Geology of the Ayr 1:250,000 Sheet Area, Queensland

002841
COMMONWEALTH OP AUSTRALIA
DEPARTMENT O F NATIONAL
B U R E A U
DEVELOPMENT
O F MINERAL RESOURCES, G E O L O G Y A N D GEOPHYSICS
R E P O R T 128
Geology of the Ayr 1:250,000 Sheet Area,
Queensland
BY
A . G . L . Paine, C. M . Gregory (Bureau of Mineral Resources)
and D . E. Clarke (Geological Survey of Queensland
Issued under the Authority of Hon. R. W. Swarlz
Minister for National Development
1970
C O M M O N W E A L T H OF A U S T R A L I A
D E P A R T M E N T
B U R E A U
O F N A T I O N A L
DEVELOPMENT
O F M I N E R A L RESOURCES, G E O L O G Y A N D
GEOPHYSICS
R E P O R T 128
Geology of the Ayr 1:250,000 Sheet Area,
Queensland
BY
A . G . L . Paine, C. M . Gregory (Bureau of Mineral Resources)
and D . E. Clarke (Geological Survey of Queensland
Issued under the Authority of Hon. R. W. Swartz
Minister for National Development
1970
COMMONWEALTH OF AUSTRALIA
DEPARTMENT OF NATIONAL DEVELOPMENT
MINISTER: T H E H O N . R . W . SWARTZ, M . B . E . , E . D . ,
M.P.
SECRETARY: L . F. BOTT, D . S . C .
B U R E A U OF M I N E R A L RESOURCES, G E O L O G Y A N D
DIRECTOR: N
GEOPHYSICS
H . FISHER
THIS REPORT WAS PREPARED FOR PUBLICATION IN THE
GEOLOGICAL BRANCH
ASSISTANT DIRECTOR: J. N . CASEY
Published by the Bureau of Mineral Resources, Geology and Geophysics
Canberra, A.C.T.
(i)
CONTENTS
Page
SUMMARY
..
iii
INTRODUCTION
..
Acknowledgments
..
P r e v i o u s and Contemporary Investigations
1
2
2
PHYSIOGRAPHY
3
EARLY PALAEOZOIC
5
Metamorphics
Ravenswood Granodiorite
..
U P P E R DEVONIAN(?)
Calcareous Hornfels
..
5
13
..
13
..
13
U P P E R CARBONIFEROUS
Ellenvale Beds
Acid Volcanics
14
..
..
„.
14
14
U P P E R C A R B O N I F E R O U S to L O W E R P E R M I A N
Intermediate to Basic Plutonic Rocks
Acid Plutonic Rocks „,
Acid Volcanic Plug
Intermediate to A c i d Volcanics
15
..
16
23
28
28
P E R M I A N T O MESOZOIC . .
Volcanics
Granites, e t c .
Dykes
CAINOZOIC
30
..
..
..
..
..
..
39
QUATERNARY
..
41
STRUCTURE
42
GEOLOGICAL HISTORY
..
ECONOMIC G E O L O G Y
REFERENCES
30
30
34
43
..
..
..
44
47
(ii)
APPENDICES
Page
Appendix 1. Spectre-chemical analyses
49
Appendix 2. M i n e r a l o g i c a l composition of three samples of heavy m i n e r a l
sand from beaches near Bowen
50
Appendix 3. M i n e r a l o g i c a l c o m p a r i s o n
of ilmenite
sand and gabbro f r o m
near Abbot Point
53
Appendix 4. W a t e r bores d r i l l e d to bedrock in the Burdekin R i v e r Delta
Appendix 5.
Isotopic age determinations
55
.58
TABLES
Table 1.
P a l a e o z o i c stratigraphy and igneous activity
..
6
Table 2.
Cainozoic stratigraphy
..
38
PLATE
A y r Geological Sheet, scale 1:250,000
A t back of
Report
FIGURES
Figure 1.
L o c a l i t y map
F i g u r e 2.
Physiography (block d i a g r a m )
F i g u r e 3,
Andalusite quartzite near Clevedon railway siding.
Photomicrograph
..
4
..
..
ll
Figure 4.
Contortion and truncation of banding in gabbro at Abbot Point
19
F i g u r e 5.
I r r e g u l a r i t i e s in the banding in gabbro at Abbot Point
19
F i g u r e 6.
Euhedral plagioclase phenocrysts in gabbro at Abbot Point
20
F i g u r e 7.
Gabbro pegmatite segregations in gabbro at Abbot Point
20
F i g u r e 8.
Planar banding in anorthite gabbro near Mount Luce
21
F i g u r e 9.
Air-photograph of Cape Upstart peninsula
F i g u r e 10.
Dykes intruding marginal zone of Gloucester Island
leucogranite stock ( P e r m i a n or M e s o z o i c )
F i g u r e 11.
Jointing in leucogranite, Gloucester Island
F i g u r e 12.
Leucogranite intruding net-veined c o m p l e x ,
Gloucester Island
..
..
,.
31
..
33
33
..
35
..
35
F i g u r e 13.
Close-up of net-veined complex, Gloucester Island
F i g u r e 14.
P o r p h y r i t i c rhyolite dyke in adamellite ( P e r m i a n or
M e s o z o i c ) near Cape Upstart
..
..
Quaternary deltaic sediments at Lynchs Beach in the
37
F i g u r e 15.
Burdekin R i v e r Delta
..
40
..
42
F i g u r e 16.
Structure
..
F i g u r e 17.
Location of water b o r e s which reached bedrock in the
Burdekin R i v e r Delta
..
..
..
..
56
(ill)
SUMMARY
The A y r Sheet area was mapped at 1:250,000 scale in 1964 by the Bureau of Mineral
Resources and the Geological Survey of Queensland as part of a regional survey of the
T o w n s v i l l e , Hughenden, Charters T o w e r s , A y r , Bowen, and Proserpine Sheet areas.
Most of the Sheet area is c o v e r e d by alluvial, deltaic, and littoral deposits of the
coastal plain, whose most important feature is the Burdekin River Delta. Plutonic igneous
rocks are exposed over about 600 square m i l e s . The mapping of the northern half of the
Bowen Sheet area in 1965 and the isotopic ages obtained in 1966-67 have led to a better
understanding of the age and relationships of the plutonic rocks than was possible from
the A y r Sheet area alone.
The oldest rocks are roof pendants of metasediments, most of which are believed to
be Silurian or older. West of the Burdekin River the metasediments have been intruded by
granodiorite which is thought to be part of the Silurian to Lower Devonian Ravenswood
Granodiorite*, which underlies 2000 square m i l e s in the Charters T o w e r s and Townsville
Sheet areas. Acid volcanics, which are correlated with Upper Carboniferous volcanics in
the Townsville and Bowen Sheet areas, crop out in the southwest. Most of the bedrock east
of the Burdekin River is generally contiguous with similar rocks in the Bowen Sheet area
which have been dated isotopically as Upper Carboniferous and Lower Permian. Carbonifer­
ous to Permian intermediate volcanics extend southeast from Townsville into the north­
western part of the Sheet area. They are intruded by L o w e r Permian epizonal granites;
s i m i l a r granites intrude the Upper Carboniferous to Lower Permian granites and diorites
east of the Burdekin R i v e r . Dyke swarms are abundant in most of the rock units.
No metalliferous deposits have been worked in the A y r Sheet area, but nickel, copper,
and molybdenum have been detected by spectrochemical analysis of rocks collected during
the regional mapping. A regional geochemical survey of the A y r Sheet area was c a r r i e d out
by the Bureau of Mineral Resources in 1965.
*
See footnote, p. 13
F i g . 1:
Locality map.
INTRODUCTION
The Bureau of Mineral R e s o u r c e s in con junction with the Geological Survey of Queens­
land mapped the A y r 1:250,000 Sheet area f r o m July to October 1964, as part of a p r o ­
g r a m m e of regional mapping of the T o w n s v i l l e / C h a r t e r s T o w e r s / B o w e n r e g i o n (see F i g . 1 ) .
A s a result of field w o r k in the Bowen and P r o s e r p i n e Sheet a r e a s in 1965 (Paine
et a l . , in p r e p . ; Clarke et al., 1968, unpubl., and in p r e p . ) , some of the r o c k units initially
e r e c t e d (Paine e t a l . , 1966, unpubl.) w e r e reappraised. The plutonic rock units w e r e further
r e c o n s i d e r e d in 1967, partly because isotopic age determinations became available. In
brief, it was decided not to use the name Urannah Complex in the A y r Sheet area, to con­
fine the name Ravenswood Granodiorite to r o c k s w e s t of the Burdekin R i v e r , and to
group the m o r e acid plutonic rocks into two main c a t e g o r i e s , 'Upper Carboniferous to
L o w e r P e r m i a n ' ( C - P g ) and ' P e r m i a n to Mesozoic* ( P - M g ) .
o
o
o
The A y r Sheet area is situated between latitudes 19 S and 20 S and longitudes 147 E
and 148 E. The area i s s e r v e d by two towns, A y r (population 8010)* and Home Hill (pop­
ulation 3217)* on the northern and southern sides of the Burdekin R i v e r r e s p e c t i v e l y , and
the s m a l l e r centres of Giru, Brandon, C l a r e , and M i l l a r o o . The North Coast Railway and
the Bruce Highway link A y r and Home Hill with other centres of population along the
coast. A sealed road follows the western side of the Burdekin R i v e r , and joins Dalbeg
in the Bowen Sheet area with A y r . In the A y r , Home Hill, and Giru d i s t r i c t s many m i l e s
of sealed roads s e r v e the sugar-cane f a r m s . G r a v e l roads connect the cattle stations
with the sealed r o a d s .
A c c e s s is good except for a few rugged a r e a s and some coastal outcrops. The survey
used f o u r - w h e e l - d r i v e v e h i c l e s as the main f o r m of transport, and a launch to v i s i t other­
w i s e inaccessible coastal outcrops and islands. A light aircraft was used briefly towards
the end of the survey for a final appraisal of the area, and for spotting outcrops in the
Burdekin R i v e r .
The c l i m a t e i s mild and usually dry in winter, and hot and wet in s u m m e r . The annual
rainfall, which i s about 40 inches at A y r , d e c r e a s e s away f r o m the coast. T h r e e - q u a r t e r s
of the rain usually falls between November and A p r i l , and heavy falls s o m e t i m e s c l o s e
a l l roads for short p e r i o d s .
Sugar production is the main industry around A y r , Home Hill, and Giru. In the A y r
and Home Hill districts water for irrigation is obtained f r o m the alluvium of the Burdekin
Delta. Cane f a r m s have also been established farther upstream, w h e r e v e r suitable land
and water for i r r i g a t i o n a r e available. Around Giru the rainfall is just sufficient to g r o w
cane without i r r i g a t i o n . Beef-cattle raising is the main industry in the r e s t of the a r e a .
Minor p r i m a r y industries include s m a l l - s c a l e fruit and vegetable growing, some grain
and fodder production, and quarrying of 'earth lime* and rock a g g r e g a t e . T h e r e is no
p o r t at A y r , and all products are transported to markets or ports by r a i l o r road.
Air-photographs at 1:85,000 scale, flown by Adastra in 1961, c o v e r all the Sheet area,
except for Holbourne Island and N a r e s Rock.
The following base maps c o v e r the Sheet a r e a :
4 m i l e s to an
A y r , E55-15
Australian A r m y 1943
inch
1:1,000,000
1:100,000
*
Townsville,
3219
Bowling Green
Bay, 8359
A y r , 8358
ICAO
1958
RASC
1967
1961 Commonwealth Census
1
F e w contours
Contour interval
100 ft
11
Cape Upstart,
8458
"
"
Abbot Point,
8558
"
1967
"
"
11
Cadastral maps at 4 m i l e s to 1 inch and 2 m i l e s to 1 inch a r e published by the Depart­
ment of Public Lands, Brisbane.
The p l a n i m e t r i c base for the geological map which accompanies this Report was
c o m p i l e d f r o m 1:75,000 topographic compilations supplied by the Royal Australian Survey
Corps.
In 1965, A . W . Webb of the Bureau of Mineral R e s o u r c e s c o l l e c t e d samples for isotopic
dating f r o m the A y r Sheet a r e a , mostly from the plutonic r o c k s , and all dates cited in this
R e p o r t a r e the result of his w o r k .
Acknowledgments
One hundred and sixty three thin sections w e r e described briefly by R . Townend and
A . R . T u r n e r of the Australian Mineral Development L a b o r a t o r i e s , and by W . R . Morgan
of the Bureau of M i n e r a l R e s o u r c e s . W . B . Dallwitz m a t e r i a l l y assisted in the examination
of s o m e of the thin sections.
We a r e indebted to the Queensland Irrigation and Water Supply C o m m i s s i o n for the
data in Appendix N o . 4 on w a t e r b o r e s in the Burdekin R i v e r Delta. M r W . Hickmott,
of Guthalungra, f r e e l y shared with us his knowledge of mineral occurrences and interesting
g e o l o g i c a l features in the Home H i l l / B o w e n d i s t r i c t , and his assistance is gratefully
acknowledged.
P r e v i o u s and Contemporary Investigations
In 1950 the Land R e s e a r c h and Regional Survey Division of the Commonwealth Scientific
and Industrial R e s e a r c h Organisation c a r r i e d out a land-use survey of the T o w n s v i l l e Bowen r e g i o n , including the A y r Sheet a r e a . T h e i r r e p o r t (Christian et al., 1953) contains
a b r i e f account by D . M . T r a v e s ( B M R ) of the geology of the r e g i o n based on a fuller r e p o r t
by T r a v e s (1951, unpubl.).
A p a r t f r o m T r a v e s ' survey, no regional g e o l o g i c a l w o r k had been c a r r i e d out before
the present survey by the Bureau of Mineral R e s o u r c e s and Geological Survey of Queens­
land. M i n e r a l o c c u r r e n c e s have been investigated f r o m time to t i m e . They include the
graphite near Cape Upstart (Dunstan, 1921); the phosphate deposit at Holbourne Island
(Saint-Smith, 1919; R e i d , 1944; Young, 1944, unpubl.); the Cainozoic 'earthlime* deposits
near H o m e Hill (Connah, 1958); and the v e r m i c u l i t e and asbestos occurrences near Home
Hill (Carruthers, 1954).
In r e c e n t y e a r s , much attention has been devoted to the study of the groundwater
potential of the Burdekin R i v e r Delta (Irrigation and Water Supply Commission, Queensland,
1964, unpubl.). Watkins & Wolff (1960, unpubl.) reported on the geology of the delta and its
neighbourhood. M o r e recently, at the request of the Queensland Irrigation and Water
Supply C o m m i s s i o n , the Bureau of Mineral R e s o u r c e s c a r r i e d out extensive geophysical
investigations to determine the structure and distribution of the sediments in the delta,
the m o v e m e n t of groundwater, and the behaviour of the interface between fresh water
and salt w a t e r (Andrew & Wainwright, 1964, unpubl.; Andrew e t a l . , 1965; Wiebenga
et a l . , 1966, unpubl.).
In 1964, three g e o l o g i s t s , J . M . Coleman, S.M, Gagliano, and W . G . Smith f r o m Louisiana
State U n i v e r s i t y , USA, surveyed the Quaternary sediments of the coastal plain between
Cape Cleveland and Cape Upstart to obtain information on deltaic sedimentation, with
special r e f e r e n c e to petroleum exploration.
2
In 1963 the Bureau of Mineral Resources c a r r i e d out a reconnaissance helicopter
gravity survey (Darby, 1966, unpubl.) of the northern part of the Bowen Basin and the
A y r Sheet a r e a .
In 1965 the Bureau of Mineral Resources c a r r i e d out a regional geochemical survey
of the Sheet area (Marshall, 1967, unpubl.). Samples w e r e collected from stream sediments,
s o i l s , and r o c k s .
PHYSIOGRAPHY
The A y r Sheet area contains five main physiographic units: coastal plain, isolated
h i l l s , a r e a s of low hills, a feature called the Plumtree 'plateau-basin', and rugged hills
( F i g . 2 ) . The mudflats, saltpans, mangrove swamps, and coastal sand dunes together form
a subunit of the coastal plain.
The coastal plain c o v e r s most of the land surface. The plain is flat to gently undulating.
The watercourses are generally steep-sided, and the Burdekin River is incised in places
down to 80 feet below its l e v e e s . Most of the plain consists of alluvial and deltaic deposits.
The coastal plain includes a few steep isolated h i l l s , most of which form prominent
landmarks,
rising abruptly from the plain.
The areas of low hills surround the Plumtree *plateau-basin', and occupy the southwest
c o r n e r of the Sheet area. The land surface ranges from open undulating country to small
a r e a s of rough hilly terrain with a local r e l i e f of up to 500 feet. There is a sharp break
between the areas of low hills and the coastal plain.
The name Plumtree 'plateau-basin' is used to describe a remnant of a southerly
directed mature drainage basin (Plumtree Creek) which has been truncated on its western,
northern, and eastern sides by the headwaters of more youthful streams which flow radially
outwards from it. The surface of this feature is a mature gently undulating erosion surface
which slopes gently southwards. The northern and eastern sides are bounded by irregular
scarps 100 to 200 feet high; the western margin, although scarp-like locally, is poorly
defined and, like the southern margin, m e r g e s with the base level of the c r e e k s which
drain the areas of low hills. The northern part of the Plumtree 'plateau-basin' is a low
plateau, but the southern half is basinal in relation to the bordering hills.
The rugged hills occur as isolated ranges which r i s e steeply to between 1500 and 3000
feet above sea l e v e l . The summit of Mount Elliot, just west of the Sheet area, is 4025
feet above sea l e v e l . Deep straight fault-controlled ravines have been eroded in the Cape
Cleveland, Saddle Mountain, and Cape Upstart ranges ( F i g . 9 ) . The Cape Cleveland and
Cape Upstart ranges are peninsulas, connected to the mainland only by sand dunes and
mud flats.
Much of the area is drained by short coastal streams that commonly m e r g e with the
tidal areas or
broaden out and lose their
identity in the plains adjacent to the coast.
The Burdekin River is by far the largest watercourse in the Sheet area, but it drains only
a r e l a t i v e l y small part of the area.
3
E5VAI5/36
F i g . 2:
Physiography (block d i a g r a m ) .
EARLY PALAEOZOIC
The P a l a e o z o i c rock units a r e summarized in Table 1.
METAMORPHICS (Pzu)
Remnants of a metamorphosed arenite-siltstone sequence which is intruded by g r a n o ­
diorite c o r r e l a t e d with the Ravenswood Granodiorite c r o p out in the southwest. The
sediments have been dynamothermally metamorphosed to the q u a r t z - a l b i t e - m u s c o v i t e chlorite subfaeies, and locally to the quartz-albite-epidote-biotite subfaciesof the g r e e n schist f a c i e s . The metamorphic r e g i m e was not a regional one in the g e n e r a l l y accepted
sense as the dynamic and thermal metamorphism was related to intrusions and fault z o n e s .
If the granodiorite which intrudes these rocks is part of the Ravenswood Granodiorite
then they a r e Silurian or o l d e r . They a r e regarded as broadly equivalent to the Cape
R i v e r Beds of the Charters T o w e r s Sheet area and to unnamed metamorphics ( P z u )
in the southeastern part of the T o w n s v i l l e Sheet a r e a .
Hornfelses, some of which a r e a l s o metamorphosed arenites and siltstones, c r o p
out near Guthalungra, where they a r e intruded by Upper Carboniferous to L o w e r P e r m i a n
granites. T h e i r age is unknown, but they could be as young as late P a l a e o z o i c .
Topography
In the southwest the l a r g e s t o c c u r r e n c e of metamorphosed sediments is an i r r e g u l a r
area of about 4 square m i l e s 5 m i l e s southwest of Mount Woodhouse. In p l a c e s the m e t a sediments f o r m a range of hills r i s i n g about 400 feet above the surrounding alluviumc o v e r e d Ravenswood Granodiorite. Similar metamorphosed sediments f o r m steep r i d g e s
a few hundred feet high 2 m i l e s w e s t of Mount Benjonney. Low outcrops occur just w e s t of
Landers C r e e k homestead, and in the bed of the Burdekin R i v e r near M i l l a r o o .
Similar rocks crop out in the hills northwest of The Cape homestead. They have been
intruded by Carboniferous to P e r m i a n granite; the contact is v e r y i r r e g u l a r and has been
simplified on the map. Metasediments also crop out to the w e s t of the Seven S i s t e r s , and
there is a s m a l l spur of andalusite quartzite to the west of the Bruce Highway, half a m i l e
southeast of Clevedon railway siding.
Lithology and Metamorphism
F i v e m i l e s southwest of Mount Woodhouse the l o w - g r a d e dynamothermally m e t a ­
morphosed sediments c o m p r i s e c o a r s e to medium-grained micaceous sandstone, w e l l
sorted subarkose, p o o r l y sorted micaceous pebbly sandstone, micaceous silty arenite,
and pebble c o n g l o m e r a t e . Oligomictic cobble c o n g l o m e r a t e , quartzite, subarkose, and
thinly bedded carbonaceous siltstone crop out 2 m i l e s northwest of Mount Benjonney. The
cobbles in the conglomerate consist of quartz porphyry, quartz-feldspar p o r p h y r y , biotite
schist, quartzite, and fine-grained amphibolite* The sediments f o r m a roof pendant on the
Ravenswood Granodiorite, and w e r e further metamorphosed by the granodiorite ( C - P g )
immediately to the east.
The sediments southwest of Mount Woodhouse also f o r m a roof pendant on the R a v e n s ­
wood Granodiorite, and have been thermally and dynamically metamorphosed. Metamorphic
grade i s higher w h e r e the roof pendant is thinner, as for example, in the headwaters of
Sandy C r e e k , w h e r e metamorphosed siltstone and q u a r t z - c h l o r i t e - s e r i c i t e - m u s c o v i t e
schist c r o p out. The metamorphosed siltstone consists of subspherical a g g r e g a t e s of
s i l t - s i z e quartz, chlorite, and muscovite surrounded by an intensely foliated groundmass
of muscovite, r a r e s e r i c i t e , and quartz grains. Similar metamorphics c r o p out in the
southeastern part of the T o w n s v i l l e Sheet a r e a .
5
T A B L E 1.
