clinopyroxene composition, an indicator of magmatic affinity in mafic

CLINOPYROXENE COMPOSITION, AN INDICATOR OF MAGMATIC AFFINITY IN
MAFIC AND INTERMEDIATE METAVOLCANIC ROCKS FROM THE IBERIAN
PYRITE BELT
por
J. MUNHA.*
RESUMO
A composi9aO quimica das reliquias de cIinopiroxena ignea em metavulcanitos maticos e intermedios permite caracterizar
os diferentes grupos de rochas basalticas e andeslticas que ocorrem na Faixa Piritosa Iberica. As cIinopiroxenas dos doleritos tipo-A e das
lavas maticas inferiores (LML) contem em media mais Cr e menos Ca, Na e Ti que as cIinopiroxenas dos doleritos tipo-B e das lavas maficas superiores (UML); nas rochas andesiticas as clinopiroxenas apresentam varia90es quadrilaterais semelhantes aquelas que sao observadas para os doleritos-A e LML sendo caracterizadas por teores mais baixos de Cr, AI e Ti.
Os tipos de substitui9ilo cati6nica dominantes nas piroxenas da Faixa Piritosa sao: 1) Mti 2 Si = TiVI + 2 Ahv e 2) M~
+Si=(Fe 3 + + Cr+AI)VI+AJrv. Os dois tipos sao igualmente relevantes para as cIinopiroxenas dos doleritos-A e LML enquanto que 0
tipo 1) ecIaramente predominante nas clinopiroxenas dos doleritos-B e UML. 0 valor da razao AJ/Ti (nas cIinopiroxenas menos evoluidas)
decresce desde 22-5 nas cIinopiroxenas das rochas andesiticas, passando por valores entre 10 e 4 nas cIinopiroxenas dos doleritos-A e LML,
ate ~3 nas cIinopiroxenas dos doleritos-B e UML, 0 que indica cristaIiza9ilo a partir de magmas com valores de aSi02 progressivamente
decrescentes.
Os resultados sao compativeis com as informa90es obtidas a partir da analise de elementos im6veis na rocha total e indicam,
1) que os basaItos e andesitos nao sao relacionaveis por processos de cristaliza9ilo fraccionada, 2) que as rochas basaIticas variam desde
toleiticas/transicionais (na base do YS) a alcalinas (no topo do YS) e, 3) que as rochas andesiticas tern afinidades com as series calco-alcalinas
+
ABSTRACT
Relict clinopyroxene analyses, from the Iberian Pyrite Belt mafic and intermediate metavolcanics, have been used to identify
the various basaltic and andesitic rock groups from pyroxene chemistry. A-dolerites/lower mafic lavas (LML) and B-dolerites/upper mafic
lavas (UML) pyroxene groups differ primariy in Ca, Na, Ti and Cr contents; A-dolerite/LML cIinopyroxenes are higher in Cr and lower
in Na, Ti and Ca. Andesitic rock cIinopyroxenes show quadrilateral component variations which are similar to those observed for A-dolerites/ LML being characterized by lower Cr, AJ and Ti contents.
Dominant cationic substutions in the Iberian Pyrite Belt pyroxenes are 1) "M2vt + 2Si=Tivi+2Aliv and 2) M2vt + Si=
=(Fe3 + +Cr+AJ)vi +AJiv; they are of roughly equal importance in pyroxenes from A-dolerites/LML, but in pyroxenes from B-dolerites/
/UML type 1) is more important. AJ/Ti (atomic) ratios increase from ~3 in pyroxenes from B-dolerite/UML, through 4-10 in pyroxenes
from A-dolerites/LML, up to 5-22 in pyroxenes from andesitic rocks, indicating crystallization from magmas with progressively increased
asi02 levels.
The pyroxene data supports previous inferences from whole rock geochemistry and indicates that, (1) basalts and andesites
are not linked by fractional crystallization, that (2) basalts range from tholeiitic/transitional at the base of the Volcanic-Sedimentary Complex to alkaline near the contact with the overlying Culm Group and that (3) the andesitic rocks have magmatic affinities with calc-alkaline series.
1 - Introduction and geological setting
Upper Paleozoic volcanic rocks and volcanogenic
sediments are exposed in a zone about 250 km long
by up to 35 km wide that extends from near Sevilla
in southwest Spain to the Atlantic coast in south
Portugal. All along this zone extremely large pyritic
orebodies are found associated with volcanic rocks
characterizing the Iberian Pyrite Belt. The latter
constitutes the intermediate sub-zone of the South
Portuguese Zone (LOTZE, 1945; CARVALHO & al.,
1971), an external lower Carboniferous eugeosyncline flanking the central Hercynian block of Iberia.
The Iberian Pyrite Belt contains three major
lithostratigraphic units (for regional geological descriptions see: SCHERMERHORN & STATON, 1969; CARVALHO & al., 1971; SCHERMERHORN, 1971; OLIVEIRA
& al., 1979; OLIVEIRA, 1983), from base to top, the
* Departamento de Geologia, Faculdade de Ciencias de
Lisboa e Centro de Geologia da Universidade de Lisboa (I.N.I.C.).
239
Phyllite-Quartzite Formation (PQ), the VolcanicSedimentary Complex (VS; mostly Tournaisian to
lower Visean), and the Mertola Formation (Culm
facies). The Volcanic-Sedimentary Complex comprises felsic to mafic volcanics, sediments and the stratiform sulphidic and manganese deposits (BARRIGA
& CARVALHO, 1983). The Mertola Formation is a
flysch sequence of slates and greywackes. The exposed strata are of upper Devonian and lower Carboniferous age. All these rocks were deformed and
regionally metamorphosed during the Hercynian
orogeny. The tectonic framework is characterized by
an imbricated structure facing southwest due to
high-angle reverse faults post-dating the main cleavage, of pre- Westphalian-D age (RIBEIRO & SILVA,
1983).
Recent work (BARD, 1971; CARVALHO, 1972;
BARD & al., 1973, 1980; VEGAS & MUNoz, 1976;
RIBEIRO & al., in press) on the Iberian Variscan Orogen has called upon plate tectonic~ to expla~n str~­
tigraphic, structural and petrologIcal relatIOns III
the South Portuguese Zone. Nevertheless, some problems are still open, particularly in what concerns
the magmatic regime in the Iberian Pyrite Belt (see
for example SCHERMERHORN, 1975; ROUTHIER & al.,
1977' MUNHA, 1979, 1983b; FLOYD, 1982). Some of
these' problems arise because virtually all the Pyrite
Belt volcanic rocks have experienced some degree of
post-emplacement alteration that obscured original
mineralogical and geochemical characteristics and
thus prevent a rigorouf> reconstruction of their magmatic affinity.
Detailed investigation of the crystal chemistry
of clinopyroxenes in conjunction with experimental
studies reveal that clinopyroxenes may be important recorders of bulk chemistry, f0 2 , mineral paragenesis and cooling rate of their host rocks (KUSHIRO,
1960, 1972; LE BAS, 1962; COOMBS, 1963; BENCE &
PAPIKE, 1972; GROVE & BENCE, 1977; COISH &
TAYLOR, 1979). It has also been established that this
work has an useful application in studying spilitised lavas (VALANCE, 1969; 1974a, b; GARCIA, 1975;
SCHWEITZER & a!., 1979; LETERRlER & al., 1982).
In the Iberian Pyrite Belt clinopyroxene occurs frequently as a fresh igneous relict mineral in mafic and
intermediate metavolcanic rocks. By probing these
pyroxenes, it may be possible to see through the
effects of alteration and characterize the magma type
as well as the conditions of crystallization of the host
volcanic rocks; the present study was undertaken
in an attempt to obtain such information.
2 - Petrogmphic feactures of the metavolcanic
vocks
Volcanicity, mainly submarine, was active in the
Iberian Pyrite Belt throughout VS times producing
contemporaneous, though largely independent
(SCHERMERHORN, 1970, 1975; SOLER, 1973) felsic
(actually quartz..keratophyres) and mafic (now spilites
and albite-diabases) volcanics, with occasionally some
intermediate rocks. Felsicrocks are predominant and
comprise about 60-70 % of the total outcroping volcanic areas.
The Pyrite Belt volcanics generally exhibit clear
igneous textures. However, with the exception of
clinopyroxenes in mafic and intermediate rocks, the
primary mineralogy is rarely preserved. The volcanic
rocks have metamorphic assemblages characteristic
240
of the prehnite-pumpellyite/lower greenschist facies
and available geochemical data indicates that they
have experienced significant redistribution of several
major and trace elements during the alteration processes (MUNHA, 1979, 1983 a; MUNHA & KERRICH,
1980); as pointed out by several authors (c. f. SMITH,
1968; VALLANCE, 1974a, b), this has major implications for any discussion of their magmatic affinity.
Despite the problems presented by alteration, whole
rock chemical analyses are given in table I and some
aspects of the «immobile element» data will be used
to support the arguments in the ensuing discussion.
2.1-Mafic rocks
Mafic volcanics comprise essentially rocks of
basaltic composition and correspond to the «spilites» and «albite-diabases» of previous authors
(SCHERMERHORN, 1970, 1975; SOLLER, 1973). Samples selected for this study include both extrusive
and intrusive rocks which occur at various levels of
the VS stratigraphic sequence.
The lower mafic lavas (LML) are representative
of mafic extrusive magmatic activity at the onset of
VS times and were collected mainly from an area
between ENE Calaiias and Rio Tinto in southwest
Spain (see also FEBREL, 1967; RAMBAUD, 1969;
GARCIA PALOMERO & al., 1975). The majority of
these rocks are fine-grained to aphanitic massive
flows and exhibit predominantly inter granular to
subophitic or, more rarely, slightly porphyritic textures; phenocrysts are of (albitised) plagioclase and,
not so often, of clinopyroxene (typically a pale coloured variety) which also occurs as anhedral grains
interstitial to plagioclase micro lites of the groundmass. Other common relict igneous phases are
Fe-Ti oxides which occur as late-stage micro-grains
or small lamelar (ilmenite) crystals largely replaced
by sphene.
