Fig. 2. Sample photographs and photomicrographs showing: A. Rhyolitic dykes cross-cutting tholeiitic basalts, typically with plagioclase Pl phenocrysts and corroded quartz Qz; B. Heteradcumulate texture of a wehrlite; serpentinized olivine S.Ol,
chromite Chr; C. Post-cumulus clinopyroxene Cpx and brown amphibole Am in wehrlite; D. Relic grains of fresh olivine Ol enclosed in orthopyroxene Opx; magnetite Mt; E. Post-cumulus amphibole and biotite Bi, partially pseudomorphosed into
chlorite in wehrlite; F. Layered gabbro; G. Differentiated gabbro; ilmenite Ilm; H. CaKa X-ray map of a clinopyroxene containing thin lamellae of chlorite.
with the layered gabbro-magnetite with thin lamellae of exsolved ilmenite.
4. Mineralogy
More than a hundred electron-microprobe analyses were performed using a CAMEBAX SX
50 instrument at the Laboratoire de Mineralogie, Toulouse beam current of 10 or 20 nA depending
on the mineral’s resistance to beam damage, 15 kV, with counting times of 10 s at peak positions
and 5 s for backgrounds. The data were cor- rected using PAP SX50 procedures a list of the
standards used is available from the authors upon request. Concentrations of major elements are
accurate to 1 wt of the element present, whereas concentrations of minor elements are less accu-
rate, being reproductible to 0.1 wt.
Representative compositions of olivine, pyroxe- nes, spinel, and amphiboles obtained only from
mafic and ultramafic rocks are given in Tables 1 – 4. Relics of primary igneous phenocrysts are
not observed in the volcanic rocks.
4
.
1
. Oli6ine Some rare relic olivine grains were found in the
wehrlites Fig. 2D. They are unzoned and show a more limited compositional range Fo85 – 84,
Fig. 2. Continued
with NiO reaching a maximum of 0.40 wt Table 1. In terms of both Ni and Fo contents,
the olivine compositions are consistent with a mantle-derived origin Sato, 1977, being compat-
ible with the compositions of olivine in cumulates crystallizing from the melt fraction.
4
.
2
. Pyroxenes Selected compositions of different types of py-
roxene are listed in Table 1. In wehrlite, the orthopyroxene is enstatite of mean composition
Wo
5
En
80
Fs
15
, while the clinopyroxene varies from Mg-augite Wo
32 – 44.5
En
48 – 58
Fs
7.5 – 10
to diopside Wo
47
En
47
Fs
6
for clinopyroxene con- taining thin lamellae of chlorite along the 100
crystallographic planes Fig. 2H Fig. 3. This difference of composition could result from the
reaction Mg-augite diopside + orthopyroxene,
the chlorite lamellae representing relictual or- thopyroxene exsolution lamellae. The clinopyrox-
ene in the gabbros is Mg-augite, with lower Cr
2
O
3
and Al
2
O
3
contents Fig. 4 than in the clinopy- roxene of wehrlites. The strong positive correla-
tion between Al
2
O
3
and Cr
2
O
3
suggests that charge balance is maintained by a CaCrAlSiO
6
- type substitution. CaO contents are highly vari-
able in all clinopyroxenes, which may reflect submicroscopic orthopyroxene exsolution lamel-
lae resulting in large variations in Wo and corre- spondingly also in En components. However, the
range in magnesium number mg = 100Mg Mg + Fe
2 +
is more limited in both the clinopy- roxenes
0.90 – 0.85 and
orthopyroxenes 0.88 – 0.84, Table 1.
