Paragenetic and mineral‐chemical relationships in orthoamphibole‐bearing gneisses from Enderby Land, east Antarctica: a record of Proterozoic uplift
Abstract Polymetamorphic orthoamphibole‐bearing gneisses from the vicinity of shear zones in Casey Bay, Enderby Land, Antarctica, record both the overprinting of Archaean granulite lithologies by Proterozoic metamorphism and the subsequent evolution of the latter episode during localized deformation...
| Published in: | Journal of Metamorphic Geology |
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| Format: | Article in Journal/Newspaper |
| Language: | English |
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Wiley
1985
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| Online Access: | http://dx.doi.org/10.1111/j.1525-1314.1985.tb00313.x https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1525-1314.1985.tb00313.x https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1525-1314.1985.tb00313.x |
| Summary: | Abstract Polymetamorphic orthoamphibole‐bearing gneisses from the vicinity of shear zones in Casey Bay, Enderby Land, Antarctica, record both the overprinting of Archaean granulite lithologies by Proterozoic metamorphism and the subsequent evolution of the latter episode during localized deformation. Mineral chemistry and zoning relationships in orthoamphibole‐garnet‐kyanite‐quartz and later orthoamphibole‐garnet‐cordierite‐quartz assemblages are used together with interpretation of reaction and corona textures to constrain the Proterozoic pressure‐temperature path experienced by the rocks. Consideration of reaction topologies, P‐T‐X(Fe‐Mg‐A1) relationships in orthoamphibole‐bearing assemblages, and standard geothermobarometry indicate that the gneisses underwent a near‐isothermal decompression P‐T history (steep positive dP/dT) from ± 8 kbar and 700°C to <5.5kbar and 650°C. This uplift path is correlated with the general effects of Rayner Complex metamorphism and deformation which occurred after 1100 Ma in a major erogenic belt south of Casey Bay. |
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