滇西维西-德钦一带花岗岩年代学、地球化学和岩石成因  

Geochronology,Geochemistry and Petrogenesis of Granites in Weixi-Deqin,West Yunnan

作　　者：高睿[1] 肖龙[2] 何琦[1] 袁静[1] 倪平泽[1] 杜景霞[1] 

机构地区：[1]中国地质大学研究生院,湖北武汉430074 [2]中国地质大学地球科学学院,湖北武汉430074

出　　处：《地球科学（中国地质大学学报）》2010年第2期186-200,共15页Earth Science-Journal of China University of Geosciences

基　　金：国家自然科学基金(Nos.40772043,40572031)

摘　　要：金沙江弧盆体系消减与碰撞的确切时间存在较大的争议.运用LA-ICP-MS地质年代学、地球化学及Sr-Nd同位素方法研究金沙江缝合带周边的花岗岩体.贡卡花岗闪长岩(232Ma)和羊拉花岗闪长岩(229.6Ma)形成于印支期,羊拉二长花岗岩(261Ma)形成于海西-印支期.羊拉二长花岗岩地球化学特征类似O型埃达克岩,由大洋板片熔融与地幔楔交代(Mg#=55～61.8>40),且上升过程与岩浆房酸性岩浆混合,形成于俯冲消减环境;贡卡花岗闪长岩和羊拉花岗闪长岩可能由类似扬子地块的崇山群玄武质岩石和变质表壳岩部分熔融形成,产于碰撞后环境.金沙江缝合带从中二叠世末期-晚二叠世早期持续俯冲;碰撞阶段可能于晚二叠世末期开始,在中三叠世早期结束.There is still much dispute over the exact subduction and collision time of Jinshajiang arc-basin system, which reveals geological evolution history of the paleo-Tethys in West China. This study provides chronological, petrological, and geochemical data of Gongka and Yangla granitoid plutons that are situated on the western margin of Jinshajiang suture zone but poorly studied in Deqin-Weixi area, Yunnan Province. The Yangla granitoid complex is divided into granodiorite and monzonite. LA- ICP-MS zircon dating results are 229.6 Ma （Yangla granodiorite）, 232 Ma （Gongka granodiorite） and 261 Ma （Yangla monzo- nite）, respectively. Yangla monzonites, showing O-adakitic affinity, was generated through partial melting of oceanic slab when subducting, probably subjected to metasomatism of the mantle wedge. Gongka granodiorites and Yangla granodiorites were derived from partial melting of lower crustal rocks. In general, we conclude that the subduction started from Middle Permian to Late Permian and the collision started in Late Permian and terminated in early Middle Triassic.

关 键 词：古特提斯 埃达克质岩 Ⅰ型花岗岩 地质年代学 地球化学 SR-ND同位素 岩石成因 

分 类 号：P597[天文地球—地球化学]