Table 1 Representative microprobe analyses of olivine and pyroxenes
a
1 Analysis
2 3
4 5
6 7
8 9
W W
W W
LG Host rock type
EG W
W W
Cpx Cpx
Opx Chlorit.-Cpx
Cpx Cpx
Cpx Ol
Ol SiO
2
51.97 53.29
52.94 55.61
54.19 52.60
52.96 39.96
39.69 0.08
0.22 0.06
0.03 T
I
O
2
0.12 0.19
0.16 -
- 2.48
2.62 1.77
1.20 2.42
2.68 1.71
Al
2
O
3
- -
4.58 FeO
4.04 5.87
9.51 3.83
5.60 8.14
14.70 14.62
0.89 0.92
0.56 0.47
0.64 Cr
2
O
3
0.04 1.03
0.05 0.05
0.21 0.15
0.17 0.19
0.30 0.16
0.38 MnO
0.23 0.16
16.98 MgO
18.76 18.95
30.41 16.50
16.32 12.17
44.66 45.28
19.11 18.12
CaO 2.14
21.88 23.29
21.67 23.70
0.06 0.02
0.37 0.21
0.03 0.34
0.32 0.24
0.82 Na
2
O -
- 0.00
K
2
O 0.01
0.00 0.01
0.04 0.03
0.02 -
- 99.24
100.00 100.27
100.08 100.02
Total 100.10
99.71 99.99
100.16 39.38
36.84 4.12
47.16 Wo
44.24 44.47
50.12 Fo
0.84 0.85
En 48.01
53.78 53.61
81.36 46.49
46.36 35.81
Fa 0.16
0.15 6.84
9.56 Fs
14.53 7.52
6.36 9.41
14.07
a
In W: wehrlite; LG: layered gabbro; EG: evolved gabbro; Chlorit-Cpx: clinopyroxene containing thin lamellae of chlorite.
In the more evolved gabbros, clinopyroxene is diopside Wo
50
En
36
Fs
14
. It differs from the clinopyroxene of wehrlites and gabbros in having
lower mg B 80, Al
2
O
3
and Cr
2
O
3
Fig. 4 and higher CaO, Na
2
O and FeO contents.
4
.
3
. Spinel Spinel is mostly encountered in ultramafic cu-
mulates, more rarely in the gabbros and basalts. Selected
compositions of
different types
of chromite are listed in Table 2. They correspond to
chromite, with only one grain having the compo- sition of magnesio-chromite MgM
2 +
\ Fe
2 +
M
2 +
, Table 2. Chromite is dispersed throughout the entire volume of the ultramafic cumulates. It
occurs as 200 – 400 mm euhedral to rounded grains included in olivine, interstitial to olivine, or in-
completely enclosed by olivine and in partial con- tact with postcumulus phases Fig. 2B, C and D.
Compositional zoning within individual grains is not observed; only a thin ferritchromite rim is
developed along boundaries in individual grains located in secondary serpentine or chlorite phases.
When plotted against Mg ratio = MgMg + Fe
2 +
, chromite exhibits similar Cr contents but a distinct inverse relationship between Al and Fe
3 +
, except those having a Mg ratio B 0.2 which
shows more scattered trivalent cation contents Fig. 5. TiO
2
also correlates positively with Fe
3 +
Fig. 6. These compositional variations indicate a spinel-magnetite type-substitution.
No significant differences in chemistry exist be- tween chromites in dunites or wehrlites. However,
significant differences exist among interstitial chromites entirely included in either clinopyrox-
ene or amphibole. These chromites are distinctly Al-poor and Fe
3 +
-rich, while most of them are Mg-rich compared with chromites included or
incompletely enclosed by olivine. Fractional crystallization can be excluded as a
major cause of the compositional variation of chromites because of the slight change in Cr
content relative to their Mg ratio Hulbert and Von Gruenewaldt, 1985; Leblanc, 1985. So, the
chemical characteristics of chromite are in part a result of hydrothermal alteration processes and
metamorphism which affect the host rocks, with dissolution-recrystallization
from magmatic
chromite to Mg-Al-poor and Fe
2 +
-Fe
3 +
-rich
D .
