滇西始新世巍山岩体的岩石学成因及构造意义  

Petrogenesis and tectonic implications of the Eocene Weishan pluton from western Yunnan

作　　者：贾儒雅[1,2] 廖世勇[3] 刘铮[4] 叶春林[5] 

机构地区：[1]中国地质调查局发展研究中心,北京100037 [2]国土资源部矿产勘查技术指导中心,北京100120 [3]中国地质调查局成都地质矿产研究所,四川成都610081 [4]兰州大学地质科学与矿产资源学院,甘肃兰州730000 [5]四川省地质调查院,四川成都610081

出　　处：《中国地质》2016年第1期132-141,共10页Geology in China

基　　金：国家自然科学基金(41202048;41202067);中国地质调查局项目(12120115037101)联合资助~~

摘　　要：巍山岩体位于云南西部哀牢山—红河断裂带附近,其主体岩性为二长斑岩和石英二长斑岩。LA-ICP-MS锆石U-Pb定年表明该岩体侵位于始新世,年龄为（38.5±0.6）Ma。巍山岩体为过铝质岩石,其铝饱和指数ASI（=Al2O3/（Ca O＋Na2O＋K2O）,分子数）为1.09-1.44。所有样品具有高的K2O含量（4.50%-4.98%）和K2O/Na2O比值（1.10-1.41）。这些花岗闪长岩类呈现出埃达克质岩石的属性,例如高的Al2O3、Sr和低的重稀土（HREE）以及Y含量、Eu负异常缺失等。它们比云南西部同期的浅色过铝质侵入岩有着低的ISr和高的εNd（t）组成,暗示基性岩浆对该岩体的形成做出了贡献。岩石地球化学证据表明,该岩体最可能形成于幔源玄武质岩浆底侵诱发增厚地壳中沉积岩或者变质沉积岩发生了部分熔融。巍山岩体侵位年龄早于哀牢山—红河断裂带走滑过程（32-22 Ma）,因此其形成可能与该断裂带的走滑无关。The Weishan pluton is located in western Yunnan, close to the Ailao Mountain- Honghe River fault zone. It comprises monzonite porphyry and quartz monzonite porphyry. The LA-ICP-MS zircon U-Pb dating suggests that the pluton was emplaced in Eocene, with the age of（38.5±0.6） Ma. The Weishan pluton is peraluminous, with ASI from 1.09 to 1.44. All the samples havehigh K2 O content（4.50 %to 4.98 %） and K2O/Na2 O ratios（1.10 to 1.41）. The granitoids show adakitic affinities, such as high Al2O3,Sr, low HREE and Y content and the absence of negative Eu anomalies. The Weishan pluton has higher εNd（t） and lower ISrvalues than the coeval peraluminous plutons from western Yunnan, indicating the contribution of mantle material to the formation of the pluton. All the geochemical data imply that the Weishan pluton was likely derived from partial melting of the sedimentary or metasedimentary rocks of thickened crust, triggered by underplating of basaltic magmas. Due to the early emplacement age, the Weishan pluton was not likely related to the left-lateral displacement of the Ailao Mountain-Honghe River shear zone.

关 键 词：花岗岩类 增厚的地壳 始新世 埃达克质岩石 巍山岩体 

分 类 号：P588.1[天文地球—岩石学]