高校地质学报2018，Vol.24Issue(1)：41-55,15.DOI:10.16108/j.issn1006-7493.2017087
西藏冈底斯南缘汤白斑状花岗岩锆石U-Pb年代学、地球化学及地质意义
Zircon U-Pb Geochronology,Geochemistry and Tectonic Implications of the Tangbai Porphyritic Granite Pluton in Southern Margin of Gangdese,Tibet
摘要
Abstract
In order to discuss the genesis of Late Triassic to Early Jurassic magmatic rocks and its relationship with the early-stage evolution of the Neo-Tethys in the southern margin of the Gangdese, we report petrography, geochronology and geochemistry of the porphyritic granites from Tangbai in southern margin of Gangdese, Tibet. Zircon U-Pb dating yields an age of(190.37 ± 0.87) Ma (MSWD=0.58) for the porphyritic granites, indicating that they were formed in Early Jurassic. Geochemically, the rocks are characterized by high contents of SiO2(75.20%~75.97%),Na2O(3.39%~4.12%)and ratios of Na2O/K2O(1.40~2.00)and low contents of MgO(0.32%~0.38%), thus can be grouped into calc-alkaline I-type granites. The trace elements are characterized by enrichment of LILEs(such as Rb,U and K)and LREEs and depletion of HFSEs(such as Nb,Ta and Ti)and HREEs,indicating that they were formed in magmatic arc setting related to the northward subduction of the Neo-Tethys oceanic slab. Furthermore, the granites have low Mg#values(26.71~41.34,Mean=35.26),and with Nb/Ta ratios similar to the lower crust,indicating that the granites were mainly generated from partial melting of the lower crust. Combined with previous research results, it is shown that the Late Triassic to Early Jurassic magmatic rocks in the southern Gangdese were formed in magmatic arc related to the northward subduction of the Neo-Tethys oceanic slab,and the initial age of northward subduction of the Neo-Tethys oceanic crust should prior to the crystallization age(190.37±0.87 Ma) of the porphyritic granites reported in this paper.关键词
冈底斯/花岗岩/晚三叠世—早侏罗世/构造背景/新特提斯洋Key words
gangdese/granite/Late Triassic to Early Jurassic/tectonic setting/Neo-Tethys分类
天文与地球科学引用本文复制引用
王旭辉,郎兴海,邓煜霖,崔志伟,娄渝明,韩鹏..西藏冈底斯南缘汤白斑状花岗岩锆石U-Pb年代学、地球化学及地质意义[J].高校地质学报,2018,24(1):41-55,15.基金项目
国家自然科学基金项目(41502079) （41502079）
国土资源部公益性行业专项(201511022-02) （201511022-02）
内生金属矿床成矿机制研究国家重点实验室开放研究基金项目(2017-LAMD-K04) （2017-LAMD-K04）
四川省青年基金项目(2014JQ0047) （2014JQ0047）
四川省教育厅自然科学重点项目(15ZA0073)联合资助 （15ZA0073）
