The Archaean geological evolution of Enderby Land, Antarctica
- 1 January 1987
- journal article
- Published by Geological Society of London in Geological Society, London, Special Publications
- Vol. 27 (1) , 285-296
- https://doi.org/10.1144/gsl.sp.1987.027.01.24
Abstract
The Napier Complex of Enderby Land, Antarctica, is a major terrain exhibiting Archaean granulite-facies metamorphism at extreme PT conditions. Combined Rb-Sr, Sm-Nd and U-Pb zircon isotope systematics define an age of 3070 Ma for initial granulite-facies metamorphism and intense D1 deformation. Orthogeneissic sheets intruded into the tectonically thickened crust at times up to 3070 Ma resulted in the attainment of peak regional metamorphic conditions of 950°C and 7–10 kb subsequent to D1. These high-grade conditions prevailed through a second, less intense, deformation (D2) after which the Napier Complex became a stable craton for some 500 Ma. The presently exposed granulites record a near-isobaric cooling path over this time interval prior to reactivation at 700–650°C and 5–8 kb in a deformation event (D3) at c. 2450 Ma. The D3 event resulted in open dome-and-basin folding of the pre-existing recumbent- and isoclinally-folded pile. Protolith ages for some granulite-facies gneisses, obtained from conventional and ion-microprobe investigation of zircons and deduced from Sm-Nd modelling, are in the range 3750–3950 Ma, some 700–900 Ma prior to the first recognized metamorphism.Keywords
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