滇西始新世十里村正长岩的成因及构造意义

Petrogenesis and tectonic implications of the Eocene Shilicun syenite from western Yunnan

十里村岩体出露于滇西哀牢山走滑断裂带附近,主要由石英碱长正长岩和石英正长岩构成,形成于始新世(~36.8 Ma).样品呈现出准铝质的特征,具有高碱、高Si、低Yb、低Y.Sr-Nd同位素值落在来自下地壳的斜长角闪岩捕虏体同位素范围内.岩石学和地球化学特征表明十里村岩体很可能产出在厚的岩石圈地幔移除诱发软流圈上涌的后碰撞环境下.

The Shilicun pluton from western Yunnan is exposed adjacent to the Ailaoshan fault zone. It comprises quartz alkali-feldspar syenite and quartz syenite. The pluton was emplaced at ~36.8 Ma. All the samples,being metaluminous, have a high alkali content,high Sr and low Yb and low Y content.The initial Sr-Nd isotopic data were plotted in the field of xenolithes from the mafic lower crust. The occurrence of the Shilicun pluton indicated that the Cenozoic potassic magmatic belt was formed in a post-collisional setting, in response to asthenospheric upwelling triggered by removal of the thickened lithospheric mantle root.