巴西卡拉加斯地区基底杂岩的地质特征与时代约束  

Geological features and age constraint of basement complex in Carajás province of Brazil

作　　者：曾勇[1,2] 郭维民 姚春彦 陈丹丹 刘君安 ZENG Yong;GUO Weimin;YAO Chunyan;CHEN Dandan;LIU Jun an(China University of Geosciences,Wuhan 430074, Hubei, China;Nanjing Center of China Geological Survey, Nanjing 210016, Jiangsu, China)

机构地区：[1]中国地质大学,湖北武汉430074 [2]南京地质调查中心,江苏南京210016

出　　处：《中国地质》2017年第4期766-780,共15页Geology in China

基　　金：中国地质调查局地质矿产调查评价项目(1212011220909);中央地质勘查基金境外风险勘查项目(201130D6200119)联合资助~~

摘　　要：巴西卡拉加斯(Carajás)地区出露世界上重要且古老的太古宙变质基底,是世界上矿床类型最为丰富、资源聚集程度最高的成矿区之一,它的基底兴谷(Xingú)杂岩是南美克拉通古老的太古宙花岗岩-绿岩地体。在调查该地区基底杂岩地质特征的基础上,对侵入其中的变质深成岩体进行了年代学研究,提出了基底杂岩的组成、结构与构造的认识,认为兴谷杂岩是以麻粒岩相-角闪岩相片麻岩和混合岩为主体的古老变质岩,将其中的紫苏花岗岩和英云闪长质-奥长花岗质片麻岩从中剥离出来,进一步分解出不同时期的变质侵入体;本次在其中的片麻状花岗岩中获得了(2899±45)Ma、(2742±9.5)Ma和(2831±19)Ma的锆石LA-ICP-MS年龄,进一步确认兴谷杂岩的时代为中太古代,时代约束在3.05~2.85 Ga,其中包含3.05~2.96 Ga和2.96~2.85 Ga的两个构造时段的表壳岩和TTG片麻岩套。The world’s most important and older Archaeozoic metamorphic basement is exposed in Carajas province of Brazil,it is known as one of the metallogenic provinces that have most abundant ore deposit types and highest extent of resource aggregation.Its basement of Xingu complex is the Southern American Craton’s older Archaean greenstone-gtanite body.Based on the investigation of geological features of the basement complex,the authors studied the chronology of metamorphic pluton that intruded into the metamorphic basement and put forward the understanding concerning composition,structure and tectonics of the basement complex.It is thought to be the ancient metamorphic basement with granulite-amphibolite facies gneisses and complex as the main body.The authors peeled off the charnockite and tonalite-trondhjemite granitic gneiss and further decomposed the metamorphic intrusions in different periods.The LA-ICP-MS ages of zircons in(2899±45)Ma,(2742±9.5)Ma and(2831±19)Ma were acquired in gneissic granite,and this further confirms the fact that the age of Xingu complex is Mesoarchean within3.05-2.85Ga,and the Xingu complex also includes two tectonic periods of supracrustal rock and gneiss suite with age of3.05-2.96Ga and2.96-2.85Ga.

关 键 词：变质岩 巴西 卡拉加斯 兴谷杂岩 年龄 

分 类 号：P587[天文地球—岩石学] P597.3[天文地球—地质学]