The upper mafic lavas (UML) occur near the
top of the VS sequence and were collected from the
Castro Verde-Ourique region of south Portugal (see
also SCHERMERHORN, 1970). They are very finegrained to aphanitic and highly vesicular. Due to
their high porosity the UML are very susceptible
to the effects of secondary alteration and an almost
complete mineralogical reconstitution to chloritealbite-carbonate-celadonite/with mica-hematite-epidote-sphene/rutile frequently occurs. In the few
samples in which original igneous minerals still survived the groundmass texture may be described as
pilotaxitic, with laths of (albitised) plagioclase and
grains of pyroxene set in an altered finely crystalline
mesostasis. Invariably, the pyroxene is a purple-coloured variety (Ti-augite), sometimes, partially
replaced by kaersutite and biotite (see table II); a
few pseudomorphs after olivine were also observed.
Doleritic sills consist largely of medium-grained
(albitised) plagioclase and clinopyroxene (or their
replacement products). Relicts of calcic-plagioclase
occur sporadically, and some samples contain additional small amounts of igneous ilmenite, Ti-magnetite, amphiboles, biotite, apatite, K-feldspar and
quartz (see table II). The texture is sometimes ophitic,
but most commonly subophitic to intergranular.
G. K. STRAUSS & J. MADEL (1974) reported on
the occurrence of ultramafic cumulates (picritic dolerites) within some dolerite sills. Petrographic observation (MUNHA, 1982) suggests that these cumulate
Table I: Average major and trace element concentrations in mafic and intermediate metavolcanic rocks
from the Iberian Pyrite Belt (after MUNHA, 1983b)
Si02 (a) wt. %
Ti0 2
1\120S
Fe2 0 S (b)
MgO
MnO
CaO
Na20
K20
P20 5
LML
N
53.15
1.95
15.56
11.28
5.71
10
10
10
10
10
10
0.24
8.42
3.33
0.14
0.22
10
10
10
10
I
UML
N
A
N
B
N
I-N
N
I-S
47.72
2.05
17.16
11.80
6.65
0.23
8.48
3.10
1.70
0.50
7
7
7
49.72
1.81
16.55
11.35
8.01
0.20
8.99
2.81
0.41
0.16
35
35
35
35
35
31
35
35
35
35
47.65
2.74
16.50
12.74
7.25
0.24
8.00
3.31
0.99
0.58
7
7
7
7
7
7
7
7
7
7
61.45
0.94
16.64
7.08
3.67
0.10
4.95
3.48
1.54
0.15
22
2!
22
22
22
22
22
22
22
22
60.47
0.4
18.55
5.70
4.18
0.07
3.86
5.42
0.77
0.14
192
133
262
45
60
53
36
423
515
26
27
161
55
37.3
68.0
33.8
6.55
7
7
6
2
2
2
6
7
6
5
7
7
7
3
3
3
3
3
3
3
79
8
174
49
77
22
22
22
56
15
15
15
37
213
223
22
22
21
24
106
22
58
52
14
432
113
29
141
22
7
'j
7
7
7
7
7
N
15
15
15
15
15
14
15
15
15
15
Trace Elements
ppm
Cr
Ni
V
Cu
Zn
Li
Rb
Sr
Ba
Sc
Y
Zr
Nb
La
Ce
Nd
Sm
Eu
Gd
Yb
138
41
288
30
52
31
6
201
73
36
39
147
5
15.1
31,.5
21.7
5.61
1.77
6.25
3.31
9
9
9
3
3
3
10
10
10
9
10
10
10
4
4
4
4
4
4
4
1.92
5.68
1.84
134
237
35
78
263
26
16
76
16
85
5
57
35
13
35
217
35
159
33
36
35
33
35
119
34
6
11
15.0
11
31.1
20.0
11
5.13
11
1.50
11
5.46
10
2.75
11
126
76
245
25
636
487
22
29
193
57
36.8
68.9
36.6
7.40
2.14
6.65
1.90
7
7
7
7
7
7
7
7
7
7
7
7
7
7
~I
9
20.5
40.5
21.6
4.85
1.27
5.03
3.53
9
9
22
22
3
3
3
3
3
3
3
16
107
7
14.4
31.4
16.5
3.43
0.82
2.87
1.16
11
11
6
15
15
15
15
15
15
2
2
2
2
2
2
2
(a) AI[ major elements calculated on a volatile free basis; (b) All Fe calculated as Fe3+
LML -lower mafic lavas; UML - upper mafic lavas; A - type A dolerites; B - type B dolerites;
I - andesites (-N: northern outcrops, -S: southern outcrops; see MUNHA~ 1983); N _nO of samples
rocks (now intensely serpentinesed) were originally
composed of olivine (Fo so)' plagioclase and minor
(1-2 % modal) spinel (Cr-pleonaste to Al-chromite),
with intercumulate clinopyroxene and late-stage
kaersutite-richterite, phlogopite, Cr-titanomagnetite
and ilmenite.
Detailed study of the relict igneous phases of a
large number of samples has permitted recognition
among the sills of two doleritic rock types:
a)
b)
type A - characterized by ilmenite-plagioclase-(pale coloured) augite. Sporadic occurence of quartz+K-feldspar late-stage granophyric intergrowths suggests tholeiitic affini..
ties for this rock group;
type B - characterized
by
Ti-magnetite
(rare)-ilmenite-apatite -plagioclaseTi augite-kaersutite-biotite. The
relict mineralogy is identical to that
of the UML (like the UML, type B
dolerites also tend to occur at
high levels within the VS sequence)
and suggests affinities with the alkali basaltic rocks.
2.2 -
Intermediate rocks
Intermediate rocks occur throughout the Iberian
Pyrite Belt and constitute extrusive masses and
variously shaped (mainly sills) intrusive bodies emplaced at different levels of the VS stratigraphie sequence. The studied samples were collected from
Pomadi.o [BOOGAARD'S (1967) keratophyres] and
from various places along D. CARVALHO'S (1976)
volcanic lineament D, which runs parallel to the
regional strike going through S. Domingos in south
Portugal.
The intermediate volcanic rocks have a distinct
porphyritic texture. Phenocrysts of (albitised) plagioclase (up to 25 % modal; sometimes exhibiting
a zoned alteration pattern) and of clinopyroxene
(up to 10 % modal), often grown together into clusters, occur in a fine fluidal groundmass. Hornblende
(see table II) partially replaces some pyroxene phenocryst. Minor biotite (largelly replaced by chlorite) as well as iron oxides and traces of apatite were
also observed. In the great majority of the studied
samples pyroxene grains account for less than 20 %
of the mode and the inferred original colour index is
clarley lower than that observed for the mafic vol241
Table II: Representative electron-pro be analyses of relict igneous minerals in mafic and intermediate
metavolcanic rocks
AMPHIBOLES
Sample
495-2
538-30
dolerite-B
Kaersutite
Si02 wt.%
Ti02
AI2 0 S
FeO
MgO
MnO
CaO
Na2 0
K 20
Total
Si
AIiv
Alvi
Ti
Fe s+
Fe 2 +
Mg
Mn
39.29
4.63
11.77
15.16
9.73
0.23
11.69
2.65
1.28
96.43
6.039
1.961
0.171
0535
1.945
2.229
0.030
BIOTITES
559-20
495-8
andesite
Hornblende
39.20
5.98
13.77
10.23
12.83
0.12
12.43
2.58
101
98.15
5.780
2.220
0.173
0.663
1.261
2.820
0.D15
34.83
5.63
12.69
27.22
5.41
0.41
0.00
0.16
9.09
95.44
7.121
0.879
0.022
0.119
0.611
2.130
0.044
538-30
551-7
dolerite-B
47.01
1.04
5.05
21.66
9.19
0.34
10.25
1.76
0.86
97.15
2.075
506-8
PLAGIOCLASE
36.26
8.98
13.82
1735
35.32
6.89
13.63
15.83
10.49
12.79
0.16
0.16
0.28
8.39
95.90
0.50
0.00
0.79
9.11
Si
Ti
AI
5.565
0.676
5.444
2.390
Fe
Mg
Mn
Ca
3.637
1.288
0.055
0.000
0.050
1.853
2.445
2.178
Na
K
dolerite-A
1.014
2.347
0.020
0.026
0.082
1.607
52.98
29.62
12.49
4.32
0.06
99.47
94.85
5.382
0.789
2.446
2.017
2.905
0.065
0.000
0.233
1.771
Si
AI
Ca
Na
K
K
0
1.925
0.790
0.251
23
1.964
0.738
0.190
23
1.663
0517
0.166
22
22
22
1.523
0.014
32
An%
61.29
38.35
0.35
Or
23
canics; these features, coupled with relatively high
Si0 2 contents (typically within the range 57-64 %;
see table I), indicate that the intermediate metavolcanic rocks should correspond to meta-andesites.
3 - Mineralogy of the relict clinopyroxenes
Mineral analyses were made at the Department of
Geology, University of Western Ontario, utilizing
a MAC 400 electron microprobe fitted with the
Krisel automation system; working conditions and
precision of the analytical method are discussed in
M. E. FLEET & R. L. BARNETT (1978).
In the following section some physical properties
and microprobe analyses of relict igneous clinopyroxenes will be examined in order to determine the
magmatic affinities of the Iberian Pyrite Belt metavolcanic rocks. Representative clinopyroxene bulk
analyses and structural formulae (calculated on the
basis of 4 cations) are provided in table III. Analyses
of other relict igneous phases are shown in table II.
3.1 - Occurence and optical properties
Textural relations suggest that in the Iberian
Pyrite Belt basaltic and andesitic magmas, clinopyroxene started to crystallize after olivine and after
or simultaneously with plagioclase, but always
before Fe-Ti oxides.
