东昆仑东段巴隆花岗质片麻岩年代学、地球化学特征及地质意义  

Geochronology,geochemical features and geological significance of the granitic gneiss in Balong area,East Section of East Kunlun

作　　者：陈有炘[1,2] 裴先治[1,2] 李佐臣[1,2] 李瑞保[1,2] 刘成军[1] 陈国超[1] 裴磊[3] 魏博[1] 

机构地区：[1]长安大学地球科学与资源学院,西安710054 [2]国土资源部岩浆作用与找矿重点实验室,西安710054 [3]中国地质大学地球科学与资源学院,北京100083

出　　处：《岩石学报》2015年第8期2230-2244,共15页Acta Petrologica Sinica

基　　金：国家自然科学基金项目(41472191;41172186;40972136;40572121);中国高等学校博士学科点专项科研基金项目(20110205110004);中央高校基本科研业务费专项资金项目(CHD2011TD020;2013G1271091;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

摘　　要：东昆仑东段巴隆南侧古元古界白沙河岩组中可识别出一套花岗质片麻岩。采用LA-MC-ICP-MS方法进行锆石UPb年代学分析,获得加权平均年龄为870.6±7.7Ma（MSWD=2.6）和875.3±6.3Ma（MSWD=0.92）,显示该岩体形成于新元古代早期,并经历了早古生代变质作用。地球化学特征显示,岩石具有高Si O2、Al2O3、K2O,低Ti O2、Na2O的特征,A/CNK平均为1.14,A/NK平均为1.47,矿物组合中出现石榴子石和白云母等富铝矿物,显示S型过铝质花岗岩特征;球粒陨石标准化配分曲线显示轻稀土元素富集（（La/Yb）N=6.22~25.37）,有明显的铕负异常（δEu=0.16~0.44）。原始地幔标准化蛛网图显示,岩石富集Rb、Th,明显亏损Ba、Ta、Nb、Sr、P和Ti元素。综合分析,岩浆来源于陆壳部分熔融,可能为古元古界白沙河岩组长英质岩石发生脱水熔融的产物,形成于同碰撞环境,是东昆仑地区响应Rodinia超大陆汇聚事件的物质记录。A suite of granitic gneisses have been identified within the Paleoproterozoic Baishahe Formation to the south of Balong,East Kunlun orogenic belt. LA-MC-ICP-MS zircon U-Pb dating of the granitic gneisses yielded magmatic crystallization ages of 870. 6 ±7. 7Ma and 875. 3 ± 6. 3Ma. The granitic gneisses experienced metamorphism in the Early Paleozoic. They are characterized by high Si O2,Al2O3,and K2 O,and low Ti O2 and Na2O contents. The peraluminious character（ ave. A / CNK = 1. 14,ave. A / NK = 1. 47）and the occurrence of rock-forming minerals such as garnet and muscovite suggest that the granites are of S-type. The chondritenormalized REE patterns of the samples show enrichment of LREE（（ La / Yb）N= 6. 22 ~ 25. 37） and strong negative Eu anomalies（ δEu = 0. 16 ~ 0. 44）. The primitive mantle-normalized trace element diagrams show enrichment of Rb and Th,and depletion of Ba,Ta,Nb,Sr,P and Ti. The geochemistry of the granitic gneisses resembles that of typical crust-derived syn-collisional granites. It is suggested that the granitic gneisses resulted from dehydration melting of the Paleoproterozoic Baishahe Formation,recording a collision between micro blocks in East Kunlun in Early Neoproterozoic period in response to the assembly of Rodinia.

关 键 词：东昆仑东段 花岗质片麻岩 新元古代 同碰撞花岗岩 RODINIA 

分 类 号：P588.345[天文地球—岩石学] P597.3[天文地球—地质学]