P A L A E O Z O I C S T R A T I G R A P H Y A N D IGNEOUS A C T I V I T Y
(includes some possibly Mesozoic granites)
Rock Unit
and
or Epoch
Map Symbol
Period
(P-Mg)
u
o
N
o
CO
w
o
Lithology
Topography
Leucocratic
adamellite
and granite;
granophyre,
syenite, and
rhyolite p o r ­
phyry; r a r e
intermediate
and basic
rocks
Rugged hills and mount­
ains up to 3000 ft above
sea l e v e l ; some small
hills; Holbourne Is
Relationships
Structural/Depositional
Remarks
Environment
Youngest plutonic bodies; Epizonal stocks, some of R a r e l y intruded by dykes
intrude U Carboniferous/ which may be ring
L P e r m i a n volcanics
complexes
( C - P v ) and granites
(C-Pg)
H
w
(P-Md)
(P-Mv)
Gabbro, d i o - E part of Holbourne Is
r i t e , d o l e r i t e (300 ft a s l ) ; other
small outcrops
at sea l e v e l along
coastline
Probably older than
Mainly small marginal
Permian/Mesozoic
s l i v e r s around stocks
granites ( P - M g ) , but in
( P - M g ) ; probably e a r l y
places may be
differentiates of
essentially contemporan­ ' P - M g ' magma
eous (net-veined
complexes)
Hornfelsed
siliceous
tuff or tuffaceous sedi­
ments
Unknown
Nares Rock, 20 ft high
200 ft in diameter
Unknown
Size of outcrops (except on
Holbourne Is) exaggerated
on map
(C-Pv)
<
(C-Ph)
w
w
o
(C-Pg)
•J
o
H
CO
8
W
i—i
o
«
w
(C-Pd)
Intermediate Uneven slopes and footlavas and
hills adjoining Saddle Mt
p y r o c l a s t i c s ; and Mt Elliot; steep
minor acid
narrow Cape Cleveland
volcanics
promontory
Rhyolite,
trachyte,
trachyandesite
Steep high hills with
cliffs in places;
Mt Louisa
Adamellite,
granite,
some gran­
odiorite;
minor
fine­
grained
variants
Coastal inselbergs up to
700 ft; uneven hills,
in places quite rugged;
uneven undulating
country, with some
prominent dyke r i d g e s
Diorite,
quartz
Undulating r i s e s , uneven
hills, dyke r i d g e s
diorite,
S of Home Hill;
tonalite,
inselbergs up to 900 ft
gabbro,
high; l o w - l y i n g country
norite;
S of Guthalungra; roof
minor
pendants near summit of
granodiorite, Mt Roundback
adamellite,
and granite
Intruded by P e r m i a n /
M e s o z o i c granites
( P - M g ) ; continuous with
Glossopteris-bearing
volcanics near T o w n s ­
v i l l e ; correlated with
L i z z i e Creek Volcanics
(Bowen Sheet)
Intrudes Carboniferous/
P e r m i a n granite
(C-Pg)
Intrudes Carboniferous/
P e r m i a n diorite ( C - P d )
and U Carboniferous
volcanics (Cuv);
relationship to
Carboniferous/Permian
volcanics unknown, but
latter probably younger;
small roof pendants near
The Cape homestead
Generally structureless
except at Cape Cleveland,
where dip is consistently
SE; abundant c o a r s e
Maximum thickness 4000ft
at Cape Cleveland; e l s e ­
where thickness unknown;
strongly epidotized i n p l a -
pyroclastics indicate
local derivation
ces
Plug with some extrusive
phases; v e r t i c a l flow
banding
Sheared or foliated in
places
A g e postulated mainly by
analogy with contiguous
granite in Bowen Sheet
A g e postulated mainly by
Intruded by
Sheared or foliated in
Carboniferous/Permian
places; p r i m a r y layering analogy with s i m i l a r rocks
in Bowen Sheet; may in­
granite ( C - P g ) and by
in places
clude undetected roof pen­
P e r m i a n / M e s o z o i c granite
dants of Ravenswood Gran­
( P - M g ) ; small roof
odiorite S of Home Hill
pendants near Guthalungra
(Cuv)
CO
p
O
w
PH
S
CL
§
Flow-banded Rugged range (Mt
D a l r y m p l e ) , small hill
rhyolite,
m a s s i v e w e l ­ (Mt Woodhouse)
ded tuff;
minor andesite and
andesite
tuff
Fault-controlled; Mt
Intruded by
Dalrymple is a
Carboniferous/Permian
downfaulted block
granite ( C - P g ) ;
c o r r e l a t e d with Ellenvale
Beds (Townsville Sheet)
and Bulgonunna Volcanics
(Bowen Sheet)
Flow-bandded rhyolite,
rhyolite
breccia,
andesite
Prominent hill (Horse
Camp H i l l ) above 700 ft
high
Not seen in A y r Sheet
area; continues into
Townsville Sheet w h e r e ,
in type area, it is late
M to U Carboniferous
Fault-controlled
Charlies Hill, 1200 ft
Isolated inlier in
Burdekin R Delta;
strongly r e s e m b l e s
conglomerate of U
Devonian Dotswood
Formation (Townsville
C r o s s - b e d s indicate
Horse Camp Hill is SE
limit
of Ellenvale Beds
which thereafter
become
'Cuv' (see text)
P
&
^ PQ
Ellenvale
Beds
(Ce)
(Pzj)
rr*
PG
5f^
w
Pi
3£
P.
O
z>w >
Q
Strongly
hornfelsed
calcareous
cobble and
pebble con­
glomerate;
some interbeds of c a l ­
careous
quartzite
by 700 ft
Sheet)
that beds have been
overturned
Phenoc lasts
of quartz,
marble, and gneissic d i o ­
rite
<
O
>
crj O W
P H Q
(S-Da)
Biotite
granite,
leucocratic
adamellite
(S-Dr)
Deeply
weathered
hornblendebiotite
°
w
CO
I
(Pzu)
Steep hills, low r i s e s
Late acid phase of
Not known in A y r Sheet
area; in Townsville Sheet batholith
intrudes granodiorite
phase (S-Dr) and is
overlain nonconformably
by M Devonian sediments
E limit of l a r g e batholith
L o w - l y i n g , p o o r l y expos­ Intrudes e a r l y P a l a e o z o i c
ed
metamorphics (Pzu) at
Barrata C r ; overlain
unconformably by U
granodiorite;
Carboniferous volcanics
minor adam­
(Cuv)
e l l i t e , quartz
diorite, diorite,
and alkali
granite
Schist,
phyllite,
quartzite,
hornfels;
H i l l s , small steep
r i d g e s , low r i s e s
Intruded by Ravenswood
Granodiorite and
younger plutonic units
Photo-interpreted extens­
ions from T o w n s v i l l e and
Bowen Sheets
which caused widespread
'regional/contact*
meta­
morphism
Roof pendants,
dynamothermally
Probably at least partly
equivalent to Cape R i v e r
metamorphosed sediments Beds of C h a r t e r s T o w e r s
and minor igneous r o c k s ; Sheet; outcrops near Guth-
S
weakly
metamorphism and f o l d -
alungra
N
metamorphosed
ing related to intrusions
homestead
subarkose,
and faults rather than
young as L P e r m i a n
conglomerate,
and carbon­
to orogeny; bedding and
cleavage attitude appear
aceous s i l t ­
stone
to lack regional control
« o
W w
3
<
ft
and
The
may
Cape
be
as
The metamorphosed sediments near the margins of the roof pendant include various
a s s e m b l a g e s of the q u a r t z - a l b i t e - m u s c o v i t e - c h l o r i t e subfacies of the greenschist f a c i e s .
They a r e chiefly p o o r l y foliated c h l o r i t e - m u s c o v i t e - s e r i c i t e - q u a r t z schist. Only at the
thinner southeastern end of the roof pendant is the schistosity sufficiently w e l l developed
to be c l e a r l y v i s i b l e in hand s p e c i m e n . R e c r y s t a l l i z a t i o n has generally been confined to
the m a t r i x of the sediments, e s p e c i a l l y towards the northwest, w h e r e thermal effects a r e
weakest.
Half a m i l e w e s t of Landers C r e e k homestead strongly foliated q u a r t z - c h l o r i t e m u s c o v i t e - s e r i c i t e schist, q u a r t z - c h l o r i t e - s e r i c i t e - m u s c o v i t e schist, and black schistose
a r g i l l i t e f o r m an isolated r i s e above the alluvium bordering Landers C r e e k . The metasediments appear to l i e in a shatter zone associated with strong faulting. The spotted
s e r i c i t e schist and metamorphosed pebbly arenites exposed in the bed of the Burdekin
R i v e r a l i t t l e to the east a l s o l i e in this zone.
The metamorphics northwest of The Cape homestead have been intimately intruded
and hornfelsed by granite, tonalite, and gabbro ( C - P g , C - P d ) . They include a v a r i e t y of
hornfelses, some of which a r e m o d e r a t e l y high in g r a d e : biotite-alkali feldspar-quartz
hornfels; epidote-hornblende-andesine-quartz hornfels; garnet-biotite-albite-potash f e l d ­
spar-quartz
hornfels; g a r n e t - b i o t i t e - m i c r o c l i n e - p l a g i o c l a s e - q u a r t z hornfels; biotiteq u a r t z - s e r i c i t e hornfels; biotite-andalusite-quartz-sericite hornfels; andalusite-biotitem u s c o v i t e - o l i g o c l a s e - q u a r t z hornfels; andalusite-biotite-sericite-quartz hornfels;and f e r ­
ruginous b i o t i t e - c o r d i e r i t e - c h i a s t o l i t e - q u a r t z schist.
The biotite-alkali feldspar-quartz hornfels, epidote-hornblende-andesine-quartz horn­
f e l s , garnet-biotite-albite-potash feldspar-quartz hornfels, and g a r n e t - b i o t i t e - m i c r o c l i n e p l a g i o c l a s e - q u a r t z hornfels a r e strongly foliated, and in places they a r e c o a r s e - g r a i n e d
and gneissic in texture. They c r o p out on the southern slopes of a southwesterly trending
r i d g e , 1 m i l e west-southwest of The Cape homestead. They r e s e m b l e granodiorite, and
in p l a c e s the foliation is intricately folded. R a r e spherical aggregates of epidote, quartz
and hornblende, up to 3 c m in d i a m e t e r , which developed later than the foliation, occur
in the foliated r o c k s . The hornfelses a r e all c l o s e to a contact with garnetiferous ton­
a l i t e , which i s also foliated in p l a c e s . The contacts a r e generally sharp, o r gradational
o v e r a few inches. The biotite-alkali feldspar-quartz hornfels may be a metamorphosed
rhyolite o r m i c r o g r a n i t e with r e l i c t phenocrysts of quartz, sodic p l a g i o c l a s e , and biotite.
The epidote-hornblende-andesine-quartz hornfels is possibly a metamorphosed calcareous
and aluminous sandstone; some of the andesine and hornblende have been p a r t l y replaced
by epidote. The garnet-biotite-albite-potash feldspar-quartz hornfels contains a few
p a r t l y r e c r y s t a l l i z e d m e g a c r y s t s of albite, which suggests that the original rock was
an acid porphyry. The r a r e c o l o u r l e s s garnet (probably almandine) has been partly replaced
by biotite and c h l o r i t e , and knots of biotite flakes may also represent a l t e r e d garnet.
The g a r n e t - b i o t i t e - m i c r o c l i n e - p l a g i o c l a s e - q u a r t z hornfels contains garnet porphyroblasts
in the c o a r s e r (0.5 m m ) l a y e r s . The main metamorphism of the hornfelses was probably
caused by the gabbro ( C - P d ) and the later r e t r o g r a d e metamorphism of p l a g i o c l a s e and
hornblende to epidote was probably caused by the tonalite ( C - P g ) .
Dark g r e y b i o t i t e - q u a r t z - s e r i c i t e hornfels f o r m s the southwestern end of a spur l i
m i l e s west-southwest of The Cape homestead. The banding presumably r e p r e s e n t s bedding.
In places the rock is c l e a v e d by s e r i c i t i c parting planes. The hornfels is composed of
amoeboid quartz grains (30%), a g g r e g a t e s of fine s e r i c i t e flakes pseudomorphing feldspar
o r andalusite ( ? ) , and randomly oriented chloritized biotite.
The b i o t i t e - a n d a l u s i t e - q u a r t z - s e r i c i t e hornfels, andalusite-biotite-muscovite-olig o c l a s e - q u a r t z hornfels, and andalusite-biotite-sericite-quartz hornfels c r o p out as thin
r o o f pendants and l a r g e xenoliths in granite in the centre of the range which extends
for s e v e r a l m i l e s w e s t of The Cape homestead. The biotite-andalusite-quartz-sericite
10
hornfels contains tabular porphyroblasts of partly s e r i c i t i z e d andalusite. It is probably
a m o r e strongly metamorphosed version of the biotite-quartz-sericite hornfels. The
andalusite-biotite-muscovite-oligoclase-quartz hornfels was probably a tuff. It contains
50 to 60 percent inequigranular (0.03-4.0 mm) anhedral crystals of r e c r y s t a l l i z e d quartz
and tabular slightly r e c r y s t a l l i z e d twinned oligoclase set in a matrix of fine biotite and
muscovite, with some granoblastic quartz and feldspar; groups of partly s e r i c i t i z e d c r y s ­
tals of andalusite are present in places. Both rocks are dark blue-grey, dense, and flinty.
A fragment of ferruginous biotite-cordierite-chiastolite-quartz hornfels was found
in the valley between this range and the mountains to the north. It is a dark brownish
black fine-grained rock with a resinous lustre, and contains numerous small euhedral
pinkish brown crystals of chiastolite. T w o kinds of porphyroblasts are present: crystals
of chiastolite with their long axes in the plane of schistosity, and xenoblastic crystals of
c o r d i e r i t e ( ? ) containing many inclusions of iron oxide. Parts of the c o r d i e r i t e crystals
are in optical continuity with neighbouring crystals of altered chiastolite which they appear
partly to r e p l a c e . The xenoblastic c o r d i e r i t e is unusual in that it is uniaxial or biaxial
negative with a small optic axial angle. The fine-grained matrix consists of ferruginous
biotite, iron oxide dust, and quartz.
A piece of blastomylonite was found on the southern slopes of the range west of The
Cape homestead. The matrix has a g r a i n s i z e o f 0.01 to 0.03 mm, and consists of amoeboid
grains of plagioclase (probably labradorite), prismatic to granular pale brownish green
amphibole, and granules of iron oxide. The poikiloblastic porphyroblasts of almost colour­
l e s s clinopyroxene are about 0.3 mm in diameter. T h e r e are a few residual megacrysts
of clinopyroxene and orthopyroxene. This rock is probably a gabbro which has been
mylonitized and subsequently thermally metamorphosed; the c r i s s - c r o s s i n g veinlets and
porphyroblasts of clinopyroxene w e r e probably formed at the same time.
Biotite-quartz-sericite hornfelses s i m i l a r to some of the hornfelses west of The
Cape homestead form undulating r i s e s immediately west of the Seven Sisters. They have
been intruded by tonalite ( C - P d ) and by the granite of the Seven Sisters ( C - P g ) . They are
fine-grained brownish red and brownish green impure arenites. Cleavage has been develop­
ed in the fine-grained interbeds.
F i g . 3:
Andalusite quartzite (Pzu), half a mile southeast of Clevedon railway siding.
Xenoblastic andalusite is partly r i m m e d by aggregates of rutile and iron
oxide. White mica ( s e r i c i t e or pyrophyllite) occurs between subhedral quartz
grains. Plane polarized light, x45. (BMR TS15715).
11
A small spur of andalusite quartzite ( F i g . 3) abuts against the northeastern foot of
the Saddle Mountain granite ( P - M g ) , half a m i l e southeast of Clevedon railway siding.
Xenoblastic grains of andalusite form up to 20 percent of the rock; most of them have an
alteration r i m of s e r i c i t e or pyrophyllite, and in places the mica has completely replaced
the andalusite. The quartzite is even-grained: individual quartz grains range from 0.05 to
0.1 m m , and the largest andalusite c r y s t a l s measure 0.4 by 0.2 mm. The rock is rich
in aggregates of rutile and opaque minerals which do not seem to be detrital.
Structure and Thickness
In the west, the sediments are w e l l bedded, and southwest of Mount Woodhouse they
dip at moderate to steep angles to the north-northeast, except for r e v e r s a l s near the
Woodhouse Fault. The p r e s e r v e d thickness of the sediments is estimated at 6000 feet.
Graded bedding is apparent in thin section, and r a r e cross-bedding was observed in
outcrop. The sediments of the roof pendant southwest of Mount Woodhouse have been faulted
in two principal directions. The Woodhouse Fault trends southeast, and is marked by a
wide zone of silicified sandstone and breccia, which has been displaced by later dextral
wrench faults. Many s m a l l e r faults are indicated by areas of intense quartz veining.
The roof pendant northwest of Mount Benjonney is c o m p l e x l y faulted, and appears to
be a resistant remnant p r e s e r v e d by the hornfelsing associated with the granodiorite
( C - P g ) immediately to the east.
Foliation, c l e a v a g e , and r e l i c t beddingare v i s i b l e indifferent places in the hornfelses
w e s t of The Cape homestead. The cleavage and bedding strike east-southeast to southeast.
Near the Seven Sisters, where the cleavage and bedding probably coincide, the strike is
roughly the same as in the hornfelses west of The Cape homestead.
Age and Relationships
The metasediments southwest of Mount Woodhouse are intruded by poorly exposed
granodiorite which is correlated with the Silurian to L o w e r Devonian Ravenswood
Granodiorite. The contacts are both faulted and intrusive; the granodiorite, masked by
alluvium, c r o p s out in gullies along the southern boundary of the metasediments. The
metasediments are also intruded by rhyolite, quartz porphyry, f e l s i t e , and feldspar
porphyry dykes. The metasediments are probably e a r l y P a l a e o z o i c and are tentatively
c o r r e l a t e d with the Cape R i v e r Beds which commonly form the country rock around the
Ravenswood Granodiorite i-n the Charters T o w e r s Sheet area (Wyatt el al., 1967, unpubl.,
and 1970b.). However, it is possible that the cobbles in the conglomerates w e r e derived
from the Cape R i v e r Beds or their equivalents, and that the granodiorite is late P a l a e o z o i c .
The age of the hornfelses in the Guthalungra/Cape homestead district is uncertain.
They are intruded by gabbro and granite, which are probably Upper Carboniferous or
L o w e r P e r m i a n , and a r e unlikely to be younger than Carboniferous.
Mineralization
A few small costeans have been bulldozed in the hornfelses west of the Seven Sisters.
It is not known whether they w e r e made in the search for minerals or for road-making
m a t e r i a l s . Early this century a small shaft was sunk in graphitic hornfels 2 j m i l e s west
of The Cape homestead.
12
R A V E N S W O O D G R A N O D I O R I T E (S-Dr and S-Da)
The p o o r l y exposed granodiorite in the southwestern corner of the Sheet area i s
tentatively r e g a r d e d as part of the Ravenswood Granodiorite, a l a r g e and complex batholith
which is exposed o v e r about 2000 square m i l e s in the Charters T o w e r s and Townsville
Sheet a r e a s . Isotopic age determinations indicate a Silurian age for the batholith, but it
may range into the e a r l y Devonian*.
T w o main phases have been recognized in the Charters T o w e r s and T o w n s v i l l e Sheet
a r e a s : an e a r l i e r granodioritic phase ( S - D r ) , and a later m o r e leucocratic phase ( S - D a ) .
In the A y r Sheet area, the granodioritic phase consists chiefly of hornblende-biotite
g r a n o d i o r i t e , adamellite, quartz d i o r i t e , and minor alkali granite. The r o c k s a r e deeply
weathered and eroded, and l a r g e l y c o v e r e d by s o i l . T w o small a r e a s of the later m o r e
leucocratic phase have been photo-interpreted f r o m adjoining Sheet a r e a s : the outcrop
south of H o r s e Camp Hill f o r m s a steep east-northeasterly r i d g e and the outcrop south
of Mount Benjonney f o r m s low hills and r i s e s .
U P P E R D E V O N I A N (?)
CALCAREOUS HORNFELS (Pzj)
The calcareous hornfelses at Charlies Hill, about 4 m i l e s southeast of Home H i l l ,
may be Upper Devonian.
The hill is elongated northeast and is about 1200 feet long, 300 feet w i d e , and 70
feet high. It consists of dark g r e y strongly hornfelsed calcareous cobble and pebble c o n ­
g l o m e r a t e with interbeds of g r e y cross-bedded calcareous quartzite. Calcareous s e d i ­
ments of this type a r e unknown e l s e w h e r e in the Sheet a r e a .
o
The metasediments dip at about 20 to the southeast, and the cross-bedding in the
quartzite indicates that they are overturned. The conglomerate contains phenoclasts
of white quartz, m a r b l e , and foliated to gneissic d i o r i t e to granodiorite. The conglomerate
is a tremolite-wollastonite-diopside-garnet-quartz hornfels, in which some of the minerals
show a zonal arrangement around the phenoclasts. The interbeds consist of fine-grained
sheared actinolite quartzite. A l l the phenoclasts in the conglomerate a r e ellipsoidal
and l i e with their long axes in the plane of the bedding. The structure suggests that the
r o c k s w e r e c o m p r e s s e d , and perhaps also sheared, during folding. In p l a c e s , the con­
g l o m e r a t e has been intruded by post-tectonic veins of medium-grained leucocratic d i o r i t e
up to 6 inches w i d e .
The age of the hornfelses is unknown. The conglomerate c l o s e l y r e s e m b l e s the distinct­
i v e 'Deadmans Gully conglomerate* at the base of the Upper Devonian Dotswood Formation
in the Reid R i v e r district in the Townsville Sheet area (Wyatt et al., 1970a).
*
Further isotopic age determinations have become available since the map which a c ­
companies this Report was printed. A s a result of detailed mapping of the Ravenswood 1m i l e Sheet area (Charters T o w e r s 1:250,000 Sheet a r e a ) in 1966, the Ravenswood G r a n o ­
d i o r i t e has been subdivided into separate phases and has been renamed the Ravenswood
Granodiorite Complex (Clarke, in p r e p . ) . Rb/Sr whole r o c k dating has shown ( A . W . Webb,
p e r s . c o m m . ) that most phases of the complex w e r e intruded about 450 m i l l i o n y e a r s
ago (Middle Ordovician, Harland et al., 1964), and the r e s t about 400 m i l l i o n y e a r s ago
(Silurian-Devonian boundary).
13
U P P E R CARBONIFEROUS
E L L E N V A L E BEDS ( C e )
H o r s e Camp Hill is bisected by the boundary between the A y r and T o w n s v i l l e Sheet
a r e a s . It consists of g r e y flow-banded rhyolite, rhyolite breccia, andesite, and porphyritic
r h y o l i t e with phenocrysts of feldspar or rounded quartz.
T h e s e v o l c a n i c s w e r e mapped with the Ellenvale Beds in the T o w n s v i l l e Sheet area,
w h e r e they a r e assigned to the late Middle o r Upper Carboniferous in the type area in the
v a l l e y of the Reid R i v e r ( W y a t t e t a l . , 1970a).The evidence for this age i s : ( i ) the presence
of fragments of cf. Rhacopteris sp. and indeterminate equisetalean stems ( M c K e l l a r ,
1963, unpubl.) in the interbedded sediments, (ii) the stratigraphic position of the Ellenvale
Beds above Tournaisian strata, and (iii) the absence of G l o s s o p t e r i s .
