panterra geoservices inc. - China Minerals Mining Corporation

Transcription

PANTERRA
GEOSERVICES INC.
Applied geological studies for exploration and mining
14180 Greencrest Drive
Surrey, B.C., Canada
V4P 1L9
Phone 604-536-4744
MEMO
DATE:
September 9, 2009
TO:
J. Dadds, R. Barclay. M. Petrina
Hawthorne Gold Corp.
Suite 1580, 505 Burrard Street
Vancouver, B.C.
Canada V7X 1M5
FROM:
David Rhys
RE:
Cassiar Camp – summary of setting, style and exploration potential of gold
vein systems: preliminary report for discussion purposes
Introduction
This memo summarizes some key points from the recent on site geological evaluation of the
Cassiar property during late July and early August, 2009. A more comprehensive technical report
outlining geological observations, potential structural controls on mineralization, and potential
targets exploration areas will be prepared subsequently, after additional map review and further
examination of underground workings and drill core in upcoming site visits.
Structural setting of gold mineralization in the Cassiar area
• Gold mineralization in the Cassiar district occurs within the Sylvester Allochthon, which
comprises a mafic-sedimentary portion of the Slide Mountain Terrane that is affected by
regional greenschist-grade metamorphism (Nelson and Bradford, 1993). Within the Sylvester
Allochthon, mineralization is hosted by stacked, shallow dipping thrust panels of alternating
pillowed to massive mafic volcanic rocks and carbonaceous (graphitic) fine-grained
metasedimentary rocks, with local thin lenses of altered probable ultramafic sills. The shallow
dipping thrust faults which imbricate the sequence are likely early and related to easterly
directed, syn-accretionary thrust development during Mesozoic emplacement of the Sylvester
Allochthon on to siliciclastic strata of the Cassiar Terrane (Nelson and Bradford, 1993).
• Superimposed on the thrust faults are several phases of syn-metamorphic deformation
manifested by several generations of foliation that probably reflect ongoing progressive
deformation related to crustal thickening during and after accretion and imbricate thrusting of
Sylvester Allochthon lithologies. Ductile deformation is strongly partitioned into sedimentary
and altered ultramafic components of the sequence, which often contain intense foliation
development, while intervening panels of mafic volcanic rocks are often massive and show
only low strain. Highest strains are localized in contact areas between mafic and sedimentary
units, and along lenses of carbonate altered (listwanite) ultramafic sills, forming ductile high
strain zones which are probably superimposed on, and exploit the earlier thrust fault surfaces.
The earlier thrusting event, which is locally associated with sets of minor recumbent folds, is
here termed D1.
Cassiar project exploration
A: South end of Taurus tailings pond, view NE
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B: Near Boomerang prospect
Figure 1: Dominant lineation developed in the Cassiar Camp, illustrating geometry with respect to
quartz extension veins. A: Pronounced shallow dipping composite crenulation and stretching lineation dips
shallowly to the left (northwest) on foliation surfaces in altered mafic volcanic rocks. Joints which dip
steeply to the right locally contain quartz extension veinlets here Field of view approx. 5 m. B: Grey
carbonaceous phyllite from metasedimentary band between mafic volcanic units at the Boomerang prospect
at the northwestern end of the Taurus property area. The shallow dipping crenulation lineation (parallel to
pencil) is orthogonal to quartz extension veinlets which trend northeast and dip steeply. Quartz fibres in the
extension veins and in pressure shallows to pyrite porphyroblasts are parallel to the lineation. The geometry
of vein systems in the Cassiar area is linked to the orientation of this lineation.
• At least one, and often two dominant foliations are often recognizable in altered ultramafic
rocks and metasedimentary units, and are locally developed in mafic volcanic rocks in areas of
high strain, between, or on the margins of more massive low strain, shallow dipping mafic
volcanic units. The foliations are associated with structural events that overprint D1 thrust
faults and folds, described above, and are hence here coded as part of later events, here termed
D2 and higher. Gold mineralization probably formed late during, and is kinematically linked
with, these events. Earliest foliations (S2 foliation, defining D2) are generally close to or
parallel with shallow dipping bedding in the sedimentary units, and parallel to listwanite
carbonate-sericite (fuchsite/mariposite) altered ultramafic rocks. Intense areas of high strain
associated with the S2 foliations are particularly evident in listwanite and adjacent sedimentary
units in the Bain and Cusac areas defining probable shear zones that are up to several tens of
meters thick. The moderate to shallow dipping S2 foliation associated with the highly strained
areas around mafic volcanic contacts is affected by a later phase of generally steeply dipping,
northwest trending foliation (S3) which is associated with open folding of S1 and lithologic
contacts. Additional foliations are present also in areas of highly strained carbonaceous
sediments suggesting that further foliation-forming events occurred, including the local
development of a late, northeast-trending and generally steeply dipping crenulation cleavage.
• A northwest-trending, and shallow plunging composite stretching and intersection lineation is
developed at the intersection of S2 and S3 throughout the Cassiar gold camp (Figure 1). In
areas of high strain, the lineation is defined by the linear intersection of S1 and S2 foliations,
which is collinear with a stretching lineation that is defined by elongation of pillows, mineral
aggregates, and where present, stretched fragments in siliciclastic units. The lineation records
significant northwest-southeast stretching of the lithologic sequence, and is linked to the
orientations of extension and shear veins associated with gold mineralization. Shear bands and
minor shear zones in high strain zones in listwanite at Cusac and in the Bain working support a
Panterra Geoservices Inc.
D. Rhys, M.Sc., P. Geo.
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top to the northwest sense of displacement on S2 (D2) fabrics parallel to L3. Quartz-carbonate
fibres in mineralized sheeted extension veins are oriented parallel to the lineation, suggesting
that the vein opening vector corresponds with, and vein formation was coeval with the
formation of, the lineation.
• Metamorphic fabrics and quartz veins (see below) are cut by a set of east-west trending, steeply
dipping diabase dykes. The dykes locally intrude and follow vein systems, but are in turn cut
by post-mineralization brittle faults. Biotite lamprophyre dykes are also locally present and
have similar orientations and timing. Both types of dykes form significant magnetic anomalies
on airborne surveys (e.g., Wells, 2003), which locally obscure magnetic patterns associated
with lithologic distribution, alteration and syn-mineralization structures. The dykes provide
evidence for the relative timing of faults – faults which cut and offset the dykes are clearly
post-mineralization in timing, although could locally remobilize more semi-brittle earlier synmineralization structures.
• Late deformation comprises mainly brittle, chloritic to white clay gouge filled, fault
development. Faults observed typically trend north-northwest or northeast, the latter are
generally southeast dipping. Northeast trending faults typically have oblique slip southeast side
down (normal) kinematic indicators where observed, and result in apparent right lateral offsets
of veins, dykes and lithologic contacts in plan view consistent with the normal shear sense. The
faults locally exploit older, syn-mineralization structures (see below). North-northwest
trending brittle faults in the Taurus area generally have apparent left lateral offset (Wells,
2003). Existence of the previously emphasized “Erickson Creek Fault Zone” could not be
confirmed, but since no significant offset of lithologies is apparent along the length of it
projected trace, and faults within the fault corridor dominantly trend oblique to the northerly
trend implied, it is possible that corridor may not contain a continuous fault system, and even if
so, that faulting along its trace may be dominantly post-mineralization in timing. Further
interpretation of faulting patterns and relationships will be undertaken in future work.
