Igneous activity and petrogenesis of Late Proterozoic (Grenville Period) intrusions in the Sor Rondane Mountains, East Antarctica

本文对南极索朗丹山脉晚元古代的入侵进行了详细的研究。岩体岩性分为强片麻岩变长岩、弱片麻岩变长岩和变长岩3种。主要岩型为强片麻岩变长岩，地球化学分类为低钾拉斑花岗岩类。岩石学研究表明，拉斑岩浆来源于地壳深处的低钾玄武岩熔融，最可能的构造背景是幼年洋弧。另外2块岩石分散成小侵入体，地球化学上认为是与大洋板块熔融有关的钙碱性埃达克岩。拉斑变质岩的U-Pb SHRIMP锆石年龄集中在998 ~ 995 Ma，而钙碱性埃达岩的锆石年龄较年轻，分为945 ~ 920 Ma和772 Ma。因此，晚元古代侵入岩首先形成为幼弧成分，其次是洋板熔融的埃达克质岩浆作用。

This is a detailed study of Late Proterozoic intrusion in the Sor Rondane Mountains, Antarctica. The intrusion is classified into three lithologies: strong gneissose metatonalite, weak gneissose metatonalite and metagabbro. The strong gneissose metatonalite is the main lithotype, which is geochemically categorized as low-K tholeiitic granitoid. Petrological studies suggest that the tholeiitic magma was derived from low-K basalt melting at the crustal depth, and the most plausible tectonic setting is a juvenile oceanic arc. The other two rocks are scattered as small intrusions and are geochemically regarded as calc-alkaline adakites related to oceanic slab melting. U-Pb SHRIMP zircon ages of the tholeiitic metatonalite are concentrated at 998-995 Ma, whereas the calc-alkaline adakites are younger and divided between ages 945-920 Ma and 772 Ma. Therefore, the Late Proterozoic intrusion was formed first as a juvenile arc component, followed by adakitic magmatism with oceanic slab melting.