Geology of the Region around Botnneset, East Antarctica (Earth Sciences)

概要

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Geological observations of the Botnneset region, and mineral and chemical compositions of the rock samples collected from the region are presented in this article. The structural and metamorphic history of the region is summarized as follows. First episode : Development of the foldings, probably of an isoclinal type. Metabasites and paragneisses may have been formed during this episode, probably under granulite facies conditions. Second episode : Development of the foliation structure. Formation of brown gneissose granodiorite (charnockite) under earlier granulite and later amphibolite facies conditions. E-W asymmetric folding is considered to have occurred late in this episode. Third episode : Formation of pink gneissose granites and migmatization over wide areas under amphibolite facies conditions. N-S trending open folding is probably the prevailing tectonics. Fourth episode : Development of greenschist facies or a slightly lower metamorphic conditions over wide areas of the region. This is probably attributed to the effect of the late activity of the pink gneissose granites of the third episode.
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