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Schubert, Wolfgang; Olesch, Martin (2011): Tab. 1+2: Representative electron-microprobe analyses of minerals from Du Toit Nunataks. PANGAEA, https://doi.org/10.1594/PANGAEA.763845, Supplement to: Schubert, W; Olesch, M (1995): Cordierite in the Shackleton Range, Antarctica: first recorded occurrence. Polarforschung, 63(2/3), 153-164, hdl:10013/epic.29719.d001

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Abstract:
An example of cordierite-bearing gneiss that is part of a high-grade gneiss-migmatite sequence is described from the Hatch Plain in the Read Mountains of the Shackleton Range, Antarctica, for the first time. The cordierite-bearing rocks constitute the more melanosomic portions of the metatectic and migmatitic rocks that are associated with relict granulite facies rocks such as enderbitic granulite and enderbitic garnet granulite. The predominant mineral assemblage in the cordierite-bearing rocks is chemically homogeneous cordierite (XMg 0.61) and biotite (XMg 0.47), strongly zoned garnet (XMg 0.18-0.11), sillimanite, K-feldspar (Or81-94Ab5-18An0.6), plagioclase (An28), and quartz. Inclusions of sillimanite and biotite relics in both garnet and cordierite indicate that garnet and cordierite were produced by the coupled, discontinuous reaction biotite + sillimanite + quartz = cordierite + garnet + K-feldspar + H2O.
Various garnet-biotite and garnet-cordierite geothermometers and sillimanite-quartz-plagioclase-garnet-cordierite geobarometers yield a continuous clockwise path in the P-T diagram. The P-T conditions for equilibrium between garnet core and cordierite and between garnet core and biotite during peak metamorphism and migmatization were estimated to be 690 °C at 5-6 kb. This was followed by cooling and unloading with continuously changing conditions down to 515 °C at 2-3 kb. This low-pressure re-equilibration correlates with the pressure conditions evaluated by SCHULZE (1989) for the widespread granitic gneisses of the Read Group in the Shackleton Range. The associated relict enderbitic granulites representing low-pressure type granulite (8 kb; 790 °C) are comparable to similar low-pressure granulites from the East Antarctic craton. They were either formed by under-accretion processes after collision (WELLS 1979, p. 217) or they are a product of remetamorphism at P-T conditions intermediate between granulite and amphibolite facies. A model of a multiple imbrication zone with crustal thickening (CUTHBERT et al. 1983) is discussed for the formation of the relict granulites of the central and eastern Read Mountains which show higher pressure conditions (8-12 kb, SCHULZE & OLESCH 1990), indicating a Proterozoic crustal thickness of at least 40 km.
Coverage:
Latitude: -80.766700 * Longitude: -25.750000
Event(s):
Hatch_Plain * Latitude: -80.766700 * Longitude: -25.750000 * Location: Du Toi Nunataks, Read Group, Shackleton Range, Antarctia * Method/Device: Geological sample (GEOS)
Parameter(s):
#NameShort NameUnitPrincipal InvestigatorMethod/DeviceComment
Mineral nameMineralSchubert, Wolfgang
Sample code/labelSample labelSchubert, Wolfgang
CommentCommentSchubert, Wolfgang
Silicon dioxideSiO2%Schubert, WolfgangMicroprobe
Titanium dioxideTiO2%Schubert, WolfgangMicroprobe
Aluminium oxideAl2O3%Schubert, WolfgangMicroprobe
Chromium(III) oxideCr2O3%Schubert, WolfgangMicroprobe
Magnesium oxideMgO%Schubert, WolfgangMicroprobe
Calcium oxideCaO%Schubert, WolfgangMicroprobe
10 Manganese oxideMnO%Schubert, WolfgangMicroprobe
11 Iron oxide, FeOFeO%Schubert, WolfgangMicroprobe
12 Sodium oxideNa2O%Schubert, WolfgangMicroprobe
13 Potassium oxideK2O%Schubert, WolfgangMicroprobe
14 Barium oxideBaO%Schubert, WolfgangMicroprobe
15 SumSum%Schubert, WolfgangMicroprobe
16 Number of oxygensNo OSchubert, WolfgangMicroprobe
17 SiliconSi%Schubert, WolfgangMicroprobe
18 Aluminium (IV)Al(IV)%Schubert, WolfgangMicroprobe
19 --Schubert, WolfgangMicroprobe
20 Aluminium (VI)Al(VI)%Schubert, WolfgangMicroprobe
21 TitaniumTi%Schubert, WolfgangMicroprobe
22 ChromiumCr%Schubert, WolfgangMicroprobe
23 Iron 3+Fe3+%Schubert, WolfgangMicroprobe
24 MagnesiumMg%Schubert, WolfgangMicroprobe
25 CalciumCa%Schubert, WolfgangMicroprobe
26 ManganeseMn%Schubert, WolfgangMicroprobe
27 Iron 2+Fe2+%Schubert, WolfgangMicroprobe
28 SodiumNa%Schubert, WolfgangMicroprobe
29 PotassiumK%Schubert, WolfgangMicroprobe
30 AluminiumAl%Schubert, WolfgangMicroprobe
31 BariumBa%Schubert, WolfgangMicroprobe
32 SumSum%Schubert, WolfgangMicroprobe
Size:
321 data points