242
0
2.434
0
Ab
Ca
Na
9.636
6.350
Larger clinopyroxene grain cores in type A dolerites as well as phenocrysts in the LML are usually
pale coloured (pale green to very-pale pinkish-brown) but may show outward zoning to a brownish
rim which is similar to some late-stage, micro-granular, groundmass augite. These coloured rims and
grains also show the lowest 2Vy values (total range,
38-56°) thus, suggesting significant decreasing in
Ca/(Fe+Mg) towards late-stage iron enriched augite
varieties.
Clinopyroxenes in type B dolerites and UML
often show strong outward zoning from pale-pinkish
low-l'i augite to deep brownish-purple titan augite
and display both concentric and, less commonly, sector zoning. Where the sector zoning is observed,
the darken purple more Ti-rich composition is confined to the prism sector (100), as has been noted for
other occurrences (cf. HOLLISTER & GANCARZ,
1971). The observed 2Vy and c-yrange of values for
Ti-augites are 50-60° and 35-48°, respectively. While
Ti has been thought to have the effect of lowering
2Vy (DEER & al., 1978), the lowest 2Vy observed in
deep-coloured Ti-augite was about 50°; the presence of other substitutions, especially acmite (pale
greenish yellow to dark green, pleochroic, sodian
ferrosalite occurs as late-stage, interstitial micro-grains), may counteract the effect of Ti.
In the andesitic rocks clinopyroxene relicts occur
as colourless to extremely pale green phenocrysts
and micro-phenocrysts. 2Vy and c-y values range
from 440 to 56° and 33° to 440 respectively, much
within the range observed for type A dolerites and
LML.
3.2 - Chemioal composition
a)
Ca - Mg - Fe Relations
Variations in the atomic proportions Ca: Mg: Fe
for clinopyroxenes from mafic metavolcanics and
meta-andesitic rocks are illustrated in figs. la and
1b, respectively.
It seems clear from the data on fig. la that the
clinopyroxenes from different mafic metavolcanic
rock groups are readily distinguished on the basis
of both Ca contents and crystallization trends. All
but a few analyses of pyroxenes from LML and
A-dolerites have Ca contents bellow 45 % at. (atomic) and, in spite of considerable scatter, their predominant average crystallization trend is similar to
that reported for clinopyroxenes from tholeiitic
basalts (CARMICHAEL, 1967; EVANS & MOORE, 1968;
see also fig. lc). In contrast all the data points representative of clinopyroxenes from UML and B-dolerites plot above 45 % Ca (at.) and display a salite-ferrosalite trend showing late stage enrichment in
50
o
co
40
liD
70
30
A.
aegirine molecule, as usually observed for most alkali
basalt rock suites (WILKINSON, 1956; see also fig. lc).
Although the precise nature of the clinopyroxene
chemical trend may also depend on the physical
conditions during magmatic crystallization (see BARBIERI & al., 1971), the fact remains, however, that the
salite-ferrosalite-sodian ferrosalite trend observed
for the UML/B-dolerites, which is typical of alkaline
basic magmas, is markedly different from the augite-feroaugite trend typical of the non- alkaline varieties; thus, the pyroxene data do not contradict the
petrographic observations in what concerns the
magmatic affinity of the mafic metavolcanic rocks.
The crystallization conditions which give rise to
these types of pyroxene trends in mafic rocks from
the Iberian Pyrite Belt will be discussed in a later
section.
Ca:Mg:Fe relations in Ca-rich pyroxenes from
andesitic rocks (calc-alkaline) have been studied by
A. L. SMITH & A. E. CARMICHAEL (1968), G. LOWDER
(1970, 1973) R. V. FODOR (1971) and A. EWAR.T
(1976), who suggested that clinopyroxene compOSItions are concentrated within the augite field, and
show no tendency to develop marked iron enrichment at anv stage during crystallization in modern
orogenic lavas. In the Iberian Pyrite Belt andesitic
rocks the first clinopyroxene to crystallize (phenocryst cores) has an average composition FS9En47W044
but with continued fractionation, there is an increase
in Fe/Mg ratios coupled with a slight decrease in
Ca contents (fig. 1b); the iron-richest clinopyroxen.e
is about Fs 30 En 29 W0 41 • There is, however, a conSIderable overlap between pyroxenes from andesitic rocks and those from LML/A-dolerites, and
clinopyroxenes from these two lithotypes are not
readily distinguished in terms of «quadrilateral»
components.
b)
80
70
50
SO
70
Ig
___
-7
---6
-.
50
'~440
c.
30
Fe
Fig. 1 - Ca-Mg-Fe variations in clinopyroxenes from the Iberian
Pyrite Belt.
A) Lower mafic lavas (squares); type A dolerites (closed circles); type B dolerites + upper mafic lavas
(open circles).
B) Intermediate rocks (andesites) (stars).
C) Comparative data from (1) Skaergaard (BROWN, 1957;
BROWN & VINCENT, 1963), (2) Kap Edward Holm
(CARMICHAEL & aZ., 1974), (3) Shiant Island (GIBB,
1973), (4) Shonkin Sag (NASH & WILKINSON, 1970),
(5) Japanese alkaline rocks (AOKI, 1964), (6) Canary
Islands (SCOTl', 1975), and (7) Monte Somma
(Vesuvius) (RAHMAN, 1975).
Si, AI, Ti and Na
I. KUSHIRO (1960) and LE BAS (1962) suggested
that the amounts of Al and Ti entering clinopyroxene
depend on the degree of alkalinity of the parent
magma and hence that Al and Ti contents of clinopyroxene could be used to indicate the nature of the
original magma. However, the Al and Ti contents
of the clinopyroxene are essentially a reflection of
the silica activity (VERHOOGEN, 1962; BROWN, 1967;
GRUPTA & al., 1973; CAMPBELL & NOLAN, 1974) and
the physical conditions under which the pyroxene
crystallized (BARBIERI & al., 1971; THOMPSON, 1974;
WOOD, 1976; COISH& TAYLOR, 1979) and,consequently, as F. BARBIERI & al. and R. A. COISH & L. TAYLOR pointed out, no simple relationship is to be
expected between pyroxene composition and parental magma type. This conclusion is substantiated by
clinopyroxene data on Eg. 2b which shows that compositional zoning in clinopyroxenes from. UML/B-dolerites may extend from the non-alkahne to the
peralkaline field of LE BAS (1982). Nevertheless,
since under the same general conditions aSi02 should
increase from strongly undersaturated to oversaturated magmas, it should be possible to obtain (0!1
a statistical basis) from the pyroxene data, some quahtative information regarding the magmatic affinity
of their host rocks. As shown in figs. 2a, b, and c,
the majority of the analysed clinopyroxenes. ~rom
UML/B-dolerites (about 73 %) are equally dIVIded
between the alkaline and perakaline fields; 63 % of
243
Si02 wt'/,
A
52
50
48
4&
the data points representative of pyroxenes from
LML/A-dolerites plot in the non-alkaline field (with
the remainder falling in the alkaline field) while
all but one of the analysed pyroxenes from andesitic
rocks fall in the non-alkaline field of LE BAS (1962).
Decreasing average Al 20 3 wt. % contents is precisely
what should be expected if pyroxenes from UML/B-dolerites, LML/ A-dolerites and andesitic rocks
would have crystallized from magmas with progressively increased aSi02 levels, as it should be the
case on going from alkali through tholeiitic basaltic series and andesites (NICHOLS & al., 1971; CARMICHAEL & al .• 1974).
Plotting AI, Ti and Na against Si, and Ti against
Al in terms of atoms per 4 cations (calculated taking
all Fe as Fe!l+) as in figs. 3a and b reveals the manner
44~-----.-----r-----.-----.------
o
2
4
&
Si02wl'lo
B
o
.20
50
.10
48
46
O~------,-------~------~------~----~
-+-
Si
44
Na
.025
42
1.75
40~----~---'-----.-----r----~----
o
2
4
&
8
10
1.85
1.80
2.00
1.95
1.90
Si
AI203 wl'/,
C
Ti
.075
•
.050
52
•
.025
•
•
.0
eo
B~
•
"t.
~
D~.
--------
°
O.'I;J,:'0 q, 0",
C!":::::'----1,1
•• ·"~OO
¥-~\¥-¥-~TD
• •• • . '
.~l.J-'
.. . . . . . .
•
••0 •• 0
~
If..
~
0
.00
50
.10
.15
.2D
.25
Alt
H'ig. 3a - Alt. Na-Si and Ti_Alt relationships for clinopyroxenes
in lower mafic lavas, type A dolerites and andesitic
rocks.
48
46~----~----~~----~-----
o
2
4
Fig. 2 - Si02 - Al20 a relationships for clinopyroxenes in mafic
and intermediate metavolcanic rocks from the Iberian
Pyrite Belt. Compositional fields after LE BAS (1962).
A) Lower mafic lavas and type A dolerites.
B) Upper mafic lavas and type B dolerites.
C) Intermediate (andesitic) rocks.
244
.05
in which these elements are substituted in pyroxene;
the data poinsts are scattered but overall trends are
evident. All but a few of the Al values lie above the
1:1 line in figs. 3a and b indicating that any Si deficiency is made up by Aliv ; as should be expected the
maximum amount of Aliv for Si substitution is
variable for each pyroxene group (up to 20 % in
clinopyroxenes from UML/B-dolerites, less than
10 % in c1inopyroxenes from LML/A-dolerites, and
usually less than 5 %in clinopyroxenes from andesitic
rocks). Together with the sympathetic relationships
o
o
00
.15
.20
AI IV
3
Fig. 4 - Variation of Fe +(calculated) against Aliv for clinopyroxenes in lower mafic lavas and type A dolerites.