Style and controls on auriferous vein systems
General styles and patterns
• Gold mineralization in the Cassiar district is typical in style of Orogenic (mesothermal) gold
systems globally, forming quartz extensional and shear veins with associated Fe-carbonatesericite-pyrite alteration. As with many other orogenic gold districts, veins in the Cassiar area
have pronounced lithological control and are developed primarily in rheologically competent
mafic volcanic rocks between weaker carbonaceous phyllite and listwanite horizons, the
contacts of which are affected by areas of high strain and shear zones.
• Vein systems in the Cassiar district are composed of two dominant styles:
a) Shear veins form continuous veins with strike lengths of tens to hundreds of meters long
that occur in minor shear zones are by far the principal source of previously mined gold
mineralization in the Cassiar district, and
b) Extension veins and veinlets are sheeted veins that typically trend east-northeast to
northeast with steep dips and which occur as haloes around, and long strike from shear
veins. The joining, and interaction of the two vein styles indicates that they are coeval.
Shear veins form targets for individual undergound mining, while larger sets of extension
veins, occurring peripheral, between or along strike from shear veins, may form targets for
bulk tonnage, lower grade mineralization. Combinations of shear and extension veins form
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the large low grade resource at Taurus, which with higher grade areas may be localized
within shear veins or in larger peripheral extension veins.
Diagrams illustrating typical veining patterns and evolution of shear veins and extension vein
arrays in orogenic gold systems which have comparable style to the Cassiar vein systems are
shown in Figures 2 and 3.
Figure 2: Block diagrams illustrating
geometry of extension and shear vein
arrays in Archean orogenic deposits,
from Robert (1990). The block diagrams
illustrate vein geometries in the SigmaLamaque deposit (12 million ounces Au) in
Val d’Or, Quebec. At top is an illustration
of reverse shear veins. Note the extension
veins (here termed “flat veins”) which fold
asymptotically as they approach the shear
veins, and the oblique fabrics in the shear
zones which host the veins (“fault fill” or
shear veins). Below is an illustration of
conjugate en echelon arrays in the system.
The association of shear and extension
veins, as at Cassiar, is common in orogenic
gold systems globally. In the Cassiar
district, however, the block diagram would
be tilted from this geometry, since extension
veins dip steeply, and σ1 would have been
steep instead of horizontal during vein
formation, reflecting the activity of low
angle thrusts in the Cassiar district.
Compare the above diagram to Figure 5B.
• Shear veins which have been historically mined the district areas comprise 0.2 to 8 m wide
quartz veins which mainly trend east –west to east-northeast with steep, generally northerly
dips. A subsidiary set of veins (e.g. Alison, Rory) in the Main (Erickson) mine trends northnortheast, forming networks with the east-northeast trending veins. At Taurus, west-northwest
trends of the shear veins predominate. The shear veins have often banded fill, with banding
variably defined by trails of disseminated sulphides (pyrite, tetrahedrite, sphalerite, chalcopyrite
observed most commonly), slip surfaces with fine-grained sulphide fill and seams of grey
deformed quartz, pyrite bands, and multiple parallel stylolitic carbonaceous (graphitic) black
ribbons (e.g. Sketchley, 1984; Figures 4-6). Tourmaline may be present in some ribbons and
cataclastic bands. Narrow foliated shear zones defined by cleaved, foliated wallrock may occur
on vein margins, or host thinner portions of veins. Bands of grey matrix cataclastic breccia are
locally common and record the position of principal displacement surfaces along the shear
veins (Figure 5). Fe-carbonate may occur as bands near vein margins or as late fill, the latter
associated with discrete late veinlets which may exploit earlier quartz veining. Style of shear
veins varies from well banded shear veins in the Table Mountain area in the south (Bain, Cusac,
Vollaug, Main Mine, Camp veins) to more massive quartz veins with often disseminated to
massive pyrite selvages in the north at Taurus. The changes may reflect differing host rock
controls and degree of displacement on the shear veins in the two areas, as is discussed below.
5
Competent unit
1
Sh
Boudinage
A. Extension vein array
ea
r
Less competent unit
ve
in
Dominant Foliation
C. Shear vein development
Early quartz
extension vein
1
Sh
e
B. Sigmoidal vein array
Younger extension
veins
ar
ve
in
D. Shear vein, new extension veins
Figure 3: Diagram illustrating stages in the development of a sigmoidal extension vein array and shear vein
system. The sequence is analogous to that observed in systems at the Main Mine and Cusac areas in Cassiar, which
would represent a plan view of the development of a sinistral-normal shear vein system; Ball (1985) shows similar
diagrams. Extension vein arrays typically evolve from an en-echelon array of early extension veins (A), through
gradual deformation into sigmoidal shapes (B) with shear movement along the core of the array. Eventually, the
original extension veins may become partially (C) or fully (D) transposed into the shear zone, and a continuous
shear vein may propagate along the shear zone. Later phases of extension veining may be superimposed onto the
forming shear vein system (D). The vein shapes and geometries provide excellent shear sense indicators,
predictable oreshoot geometries, and demonstrate syn-tectonic formation of the vein systems under contractional
deformation conditions.
• The steeply dipping northeast to north-northeast trending extension veins and veinlets in the
Cassiar area are consistently oriented at high angles, or orthogonal to the L3
stretching/intersection lineation. These veins, which have been referred to as “gash veins” in
previous reports, have blocky quartz fill locally with fibrous quartz-Fe-carbonate +/- tourmaline
selvages. The fibrous quartz-carbonate +/- tourmaline fill is often paragenetically early and on
vein margins. Quartz-carbonate fibres are aligned parallel to L3 and usually perpendicular vein
walls, recording extensional opening of the veins parallel to the fibres. Extension veins vary
from veinlets less than 1 cm thick with strike lengths of a few tens of centimeters, to larger
veins several tens of centimeters in thickness with strike lengths >15 m long; most are 1 to 5 cm
thick, and 0.5 to 3 m in length, with lenticular form. They lack peripheral shear zones. The
orthogonal orientation of extension veins to the L3 northwest-southeast trending lineation and
the fibrous to prismatic mineral growth of quartz, Fe-carbonate and locally tourmaline
perpendicular to vein walls and parallel to L3 suggest that the veins accommodated purely
extensional opening in response to northwest-southeast stretching (extension) parallel to L3.
Their overall style lenticular forms, and extensional nature are typical of formation as hydraulic
fractures. The extension veins are auriferous and may contain visible gold, but gold grades are
generally much lower and continuity of mineralization less than in shear veins, with the
extension veins most likely to be mineralized in areas where pervasive carbonate-pyrite
alteration surrounds them and forms broad zones. Shear veins laterally and vertically may
terminate in sheeted to sigmoidal sets of extension veins, which may be en echelon and step
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along the projected strike extent of the shear vein, so extension vein arrays may form a vector
to the along strike development of shear veins. At the Taurus Mine, an abundant set of
extension veins at the termination of a principal shear vein constituted a small zone of bulk
mineable ore (D. Gunning. pers. comm., 2009).