A C I D V O L C A N I C S (Cuv)
A c i d v o l c a n i c s and minor intermediate volcanics f o r m Mount Dalrymple and a number
of s m a l l e r hills and r i s e s in the southwest. The volcanics c o m p r i s e rhyolite and rhyolite
p y r o c l a s t i c s (commonly welded) with subordinate andesite. They a r e probably equivalent
to the Ellenvale Beds in the T o w n s v i l l e Sheet area and the Bulgonunna Volcanics in the
Bowen Sheet a r e a . Malone et al. (1966) r e g a r d e d the Bulgonunna Volcanics as Upper
Carboniferous because they r e s t unconformably on the L o w e r Carboniferous Drummond
Group, and because they a r e unconformably o v e r l a i n by the L o w e r P e r m i a n L i z z i e C r e e k
V o l c a n i c s . The volcanics crop out in isolated fault blocks. No sedimentary interbeds have
been found in them.
Topography
T h e s e v o l c a n i c s f o r m most of the steep rugged range culminating in Mount Dalrymple
(1900 ft above sea l e v e l ) . They also f o r m Mount Woodhouse, which r i s e s only a few hundred
feet above the alluvial plain. The s m a l l occurrences in the southwest have insignificant
topographic expression.
Lithology
The fine-grained rhyolite and welded tuff on the southwestern flank of Mount Dalrymple
a r e highly brecciated by a strong southeast-trending fault. The welded tuffs a r e composed
of feldspar and quartz c r y s t a l s and r o c k fragments set in a devitrified felsitic matrix
of s e r i c i t i z e d and saussuritized feldspar and quartz. The rock fragments a r e of three
main t y p e s : a l t e r e d glassy fragments which have been devitrified and partly or wholly
converted to s e r i c i t e and quartz, quartz-rich fragments, and welded (?) tuff. The volcanics
a r e intruded by dykes of r e d - b r o w n feldspar-hornblende porphyry.
At the eastern end of the Mount Dalrymple range, near the headwaters of Deep C r e e k ,
dense fine-grained light g r e y r h y o l i t e and r h y o l i t e - b r e c c i a predominate. Blue-black
dacite w e l d e d tuff also o c c u r s . The volcanics a r e strongly jointed, and locally appear to
have been thermally metamorphosed.
White siliceous strongly sheared v i t r i c tuff(?) and spherulitic rhyolite crop out 2
m i l e s w e s t of the junction of Deep C r e e k and the Burdekin R i v e r . The volcanics contain
abundant p y r i t e , and l o c a l l y r e s e m b l e p y r i t i c quartzite. The strong shearing i s related
to the southeasterly fault,* and the p y r i t e may have been introduced hydrothermally from
the m i c r o g r a n i t e ( C - P g ) north of Deep C r e e k . White p y r i t i c hornfelsed rhyolite also occurs
next to the s m a l l e r body of m i c r o g r a n i t e ( C - P g ) along Deep C r e e k .
The s m a l l o c c u r r e n c e s of brecciated intermediate volcanics in the Burdekin R i v e r , and
the b r e c c i a t e d volcanic breccia in Landers C r e e k , a r e small blocks caught up in a strong
shear zone along the southwestern side of Mount D a l r y m p l e .
14
The low hills east of the Burdekin R i v e r , on the southern edge of the Sheet area,
are s p a r s e l y c o v e r e d with rubble of acid volcanics and siliceous r o c k r e s e m b l i n g quartzite.
The acid v o l c a n i c s a r e p o o r l y exposed; exposures a r e much better just within the Bowen
Sheet a r e a . They a r e pale green, pink, and white; s o m e of the rocks contain small
phenocrysts of quartz and feldspar in a flow-banded or m a s s i v e groundmass. The flow
banding i s steep and generally contorted. The siliceous rock, which consists of angular
quartz grains with strongly oriented threads of s e r i c i t e , may be older than the v o l c a n i c s .
Andesite b r e c c i a and tuff, rhyolite tuff, and subordinate rhyolite and andesite p r e ­
dominate at Mount Woodhouse; some of the tuff is partly w e l d e d . Strongly banded rhyolite
crops out c l o s e to the Woodhouse Fault, 5 m i l e s southwest of Mount Woodhouse.
Structure and Relationships
The v o l c a n i c s at Mount Dalrymple f o r m a downfaulted block in the Ravenswood Gran­
o d i o r i t e . They a r e probably mainly extrusive and partly intrusive. Along the Woodhouse
Fault, the acid volcanics are strongly sheared, brecciated, and r e c r y s t a l l i z e d , and in
places they a r e also p y r i t i c .
The granite aplite and alkali microgranite ( C - P g ) north of Deep C r e e k intrude the
v o l c a n i c s , but the contacts with the granophyric alkali granite ( C - P g ) north of Landers
C r e e k homestead a r e obscured by poor exposure and strong faulting.
The tuffaceous volcanics at Mount Woodhouse unconformably o v e r l i e the Ravenswood
Granodiorite. The small outcrops south-southwest of Mount Woodhouse are strongly
brecciated along the Woodhouse Fault; the three small a r e a s of volcanics near the southern
edge of the Sheet area have been s e v e r e l y brecciated in the east-southeasterly shear zone
along the southwestern flank of Mount D a l r y m p l e .
Age
The p r e c i s e age of the volcanics i s uncertain. They a r e younger than the Ravenswood
Granodiorite, and a r e intruded, particularly in the Leichhardt Range in the Bowen Sheet
area, by Upper Carboniferous or L o w e r P e r m i a n granites.
U P P E R CARBONIFEROUS T O LOWER PERMIAN
Most of the plutonic rocks in the A y r Sheet area a r e thought to have been emplaced in
the Upper Carboniferous or L o w e r P e r m i a n . An arbitrary twofold subdivision has been
used on the map: (1) the basic to intermediate plutonic r o c k s ( C - P d ) such as gabbro,
norite, d i o r i t e , quartz diorite, and granodiorite; and (2) the m o r e acid rocks ( C - P g ) such
as adamellite, granite, and minor granodiorite and tonalite. In places, the intrusions have
been assigned to one or other group mainly on the basis of photo-interpretation. The contacts
are p o o r l y exposed, but the m o r e acid rocks are g e n e r a l l y younger.
Paine et al. (1966, unpubl.) included the granodiorite and diorite between Arkendeith
and Beaks Mountain with the Ravenswood Granodiorite ( S i l u r i a n - L o w e r Devonian), but
recent isotopic ages and mapping in the Bowen Sheet area suggest that they a r e m o r e likely
to be the same age as s i m i l a r rocks in the eastern half of the Bowen Sheet a r e a . In
1966 the Urannah Complex in the southern half of the Bowen Sheet area (Malone et a l . ,
1966) w a s extended into the A y r Sheet area, but the name is no longer used in the northern
part of the Bowen Sheet area or in the A y r Sheet area. The plutonic r o c k s in the eastern
half of the A y r Sheet area, which w e r e f o r m e r l y mapped as part of the Urannah Complex,
a r e now incorporated in the two Upper Carboniferous to L o w e r P e r m i a n groups, and
most of the remaining acid plutonic rocks in the Sheet area a r e also included in one of
these groups ( C - P g ) .
15
I N T E R M E D I A T E T O BASIC P L U T O N I C ROCKS ( C - P d )
Topography
The area between Arkendeith and Beaks Mountain includes rough hilly country with a
r e l i e f of up to 300 feet; a r e a s of p a r a l l e l dyke r i d g e s with a r e l i e f of about 100 feet; and
gently undulating country. The dyke r i d g e s are c l e a r l y v i s i b l e on the air-photographs,
but most of the area is difficult to map by photo-interpretion.
The gabbro and diorite to the south and southwest of the Seven Sisters f o r m low un­
dulating r i s e s only slightly higher than the s o i l - c o v e r e d plains. E l s e w h e r e , the gabbro
and d i o r i t e g e n e r a l l y crop out in isolated steep hills r i s i n g abruptly from the coastal
plain. The hills v a r y in height; f o r example, Bald Hill is 250 feet above sea l e v e l and
Mount Luce 900 feet. Dioritic roof pendants occur near the summit of Mount Roundback
(2400 f t ) . Camp Island consists of r o c k s mapped with this group.
Slopes devoid of vegetation and c o v e r e d with l a r g e rounded boulders of gabbro occur
in p l a c e s on the hills as, for e x a m p l e , on the northern side of Mount L u c e . The slopes
appear black when seen from a distance, and are c l e a r l y recognizable on air-photographs.
Lithology
Arkendeith to Beaks Mountain
The area f r o m Arkendeith to Beaks Mountain contains a l a r g e number of r o c k types:
g r a n o d i o r i t e , d i o r i t e , and adamellite, and their fine-grained equivalents, predominate;
there a r e l e s s e r amounts of gabbro, granite, and m i c r o g r a n i t e . Hornblende i s a major
constituent of the calcic r o c k s .
Between P l u m t r e e Hill and P l u m t r e e homestead the country is gently undulating and
outcrop is s p a r s e . The area consists mainly of diorite and granodiorite, with subordinate
a d a m e l l i t e , gabbro, and granite. Dykes of m i c r o d i o r i t e and m i c r o a d a m e l l i t e w e r e also
noted. Some of the granodiorite is weakly foliated. Most of the rocks are c a l c i c , and weather
to a dark brown to black soil containing abundant l i m e - r i c h nodules.
South of the Bobawaba Range many p a r a l l e l s w a r m s of dykes intrude d i o r i t e and
g r a n o d i o r i t e . The dykes are so abundant that in places they predominate o v e r the
host r o c k s . The trend of the dykes swings f r o m approximately meridional in the south
to north-northwest in the north, w h e r e they a r e normal to the Inkerman Shear Zone.
The dykes include porphyritic m i c r o g r a n i t e , m i c r o a d a m e l l i t e , m i c r o d i o r i t e , m i c r o g r a n o d i o r i t e , and d o l e r i t e . The c o a r s e - g r a i n e d m o r e leucocratic r o c k s a r e foliated
p a r a l l e l to the trend of the dykes. The m o r e melanocratic rocks are not foliated.
South of Arkendeith there is a second zone of dyke s w a r m s which intrude granodiorite,
d i o r i t e , and adamellite. The dykes continue into, and are younger than, the Inkerman
Shear Zone. Epidotization along joints i s common, and may extend a few inches out f r o m
the joints.
A small deposit of asbestiform t r e m o l i t e was noted by Carruthers (1954) about 1 m i l e
south of Arkendeith. The outcrop is s i m i l a r to the material found in S i x - M i l e C r e e k in
the Inkerman Shear Zone.
The Rocks is a l a r g e area of w a t e r w o r n outcrop in the bed of the Burdekin R i v e r
southeast of K e l l y s Mount. Most of the r o c k types in the adjacent a r e a s a r e exposed here
in almost continuous outcrop, and the sequence of events was as follows:
(1) Emplacement of tonalite, containing f a i r l y abundant tabular xenoliths of m e l a n o ­
c r a t i c foliated hornblende-biotite m i c r o g r a n o d i o r i t e up to 1 foot long.
16
(2) Intrusion of a second granodioritic phase as i r r e g u l a r m a s s e s of c o a r s e - g r a i n e d
hornblendic r o c k s .
(3) Intrusion of i r r e g u l a r m a s s e s of porphyritic m i c r o g r a n o d i o r i t e . The m i c r o granodiorite contains abundant hornblende xenoliths of the c o a r s e - g r a i n e d hornblende
granodiorite. Epidotization is common along joints in the m i c r o g r a n o d i o r i t e .
(4) Intrusion of dykes of flow-banded spherulitic dacite. The dacite is porphyritic
in places, and the c o a r s e flow layering ranges from pink to pinkish g r e y . The dykes are
up to 40 feet thick and have no consistent trend.
(5) Intrusion of i r r e g u l a r masses of medium-grained porphyritic m i c r o d i o r i t e .
The m i c r o d i o r i t e contains phenocrysts of plagioclase and has been extensively epidotized
along joints.
(6) Intrusion of m i c r o d i o r i t e dykes. The dykes are fine-grained and dark green to
almost black; they a r e commonly porphyritic in the centre and generally have fine-grained
chilled m a r g i n s . The dykes a r e of at least three a g e s , and have no regular trend.
The Inkerman Shear Zone is at least 2 m i l e s w i d e . Shearing and metasomatic alteration
of diorite and granodiorite have produced many v a r i e t i e s of r o c k s , but some of the original
rocks are unaltered.
In S i x - M i l e C r e e k , near Leichhardt Downs homestead, a section across most of the
shear zone can be seen. T h e r e are wide exposures of d i o r i t e gneiss, which in places
contain lenses of m a s s i v e d i o r i t e . Rocks rich in v e r m i c u l i t e , dyke-like m a s s e s of garnet
rock, epidote r o c k s , thin quartz v e i n s , magnetite bodies, amphibole-epidote-garnet r o c k s ,
and amphibolite a r e also found in the zone of alteration,
The g r a i n s i z e of the gneiss is v a r i a b l e . Some of it is fine-grained, uniformly banded,
and strongly c l e a v e d owing to p a r a l l e l growth of hornblende c r y s t a l s . C o a r s e - g r a i n e d
pegmatitic pods with biotite flakes and plagioclase c r y s t a l s up to 1 inch a c r o s s a r e also
present. In p l a c e s the gneiss is contorted. The banding is commonly lenticular and of
v a r i a b l e width. Hornblende-rich bands are plentiful.
Two tabular bodies of metasomatic garnet rock, probably dykes, w e r e noted. The
f i r s t is composed of about 95 percent brown garnet with a little intergranular quartz and
small grains of diopsidic(?) p y r o x e n e . The garnet shows excellent sector twinning and
multiple twinning. Some of the c r y s t a l s are strongly zoned. The second body is composed of
pale y e l l o w - g r e e n isotropic garnet c r y s t a l s r i m m e d by anisotropic brown garnet, and
about 5 percent intergranular quartz. The garnetiferous r o c k s appear to have been formed
after the shearing, possibly by metasomatic alteration of m i c r o d i o r i t e dykes. Turner
(1933) has d e s c r i b e d a suite f r o m Westland, New Zealand, in which highly garnetiferous
rocks w e r e developed f r o m gabbro during metasomatism and strong regional metamorphism,
Benson (1913) noted numerous occurrences of garnet-bearing altered gabbro in the
Great Serpentine Belt in northern New South W a l e s , in which the proportion of garnet
ranges f r o m a few percent to almost 100 percent. White (1959) has noted the coexistence
of two calcium garnets in the same rock in South Australia; it occurs in a zone where
c a l c - s i l i c a t e r o c k s a r e veined by migmatite, gneiss, and granite, and was formed as a
result of metasomatism and interaction between mineral phases.
The magnetite-epidote-quartz-garnet rocks contain about 60 percent euhedral brown
sector twinned garnet, 20 percent quartz, 10 percent epidote, and 10 percent magnetite.
Epidote r o c k s , which w e r e not seen in situ, consist of about 98 percent epidote and
2 percent of an amorphous brown material which has possibly been formed by the r e p l a c e ­
ment of biotite.
17
A m p h i b o l e - r i c h rocks a r e c o m m o n in S i x - M i l e C r e e k . One consists entirely of c o l o u r ­
l e s s t r e m o l i t e , and another consists of 85 percent g r e e n hornblende and 15 percent
a g g r e g a t e s of talc poikiloblastically enclosed in the hornblende. Other specimens examined
contain t r e m o l i t e and talc in about equal quantities, and in one of them the talc appears
to r e p l a c e t r e m o l i t e . A l l the amphibole-rich rocks have a foliation due to the orientation
of the amphibole c r y s t a l s .
Foliated quartz-garnet-augite r o c k and garnet-wollastonite-diopside r o c k have been
noted 8 m i l e s south-southeast of Home H i l l . Both have a granulitic texture. In the f i r s t
the quartz grains a r e elongated and the garnet is l a r g e l y segregated into distinct l a y e r s ;
p l a g i o c l a s e is extensively altered to c l i n o z o i s i t e . In the second, there is little evidence
of foliation apart from the p a r a l l e l i s m of the inclusions in the garnet; it is composed
of about 50 percent garnet, together with wollastonite, diopside, c a l c i t e , and quartz.
T w o types of garnet are present; one is colourless and isotropic, the other i s brown and
anisotropic and shows sector twinning. Both rocks appear to have been f o r m e d by
metasomatic alteration of g n e i s s e s .
T r a c e s of secondary copper m i n e r a l s and sporadic grains of chalcopyrite w e r e found
in parts of the shear zone; s p e c t r o g r a p h ^ analyses of four samples are given in Appendix
1.
Intruded into the shear zone a r e two swarms of dark green fine-grained m i c r o d i o r i t e
and porphyritic hornblende gabbro dykes, and small plugs of m a s s i v e granite. Most of the
dykes trend either p a r a l l e l to or normal to the shear direction.
A t various places in the bed of the Burdekin R i v e r there are l a r g e a r e a s of w a t e r w o r n outcrop. Between The Rocks and the southern edge of the Sheet area there a r e a
number of s i m i l a r outcrops consisting of foliated granite, granodiorite, and d i o r i t e which
have been sheared and mylonitized in p l a c e s . The foliation and shear directions a r e v a r ­
iable, and a r e not parallel to the Inkerman Shear Zone. The sheared r o c k s a r e intruded
by dykes of m i c r o a d a m e l l i t e , porphyritic m i c r o d i o r i t e , micromonzonite, and dark g r e e n
fine-grained m i c r o d i o r i t e . Quartz veining and epidotization, especially along joints, a r e
common in p l a c e s .
A low r i d g e of crudely banded basic plutonic r o c k s , surrounded by alluvium, occurs
1 m i l e southwest of Sandalwood W a t e r h o l e , west of the Burdekin R i v e r . The specimen
sectioned i s an olivine m i c r o g a b b r o . The outcrop strongly r e s e m b l e s s i m i l a r l a y e r e d
gabbroic outcrops in the eastern part of the Sheet area.
Eastern P a r t of Sheet A r e a
In the eastern part of the Sheet area this unit includes diorite, d o l e r i t e , gabbro,
and norite. Some of the rocks are m a s s i v e , others a r e l a y e r e d .
One specimen f r o m the eastern foothills of Mount Little is a c o a r s e m a s s i v e d i o r i t e
which has been slightly r e c r y s t a l l i z e d by the granite ( P - M g ) in the saddle between
Sprole Castle and Mount L i t t l e . A s i m i l a r diorite crops out at the summit of Sprole
C a s t l e , and blocks of augite d i o r i t e and banded m i c r o d i o r i t e occur on the southern s l o p e s ,
in the Bowen Sheet a r e a .
Olivine gabbro, olivine m i c r o g a b b r o , and leucocratic olivine norite f o r m a low r i s e
i m m e d i a t e l y east of A l l i g a t o r Swamp (north of the railway line, 5 m i l e s west-northwest of
Bowen). In places they are weakly banded; the bands trend east-west and dip subvertically.
Segregations of gabbro pegmatite occur in places, and some of the rocks a r e intruded by
biotite pegmatite and aplite dykes. The olivine norite contains 10 percent fresh olivine
with a ubiquitous reaction r i m of pale brown hornblende. An intervening r i m of hypersthene
may also be present. The opaque grains a r e also r i m m e d by amphibole.
18
Banding is well displayed in waterworn boulders and to a lesser extent in outcrops
of the basic rocks at Abbot Point. The gabbros are generally coarse-grained, but there is
considerable variation in the grainsize, texture, and composition of individual bands and
boulders. In places the banding in the gabbro has been truncated by a later banded intrusion
( F i g . 4 ) . The banding may be sharp or vague, and small folds and contortions are common
within individual bands ( F i g . 5 ) .
F i g . 4:
Contortion and truncation of banding in gabbro ( C - P d ) . Waterworn boulder
at Abbot Point.
F i g . 5:
Waterworn boulder of banded gabbro ( C - P d ) at Abbot Point. Truncation,
disruption, and wedging of bands (probably due to contemporaneous erosion
during gravitational deposition) are v i s i b l e in the lower part of the boulder.
The small disharmonic folds ( e . g . right centre and extreme left) w e r e p r o b ­
ably caused by slumping during deposition. The scale is 6 inches long.
19
Fig 6
Waterworn boulder of
gabbro ( C - P d ) at Abbot
Point. The squat euhedral
plagioclase phenocrysts,
2 to 3 c m in diameter,
contain small f e r r o magnesian nuclei, and in
places concentric bands
of ferromagnesian min­
e r a l s . The groundmass
consists of roughly equal
proportions of plagioclase
and ferromagnesian
m i n e r a l s . The scale i s
6 inches long.
F i g . 7:
Waterworn boulder of gabbro ( C - P d ) at Abbot Point. A gabbro pegmatite
segregation occupies the c o r e of a ' r o o t l e s s ' fold in the banding. A f i n e r grained v e i n - l i k e extension of the pegmatite has been intruded along the axial
plane of the fold. The l a r g e s t feldspar and ferromagnesian crystals are
2 inches long.
20
F i g . 8:
Planar banding in anorthite gabbro ( C - P d ) , on the coast half a m i l e northeast
of Mount Luce.
Some of the coarsely porphyritic rocks contain large squat euhedral crystals of p l a g i o ­
c l a s e 2 to 3 c m across ( F i g . 6 ) . Some of the phenocrysts have a small mafic nucleus
and one or m o r e thin concentric zones of fine-grained mafic minerals. Segregations of
gabbro pegmatite are common in the c o r e s of folds in the banding ( F i g . 7 ) . R a r e thin veins
and lenticles of a fine-grained melanocratic rock transgress most of the other structures.
Finally a thin network of late pegmatitic veins is present in places.
Coarse inequigranular massive uralitized gabbro crops out in the southwestern foot­
hills of Mount Luce, and banded uralitized anorthite gabbro, containing large poikilitic
c r y s t a l s of hornblende, f o r m s the small hill on the coast northeast of Mount Luce. The
o
banding, which dips at 60 south ( F i g . 8), is regular, but the bands do not show such marked
variation in composition, texture, and grainsize as the banding at Abbot Point. The beach
sands along the shore near Mount Luce and Abbot Point contain a high concentration of
heavy minerals derived from basic r o c k s . The mineralogical composition of the beach sand
compared with the composition of the augite-hornblende gabbro from the small hill north­
east of Mount Luce is given in Appendix 2.
The basic plutonic rocks near the summit and on the shoulders of Mount Roundback
appear to be roof pendants in granite ( C - P g ) . They are probably similar to outcrops at
Abbot Point. Massive melanocratic d o l e r i t e ( ? ) , permeated by veins and stringers of gabbro
pegmatite, crops out in the western foothills.
Numerous rounded boulders of gabbro e m e r g e from the black soil in the low-lying
country south and west of the Seven Sisters. Diorite and tonalite are also present. Both
the diorite and tonalite contain melanocratic xenoliths.
Medium-grained massive hornblende-augite norite crops out at Moosie Hill and coarse
massive hornblende-hypersthene gabbro is intruded by or interlayered with thin bands of
hypersthene-hornblende microgabbro in the small hill immediately to the northeast.