.10
Ti
.10
.05
ther difficulties generated during extensive magmatic differentiation, characteristic AIfTi values for
each suite are as follows:
o
CLINOPYROXENE
.15
AndesiticRocks
LML/A-dolerites
UML/B-dolerites
.10
AIfTi
22-5
10-4
3
.05
Na
0
.15
0
.10
.05
B
0
0
00
0
00
0c2 {fo
fI
00 {g!
0
1.8
1.7
1.&
3~
CID
«D
°O«D
cP
@9oogo
2.0
1.9
Si
Fig. 3b - Alt, Ti and Na-Si relationships for clinopyroxenes in
upper mafic lavas and type B dolerites.
of Ti (figs: 3a and b) and Fe 3+ (fig. 4), this suggests
that the dominant substitutions are:
M!t + 2Si
2+
.
=
Ti vi + 2A1iv
Mvi + Sl = (Fe
3+
+ Cr + AI)vi + Aliv
(1)
(2)
Comparison of the data on figs. 3a, band 4 indicate
that while both types of substituion are of reoughly
equal importance in pyroxenes from LML/A-dolerites, type (1) is clearly more important in pyroxenes
from UML/B-dolerites (see also SCHWEITZER & ai.,
1979). Considering the relative importance of these
two types of cation substituion it is instructive to
compare the AIfTi ratios exhibited by clinopyroxenes
from each of the studied rock groups. As shown in
figs. 3a and b, the analysed clinopyroxenes display
a considerable range of AI/Ti variation; if we restrict the comparison to the less evolved pyroxenes
(Fe/Fe+Mg less than 0.25), in order to avoid fur-
It was already emphasized that the presence of
considerable amounts of Al and Ti in clinopyroxene
has been ascribed variously to bulk composition,
temperature, pressure and cooling rate of the
magma from which the pyroxenes crystallize. While
the slightly higher AIfTi ratios observed in pyroxenes from LML relative to those from A-dolerites
(fig. 3a) could be used to support R. A. COISH &
L. A. TAYLOR's(l979) contention regarding the effects
of cooling rate, several other lines of evidence do
indicate that neither this parameter, nor pressure,
are of fundamental importance in explaining the
variable amounts of Al and Ti in the analysed clinopyroxenes (see STORMER, 1972;GRUPTA & ai.,
1973). If we accept this simplifying hypothesis then,
at a given temperature, AI/Ti ratios in clinopyroxene
should be buffered by its host magma composition according to following reaction:
CaTiAl2 06 + SiO z = CaAISiA10 6 + Ti02
cpx
melt
cpx
melt
aCaAISiA106)
) "
( ------'. cpx = CSi0 / aTi0 melt· K(3)
2
2
aCaTiAl 2 0 6
(3)
(4)
or
It is not p6ssible, with the thermochemical data
available at present, to define quantitatively the characteristic range of AI/Ti values for clinopyroxenes
crystallizing from each of the main magmatic series:
average Si02 /Ti0 2 ratios in basalts (IS - alkaline
olivine basalt; 20 - tholeiitic basalt; 42 - calc-alkaline basalt; data from HYNDMAN, 1972) suggest
that AIfTi ratios should increase pro"gressiveIy from
lower values in clinopyroxenes crystallizing from
alk~Ji basalt magmas to higher values in clinopyroxenes crystallizing from tholeiitic and calc-alkaline
245
basalt magmas, a conclusion that is apparently substantiated by the clinopyroxene data presented here
for the Iberian Pyrite Belt volcanic rocks.
Except for late-stage pyroxenes in type B dolerites
Na contents are low (figs. 3a and b), but the small
change of Na with increasing Ti indicates some
involvement of the NaTiAISi06 substituion suggested
by L. S. HOLLISTER & A. J. GANCARZ (1971). It
seems probable that most Na is present as acmite, a
possibility enhanced by the known presence of
Fe H in these pyroxenes (BARRIGA & MUNIIA,
unpublished data).
Several authors have recorded systematic variations in the Al and Ti contents of pyroxenes with
increasing fractionation (c. f. EVANS & MOORE, 1968;
SMITH & CARMICHAEL, 1969; SMITH & LINDSLEY,
1971; FODOR & al., 1975; TRACY & ROBINSON, 1977;
SCHWEITZER & al., 1979; BIZOUARD & al., 1980).
The observed trends are variable but clinopyroxenes
from alkali basalts are characterized by the widest
range of Al and Ti concentrations with high values
at low Fe/{Fe + Mg) and low values at high Fe/
/(Fe + Mg), (compare fig. 5); clinopyroxenes from
tholeiitic basalts tend to show similar trends but
much more limited and smoother variations. Data
for clinopyroxenes from calc-alkaline rock suites are
scarce, and in general they are vey low in Ti and low
in AI. When the Ti contents of the cIinopyroxenes
from the Iberian Pyrite Belt volcanic rocks are plotted against Fet/{Fe t + Mg) (fig. 5) some interestingfeatures are revealed: clinopyroxenes from different rock groups contrast markedly in terms of Ti
contents for the same Fe/(Fe+Mg) ratio. Bulk analyses (see table III) indicate that pyroxenes from andesitic rocks always have less than 1 wt. % Ti02 , those
from LML/A-dolerites typically range from 1-2
wt. % Ti0 2 , whereas those from UML/B-dolerites
Ti
A.
.15
o
ALKALINE
fuo
.10
NON - ALKALINE
.05
o
o
o
o
o ~-----r------r-----~------~-----'-----.5
.Ii
.7
.8
.9
1.0
Ca+ Na
Ti+Cr
B.
NON - OROGENIC
.05
D
.fJ 0
.n
o
•
n
o
o
o
c9
.15
8>
0~~--,,-----,------,------'-----1-­
o
.5
o
Ti
~00r9
oo~ '$>0
0
o
•15
.0 •.
••
.01
... a.~ •
~
o
0.:''' •••
.J1~~
•
00
tJ ",,,, '" .... ~r.'"
o~
o
o
o
CD 0 0 0000
'"
I~--~----~----~--~----~--~----~
.1
.2
.3
.4
.5
.1
.7
Fe/Fe+Mg
••
Fig. 5 - Ti variations with Fe/(Fe+ Mg) ratio in clinopyroxenes.
Symbols are the same as in fig. 1.
246
c.
CALC - ALKALINE
0
-.at 0 •
~ 8
•
0
1.0
.02
• ~ o . o.
,
.9
0
.11
(l)
.8
.7
Ca
~
o
.6
o
.05
.10
.15
.20
All
Fig. 6 - Characterisation of the magmatic parentage of the Iberian Pyrite Belt metavolcanic rocks using the distribution of the compositions of the clinopyroxene phenocrysts (except for UML and B-dolerite for which non-evolved clinopyroxene compositions have been plotted)
in LETERRIER & al.'s (1982) discrimination diagrams.
Symbols are the same as in fig. 1.
may reach up to about 7 wt. % Ti0 2. For each clinopyroxene group it is apparent that Ti increases with
Fe content until a given value of Fe/(Fe+Mg) whereupon there is a reversal with further increase in
Fe. It is evident from fig. 5 that these reversals occur
at different Fe/(Me+Mg) and Ti values for each clinocpx/melt
cpx /melt
.
pyroxene group. Smce D FeO/MgO and D Ti
do not seem to change drastically, at least for basic
and intermediate compositions (THOMPSON, 1974;
PEARCE & NORRY, 1979), the clinopyroxene data
clearly indicates that the various rock groups represent different magma types which are not related by
crystal fractionation.
Plotting clinopyroxene phenocryst compositions
in terms of Ca, CA + N a, and Alt against Ti (or
Ti+Cr) (see fig. 6), as in J. LETERRIER & at.'s (1982)
discrimination diagrams, confirms and expands the
information already obtained from previous plots.
UML/B-dolerite clinopyroxene compositions (fig. 6a)
are related to the alkali basalt series whereas the
LML clinopyroxene phenocryst analyses (figs. 6a
and b) plot in the areas of the diagrams characteristic
of clinopyroxenes in tholeiitic/transitional basalts
from spreading zones; in contrast, the clinopyroxene phenocrysts from andesitic rocks plot in the
orogenic field (fig. 6b) and show a calc-alkaline tendency in fig. 6c.
c)
.113
••
o
.il2
a
•
.0
o oeo
•
••
qs:
B·.
.01
[]ii
o •
••
o••
. 0
_0
•
•.
0
tJ •
. . [J tJ ••
•
•
O+-----~~~~~~~~~~~--~
.1
.2
.6
.5
.4
.3
Fe/Fe+Mg
·03
Cr
b
'02
·01
Mn and Cr
t+------.~Ull~~~~~~~~~-.
The pyroxenes of all three lithological groups
show a positive correlation between Mn content
and Fe/(Fe+Mg), (table III).
Cr H has the highest crystal field stabilization
energy in octhaedral sites of any transition metal
ion (BURNS, 1970) and, in consequence, it partitions
strongly into the early formed clinopyroxenes resulting in its rapid depletion in the melt with fractionation (fig. 7). As shown in fig. 7, Cr H is enriched in
clinopyroxenes from LML/A-dolerites relative to
those from UML/B-dolerites and andesitic rocks.
3.3 -
0
·2
·4
·6
t t
Fe/Fe+Mg
1
·8
.02
c
.01
Discussion
o~----~~----~~==~----~~--
The compositional vanatton of pyroxenes associated with fractional crystallization of basaltic
magmas is related to the two main series, tholeiitic
and alkali basalts. Thus, the tholeiitic series is characterized until a late stage of fractionation by a
two pyroxene assemblage and the Ca-rich pyroxenes
show an initial decrease in Ca content. In contrast
the single Ca-ricll pyroxene of the alkalic series is
richer in calcium and the fractionation trend is
approximately parallel to the diopside-hedenbergite join until a late stage of fractionation, whereupon Ca contents may decrease due to enrichment in
aegirine molecule; in addition to the initial pyroxenes of alkali magmas being more calcic than those
of tholeiitic liquids, it is also significant that those
of strongly undersaturated magmas are more calcic
than those of alkaline magmas (see fig. lc).
