Magma mixing genesis of the Qushui collisional granitoids,Tibet,China:Evidences from genetic mineralogy.
西藏曲水碰撞花岗岩的混合成因：来自成因矿物学证据

The Qushui collisional granitoids in Tibet is located in the middle part of the southern Gangdis Mts.,extending west to east parallel to the Yarlung Zangbo Suture.The granitoids mainly consist of mid-coarse-grained granodiorite and quartz diorite with abundant mafic microgranular enclaves(MMEs).Genetic mineralogical and petrographical studies suggest that the Qushui granodiorite and MMEs were generated by magma mixing and could not be evolved magma by FC(AFC)which is excluded by evidences as follows:(1)Oscillatory zoning of plagioclase with basic core and rim,but felsic mantle;(2)Amphiboles and biotites as inclusions in the rim of the feldspars,but seldom in the core;(3)Temperature increased from the core to rim of K-feldspar phenocryst;(4)Relatively high content of the Cr,Ni, Co elements in feldspars than those of the crust granitoids;(5)Contents of MgO in both amphiboles and biotites indicating their crust- mantle sources;(6)Needle shape of the apatites and amphiboles in MMEs implying the process of fast cooling.Pressure and temperature estimated with mineral Geothermo-barometers further support magma mixing is the main process of the Qushui granitoids and enclaves due to different emplacement depth between the host rocks and their enclaves,but approximately the same forming temperature.