• Distinguishing shear veins from sets of extension veins during core logging will be important in
modeling the continuity of mineralization in cross sectional or wireframe modeling, since each
implies a different mineralization style and different degrees of continuity. Shear veins may
laterally dissipate in sets of extension veins, or may along strike continue as narrow semi-brittle
shear zones with surrounding carbonate-sericite alteration and pressure solution foliation
surfaces. Identification of such narrow shear zones consequently is also important, as these
laterally or vertically could become shear veins where appropriately oriented, or where they
pass into rheologically favorable host rocks.
• In addition to the volcanic hosted shear and extension vein styles, thick white quartz veins up to
several meters thick with shallow to moderate dips are localized along or at shallow angles to
contacts in listwanite and at mafic-sedimentary contacts at Table Mountain, and thick veins
occur often along mafic-sedimentary contacts and moderate dipping carbonaceous faults at
Taurus. These are fault hosted shear veins which locally branch or curve into auriferous shear
veins in the adjacent mafic sequence, but which contain generally low or erratic gold values,
although there is potential for these also to contain oreshoots, and they may be spatially
associated with disseminated pyrite mineralization. They are discussed further below.
A: View west of Bain vein in decline
B: 20 cm wide sample of Vollaug vein
Figure 4: Photos illustrating internal style of
shear veins in the Table Mountain-Cusac area.
A: West Bain vein exposed in main Bain decline.
The vein here is >1 m thick with banding defined
by grey quartz with minor cataclastic breccia
parallel to vein walls. In the upper right, a 20 cm
wide shear zone with apparent normal oblique
fabrics occurs in tan altered wallrock adjacent to the
vein. B: Stylolitic black carbonaceous (graphitic),
pyrite and carbonate-bearing ribbons create banding
parallel to vein walls. C: Composite banded shear
vein in new underground development on the Bain
decline, showing white quartz (left), central grey
pyritic quartz and breccia, and at right grey quartz
with bands of late yellow-orange Fe-carbonate.
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C: View east in lower Bain decline
A: Bain decline near lower end. View up at back, field of view approximately 3 m.
B: Detail of lower central part of Photo A
Figure 5: Shear-extension vein system
intersected by new development in the Bain
underground workings. The photos are taken in
a remuck/sump near the lower end of the decline
as of August, 2009. These are views up at the
back, so apparent shear sense is reversed from if
the view was in plan. A: In the photo above a
west-northwest trending banded shear vein
(below) is fringed by northeast trending white
quartz extension veinlets which splay off it, and
which in the upper part of the photo form a
sigmoidal vein array (compare to Figure 3).
Extension veins are developed at high angles to
northwest trending foliation (runs from lower left
to upper right) in altered wallrocks. Vein
geometries and sigmoidal shapes in the array
support a dextral (right lateral) shear sense in this
view upward at the back, which is left lateral in
plan view, typical of other shear veins in the
Table Mountain area. B: Detail of lower central
part of photo A showing dark banded shear vein,
and sigmoidal shapes of extension veins as they
join it.
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A: View up at the back, field of view apprx 4 m
B: View up at the back, field of view apprx 2 m
C: View of decline wall looking up dip to north
D: View up at back, field of view approx 0.5 m
Figure 6: Shear vein-extension vein systems in the Bain decline, illustrating structural style. The veins
have classic textures of orogenic gold systems. A and B: These images illustrate the same vein system which
crosses the decline just east of UTM NAD83 461050E. In A, the vein system comprises a series of en echelon,
locally sigmoidal shear veins which surround a minor, east-west trending and steeply dipping slip surface in the
upper part of the photo. In B, in an electrical bay, the vein system comprises a central shear vein which is
joined by sheeted extension veins that extend into the adjacent altered wallrocks. Note the sigmoidal shapes to
some of the extension veins where they splay off the shear vein at left. In both images, the vein geometry and
sigmoidal shapes indicate an apparent right lateral shear sense, which in plan view would be left lateral
(sinistral) since the shear sense is inverted when looking up at the back. C and D: Texture of minor shear
veins which have been intersected in the Bain decline east of UTM 460950E. Banded in C is defined by
diffuse bands of sulphide aggregates + altered wallrock breccia fragments, and by sulphide-grey quartz slip
surfaces. In D, note banding and mottled texture caused by lenses of altered wallrock and grey quartz-sulphide
fragments and lenses.
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Veins in the Table Mountain area (Main Mine, Vollaug and Cusac)
• The dominant set of set of west to east-northeast trending shear veins in the Table Mountain
area as observed during this study and determined by previous structural studies shows
consistent kinematic indicators which suggest that they accommodated top to the northwest
displacement during vein formation (Ball, 1985; Ey, 1986, 1987; Anderson and Hodgson,
1989). Shear sense indicators include a) offsets of lithologic contacts (mafic-listwanite and
mafic-sedimentary contacts), which are consistently offset down to the north and where strike a
slip component is determinable to the left (sinistral), b) the presence of oblique foliation
development, shear bands (extensional duplex), and oblique internal cleavage is associated
minor shear zones that host shear veins, and c) sigmoidal extension vein arrays that occur in
sets along strike from, or in arrays parallel to shear veins (Figures 5, 7) and overall right
stepping of vein systems in en echelon steps (Figure 6), which also support left-lateral
(sinistral)-north side down displacements, and d) the overall geometry and relationship of
extension veins which join and splay off the shear veins (Figure 6A, B), also geometrically
imply a compatible shear sense as other shear sense indicators. The implied slip vectors are
consistent with the northwest-southeast trend of stretching lineations, and suggest that veining
may have formed in second and third order minor shear zones in response to top to the
northwest displacement along lithology-parallel shear zones that are localized along listwanite
and mafic-sedimentary contacts, in a setting of bulk northwest-southeast stretching (extension)
and vertical shortening, consistent with a low angle thrust setting (see Figures 8C, D and 9 for
examples). Overall style of veining is semi-brittle, defined by brittle textures such as the veins
themselves and associated cataclastic breccias, and by the associated development of narrow
ductile shear zones on their margins and formation of sigmoidal extension vein arrays.
A: Detail of vein near 14 level portal
B: Detail of Maura vein northeast, 28 level
Figure 7: Photos of underground plan maps from parts of the Main Mine. Drift width is approximately
5 m in both, and quartz veins are colored red. In A, an east-west trending shear vein has well developed
sigmoidal peripheral extension veins indicative of apparent sinistral (left lateral) shear sense. In B, at the
eastern end of the Maura vein, similar sets of sigmoidal extension veins also splay off the main vein. Note
the steps and bends in the vein. Structural style and kinematics are compatible with those seen in the Bain
area during this study.