As previously discussed by F. GIBB (1973), the
general situation is analogous to that in the synthetic system Mg2Si04-CaMgSi206-Si02 (KUHSIRO, 1972)
and the more calcic nature of the initial clinopyroxenes crystallizing from alkalic magmas seems to be
related to the low silica activities of the liquids causing
.1
.2
.3
.4
.5
Fe/fe+Mg
Fig. 7 - Cr - Fe/{Fe+ Mg) relationships for clinopyroxenes in
mafic and intermediate metavolcanic rocks from the
Iberian Pyrite Belt.
A) Lower mafic lavas and type A dolerites.
B) Upper mafic lavas ant type B dolerites [some clinopyroxenes from ultramafic cumulates (MuNHA,
1982) are also plotted as stars within circles].
C) Andesitic rocks.
the precipitation of only a single pyroxene. In the case
of the Iberian Pyrite Belt basaltic rock pyroxenes,
those from UML/B-dolerites have calcium contents
which are typical of c1inopyroxenes from alkaline
magmas and some specimens may even plot above
the diopside-hedenbergite join due to the exclusive
substitution of «non-quadrilateral» components for
Fe2+ and Mg in (M 1). On the other hand, early
crystallizing pyroxenes from LML/ A-dolerites display Ca contents intermediate between those com.
monly observed in clinopyroxenes from tholeiites
247
and those reported for pyroxenes from mildlyalkaline basic rocks (see figs. la and c). Coupled with
the absence of Ca-poor pyroxene, these features
suggest that at least some LML/ A-dolerites may
have chemical affinities with transitional basalts
(COOMBS, 1963); i.e., relative to typical tholeiitic
magmas, the SiO., contents of these basaltic liquids
were low and/or -aSi02 did not increase at a rate
fast enough to stabilize Ca-poor pyroxene.
While the composition of the initial pyroxene
depends largely on the nature of the parental
magma, the subsequent trend is controlled by the
conditions under which fractional crystallization took
place; in the case of the Iberian Pyrite Belt basaltic
rocks, the augite-ferro augite and salite-ferrosalite
-sodian ferrosalite pyroxene trends displayed by the
LML/ A-dolerites and UML/B-dolerites, suggest that
these conditions must have been different for the two
rock groups. In UML/B-dolerites continued crystallization under low silica activity kept the clinopyroxene compositions within the salite field but, as
the H 20 content rose in the magma (a possibility
enhanced by the common occurrence of late amphibole and biotite), f0 2 fell at a much slower rate than
that necessary to maintain a constant Fe~+jFe3+
. III
. t h e 1·Iqm·d WIt
. h t h e resu It t h at amelt
Fe~+ rose
ratIO
Fel? +t h
·
· to t h at 0 f amelt
re IatIve
us, I
exp·ammg
t h e crystallization of pyroxenes with high aegirine contents
towards the later stages of fractionation. In contrast, the strong iron enrichment, decreasing Ca
contents and lack of significant aegirine molecule
enrichment in c1inopyroxenes from LML/A-dolerites suggest that crystallization took place under
relatively higher silica activity but lower f0 2.
Pyroxenes from the andesitic rocks have «quadrilateral» component chemical charateristics which
are, in many respects, similar to that described for
LMLj A-dolorites. Their lower Al contents and
higher AljTi ratios suggest, however, that they precipitated from Si02 richer liquids; this is consistent
with their host rock bulk chemistry and with M.
BOOGARD'S (1967) contention that some chloritic
pseudomorphs in kerathophyres could represent former Ca-poor pyroxene.
The data discussed above indicates that fresh
igneous pyroxenes, even in highly altered basalts/
jandesites, may provide important clues about the
original chemical character of their host rocks.
Pyroxenes from the the Iberian Pyrite belt LMLjA-dolerites and UML/B-dolerites differ primarly in
the abundances of the components, CaO, Ti0 2,
Cr20 3 and Na 20; a comparison with the clinopyroxene chemistry of fresh basalts indicates that these
rocks represent the crystallization products of transitional/tholeiite and alkali basalt magmas, respectively. Pyroxenes from intermediate rocks are characterized by low Cr, Al and Ti contents as it appears
to be typical in clinopyroxenes from the calc-alkaline series.
4-
Some concluding remarks on the magmatic
evolution of the Iberian Pyrite Belt
Hercynian volcanism in the Iberian Pyrite Belt
is essentially representative of a bimodal association
of tholeiitic to alkalic basalts and rhyolites, with
only subordinate andesitic lithotypes. Although clo248
sely associated the felsic and mafic volcanics OrIgInated and evolved separately (SCHERMERHORN, 1970,
1975; SOLER, 1973); no lithological transitions occur
and the volcanic centers are distinct. In contrast to
what have been previously suggested by M. LECOLLE (1977) and P. ROUTHIER & a!., (1977), the
clinopyroxene data obtained during this study
indicates that basalts and andesites are not linked by
fractional crystallization; furthermore, the estimated
volumetric relationships between basalticjandesitic
rocks and rhyolites in the Iberian Pyrite Belt, where
rhyolites are about 3 times more abundant on the
surface argue against the generation of rhyolites by
fractional crystallization of basaltic or andesitic
magmas. The source for the mafic magmas must
be sought in the upper mantIe but the high (87Srj
j86Sr)i values exhibited by the felsic volcanics (up
to 0.7135; PRIEM & at., 1978) suggest that they were
derived from magma chambers developed by melting in the crust (see also MUNHA, 1983b), possibly
by heat supplied by rising mafic magmas.
Relict clinopyroxene chemistry and whole rock
«immobile» minor and trace element data (see table I) show that the basaltic lavas occurring at the
base of the Pyrite Belt volcanic sequence have
tholeiitic affinities and some geochemical characteristics transitional to island arc basalts (particularly
LILE/HFSE values; see also PERFIT & at., 1980;
SAUNDERS & at., 1980; WOOD & at., 1981) similar
to some basalts erupted during the initial stages of
back arc spreading (SAUNDERS & TARNEY, 1979;
SAUNDERS & at., 1979; WEAVER & at., 1979). However, towards the top of the VS Complex basaltsj
jdolerites become alkaline and display a significant
enrichment in incompatible elements (see table I)
such that the upper mafic lavas are typical «within
plate basalts» (see also MUNHA, 1979, 1983b) characteristic of continental rift zones and some ocean
islands. The range of compositions displayed by
the Pyrite Belt basaltic rocks and their relict clinopyroxenes cannot be accounted for only in terms
of fractional crystallization processes (MUNHA,
1983b); specifically, the wide range of highly incompatible trace element ratios (see table I) suggests
that at least some of the observed heterogeneities
might have been directly inherited from their mantle source(s), (see also ERLANK & KABLE, 1976;
PEARCE & NORRY, 1979; WOOD & at., 1979). Similar
basalt-rhyolite associations are commonly found
within and/or near continental margins in areas characterized by rifting and/or back-arc spreading tectonics (c. f. NOBLE, 1972; MACDONALD, 1975;
RANKIN, 1976; SMITH & at., 1977); available geological data pertinent to the South Portuguese Zone
of the Iberian Variscan Orogen (RIBEIRO & al.,
in press) is also compatible with such a tectonic
setting for the Iberian Pyrite Belt. By analogy with
recent examples (c. f. CHRISTIANSEN & LIPMAN, 1972;
BEST & BRIMHALL, 1974; GILL, 1976; SMITH & al.
1977; SAUNDERS & TARNEY, 1979; CAMERON & al.,
1980) it is suggested that the particular volcanic rock
types which occur in the upper Paleozoic geosynclinal sequence of the Iberian Pyrite Belt, including
andesites, transitional arc tholeiites and «within
plate» alkali basalts, may reflect the transient geochemical nature of the mantIe under a former active
continental margin combined with complex melting
relationships attending the initial stages of an
attempt for ensialic back-arc spreading.
AKNOWLEDGEMENTS
This study was initiated several years ago in the Department of Geology at the University of Lisbon; I wish to thank
F. Barriga for his enthusiastic colaboration on the difficult task
of mineral separation. The final paper is based on a portion of a
Ph. D. thesis submitted by the author to the University of Western Ontario (London, Canada); valuable criticism and discussion
provided by Professors W. S. Fyfe and W. R. Church are gratefully acknowledge. Special thanks are also due to R. L. Barnett
for advice and technical assistance with the electron-microprobe
analyses.
REFERENCES
AOKI, K. (1964) - Clinopyroxenes from alkaline rocks of Japan.
Am. Mineral., Washington, vol. 49, pp. 1119-1223.
BARBIERI, F., BIZOUARD, H. & VARET, J. (1971) - Nature of the
clinopyroxene and iron enrichment in alkalic and transitional basaltic magmas. Contr. Min. Petrol., Berlin, v. 33,
pp. 93-107.
BARD, J. P. (1971) - Sur l'alternance des zones metamorphiques
et granitiques dans Ie segment hercynien Sud-Iberique; comparaison de la variabilite des caracteres geotectoniques de
de ces zones avec les orogenes «orthotectoniques». Bol.
Geol. Mill. Espana, Madrid, v. LXXXII-TIl-IV, pp. 324-345.
BARD, J. P., BURG, J. P., MATTE, P.& RIBEIRO, A. (1980) - La
chaine hercynienne d'Europe occidentale en termes de tectonique de plaques. Colloque C. 6,26. 0 Congr. Geol. Int., Paris.
BARD, J. P., CAPDEVILLA, R., MATTE, P. & RIBEIRO, A. (1973)Geotectonic model for the Iberian Variscan Orogen. Nature,
London, v. 241, pp. 50-52.
