小秦岭、熊耳山金矿区中基性岩墙的岩石化学研究

通过对小秦岭、熊耳山金矿区岩墙的地质学、岩石学、地球化学的综合研究,查明该岩墙主要由辉绿岩和煌斑岩类组成,属钾质、中等铝质岩石并富含挥发份(>2%)的中基性岩。岩石富集LILE和LREE,与原始地幔相比具有明显的Ti、Nb负异常和Pb正异常。对形成岩墙的岩浆演化过程研究后认为,其岩浆演化大致分为三个关键环节:(1)早中生代时期富钾、富硅熔体交代秦岭造山带岩石圈地幔,导致具富集地幔特征的玄武质岩浆的形成;(2)玄武质岩浆与区域热效应形成的花岗质岩浆的混合(混染)作用;(3)混合岩浆在深部热力学和动力学机制下的结晶分异和连续演化过程。

Petrochemical research on intermediate-basic dykerocks in Xiaoqinling,Xiong'ershan goldfield, Henan province, Central China

By comprehensive study on geology,petrology and geochemistry of dykerocks in the Xiaoqinling and Xiong'ershan area,we identified the main dykerocks as intermediate-basic rocks,including diabases and lamprophyres.The major elements of dykerocks vary in a large range,with high potassium,met-aluminous and enriched volatile components.The dykerocks are enriched in LILE,LREE,and show negative Ti and Nb anomalies,and positive Pb anomaly relative to primitive mantle.Through our study,we suggest that the magmas evolution relevant to the formation of the dykerocks may be divided into three stages.(a)In the early Mesozoic,fluids and melts with high potassium and silicon had undergone matasomatism with lithospheric mantle in upper mantle source in the Qinling orogenic belt,leading to the formation of basaltic magmas with enriched mantle characteristics.(b)The basaltic magmas mixed with granitic magmas formed by regional thermal effect.(c)The mixed magmas ascended through continental crust,and underwent crystallization,differentiation,assimilation and continued evolution by thermodynamic and dynamic mechanisms.