• Shear veins in the Main Mine, at Cusac, and in the Bain undergound workings displays normalleft lateral offsets of lithologic contacts on the margins of the mafic volcanic sequence often in
the order of several tens of meters (Figure 8B). However, although displacing the contacts,
several exposures and cross sections through veins in the Main Mine suggest that the minor
shear zones which host the veins, and veins themselves refract upward and shallow, becoming
parallel or close to the orientation of the dominant shallow dipping foliation along the contact
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area. Where they are developed in listwanite or sediments above the mafic volcanic sequence,
veins may have only low grade or may not be auriferous, but where they steepen and penetrate
downward into the mafic volcanic sequence below, gold grades increase, particularly at or just
below the point of inflection where the veins cross the contact from listwanite to mafic
volcanics below. These patterns suggest that 1) minor quartz vein filled shear zones which are
parallel to, or obliquely cross the dominant foliation in the overlying listwanite may be
traceable downward into mineralized veins below, and 2) that offsets of the lithologic contacts
along minor shear zones lacking significant veining may project downward into underlying,
more steeply dipping shear veins which lie deeper along the offsetting shear zone where it
refracts to steeper dips as it passes into the mafic volcanic sequence below; in such cases, the
most prospective shear zones would be those which have orientations that are compatible with
known shear veins elsewhere in the camp. Modeling of the mafic volcanic and listwanite
contacts, and specifically offsets and displacements in the contact, may consequently aid in
targeting for additional vein systems, as has been noted by previous workers (e.g. Ball, 1985;
Ey, 1987). The largest offset known is spatially associated with the Sky vein, suggesting that
the shear zone hosting this vein system may have significant lateral an vertical continuity and
providing much room along its trace for the development of oreshoots.
• Highest grades and greatest gold production have been obtained in individual veins in areas at
and immediately below the listwanite contact in underlying basalts, making the upper few tens
of meters of the contact, particularly at Cusac, the most prospective part of the mafic sequence
to date. Veins locally dissipate downward from the contact area after a few tens of meters in
some historically mined veins. However, larger veins with greatest offset and greatest tonnage
potential have the potential for much greater continuity, and also may form downward en
echelon steps where a new vein may develop beneath the termination of a higher vein,
providing potential beneath known veins where not currently tested. In a similar pattern, veins
may terminate at a weaker unit (e.g. a band of listwanite in mafic volcanic) but re-appear again
in mafic units below where lithologies are stacked. Such patterns are seen in the Jennie and
Maura veins in the Main Mine, which may form discrete veins with a single vein system that
form periodically downward as displacement is accommodated across progressively deeper
competent mafic units.
• As is typical of vein system in other orogenic districts and illustrated by the Main Mine, vein
systems form closely spaced networks which define areas of high structural permeability and
fluid flow. The minor shear zones which host the shear veins in these areas of more intense
veining on Table Mountain collectively accommodate strain across the more rigid, competent
mafic volcanic units while the surrounding weaker lithologies are affected penetratively by high
strain and deform in a ductile manner. Deformation of the hosting rock sequence as a whole is
one of structural thinning during foliation formation and shear zone formation, and the vein
systems occur in second and third order minor shear zones which effectively form spaced areas
of large scale boudinage of the rigid mafic units where minor shear zone formation
accommodating strain is localized, and which forms a permeable network of favorably oriented
fault surfaces for fluid flow and vein formation. Such patterns of host rock control and
deformation induced structural thinning of competent rock units are extremely common in, and
often form the dominant control on, vein localization in orogenic gold districts.
• Undergound development in the Bain decline has recently intersected a series of narrow banded
steeply dipping to moderate south dipping and east-west trending shear veins to the north of the
West Bain vein (Figures 5, 6). The shear veins are surrounded by a broad zone of tan-grey
carbonate-sericite alteration and fringed by sets of northeast trending quartz extension veins,
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some of which form sinistral (left lateral) en echelon vein arrays. The abundance of veins here
and intensity of associated alteration suggest that these veins form part of a larger vein system
which has the potential to host additional veins that are comparable in style to the Bain vein
system itself. Individual veins in this set could laterally or vertically become more continuous
and wider shear veins, or the veins collectively could coalesce into a larger vein. Undergound
drill testing of this vein set is recommended using the decline area, or drill cutouts from it as a
platform. It may not have been tested before due to the often steep southerly dip of veins
within it, which are parallel to many drill holes, its position separate from the main Bain vein
system. Style of and kinematics of veins in this set are typical of extensions of previously
productive vein systems in the Table Mountain area, including the West Bain vein system,
which at the eastern end of underground development along it, breaks into en echelon and
sigmoidal vein arrays.
• In addition to the veins intersected in the Bain decline, a significant southeast side-down,
northeast trending shear zone in listwanite intersected at the lower end of the ramp contains
quartz veins and narrow grey breccia veins along slip surfaces (Figure 10), suggesting a synmineralization timing. This could host veining where it passes into underlying mafic volcanic
rocks, or form a controlling structure to other veins which may splay off it. Potential exists too
for further extensions of the West Bain vein system along strike and down dip since it is hosted
by a shear zone with significant displacement suggesting that it should have good continuity,
and potential to host additional continuous shear vein segments where it is appropriately
oriented.
• In the area of the Cusac portal, and to the north in the surface exposures of the Fred, Dino and
Hot veins, a thin veneer of listwanite and carbonaceous sedimentary rocks occurs over the
mafic volcanic rocks. Being close to the contact area, offsets of the listwanite-mafic contact are
evident where veins project to surface, particularly in the area of the Fred vein, where >15 m of
south side down displacement across the vein juxtaposes highly strained listwanite and a thin
remnant of the base of the overlying carbonaceous units on the south against massive mafic
volcanic rocks to the north of the vein (Figure 8B). Similar quantities of displacement are
suggested on the Hot vein to the north, but with north side down displacement juxtaposing
carbonaceous sediments to the north against mafic volcanic rocks to the south. Widespread
carbonate alteration and common surface showings of veining in the limited outcrops that are
exposed suggest that this entire area extending from the Hot vein in the north to the Bain
underground workings to the south, has very high potential for the discovery of additional shear
veins that could form a network like that seen in the Main mine. A review and compilation of
underground and drilling data for this area is recommended, including re-examination of older
drill core to identify areas of prospective alteration, high vein density, and possible shear zones
which could host or control veins is recommended. Modeling of the ultramafic-mafic and
sedimentary-mafic contact surfaces is recommended to identify offsets and deflections that
could reflect the position of veins at depth.
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A: Erickson creek, foliated ultramafic
B: Fred vein pit, view west-southwest
C: Fred vein pit access ramp, view east
D: Pit north of Cusac portal, view north
Figure 8: Photos of structural features associated with veining at and along listwanite contacts in the Main
mine and Cusac areas. A: Strongly foliated talc-chlorite-carbonate altered ultramafic outcropping along Erickson
Creek at the contact between mafic volcanics and carbonaceous phyllite. Note strongly foliated nature, and the
abundant quartz veinlets, both crosscutting and parallel to foliation. B: Fred vein pit, looking west. The vein prior
to mining was steeply dipping and ran through the right center part of the image along the pit. In the footwall of the
vein (right) are mafic volcanic rocks, while the hangingwall of the vein (left) comprises dark grey shallow dipping
carbonaceous phyllite (upper part of exposures) overlying pervasively fuchsitic carbonate altered listwanite below
(reddish weathering). The juxtaposition of these lithologies across the vein suggest more than 15 m of apparent
south side down displacement across the vein, potentially conjugate to the displacement shown in C. C: Carbonate
altered fuchsitic listwanite in the access ramp to the Fred Vein pit is capped by a thin band of dark grey carbonaceous
phyllite (above), and is affected by multiple moderate north dipping shear zone slip surfaces (dashed blue lines) with
top to the north displacement. Black dashed lines in the inset show dominant foliation trace in the listwanite. Note
back-rotation of the foliation on the slip surfaces, and drag of the quartz veins (red in inset) into the slip surfaces,
compatible with the north side down shear sense. D: Minor pit north of the Cusac Portal exposes listwanite with a
shallow dipping shear vein that is joined in its hangingwall by moderate to shallow northwest dipping extensional
veins. The overall geometry supports a top to the northwest transport direction on the shear vein, with dilation of the
hangingwall veins in response to displacement along it. Photos C and D may are representative of vein and shear
zone patterns observed in the listwanite throughout the area, and convey the relationships of shallow dipping shear
zone surfaces in the listwanite to the development and geometry of auriferous quartz veins.
