阿尔金西段库木塔什萤石矿床成因:磷灰石U-Pb年龄、原位Sr-Nd同位素、地球化学约束OA北大核心CSTPCD

In recent years,significant breakthroughs in fluorite prospecting have been made in the western Al-tyn-Tagh Terrane,and Kaerqiaer,Kumutashi and other deposits have been discovered successively,however,the research on metallogenic epoch and ore-forming processes are still unclear.In this paper,the closely symbi-otic apatite with fluorite were selected as the research object to carry out the main microanalysis of apatite,U-Pb dating and in situ Sr-Nd isotopic test analysis,so as to explore the metallogenic epoch and the genesis of deposit.The apatite often has a self-semi-automorphic structure with uniform surface and nearly transparent under monopolarized light,mainly symbiotic with fluorite,calcite,tainiolite,bastnaesite and other minerals.The study shows that the U-Pb isotope age of apatite microregion is(448±27)Ma,and the fluorite mineralization is close-ly related to the invasive activity of alkali feldspar granite,all of which are the products of the late Ordovician tectonic-magmatic activity.The F content of apatite is 4.20%to 5.12%;the Cl content is less than 0.02%,and the very low Cl content indicates a low dissolved fluid Cl content.The content of rare earth elements is high(908×10-6～2 164×10-6),and the partition curve of rare earth shows strong Eu negative anomaly and positive Ce negative anomaly.This anomaly is obviously consistent with its associated fluorite,calcite and alkali feldspar granite,which may be closely related to the dissolution of massive fluid in the magma-hydrothermal stage.The ratio of 87Sr/86Sr of apatite is from 0.709 13 to 0.710 47,the ratio of 143Nd/144Nd is from 0.511 38 to 0.511 53,and εNd(t)is from-13.27 to-10.26,reflecting that the ore-forming materials have the characteristics of crust-man-tle mixing.Comprehensive studies show that the ore-forming age of fluorite in the western Altyn-Tagh Terrane is Ordovician,closely related to the same period alkali feldspar granite,formed in the post-collision extension stage,the ore-forming fluid may be derived from the melt-fluid evolution of alkali feldspar granite,and it is a magmatic hydrothermal filling type deposit.