东昆仑南缘布青山构造混杂岩带哥日卓托闪长岩体年代学、地球化学特征及其地质意义  

Geochronology and Geochemistry of the Gerizhuotuo Diorites from the Buqingshan Tectonic Mélange Belt in the Southern Margin of East Kunlun and Their Geologic Implications

作　　者：李佐臣[1] 裴先治[1] 刘战庆[2] 李瑞保[1] 裴磊[3] 陈国超[1] 刘成军[1] 陈有炘[1] 高景民[1] 魏方辉[1] 吴树宽[1] 王银川[1] 杨杰[1] 

机构地区：[1]西部矿产资源与地质工程教育部重点实验室,长安大学地球科学与资源学院,西安710054 [2]桂林理工大学地球科学学院,广西桂林541004 [3]中国地质大学(北京)地球科学与资源学院,北京100083

出　　处：《地质学报》2013年第8期1089-1103,共15页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号41172186;40972136;40572121);高等学校博士学科点专项科研基金项目(编号20110205110004);中央高校基本科研业务费专项资金项目(编号CHD2011TD020;CHD2009JC046;2013G1271092);青海省国土资源厅-中国铝业公司公益性区域地质矿产调查基金项目(中铝基金200801)联合资助的成果

摘　　要：对东昆仑南缘布青山构造混杂岩带哥日卓托闪长岩体进行了锆石U-Pb年代学和岩石地球化学研究,以便对其形成时代和岩石成因进行约束。结果表明,哥日卓托闪长岩锆石Th/U比值(0.63～1.28)较高,阴极发光图像显示锆石内部发育振荡环带,具岩浆成因特点;LA-ICP-MS锆石U-Pb年龄为225.8±1.5Ma(MSWD=0.53),表明其形成时代为晚三叠世早期。岩体的SiO2含量在53.07%～58.74%之间,Al2O3(14.66%～16.17%)含量相对较高,全碱含量较低(4.76%～6.04%),高钾(1.60%～2.90%),里特曼指数σ在1.69～2.66之间,属高钾钙碱性系列。稀土元素总量(∑REE)为158.36×10-6～211.50×10-6,δEu为0.85～0.97,稀土元素配分曲线呈右倾型,具有弱的负铕异常。高场强元素(Nb、Ta、P等)和大离子亲石元素(Ba、Sr、Ti等)具有明显的负异常,而Rb、U、La、Hf、Nd等元素具有明显的正异常。哥日卓托闪长岩形成于高温环境(800℃±),具有后碰撞岩浆活动的特征,是东昆仑地块与巴颜喀拉地块碰撞后地壳部分熔融的产物。This paper studies the Gerizhuotuo diorite of Buqingshan tectonic mélange belt in the southern margin of East Kunlun using zircon U-Pb geochronology and geochemical methods so as to constrain its formation and origin.The results shows that the zircons have high ratios of Th/U （0.63-1.28） and internal oscillatory zoning on CL imagines of the Gerizhuotuo diorites,suggesting a magmatic origin.LA-ICP-MS zircon geochronological age of 225.8±1.5Ma （MSWD=0.53） implies the diorite formed at the early period of Late Triassic.Geochemically,the rock is characterized by medium contents of SiO2（53.07%-58.74%）,and relatively high Al2O3 （14.66%～16.17%）,low alkaline （4.76%～6.04%）,high K2O（1.60%～2.90%）and Rittmann index σ from 1.69 to 2.66,suggesting that the diorite belongs to the high-K calc-alkaline series.The average value of ΣREE is 158.36×10-6 ～211.50×10-6,with δEu= 0.85～0.97.The chondrite normalized REE pattern curve shows right-sloping type,with weak negative Eu anomalies.The primitive mantle standardized trace elements diagram show that HFSE（Nb,Ta,P,etc.） and LILE（Ba、Sr,Ti,etc.） has remarkable negative anomalies,while Rb,U,La,Hf,Nd,etc.） has remarkable positive anomalies.Our study indicates that the Gerizhuotuo diorite formed in the high temperature environment （800 ℃ ±）,and its post-collisional magmatism characteristic suggests the diorite was the product of crustal partial melting after the collision of the East Kunlun block and Bayan Har block.

关 键 词：闪长岩 LA-ICP-MS定年 地球化学 构造环境 布青山构造混杂岩带 

分 类 号：P588.122[天文地球—岩石学]