Coarse medium and fine-grained basic or intermediate plutonic rocks crop out on the
northeast side of Camp Island. They are commonly dyke-like and cut each other. Layering
i s not as marked as at Abbot Point. A thin dyke of spinel-bearing 'uralitized' diallagite
intrudes gabbro or diorite; 90 percent of the rock consists of fibrous to prismatic richte r i t e ( ? ) and subordinate diallage; the richterite has been formed by replacement of
21
diallage.
Numerous fractured
crystals
of green spinel
and a few anhedral grains of
bytownite a r e also present.
A t Red H i l l , 8 m i l e s northwest of Guthalungra, the Bruce Highway c r o s s e s low hills
of olivine microgabbro and gabbro.
Two small hills near Green Hill, on the coast north of Gumlu, consist of coarse to
fine-grained melanocratic gabbro with random patches of leucocratic gabbro. A local
weak foliation trends at 110 . L a r g e xenoliths of sheared granite a r e present in the
gabbro in a wavecut platform on the seaward side of the m o r e northerly of the two
hills.
Structure
Arkendeith to Beaks Mountain
The intermediate to basic r o c k s between Arkendeith and Beaks Mountain are strongly
foliated in p l a c e s . The direction and intensity of the foliation are not constant, and in
places it is c l e a r l y associated with shear zones and faults.
The joint patterns are generally i r r e g u l a r , but some outcrops are c l o s e l y jointed.
Polygonal joint patterns are common, but the angles between the joints v a r y in the adjacent
rock types.
In addition to the Inkerman Shear Zone s e v e r a l faults a r e shown on the map. A l l
have caused strong foliation l o c a l l y . The Inkerman Shear Zone dips v e r t i c a l l y , and is at
least 2 m i l e s w i d e .
Eastern Part of Sheet A r e a
Shearing was not observed in the intermediate to basic rocks in the eastern part of
the Sheet area.
No p r i m a r y layered structures of regional extent are manifest f r o m the isolated
measurements which have been made, and the contortions in the banding at Abbot Point
suggest that the structures in the banding are of local significance only.
A g e and Relationships
The country rocks of the intermediate to basic plutonic rocks have been entirely
r e m o v e d by erosion except for small roof pendants of hornfels (Pzu) near Guthalungra.
The age of the hornfels is unknown. In the Bowen Sheet area the relationships of the
plutonic rocks to fossiliferous sediments a r e inconclusive, but the balance of evidence
suggests that they are older than the L i z z i e C r e e k Volcanics ( L o w e r Bowen Volcanics
of Malone et a l . , 1966) which contain L o w e r P e r m i a n f o s s i l s . Isotopic ages ranging from
270 to 285 m . y . have been obtained by the K / A r method on biotite and hornblende from a
s i m i l a r group of rocks ( C - P d ) in the Bowen Sheet area. H o w e v e r , recent R b / S r total rock
determinations on some of the same specimens indicate that the true age of emplacement
was about 310 m . y . (Upper Carboniferous), and that the younger ages obtained by the K / A r
method may be due to loss of argon during the widespread intrusion of granite in the
L o w e r P e r m i a n ( A . W . Webb, p e r s . c o m m . ) .
T h r e e isotopic age determinations on amphiboles have been c a r r i e d out by the K / A r
method on sheared rocks from the Inkerman Shear Zone. T w o specimens of diorite
gneiss have yielded ages of 265 to 275 m . y . ( L o w e r P e r m i a n ) ; and a specimen of green
amphibole rock has yielded an age of 245 m . y . (Upper P e r m i a n ) . However, it is not known
to what extent these ages r e f l e c t r e c r y s t a l l i z a t i o n and metasomatism.
22
The p r e s e n c e of cobbles of sheared diorite in the Upper Devonian (?) calcareous
c o n g l o m e r a t e at Charlies Hill suggests that equivalents of the Ravenswood Granodiorite
( S i l u r i a n / L o w e r Devonian) may exist south of Home H i l l .
A C I D P L U T O N I C ROCKS ( C - P g )
The acid intrusions ( C - P g ) crop out at scattered l o c a l i t i e s throughout the Sheet area.
T w o small hills 3 m i l e s south of White Rock Bay (Cape Cleveland peninsula) consist of
f i n e - g r a i n e d foliated biotite adamellite. The hills are much lower than the main part of
the Cape Cleveland range, which i s composed of m a s s i v e c o a r s e biotite adamellite ( P - M g ) .
The foliated adamellite appears to have been intruded by the m a s s i v e a d a m e l l i t e . In the
foliated rock, which is gneissic in p l a c e s , the foliation dips at 45 to the southeast. It
is composed of xenomorphic quartz, perthite, and sodic p l a g i o c l a s e t r a v e r s e d by thin
t r a i l s of biotite.
A r t i l l e r y H i l l / M a j o r C r e e k Mountain. Pink c o a r s e l y porphyritic m i c r o g r a n i t e
f o r m s two north-northwesterly ranges, up to 900 feet high, northwest of the Haughton
R i v e r ; the ranges include A r t i l l e r y Hill and Major C r e e k Mountain. In the northern
bank and bed of Major C r e e k , south of A r t i l l e r y Hill, the pink and r e d porphyritic m i c r o granite is brecciated.
The m i c r o g r a n i t e in the eastern range contains rounded phenocrysts of quartz and
white euhedral c r y s t a l s of feldspar averaging 5 to 6 m m , but up to 3 c m , a c r o s s set in
a fine-grained pink groundmass. The microgranite is aphyric in p l a c e s . R a r e c h l o r i t i z e d
biotite is the chief mafic m i n e r a l . M i c r o d i o r i t e dykes a r e abundant in both ranges.
The contact between the m i c r o g r a n i t e and the Carboniferous to P e r m i a n volcanics
( C - P v ) to the northwest was not seen, and their age relationship is unknown.
The m i c r o g r a n i t e c l o s e to a m i c r o d i o r i t e dyke which intrudes it near a g r a v e l pit
at the northern end of the steep hill immediately southeast of Mount Ironbark has been
a l t e r e d to a white siliceous rock containing disseminated p y r i t e .
A sheet-like intrusion, which ranges from medium-grained biotite granite to g r a n o phyric alkali m i c r o g r a n i t e , f o r m s a low hill half a m i l e west-southwest of Mount W o o d house. The intrusion is 300 feet thick and dips at a moderate angle to the east-northeast.
The r o c k is generally weakly foliated, particularly the granophyric m i c r o g r a n i t e at the
southern end. Several different m i c r o g r a n i t e intrusions a r e present, and in p l a c e s they
have been contaminated by the assimilation of country r o c k . The m i c r o g r a n i t e intrudes
deeply eroded blue-grey hornblende-biotite granodiorite (Ravenswood G r a n o d i o r i t e ) .
T w o small intrusions of fine-grained white leucocratic granodiorite and quartz
d i o r i t e intrude the Ravenswood Granodiorite 2 m i l e s north-northwest of Mount Woodhouse.
Both intrusions a r e strongly fractured in a north-south direction.
Mount Benjonney is a roughly oval stock of alkali granite which is sparsely vegetated
and strongly jointed. The granite is g r e y , even textured, fine to m e d i u m - g r a i n e d , and
leucocratic, and contains numerous small hornblendic xenoliths. It intrudes the R a v e n s ­
wood Granodiorite. Biotite is the chief mafic constituent. No dykes w e r e noted in the
alkali granite, which postdates the various dykes intruding the Ravenswood Granodiorite
nearby.
An i r r e g u l a r mass of medium-grained blue-grey granodiorite intrudes quartzite
(Pzu) 2 m i l e s west of Mount Benjonney; it may also intrude the hornblende granodiorite
(Ravenswood Granodiorite) which partly surrounds it. The granodiorite is leucocratic,
and contains abundant l a r g e phenocrysts of plagioclase which in places a r e surrounded
by m i c r o p e g m a t i t e . Some hornblende is present. The granodiorite is intruded by g l o m e r o porphyritic plagioclase-hornblende porphyry dykes.
23
Red alkali m i c r o g r a n i t e c r o p s out in an arcuate r i d g e , 250 feet high, 3 m i l e s west
of Mount Benjonney; two s m a l l e r a r e a s east and west of the r i d g e have been photo-inter­
p r e t e d as m i c r o g r a n i t e . The alkali m i c r o g r a n i t e has a graphic texture in p l a c e s , and con­
tains scattered s m a l l basic and intermediate xenoliths, some of which have been converted
to mafic clots by assimilation. Biotite, amphibole ( f e r r o a c t i n o l i t e ? ) , and subordinate
clinopyroxene together constitute l e s s than 5 percent of the r o c k . Chlorite and epidote
have been f o r m e d by deuteric alteration.
The scattered fragments of hornblende granodiorite in the m i c r o g r a n i t e w e r e
d e r i v e d f r o m the Ravenswood G r a n o d i o r i t e . Other xenoliths, chiefly feldspar-hornblende
porphyry, a r e s i m i l a r to the dyke in the Ravenswood Granodiorite to the east of the
m i c r o g r a n i t e . N o dykes w e r e noted in the m i c r o g r a n i t e .
An oval stock of pink medium-grained biotite adamellite crops out in the headwaters
of Barratta C r e e k . The adamellite intrudes the Ravenswood Granodiorite, and c l o s e l y
r e s e m b l e s the biotite adamellite stock in Molybdenite C r e e k in the northeastern corner
of the Charters T o w e r s Sheet area (Wyatt et al., 1967, unpubl., and in p r e p . ) . No dykes
appear to be p r e s e n t .
The spur of the Mount D a l r y m p l e range which r i s e s west-northwest f r o m the junction
of Deep C r e e k and the Burdekin R i v e r consists of granite aplite and alkali m i c r o g r a n i t e .
The intensely fractured pinkish brown granite aplite in the west bank of the Burdekin
R i v e r is locally v e r y fine-grained and commonly flow banded. It is intruded by a porphyritic
m i c r o d i o r i t e dyke and a thin fine-grained biotite adamellite dyke.
The fine-grained brownish g r e y alkali microgranite in the main spur of the range also
shows i r r e g u l a r banding, with the r a r e micaceous m i n e r a l s strung out in fine i r r e g u l a r
l a y e r s . One and a half m i l e s up Deep Creek, a small body of s i m i l a r brownish g r e y
m i c r o g r a n i t e intrudes and hornfelses Upper Carboniferous volcanics (Cuv). Near the
contact the m i c r o g r a n i t e contains blocks of hornfelsed vesicular porphyritic v o l c a n i c s .
The alkali m i c r o g r a n i t e is strongly fractured by the Woodhouse Fault. It intrudes the
Ravenswood G r a n o d i o r i t e , which i s c o v e r e d by s c r e e and alluvium at the eastern end of
Mount D a l r y m p l e .
A p o o r l y defined body of granite f o r m s the southeastern e x t r e m i t y of the Mount
D a l r y m p l e r a n g e . Pink medium to c o a r s e - g r a i n e d leucocratic alkali granite, which
i s slightly porphyritic and granophyric, i s exposed in a quarry north of Landers C r e e k
homestead. T o the southwest, the granite contains rounded quartz phenocrysts averaging
2 m m in d i a m e t e r . The granite i s c l o s e l y associated with a pink granophyric m i c r o g r a n i t e
containing r a r e phenocrysts of fine feldspar. In the quarry, the granite i s strongly
shattered by a northwesterly fault zone which is intruded by numerous greenish g r e y
porphyritic m i c r o d i o r i t e dykes.
One m i l e northwest of the quarry, g r e y to pink medium-grained granophyre is intruded
by dark greenish blue m i c r o d i o r i t e dykes.
The contact between the granophyre and the Upper Carboniferous (?) Volcanics
(Cuv) was examined in this a r e a , but the relationships w e r e not established; the volcanics
at the contact do not appear to be metamorphosed, and the granite may t h e r e f o r e be the
older.
Pink f i n e - g r a i n e d leucogranite, intruded by numerous rhyodacite and rhyolite dykes,
f o r m s a broad, a l m o s t imperceptible r i s e surrounded by alluvium, between Gladys Lagoon
and the Burdekin R i v e r .
K e l l y s Mount, 8 m i l e s southwest of A y r , is an uneven granite hill r i s i n g 600 feet above
sea l e v e l ; it i s surrounded by a broad apron of sand. The northern spur consists of c o a r s e
m a s s i v e leucocratic biotite granite composed of m i c r o c l i n e perthite, quartz, a l b i t e -
24
o l i g o c l a s e , and biotite. A little chlorite and rutile (after b i o t i t e ) , and z i r c o n associated
with iron oxides and muscovite, a r e present. The p l a g i o c l a s e shows incipient s e r i c i t i z ation, and the potash feldspar is commonly cloudy. Greisen is e x t e n s i v e l y developed on
the northeastern slopes of the hill. Several costeans and benches have been bulldozed
in it. No mineralization was seen in the field, but one specimen was found to contain 300
ppm of molybdenum (see Appendix 1 ) . Thin basic to intermediate dykes intrude the granite
on the southern slopes.
The range 2 J m i l e s ^southwest of K e l l y s Mount consists of adamellite, and is also
surrounded by a broad apron of sand. The rock is well exposed in a r o a d - m e t a l quarry
at the southeastern end of the range. It is a massive medium-grained pink biotite adamellite
composed of o l i g o c l a s e , perthite, quartz, and biotite which has been mostly altered to
chlorite and epidote. Potash feldspar and quartz a r e commonly intergrown; the biotite
has been partly replaced by potash feldspar; and the quartz c r y s t a l s a r e strained. The
a c c e s s o r i e s include iron oxides, apatite, and z i r c o n . The adamellite is generally slightly
epidotized, particularly along small faults. A g g r e g a t e s of p y r i t e occur in association with
quartz and small r o s e t t e s of muscovite in r a r e pegmatitic s e g r e g a t i o n s . C o a r s e a g g r e g a t e s
of quartz, c a l c i t e , epidote, and pyrite occur as lenses and as the linings of small v u g s .
A swarm of thin amygdaloidal pyritiferous augite dolerite dykes intrudes the a d a m e l l i t e .
The granitic rocks f o r m the G r e g o r y Ranges, and extend east to Be'aks Mountain, but
f o r m l o w - l y i n g country in p l a c e s , where outcrop is p o o r , and weathering deep.
The main r o c k types a r e deeply weathered leucocratic pink adamellite and biotite
granite, which in p l a c e s are strongly sheared. Jointing is g e n e r a l l y w e l l developed.
T h e r e are numerous dykes of m i c r o d i o r i t e , m i c r o a d a m e l l i t e , m i c r o g r a n i t e , r h y o l i t e ,
rhyodacite, dacite, and related p o r p h y r i e s . They commonly occur in s w a r m s , and in some
a r e a s the dykes a r e so c l o s e together that outcrop of the host r o c k i s r a r e ( e . g . , near
Beaks Mountain). Most of the dykes trend between 315 and 045 .
Shearing is common in some a r e a s , especially east of the Burdekin R i v e r , but it is
not related to any of the known major shear directions. The trend of the shearing ranges
from about 060 to 160 , and the dip is generally v e r t i c a l .
The Mount Louisa rhyolite plug ( C - P h ) intrudes granite mapped with this unit. No
contacts w e r e seen with the dioritic rocks ( C - P d ) to the north.
Mount Inkerman is an inselberg which r i s e s steeply to 700 feet above sea l e v e l , and
is elongated in a northeasterly direction. It is composed of strongly sheared and jointed
foliated granite. The foliation trends northeast by east, and Mount Inkerman is interpreted
as lying within the Inkerman Shear Zone, which has affected the granodiorite and d i o r i t e
( C - P d ) in the hills to the southwest. The granite at Mount Inkerman contains xenoliths
of biotite schist and i s cut by dykes of m i c r o d i o r i t e which postdate the shearing. The
geology of Mount A l m a i s s i m i l a r .
A small hill near Stud Lagoon, 4 m i l e s southwest of Mount Inkerman, also l i e s within
the Inkerman Shear Zone. It consists of sheared, r e c r y s t a l l i z e d , and hydrothermally
altered granite composed mainly of equigranular quartz and feldspar with cubes of magnetite
and small c r y s t a l s of r e d garnet.
Sparse outcrops of probable granitic rocks along the southern boundary of the Sheet
area 5 m i l e s southwest of Guthalungra have been included in this unit. On the air-photographs
the area appears to consist almost entirely of low r i s e s , f r o m which e m e r g e r a r e c o r e stones. Biotite adamellite c r o p s out 2 m i l e s to the south on the Bowen Sheet. An isotopic
age of 270 m . y . ( K / A r on b i o t i t e , + 3 percent) has been obtained f r o m adamellite in Finlay
C r e e k 8 m i l e s south of Guthalungra.
25
Beach Hill i s a steeply rounded inselberg r i s i n g abruptly to o v e r 400 feet above sea
l e v e l . It consists of granulated and brecciated granite which has been r e c r y s t a l l i z e d .
M o s t of the granite is strongly joined; the most prominent joints trend 090 and dip north
at between 50 and v e r t i c a l . In a few a r e a s the granite has a weak e a s t e r l y foliation, but
it i s g e n e r a l l y granular and m a s s i v e .
Some of the m i c r o d i o r i t e dykes in the granite a r e foliated, others a r e m a s s i v e . It
appears that the m i c r o d i o r i t e was intruded during and after the brecciation and shearing
of the granite.
Probably m o r e than one p e r i o d of faulting affected this area. The prominent 090°joint direction does not appear to be related to the northeasterly trend of the Inkerman
Shear Zone (which, unless it has died out, should pass c l o s e by) or the north-northwest
to northwesterly trend of the Sugar Loaf Fault. Beach Hill culminates in a central spine
aligned on strike with the Sugar Loaf Fault.
Sugar Loaf, an i n s e l b e r g r i s i n g 100 feet above sea l e v e l , consists of sheared granite.
The shearing trends southeast, p a r a l l e l to the beach. The shear zone (Sugar Loaf Fault)
terminates in a cliff of my lord te on the seaward side of the hill. About 30 feet inland from
the cliff, the r o c k is l e s s sheared and grades into gneiss containing augen of feldspar
and quartz. Sixty feet farther inland the rock becomes recognizable as granite. A l l the
r o c k s are strongly jointed and w e a t h e r e d .
A few low outcrops of deeply weathered and sheared granite crop out near the mud
flats on the northwestern side of G r e e n H i l l . Green Hill is terminated at its northeastern
edge by a wide m a s s of quartz which was probably intruded along the continuation of the
Sugar Loaf Fault.
Nobbies Lookout, another 400 foot inselberg 5 m i l e s northwest of Guthalungra, is
composed of weathered m a s s i v e fine-grained granodiorite.
The outcrops extending w e s t w a r d s from The Cape homestead include low r i s e s ,
gentle s l o p e s , and steep hills and spurs. These culminate in a steep i r r e g u l a r w e s t - n o r t h ­
w e s t e r l y range which r i s e s 600 feet above sea l e v e l 4 m i l e s west-northwest of The Cape
homestead. The range is separated f r o m the main Cape Upstart peninsula range (2400 ft)
by an e a s t - w e s t v a l l e y with a low central saddle.
The range trending west from The Cape homestead consists of tonalite and adamellite.
Medium-grained garnetiferous biotite tonalite (locally foliated) has intruded and hornfelsed
the sediments ( P z u ) 1 m i l e west-southwest of the homestead. It consists of o l i g o c l a s e andesine (50%); anhedral strained and granulated quartz (30%), in places r e c r y s t a l l i z e d ;
clots of fine biotite (1^%) ( r e c r y s t a l l i z e d ? ) ; interstitial to poikilitic m i c r o c l i n e (5%); and
r a r e r e d - b r o w n garnet.
The r o c k immediately north of the homestead is a m a s s i v e c o a r s e inequigranular
biotite adamellite composed of r e c r y s t a l l i z e d quartz (35%), oligoclase-andesine (30%),
perthite (30%), and fine-grained a g g r e g a t e s of biotite (5%). The rock contains s o m e fine­
grained d i o r i t i c xenoliths.
A thick d y k e - l i k e body of biotite leucoadamellite trends east-west along the northern
slopes of the r a n g e . It consists of o l i g o c l a s e (40%), poikilitic quartz (35%), perthite (25%),
and a little biotite.
An isolated hill on the coast north of Nobbies Inlet consists of m a s s i v e brown mediumgrained biotite leucoadamellite composed of strained quartz (35%), poikilitic m i c r o c l i n e
perthite (35%), andesine (30%), and a few flakes of biotite.
east
The Maiden Mountain, a 400-foot hill immediately north of the Bruce Highway 2 m i l e s
of Guthalungra, consists of fine-grained biotite-hornblende alkali granite aplite.
26
It is composed mainly of albite, potash feldspar, and quartz, and has an inequigranular
xenomorphic texture. A few c r y s t a l s of poikilitic green hornblende and c h l o r i t i z e d biotite
a r e also present. The a c c e s s o r i e s a r e iron oxide and sphene. In places the r o c k is banded,
and some bands a r e noticeably m o r e aplitic than others. Rubble of strongly epidotized
basic to intermediate dykes is abundant.
The Seven Sisters is a steep-sided linear inselberg of slightly to m o d e r a t e l y foliated
leucocratic granite south of the Bruce Highway, 3 m i l e s east-southeast of Guthalungra.
The inselberg, which r i s e s gradually to 500 feet above sea l e v e l at its eastern end, has
a pronounced east-west trend p a r a l l e l to the foliation. The foliation is only slight at the
w e s t e r n end, but is m o r e pronounced in the east, where the mafic aggregates a r e drawn out
into l e n s e s . The western end of the range consists of aplitic, leucocratic hornblendebiotite granite composed of quartz, o l i g o c l a s e , poikilitic m i c r o c l i n e , and a little biotite,
hornblende, pyrrhotite, and epidote. A few phenocrysts of plagioclase and quartz a r e
present. Rubble f r o m epidotized dolerite and m i c r o d i o r i t e dykes is abundant at the
w e s t e r n end of the r i d g e .
The southeastern slopes of Mount Cur l e w i s , an inselberg which r i s e s 700 feet above
sea l e v e l on the coast 7 m i l e s east of Guthalungra, consist of weakly foliated inequigranular
leucocratic aplitic biotite granite. Quartz f o r m s xenoblastic grains 0.3 m m a c r o s s in
a g g r e g a t e s 1 m m a c r o s s . Sodic p l a g i o c l a s e and m i c r o c l i n e a r e roughly tabular, but much
of the feldspar has been r e c r y s t a l l i z e d into fine-grained a g g r e g a t e s . Biotite is also r e c r y s t a l l i z e d as strings of small flakes.
Medium-grained biotite leucogranite ( C - P g , shown in e r r o r on the map as C - P d ) is
w e l l exposed in a railway ballast quarry on the western side of Mount C a r e w , a small
i n s e l b e r g li m i l e s west by south of Wilmington railway siding. The leucogranite is in­
truded by pyritiferous basic to intermediate dykes. A quarry w o r k e r r e p o r t e d that he had
found m a s s e s of p y r i t e s e v e r a l inches across in the leucogranite.
