斯里兰卡地质演化研究的进展与评述:岩石组合、变质演化及其与冈瓦纳大陆的关系  

A review and appraisal on the study progress of the geological evolution of Sri Lanka:Rock associations,metamorphism and their relations with Gondwana

作　　者：赵磊[1] 张艳斌[1] MALAVIARACHCHI Sanjeewa Prabhath Kumara DHARMAPRIYA Prasanna Lakshitha 翟明国[1] ZHAO Lei;ZHANG YanBin;MALAVIARACHCHI Sanjeewa Prabhath Kumara;DHARMAPRIYA Prasanna Lakshitha;ZHAI MingGuo(State Key Laboratory of Lithospheric Evolution,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;Department of Geology,Faculty of Science,University of Peradeniya,Kandy 20400,Sri Lanka)

机构地区：[1]中国科学院地质与地球物理研究所岩石圈演化国家重点实验室,北京100029 [2]斯里兰卡佩拉德尼亚大学地质系,康堤20400

出　　处：《岩石学报》2021年第5期1287-1320,共34页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(41872197、41890832、41890834);中国-斯里兰卡水技术研究与示范联合中心项目;中国科学院中国-斯里兰卡联合科教中心联合资助

摘　　要：地球表生环境的演变及生命演化过程,与地球构造过程密切相关,新元古代-寒武纪时期的冈瓦纳大陆汇聚过程见证了一系列剧变。东非造山带(ca.650~620Ma)和Kuunga造山带(ca.600~500Ma)是冈瓦纳大陆块体汇聚过程中形成的两条主要造山带,二者在斯里兰卡所在的区域十字交叉。因此斯里兰卡地质演化历史的准确梳理,对理解新元古代时期全球构造过程的重要意义不言而喻。斯里兰卡的四个前寒武纪地质体(Wanni、Kadugannawa、Highland和Vijayan杂岩地体)中,中部的Highland杂岩地体最古老(ca.2000~1800Ma)、变质程度最高(普遍麻粒岩相,局部为超高温麻粒岩相),其余三个地质体主要岩石的形成时代为中元古代晚期-新元古代(ca.1100~700Ma),岩石记录的变质级别略低于Highland地体,为角闪岩相-麻粒岩相。现有研究表明斯里兰卡几个地质体在新元古代-寒武纪时期(ca.610~500Ma)的变质作用记录最为显著,并伴随有广泛的陆壳重熔再造。该构造热事件晚于东非造山带的变质时代(ca.650~620Ma),与Kuunga造山带活动时间(ca.600~500Ma)吻合度较高,这与前人提出的莫桑比克缝合带(东非造山带)穿过斯里兰卡的认识相矛盾。斯里兰卡的高级变质作用究竟是单次造山作用的结果,还是代表了两期造山事件的叠加效应,目前尚无定论。高温-超高温变质作用是斯里兰卡前寒武纪基底岩系的显著特征,其中超高温麻粒岩具有假蓝宝石+石英、紫苏辉石(Al2O3含量可达~13%)+夕线石、尖晶石+石英等的矿物组合,不同研究者给出超高温峰期变质温度在950~1150℃的范围内,峰期变质压力在10~16kbar的范围内,多显示顺时针演化P-T轨迹。斯里兰卡中东部地区的基性麻粒岩,发育由斜方辉石+斜长石、角闪石+斜长石或单斜辉石+斜长石组成的环绕石榴石的蠕虫状后成合晶结构,指示近等温降压的P-T演化样式,以及峰期变质作用之后地体相�Changes in our Earth’s environment and biota are usually closely associated with tectonic processes.The assembly of the supercontinent Gondwana during Neoproterozoic-Cambrian is synchronous with some of these critical changes.The East African Orogen(ca.650~620 Ma)and the Kuunga Orogen(ca.600~500 Ma)are two major orogenic events that welded major parts of Gondwana and they cross each other in Sri Lanka.A thorough understanding of the evolutionary history of Sri Lanka is,therefore,of great importance for the reconstruction of Supercontinent Gondwana and the proper interpretation of the tectonic processes involved.The Precambrian crystalline basement of Sri Lanka has been divided into four parts according to metamorphic grade and isotopic features of constituent rock assemblages,which are the Wanni,Kadugannawa,Highland and Vijayan complexes.The Highland Complex situating in the middle part of Sri Lanka hosts the oldest rocks(ca.2000~1800 Ma)of Sri Lanka and its basement rocks often display granulite facies metamorphism.Rocks of the other three terranes in Sri Lanka are relatively younger(ca.1100~700 Ma)and their metamorphic grade is also relatively lower than that of the Highland Complex,at amphibolite-granulite facies.High-grade metamorphism of these terranes occurred during Neoproterozoic-Cambrian(ca.610~500 Ma)is a prominent feature which was accompanied by pervasive anatexis.This tectonothermal event in Sri Lanka is relatively younger than those developed in East African Orogen(ca.650~620 Ma)and largely synchronous with the Kuunga Orogen(ca.600~500 Ma),which is inconsistent with the previously proposed interpretation that the Mozambique Suture(East African Orogen)passes through Sri Lanka.Besides,it is still unclear whether the high-grade metamorphism in Sri Lanka is the result of one orogenic event or that of multiple orogenic events.High-to ultrahigh-temperature metamorphism is a typical feature of basement rocks in the Highland Complex of Sri Lanka.Ultrahigh temperature(UHT)granulites contain diagnostic mine

关 键 词：斯里兰卡 前寒武纪地体 UHT变质作用 变质年代学 冈瓦纳大陆 

分 类 号：P588.3[天文地球—岩石学] P542[天文地球—地质学]