Petrography, microprobe analyses and isotope composition of ultramafic rock from the northern Haskard Highlands, Shackleton Range, East Antarctica ...
In the Shackleton Range of East Antarctica, garnet-bearing ultramafic rocks occur as lenses in supracrustal high-grade gneisses. In the presence of olivine, garnet is an unmistakable indicator of eclogite facies metamorphic conditions. The eclogite facies assemblages are only present in ultramafic r...
| Main Authors: | , , |
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| Format: | Article in Journal/Newspaper |
| Language: | English |
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PANGAEA
2009
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| Subjects: | |
| Online Access: | https://dx.doi.org/10.1594/pangaea.849763 https://doi.pangaea.de/10.1594/PANGAEA.849763 |
| Summary: | In the Shackleton Range of East Antarctica, garnet-bearing ultramafic rocks occur as lenses in supracrustal high-grade gneisses. In the presence of olivine, garnet is an unmistakable indicator of eclogite facies metamorphic conditions. The eclogite facies assemblages are only present in ultramafic rocks, particularly in pyroxenites, whereas other lithologies - including metabasites - lack such assemblages. We conclude that under high-temperature conditions, pyroxenites preserve high-pressure assemblages better than isofacial metabasites, provided the pressure is high enough to stabilize garnet-olivine assemblages (i.e. >=18-20 kbar). The Shackleton Range ultramafic rocks experienced a clockwise P-T path and peak conditions of 800-850 °C and 23-25 kbar. These conditions correspond to ~70 km depth of burial and a metamorphic gradient of 11-12 °C/km that is typical of a convergent plate-margin setting. The age of metamorphism is defined by two garnet-whole-rock Sm-Nd isochrons that give ages of 525 ± 5 and ... : Supplement to: Romer, T; Mezger, Klaus; Schmädicke, Esther (2009): Pan-African eclogite facies metamorphism of ultramafic rocks in the Shackleton Range, Antarctica. Journal of Metamorphic Geology, 27(5), 335-347 ... |
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