13
Figure 9: Vein exposure illustrating possible larger scale controls on vein development in the Cusac
area. Host rocks are grey carbonate-sericite altered mafic cherty sediments in upper parts of the mafic
volcanic unit at Bain. The vein system is exposed in the sump/remuck near the current lower end of the
Bain decline. At lower right, steeply dipping extension veins form a classic horsetail structure at the upper
termination of a shear vein which extends downward below at far lower right; veins are shown in red. The
geometry is of a south (right) side down apparent shear sense with displacement on the shear vein
accommodated in part by dilation of the extensional veins. At upper left, and shown in detail at lower left,
(blue in the inset) is an approximately 10 cm thick Fe-carbonate-rich shear zone which has top to the south
(top to the right in this view) internal shear sense indicators, and which at its south end terminates,
branching downward into a more steeply dipping narrow shear zone and the vein system itself. This
illustrates the transfer of displacement from shallow dipping shear zones into underlying vein systems, such
as is seen frequently along the areas of the ultramafic-mafic contact in the Table Mountain area.
A: View north of wall, field of view approx. 3 m
14
B: Detail of center of A, view north
Figure 10: Shear zone in listwanite near current lower end of the decline between the West and East
Bain veins. The shear zone comprises multiple northeast trending and moderate to steep southeast dipping
slip surfaces in carbonate-fuchsite (green) altered ultramafic rocks. In A, several slip surfaces which dip to the
right are visible, including quartz veins vein filled slip surfaces at far upper right (just visible in corner) and
center right, a thin black surface at center left, and at lower left a fourth occurs at between the orange (rusty)
wallrock ad green-tan listwanite to the right. The orange unit at lower left is composed of tan altered mafic
volcanic rocks which are in tectonic contact with the listwanite above, the latter which is downdropped to the
southeast on the mafic unit with apparent normal shear sense. In B, a detail of A, well developed shallow
dipping foliation (S surfaces) and shear bands occur above the hammer on both sides of the slip surfaces,
implying a normal > dextral shear sense that is compatible with the offset of the listwanite onto the mafic
volcanic unit below. Grey quartz with fine-grained pyritic disseminations fills the slip surface in B. The
presence of quartz along the slip surfaces and the ductile style of deformation suggests that the shear zone is
syn-mineralization in timing and may control the development of vein systems along strike and down dip. The
lowermost slip surface in A and other slip surfaces in the shear zone have been remobilized by clay gouge
during later brittle faulting, the late fault strands of which are significantly water-producing.
Taurus mineralization
• Veining patterns shear sense in shear vein systems in the Taurus area are comparable to those in
the Main Mine and Table Mountain area to the south, although shear veins have generally more
east-west to west-northwest trends. The Taurus veins have a higher proportion of extension
veins – some of which are large and laterally continuous -- as the principal source of gold than
in other parts of the district. Underground maps of the Plaza and Sable workings, as well as
some trench exposures show that shear veins are internally composed of right stepping en
echelon extension veins which step to the northwest (Figure 11A), and which alternate with
more continuous west-northwest trending veins that are probably shear veins. In drill core, and
currently being intersected in the stripped pit, narrow shear zones which vary from tens of
centimeters to locally several meters thick and have stylolitic pressure solution foliations which
weather recessively and rusty (Figures 11B to 11D) are present which contain lenses of quartz
along strike. Since these shear zones are mineralized, are often quartz-bearing, and are spatially
15
associated with sets of extension veins, they likely represent controlling structures to the vein
systems. Higher extension vein densities may occur peripheral to them, and shear veins could
locally occur along them, making them important features to track in establishing
mineralization continuity at Taurus. Map patterns of veins suggest that at a larger scale
individual shear veins may also be en echelon and right stepping, along predictability to the
position of potential additional veins if one vein terminates.
• As with the Table Mountain veins, at their terminations the Taurus shear veins may terminate in
sets of en echelon extension veins along strike. Overall vein geometries of veins at Taurus are
consistent with the left-lateral/normal shear sense that is evident in shear veins at Table
Mountain (Main Mine, Cusac, Bain). Potential conjugate, dextral and northeast striking shear
zones/veins could also be present but will probably subsidiary to the west-northwest trending
dominant set, as they are locally at Table Mountain. The rare presence (Panteleyev et al.,
1997), but general lack of sigmoidal veins and less evidence of displacement along the shear
veins (banding and cataclastic textures are much rarer, peripheral shear zones are more weakly
developed) suggest a more brittle style of the Taurus veining than in other parts of the camp,
which is consistent with the higher abundance of extension veins in proportion to shear veins in
this area, defining the large low grade resource. Carbonacous ribboning, however, is reported
in the #3 vein shear veins in the Taurus Mine, comparable to the Main mine (Hooper, 1984).
• As with the Table Mountain area, shear veins and shear zones hosting gold mineralization may
emanate off major shear zones and areas of high strain localized along the underlying maficsedimentary contact. Broughton and Masson (1996) report local thin lenses of listwanite and
ultramafic units at this contact, as is seen at Table Mountain. However, in the Taurus area case,
since the mafic units overly the rheologically weaker carbonaceous phyllites below, the basal
contact of the mafic unit may be highly favorable for the localization of more abundant veining
and higher gold grades in veins as is seen in the marginal portions of the mafic volcanic
sequence at Table Mountain and Cusac.
Figure 11 (following page): Taurus area mineralization styles. Photos B and C are from K. Whitehead.
A: 88 hill west stripped vein exposures, looking northwest, showing en echelon right stepping quartz
extension veins which steep from lower right to upper left in a vein array. B: Similar field of view looking
northwest in north part of pit area stripped for the bulk sample southwest of the Sable underground
workings. A rusty, oxidized shear zone at center trends northwest parallel to the direction of veins and is
fringed by east-west trending extension veins at left and right. Discontinuous quartz occurs along the shear
zone. Vein geometries are compatible with sinistral (left lateral displacement along the shear zone with
formation of extension veins in response. C: Detail of shear zone in photo B showing rusty central shear
zone at center right, probably after altered pyrite, and extensional veins which branch off at left. D: Quartzbearing shear zone with stylolitic pyritic, chlorite-bearing slip surfaces in tan sericite-carbonate altered
mafic volcanic rocks, 88 Hill area from drill hole TA09-14, between 73 and 74 m. The deformed quartz
lenses and disseminated pyrite indicate that this is a mineralized, likely vein-controlling structure which
along strike or down dip could host a more continuous shear vein. Such shear zones, with their high pyrite
content, weather recessively in outcrop exposures to red soil Fe-rich friable subcrop. E: Quartz extension
vein has fibrous black tourmaline on its margins which is most abundant in clots. F: Sheeted northeast
trending and steeply dipping quartz extension veinlets in rusty weathering carbonate-sericite-pyrite altered
massive mafic volcanic rocks. This is typical of exposures of extension vein sets in the Taurus area,
although this exposure is in the area of the Newcoast veins in a roadcut along the Cassiar highway.