Be ´ziat
et al
. Precambrian
Research
101 2000
25 –
47
33
Table 2 Representative microprobe analyses of spinel
a
5 6
7 8
9 10
Analysis 11
1c 12
13 1r
2 3
4 W
W W
W W
W LG
W LG
Host rock B
D D
D D
S.Ol S.Ol-Am
Cpx Am
S.01-Bi Bi
S.Ol Related silicate
Am S.Ol
Trem S.Ol
S.Ol-Cpx Cpx
Ol 0.05
0.01 0.12
0.00 0.01
0.00 0.09
0.00 0.09
0.45 0.10
0.00 SiO
2
0.02 0.08
16.24 13.75
20.23 11.78
12.51 6.79
Al
2
O
3
19.21 16.68
16.87 13.40
17.03 16.04
17.32 18.90
34.47 38.12
24.75 48.74
42.11 57.47
30.16 34.12
38.36 FeO
35.19 29.91
31.97 33.35
31.48 0.41
0.29 0.36
0.32 0.24
0.27 0.35
0.74 0.18
1.33 1.68
0.46 0.28
MnO 0.34
6.33 6.18
11.84 6.27
5.56 2.32
8.93 7.16
1.44 MgO
0.35 9.78
8.75 7.30
8.49 0.66
1.61 0.39
0.14 0.82
3.10 0.50
TiO
2
0.35 0.72
0.20 0.64
1.74 1.64
0.43 40.15
38.21 42.93
30.17 37.15
27.26 39.11
37.66 37.75
Cr
2
O
3
44.49 38.80
39.62 38.75
39.90 0.00
0.00 0.00
0.00 0.08
0.20 0.15
0.11 0.00
0.00 0.00
0.00 0.00
0.00 ZnO
0.66 0.20
0.09 0.28
0.22 0.25
0.17 0.43
0.16 0.04
0.07 NiO
0.15 0.18
0.17 98.99
97.85 98.92
98.40 100.67
97.85 98.88
98.04 98.26
96.71 95.48
97.65 98.66
98.06 Total
0.002 0.000
0.004 0.000
0.000 0.000
0.000 0.016
Si 0.004
0.001 0.003
0.003 0.003
0.000 0.633
0.542 0.738
0.470 0.496
0.281 0.731
0.724 0.697
0.659 0.574
Al 0.645
0.664 0.614
0.300 0.408
0.202 0.718
0.494 0.881
0.259 Fe
3+
0.248 0.303
0.144 0.305
0.325 0.311
0.298 0.654
0.658 0.439
0.662 0.692
0.807 0.555
0.630 0.877
Fe
2+
0.925 0.496
0.543 0.618
0.561 0.010
0.009 0.006
0.008 0.010
0.022 0.005
Mn 0.039
0.011 0.052
0.013 0.008
0.009 0.008
0.312 0.308
0.547 0.317
0.279 0.121
0.430 0.347
0.075 0.471
0.019 Mg
0.415 0.360
0.424 0.016
0.040 0.009
0.004 0.021
0.082 0.012
Ti 0.009
0.018 0.005
0.016 0.043
0.040 0.011
1.050 1.010
1.051 0.808
0.989 0.757
0.998 0.968
1.046 Cr
1.277 0.990
1.018 1.014
1.035 0.000
Zn 0.000
0.000 0.002
0.005 0.004
0.003 0.000
0.000 0.000
0.000 0.000
0.000 0.000
0.015 0.005
0.002 0.007
0.005 0.006
0.004 0.010
0.004 Ni
0.002 0.003
0.004 0.004
0.001 0.525
0.505 0.525
0.404 0.494
0.378 CrM
3+
0.499 0.517
0.523 0.639
0.507 0.509
0.495 0.484
0.317 0.271
0.369 0.235
0.248 0.140
0.365 0.362
0.348 AlM
3+
0.287 0.329
0.307 0.332
0.322 Fe
3+
M
3+
0.150 0.151
0.204 0.101
0.359 0.247
0.440 0.129
0.124 0.072
0.153 0.163
0.156 0.149
0.670 0.675
0.442 0.668
0.703 0.846
0.561 0.640
0.884 0.508
0.929 Fe
2+
M
2+
0.568 0.623
0.557 0.320
MgM
2+
0.316 0.420
0.550 0.319
0.284 0.127
0.434 0.076
0.019 0.364
0.435 0.482
0.352
a
c: core; r: rim; D: dunite; W: wehrlite; LG: layered gabbro; B: basalt; spinels included in fresh olivine Ol, in serpentinized olivine S.Ol and in partial contact with clinopyroxene S.Ol-Cpx, amphibole S.Ol-Am or biotite S.Ol-Bi, in clinopyroxene Cpx, in amphibole Am, in biotite Bi and in tremolite Trem.
chromites, leading to the complete late-stage transformation to ferritchromite Jan et al., 1985;
Kimball, 1990; Be´ziat and Monchoux, 1991; Liipo et al., 1995. The low Mg
contents of chromite grains trapped in olivine could result from subsolidus re-equilibration be-
tween chromite and olivine Wilson, 1982; Hatton and Von Gruenewaldt, 1985; Roeder and Camp-
bell, 1985; Yang and Seccombe, 1993; Scowen et al., 1991. On the contrary, their generally high Al
contents could be inherited from the magmatic stage because Al partitions preferentially into the
Al silicates Eales and Marsh, 1983 causing a relative decrease of Al in the interstitial chromite
relative to the cumulus chromite where the only cocumulus phase is olivine.