North of Mount Roundback the granitic rocks crop out mainly as undulating r i s e s
with scattered small outcrops and bare expanses of r o c k up to 100 yards a c r o s s . The
granitic rocks f o r m most of Mount Roundback, but they a r e masked in p l a c e s by s c r e e
f r o m dioritic roof pendants.
The white hornblende-biotite adamellite, beside a r a i l w a y l e v e l - c r o s s i n g 2 m i l e s
east of Wilmington siding, i s m a s s i v e and c o a r s e - g r a i n e d . It is composed of zoned
o l i g o c l a s e , perthite, quartz, biotite, and chloritized green amphibole; the mafic clusters
include sphene, apatite, z i r c o n , iron oxides, and allanite.
M a s s i v e boulders of c o a r s e white granite occur beside the track near K a l l i V a l l e y
homestead; quartz-hornblende latite porphyry crops out nearby, but its relationship to
the granite is unknown.
The northeastern foothills of Mount Roundback a r e composed of hornblende-biotite
adamellite.
A narrow belt of granite o r granodiorite intrudes gabbro on the seaward side of
Mount L u c e . The outcrop is about 50 feet wide and at least 300 feet long, and the contact
dips at about 50° to the south. The granite has been contaminated by the gabbro, and
contains numerous basic xenoliths and schlieren elongated p a r a l l e l to the contact. F l o w banded m i c r o g r a n i t e intrudes both granite and gabbro along the contact, and both r o c k s
have also been intruded by two s w a r m s of m i c r o d i o r i t e and dolerite dykes - an e a r l i e r
s w a r m trending at 290° and a later at 015°. The dykes and country r o c k s have been
s e v e r e l y epidotized in zones up to 6 inches wide along the contacts. Numerous pegmatite
v e i n s intrude both the granite and gabbro.
27
The m a s s i v e white to g r e y c h l o r i t i z e d granite, which c r o p s out at s e v e r a l places
at Bowen, i s b e l i e v e d to underlie much of the town. M a s s i v e leucoadamellite c r o p s out
on the eastern side of a low hill on the northern outskirts of Bowen (half a m i l e north of
the Bowen Shire Council Rugby Football ground), just within the Bowen Sheet area. It
contains phenocrysts of strongly zoned o l i g o c l a s e surrounded by c o a r s e m i c r o c l i n e
antiperthite which i s inter grown with quartz in p l a c e s . The granite intrudes intermediate
volcanics which a r e probably L o w e r P e r m i a n in a g e . A s at Mount Luce, the granite i s
intruded by two s w a r m s of intermediate to basic dykes; the e a r l i e r trends northwest
and the later has a northerly trend.
A g e and Relationships
The acid plutonic r o c k s g e n e r a l l y intrude the basic to intermediate rocks ( C - P d ) .
The only younger intrusions a r e abundant dykes and scattered epizonal granites ( P - M g ) .
No isotopic ages a r e available f o r the acid plutonic rocks ( C - P g ) in the A y r Sheet
a r e a . In the w e s t e r n part of the Bowen Sheet area the extensive granite which intrudes
Upper Carboniferous v o l c a n i c s has been dated isotopically at about 285 m . y . by the K / A r
method (uppermost Carboniferous). A few m i l e s north of the known l i m i t of these Upper
Carboniferous granites is a group of oval epizonal stocks f r o m which a single isotopic
age of 270 m . y . ( L o w e r P e r m i a n ) has been obtained. In the north-central part of the Bowen
Sheet area, deeply weathered and altered granitic r o c k s a r e o v e r l a i n nonconformably
by the L i z z i e C r e e k V o l c a n i c s ( L o w e r P e r m i a n ) , and f r o m their fresher parts two isotopic
a g e s of 270 m . y . have been obtained by the K / A r method. H o w e v e r , detailed mapping is
r e q u i r e d to determine whether the fresh and weathered r o c k s a r e part of the same body.
Granite at Bowen intrudes volcanics mapped with the L o w e r P e r m i a n C a r m i l a Beds just
south of the A y r Sheet a r e a . The Thunderbolt Granite near C o l l i n s v i l l e (Bowen Sheet a r e a )
has yielded isotopic ages which a v e r a g e 265 to 270 m . y , ; it i s believed to be younger
than the L i z z i e C r e e k V o l c a n i c s . Until g r e a t e r resolution can be obtained by further age
determinations and detailed mapping it s e e m s best to r e g a r d the granites grouped in this
unit ( C - P g ) as Upper Carboniferous to L o w e r P e r m i a n in a g e .
ACID VOLCANIC P L U G (C-Ph)
Mount Louisa i s a p l u g - l i k e mass of intrusive rhyolite and related rocks 20 m i l e s
south-southwest of Home H i l l . It f o r m s a high steep hill with cliffs in places near its
summit.
Mount Louisa consists mainly of strongly flow-banded rhyolite and f e l s i t e , with
subordinate trachyte and tr achy andesite. The rocks a r e g e n e r a l l y slightly porphyritic,
g r e e n to white, and highly jointed; some of them a r e v i t r i c . The flow banding i s usually steep
and commonly contorted. The cliff faces exhibit strong v e r t i c a l joints. The plug is intruded
by dykes of m i c r o d i o r i t e and m i c r o a d a m e l l i t e , s i m i l a r to those to the east in the diorite
and granodiorite ( C - P d ) . Dykes of f e l s i t e and trachyandesite, s i m i l a r to parts of the
Mount Louisa plug, intrude the adamellite ( C - P g ) to the east.
The acid intrusives a r e composed of m i c r o l i t e s of feldspar, ironstained clay, and
quartz. Quartz probably f o r m s a high proportion of the groundmass. Small patches of
penninite and epidote a r e scattered through the rock. Granular quartz occurs in i r r e g u l a r
a g g r e g a t e s and the feldspar phenocrysts a r e completely altered to clay and epidote.
The Mount Louisa plug probably intrudes the Carboniferous to P e r m i a n granitic
r o c k s ( C - P g ) . The plug i s intruded by m i c r o d i o r i t e dykes.
INTERMEDIATE T O ACID VOLCANICS ( C - P v )
Intermediate and acid v o l c a n i c s , c o r r e l a t e d with Carboniferous to P e r m i a n volcanics
near T o w n s v i l l e , f o r m the foothills of Saddle Mountain and Mount Elliot and the northern
28
part of the
Cape Cleveland peninsula.
The maximum
thickness at Cape Cleveland i s
4000 feet.
Topography
At Cape Cleveland the volcanics f o r m a narrow steep headland r i s i n g in p l a c e s to
300 feet above sea l e v e l . A c r o s s the granite contact to the south, the headland b e c o m e s
higher and broadens to f o r m the main mass of the Cape Cleveland peninsula. West of Giru,
the v o l c a n i c s f o r m a fringe of foothills east and southeast of Saddle Mountain and Mount
Elliot. Uneven hills of volcanics, r i s i n g to 800 feet above sea l e v e l , extend for s e v e r a l
m i l e s southeast of Mount Elliot.
Lithology
W e l l bedded dark to pale brownish g r e y acid welded c r y s t a l tuff crops out at Cape
Cleveland; one specimen has a dacitic composition. Some thin flows of acid lava w e r e
also noted.
In the southeastern foothills of Saddle Mountain, massive dark greenish g r e y andesite
a g g l o m e r a t e and lapilli tuff, with s m a l l disseminated cubes of p y r i t e , predominate. P a l e
pinkish brown feldspar porphyry c r o p s out on the western side of the road due east of the
summit of Saddle Mountain.
M a s s i v e porphyritic greenish g r e y andesite or dacite and some dark blue finely
porphyritic andesite crop out t h r e e - q u a r t e r s of a m i l e southwest of w h e r e the Bruce
Highway c r o s s e s P a l m C r e e k .
Southeast of Mount Elliot, in the W a l k e r s C r e e k / B l a c k Gully district, purple and
greenish purple porphyritic and aphanitic andesites(?) c r o p out. They a r e commonly
amygdaloidal and strongly epidotized. The abundant boulders of fine-grained basic r o c k s
a r e probably d e r i v e d f r o m dykes.
Structure and Thickness
A t Cape Cleveland the v o l c a n i c s a r e w e l l bedded, with a f a i r l y constant dip to the
southeast. Northwesterly lineaments, probably faults, appear in p l a c e s on the a i r photographs. Dips of 50 w e r e r e c o r d e d at two points about a m i l e apart. If there is no
repetition of the sequence by faulting, the p r e s e r v e d thickness is about 4000 feet.
The thickness and structure of the volcanics e l s e w h e r e a r e unknown. In a road cutting
on the main road to the west of Black Gully, the andesite appears to dip northwest at
5 , and the andesite half a m i l e southwest of w h e r e the Bruce Highway c r o s s e s P a l m
Creek s e e m s to dip w e s t at a moderate angle. No structure was v i s i b l e in the other out­
crops.
A g e and Relationships
The volcanic r o c k s around Mount Elliot and Saddle Mountain are continuous with
s i m i l a r r o c k s near Townsville which have been dated as late Carboniferous to P e r m i a n
because they contain sedimentary interbeds with Glossopteris sp. (Wyatt et al.,1970a).
The volcanics at Cape Cleveland, h o w e v e r , are somewhat different in lithology f r o m the
volcanics near T o w n s v i l l e . They a r e included in this group f o r lack of evidence that they
a r e of any other a g e . They a r e intruded by the Cape Cleveland adamellite ( P - M g ) .
29
P E R M I A N T O MESOZOIC
(TABLE
VOLCANICS
1)
(P-Mv)
N a r e s R o c k i s an i s l e t about 200 feet square which r i s e s 15 to 20 feet out of the sea
3 m i l e s south of Holbourne Island. The rock consists of strongly jointed dark g r e y hornfelsed tuff o r tuffaceous sediments. It is mainly uniformly dark g r e y , but in p l a c e s i s
finely banded and light g r e y . The bands dip v e r t i c a l l y and strike northwest; they a r e
slumped in p l a c e s and probably represent bedding. The r o c k s do not part along the bands.
The hornfels contains 10 to 20 percent angular to subangular grains of quartz and
poikiloblastic albite, which suggests that it is a r e c r y s t a l l i z e d sediment. The grains a r e
enclosed in a m a t r i x of poikiloblastic to granophyric intergrowths of quartz and alkali
feldspar.
Some v o l c a n i c s in the P r o s e r p i n e Sheet area have been found to be Cretaceous, and
N a r e s Rock could possibly be of the same age.
G R A N I T E S , E T C . ( P - M g and P - M d )
Some granitic plutons ( P - M g ) in the A y r Sheet area a r e mapped c o l l e c t i v e l y as P e r m i a n
to M e s o z o i c . The plutons a r e typically subcircular in plan and r i s e abruptly f r o m the
coastal plain as high rugged r a n g e s . Leucocratic adamellites predominate o v e r true
granites. R a r e s m a l l outcrops of d i o r i t e and d o l e r i t e ( P - M d ) occur around the margins
of the acid stocks, and on Holbourne Island. The p r e s e n c e of net-veined c o m p l e x e s in
places suggests that the m o r e basic rocks a r e genetically related to the granitic r o c k s .
The only known younger intrusive r o c k s are r a r e acid and m i c r o d i o r i t e dykes of unknown
age.*
Topography
Mount E l l i o t , Saddle Mountain, Gloucester Island, and the Cape Cleveland and Cape
Upstart peninsulas a r e mantled by dense scrub. Mount Elliot r i s e s abruptly to about
4000 feet above sea l e v e l and dominates the landscape in the western part of the Sheet
a r e a . Saddle Mountain and the Cape Upstart peninsula r i s e 2800 feet and 2500 feet r e s ­
p e c t i v e l y ; Gloucester Island and the Cape Cleveland peninsula reach just under 2000
feet above sea l e v e l . The granites at Cape Edgecumbe and in the saddle between Mount
L i t t l e and Sprole Castle have also been mapped with this group. Cape Edgecumbe i s
the northern tip of a rocky headland which consists l a r g e l y of bare outcrops and tors of
granite. The granite northeast of Mount Louisa f o r m s rough bouldery h i l l s .
Lithology
The adamellite ( P - M g ) on the southern margin of the Cape Cleveland peninsula i s a
c o a r s e m a s s i v e white and pink porphyritic biotite a d a m e l l i t e , containing a little horn­
blende. The r o c k i s composed mainly of quartz, perthite, and plagioclase which i s
diffusely zoned f r o m andesine to albite. The a c c e s s o r i e s a r e sphene, magnetite, and
apatite.
One and a half m i l e s southeast of Cape Cleveland, thick granophyre dykes, which a r e
probably offshoots of the adamellite, intrude the volcanics ( C - P v ) .
The southwestern margin of Saddle Mountain, which l i e s within the T o w n s v i l l e Sheet
area, i s c o m p o s e d of leucogranite and adamellite. The leucogranite i s a m a s s i v e r e d
*
Recent K / A r isotopic dating of biotites f r o m the Mount Elliot and Cape Cleveland
granite stocks has shown them to be L o w e r P e r m i a n (see Appendix 5 ) .
30
medium-grained rock which contains no plagioclase. The groundmass is locally granophyric, and some muscovite occurs in places. The r a r e mafic minerals have been
entirely epidotized and chloritized. One and a half m i l e s to the southeast the rock grades
into adamellite. Some cobbles of fine-grained quartz-hornblende gabbro w e r e found in a
c r e e k near the southern margin of Saddle Mountain.
Feltham Cone and the smaller inselbergs nearby have a similar air-photo pattern
to that of Saddle Mountain.
The granite at Mount Elliot in the Townsville Sheet area is a massive pink-brown
c o a r s e porphyritic biotite-hornblende granite ( P - M g ) . It is composed of potash feldspar,
zoned plagioclase (andesine to albite), green hornblende, biotite, magnetite, apatite,
z i r c o n , epidote, and allanite.
The stock north of The Gap, 5 m i l e s east-northeast of Mount Louisa, consists of
massive medium-grained biotite adamellite. No dykes w e r e seen.
F i g . 9:
Vertical air-photograph of Cape Upstart peninsula, an epizonal stock or
ring complex of Permian or Mesozoic age. Approximate scale, 1:100,000.
Reproduced by courtesy of Division of National Mapping, Department of
National Development.
Most of the Cape Upstart peninsula consists of a subcircular stock of adamellite
( P - M g ) with some low hills at its southern end ( F i g . 9 ) . The southeastern margin of the
stock consists of massive leucocratic pinkish brown porphyritic medium-grained hornblende-biotite adamellite; it i s composed of oligoclase-andesine (40%), potash feldspar
(30%), and a little biotite, hornblende, and iron oxide. Massive coarse leucocratic biotite
adamellite, containing r e c r y s t a l l i z e d quartz, chloritized biotite, and microfractured
31
oligoclase, crops out on the northern coast, and possibly represents a remnant of the
country rock which surrounded the main stock.
Small outcrops of diorite, m i c r o d i o r i t e , and quartz diorite ( P - M d ) crop out in places
around the eastern and northern margins of the Cape Upstart stock. T h e i r s i z e has been
exaggerated on the geological map.
Two m i l e s north-northeast of The Cape homestead there is an excellent exposure
of a net-veined complex of basic to intermediate intrusive rocks ( P - M d ) in intimate
association with granite ( P - M g ) . The melanocratic rocks form a s l i v e r , s e v e r a l hundred
yards long and 30 to 50 feet wide, along the margin of the granite. The granite contains
numerous basic to intermediate xenoliths, some of which show orbicular structures ( P . J .
Stephenson, p e r s . c o m m . ) . The melanocratic rocks range from augite-diorite to p o r ­
phyritic biotite m i c r o d i o r i t e .
Quartz d i o r i t e , biotite-quartz d i o r i t e , and biotite diorite also crop out along the margin
of the adamellite in a bay on the northeastern coast of the Cape Upstart peninsula. The
adamellite veins the d i o r i t e s , but in places, the d i o r i t e becomes finer in grain near the
contact, and has a crude foliation which may be a type of flow structure. Dioritic xenoliths
with crenulate margins occur in the adamellite in p l a c e s . Thin horizontal veins of
adamellite p e r m e a t e the diorite and meandering anastomosing pegmatitic apophyses
commonly extend upwards from them. Similar features have been described by Blake
et al. (1965), where basic and acid magma have been intruded simultaneously, or where
basic magma has intruded acid rock. In the first c a s e , the basic magma is chilled against
the acid magma in which it is trapped, and may c r y s t a l l i z e as xenoliths with crenulate
margins; in the second case, the basic magma has intruded and remelted the granitic
rock, which has then 'back-veined' the basic rock.
The adamellite ( P - M g ) forming the saddle between Sprole Castle and Mount Little
is a northerly continuation of the intrusion at Mount P r i n g in the Bowen Sheet area. The
Mount P r i n g mass consists of coarse inequigranular m a s s i v e white biotite adamellite
composed of perthite, zoned o l i g o c l a s e , quartz, and biotite, with a little z i r c o n , apatite,
sphene, and euhedral allanite.
The Cape Edgecumbe promontory consists of m a s s i v e pink medium-grained drusy
leucocratic alkali granite composed of perthite (40%), quartz (40%), albite (15-20%),
and some biotite and z i r c o n . Euhedral quartz c r y s t a l s occur in r a r e druses.
The southeastern tip of Holbourne Island consists of c o a r s e , medium, and fine-grained
intermediate and basic plutonic rocks ( P - M d ) . Thick melanocratic and paler l a y e r s dip
at a low angle to the north-northwest. The rocks include leucocratic hornblende gabbro,
augite d i o r i t e , and diorite; a m o r e leucocratic rock which is locally pegmatitic, occurs
as horizontal veins f r o m which apophyses extend upwards, as at Cape Upstart. Some of
the veins contain feldspar, hornblende, quartz, and epidote.
The granophyre and hornblende-quartz alkali syenite ( P - M g ) on the northeast coast
of Holbourne Island are faulted against the d i o r i t e s ( P - M d ) . The granophyre c l o s e to the
fault is strongly sheared and intruded by abundant basic to intermediate dykes. The
hornblende-quartz alkali syenite c r o p s out 200 yards farther northwest. The northwestern
tip of the island consists of leucogranite intruded by a swarm of dark dykes.
Middle Island also consists of leucocratic granitic r o c k s . A c o a r s e biotite alkali
rhyolite porphyry c r o p s out on the northwest coast; it is intruded by numerous dykes of
s i m i l a r porphyry, up to 20 feet thick, and by thinner dykes of dolerite or m i c r o d i o r i t e .
32
F i g . 10:
F i g . 11:
Dolerite or microdiorite dykes intruding the complex marginal zone of the
Gloucester Island leucogranite stock ( P e r m i a n or M e s o z o i c ) . The stock f o r m s
the main mass of the island, but large marginal s l i v e r s of dark dioritic rocks,
banded in places, crop out along the northeast shore. Photograph by J.E.
Zawartko.
Jointing in leucogranite, northeast shore of Gloucester Island. A complex zone
of mixed dioritic and granitic rocks is v i s i b l e on the right of the picture.
Photograph by J.E. Zawartko.
33
Gloucester Island consists mainly of uniform medium to fine-grained leucocratic
biotite granite
( P - M g ) . Dioritic s l i v e r s ( P - M d ) crop out at sea l e v e l in places ( F i g s 10,
11).
At the e x t r e m e northern tip of the island a net-veined complex ( F i g s 12, 13), s i m i l a r
to that on the Cape Upstart peninsula, is well exposed at sea l e v e l . The oldest rocks in the
complex are hard siliceous mottled pale g r e y , pink, and green hornfelsed volcanics
which occur as xenoliths, up to 6 feet a c r o s s , in diorite and granodiorite. The volcanics
a r e commonly banded, and in places amygdaloidal. Xenoliths and blocks of diorite (which
themselves contain xenoliths of the volcanic r o c k s ) occur in granodiorite, and the xenoliths
a r e cut by an i r r e g u l a r permeating network of granodiorite v e i n s . The leucocratic granite,
which appears to f o r m most of the island, cuts across the net-veined complex. The contact
is r e c t i l i n e a r , but apophyses are present in p l a c e s . Finally, the complex was intruded by
basic to intermediate dykes.
Structure
The Mount Elliot, Saddle Mountain, and Cape Upstart plutons are well defined subcircular stocks. The outline of the Cape Cleveland mass is i r r e g u l a r but roughly equidimensional and may be circular at depth. The granite outcrops between Sprole Castle
and Mount L i t t l e represent the partly unroofed northern extension of a circular stock
which f o r m s Mount P r i n g in the Bowen Sheet area. A l l these granites are evidently highl e v e l epizonal intrusions, and further mapping may show that some of them ( e . g . , Cape
Upstart) are ring c o m p l e x e s .
The deep straight V-shaped v a l l e y s , which a r e common in most of the granites, are
almost certainly the result of erosion along faults. The faults have a p r e f e r r e d north­
w e s t e r l y trend, and a r e therefore probably the result of regional rather than local s t r e s s e s .
A g e and Relationships
Although these granitic intrusions are not n e c e s s a r i l y all of the same age, they are
c o l l e c t i v e l y r e g a r d e d as the youngest in the Sheet a r e a . The Cape Cleveland peninsula
adamellite intrudes volcanics which may be equivalent to the Upper Carboniferous to
P e r m i a n volcanics near T o w n s v i l l e . It is intruded by r a r e m i c r o d i o r i t e dykes. The Saddle
Mountain and Mount Elliot stocks both intrude volcanics which are continuous with the
Upper Carboniferous to Permian volcanics near T o w n s v i l l e . T h e granite at Cape Edgecumbe
is probably continuous at depth with the granite at North Head (within the Bowen Sheet
a r e a ) , which intrudes abundant P e r m i a n m i c r o d i o r i t e and dolerite dykes. Only r a r e acid
dykes a r e known in the granite at Cape Edgecumbe. The Cape Upstart adamellite and the
Gloucester Island mass are included with the group because they are probably epizonal
intrusions, and because they are only r a r e l y intruded by dykes.
The age of the few dykes which intrude the granites and adamellites is unknown. The
granites in the Whitsunday and Cumberland Islands a r e regarded as Cretaceous (Clarke
et a l . , 1968, unpubl., and in p r e p . ) . A l a r g e L o w e r Cretaceous granite has been delineated
recently by mapping and isotopic dating in the northeastern part of the Bowen Sheet area
(Paine et al., in prep.; see also Webb & McDougall, 1964). This suggests that some of the
youngest granites in the A y r Sheet area, e s p e c i a l l y in the east, may also be Cretaceous.
