藏东地区中奥陶世浪拉山糜棱岩化二长花岗岩LA-ICP-MS锆石U-Pb年代学及地质意义  

GEOLOGICAL SIGNIFICANCE AND LA-ICP-MS ZIRCON U-Pb CHRONOLOGY OF THE MIDDLE ORDOVICIAN LANGLASHAN MYLONITIZED MONZONITIC GRANITE IN EASTERN TIBET

作　　者：胡志宇[1] 王新然 樊炳良 白涛[4] Hu Zhiyu;Wang Xinran;Fan Bingliang;Bai Tao(Key Laboratory of Geological Hazards on Three Gorges Reservoir Area,China Three Gorges University,Ministry of Education,Yichang 443002,China;Bureau of Geology and Mineral Exploration and Development,Zhengzhou 451464,China;Geothermal Geological Survey Party,Tibet Bureau of Geology and Mineral Exploration and Development,Lhasa 850000,China;College of Earth Sciences,Chengdu University of Technology,Chengdu 610059,China)

机构地区：[1]三峡库区地质灾害教育部重点实验室,三峡大学,湖北宜昌443002 [2]河南省地质矿产勘查开发局第三地质勘查院,河南郑州451464 [3]西藏自治区地质矿产勘查开发局地热地质大队,西藏拉萨850000 [4]成都理工大学地球科学学院,四川成都610059

出　　处：《矿物岩石》2019年第3期60-68,共9页Mineralogy and Petrology

摘　　要：对藏东地区浪拉山糜棱岩化二长花岗岩进行了LA-ICP-MS锆石U-Pb年龄测试,获得了该岩体的206Pb/238 U年龄加权平均值为470.5 Ma±3.7 Ma(MSWD=1.7,n=15),属于中奥陶世的产物。岩石地球化学特征表明,岩石具有高钾(Na2O/K2O=13.12~162.89)、铝(A/CNK值平均为1.30)、低钛的特征,岩石属于高钾钙碱性过铝质S型花岗岩。岩石具有明显Eu负异常,表现为Nb,Sr,P、Ti等高场强元素相对亏损,相对富集K,Rb,Th,U等大离子亲石元素,具有岛弧型花岗岩的特征。结合区域地质资料分析,该岩体与区内原特提斯洋的俯冲存在成因联系,藏东地区浪拉山糜棱岩化二长花岗岩的发现有助于进一步探索原特提斯洋演化过程。LA-ICP-MS zircon U-Pb dating on the Langlashan mylonitized monzonitic granite in eastern Tibet yields a weighted average age of 470.5Ma±3.7Ma(MSWD=1.7,n=15),aproduct of middle Ordovician.Geochemical analysis shows that the rock is characterized by high potassium (Na2O/K2O=13.12~162.89),aluminum(average A/CNK 1.30)and low titanium,belonging to high potassium calcium alkaline over-aluminum S-type granite.The rock has obvious Eu negative anormaly,with relative loss of high field strength elements,such as Nb,Sr,P and Ti,and relatively rich in large ionic pro-stone elements,such as K,Rb,Th and U,characteristic of island arc granite.Based on the geochemical and chronological studies,combined with the analysis of regional geological data,it is considered that the Langlashan mylonitized monzonitic granite is related to the subduction of Proto-Tethys Ocean.Therefore,the discovery of the Langlashan mylonitized monzonitic granite provides evidence for the discussion of Proto-Tethys Ocean evolution.

关 键 词：浪拉山糜棱岩化二长花岗岩 岩石地球化学特征 锆石U-PB LA-ICP-MS 岩石成因 

分 类 号：P588.1[天文地球—岩石学] P597[天文地球—地质学]