16
A: View northwest
B: View northwest
C: View northwest, detail of B
D: TA09-14, between 73 and 74 m
E: Detail of vein in bulk sample pit
F: View northeast along highway roadcuts
Figure 11: see captions on previous page
17
• At Taurus, like the Table Mountain area, given the stacked nature of shallow dipping mafic
units which host the veins, there is potential for additional favorable mafic volcanic host rocks
beneath the carbonaceous, graphitic phyllite unit that bounds the vein systems below.
Broughton and Masson (1996) suggest that the carbonaceous phyllite beneath the Taurus mafic
host rocks may be as thin as 70 m, so if so thee may be potential in underlying shallow dipping
imbricate thrust lenses and bedded mafic units for additional veins below.
• Other targets in the Taurus area, which include the main Taurus, Plaza and Highway/Taurus
West areas, also have similar character in outcrop exposures and published descriptions as the
88 Hill – Sable area. Potential consequently exists to identify more continuous shear veins and
mineralized shear zones in areas not previously mined in these areas which may lie within areas
of higher extension vein density. Alteration mapping suggests that some of these areas lie in
broad east-northeast trending corridors that may trend for several kilometers, suggesting the
potential for multiple en echelon shear veins that are distributed along strike within them.
• In addition to the vein styles of mineralization described above at Taurus, drilling and
underground development at the Taurus mine has intersected areas of pervasively disseminated
fine-grained pyrite which is auriferous, defining a style of pyritic replacement mineralization.
Several drill hole intercepts of this style are present to the west of 88 Hill in what is termed by
Broughton and Masson (1996) as the Taurus West Shear Zone. Here, disseminated pyrite
mineralization occurs in tan carbonate-sericite altered mafic volcanic rocks over widths of
several meters and locally up to 30 m. Mineralization comprises 5 to 40% disseminated finegrained pyrite in altered mafic rocks. These pyritic zones are locally intensely foliated high
strain zones which define probable shear zones peripheral to a large partially quartz-filled,
carbonaceous (graphitic), and moderate east dipping fault zone at Taurus West. Similar styles
of mineralization are reported adjacent to the basal shear zone contact with underlying graphitic
phyllites that lies at the base of the shallow dipping mafic unit in the Taurus Mine (Gunning,
1988). The mineralization may represent a pre-quartz veining style of pyritic replacement
mineralization that occurs in, and adjacent to significant shear zones, and could be comparable
to pre-veining early styles of pyritic mineralization seen in other orogenic gold districts (e.g.
Wells-Barkerville: see Rhys et al., 2009; and Holloway in the Abitibi). Grades of up to 8.3 g/T
Au within an interval of 3.0 g/T Au over 26.45 m occurs between 224.0 and 250.45 m in drill
hole T95-13 which is the best intercept, and which also includes an intercept of 4.51 g/T Au
over 7.0 m from 225.0 to 232.0 m. Drill core re-logging and modeling of this mineralization is
recommended to assess its exploration potential. Other quartz vein filled shear and fault zones,
such as those seen to the south at Wings Canyon (see below), may also have the potential for
similar peripheral styles of replacement pyritic mineralization.
• In addition to the Taurus extension and shear veins, as discussed above larger white zones of
quartz veining occur in moderate to shallow dipping fault zones in the Taurus area, including
the fault hosted vein system in Taurus West adjacent to which the replacement pyrite
mineralization is developed, as is described above. The largest area of development of fault
hosted quartz veins is along Quartzrock Creek in Wings Canyon, one kilometer south-southeast
of the Sable portal area. Here, east-west trending and moderate south dipping quartz veins
which are hosted by mafic volcanic rocks which locally exceed 10 m in thickness comprise 10
to 40% of the outcrop exposure for several hundred meters of strike length along the creek
(Figure 12), in a true cross section crossing the vein system. In southern portions of this vein
system, vein orientations are highly variable, suggesting north-northeasterly trending fault
hosted veins may intersect the east-west trending set. Local occurrence of carbonaceous bands
in some of the veins (Figure 12C) suggest either entrainment of carbonaceous phyllite lenses
18
along the vein system, or hydrothermal graphite presence, as is seen in Table Mountain veins
(Sketchely and Sinclair, 1991). Previous sampling here indicates that the veins carry
anomalous and low grade gold mineralization, although economic grades have not yet been
identified here. The style of veining is comparable to large, low grade to barren white quartz
veins that occur along major faults in some orogenic gold districts such as the Mother Lode
Belt of California. In such areas, productive, auriferous high grade vein systems may occur
adjacent to, or between the larger, more barren quartz veins. In such cases the large vein
system may represent a major fluid and structural channelway for hydrothermal fluids, which in
itself does not trap mineralization, but which may control and localize mineralization in vein
systems and replacement zones in adjacent wallrocks which splay off, or occur in nearby
adjacent zones. The Wings Canyon veins project eastward through areas of poor exposure with
isolated exposures of altered outcrop for several kilometers to the Rich vein area, suggesting
that the areas may be linked and have the potential for veining in between over a large strike
length. Alteration also projects westward, although its extent in that direction is poorly defined
as well by limited exposure.
A: View west-SW of west Canyon wall
B: View west-SW; 20 m approx view
C: View south, south end of canyon
Figure 12: Wings Canyon quartz vein
exposures. A and B: View west of west wall of
the southern parts of the Canyon looking across
Quartzrock creek. Quartz veins locally >20 m
thick (A) dip moderately to the south and form 25
to 60% of outcrop exposure in the canyon. In B,
a large southwest dipping quartz vein at upper left
has steeply dipping quartz extension veins in its
footwall; these smaller veins may have higher
potential to host mineralization than the larger
veins. C: Southeast dipping thick quartz shear
vein in southern parts of the canyon has well
developed carbonaceous bands which make it
more prospective than more barren veins that are
present here.
19
Associated alteration with veins in the Cassiar area
• As with other orogenic gold districts, vein systems in the Cassiar camp are surrounded by pale
grey (when fresh) to tan/orange-yellow weathering Fe-carbonate-sericite-pyrite alteration
(Figure 11F). The alteration may surround and extend outward for a few meters on individual
shear veins and focused sets of extension veins, or be more pervasive over widths of tens of
meters in areas where closely spaced vein networks are developed. Envelopes of disseminated
pyrite which extend several centimeters to tens of centimeters around veins, particularly in the
Taurus area, also expand the total area of mineralized material beyond the limits of the veins
themselves. The very hard nature of the alteration may suggest the presence of K-feldspar and
Na-cobaltinitrite staining of selected samples will be undertaken to assess its presence; Wells
(2003) reports secondary K-feldspar in some samples. Outer alteration is chlorite and calcite
dominant with or without epidote, so the transition from calcite to Fe-carbonate forms an
important mineralogical change in assessing proximity to vein systems. Clay alteration
associated with late brittle faults overprints syn-mineralization alteration assemblages and is
previously reported distal to some veins in the main mine (e.g. Sketchely and Sinclair, 1991),
but where observed during this study it is late fault related and not part of the primary alteration
assemblage.
