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).

摘要

南极东部拉尔瑟曼山的片麻岩露头是研究普里兹构造带的组成和演化的理想之地。在这项研究中，对拉瑟曼山（Larsemann Hills）Broknes半岛的长直生长片麻岩进行了详细的岩石学分析，相平衡建模和锆石分析。研究结果表明，长英质片麻岩的原生岩为花岗岩，进一步被确定为S型花岗岩。约长976 Ma的长直属片麻岩侵入了地下复合体中。与同一块岩石中的变质锆石相比，长统斜长统中的岩浆锆石具有较低的LREE和较高的HREE含量。长英质片麻岩由矿物组成的石榴石+钛铁矿+斜长石+钾长石+硅线石+石英组成，在格里维利时期（〜899 Ma）经历了粒状相变质作用，峰值条件为〜870°C和〜9.5 kbar。拉森曼山应该归类为格伦维利时期的弧-大陆碰撞到大陆-大陆碰撞的造山过程，地壳增厚（〜899 Ma）和随后的崩塌（550-500 Ma）。