4
.
4
. Amphiboles Brown amphibole frequently coexists with
clinopyroxene in ultramafic cumulates Fig. 2C and layered gabbros, while green amphibole oc-
curs in the isolated massive gabbros and the vol- canic sequence. Using IMA nomenclature 1997,
Table 3, they range in composition, respectively, from pargasite to edenite and from magnesio-
hornblende to actinolite. Tremolite occurs as a selvage in these amphiboles and is also as pseudo-
morph of serpentine in contact with chlorite.
Amphibole compositions Fig. 7 fall into two distinct groups. Brown amphibole has high Al
IV
, Ti, Na and K and low Si. Green and colourless
amphiboles have low Al
IV
, Ti, Na and K and high
Table 3 Representative microprobe analyses of amphiboles
a
4 Analysis
5 1
6 7
2 3
W B
Do Di
G W
W Host rock
44.18 50.73
41.84 43.59
43.75 43.04
SiO
2
44.95 4.06
0.16 0.48
3.77 3.51
3.37 TiO
2
2.32 13.01
4.65 10.14
10.32 Al
2
O
3
10.30 10.65
10.79 0.06
0.01 0.08
0.25 Cr
2
O
3
0.72 1.02
0.15 FeO
22.18 15.55
9.63 12.05
6.57 7.56
7.72 0.28
0.31 0.16
0.42 0.04
0.10 0.01
MnO 12.94
16.37 6.33
16.23 16.41
13.66 13.98
MgO 11.55
11.54 11.50
CaO 11.05
11.79 11.91
11.08 2.47
2.60 3.02
Na
2
O 2.45
2.03 0.74
1.91 0.59
0.35 K
2
O 0.23
0.63 0.35
0.67 0.48
Cl 0.00
0.00 0.05
0.02 0.00
0.00 0.00
0.00 F
0.00 0.19
0.00 0.00
0.00 0.00
97.16 96.62
97.39 97.99
95.56 Total
97.2 97.68
6.471 7.487
6.416 6.378
Si 6.456
6.409 6.438
1.584 0.513
1.529 1.562
Al
IV
1.544 1.622
1.591 0.769
0.256 Al
Vl
0.249 0.216
0.259 0.495
0.297 Cr
0.018 0.029
0.083 0.119
0.007 0.001
0.010 0.000
0.000 0.000
0.000 0.059
Fe
3+
0.000 0.000
0.260 0.379
0.018 0.055
0.443 Ti
0.415 0.390
3.539 3.609
3.045 3.539
3.110 Mg
2.846 1.447
0.936 0.925
0.811 1.508
1.202 1.919
2.786 Fe
2+
0.035 0.001
0.055 0.012
0.005 0.020
0.039 Mn
1.884 1.795
1.821 1.809
1.818 1.771
1.886 Ca
0.568 0.212
0.588 0.711
Na 0.864
0.738 0.695
0.067 0.043
0.068 K
0.109 0.118
0.090 0.128
0.79 0.34
0.59 0.72
0.67 0.79
0.82 mg
a
In D: dunite; W: wehrlite; LG: layered gabbro; EG: evolved gabbro; IG: isolated massive gabbro; B: basalt.
Fig. 3. Compositional variation of pyroxenes. Orthopyroxene , clinopyroxene 2 and clinopyroxene containing thin
lamellae of chlorite from wehrlite; clinopyroxene from
layered and more differentiated
gabbros.
MgO and Cr
2
O
3
Table 3 are depleted in more differentiated gabbros relative to the cumulate
amphiboles.
4
.
5
. Feldspar In the different lithological facies, plagioclase is
always pseudomorphed into albite.
4
.
6
. Accessory phases Late magmatic biotite, rimming brown amphi-
bole Fig. 2E and clinopyroxene, is present within the wehrlites and gabbros. They clearly
differ from biotites of metamorphic origin en-
Fig. 5. Compositional variation of chromites. Dunite: included chromite in serpentinized olivine
, partly in contact with
clinopyroxene |stop10| and entirely within clinopyroxene . Wehrlite: included chromite in serpentinized olivine 2,
fresh olivine , clinopyroxene or amphibole and biotite
; partly in contact with clinopyroxene or amphibole and biotite
. Gabbro: chromite included in serpentinized olivine and amphibole . Basalt .