DYKES
Dykes with a wide range in composition a r e common in all rock units except the
younger granites. M i c r o d i o r i t e and d o l e r i t e dykes are the most widespread. They a r e
commonly between 2 and 5 feet thick, but range up to 20 feet. There a r e no known e a r l y
P a l a e o z o i c dykes; the vast majority are believed to be late Palaeozoic (probably P e r m i a n ) ,
but some a r e probably M e s o z o i c . Epidotization is widespread and typical of the dark dykes.
34
F i g . 12:
Leucogranite (left) intruding net-veined complex, northern point of Gloucester
Island. The leucogranite is probably magmatically related to the net-veined
complex. The resistant stack of light-coloured rock to the right of the figures
is a pipe-like body of leucogranite which i s probably an offshoot of the main
m a s s . Photograph by J.E. Zawartko.
F i g . 13:
Close-up of part of the net-veined complex in Figure 12. Photograph by J.E.
Zawartko.
35
The acid f e l s i t e , microgranite, granophyre, and porphyry dykes can be related in places
to the P e r m i a n to Mesozoic igneous centres ( P - M g ) , near some of which they are v e r y
abundant. They are usually thicker than the basic to intermediate dykes. In the central
and northwestern parts of the Sheet area, most of the dykes trend between north-north­
w e s t and west-northwest, except for some east-northeasterly dykes in the Inkerman Shear
Zone. The dykes in the southwest and east appear to have no p r e f e r r e d orientation.
Southeastern Part of Sheet A r e a
Both the intermediate to basic and the acid dykes a r e well exposed in and around the
town of Bowen, which l i e s just south of the Sheet a r e a . Easily accessible outcrops are
found on North Head, in an old quarry west of Magazine C r e e k , and on the eastern slopes
of a low hill just west of the turn-off to Flagstaff H i l l . The outcrops r e v e a l the following
chronological sequence of events: (1) acid and intermediate volcanics (probably Lower
P e r m i a n ) , (2) adamellite ( C - P g ) , (3) northwesterly swarm of basic to intermediate dykes,
(4) northerly s w a r m of basic to intermediate dykes, (5) leucogranite ( P - M g ) , and (6)
northerly microgranite dykes.
Some of the basic to intermediate dykes at Bowen have been albitized, and the mafic
m i n e r a l s are almost invariably uralitized, epidotized, or c h l o r i t i z e d . The dykes are gen­
e r a l l y fine-grained and equigranular, but some contain plagioclase phenocrysts. In the
dykes which have not been albitized the plagioclase ranges from labradorite to andesine.
Some contain p r i m a r y hornblende, with or without quartz, and no pyroxene. They include
d o l e r i t e and m i c r o d i o r i t e and some augite m i c r o d i o r i t e and hornblende d o l e r i t e , some of
which contain quartz. T h e r e is no significant difference in composition between north­
w e s t e r l y and northerly dykes.
The basic to intermediate dykes near Bowen a r e intersected by thicker m i c r o g r a n i t e
dykes, some of which are probably offshoots f r o m , and others intrude, the leucogranite
( P - M g ) of Cape Edgecumbe.
An albitized dolerite dyke intrudes diorite at the eastern end of Holbourne Island,
and a s w a r m of albitized m i c r o d i o r i t e dykes intrudes the granite ( C - P g , see p . 27) at
Mount Carew west of Salisbury Plains homestead.
A weakly banded microtonalite dyke intrudes granite ( C - P g ) 1 m i l e east of Salisbury
Plains homestead. It is composed of phenocrysts of andesine set in a groundmass of horn­
blende, p l a g i o c l a s e , and appreciable amounts of interstitial quartz and alkali feldspar.
A different type of microtonalite dyke intrudes the granite ( C - P g ) 4 m i l e s west-northwest
of The Cape homestead. It contains 60 percent of zoned plagioclase phenocrysts ( A n g - A n g g )
set in a groundmass of quartz (15%), hornblende (10%), and biotite (10%).
0
The granite ( P - M g ) l j m i l e s east of Cape Upstart is intruded by a multiple dyke of
m i c r o d i o r i t e and f e l s i t e . The margins of the dyke consist of albitized hornblende m i c r o ­
d i o r i t e and the c o r e is a thin lenticular intrusion of porphyritic f e l s i t e . A rhyolite dyke
intrudes the granite ( P - M g ) on the northeastern coast of the Cape Upstart peninsula
( F i g . 14). It is composed of phenocrysts of oligoclase-andesine, potash feldspar, embayed
quartz, and epidotized hornblende set in a groundmass of alkali feldspar laths, inter­
stitial quartz, some plagioclase, epidote, and acicular apatite.
36
F i g . 14:
F i v e - f o o t porphyritic rhyolite dyke intruding adamellite ( P - M g ) on the north­
eastern coast of the Cape Upstart peninsula.
Central Part of Sheet A r e a
P a r t l y amphibolitized dolerite dykes, composed of calcic labradorite and augite,
intrude the granite ( C - P g ) southwest of Kellys Mount.
Dyke swarms intrude the intermediate to basic plutonic rocks ( C - P d ) . They include
two l a r g e north-northwesterly swarms and an east-northeasterly swarm along the Inkerman
Shear Zone. The dykes include rhyolite, rhyodacite, microgranite, microadamellite,
m i c r o g r a n o d i o r i t e , acid porphyries, and m i c r o d i o r i t e . The microgranodiorite dykes w e r e
probably intruded soon after the emplacement of the granodiorite and diorite country
rock; they are cut by the acid dykes. Fine-grained dark green microdiorite dykes, believed
to be no older than late P a l a e o z o i c , are common in the central part of the Sheet area;
at least three intrusive episodes have been recognized at The Rocks in the Burdekin
River.
Microgranite, microadamellite, and rhyodacite, with or without phenocrysts, are next
in abundance.Dacite is comparatively r a r e . Rhyolite dykes w e r e found near Beaks Mountain
and Mount Louisa. At Beaks Mountain they appear to be related to Edinburgh Castle
(an intrusive centre 4 m i l e s south of the margin of the Sheet a r e a ) , which r e s e m b l e s
the Upper Permian or L o w e r T r i a s s i c plugs between the Bogie and Bowen R i v e r s . One
of the rhyolite dykes contains concentric spheroidal flow structures, compressed in the
plane of the dyke.
The width of the dykes generally
A m i c r o a d a m e l l i t e dyke up to 300
junction with Landers C r e e k . The
jointed. The jointing is probably due
Rhyolite dykes associated
ranges from 1 to 10 feet, but some are much w i d e r .
feet wide crops out in the Burdekin R i v e r , near its
dyke has a weak east-west foliation and is closely
to the M i l l a r o o Fault, which is close by to the west.
with the Mount Louisa rhyolite plug intrude adamellite
( C - P g ) east of the plug.
37
T A B L E 2.
Rock Unit
and
or Epoch
Map Symbol
(Qm)
Lithology
Mud, silt; minor salt
CAINOZOIC S T R A T I G R A P H Y
Topography
Relationships
Littoral flats
Superficial; c o m p l e ­
and pans
mentary to coastal dunes
Structural/Depositional
Environment
Remarks
Deposited in calm water
Intermittent
deposition
from high tides and floods continuing in l e e of c o a s t ­
al dunes
(Or)
Sand; some interbedded
silt
Low linear
dunes up to
25 ft high
Superficial
Ancient and present shore Includes some old blow­
dunes; perhaps some
out dunes; local concen­
submerged offshore bars trations of heavy minerals
(Qu)
Scree, g r a v e l , sand;
Scree slopes
Superficial; m e r g e s with
alluvium ( C z a ) and
residual soil ( C z s )
Outwash fans, essentially Dissected
by
present
stable at present; t h e r e ­ streams; probably P l e i s ­
fore thought to have been tocene
deposited in a wetter
climate
Flat to gent­
ly undulating
Superficial; m e r g e s with
residual soil ( C z s ) and
outwash fans (Qu)
L e v e e s , floor plains, and
deltas
semiconsolidated in
places
(Cza)
Sand, silt, mud, g r a v e l ;
semiconsolidated in
places
(Czs)
Soil, sand, rubble; semi- Gently un­
consolidated in places
dulating
Generally less than 10 ft
Superficial; mainly close­ Mainly residual soil
ly related to bedrock
developed on deeply weath-(thick
e r e d granitic rocks;
some colluvium
(Czc)
White powdery material
r i c h in calcium c a r b ­
onate
Isolated deposits interfingering with residual
soil ( C z s )
Flat
Superficial; derived
from weathered c o a r s e
diorite
Up to 270 ft thick in Bur­
dekin R Delta; e l s e w h e r e
much thinner;mostly Qua­
ternary
T w o small isolated dep­
osits; thickness of 50 ft
claimed
by
lessees;
worked for local a g r i ­
cultural use
Western Part of Sheet A r e a
F e l s i t e , quartz porphyry, and feldspar porphyry dykes intrude the low-grade metamorphics ( P z u ) southwest of Mount Woodhouse. Leucocratic microgranite dykes intrude
sheared volcanics (Cuv) at the northeastern end of the Mount Dalrymple range. Four m i l e s
west of Mount Benjonney a complex swarm of blue-grey feldspar-hornblende porphyry,
feldspar-hornblende-quartz porphyry, andesite, and aplitic quartz porphyry dykes intrudes
the Ravenswood Granodiorite; the swarm i s truncated by an arcuate body of microgranite
( C - P g ) . Some of the feldspar-hornblende porphyry dykes intrude dark-blue andesite
dykes, and both are cut by flow-banded m i c r o d i o r i t e dykes.
A swarm of flow-banded felsite, andesite, and microdiorite dykes intrudes the
granodiorite in the Burdekin R i v e r east of C l a r e . The dykes are parallel, and their
r e l a t i v e ages are unknown. The swarm is parallel to the north-northwesterly swarm in the
Stokes Range, 6 m i l e s to the east.
Two m i l e s southeast of the confluence of Deep Creek and the Burdekin River westtrending m i c r o d i o r i t e dykes intrude granite r o c k s . They are cut by thin tourmaline p e g ­
matite. Dykes of red granite and biotite adamellite also intrude the plutonic rocks, but
their relationship to the m i c r o d i o r i t e and pegmatite is unknown.
Northerly trending pyroxene m i c r o d i o r i t e dykes containing oligoclase-andesine intrude
the porphyritic microgranite ( C - P g ) in the northeastern foothills of Major Creek Mount­
ain; they are s e v e r e l y epidotized. Similar epidotized dykes, including some d o l e r i t e s ,
are abundant in the Upper Carboniferous to Permian Volcanics ( C - P v ) . They are generally
absent in the younger granites ( P - M g ) , but strongly altered m i c r o d i o r i t e (?) dykes intrude
granite ( P - M g ) near Cape Ferguson.
CAINOZOIC
(Table 2)
Earth L i m e ( C z c )
The small superficial deposits of unconsolidated white 'earth l i m e ' occur 10 m i l e s
to the southwest and 8 miles to the south of Inkerman homestead. The earth l i m e deposits
are c o v e r e d by several feet of soil, and w e r e probably formed by leaching and concen­
tration of calcium carbonate in the dioritic r o c k s . In places the colluvium o v e r l y i n g the
diorite has also been calcified. Connah (1958) regarded the deposits as the products of
Quaternary mound springs (see p . 45 ) .
Residual and Colluvial Soil ( C z a )
Residual and colluvial soils form a discontinuous broad zone between the hills and
the coastal plain. The s o i l - c o v e r e d areas are higher than the coastal plain; they are
gently undulating and are interrupted by a few low rounded hills. Scattered cobbles and
angular blocks of weathered rock are found in a few areas, and patches of g r a v e l are not
uncommon at shallow depth in creek sections. The soils range from pale sand to black
loam, depending on the parent rocks, and are at least 10 feet thick in p l a c e s . They are
probably l a r g e l y residual, but colluvial material i s also present.
Alluvial and Deltaic Deposits ( C z a )
Most of the Sheet area i s underlain by superficial Cainozoic alluvial and deltaic
sediments. They a r e believed to be mainly Quaternary, but some may be T e r t i a r y .
39
Near the mouth of the Burdekin R i v e r the entire sugar crop on the Burdekin R i v e r
Delta (valued at about 830 m . in 1963, Wiebenga et a l . , 1966, unpubl.) depends on under­
ground water pumped from the Quaternary sediments. The sediments w e r e studied in
1964 by a group of geologists f r o m Louisiana State University and detailed geophysical
s u r v e y s w e r e c a r r i e d out by the Bureau of Mineral Resources in 1962-65.
Many w a t e r b o r e s have been d r i l l e d in the delta. Those which reached bedrock are
plotted on the map in Appendix 4. The maximum thickness of the sediments recorded in
a bore is 271 feet near Plantation C r e e k , 5 m i l e s northeast of the centre of A y r , but
s e i s m i c work has indicated a thickness of at least 500 feet near Lynchs Beach (Wiebenga
et al., 1966, unpubl.).
Some colluvial and outwash deposits which underlie gently sloping country c l o s e
to the hills and ranges have been mapped in places with this unit. The deposits m e r g e
imperceptibly with the alluvium laid down in the f l a t - l y i n g country by overflow from the
l a r g e r streams during floods. Both the colluvium and alluvium m e r g e and interfinger with
the deltaic deposits.
The sediments of the Burdekin R i v e r Delta consist of interbedded lenses of sand,
silt, and g r a v e l , with lenses of mud near the coast. Recent erosion of the Quaternary
deposits, due to slight coastal e m e r g e n c e , can be seen at Lynchs Beach ( A l v a ) , where a
10 foot cliff has been cut in interbedded deltaic sand and mud ( F i g . 15). A C ^ age of
3870+50 y e a r s b.p. was obtained on carbonized wood embedded in the sand near the top
of this cliff (Institute of Nuclear Sciences, DSIR, New Zealand), which sets a maximum
age limit on both the uppermost sediments and the e m e r g e n c e .
F i g . 15:
Quaternary deltaic sediments of the Burdekin R i v e r Delta at Lynchs Beach
( A l v a ) , 10 m i l e s northeast of A y r . The sediments consist of fine sand and
interbedded lenses of silty mud, and a r e now being eroded owing to a recent
slight fall in sea l e v e l .
40
QUATERNARY
Outwash and Scree (Qu)
W e d g e - l i k e deposits of angular rubble and sand form an outwash apron around the
Mount Dalrymple range. At the foot of the range the rubble is consolidated s c r e e , but
the finer-grained material farther away is unconsolidated. The apron is up to 2 j m i l e s
wide; it thins gradually outwards from the range and m e r g e s with the alluvium. The
maximum thickness of rubble is estimated at about 50 feet. A crude radial system of small
s t r e a m s dissects the outwash apron. The rubble is an accumulation of angular fragments
of fine-grained acid volcanics up to 2 feet in diameter.
Kellys Mount, and the two hills 3 miles southwest, are surrounded by a similar
outwash apron.
Thick tongues of s c r e e , which coalesce to form outwash fans, occur around the slopes
of Mount Roundback and Mount Little in the southeast.
The
scree
and outwash deposits are
now being dissected. They are the products
of a f o r m e r period of active denudation, probably a pluvial period during the P l e i s t o c e n e .
Coastal Sand Dunes ( Q r )
Sand dunes, some of them s e v e r a l m i l e s inland, occur along much of the coast. They
consist of material deposited by wave action, and later redistributed by winds. Most are
fixed by vegetation, but some of the present-day active beach dunes and offshore sand
bars are included in this unit. The highestdunes ( e . g . , that extending southeast from The
Cape homestead) are about 25 feet high, but most of them are less than 15 feet above sea
level.
The dunes indicate f o r m e r strandlines. Their distribution and trends are controlled
by the predominant northwesterly longshore currents. In places, they have advanced
out to sea by growth at their distal ends and bridged the gaps between f o r m e r islands
(Cape Cleveland and Cape Upstart peninsula) and the mainland; extensive mud flats have
been developed in their l e e . Cape Bowling Green is a complex of dunes which is currently
growing to the northwest by the addition of material from the Burdekin R i v e r .
Thin remnants of pale brown hard cemented beach detritus ('beach r o c k ' ) occur
between t i d e - m a r k s along the beaches as, for example, at Dingo Beach. They are too
small to map.
Some of the beach sands along the coast between Bowen and Cape Bowling Green
contain high concentrations of heavy minerals. T h r e e samples of the sands have been
analysed and the results are tabulated in Appendices 2 and 3. A body of heavy mineral
sand at Dingo Beach is about 3000 feet long, 30 feet wide, and about 18 inches thick in
the centre. The analysed sample contains 87 percent iron and titanium oxides (see p .
).
The heavy minerals have been derived from the gabbro at Abbot Point.
A pumice beach occurs on the northeastern side of Cape Cleveland.
Coastal Mud Flats (Qm)
Much of the low-lying country fringing the coast consists of mud flats which are
p e r i o d i c a l l y inundated by high tides and floods. In places the mud flats are c o v e r e d by
a thin l a y e r of salt. The flats are most extensively developed in the l e e of the large
ancient coastal dunes, as for example at Abbot Point, Cape Upstart, and Cape Bowling
Green.
41
I4r JO;
*roo-
Geological boundary
Fault, broken where approximate
Sftaor zona
-<**» Strike and dip o t strata
Strike and dip of foliation
X
Dyke
is MILES
F i g . 16:
STRUCTURE
The major structural units are outlined in F i g u r e 16.
The Inkerman Shear Zone is at least 2 m i l e s wide at its widest part. The rocks within
it have been intensely metamorphosed by shearing and r e c r y s t a l l i z a t i o n , and in places
by metasomatic activity (with which some traces of copper mineralization a r e associated).
In the Townsville Sheet area, just west of Horse Camp H i l l , phyllonite, mylonite, schist,
and gneiss have been developed from granite and granodiorite within the s i m i l a r A l e x
Hill Shear Zone, which l i e s on strike with the w e s t e r l y projection of the Inkerman Shear
Zone. Outcrops are not abundant in the intervening area, but the existing outcrops show
no evidence of shearing along this east-northeasterly zone. The foliation within the shear
zone is v e r t i c a l , but the direction of movement is unknown.
The Woodhouse Fault, in the southwest, can be traced for 16 m i l e s within the A y r
Sheet area. It continues northwest into the Townsville Sheet area as a fault system extend­
ing west-northwest up the v a l l e y of the Reid R i v e r . The total length of the fault is about
65 m i l e s . In the A y r Sheet area, the Woodhouse Fault in the metamorphic rocks (Pzu) is
marked by dip r e v e r s a l s , fault breccia, and zones of silicification and shearing. The
distribution of the Upper Carboniferous volcanics (Cuv) suggests that the Woodhouse
Fault may have partly controlled their extrusion. The major component of movement is
apparently v e r t i c a l . In the T o w n s v i l l e Sheet area the movement is north block down.
P y r i t i c silicified rhyolite occurs along the fault near Mount D a l r y m p l e .
A major northwesterly fault, here named the M i l l a r o o Fault, is believed to extend
northwards into the A y r Sheet a r e a . In the Bowen Sheet area, this fault has downthfown
L o w e r P e r m i a n Volcanics in the east against Upper Carboniferous granite in the west.
The granite near the confluence of the Bogie and Burdekin R i v e r s , to the south of the A y r
Sheet area, is strongly brecciated on the projection of the M i l l a r o o Fault, and the fault
is believed to have controlled the direction of the Burdekin R i v e r near h e r e . The M i l ­
laroo Fault may extend farther northwest beneath the alluvium, and the brecciated m i c r o ­
granite at the confluence of Seven M i l e and Major C r e e k s may possibly be an indication
of it.
T h e r e is evidence of strong faulting (Sugar Loaf Fault) p a r a l l e l to the coast between
Beach Hill and Green H i l l . Mylonite is present in p l a c e s . The shearing is stronger at Sugar
Loaf in the northwest than at Green Hill in the southeast. The Sugar Loaf Fault is normal to
the Inkerman Shear Zone and roughly parallel to the M i l l a r o o Fault.
42
Numerous dyke s w a r m s intrude the plutonic r o c k s ( C - P d and C - P g ) p a r a l l e l to the
Sugar Loaf and M i l l a r o o Faults. East of Stockyard C r e e k the dykes trend north-south,
possibly because of rotation by two northeasterly faults. The northwesterly dykes p e r s i s t
through and a r e therefore younger than the Inkerman Shear Zone. They may be genetically
r e l a t e d to, the L o w e r P e r m i a n volcanics ( L i z z i e C r e e k V o l c a n i c s , Bowen Sheet a r e a )
and Upper Carboniferous to P e r m i a n volcanics ( C - P v ) .
Numerous other faults have been mapped in the southwest. Most of them appear to
be of local significance only. The strong faults on the border of the Upper Carboniferous
v o l c a n i c s of Mount D a l r y m p l e may have developed as a result of subsidence of the m a s s i v e
p i l e of v o l c a n i c s , together with v e r t i c a l movement along the Woodhouse Fault. The fault
along the southwestern side of Mount Dalrymple may be a branch of the Woodhouse Fault.
Detailed g r a v i t y surveys in the Burdekin R i v e r Delta have r e v e a l e d a sharp northnorthwesterly g r a v i t y gradient a few m i l e s east of A y r . The gradient i s interpreted as
a hinge-fault (east block down) in the p r e - C a i n o z o i c basement, the throw being g r e a t e r in the
north than in the south (Wiebenga et al., 1966, unpubl.).
A strong negative g r a v i t y anomaly, roughly c i r c u l a r in plan, is centered 1^ m i l e s
south of the Burdekin R i v e r b r i d g e . It is possibly due to a r e l a t i v e l y low density intrusion
(Wiebenga et al., 1966, unpubl.).
G E O L O G I C A L HISTORY
The oldest r o c k s known a r e isolated remnants of metamorphics ( P z u ) which crop
out in the southwest. They r e p r e s e n t altered impure arenites and siltstones which w e r e
probably deposited in the e a r l y P a l a e o z o i c , and a r e intruded by the Ravenswood Grano­
d i o r i t e . Similar r o c k s occur in the southern part of the Cape Upstart peninsula and near
Guthalungra, but it is not known whether they are the same a g e . They a r e older than the
plutonic rocks mapped as Upper Carboniferous to L o w e r P e r m i a n .
Two isotopic dates of 420 m y (Silurian)havebeen obtained on the e a r l i e r ( g r a n o d i o r i t i c )
phase of the Ravenswood Granodiorite in the T o w n s v i l l e Sheet a r e a .
-
#
The calcareous hornfels at C h a r l i e s Hill is the only r e c o r d of sedimentation between
Silurian and Carboniferous t i m e s . The beds w e r e probably deposited in a shallow n e a r shore environment, with basement rocks cropping out nearby.
The late P a l a e o z o i c (late Carboniferous and e a r l y P e r m i a n ) was a t i m e of widespread
igneous activity and tectonic unrest in eastern Queensland. Most of the plutonic r o c k s a r e
believed to have been emplaced in this late P a l a e o z o i c p e r i o d of r e c u r r e n t mobilization
of magma. The acid v o l c a n i c s in the southwest (Cuv) w e r e extruded in the Upper Carbon­
iferous; their distribution was probably partly controlled by the Woodhouse Fault.
