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

本文对南极索尔龙托山脉晚元古代侵入体进行了详细的研究。岩体岩性可分为强片麻状变质岩、弱片麻状变质岩和变辉长岩三种。岩石类型以强片麻状变长岩为主，属低钾拉斑花岗岩类。岩石学研究表明，拉斑玄武岩岩浆来源于地壳深处的低钾玄武岩熔融，最合理的构造背景是一个年轻的洋弧。另外两个岩石是分散的小侵入体和地球化学被认为是钙碱性埃达克岩有关的大洋板片熔融。拉斑质变长岩的锆石U-Pb SHRIMP年龄集中在998 - 995Ma之间，钙碱性埃达克岩的年龄较年轻，分别在945 - 920Ma和772Ma之间。因此，晚元古代侵入体首先是作为幼年弧成分形成的，其次是埃达克质岩浆作用和大洋板片熔融。

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.