No 13 (2014): Ukrainian Antarctic Journal
Articles

The model of charnockite formation process in Thala hills, East Antarctica

О.В. Miasnikov
State Scientific Institution the Institute for Nature Management, the National Academy of Sciences of Belarus, Minsk
Keywords
  • geological mapping,
  • East Antarctica,
  • Petrogenesis,
  • Petrophysics

Abstract

The research was performed in 2008-2009 within Belarus Government target program with the 54-th Russian Antarctic expedition. Geological mapping was carried out along with geochemical survey of Precambrian basement of Thala hills in western Enderby Land, Antarctica (lat 67°38,7'S ÷ 67°41'S; long 46°02,7'E ÷ 46°14'E). Peculiarities of geophysical fields correspond to the different petrophysical conditions. In the outcrops within Thala hills, the field relations of plagiogneisses facies, migmatitic and plutonic rocks of charnockite and post-tectonic granitoid affinities are well exposed. Four types of main petrographic and petrophysical heterogeneities were singled out: 1) protolyth - relic two pyroxene amphibole, biotite plagiogneisses (pg); 2) intermediate hybrid amphibole-pyroxene-plagioclase-quartz-feldspathic charnockitic enderbites (čeg); 3) enclosing amphibole-feldspathic-quartz-plagioclase charnockites (čg); 4) in cores – ultrametamorphic feldspathic-quartz-plagioclase-amphibole-biotite streamy rapakivi-gneissic charnockites (hybrids) (čmg). The rocks correspond to the dominant processes of tectonic thermal activation of the four geochronological borders. The rocks architectonics reflects evolutionary succession of events, i.e. a change of direction of granitization processes from lateral (↔) crustal to vertical (↕) intrusive ones. The territory structure of Thala hills is represented as an ordered linear-dome model of Precambrian structural and compositional evolution: protolyth plagiogneiss ↔, intermediate charnockitic enderbite ↔, enclosing charnockite ↔, core - streamy rapakivioid charnockite.