Intrusion of d i o r i t e - g r a n o d i o r i t e ( C - P d ) and granite-adamellite ( C - P g ) w a s accompanied
and c l o s e l y followed by faulting, shearing, and by the intrusion of dykes. The intermediate
volcanics ( C - P v ) w e r e probably erupted between separate Upper Carboniferous and
L o w e r P e r m i a n intrusive epochs, and acid vulcanism ( C - P h ) is b e l i e v e d to have r e c u r r e d
at that t i m e . H i g h - l e v e l granites ( P - M g ) , accompanied by minor dyke intrusion, w e r e
emplaced in the P e r m i a n o r M e s o z o i c .
T h e r e is no r e c o r d of sedimentation during the M e s o z o i c , although there a r e remnants
of possible M e s o z o i c sediments in the southeastern part of the T o w n s v i l l e Sheet area
(Wyatt et al., 1970a). During this e r a the environment was chiefly e r o s i o n a l .
The development of • the coastal plain during the Cainozoic led to the deposition
of superficial alluvial, deltaic, and littoral deposits. In the A y r Sheet a r e a , it i s not known
to what extent the formation of the coastal plain was due to faulting, but the development
43
of a T e r t i a r y graben in the P r o s e r p i n e Sheet area (White & Brown, 1963, unpubl.;
C l a r k e et a l . , 1968, unpubl., and in p r e p . ) indicates that faults may also have been active
at the same time in the A y r Sheet a r e a .
ECONOMIC G E O L O G Y
A p a r t f r o m m i n o r molybdenum mineralization at K e l l y s Mount, no metalliferous
deposits a r e known in the A y r Sheet a r e a . Minor occurrences of phosphate r o c k (Holbourne
Island), v e r m i c u l i t e (Stokes Range a r e a ) , and graphite (Cape Upstart peninsula) have been
r e c o r d e d . The groundwater in the Burdekin R i v e r Delta and the w a t e r in the Burdekin
R i v e r a r e of major economic importance.
Groundwater
Groundwater i s used extensively in the Burdekin Delta for i r r i g a t i o n . Intensive
hydrological and geophysical investigations have been c a r r i e d out in the past few y e a r s ,
and the results have been s u m m a r i z e d in an unpublished ' P r o g r e s s R e p o r t on the Water
R e s o u r c e s of the Burdekin Delta* submitted to the Queensland Irrigation and Water Supply
C o m m i s s i o n in June 1964. The Bureau of Mineral R e s o u r c e s has since c a r r i e d out further
geophysical w o r k to define the structure of the delta (Andrew & Wainwright, 1964,
unpubl,; Andrew et a l . , 1965; Wiebenga et al., 1966, unpubl.).
Metals
at
T h e r e i s no r e c o r d e d production of m e t a l s . Workings in p y r i t i f e r o u s metarhyolite
the eastern end of the Mount D a l r y m p l e range a r e possibly old gold p r o s p e c t s .
During the regional mapping, minor occurrences of the copper m i n e r a l s malachite,
a z u r i t e , and chalcopyrite w e r e found in altered r o c k s 4 m i l e s southwest of Mount Inkerman
in the Inkerman Shear Zone, and in v o l c a n i c s in the Burdekin R i v e r near M i l l a r o o . A
little finely disseminated chalcopyrite has been noted in gabbro near Abbot Point (see
Appendix 3 ) .
T h r e e o f the f i v e specimens analysed spectrochemically (see Appendix 1) contain
interesting metal v a l u e s : a g r e i s e n from a costeaned a r e a on the northeastern slope
of K e l l y s Mount contains 300 ppm molybdenum; the epidote r o c k f r o m the Inkerman Shear
Zone ( A r 9 / 7 / 3 7 ( K ) ) contains 1000 ppm nickel and 50 ppm cobalt; and the magnetite rock
f r o m the Inkerman Shear Zone contains 200 ppm copper and 40 ppm cobalt.
#
Morton (GSQ f i l e 30/609M, 7 Oct. 1930) has reported on an a r e a held by the A y r
Exploration Syndicate at K e l l y s Mount. The costeaned a r e a mentioned in the previous
paragraph i s b e l i e v e d to r e p r e s e n t p a r t of the Syndicate's w o r k i n g s . Morton reported
that 'greisenisation of the granite on a grand s c a l e , and to e v e r y d e g r e e of intensity,
i s in evidence
The numerous veins and veinlets of barren quartz in evidence within
the altered zone w e r e apparently introduced during the p r o c e s s of greisenisation, as
they do not occur in the surrounding unaltered granite*.
P y r i t e , or its oxidation products, w a s reported to be widespread, and t r a c e s of gold
and s i l v e r w e r e r e p o r t e d in part of the workings. Occasional vugs c a r r y i n g lead carbonates
with an appreciable s i l v e r content and t r a c e s of bismuthinite accompanying p y r i t e w e r e
r e p o r t e d f r o m e l s e w h e r e in the w o r k i n g s . A sample f r o m one of the shafts assayed 1
dwt 14 g r of gold and 60 dwt of s i l v e r . Morton concluded that the low values encountered
did not justify further prospecting. H o w e v e r , he stressed the l a r g e extent of the g r e i s e n ,
and the possibility of economic mineralization at depth cannot be e n t i r e l y discounted.
44
In 1966-67 Australian Selection Pty Ltd located molybdenum anomalies in the g r e i s e n
by g e o c h e m i c a l sampling, and d r i l l e d shallow percussion holes (up to 200 ft) on some of
the a n o m a l i e s . H o w e v e r , the molybdenum values intersected w e r e uneconomic (Australian
Selection P t y L t d , 1967, unpubl.).
A number of samples of beach sand have been m i n e r a l o g i c a l l y examined (see Appendices
2, 3 ) . The m o s t interesting m i n e r a l sand occurs at Dingo Beach, just w e s t of Abbot
Point, w h e r e a thin blanket of dark blue-black ilmenite-magnetite sand has been concen­
trated f r o m gabbro which crops out nearby. The analysed sample contains 87 percent iron
and titanium o x i d e s . It is estimated that about 3000 tons of ilmenite are present in 10,000
tons of sand o v e r a length of 3000 feet, an a v e r a g e width of 30 feet, a maximum thickness
of about 18 inches in the centre, and a grade of 30 p e r c e n t ilmenite, but it i s difficult
to a s s e s s the proportion of ilmenite in the c o m p l e x oxides (see Appendices 2, 3 ) . The
old beach dune inland f r o m the present beach contains a considerable proportion of dark
m i n e r a l s ; the g r a d e i s much lower than in the sands on the beach, but the deposit i s much
larger.
Rock Phosphate
A s m a l l l o w - g r a d e deposit of phosphatized c o r a l l i n e beach c o n g l o m e r a t e occurs
at Holbourne Island. Production f r o m the island w a s :
Tons
1918
1919
1920
1921
Total
450
650
850
450
2400
(averaging about 18% P 2 ° 5 )
Saint-Smith (1919), Reid (1944), and Young (1944, unpubl.) have reported on the deposit.
The c o r a l l i n e m a t e r i a l has been phosphatized by leaching f r o m guano, and i s not suitable
for the production of superphosphate because of wide variations in grade and a high content
of iron and c a l c i t e .
Earth L i m e
Two
small
deposits
of 'earth lime*
(see p . 39 ) a r e being worked f o r local use.
Eight M i l e s South of Inkerman Homestead. It was c l a i m e d by the operator that 16
a c r e s of w o r k a b l e l i m e have been p r o v e d in this deposit. One d r i l l hole is r e p o r t e d to have
penetrated 50 feet of earth l i m e without reaching the bottom of the deposit. F r o m the
surface the section i s : black soil (2 f t ) ; g r e y soil (3-4ft); white earth l i m e . The deposit
consists of zones of uniform earth l i m e (probably d e r i v e d f r o m d i o r i t e ) , and zones of
partly calcified colluvium where the earth l i m e contains up to 50 percent of cobbles and
pebbles of m i c r o d i o r i t e and m i c r o g r a n i t e which have not been calcified. In one place a
2-foot m i c r o d i o r i t e dyke, which has not been c a l c i f i e d , f o r m s a bar through a zone of
almost pure earth l i m e . The deposits w e r e probably f o r m e d by s e l e c t i v e calcification of
the c o a r s e plutonic r o c k s and the m a t r i x of the unconsolidated colluvium; the fine-grained
igneous r o c k s a r e not v i s i b l y affected.
T e n M i l e s Southwest of Inkerman Homestead. The deposit 10 m i l e s southwest of
Inkerman homestead i s a bed f r o m 4 to 12 feet thick which c o v e r s only a few a c r e s . Much
of the l i m e appears to be pure, and little rubble i s associated with it, but some zones a r e
probably low in g r a d e . The deposit i s p o o r l y exposed owing to an extensive blanket of black
soil.
45
Graphite
Jack (1888) r e c o r d e d the p r e s e n c e of graphite near Cape Upstart, and Dunstan (1921)
w r o t e : ' A t Cape Upstart, a seam of graphite 4 to 8 feet thick occurs in coal measure
strata, the alteration of coal to graphite being caused by a m a s s i v e igneous intrusion.
N o p a r t i c u l a r s a r e available, h o w e v e r , concerning the character or quality of the g r a p h i t e ' .
The o c c u r r e n c e i s situated 2.5 m i l e s west-northwest of the The Cape homestead,
l o w on the eastern slope of a granite spur. The old shaft i s surrounded by mullock of black
chiastolite hornfels, s o m e specimens of which a r e soft, friable, and sooty, w h e r e a s others
a r e hard and dense. Some micronodular v e r m i f o r m aggregates of calcite a r e also present.
The hornfels c r o p s out sporadically around the foot of the spur.
M a t e r i a l f r o m this shaft i s r e p o r t e d to have been shipped to Germany for treatment
in the e a r l y part of this century ( W . Hickmott, p e r s , c o m m . ) . The graphite content of the
lip of the old shaft was estimated at 30 to 40 percent ( I . R . Pontifex, p e r s . c o m m . ) .
V e r m i c u l i t e , A s b e s t o s , and Garnet
L o w - g r a d e v e r m i c u l i t e and asbestiform t r e m o l i t e occur in the Inkerman Shear Zone
and Stokes Range (Carruthers, 1954). The v e r m i c u l i t e is c l o s e l y associated with weathered
biotite in altered granodiorite g n e i s s . Monomineralic garnet rocks also occur in the
Inkerman Shear Zone. No production of these minerals i s r e c o r d e d , but a local resident
r e p o r t e d that they had been worked.
Road Metal and Railway Ballast
Granite i s quarried for road metal in a hill to the north of The Rocks, 10 m i l e s south­
w e s t of A y r , and for r a i l w a y ballast at Mount C a r e w ,
Future P r o s p e c t s
The a r e a s believed to have most p r o m i s e of economic mineralization a r e the Inkerman
Shear Zone and the a r e a immediately east of Mount D a l r y m p l e .
The Inkerman Shear Zone is a fundamental structure which has been the locus of
major metasomatic activity (monomineralic and skarn-type r o c k s ; anomalous nickel,
c o p p e r , and cobalt v a l u e s ) , and w a r r a n t s detailed examination.
The area east of Mount D a l r y m p l e i s intersected by at least two major faults, the
Woodhouse and M i l l a r o o Faults, and p y r i t i c r o c k s and possible old workings have been
noted in the a r e a .
46
REFERENCES
A N D R E W , J . T . G . , and W A I N W R I G H T , M „ 1964 - Giru underground water
Queensland, 1963, Bur, M i n e r , Resour. Aust, R e c . 1964/111 (unpubl,),
survey,
A N D R E W , J . T . G . , E L L I S , W . R . , S E A T O N B E R R Y , B . W . , and W I E B E N G A , W , A „ 1965 The use of radioisotopes as groundwater t r a c e r s in the Burdekin delta area of north
Queensland, Australia, Aust, atom. En, C o m m . R e p . A A E C / E 1 3 7 ,
A U S T R A L I A N S E L E C T I O N P T Y L T D , 1967 - Report on prospecting up to 31st December
1966. Authority to P r o s p e c t N o . 325M, K e l l y s Mountain, A y r district (unpubl.).
BENSON, W . N . , 1913 - The geology and petrology of the G r e a t Serpentine Belt of New
South W a l e s (3, P e t r o l o g y ) .
P r o c . Linn. Soc. NSW, 38(4), 662-724.
B L A K E , D . H . , E L W E L L , R . W . D . , GIBSON, I . L . , S K E L H O R N , R . R . , and W A L K E R , G . P . L . ,
1965 - Some relationships resulting from the intimate association of acid and basic
m a g m a s . Quart. J. g e o l . Soc. Lond., 121, 31-49.
C A R R U T H E R S , D.S., 1954 - V e r m i c u l i t e and asbestos o c c u r r e n c e s , Home Hill d i s t r i c t .
Qld Govt M i n . J., 55, 64-5,
C H R I S T I A N , C.S., P A T E R S O N , S.J., P E R R Y , R . A . , S L A T Y E R , R . O . , S T E W A R T , G . A . ,
and T R A V E S , D . M . , 1953 - Survey of the T o w n s v i l l e - B o w e n r e g i o n , north Queensland,
1950. Sci, ind. R e s . O r g . M e l b . , Land R e s . Ser,, 2.
C L A R K E , D . E . , 1969 - Geology of the Ravenswood 1-mile
Bur. M i n e r , Resour, Aust, R e c , 1969/117,
Sheet area, Queensland.
C L A R K E , D . E . , P A I N E , A . G . L . , and JENSEN, A . R . , 1968 - The geology of the P r o s e r p i n e
1:250,000 Sheet area, Queensland. Bur. M i n e r . Resour. Aust. R e c . 1968/22 (unpubl.).
C L A R K E , D . E . , P A I N E , A . G . L . , and JENSEN, A . R . , in p r e p . - Idem. Bur. M i n e r . Resour.
Aust. R e p .
CONNAH,
T . H . , 1958 - Limestone r e s o u r c e s
of Queensland.
Qld Govt Min. J., 59,
637-53, 738-55.
D A R B Y , F . , 1966 - North Bowen Basin reconnaissance g r a v i t y survey, Queensland, 1963.
Bur. M i n e r . R e s o u r . Aust. R e c . 1966/209 (unpubl.).
D U N S T A N , B . , 1921 - Graphite, A r t i c l e 7; in Industrial M i n e r a l s .
G e o l . Surv. Qld Publ.
268, 217.
H A R L A N D , W . B . , S M I T H , A . G . , and W I L C O C K , B . , 1964 - The Phanerozoic time s c a l e .
Quart. J. g e o l . Soc. Lond. (Supplement), 120s.
I R R I G A T I O N A N D W A T E R S U P P L Y COMMISSION, Q U E E N S L A N D , 1964 - P r o g r e s s r e p o r t
on the w a t e r r e s o u r c e s of the Burdekin R i v e r Delta (unpubl.).
JACK,
R . L . , 1888 - The mineral wealth of Queensland.
G e o l . Surv. Qld Publ. 48.
M A L O N E , E.J., JENSEN, A . R . , G R E G O R Y , C . M . , and F O R B E S , V . R . , 1966 - Geology
of the southern half of the Bowen 1:250,000 Sheet area, Queensland. Bur. M i n e r . Resour.
Aust. R e p . 100.
M A R S H A L L , N . J . , 1967 - Regional geochemical survey, A y r 1:250,000 Sheet, Queensland.
Bur. M i n e r . R e s o u r . Aust. R e c . 1967/129 (unpubl.).
M c K E L L A R , R . G . , 1963 - Palaeontological r e p o r t on some plant collections from the Ewan
and Manton 1-mile a r e a s .
R e p , g e o l . Surv. Qld (unpubl.).
47
P A I N E , A . G . L . , G R E G O R Y , C . M . , and C L A R K E , D . E . , 1966 - Geology of the A y r 1:250,000
Sheet area, Queensland. Bur. M i n e r . Resour. Aust. R e c . 1966/68 (unpubl.).
P A I N E , A . G . L . , C L A R K E , D . E . , a n d G R E G O R Y , C . M . , in p r e p . - Geology of the northern
half of the Bowen Sheet area, Queensland (with additions to the geology of the southern
half). Ibid.
R E I D , J.H., 1944 - Holbourne Island phosphate deposits.
Qld. Govt Min. J., 45, 153-4.
S A I N T - S M I T H , E . C . , 1919 - Rock phosphate deposit on Holbourne Island, near Bowen.
Qld Govt M i n . J „ 20, 122-4.
T R A V E S , D . M . , 1951 - A g e o l o g i c a l reconnaissance in the T o w n s v i l l e - B o w e n r e g i o n ,
northern Queensland. Bur. M i n e r . R e s o u r . Aust. R e c . 1951/25 (unpubl.).
T U R N E R , F . J., 1933 - The metamorphic
T r a n s . N . Z . Inst., 63, 269-76,
WATKINS,
J.R.,
and W O L F F ,
Interim R e p o r t .
WEBB,
A . W . , and
and intrusive
rocks of southern Westland.
K . W . , 1960 - Burdekin delta groundwater investigation,
Rep, g e o l . Surv. Qld, E9 (unpubl.).
McDOUGALL,
Eungella, Queensland.
I . , 1964 - Granites
of L o w e r
Cretaceous age near
J. g e o l . Soc. Aust., 11(1), 151-3.
W H I T E , A . J . R . , 1959 - Scapolite-bearing m a r b l e s and c a l c - s i l i c a t e r o c k s f r o m Tungkillo
and Milendella, South A u s t r a l i a . G e o l . M a g . , 96(4), 285-306.
W H I T E , W . C . , and BROWN, G . A . , 1963 - P r e l i m i n a r y r e p o r t on the geology of the Mackay
region, area 93P and the southern part of 94P. R e p . Ampol Exploration (Qld) Ltd
(unpubl.).
W I E B E N G A , W . A . , P O L A K , E.J., A N D R E W , J . T . G . , W A I N W R I G H T , M „ and K E W I ,
L . , 1966 - Burdekin delta underground water investigation, north Queensland 1962-3.
Bur. M i n e r . R e s o u r . Aust. R e c . 1966/48 (unpubl,).
W Y A T T , D , H „ P A I N E , A . G . L . , C L A R K E , D . E . , and H A R D I N G , R . R . , 1970a- Geology of the
T o w n s v i l l e 1:250,000 Sheet a r e a , Queensland. Bur. M i n e r . Resour. Aust. R e p . 127.
W Y A T T , D . H . , P A I N E , A . G . L . , C L A R K E , D . E . , G R E G O R Y , C , M „ and H A R D I N G , R . R . ,
1967 - Geology of the Charters T o w e r s 1:250,000 Sheet area, Queensland.
Bur. M i n e r .
R e s o u r . Aust. R e c . 1967/104 (unpubl.).
W Y A T T , D . H . , P A I N E , A . G . L . , C L A R K E , D . E . , G R E G O R Y , C . M . , and H A R D I N G , R . R . ,
1970b.
Idem. Bur. M i n e r . R e s o u r . Aust. R e p . 137.
Y O U N G , C P . , 1944 - Report on Queensland phosphate deposits, Holbourne Island.
to British P h o s , C o m m . (unpubl.).
48
Rep.
APPENDIX 1
SPECTROCHEMICAL ANALYSES
by
A . D . Haldane
Semiquantitative spectrochemical analyses of five r o c k specimens f r o m the A y r Sheet
area, Queensland, a r e tabulated. A l l values are e x p r e s s e d in parts p e r m i l l i o n .
F i e
Number
m e n
A l >
3
/
5
/
5
1
(
P
)
A
r
9/7/37 (K) A r 9/7/37 (M)
10
10
50
7
40
12
10
2-
2-
200
2
15
15
30
300
a
a
a
1000
Co
a
Cu
V
Military
Grid Ref.
Rock type
A r 6/7/39
5-
Ni
Mo
A r 10/7/37
551537
558521
Greisen
iipidote
rock
558521
Epidotegarnet r o c k
510
558521
Magnetite
rock with
no v i s i b l e
copper
60
a
564520
Unmineralized
portion of s p e c i men of epidotegarnet-mag­
netite r o c k
In addition, P , W , Zn, Sn, B e , A g , and Bi w e r e sought but not detected in any specimen.
a, sought but not detected
5-, l e s s than 5 ppm; 2 - , l e s s than 2 ppm
49
APPENDIX 2
M I N E R A L O G I C A L C O M P O S I T I O N OF T H R E E S A M P L E S OF H E A V Y M I N E R A L SAND
F R O M BEACHES N E A R BOWEN
by
L R . Pontifex
A polished section and a thin section of a random sample of each sand w e r e examined.
The percentages of the m i n e r a l s present w e r e calculated f r o m a grain count of each
section.
Sample 1
Locality:
Air-photo:
of Bowen.
A y r , run 8, N o . 5061, point 14. Dingo Beach, 15 m i l e s northwest
Opaque m i n e r a l s :
Percent
Ilmenite with exsolution intergrowths of hematite,
r u t i l e , and magnetite
..
..
Titaniferous magnetite
..
Hematite containing exsolution intergrowths of
ilmenite
..
..
..
Hmenite
..
..
..
Hmenite-magnetite (grains having the p r o p e r t i e s
of both m i n e r a l s )
,.
..
Magnetite p a r t l y oxidized to hematite
..
..
26
23
..
..
10
11
..
..
9
8
Non-opaque m i n e r a l s :
Percent
Zircon
Amphibole
Augite
Epidote
Rutile
Quartz
Plagioclase
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
6
3
2
2
1
1
1
The a v e r a g e g r a i n s i z e i s 0.15 m m . Generally the grains a r e angular or subangular;
s o m e of the opaque grains a r e w e l l rounded.
The proportions of i r o n and titanium oxides v a r y f r o m grain to grain, and it is difficult
to determine the abundance of g r a i n s containing specific mixtures of these oxides. The
percentages of opaque m i n e r a l s given above a r e , t h e r e f o r e , accurate to within about 10
percent. It i s apparent that all these grains have a common source. The opaque m i n e r a l s
commonly f o r m c o m p o s i t e grains with amphibole. Z i r c o n o c c u r s as stumpy euhedral
c r y s t a l s . The m o s t c o m m o n amphibole i s hornblende. T w o types of epidote a r e present;
one is pale g r e e n - y e l l o w , the other deep s e a - g r e e n .
Sample 2
Locality:
Air-photo:
Ayr.
A y r , run 3, N o . 5037, Point 1.
50
Lynchs Beach, 10 m i l e s north of
Opaque m i n e r a l s :
Percent
Ilmenite with exsolution inter growths of hematite,
rutile, and titaniferous magnetite
..
Titaniferous magnetite
..
..
Ilmenite
..
..
..
18
12
10
Non-opaque m i n e r a l s :
Percent
Amphibole
Quartz
..
Epidote
..
Plagioclase
Augite
Zircon
..
Rutile
..
Orthoclase
..
Volcanic groundmass fragments
Organic fragments
..
Biotite
Tourmaline
..
