新疆玛因鄂博断裂带中花岗质糜棱岩锆石U-Pb SHRIMP和黑云母^(40)Ar-^(39)Ar年龄及意义  

Zircon U-Pb SHRIMP and ^(40)Ar-^(39)Ar Dating of the Granitic Mylonite in the Mayinebo Fault Belt of North Xinjiang and Its Geological Significance

作　　者：周刚[1,2] 张招崇[3] 王新昆[3] 王祥 罗世宾 何斌 张小林 

机构地区：[1]中国地质科学院研究生部 [2]新疆地质矿产局第四地质大队,阿勒泰市836500 [3]中国地质大学地质与矿产资源重点实验室

出　　处：《地质学报》2007年第3期359-369,共11页Acta Geologica Sinica

基　　金：新疆维吾尔自治区1:5万区调项目(编号XJQDW2003-03);国家305项目(编号2001BA609A-07-02)资助的成果。

摘　　要：玛因鄂博断裂带具有左型剪切活动特征,分布其中的花岗质糜棱岩呈脉状、条带状产出,展布方向与剪切拉伸方向一致,为同构造花岗岩。其岩石化学为高钾钙碱性系列,属后碰撞“I”型花岗岩;稀土元素含量较高,ΣREE为(239.14~266.31)×10-6;具有中等程度的铕负异常,δEu为0.45~0.66,轻稀土明显富集。其锆石U-PbSHRIMP年龄为281±4Ma,黑云母40Ar-39Ar等时线年龄为236.1±1.2Ma。二者分别代表岩石的侵入年龄和后期的剪切变形年龄。其形成与早二叠世区域性大规模剪切活动有关,而黑云母40Ar-39Ar等时线年龄代表中三叠世早期的剪切变形活动。结合前人资料分析,玛因鄂博断裂的剪切活动持续时间较长,高峰期可能为290~270Ma,而其最后结束时间为230Ma左右。The granitic mylonite occurred at the left-later shear Mayinebo fault belt as veined and banded shapes, which is consistent with shear-extension direction, belonging to syn-tectonic granite. It belongs to high-K calcalkaline series, and can be classified as ＂I＂-type granite. Their total REE contents are high, from 239.14〉〈 10.6 to 266. 31 × 10^- 6 with mediate negative Eu anomalies of 0.45 to 0. 66. They are also charactered by enrichment of LREE. The zircon U-Pb SHRIMP dating yields an age of 281±4Ma, and ^40Ar-^33Ar isochron age is 236.1±1.2Ma. These two ages may represent those of the magma emplacement and thereafter shear- deformation. The emplcaement might result from local shear event during middle Triassic. In contrast, the ^40Ar-^39Ar age of biotite represent the local shear-deformation event during middle Triassic. In combination with previous work, it can inferred that the shear event might last a long time with peak age of 290 to 270 Ma,-and ended at 230 Ma.

关 键 词：花岗质糜棱岩 锆石U-PB SHRIMP年龄 黑云母^40Ar-^39Ar年龄 玛因鄂博断裂 

分 类 号：P597[天文地球—地球化学]