BARRIGA, F. & CARVALHO, D. (1983) - Carboniferous volcanogenic
sulphide mineralizations in South Portugal (Iberian Pyrite
Belt). Mem. Servo Geol. Port., Lisboa, n.O 29, pp. 99-113.
BENCE, A. E. & PAPIKE, J. J. (1972) - Pyroxenes as recorders of
lunar basalt petrogenesis. Chemical trends due to crystal-liquid interactions. Proc. Lunar Sci. Con! 3rd., pp. 431-469.
BEST, M. G. & BRIMHALL, W. H. (1974) -Late Cenozoic alkalic
basaltic magmas in the Western Colorado Plateaus and the
Basin and Range transition Zone, U.S.A. and their bearing
on mantle dynamics. Geol. Soc. Am. Bull., Boulder, vol. 85,
pp. 1677-1690.
BIZOUARD, H., BARBIERI, F. & VARET, J. (1980) - Mineralogy
and petrology of Erta Ale and Boina volcanic series, Afar
rift, Ethiopia. J. Petrology, Oxford, vol. 21 (2), pp. 401-436.
BOOG AARD, M. Van den (1967) - Geology of the Pomarao region
(Southern Portugal). Univ. Amesterdam, Rotterdam Delko,
113 pp.
BROWN, G. M. (1957) - Pyroxenes from the early and middle
stages of fractionation of the Skaergaard intrusion, east
Greenland. Min. Mag., London, vol. 31, pp. 511-543.
- - (1967) - Mineralogy of basaltic rocks. In Basalts, vol. 1,
pp. 103-162. H. H. HESS & A. POLDERVAART eds., Interscience.
BROWN, G. M. & VINCENT, E. A. (1963) - Pyroxenes from the
late stages of fractionation of the Skaergaard intrusion, east
Greenland. J. Petrology, Oxford, vol. 4, pp. 175-197.
BURNS, R. G. (1970) - Mineralogical applications of crystal field
theory. Cambridge Univ. Press, 224 pp.
CAMERON, K. L., CAMERON, M., BAGBY, W. C., MOLL, E. J. &
DRAKE, R. E. (1980) - Petrologic characteristics of mid-Tertiary volcanic suites, Chihuahua, Mexico. Geology,
Boulder, vol. 8 (2), pp. 87-91.
CAMPBELL, I. A. & NOLAN, J. (1974) - Factors affecting the stability of Ca-poor pyroxene and the origin of Ca-poor minimum in Ca-rich pyroxenes in tholeiitic intrusions. Contr.
Min. Petrol., Berlin, vol. 48, pp. 205-219.
CARMICHAEL, I. S. E. (1967) - The mineralogy of Thingmuli, a
Tertiary volcano in Eastern Iceland. Am. Mineral., Washington, vol. 52, pp. 1815-1841.
CARMICHAEL, I. S. E., TURNER, F. J. & VERHOOGEN, J. (1974)Igneous Petrology. McGraw Hill Book Co., New York.
CARVALHO, D. (1972) - The metallogenetic consequences of plate
tectonics and the upper Paleozoic evolution of southern
Portugal. Est. Not. Trab. Servo Fom. Min., Porto, vol. 20,
pp. 297-320.
- - (1976) - Considera~es sobre 0 vulcanismo da regiao de
Cercal-Odemira. Suas rela<;oes com a Faixa Piritosa. Com.
Servo Geol. Port., Lisboa, t. LX, pp. 215-238.
CARVALHO, D., GOINHAS, J., OLIVEIRA, V. & RIBEIRO, A. (1971) Observa<;oes sobre a geologia do SuI de Portugal e consequencias metalogeneticas. Est. Not. Trab. Servo Fom. Min.,
Porto, vol. 20 (1-2), pp. 153-199.
CHRISTIANSEN, R. L. & LIPMAN, P. W. (1972) - Cenozoic volcanism and plate tectonic evolution of the Western United
States. TI. Late Cenozoic. Phil I. Trans. R. Soc. London, Ser. A,
vol. 271, pp. 249-284.
COISH R. A. & TAYLOR, L. A. (1979) - The effects of cooling
;ate on texture and pyroxene chemistry in DSDP Leg 34
basalt: a microprobe stUdy. Earth Planet. Sci. Lett., Amsterdam, vol. 42, pp. 389-398.
COOMBS D. S. (1963) - Trends and affinities of basaltic magmas
an'd pyroxenes as illustrated on the diopsi~e-olivine-silica
diagram. Miner. Soc. Am., Spec. Pap., Washmgton, vol. I,
pp. 227-250.
DEER, W. A., HOWIE, R. A. & ZUSSMAN, J. (1978) - Single-chain
silicates. Rock Forming Minerals, vol. 2A, Longman, 2nd ed.
ERLANK, A. J. & KABLE, E. J. D. (1976) - The significance of
incompatible elements in Mid-Atlantic ridge basalts from
450 N with particular reference to Zr/Nb. Contr. Min.
Petrol., Berlin, vol. 54, pp. 281-291.
EVANS, B. W. & MOORE, J. G. (1968) - Mineralogy as a function
of depth in the pre-historic Makaopuhi tholeiitic lava lake,
Hawaii. Contr. Min. Petrol., Berlin, vol. 17, pp. 85-115.
EWART, A. (1976) - A petrological study of the younger Tonga
andesites and dacites, and the olivine tholeiites of Nina
Fo'ou islands, SW Pacific. Contr. Min. Petrol., Berlin, vol. 58,
pp. 1-21.
FEBREL, M. T. (1967) - Estratigrafia, tectonica y petrografia en
la zona de Calafias (Huelva). Publicacion de Ie E. N. Adaro,
Madrid, 57 pp.
FLEET, M. E. & BARNETI, R. L. (1978) - Aliv /Alvi partioning in
calciferous amphiboles from the Frood Mine, Sudbury, Ontario. Can. Mineral., Ottawa, vol. 16, pp. 527-532.
FLOYD, P. A. (1982) - Chemical variations of Hercynian basalts
relative to plate tectonics. J. Geol. Soc. London, vol. 139,
pp. 505-520.
FODOR, R. V. (1971) - Fe content in pyroxenes from calc-alkaline
volcanic suite, New Mexico, U.S.A. Earth Planet. Sci. Lett.,
Amsterdam, vol. 11, pp. 385-390.
FODOR, R. V., KEIL, K. & BUNCH, T. E. (1975) - Contributions
to the mineral chemistry of Hawaiian rocks. IV - Pyroxenes in rocks from Haleakala and west Maui volcanoes,
Maui, Hawaii. Contr. Min. Petrol., Berlin, vol. 50, pp.
173-195.
GARCIA, M. 0 (1975) - Clinopyroxene composition, an indicator
of magma type in altered volcanic rocks. Geol. Soc. Amer.
Abstr. with Prog., Boulder, vol. 7, pp. 1082-1083.
GARCIA PALOMERO, F., SAAVEDRA, J. & SANCHEZ, A. G. (1975)Estudio preliminar sobre algunas rocas voIcanicas y volcano-sedimentarias de la Provincia de Huelva. Acta Geol. Hisp.,
Salamanca, vol. X (2), pp. 71-74.
GIBB, F. G. F. (1973) - The zoned clinopyroxenes of the Shiant
Isles sill, Scotland. J. Petrolo/fY, Oxford, vol. 14 (2), pp.
203-230.
GILL, J. B. (1976) - From island arc to ocean island: Fiji, Southwestern Pacific. Geology, Boulder, vol. 2, pp. 123-126.
GROVE, T. L. & BENCE, A. E. (1977) - Experimental study of
pyroxene-liquid interaction in quartz normative basalt 15597.
Proc. Lunar Sci. Con! 8th, pp. 1549-1579.
GRUPTA, A. K., ONUMA, K., YAGI, K. & LIDIAK, E. (1973) - E~fect
of silica activity on the diopside pyroxenes in the system dlopside-CaTiAl20 6-Si02• Contr. Min. Petrol., Berlin, vol. 41,
pp. 333-344.
HOLLISTER, L. S. & GANCARZ, A. J. (1971) - Compositional sector-zoning in clinopyroxene from the Narce area, Italy.
Am. Mineral. Washington, vol. 56, pp. 959-979.
HYNDMAN, D. W. (1972) - Petrology of igneous and metamorphic rocks. McGraw Hill Book Co., New York, 533 pp.
KUSHIRo, I. (1960) - Si-AI relations in cIinopyroxenes from igneous
rocks. Am. J. Sci., New Haven, n.O 258, pp. 548-554.
- - (1972) - Determinations of liquidus relations in synthetic
silicate systems with electron probe analyses. The system
forsterite-diopside-silica at 1 atmosphere. Am. Mineral.,
Washington, vol. 57, pp. 1260-1271.
LE BAS (1962) - The role of aluminium in igneous clinopyroxenes
with relation to their parentage. Am. J. Sci., New Haven,
n.O 260, pp. 267-288.
LECOLLE M. (1977) - La ceinture sud-iberique: un example de
pr~vince it amas sulfures volcano-sedimentaires (tectonique,
metamorphisme, stratigraphie, volcanisme, paleogeo.graphic et
metallogenie). Thesis Univ. Pierre Marie Curie, Pans, 609 PP.
LETERRIER, J., MAURY, R. C., 'FHONON, P., GIRAD, D. & MARCHAL,
M. (1982) - Clinopyroxene compositi?n as a method <?f
identification of the magmatic affinitIes of paleo-volcamc
series. Earth Planet. Sci. Lett., Amsterdam, vol. 59, pp.
139-154.
LOTZE, F. (1945) - Zur gliederung der Varisziden der Iberischru
Meseta. Geotekt. Forsch., Berlin, vol. 6, pp. 78-92.
249.
LoWDER, G. G. (1970) - The volcanoes and caldera of Talasea,
New Britain: Mineralogy. Contr. Min. Petrol., Berlin, vol. 26,
324-340.
