西准噶尔早二叠世岩浆活动:卡拉岗组流纹岩年代学、地球化学特征及岩石成因  

Early Permian Mesozoic Magmatism in Western Junggar:Chronology,Geochemistry and Petrogenesis of the Kalagang Formation Rhyolite

作　　者：贾健 舍建忠 邸晓辰 王庆军 刘阁 Jia Jian;She Jianzhong;Di Xiaochen;Wang Qingjun;Liu Ge(Xinjiang institute of geological survey,Urumqi,Xinjiang,830000,China)

机构地区：[1]新疆维吾尔自治区地质调查院,新疆乌鲁木齐830000

出　　处：《新疆地质》2018年第1期15-22,共8页Xinjiang Geology

基　　金：新疆谢米斯台山中段阿克尔布拉克一带1:5万L45E008009;L45E009009;L45E009010三幅区域地质矿产调查

摘　　要：西准噶尔谢米斯台山中段出露大面积卡拉岗组流纹岩,准噶尔乃至整个北疆广泛发育晚古生代后碰撞花岗岩类。卡拉岗组为此类岩体喷发相的代表,岩石类型主要为流纹岩,是认识西准噶尔谢米斯台花岗岩岩石成因及构造-岩浆演化的关键。该地层流纹岩中测得LA-ICP-MS锆石年龄为(296±12)Ma(n=7,MSWD=4.9),为早二叠世。岩石地球化学研究表明,流纹岩具有高硅(SiO_2=76.49%~80.10%)、低钛(TiO_2=0.10%~0.19%)、高铝(Al2O3=10.38%~12.42%)、富碱(K_2O+Na_2O=6.91%~9.00%)、富钾(K_2O/Na_2O=1.75~11.00,平均3.33)、贫钙(0.13%~0.26%)的特征,铝饱和指数A/CNK=1.33~1.52,属过铝质系列。岩石富集大离子亲石元素Rb,Th,U,高场强元素Zr和Hf,亏损Ba,Sr,Eu,Nb,稀土元素分布曲线呈右倾"V"字型,属典型的铝质A型花岗岩。据微量元素比值及相关判别图,卡拉岗组流纹岩在成因类型上属于A2型,形成于后碰撞的张性环境中,软流圈上涌使年轻的地幔来源物质组成的下地壳发生部分熔融。Klagang formation rhyolite in large areas are exposed in Xiemisitai mountain,West Junggar,extensive developed the Late Paleozoic post collisional granites in Junggar and the northern Xinjiang.Kalagang formation as a kind of rock eruption phase,the rock types are mainly rhyolite,which is the key to understanding the petrogenesis and tectonicmagmatic evolution of granite in Xiemisitai,Western Junggar.The results of zircon LA-ICP-MS U-Pb dating is(296±12)Ma(n=7,MSWD=4.9),belongs to the Early Permian.Petrogeochemical analyses suggest that the rhyolite is characterized by high silica(SiO2=76.49%~80.10%),alkali(K2O+Na2O=6.91%~9.00%),and low titanium and calcium(TiO2=0.10%~0.19%,CaO=0.13%~0.26%).They belong to peraluminous(A/CNK=1.33~1.52).Trace element and REE research indicated that the Klagang group rhyolite have enrich in LILE such as Rb,Th,U,deplete in Ba,Sr,Eu,Nb,chondrite-normalized REE pattern is right-incline“V”type.This belonged to aluminum A-type granite.Based on trace element ratios and related discrimination diagrams,the Klagang group rhyolite can be A2 type granites,which are usually believed to have been formed in an post-collisional tectonic setting.Under the extensional setting,the upwelling asthenosphere triggered the partial melting of the lower crust composed of juvenile mantle origin substance.

关 键 词：西准噶尔 卡拉岗组 岩石地球化学 锆石LA-ICP-MS 

分 类 号：P588.14[天文地球—岩石学] P597[天文地球—地质学]