• In addition to the alteration styles noted above, outer propylitic assemblages peripheral to areas
of carbonate-sericite alteration in the Cusac area contain hematite, both as specularite forming
irregular breccia fill and vein networks (surface outcrops north of the Cusac portal), and as
pervasive fine-grained hematite which affects, and provides a red tint, to volcaniclastic and
cherty sediments in the hangingwall of the West Bain vein in the Bain decline. Specularite was
also locally observed in drill core in propylitic assemblages in the Taurus area. Outer Fe-oxide
bearing alteration to inner Fe-carbonate sericite is common in some orogenic gold systems (e.g.
Hollinger, Kirkland Lake), and may provide a vector to identifying vein hosting zones of inner
carbonate-sericite alteration. The outer oxidized zones may also form positive magnetic
anomalies when magnetite is present, ringing magnetically low areas of the pyrite-bearing
alteration associated with the vein systems.
Comparisons to orogenic gold districts
• Gold bearing vein systems in the Cassiar camp show many characteristics consistent with their
classification as an orogenic (mesothermal) gold system. These include 1) a geometrical and
temporal link to late stages of syn-metamorphic deformation in the region under greenschist
grade conditions, including consistent vein orientations with respect to the camp scale,
northwest-southeast trending stretching lineation, 2) the semi-brittle vein style and association
with broad sets of extensional veins formed as hydraulic fractures, 3) spatial association of
mineralization with shallow dipping high strain zones in thrusts which form first and second
order shallow dipping regional structures which were active symetamorphically, and 4)
mineralogical consistency in metamorphic grade and Fe-carbonate-sericite-pyrite alteration
styles typical of the CO2 + K –bearing hydrothermal fluids associated with orogenic gold
deposits. The Cassiar area differs from many orogenic gold districts in that the first and second
order structures associated with the vein systems are shallow dipping thrusts as opposed to
having steep dips, but this shallow dipping geometry is also present in some other orogenic
districts including the Cariboo Gold district (B.C.), Laverton (Western Australia) and Macraes
(New Zealand). The shallow dipping orientation of the associated first and second structures is
not a valid criterion for exclusion of the Cassiar area from the orogenic deposit class, as field
evidence suggests that the whole system is formed during conditions of orogenesis associated
20
with low angle shear zone (thrust) development. The shallow dipping thrust faults represent
part of a crustal scale set of terrane controlling and bounding structural features that are
comparable to major shear zones associated with orogenic gold districts globally.
• The vein systems in Cassiar form part of a hierarchy of syn-mineralization structures, as typical
of other orogenic gold districts. First order structural control is the overall shallow dipping
imbrication of the Sylvester Allochthon on faults and shear zones with major displacement,
followed by second order shear zones internal to the Sylvester Allochthon like those localized
along sedimentary and ultramafic (listwanite) contact areas, to third and forth order control
along the minor shear and fault zones which splay off the second order structures and host the
shear veins.
• As an orogenic gold system, potential lies throughout the Cassiar district for the development
of economic veins systems where favorable structural settings and areas of rheological contrast
are developed. Overall known footprint of the district is already large, with showings present
throughout Hawthorne’s large Cassiar property. Potential also extends beyond the limits of the
Cassiar property illustrating the size of the district, for example outcrop exposures on the haul
road of the former Cassiar asbestos mine to the northwest of the property contain vein shear and
extension vein systems of similar geometry, kinematics and style as the main gold district
(Figure 13), indicating potential extends at least to this area. These veins at Cassiar are also
spatially associated with large northwest-trending, lithology parallel white quartz veins that
probably represent second order fault control to the third order minor shear zones which control
the vein systems. These large veins may be comparable to the contact hosted veins in the main
gold district. Ongoing property scale compilation, mapping and modeling of the district,
particularly in areas of lithologic variability and interleaving of units of differing rheological
contrast is recommended. As with other orogenic districts, a broad zonation which is evident at
Cassiar from Au-rich veins in the core of the district to more Ag-Sb rich veins in peripheral
portions can be used as a broad scale vectoring for target selection.
• In other orogenic gold districts, areas of veining networks which mark locations of deformation
induced structural thinning of vein hosting lithologies are also commonly repeated in the
direction of extension, which in Cassiar is the L3 northwest-southeast trending stretching
lineation. As with other mining camps, sets of veins such as the main mine can repeat along
trend in the lineation, resulting in chains of vein systems which collectively are distributed
periodically along the trend of the lineation. Such patterns are pronounced for example in the
Wells-Barkerville camp, where sets of veins in the Cariboo Gold Quartz Mine repeat along
strike along the shallow northwesterly lineation plunge; these deposits are of similar age and
setting to those in Cassiar. In the Cassiar area, the northwest-southeast trend of the dominant
lineation suggests similarly that vein systems may repeat along that orientation. Overall vein
patterns do support such repetition, since vein systems are distributed in crude north-northwest
trends (e.g. Vollaug through Main Mine, Pete to Cusac, Newcoast Veins to Taurus). If these
represent real trends, then other veins may lie along them, including in areas to the northwest
and southeast of known veins where exploration may not have tested. These patterns, and
similar patterns in other orogenic gold districts globally, suggest that the orientation of the
lineation may exert as primary control on the repetition of vein systems, in conjunction with the
location of syn-mineral first and second order faults. As is discussed above, little field
evidence was found for control of mineralization by a northerly trending set of steeply dipping
faults, since field relationships observed during this and previous structural studies suggest that
faults of this orientation are mainly post-mineralization in timing, although further fieldwork
and compilation will be necessary to fully assess such relationships.
21
Figure 13: Vein systems exposed in
the haul road to the Cassiar
asbestos mine northwest of the
Hawthorne property. View is to the
northeast. Northeast trending shear
veins which dip steeply to the left are
joined in their hangingwall by sets of
quartz extension veins which locally
have sigmoidal shapes that indicate a
northwest-side down/sinistral shear
sense.
The vein orientations and
kinematics are the same as those in the
main Cassiar gold camp, suggesting
the veining event that formed in the
camp affects a much broader area than
has previously been targeted for gold
exploration. The veins here are hosted
by a more competent cherty sediment
unit which dips to the northeast in a
sequence of carbonaceous phyllite.
• Previous literature documenting vein systems in the Cassiar area has frequently focused on
identification of a potential fluid source and primary genetic source of gold which was
subsequently deposited in the veins. As mentioned above, it has been cited by some workers
that the absence of a steeply dipping major crustal scale shear zone in the area negates the
possibility that the Cassiar vein systems are of the orogenic type, and argues instead for the
presence of a cryptic, unexposed granitic intrusion at depth as a fluid source (Nelson, 1990).