- - (1973) - Late Cenozoic transitional alkali olivine tholeiitic
basalt and andesite from the margin of the Great Basin,
southwest Utah. Geol. Soc. Am. Bull., Boulder, vol. 84,
pp. 2993-3012.
MACDONALD, R. (1975) - Tectonic settings and magma associations. Bull. Volcanol., Napoli, vol. 38, pp. 575-593.
MuNHA, J. (1979) - Blue amphiboles, metamorphic regime and
plate tectonic modelling in the Iberian Pyrite Belt. Contr.
Min. Petrol., Berlin, vol. 69, pp. 279-289.
- - (1982) - Spinels in ultramafic rocks from the Iberian Pyrite
Belt. Bol. Soc. Geol. Port., Lisboa, vol. XXIII, pp. 15-20.
- - (1983a) - Low grade regional metamorphism in the Iberian
Pyrite Belt. Com. Servo Geol. Port., Lisboa, t. 69, pp. 3-35.
- - (1983 b) - Hercynian magmatism in the Iberian Pyrite Belt.
Mem. Servo Geol. Port., Lisboa, N. S., n.O 29, pp. 39-81.
MUNHA, J. & KERRICH, R. (1980) - Sea water basalt interaction
in spilites from the Iberian Pyrite Belt. Contr. Min. Petrol.,
Berlin, vol. 73, pp. 191-200.
NASH, W. P. & WILKINSON, J. F. G. (1970) - Shonkin Sag Laccolith, Montana. I. Mafic minerals and estimates of temperature, pressure, oxygen fugacity and silica activity. Contr.
Min. Petrol., Berlin, vol. 25, pp. 241-269.
NICHOLS, J., CARMICHAEL, I.S.E. & STORMER, J. C.-Jr. (1971)Silica activity and Ptota! in igneous rocks. Contr. Min.
Petrol., Berlin, vol. 33, pp. 1-20.
NOBLE, D. C. (1972) - Some observations on the Cenozoic volcano-tectonic evolution of the Great Basin, western United States. Earth. Planet. Sci. Lett., Amsterdam, vol. 17,
pp. 142-150.
OLIVEIRA, J. T. (1983) - The marine Carboniferous of South
Portugal: a stratigraphic and sedimentological approach.
Mem. Servo Geol. Port., Lisboa, N. S., n.O 29, pp. 3-37.
OLIVEIRA, J. T., HORN, M. & PAPROTH, E. (1979) - Preliminary
note on the stratigraphy of the Baixo Alentejo Flysch Group
Carboniferous of Portugal, and on the paleogeographic deve.lopment compared to corresponding units in Northwest,
Germany. Com. Servo Geol. Port., Lisboa, t. 65, pp. 151-168.
PEARCE, J. A. & NORRY, M. J. (1979) - Petrogenetic implications
of Ti, Zr, Y and Nb variations in volcanic rocks. Contr. Min.
Petrol., Berlin, vol. 69, pp. 33-48.
PERFIT, M. R., GUST, D. A., BENCE, A. E., ARCULUS, R. J. & TAYLOR, S. R. (1980) - Chemical characteristics of island-arc
basalts: implications for mantle sources. Chem. Geol., Amsterdam, vol. 30, pp. 227-256.
PRIEM, H. N. A., BOELRIJK, N. A. I. M., HEBEDA, E. H., SCHERMERHORN, L. J. G., VERDURMEN, E. A. T. & VERSCHURE, R. H.
(1978) - Sr isotopic homogenization through whole rock
systems under low greenschist facies metamorphism in Carboniferous pyroclastics at Aljustrel (South Portugal). Chem.
Geol., Amsterdam, vol. 21, pp. 307--314.
RAHMAN, S. (1975) - Some aluminous clinopyroxenes from Vesuvius and Monte Somma, Italy. Min. Mag., London, vol. 40,
pp. 43-52.
RAMBAUD, F. (1969) - El sinclinal Carbonifero de Rio Tinto y sus
mineralizaciones associadas. Mem. Inst. Geol. Min. Esparza,
Madrid, vol. 71, 229 pp.
RANKIN, D. W. (1976) - The continental margin of Eastern North
America in the Southern Appalachians: The opening and
closing of the Proto-Atlantic ocean. Am. J. Sci., New Haven,
n.O 275 a, pp. 298-336.
RIBEIRO, A., IGLEsIAS, M., PEREIRA, E. & REBELO, J. A. (in press)Modelo geodinfunico para 0 segmento iberico do Orogeno
Hercfnico: I Generalidades.
ROUTHIER, P., LECOLLE, M., ROGER, G., AYE, F., MOLIERE, P.,
BOYER, C. & PICOT, P. (1977) - Amas sulfures volcano-sedimentaires. La ceinture sud-iberique a amas sulfures dans
sa partie espagnole mediane. Tableau geologique et metallogenetique. Rapport final de taction concertes. D.G.R.S.T.,
n.O 74-7, pp. 1181.
SAUNDERS, A. D. & TARNEY, J. (1979) - The geochemistry of
basalts from a back-arc spreading centre in the East Scotia
Sea. Geochim. Cosmochim. Acta, Oxford, vol. 43, pp. 555-572.
SAUNDERS, A. D., TARNEY, J., STERN, C. R. & DELZIEL, I. W. D.
(1979) - Geochemistry of Mesozoic marginal basin floor
igneous rocks from southern Chile. Geol. Soc. Am. Bull.,
Boulder, vol. 90, pp. 237-258.
SAUNDERS, A. D., TARNEY, J. & WEAVER, S. D. (1980) - Transverse geochemical variations across the Antartic Peninsula:
implications for the generation of calc-alkaline magmas.
Earth Planet. Sci. Lett., Amsterdam, vol. 46, pp. 344-360.
250
SCHERMERHORN, L. J. G. (1970) - Mafic geosynclinal volcanism
in the lower Carboniferous of South Portugal. Geol. Mijnb.,
Den Haag, n. ° 46 (9), pp. 439-450.
- - (1971) - An outline stratigraphy of the Iberian Pyrite Belt.
Bol. Geol. Min. Espana, Madrid, vol. LXXX (III-IV), pp.
239-268.
- - (1975) - Spilites, regional metamorphism and subduction:
some comments. Geol. Mijnb., Den Haag, n.O 54 (1), pp. 23-35.
SCHERMERHORN, L. J. G. & STATON, W. I. (1969) - Folded overthrusts at Aljustrel (South Portugal). Geol. Mag., London,
vol. 106, pp. 130-141.
SCHWErrZER, E. L., PAPlKE, J. J. & BENCE, A. E. (1979) - Statistical analysis of clinopyroxenes from deep sea basalts. Am.
Mineral., Washington, vol. 64, pp. 501-513.
SCOTT, P. W. (1975) - Crystallization trends of pyroxenes from
alkaline volcanic rocks of Tenerife, Canary Islands. Min.
Mag., London, vol. 40, pp. 805-810.
SMITH, A. L. & CARMICHAEL, A. E. (1968) - Quaternary lavas
from the southern Cascades, Western U.S.A. Contr. Min.
Petrol., Berlin, vol. 19, pp. 212-238.
SMITH, A. L. & CARMICHAEL, I. S. E. (1969) - Quarternary trachybasalts from southeastern California. Am. Minerai.,
Washington, vol. 54, pp. 909-923.
SMITH, D. & LISNDLEY, D. H. (1971) - Stable and metastable crystallization trends in a single basalt flow. Am. Mineral., Washington, vol. 56, pp. 225-233.
SMITH, L. E. M., CHAPPELL, B. W., WARD, G. K. & FREEMAN, R. S.
(1977) - Peralkaline rhyolites associated with andesitic arcs
of the southwest Pacific. Earth Planet. Sci. Lett., Amsterdam, vol. 37, pp. 230-236.
SMITH, R. E. (1968) - Redistribution of major elements in the
alteration of some basic lavas during burial metamorphism.
J. Petrology, Oxford, vol. 9 (2), pp. 191-219.
SOLER, E. (1973) - L'association spilites-quartz keratophyres du
sud west de la Peninsule Iberique. Geol. Mijnb., Den Haag,
n.O 52 (5), pp. 277-288.
STRAUSS, G. K. & MADEL, J. (1974) - Geology of massive sulphide deposits in the Spanish-Portuguese Pyrite Belt. Geol.
Rundschau, Stuttgart, vol. 63 (1), pp. 191-211.
STORMER, J. C.-Jr. (1972) - Mineralogy and petrology of the
Raton-Clayton volcanic field, Northeastern New Mexico.
Geol. Soc. Am. Bull., Boulder, vol. 83, pp. 3299-3322.
THOMPSON, R. N. (1974) - Some high-pressure pyroxenes. Min.
Mag., London, vol. 39, pp. 768-787.
TRACY, R. J. & ROBINSON, P. (1977) - Zoned titanian augite in
alkali olivine basalt from Thaiti and the nature of titanium,
substitutions in augite. Am. Mineral., Washington, vol. 62,
pp. 634-645.
VALLANCE, T. G. (1969) - Spilites again: some consequences of
the degradation of basalts. Proc. Linn. Soc. N.S. W., vol. 91,
pp. 8-51.
- - (1974 a) - Pyroxenes and the basalt-spilite relation. In
Spilites and spilitic rocks, ed. G. C. AMSTUTZ, Springer,
pp.59-68.
- - (1974 b) - Spilitic degradation of a tholeiitic basalt. J. Petrology, Oxford, vol. 15 (1), pp. 79-96.
VEGAS, R. & MUNOZ, M. (1976) - El contacto entre las zonas
Surportuguesa y Ossamorena en SW Espana. Una nueva
interpretacion. Com. Servo Geol. Port., Lisboa, t. LX, pp. 31-52.
