The felsic magmatic province in East Gondwana: implications for Pan-African tectonics

H.M. Rajesh , M. Santosh , M. Yoshida
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引用次数: 55

Abstract

The East Gondwana crustal fragments, namely southern India, Sri Lanka, Madagascar, East Antarctica and Western Australia, preserve evidence for a prominent Pan-African felsic magmatic event represented by feldspathoidal syenites, alkali granites and syenites emplaced proximal to fault lineaments. In Peninsular India, late or post-kinematic alkaline plutons ranging in age from 864 to 600 Ma characterize the Eastern Ghats belt, whereas a strong Pan-African imprint is provided by 550–750 Ma alkali granites and syenites in the southern granulite segment. In Sri Lanka, alkali granites occur in all major geologic units, with radiometric ages in the range of 550–760 Ma. In Madagascar, alkali granites and syenites with late Proterozoic to Palaeozoic ages are reported. Felsic magmatic activity in East Antarctica is characterized by post-tectonic granitic and syenitic plutons in Enderby Land and Queen Maud Land, showing an age range of 550–770 Ma. Pan-African felsic plutons in Western Australia define ages of 550–570 Ma. This paper summarizes the petrologic, geochemical and geochronologic characteristics of felsic plutons in the various East Gondwana fragments. Many of the intrusives represent anorogenic A-type magmas generated in rift-related environments of high heat flow and abundant volatile activity, correlative with an extensional tectonic regime and probably including melts generated from both upper mantle and lower crustal sources. This paper identifies a major Pan-African felsic magmatic province in East Gondwana, which, in association with their petrogenetic significance, is considered to be suggestive of a geodynamic signature of East Gondwana during the Pan-African period.

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东冈瓦纳的长英质岩浆省:对泛非构造的启示
东冈瓦纳地壳碎片,即印度南部、斯里兰卡、马达加斯加、东南极洲和西澳大利亚,保存了一个突出的泛非长英质岩浆事件的证据,其代表是长石正长岩、碱花岗岩和位于断层线近端的正长岩。在印度半岛,东高止带以864 ~ 600 Ma的晚期或运动后碱性岩体为特征,而南部麻粒岩段550 ~ 750 Ma的碱性花岗岩和正长岩则具有强烈的泛非印记。在斯里兰卡,碱花岗岩出现在所有主要地质单元中,辐射年龄在550-760 Ma之间。在马达加斯加发现了晚元古代至古生代的碱性花岗岩和正长岩。东南极洲长英质岩浆活动以Enderby Land和Queen Maud Land的构造后花岗质和正长岩体为特征,年龄范围为550-770 Ma。西澳大利亚泛非长英质岩体的年龄为550-570 Ma。本文综述了东冈瓦纳不同碎屑岩长英质岩体的岩石学、地球化学和年代学特征。许多侵入岩代表了在与裂谷相关的高热流和丰富的挥发性活动环境中产生的造山a型岩浆,与伸展构造制度相关,可能包括来自上地幔和下地壳的熔体。本文在东冈瓦纳确定了一个主要的泛非长英质岩浆省,结合其岩石成因意义,认为这暗示了东冈瓦纳在泛非时期的地球动力学特征。
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