Data

Download dataset as tab-delimited text — use the following character encoding:


Mineral

Sample label

Comment

SiO2 [%]

TiO2 [%]

Al2O3 [%]

Cr2O3 [%]

MgO [%]

CaO [%]
10 
MnO [%]
11 
FeO [%]
12 
Na2O [%]
13 
K2O [%]
14 
BaO [%]
15 
Sum [%]
16 
No O
17 
Si [%]
18 
Al(IV) [%]
19 
-
20 
Al(VI) [%]
21 
Ti [%]
22 
Cr [%]
23 
Fe3+ [%]
24 
Mg [%]
25 
Ca [%]
26 
Mn [%]
27 
Fe2+ [%]
28 
Na [%]
29 
K [%]
30 
Al [%]
31 
Ba [%]
32 
Sum [%]
BiotiteW-16835.192.9318.840.1010.230.000.0019.360.239.2796.15225.2862.71480.6210.3310.0122.2900.0000.0002.4320.0671.77715.53
BiotiteW-173rim35.103.4718.910.079.480.000.0018.930.099.6596.70225.3962.60480.7280.3900.0092.1130.0000.0002.3670.0261.83915.47
BiotiteW-173core36.813.3418.880.079.330.010.0519.240.089.6497.44225.4582.54280.7570.3720.0092.0610.0010.0072.3860.0241.82315.44
BiotiteW-168rim36.530.0021.730.122.811.071.8336.71100.80245.8760.12463.9960.0000.0140.6740.1850.2504.93816.06
GametW-173rim36.960.0420.610.092.640.961.7637.61100.67245.9670.03363.8880.0050.0120.0950.6360.1670.2414.98316.03
GametW-173core36.610.0421.120.004.350.920.9935.2599.28245.9200.08063.9440.0060.0000.0501.0490.1590.1364.72316.07
CordieriteW-16848.050.0532.787.520.060.078.600.380.0297.53184.9991.00163.0180.0041.1660.0060.0060.7480.0760.00311.03
CordieriteW-17348.180.0332.947.750.010.148.300.300.0197.66184.9971.00363.0220.0031.1990.0010.0120.7200.0600.00211.02
PlagioclaseW-16860.1325.115.940.007.850.140.0299.1982.6900.2850.0000.6810.0081.3240.0014.99
PlagioclaseW-17361.5624.455.670.028.210.140.00100.0582.7290.2690.0010.7050.0081.2770.0004.99
PerthiteW-17368.7420.270.330.099.262.740.07101.5082.9860.0150.0040.7620.1491.0140.0004.93
K-feldsparW-16862.7118.900.080.030.5114.510.3899.1282.9700.0040.0010.0470.8771.0540.0074.96
MicroclineW-17364.1319.020.130.041.9713.520.4099.2182.9690.0070.0040.1770.7991.0380.0075.00
MicroclineW-16964.8918.490.010.030.3515.860.0399.6682.9970.0010.0010.0310.9341.0060.0014.97