【摘要】 莫郎岩体位于冈底斯岩浆岩带中段,泽当镇桑耶寺北,主要由辉石闪长岩、闪长岩、花岗闪长岩和钾长花岗岩组成,本文对其进行了详细的LA-ICP-MS锆石U-Pb年代学和岩石地球化学研究。花岗闪长岩和钾长花岗岩形成时代为57Ma,具有高硅(70.1%～74.4%),低-高钾(1.3%～5.2%),低镁(0.2%～1.2%),强烈Eu、Sr负异常等特征,Zr/Nb-Zr和AFM-CFM图解表明,其形成于初生地壳物质和变质杂砂岩的低度部分熔融。辉石闪长岩和闪长岩形成时代为52～54Ma,具有低硅(53.2%～58.6%),中-高钾(1.3%～2.5%),高镁(3.2%～3.9%),弱-强烈Eu、Sr负异常等特征,与曲水岩基中基性侵入岩特征相似,是直接注入到下地壳中地幔岩浆与初生地壳部分熔融形成的壳源岩浆的混合产物。更多还原

【Abstract】 Molang intrusion, located north of Sangye Temple, Zedang Town, represents the middle part of the Gangdese magmatic belt. Lithological assemblage is composed principally of pyroxene diorite, diorite, granodiorite and K-feldspar granite. Detailed LA-ICP-MS zircon U-Pb geochronological and petrogeochemical studies are presented in this paper. Granodiorite and K-feldspar granite were emplaced at 57Ma and characterized by high SiO2(70.1%~74.4%), low to high K2O (1.3%~5.2%), and low MgO (0.2%~1.2%) contents as well as distinctly negative Eu and Sr anomalies. The Zr/Nb-Zr and AFM-CFM diagrams indicate derivation of the granodiorite and K-feldspar granite by low-degree partial melting of juvenile crust and metagreywacke. In contrast, pyroxene diorite, diorite were crystallized at 52~54Ma and characterized by low SiO2 (53.2%~58.6%), middle to high K2O (1.3%~2.5%), and high MgO (3.2%~3.9%) contents with weakly to obviously negative Eu and Sr anomalies. These characteristics are analogous to those of the intermediate to basic intrusions of the Quxu batholith. We suggest that they were produced by magma mixing between mantle-derived materials and partial melts derived from remelting of juvenile crust.更多还原