Garnet
..
,.
..
..
..
..
..
..
..
..
..
,.
..
..
..
..
..
..
..
..
..
..
10
19
6
6
4
3
2
4
2
2
1
1
1
The a v e r a g e g r a i n s i z e is 0.15 m m . Generally the grains a r e angular or subangular.
Many have w e l l p r e s e r v e d c l e a v a g e faces and crystal f o r m .
The comments regarding the iron-titanium oxide m i n e r a l s given for Sample 1 also
apply to this s a m p l e . In Sample 2, h o w e v e r , a c c e s s o r y amounts of chalcopyrite and p y r i t e
a r e associated with some of the iron-titanium oxide grains. The sulphides f i l l fractures
in the oxides, and f o r m m a s s e s up to 0.05 m m .
Hornblende is the dominant amphibole. T w o different types of epidote a r e present in
about equal abundance. One is light g r e e n - y e l l o w , the other i s deep s e a - g r e e n . The p l a g ­
i o c l a s e was found to range f r o m o l i g o c l a s e toandesine. Most of the orthoclase grains a r e
fresh but some a r e partly altered to s e r i c i t e .
The grains which appear to be d e r i v e d f r o m a volcanic groundmass a r e m i c r o crystalline; the dominant component i s quartz; subordinate m i n e r a l s a r e feldspar and
sericite.
Sample 3
Locality:
A i r - p h o t o : A y r , run 9, N o . 5045, point 4 A . Kings Beach, 1 m i l e northeast of
Bowen (just south of A y r 1:250,000 Sheet a r e a ) .
Opaque m i n e r a l s :
Percent
Ilmenite with exsolution intergrowths of hematite,
rutile, and titaniferous magnetite
..
Titaniferous magnetite
,.
..
Ilmenite
..
..
.,
51
..
„
7
7
6
Non-opaque m i n e r a l s ;
Percent
Amphibole
Quartz
Plagioclase
Epidote
Orthoclase
Augite
Rutile
Organic fragments
Calcite
Zircon
Biotite
Chlorite
Hyper sthene
Spinel
Apatite
The g r a i n s i z e ranges
angular.
„
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
..
„
„
„
,.
..
..
..
..
..
„
„
„
„
„
„
.
„
# #
#
> #
25
14
10
7
5
4
4
4
4
2
2
2
+1
+1
+1
between 0.05 and 0.3 m m . The grains are angular and sub-
The comments r e g a r d i n g the opaque minerals given for Sample 1 also apply to Sample
3. The dominant amphibole i s hornblende, and some fragments of this m i n e r a l have
small iron oxide inclusions oriented along c l e a v a g e planes. The plagioclase i s g e n e r a l l y
unaltered. Most of the grains range f r o m andesine to o l i g o c l a s e , but about 25 percent of
them range f r o m labradorite to andesine.
T w o types of epidote a r e present: the most abundant is a light green y e l l o w i s h type,
which usually o c c u r s in anhedral g r a i n s ; the other i s deep g r e e n , and commonly has a
broken p r i s m a t i c f o r m .
The identification of the hypersthene is not certain.
52
APPENDIX 3
M I N E R A L O G I C A L C O M P A R I S O N OF I L M E N I T E SAND A N D G A B B R O F R O M
NEAR ABBOT POINT
by
I . R . Pontifex
1.
Ilmenite sand
F i e l d o c c u r r e n c e : T h i s is a beach sand specimen f r o m Dingo Beach, 1 m i l e w e s t
of Abbot Point. Gabbro c r o p s out east and west of Dingo Beach.
Mineralogy: In the field, the grains which w e r e attracted to a hand magnet w e r e
r e m o v e d . These w e r e presumably mostly magnetite. The remaining sand was separated
in the laboratory into 3 fractions on a Frantz isodynamic separator, and each of these
was examined m i c r o s c o p i c a l l y . A thin section and a polished section of a random sample
of the original m a t e r i a l w e r e also examined.
The following components (excluding the constituent r e m o v e d by magnet) w e r e i d ­
entified, and their approximate volume percentages w e r e estimated:
Ilmenite containing hematite inclusions
Titaniferous hematite
Ilmenite
Titaniferous magnetite
Zircon
Hornblende
Percent
55
15
10
5
8
2
Minor amounts of epidote, olivine, rutile, tourmaline, leucoxene, and p y r i t e are also
present. The a v e r a g e g r a i n s i z e is 0.15 m m . The opaque grains a r e angular and subangular.
The main constituent of the sample, i l m e n i t e , almost invariably contains needle
and bleb-like inclusions of titanhematite oriented along certain morphological d i r e c t i o n s .
This v a r i e t y of hematite by definition contains a maximum of 10 percent T i 0 2 . The exsolution
inter growth relationship of titanhematite and ilmenite indicates that the F^^S content
in the ilmenite e x c e e d s 6 percent. The grains in which titanhematite is the dominant
m i n e r a l commonly contain abundant inclusions of ilmenite d i s c s , which indicates that the
Ti0£ content in the hematite exceeds 10 percent.
Some homogeneous opaque grains have optical p r o p e r t i e s intermediate between
magnetite and ilmenite; others consist of titaniferous magnetite which contains exsolution
blades of ilmenite 0.01 m m w i d e . A l l these grains are d e r i v e d f r o m a solid solution of
iron and titanium o x i d e s . Ilmenite is the dominant component as no suggestion of the
spinel structure is evident in any of the grains.
Zircon and hornblende generally have a euhedral f o r m . Commonly hornblende is
associated with i l m e n i t e . Epidote, olivine, and leucoxene occur as i r r e g u l a r , generally
angular, fractured grains; some are subrounded. Rutile and tourmaline grains a r e
r e l a t i v e l y w e l l rounded.
2.
Gabbro (BMR TS14349)
Field o c c u r r e n c e :
A sample of a gabbro from 2 m i l e s w e s t of Abbot Point.
53
Description of thin section: The rock consists chiefly of an ophitic a g g r e g a t e of
p l a g i o c l a s e , hornblende, and augite. The a v e r a g e g r a i n s i z e of the p l a g i o c l a s e laths and
f e r r o m a g n e s i a n grains is 1 m m and 0.6 m m r e s p e c t i v e l y .
Euhedral c r y s t a l s of p l a g i o c l a s e consist mainly of labradorite, and f o r m about 55
percent of the r o c k . Some p l a g i o c l a s e i s slightly altered to s e r i c i t e and epidote.
Hornblende f o r m s about 20 p e r c e n t of the section; it occurs as anhedral grains and
as alteration r i m s around augite. The hornblende g e n e r a l l y contains fine opaque inclusions
and i s c o m m o n l y intergrown with s m a l l opaque m a s s e s . Some hornblende shows minor
alteration to c h l o r i t e .
About 15 percent of the r o c k consists of anhedral grains of augite, g e n e r a l l y as remnant
c o r e s surrounded by i r r e g u l a r c o r o n a s of hornblende.
Description of polished section: The opaque mineral grains have an a v e r a g e s i z e
of 0,2 m m , and f o r m the following approximate proportions of the r o c k :
Percent
3
2
2
0,5
Ilmenite containing hematite inclusions
Titaniferous hematite and magnetite
Pyrite
Chalcopyrite
The ilmenite containing hematite inclusions f o r m s anhedral grains which a r e associated
with hornblende; it has the s a m e m i n e r a l o g i c a l composition as the ilmenite-hematite
grains in the ilmenite sand p r e v i o u s l y described. The hematite is the v a r i e t y titanhematite,
and i s l o c a l i z e d as blebs and needles along morphological directions of the ilmenite
host. In s o m e grains hematite i s the dominant m i n e r a l , and these g e n e r a l l y contain
ilmenite b l e b s .
Grains which have a composition intermediate between magnetite and ilmenite a r e
almost as c o m m o n as the ilmenite-hematite g r a i n s . P y r i t e occurs as d i s c r e t e anhedral
grains, and i s a l s o associated with the iron and titanium oxides.
Chalcopyrite grains up to 0.01 m m a r e disseminated through the r o c k ; these a r e not
associated with the other opaque m i n e r a l s .
Conclusions
The m i n e r a l o g i c a l composition of the opaque m i n e r a l s in the beach sand and in the
gabbro i s s i m i l a r ; in both the dominant heavy mineral i s ilmenite which contains exsolution
intergrowths of titanium-rich hematite. Grains containing various proportions of iron
and titanium oxides a r e also c h a r a c t e r i s t i c of both samples; such grains a r e commonly
associated with hornblende.
The angular nature of the g r a i n s , and the p r e s e n c e of unaltered hornblende and olivine
in the sand, suggest that it i s r e l a t i v e l y near its source.
T h e s e relationships indicate that the gabbro i s the source rock f o r the detrital iron
and titanium oxides, hornblende, and epidote on the adjacent beach,
A minor contribution of detrital m i n e r a l s f r o m a second provenance i s indicated by
the p r e s e n c e of z i r c o n and tourmaline in the sand. T h e s e minerals w e r e no doubt derived
f r o m the acid igneous intrusives of the area.
54
APPENDIX 4
W A T E R BORES D R I L L E D T O BEDROCK IN THE BURDEKIN RIVER D E L T A
Information supplied by Queensland Irrigation and Water Supply
Commission
Irrigation
R.L.
Natural Surface
Depth
to
D r i l l e r ' s Description
Commission
Bore Number
(State Datum)
( N / R - not recorded)
Bedrock
(ft)
of
Bedrock
B3S1
L3B8
L3B7
CD4
18
25
27
252
178
189
185
204
271
Porphyry
Decomposed rock
CD7A
B3S2
E2.5
26
17
N/R
N/R
110
Granite
Granite
Granite
Rock
Decomposed granite
E3
D2.5
DE3
E3A
42
N/R
N/R/
37
100
158
170
114
Decomposed granite
Basalt
Rock
Decomposed granite
L3B5
L3B4
F4A
FG4.2
F4.5
45
N/R
47
N/R
N/R
128
101
98
Diorite
Decomposed granite
Decomposed granite
Decomposed granite
FG4.7
FG4.9
EF5.2
N/R
N/R
N/R
N/R
EF5.4
E5A
D6A
E6B
B1S3
FG3A
FG4
FG4.8
H4
GH4.2
GH4.6
GH4A
G4.9
G50
H6
GH5A
FG5.2
F5
GH7A
G8
JO.8
J1.3
41
29
N/R
N/R
53
N/R
N/R
61
N/R
N/R
60
N/R
46
39
41
N/R
N/R
18
23
65
70
103
104
60
81
144
143,151
Granite
Porphyry
Granite
Granite
Granite, porphyry
188
202
210
Weathered rock. Quartz
Weathered granite
Diorite
250
64
86
Granite
Quartz
Quartz
103
71
Granite
Decomposed granite
103
104
115
85
79
62
Granite
Weathered granite
139
94
120
87
112
79
66
55
Weathered granite
Granite
Decomposed granite
Granite
Granite
Granite
Granite
Decomposed granite
Rock
Granite
Granite
F i g . 17:
Location of water bores which reached bedrock in the Burdekin R i v e r Delta.
56
Irrigation
Commission
Bore Number
HJ3A
J4
HJ4A
J5
HJ5
HJ5.2
HJ6
HJ6.1
J6
J7
K7
HJ7A
JK8
B4S5
F10
HJ0.2A
HJ1A
HJ1.7A
MP49.5/99.5
J0.3
J0.8
J1.3
MP49/98
JK0.2
JK0.8
JK1.2
MP48/97
L7B4
L7B10
L7B11
L7B1
Note:
R.L.
Natural Surface
(State Datum)
( N / R - not r e c o r d e d )
N/R
N/R
55
N/R
N/R
N/R
N/R
N/R
41
29
27
26
N/R
N/R
18
60
60
82
81
64
65
70
77
69
71
79
81
76
76
84
90
Depth
to
Bedrock
(ft)
40
34
71
66
74
73
119
79
62
D r i l l e r ' s Description
of
Bedrock
Diorite
Weathered granite
Fractured r o c k
Decomposed granite
Decomposed granite
and
quartz
Decomposed granite
Decomposed granite
Decomposed granite
Decomposed granite
Decomposed granite
Decomposed granite
Decomposed granite
Decomposed granite and quartz
Decomposed granite
134
30-43 (bottom) Black sand
137
Basalt
90
Granite
83
Granite
62
Granite
86
Granite
Granite
78
Granite
66
Granite
46
79
Granite
Basalt, granite
63
L i m e s t o n e , basalt, granite
69
76
Granite
92
Hard r o c k
105
Granite
84
Granite
105
Stone
56
24
68
30
B o r e F10 did not bottom in bedrock; it has been included h e r e because of the
interesting 13-foot intersection of black sand.
57
APPENDIX 5
ISOTOPIC A G E DETERMINATIONS
By A . W . W E B B
Rock U n i t /
Map Symbol
Sheet A r e a
Specimen N o .
ANU
Accession N o .
Military G r i d Reference
E
N
Rock Type
Mineral
Analysed
Method
Age
(m. y . )
P-Mg
E55/15/5
GA5733
518000
2582000
Adamellite
Biotite
K/Ar
267
P-Mg
6
GA5579
516000
2557000
Granite
Biotite
K/Ar
269
266
C-Pd
1
GA5275
548500
2531300
Granodiorite
Biotite
K/Ar
C-Pd
2
GA5276
558000
2520700
Diorite-gneiss
Hornblende
K/Ar
264
C-Pd
3
GA5277
558000
2520700
Green amphibole rock Amphibole
K/Ar
245
C-Pd
4
GA5319
558000
2520700
Diorite-gneiss
Hornblende
K/Ar
275
C-Pd
13
GA5580
567600
2512300
Granodiorite
Biotite
K/Ar
269
C-Pd
13
GA5580
567600
2512300
Granodiorite
Hornblende
K/Ar
281
A
Ar
4 0 , , atm.
/Ar
(%)
E55/15/1
13
Biotite
The shear zone specimens contain two foliated dioritegneisses (2,4) and an amphibole rock (3). The approximate age
of 270 m.y. for 2 and 4 is one which is common to the south
in the Bowen a r e a . It may relate to movements in the shear
zone and is unlikely to be the actual age of emplacement of
the rocks. The date measured on specimen 3 may indicate
later movements along the shear zone producing r e c r y s t a l lization and the formation of a rock composed of almost 100
percent amphibole.
(%)
7.270 )
7.26
7.246 )
0.0167
0.4209)
0.4185)
0.01653
25.6
0.1998)
0.2019)
0.01528
15.6
0.3369)
0.3384)
0.01727
18.9
7.014 )
7.005 )
0.01675
4.3
7.064 )
7.117 )
0.01687
3.5
7.177 )
7.206 )
0.01691
1.6
13
0.5456)
Hornblende 0.5446)
8.0
= 0.584 X l O - i O y r " ; \P
= 4.72 x l O "
* rj
Specimen 1, f r o m The Rocks, is intruded by several
younger igneous rocks and the date of 266 m.y. possibly r e ­
flects this later activity. The discordance between the biotite
and hornblende dates of specimen 13 also suggests argon
leakage.
14.4
0.01773
1
Specimens 5 and 6 w e r e from Cape Cleveland and Mount
Elliot respectively, and the age of 265-270 m.y. is similar to
that obtained from the Thunderbolt Granite in the Bowen Sheet
area.
1 0
1
^" ;
4
0
4
K = 1.22 x 1 0 ~ g / g K
Note: the analytical e r r o r in individual K / A r determinations is +_ 3 percent, unless
otherwise stated
Three groups of specimens w e r e dated:
(1)
Numbers 2, 3, and 4, f r o m the Inkerman Shear Zone
(2)
Numbers 5 and 6, late Palaeozoic granitic intrusions
(3)
Numbers 1 and 13, which a r e possibly unrelated to the other
two groups.
58
W . G . M U R R A Y , Government Printer, Canberra
18563/69—L
^ /
BUREAU OF MINERAL RESOURCES,GEOLOGY AND GEOPHYSICS
AYR
AUSTRALIA 1 : 2 5 0 , 0 0 0 GEOLOGICAL SERIES
FIRST EDITION 1968
SHEET SE 55-15
QUEENSLAND
Reference
Geological
Fault,
boundary
showing
Boundary
of major
Where
line
relative
location
Joint
shear
where
and faults
inferred,
are dotted,
movement
zone
of boundaries
is broken;
boundaries
horizontal
queried;
and faults
is
approximate,
where
are shown
dashes
pattern
2 60 OOOOy N
> air-photo
Trend
of coastal
Strike
and dip of
strata
Strike
and dip of
cleavage
Strike
and dip of
foliation
sand
Vertical
foliation
Foliation,
dip
Strike
dunes
Strike
platy
Reference
flow
banding
Sample
J
flow
and dip of primary
Primary
interpretation
indeterminable
and dip of platy
Vertical
®2
concealed,
by short
banding
in gabbro,
locality
for age
dip
in
gabbro
Qm
Coastal
mud
Qr
Coastal
sand
Qu
Outwash
C
Alluvial
flats
indeterminable
QUATERNARY
determination
Dyke
dunes
U
do = dolerite,
andesite,
O
microdiorite
and
talus
N
f = felsite
(including
rhyolite
g = granophyre,
mt
and acid
porphyry)
granite
<
z
a
Mineral
prospect,
little
or no
Czc
Unexploited
Minor
mineral
mineral
Residual
soil,
1
| Earth
Silver
Au
Gold
Cu
Copper
Gt
Graphite
Im
Ilmenite
Ls
Limestone
Mo
Molybdenum
Mt
Magnetite
Ni
Nickel
Pb
Lead
Ph
Phosphate
Py
Pyrite
Rc
Crushed
('earth
material
leucocratic
rhyolite-porphyry,
adamellite
and granite,
rare diorite
microdiorite,
and
P-Md
Dolerite,
P-Mv
Hornfelsed
tuff
C-Pv
Intermediate
lavas
C-Ph
Rhyolite,
C-Pg
Adamellite,
C-Pd
Diorite,
quartz
diorite,
tonalite,
adamellite
and
granite
minor
granophyre,
syenite,
gabbro
gabbro
lime')
UPPER
CARBONIFEROUS
TO LOWER
PERMIAN
trachyte,
and pyroclastics,
trachyandesite;
granite,
some
minor
acid
mainly
granodiorite;
volcanics
intrusive
minor
fine-grained
variants
Rock
rock
aggregate
o
o
N
O
Bore
1
Windpump
LJ
<
Spring
_ l
o-
semi-consolidated
occurrence
PERMIAN TO
MESOZOIC
Bismuth
some
deposit
P-Mg
Bi
and rubble;
lime'
Epizonal
Ag
sand
production
Quarry
®
deposits
microtonalite
Czs
\
and deltaic
o
Cuv
Flow-banded
rhyolite
Ce
Flow-banded
rhyolite,
p j
Hornfelsed
gabbro,
and massive
norite;
welded
tuff;
minor
granodiorite,
andesite
and andesitic
tuff
UPPER
CARBONIFEROUS
Ellenvale Beds
rhyolite-breccia,
andesite
<
ioi
Dam
CL
Waterhole
Bank
4^
on
stream
of major
Depth
in
SILURIAN
TO LOWER
DEVONIAN
fathoms
EARLY
PALAEOZOIC
Road
— I
1—
H—i—'—i—
Vehicle
track
Railway
with
Tramway
z
calcareous
conglomerate,
Ravenswood
Granodiorite
Biotite
granite,
S-Dr
Deeply
quartz
weathered
hornblende-biotite
diorite,
diorite,
alkali
granite
Pzu
Schist,
S-Da
phyllite,
leucocratic
-
—i
r
quartzite,
hornfels
siding
(sugar
cane)
transmission
Telephone
line
line
Town
•' Lisgai
Homestead
House
• Pump
•Yd
®
or
building
Pumping
station
Yard
Airfield
•
Landing
&
Trigonometrical
•1900'
Elevation
A MW
Microwave
calcareous
quartzite
interbeds
adamellite
Fence
Power
with
watercourse
Swamp
—-10—~
UPPER
DEVONIAN ?
ground
station
in feet,
derived
repeater
from
military
2 50 OOOOy N
maps
DIAGRAMMATIC RELATIONSHIP OF MAIN ROCK UNITS
station
20° 00'
68 OOOOy E
148°30'
PROSERPINF 4?M
C o m p i l e d a n d p u b l i s h e d by t h e B u r e a u o f M i n e r a l R e s o u r c e s , G e o l o g y a n d G e o ­
p h y s i c s , D e p a r t m e n t of National D e v e l o p m e n t , in c o n j u n c t i o n w i t h t h e G e o l o g i c a l
Survey o f Q u e e n s l a n d . Issued under t h e authority of t h e H o n . David Fairbairn,
M i n i s t e r f o r N a t i o n a l D e v e l o p m e n t . B a s e m a p c o m p i l e d f r o m 1 : 75,000 s c a l e
t o p o g r a p h i c c o m p i l a t i o n s s u p p l i e d by t h e R o y a l A u s t r a l i a n S u r v e y C o r p s .
V e r t i c a l a e r i a l p h o t o g r a p h y a t 1 : 85,000 s c a l e b y A d a s t r a A i r w a y s P t y . L t d . , 1 9 6 1 .
Transverse Mercator Projection.
G e o l o g y , 1 9 6 4 , b y : A . G . L. P a i n e , C . M . G r e g o r y ( B . M . R . ) , D . E. C l a r k e ( G . S . Q . )
C o m p i l e d b y : A . G . L. P a i n e , C . M . G r e g o r y , N . L. K r u g e r , A . T a t a r o w ( B . M . R . ) ,
D . E. C l a r k e ( G . S . Q . )
Drawn b y : A u s t r a l Cartographic Service, Canberra, A . C . T .
Scale 1:250,000
INDEX TO ADJOINING SHEETS
Showing Magnetic
Unconformity
15 MILES
5
Declination
GEOLOGICAL RELIABILITY DIAGRAM
25 KILOMETRES
10
CROWN COPYRIGHT RESERVED
GREY NUMBERED LINES INDICATE THE 20.0DO YARD TRANSVERSE MERCATOR GRI1, ZONE 7 (AUSTRALIA SERIES)
Bi
Detailed reconnaissance with air-photo
B2
Mainly air-photo
interpretation
interpretation
Section
ROCKHAMPTON
Scale:
= 4
Cainozoic sediments omitted from section;
ANNUAL CHANGE
attitude of faults not k n o w n
1'30"E
Stockyard Creek
MT ROUNDBACK
INC SPUR)
Elliot River
Molongle Creek
Bobs Creek
SPROLE CASTLf.
AYR
SHEET SE 55-15
T
C-Pd
C-Pd,
i
i
j _
^C-Pd,
C-Pg
C-Pd
C-Pg
C o p i e s of this map may be obtained f r o m t h e Bureau of Mineral Resources, Geology
and G e o p h y s i c s , Canberra, A . C . T . , or the Geological Survey of Q u e e n s l a n d , Brisbane
granodiorite;
minor
adamellite,