西秦岭温泉混浆花岗岩的微量与稀土元素地球化学特征

The geochemical features and its genesis of the trace and REE of the Wenquan magma mixing granite in wester Qinling

西秦岭温泉岩体是壳、幔岩浆混浆的产物。寄主岩石高Mo、Sn、Bi、W等高温热液成矿元素及Co、Ni、Cr等亲铁元素,而基性端元的暗色微细粒镁铁质包体及基性岩墙则异常富集轻稀土和Ba、Rb、Sr、Zr、Th、Hf、Nb等大离子亲石元素,贫Co、Ni、Cr等亲铁元素。微量元素的反常分布,指示了两个端元元素演化的显著依从性和交换性。LREE/HREE值在寄主岩石中为10～15,受岩浆混合作用影响在基性端元为9.98～13.5,异常富轻稀土。δEu值及(La/Sm)N、(Gd/Yb)N、(La/Yb)N等比值,显示该岩体为混浆花岗岩。岩浆混合作用强烈的混浆暗色花岗岩具有显著的壳幔过渡性质。

The Wenquan granite, which lies in the western Qinling originates, is the product of the magma mixing of crust and mantle magmas. The host rocks are characterized by higher hypothermal metallogenic elements such as Mo, Sn, Bi and W as well as siderophile elements Co, Ni and Cr etc. The basic mafic magmatic enclave and basic dyke are rich in LREE and lithophile elements such as Ba, Rb, Sr, Zr, Th, Hf and Nb , but have poorer siderophile elements. The abnormal distribution of the trace elements indicates the noticeably exchanging and complying between the two terminal elements. The ratio of LREE/HREE is 10-15 in host rocks, but is 9.98-13.5 in basic parts because of the magmas magma mixing , namely, they abnormally enrich the LREE. The ratio of the δEu, (La/Sm)_N as well as (La/Yb)_N all indicate that this rockbody is a migmatized one, and the intensively migmatized monzonitic granite shows the markable transition between crust and mantle.