阿尔泰山南缘二叠纪地壳伸展减薄——来自侵入岩的证据  

PERMIAN CRUSTAL EXTENSIONAL THINNING IN THE THE SOUTH MARGINE OF AITAY MOUNTIANS:EVIDNCE FROM INTRUSIVE ROCKS

作　　者：刘崴国[1] 韩静波[2] 薛晓峰[1] 郭伟伟[1] 

机构地区：[1]新疆地质矿产勘查开发局第一区域地质调查大队,新疆乌鲁木齐830011 [2]河北省地矿局秦皇岛矿产水文工程地质大队,河北秦皇岛066000

出　　处：《新疆地质》2011年第3期270-274,共5页Xinjiang Geology

基　　金：中国地质调查局国土资源地质大调查项目(1212010911055)资助

摘　　要：新疆阿尔泰山南缘乌夏沟发育苏长-正长岩体,受张性断裂控制,呈小岩株产出,侵入于泥盆纪花岗闪长岩及下元古界克木齐岩群中,岩石SiO2含量为46.91%～50.75%,苏长岩锆石SHRIMP U-Pb定年结果为(275.9±1)Ma,为二叠纪弛张期产物.在中蒙边境塔克什肯口岸发育富碱侵入岩及少量辉绿辉长岩,主要岩石类型有正长岩、石英二长岩、石英碱长二长岩等,岩石富碱(K2O+Na2O=9.62%～11.7%)、贫铁(TFe=1.73%～4.1%),稀土元素总量较高,∑REE=233.86×10-6～525.38×10-6,显示轻稀土富集、重稀土亏损特点,铕负异常或正异常,亏损大离子亲石元素Sr,Ba,富集高场强元素Nd,Ta.锆石U-Pb定年为206Pb/238U年龄(286±1)Ma,在Rb/Nb-Y/Nb图解上落入A2型范围,属后造山环境.上述基性及富碱侵入岩是该区二叠纪地壳伸展减薄记录.A series of norite-syenite occur on Wuxiagou the south margin of Aitay Mountians.They were in the control of normal fault,their occurrences were stock.These plutons were intruded into Devonian granodiorite and early Neoproterozoic Kemuqi Group.The contents of SiO2 rang from 46.91% to 50.75%.SHRIMP U-Pb Zircon dating of the norite yeild （275±1） Ma,they are proved that they formed in the Permian tensional structural enciroment.A series of alkali-rich intrusion occur on Chinese Aitay orogen.This pluton is composed of syenite with quartz monzonite,quartz alkali-feldspar syenite and syenogranite.The rocks are alkali-rich（K2O＋N2a=9.62%-11.71%） ,has lower Fe（TFe 1.73%-4.1%）.The total content of rare earth element（REE） are high（∑REE=223.86×10^-6-525.38×10^-6）. The rock is depleted in large-ionlithopheile elements ,such as Sr, Ba and enriched in high-field strength elements such as Nd, Ta.The Zircon U-Pb dating yield a ^206Pb /^238pb age of （286±1） Ma.The alkali-rich intrusive rocks setted in A2 type in the Rb/Nb-Y/Nb diagram,this pluton is post orogenic.The dyke and alkali-rich intrusive rocks were the record of crustal extensional thinning at Permian.

关 键 词：乌夏沟 二叠纪 富碱侵入岩 后造山环境 地壳伸展减薄 

分 类 号：P534.46[天文地球—古生物学与地层学]