Fig. 4. Cr
2
O
3
vs. Al
2
O
3
in clinopyroxenes.
Si. The reasonably good linear correlation shown in Fig. 7 between Al
IV
and Na + K parallel to the tremolite-pargasite line indicate that the substitu-
tion mechanism operative in both amphiboles is principally of the edenite type Na + K
A
+ Al
IV
A
+ Si. A simple Mg for Fe
2 +
substitution is also operative. As with the clinopyroxenes, both
D .
Be ´ziat
et al
. Precambrian
Research
101 2000
25 –
47
Table 4 Representative whole-rock chemical analyses
a
5 1
6 7
8 9
10 11
12 13
14 15
2 3
4 Sample
LG EG
EG IG
Do CAB
And Ca-CAB
Rh D
ThB W
W LG
LG 52.6
59.6 58.0
47.5 48.0
51.5 57.8
44.7 44.0
SiO
2
66.0 46.1
49.5 40.3
37.1 36.1
0.08 0.46
0.80 1.37
3.06 1.08
1.24 0.60
0.70 0.46
0.32 1.17
0.06 0.17
TiO
2
0.20 13.2
15.2 16.4
14.1 14.2
13.9 14.0
Al
2
O
3
15.6 3.0
14.8 14.0
5.4 5.7
9.9 17.9
5.7 3.2
3.7 14.5
15.7 8.7
8.2 7.4
7.2 10.3
2.6 11.3
9.5 Fe
2
O
3
12.3 10.9
0.11 0.15
0.11 0.08
0.24 0.20
0.22 0.12
0.11 0.11
0.03 0.17
0.15 0.15
0.16 MnO
9.5 2.8
2.3 5.8
5.6 8.6
3.6 MgO
6.4 36.3
0.9 5.5
30.5 27.3
15.3 5.9
10.3 7.2
6.5 8.9
10.5 8.4
9.2 8.8
7.5 0.9
3.1 8.9
CaO 7.7
3.7 3.1
4.6 0.08
4.0 8.2
7.9 3.4
0.9 3.2
2.6 2.8
6.7 1.4
0.04 0.24
1.9 Na
2
O 0.37
0.21 0.01
0.40 0.09
0.13 0.15
1.30 K
2
O 1.35
0.03 0.01
0.01 0.01
0.01 0.39
0.13 0.18
0.22 0.19
0.16 0.18
0.23 0.05
0.08 0.01
0.11 0.16
P
2
O
S
0.03 0.01
0.01 3.1
11.1 2.3
1.1 1.6
2.0 3.0
3.3 2.7
13.7 2.9
9.4 10.3
9.7 8.0
LOI 99.01
99.14 99.93
98.07 99.61
98.53 99.09
99.05 Total
98.81 100.05
98.11 97.57
96.88 97.36
98.11 750
43 265
37 62
109 40
647 98
Cr 8
38 68
799 362
650 1080
55 243
133 38
28 47
20 13
31 6
28 874
763 Ni
254 33
16 10
5 42
5 6
Co 21
78 27
24 79
71 35
20 74
66 91
121 310
50 72
2 115
7 40
171 2
Sc 7
4 36
15 174
196 3
3 2
3 3
2 4
2 16
38 39
V 2
3 4
12 8
10 15
Pb 21
30 10
1 1
1 2
6 6
0.31 0.28
0.13 0.09
0.15 9
0.58 1
0.63 0.37
Rb 1
3 5
0.00 0.00
0.11 0.19
660 93
30 139
210 100
482 20
0.13 1.03
0.08 Cs
550 Ba
355 5
1227 215
212 503
192 188
215 9
18 61
10 752
0.89 0.13
0.16 0.18
0.23 44
0.09 22
0.15 0.18
54 Sr
1 12
1.04 0.42
0.28 0.81
20.00 2.20
2.60 2.80
3.50 0.70
2.80 2.70
0.05 0.07
0.07 Ta
5.10 11.90
2.72 0.81
1.01 1.29
1.36 Nb
0.69 0.30
3.39 1.03
0.10 0.50
0.60 2.20
2.97 6.39
180 31
38 40
80 0.80
29 0.08
121 40
Hf 0.45
0.42 0.11
43 5
90 186
46 10
14 20
10 3
6 21
3 14
10 Zr
40 55
3.95 0.32
0.35 1.10
0.71 0.36
Y 2.17
2 0.24
2 5
7 9
1.41 4.52
1.36 0.12
0.12 0.30
0.34 0.33
0.10 0.05
0.85 0.09
0.24 0.20
Th 0.04
0.11 0.02
