冈底斯南缘唐加地区早侏罗世辉长岩成因及其构造意义  

ORIGIN AND TECTONIC SIGNIFICANCE OF EARLY JURASSIC GABBRO IN TANGJIA AREA OF SOUTHERN GANGDESE MARGIN,TIBET

作　　者：童霞 杨文光[1] 朱利东[1] 麦源君 解龙[1] 钟摇 李楠 周豫 Tong Xia;Yang Wenguang;Zhu Lidong;Mai Yuanjun;Xie Long;Zhong Yao;Li Nan;Zhou Yu(Institute of Sedimentary Geology,Chengdu University of Technology,Chengdu,Sichuan 610059,China)

机构地区：[1]成都理工大学沉积地质研究院,四川成都610059

出　　处：《矿物岩石》2021年第2期71-82,共12页Mineralogy and Petrology

基　　金：国家自然科学基金项目(41972118);冈底斯-喜马拉雅铜矿资源基地调查项目(DD20160015)。

摘　　要：冈底斯南缘发育的早侏罗世岩浆岩对于讨论新特提斯洋早期的俯冲消减演化具有重要约束意义。在详尽地野外地质调查工作基础上,本次研究对唐加地区辉长岩进行了LA-ICP-MS锆石U-Pb年龄、全岩地球化学组成的研究。结果表明,唐加辉长岩形成于早侏罗世(183.9±0.9 Ma);样品w(SiO2)(46.77%~48.48%)较低,较高的w(MgO)含量(平均为7.71%),Mg#为42.0~67.6。此外,轻稀土元素富集[(La/Yb)N=4.33~12.02],具有略右倾的配分模式和弱的Eu异常(δEu=0.69~0.79);富集大离子亲石元素,亏损高场强元素(Nb, Ta, Zr, Hf, Ti)。综合区域数据全面分析,认为唐加早侏罗世辉长岩可能为新特提斯洋北向俯冲消减的背景下典型的岛弧岩石,是俯冲流体交代地幔楔部分熔融的产物。On the basis of detailed field geological survey, the chronology and whole rock geochemical composition of gabbro in the Tangjia area are studied in order to discuss the important constraint significance of the Early Jurassic magmatic rocks developed in the southern margin of Gangdese on the early subduction and subduction evolution of the Neo-Tethys Ocean. The results show that the LA-ICP-MS zircon U-Pb age dating for the Tangjia gabbro yields an age of Early Jurassic(183.9±0.9 Ma). Geochemical analysis of the gabbro shows that the w(SiO2) content is low(46.77%-48.48%), the MgO content is high(7.71% on average), and the Mg# content is 42.0-67.6. In addition, light rare earth elements are enriched((La/Yb)N=4.33-12.02) with a slightly right-leaning distribution pattern and weak Eu anomaly(δEu=0.69~0.79). The rocks are enriched in large ion lithophile elements and depleted in high field strength elements Nb, Ta, Zr, Hf and Ti. Based on the comprehensive analysis of regional data, it is concluded that the Early Jurassic gabbro in Tangjia area may be a typical island arc rock under the background of northward subduction and subduction of the Neo-Tethys Ocean, and it is the product of partial melting of mantle wedge hybridized by subduction fluid.

关 键 词：辉长岩 早侏罗世 岛弧岩浆岩 冈底斯 西藏 

分 类 号：P581[天文地球—岩石学] P588.144[天文地球—地质学]