Abstract
ABSTRACT The gneisses outcropping in the Larsemann Hills of East Antarctica are ideal for studying the composition and evolution of the Prydz tectonic belt. In this study, detailed petrological analyses, phase equilibrium modelling, and zircon analyses were performed on a felsic orthogneiss from the Broknes Peninsula in the Larsemann Hills. The study results show that the protolith of the felsic gneiss is granite, which is further identified to have been an S-type granitoid. The felsic orthogneiss intruded into the basement complex at ~976 Ma. The magmatic zircons in the felsic orthogneiss have lower LREE and higher HREE contents than those of the metamorphic zircons in the same rock. The felsic gneiss consists of the mineral assemblage garnet +ilmenite+ plagioclase +K-feldspar + sillimanite + quartz and underwent granulite facies metamorphism in the Grenvillian period (～899 Ma), with peak conditions of ～870°C and ～9.5 kbar. The Larsemann Hills should be categorized as the orogenic process from arc-continent collision to continent-continent collision during the Grenvillian period, crust thickening(~899 Ma) and subsequent collapse(550–500 Ma).
Highlights
There are different perspectives on the tectonic evolution of Prydz Bay of East Antarctica: P-T paths with clockwise near isothermal decompression (ITD) indicate that it is a Pan-African collision orogeny related to crustal thickening (Ren et al 1992, 2018; Fitzsimons 1996; Carson et al 1997; Yu et al 2002; Liu et al 2006, 2007a, 2007b, 2007c; Hu et al 2008)
The Larsemann Hills are located in the heart of Prydz Bay, and the Broknes Peninsula is a major part of the Larsemann Hills
There have been a lot of studies performed on the basement complex in Prydz Bay
Summary
There are different perspectives on the tectonic evolution of Prydz Bay of East Antarctica: P-T paths with clockwise near isothermal decompression (ITD) indicate that it is a Pan-African collision orogeny related to crustal thickening (Ren et al 1992, 2018; Fitzsimons 1996; Carson et al 1997; Yu et al 2002; Liu et al 2006, 2007a, 2007b, 2007c; Hu et al 2008). Others believe that the two tectonic metamorphic events represent the aggregation of the continents of Rodinia and Gondwana, respectively, and that the Prydz tectonic belt is a collisional orogenic belt (Hensen and Zhou 1997; Fitzsimons 2000; Boger et al 2001; Liu et al 2002b, 2006; Zhao et al 2003; Li and Liu 2006) Resolving these differences in perspectives is important for understanding how the East Antarctic continent formed. An in-depth study of the rocks at these locations is important for establishing a complete metamorphic P-T path in this area, and is of great significance to clarify the metamorphic thermal evolution and tectonic nature of Prydz Bay
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