0.44 1.26
22.23 7.24
6.76 11.87
9.97 4.49
15.74 5.39
0.02 0.07
0.07 U
11.61 36.87
.06 2.40
2.30 3.32
2.98 La
1.35 0.59
4.10 2.01
0.65 1.73
2.04 4.79
28.61 73.40
25.12 10.14
10.32 13.00
13.01 10.53
5.52 0.00
16.06 9.70
Ce 4.45
3.84 1.40
1.32 0.16
4.08 8.83
6.22 2.39
2.50 2.52
2.91 1.16
2.73 2.66
0.18 0.49
0.59 Pr
Nd 18.33
0.70 34.33
1.47 0.93
0.97 0.79
0.94 0.39
0.69 1.03
0.76 2.11
2.50 5.76
4.72 7.48
6.54 2.48
3.01 2.17
2.83 1.23
1.05 0.16
2.03 2.94
Sm 0.69
0.53 0.18
0.50 0.06
1.07 1.30
1.22 0.44
0.52 0.34
0.46 0.13
0.26 0.56
0.09 0.21
0.24 Eu
5.61 8.73
8.22 2.92
3.49 2.06
2.89 Gd
0.63 0.22
1.23 3.57
0.21 0.60
0.81 1.54
1.03 1.52
1.80 0.68
0.77 0.46
0.63 0.23
0.13 0.04
0.20 0.81
Tb 0.16
0.12 0.04
1.33 0.23
6.72 9.63
5.22 2.00
2.26 1.31
1.82 0.35
0.57 2.26
0.31 0.87
1.12 Dy
1.53 Ho
2.19 0.06
0.74 0.29
0.33 0.20
0.27 0.05
0.07 0.32
0.07 0.20
0.27 0.29
4.50 6.20
4.66 1.97
2.27 1.36
1.79 0.88
0.37 0.63
0.39 2.07
0.80 Er
0.18 0.22
0.12 0.03
0.64 0.83
0.70 0.30
0.35 0.21
0.27 0.07
0.08 0.31
0.03 0.10
0.12 Tm
4.06 Yb
5.54 0.19
0.24 0.67
0.84 0.79
0.59 0.88
0.12 Lu
0.03 0.04
0.10 0.14
a
D: dunite; W: wehrlite; LG: layered gabbro; EG: evolved gabbro; IG: isolated massive gabbro; Do: dolerite; CAB: calc-alkaline basalt; And: andesite; Ca-CAB: carbonatized calc-alkaline basalt.
Fig. 6. Ti versus Fe
3 +
in chromites.
SiO
2
plot Fig. 8, the Loraboue´ basaltic rocks are clearly distributed on both sides of the Miyashiro
1974 discriminant boundary. A first group made up of dolerites, isolated massive gabbros and
some basalts is tholeiitic, while the second group, made up of basaltic rocks, evolved gabbros and
rhyolites is calc-alkaline. The chronology can be established on the field, dykes of rhyolite cross-
cutting basalts of the first group Fig. 2A, anal. 14 in Table 4. Due to their cumulative nature, the
Fig. 7. Compositional variation of amphiboles. Al
IV
, Na + K and Ti in atoms p.f.u.
countered in the volcanic sequence in having higher TiO
2
1.5 – 3 wt and Cr
2
O
3
0.5 – 0.7 wt contents. Mn-rich ilmenite \ 5 wt MnO
partially replaced by titanite, apatite and zircon are common accessories in the more differentiated
gabbros Fig. 2G. Magnetite and Ni-Fe sulphide heazlewoodite and pentlandite are common by-
products of the serpentinization of olivine in ul- tramafic
cumulates and
gabbros. However,
Ti-magnetite is present as a primary phase in the isolated massive gabbros, dolerites and the vol-
canic sequence.
5. Geochemistry
