西藏中拉萨地块门巴花岗闪长岩成因及深部动力学过程  

Petrogenesis and Geodynamic Processes of the Mamba Granodiorite,Central

作　　者：王旭辉[1] 郎兴海[1] 梁海辉 杜良艺 邓煜霖 何青 董咪 Wang Xuhui;Lang Xinghai;Liang Haihui;Du Liangyi;Deng Yulin;He Qing;Dong Mi(College of Earth Science,Chengdu University of Technology,Chengdu 610059,China;East China Metallurgical Geologlcal Prospecting Bureau of Geophysiical Prospecting Team,Wuhu 241000,China)

机构地区：[1]成都理工大学地球科学学院,四川成都610059 [2]华东冶金地质勘查物探队,安徽芜湖241000

出　　处：《地球科学》2024年第2期577-593,共17页Earth Science

基　　金：四川省科技计划项目(No.2020JDJQ0042);国家自然科学基金项目(No.41972084);成都理工大学珠峰科学研究计划(2020ZF11407);西北大学大陆动力学国家重点实验室开放基金(No.18LCD04);自然资源部深地资源成矿作用与矿产预测重点实验室开放基金(No.ZS1911);中国地质调查局项目(Nos.DD20190167,DD20160346)。

摘　　要：为了探讨拉萨地块晚白垩世岩浆作用的深部动力学机制,对中拉萨地块南缘门巴花岗闪长岩开展了岩相学、年代学、岩石地球化学及矿物化学研究.LA-ICP-MS锆石U-Pb定年表明门巴花岗闪长岩侵位于晚白垩世(83.2 Ma±0.9 Ma).岩石地球化学特征显示门巴花岗闪长岩为埃达克质岩石,电子探针数据揭示斜长石属于中-奥长石(An:16.2~34.7).综合分析本文认为门巴花岗闪长岩的母岩浆为幔源镁铁质岩浆底侵诱发加厚下地壳熔融并与之发生混合作用的结果.结合晚白垩世岩浆岩成岩环境及时空分布特征,认为拉萨地块南部晚白垩世岩浆作用主要受新特提斯洋脊俯冲控制,软流圈地幔沿洋中脊裂隙板片窗上涌诱引了南拉萨地块南缘晚白垩世大规模岩浆作用,而软流圈物质沿切割洋中脊的转换断层撕裂板片窗上涌诱发了近似垂直前者分布的小规模板内岩浆作用.In order to discuss thedynamic mechanism of Late Cretaceous magmatism in the Lhasa block,this paper carried out petrographic,chronological,geochemical and mineral chemistry studies on the Menba granodiorites in the southern margin of the central Lhasa block.LA-ICP-MS zircon U-Pb dating indicates that the Menba granodiorites emplaced in the Late Cretaceous(83.2 Ma±0.9 Ma).The geochemical characteristics show that the Menba granodiorites are adakitic rocks.Electron microprobe data reveal that plagioclase belongs to andesine and oligoclase(An=16.2-34.7).This paper believes that the parent magmas of the Menba granodiorites may be a result of magma mixing between mantle-and crust-derived magmas and the mantle-derived magma underplating may have led to partial melting of the thickened lower crust and then reactions between them.Combined with the diagenetic environment and spatial distribution characteristics of the Late Cretaceous magmatic rocks.This paper concludes that the Late Cretaceous magmatism in the southern Lhasa block was mainly controlled by the ridge subduction of the Neo-Tethys.The upwelling of asthenosphere mantle along the slab window of the mid-ocean ridge induced the Late Cretaceous large-scale magmatism in the southern margin of the south Lhasa block,while the upwelling of asthenosphere material along the tear slab window of transition fault that cuts the mid-ocean ridge induced the small-scale intraplate magmatic belt,which approximately perpendicular to the large-scale magmatism in the southern margin of the south Lhasa block.

关 键 词：拉萨地块 晚白垩世 埃达克质岩石 岩浆混合 洋脊俯冲 板片窗 岩石学 

分 类 号：P581[天文地球—岩石学]