VERHOOGEN, J. (1962) - Distribution of titanium between silicates
and oxides in igneous rocks. Am. J. Sci., New Haven, n.O 260,
pp. 211-220.
WEAVER, S. D., SAUNDERS, A. D., PANKHURST, R. J. & TARNEY, J.
(1979) - A geochemichal study of magmatism associated
with the initial stages of back-arc spreading. The Quaternary
volcanics of Bransfield Strait, from South Shetland Islands.
Contr. Min. Petrol., Berlin, vol. 68, pp. 151-169.
WILKINSON, J. F. G. (1956) - Clinopyroxenes of alkali olivine
basalt magma. Am. Mineral., Washington, vol. 41, pp.
724-743.
WOOD, B. J. (1976) - Mixing properties of tschermakitic pyroxenes. Am. Mineral., Washington, vol. 61, pp. 599-602.
WOOD, D. A., JORON, J. L., TREUIL, M., NORRY, M. & TARNEY, J.
(1979) - Elemental and Sr isotope variations in basic lavas
from Iceland and surrounding ocean floor. Contr. Min.
Petrol., Berlin, vol. 70, pp. 319-339.
WOOD, D. A., TARNEY, J. & WEAVER, B. L. (1981) - Trace element
variations in Atlantic ocean basalts and Proterozoic dykes
from northwest Scotland: Their bearing upon the nature
and geochemical evolution of the upper mantle. Tectonophysics, Amsterdam, vol. 75, pp. 91-112.
1.938
.0 ..062
0..024
.0.023
.0 ..002
0.524
0.018
.0.659
.0.735
.0.016
0..000
Si
Allv
Alvl
Ti
Cr
Fe
Mn
Mg
Ca
Na
K
E-24B
LML*
52.78
0.48
2.31
.0.61
6.51
17.77
.0.17
19.16
.0.23
.0 ..00
99.85
E-23D
LML*
52.57
0.59
1.79
.0.61
7.42
17..07
.0.26
19.15
.0.23
.0 ..00
99.69
52.27
0.74
2.66
.0.93
5.85
16.45
.0.18
20.77
.0.18
.0..0.0
1.00 ..05
52.67
0.41
2.61
.0.7.0
6.18
18 ..07
.0.21
2.0.15
.0.29
.0 ..00
101..00
.0 ..0.02
.0..052
0.0.01
0.376
0 ..0.09
.0.739
0.739
0.023
.0.00.0
1.824
.0.176
.0.017
.0 ..016
.0.018
0.229
0..008
.0.939
0.757
0..016
0.00.0
1.939
.0 ..061
.0 ..029
.0 ..013
.0.018
0.199
.0.005
.0.968
.0.751
.0 ..016
DODD
1.93.0
.0 ..07.0
.0 ..008
.0.011
.0.02.0
0.186
.0.006
.0.970
.0.778
.0 ..020
0.00.0
1.897
0.1.03
.0..035
.0 ..02.0
0.027
.0.18.0
.0.006
.0.9.01
.0.818
0.013
.0..000
1.920
.0 ..08.0
A
.0.01.0
.0.042
0..01.0
.0.282
.0•.011
.0.8.09
.0.8.08
0'..028
.0..000
1.87.0
.0.13.0
.0..028
.0..0.02
0.640
.0.773
.0•.02.0
.0 ..017
.0 ..046
0..001
.0.474
1.884
.0.116
49.37
1.41
2.42
.0 ..00
16 ..05
49.51
1.60
2.95
.0 ..02
14.89
11.29
.0.62
18.95
.0.38
.0 ..04
10.0.24
49.89
1.48
3.16
.0.34
9.01
14.48
.035
20.12
.0.38
.0 ..0.0
99.21
\
1.932
.0 ..068
.0..017
.0.042
0..001
0.692
.0 ..027
0.583
.0.619
.0..041
.0.00.0
.0 ..013
.0 ..041
0..000
0.517
.0 ..019
0.599
0.766
.0..046
.0 ..000
49.66
1.42
1.86
.0.02
2.0.54
1.0.06
.0.83
14.86
.0.54
0..00
99.81
A
E-31
1.9.03
.0.097
.0.57
18.54
0.61
.0 ..01
99.41
1.0.44
A
E-31
A
549-1
A
507-18 GA3-5
E-24B
LML*
Number of ions on the basis of 4 cations
48.40
1.83
3.99
.0..02
11.92
13.15
.0.29
19.77
.0.32
.0..0.0
99.77
E-17
LML
electron-miordbe -anailyses of relict igneous clinopy,ro)OOUes
LML -lower mafic lava; * - phenocryst; A - type A dolerite; B - type B dolerite
50.85
0.80
1.91
.0•.05
16.43
11.6.0
.0.57
17.99
.0.21
.0 ..0.0
10.0.41
E-13G
LML
R~resentaifive
81°2
Ti0 2
Al 20 a
Cr2 0 S
FeO
MgO
MnO
CaO
Na2 0
K 20
Total
SamplE
nllhle III:
0.000
.o..o2!!
0.053
0.071
.0 ..012
0.188
0..006
0.756
0.884
1.8.07
.0.193
48.24
2.52
5.59
0.4.0
6..01
13.55
.0.2.0
22 ..04
.0.39
0.00
88.98
495-2
B
.0.035
0.18.0
0..000
0.259
0..005
.0.58.0
.0.878
.0 ..062
0.000
1.599
.0.4.01
42.16
6.31
9.77
.0•.01
8.16
10.26
.0.15
21.62
.0.84
.o.D1
99.22
495-2
B
.0.008
.0.015
0..00.0
.0.5.08
.0.013
.0.5.03
.0.889
0.062
0.000
1.959
.0 ..041
51.34
0.53
1..08
.0..0.0
15.93
8.85
.0.41
21.75
.0.84
.0..01
1.0.0.74
495-6
B
0.0.05
.0 ..049
.0..001
0.593
.0 ..023
0.331
.0.886
.0.111
0.00.0
1.846
.0.154
47.66
1.66
3.49
.0.04
18.3.0
5.74
.0.7.0
21.36
1.48
.0..00
10.0.20
506-8
B
0.002
.0 ..026
.0.000
.0.710
0..028
.0244
081.0
.0.181
.0.000
1.917
.0 ..083
48.98
.0.86
1.83
.0 ..01
21.69
4.18
.0.83
19.32
2.38
.0..0.0
10.0.08
506-8
B
46.59
2.82
6.42
.0.44
6.69
12.67
.0.12
22.83
.0.59
.0 ..0.0
99.17
45.37
3.51
7.24
.0.16
7..02
12.21
.0.23
22.11$
.0.51
.0 ..01
98.44
43.62
5..07
8.88
.0 ..08
7.79
11.15
.0.21
2228
.0.63
0..0.0
99.71
538-14
UML
41.14
6.87
10.68
.0 ..02
8.27
10.4.0
.0.26
22.13
.0.67
.0 ..02
10.0.46
538-14
UML
.0.028
0 ..079
0.013
0210
.0.004
0.7.07
0.916
.0 ..045
0.00.0
1.745
.0.255
.0.034
.0.143
.0 ..002
.0245
.0..007
0.625
0.898
.0 ..046
.0.00.0
1.640
.0.36.0
.0.016
.0.194
0..001
.0.26.0
.0 ..008
0582
0.890
0.049
0..001
1.544
.0.456
.0 ..0.07
.0.123
0001
.0.289
.0 ..007
.0.611
0.906
0..056
.0 ..00.0
1.705
.0.295
45.56
4.36
6.84
.0 ..03
9.25
10.96
.0.22
22.59
.0.77
.0..01
10.0.59
538-14
UML
0.025
.0.006
.0.828
.0.244
.0.005
.0.856
.0 ..017
.0.019
1.836
.0.164
7.94
15.67
.0.17
21..08
.0.35
.0..09
1.00.51
50.07
0.68
4.2.0
477-5
1*
2.022
0.000
.0.718
.0.8.01
0.D18
.0..0.09
0.0.02
.0.418
.0.012
1.917
0..029
13.17
12.69
.0.38
19.7.0
.0.3.0
0..0.0
99.57
.0..05
51.91
.0.30
1..06
.0..029
.0 ..006
.0 ..000
.0.568
0..016
0.562
.0.793
.0..025
0.001
1.989
.0 ..011
51.24
.0.21
.0.87
.0..00
17.5.0
9.71
.0.48
19 ..07
.0.33
.0 ..03
99.45
550-16 550-32
1"'*
1**
UML - upper mafic lava; I - andesite, * - phenocryst, ** - microphenocryst
0.040
.0.10.0
0..0.05
.0.222
.0 ..007
0.689
0.899
.0.037
.0.00.0
1.717
.0293
Number of ions on the basis of 4 cations
538-14
UML
538-5
'IWll
0.032
.0 ..006
0.008
.0.165
0..0.03
.0.901
0.873
.0..012
.0.000
1.938
.0 ..062
52.46
0.23
2.15
.026
5.35
16.36
.0.11
22 ..05
.0.17
.0 ..0.0
99.64
550-32
1*
.0 ..007
0.007
0.318
.0 ..0.09
0.785
0.856
.0.021
0.000
1.934
.0 ..063
51.63
.0.28
1.42
.0.23
10.14
14 ..06
.0.28
20.32
.0.29
.0..0.0
99.54
559-20
1*
.0,018
.0 ..013
.0.265
.0 ..011
0.827
0850
.0..019
.0.000
1.9.02
.0..096
51.59
.0.7.0
2.34
.0.3.0
8.57
15.75
.0.3.0
21.19
.0.26
.0..0.00
1.00.95
559-35
1*
.0.012
.0..010
0..004
.0.22.0
0.003
0.877
0.822
0..05.0
0..001
1.941
.0..059
52.48
.0.37
1.62
0.18
7.11
15.91
.0.11
2.0.73
.0.7.0
.0..03
99.18
567-70
1*