However, as is discussed above, the vein systems are typical of the style, timing and geometry
with respect to syn-metamorphic fabrics as typical orogenic gold systems. While a contribution
to the hydrothermal fluid by a buried intrusion is possible, as is invoked in the magmaticmetamorphic fluid mixing model for orogenic gold deposits that is currently popular in gold
exploration in Australia, the timing and style of mineralization argue for a significant, if not
exclusive, contribution of metamorphic fluid to the hydrothermal system. Even if a buried,
distal intrusion was present and contributed to the hydrothermal fluid, it is sufficiently distal
that no major zonation gradients are apparent other than a broad zoning to more Ag-rich vein
system in peripheral parts of the camp, so within the camp itself understanding fluid pathways
and structural trap sites forms a more practical approach to exploration than assessing an
ultimate fluid source.
22
Conclusions and Recommendations
• There is high potential in the Cassiar area for the discovery of new vein systems, and with the
consolidation of the district now by Hawthorne, there is also great opportunity to for the first
time systematically explore the district. The similarities in style to orogenic districts globally,
such as those in the Abitibi Greenstone Belt or the Mother Lode Belt of California, allow the
potential for development of vein systems and disseminated mineralization in multiple settings
and styles, most commonly linked to areas of high rheological contrast and spatially associated
with shear zones along older thrusts or lithologic contacts.
• Two levels of exploration and evaluation are apparent to further advance discovery and
maintain resources – 1) identification of new resources in more advanced target areas, and in
near mine settings, and 2) identification of new target areas in previously poorly explored
settings where completely new oreshoots or sets of veins could be developed. In more
advanced target areas, high potential exists for new mineralization close to current areas of
known veining such as in the Bain decline area, where new veins may represent parts of
networks spatially associated with know veins, as extensions of known veins along controlling
structures, or as en echelon steps of veins. New veins may also occur where syn-mineralization
shear zones are traced along strike or down dip into areas where they are dilational, so the
recognition and tracking of such features directly through recognition in mapping and in drill
holes, and indirectly through the tracking of offsets of lithologic contacts caused by them, are
important targeting tools. In areas of low grade resources at Taurus, potential exists for
definition of higher grade shear veins and shear zones within the existing low grade resources
which could be mined selectively. New, more grassroots and early stage exploration target
areas could be defined through a combination of compilation work, surface mapping, and
geophysical targeting to identify prospective target areas, followed by reconnaissance drilling.
• Given the current resource levels and production objectives, to replenish resources during
upcoming mining and to maintain a flow of newer advancing targets leading ultimately to
resource definition and mining, a minimum of approximately 25,000 m of drilling annually will
likely be required. Approximately half of this could be directed to near term targets and
advanced areas, such as in the short term definition drilling of higher grade veins in the Taurus
low grade resource (5,000 to 7,000 m required), the disseminated pyritic mineralization at West
Taurus, and near mine testing of the Bain decline area for extensions of veins and new veins,
such as adjacent to the Bain and Cusac declines (also 5,000 to 7,000 m). Remaining drilling
(approximately 10,000 to 12,000 m) could be directed to less advanced property scale targets
stepping out from outcropping or known areas of veining (e.g. Wings Canyon, Sky vein) which
would need to be followed by definition drilling subsequently if mineralization is identified.
For resource replenishment, vein systems which are discovered by exploration will likely need
to be drilled at a spacing of no less than 25 m based on structural complexities and grade
distribution in historically mined veins in the district, and probably as tightly as 12.5 m, so it
will be important to maintain a healthy drilling budget while production occurs to establish
resource confidence for future mining.
• In addition to advancing the ongoing compilation work of the extensive historical data, several
geological tools are apparent which will aid in the exploration of the region. Given that
extension vein densities can increase adjacent to, or along strike from shear veins, tracking of
vein density in drill core and modeling of areas of higher vein density may aid in identifying
both prospective areas for shear vein development, and areas within broader zones of veining
where shear zones may be present. Tracking total % quartz also can have a similar utility.
23
Such features can be plotted along drill holes, underground drifts or trenches as histograms per
meter, or over custom intervals normalized per meter, and then modeled in Vulcan or other
software. The current drill core logging sheet in use by Hawthorne has columns for entry of
this data, but new data for historical drill holes may need to be obtained by focused core
relogging in areas of interest, or where historical core is unavailable, from drill logs if sufficient
details is available. Modeling of alteration types and intensity would also allow similar
targeting, as most intense areas of veining are likely to be outlined by alteration zones. High
priority target areas will likely require full core relogging programs in conjunction to
compilation and geological modeling to ensure all applicable data is gathered and to infill areas
where additional sampling is necessary. Given the importance of historical drill core in this
process, salvage of core in currently collapsing drill racks is strongly recommended before the
core, and associated information, is lost.
• Additional advanced targets may lie in the Main Mine and Cusac areas, where reopening of
workings will provide both a drill platform for evaluating near mine targets, and access for
sampling and mapping of many of the geological features mentioned above which could aid in
identifying nearby targets. New mapping could be added to previous maps, and include
additional information about alteration, veining and potential controlling or offsetting structures
to veins. Modeling of previous drilling data and review of historical drill core in these areas
will be necessary as part of this process.
• Over the upcoming winter, in addition to further compilation, a process of target ranking is
recommended, where priority of evaluation is assigned to those areas considered to have the
highest potential the initial focus of compilation. The ranking could be revisited as compilation
and evaluation proceeds, and then appropriate exploration or definition drilling meterage
assigned based on overall prospectivity and level of advancement of the project area.
References
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District, British Columbia, with implications for the origin of mother-lode gold deposits. Canadian
Journal of Earth Sciences, vol. 26, p. 2645-2660.
Ball, M., 1985: Structural geology associated with gold-bearing quartz veins in the McDame gold mining
camp, Liard Mining Division, Cassiar Disrict, British Columbia. Erickson Gold Mining Corp., internal
report, 22 pages.
Broughton, D., and Masson, M.:, 1996: Report on 1995 Exploration Program on the Taurus Project, B.C.,
NTS 104P/5, unpublished Report for Cyprus Canada Inc.
Ey, F, 1986: Structural analysis of the Cusac decline, Erickson Gold Mine, Cassiar, B.C.
internal report, 11 pages plus maps.
Minatco Ltd.,
Ey, F, 1987: Structural control of the Vollaug gold bearing quartz vein, Total Erickson Gold Mine, Cassiar,
B.C. Minatco Ltd., internal report, 9 pages plus diagrams.
Gunning, M., 1988: Cornucopia (Taurus Mine), Gold distribution in the Taurus veins. British Columbia
Department of Energy Mines and Petroleum Resources, Exploration in British Columbia 1987, pp. B95B105.
24
Hooper, D., 1984: A study of the gold-quartz veins at Erickson gold camp, Cassiar, north-central British
Columbia. The University of British Columbia, unpublished B.Sc. thesis, 110 pages.
Nelson, J., 1990: Evidence for a cryptic intrusion beneath the Erickson-Taurus gold-quartz vein system
near Cassiar, B.C.. B.C. Geological Survey Branch, Geological Fieldwork, Paper 1990-1, pp. 229-233.
Nelson, J., and Bradford, J.A., 1993: Geology of the Midway-Cassiar area, northern British Columbia.
B.C. Geological Survey Branch, Bulletin 83, 94 pages.
Panteleyev, A., Broughton, and D., Lefebure, D., 1997: The Taurus project: A bulk tonnage gold prospect
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