Geochemical Characteristics of Calcite and Bastnäsite U–Th–Pb Age of the Huangshui’an Carbonatite–hosted Mo–REE Deposit, Eastern Qinling

The Huangshui’an deposit, located in Xiong’ershan ore concentration area in the southern margin of the North China Craton, is one of the typical carbonatite–hosted Mo–REE deposit in the East Qinling Mo metallogenic belts. The Mo–REE ore bodies of the Huangshui’an deposit mainly are hosted in carbonatite which occur as veins and cryptoexplosive breccia intrusions in the Taihua Group. Based on the study of trace elements and C–O isotopic compostion of calcite, and bastnäsite U–Th–Pb dating, we discuss the origin of carbonatite, metallogenic age and tectonic setting, which provide constraints for tectonic evolution and mineralization in the East Qinling belt. The trace elements of calcite are characterized by enrichment of large ion lithophile elements and depletion of high field strength elements, and are enriched in LREE (LREE/HREE=3.08～10.33). The δ¹³ C_V-PDB values of calcite ranging from −4.11‰ to −5.62‰ and δ¹⁸ O_V-SMOW values ranging from 6.40‰ to 7.62‰ indicate the characteristics of primary mantle–derived carbonatite. The weighted average age of U–Th–Pb dating of bastnäsite is 213.5±2.9 Ma, representing the age of REE mineralization in the Huangshui'an deposit. Based on diagenetic and metallogenic age and available isotopic ages, we propose that the metallogenic age of the Huangshui’an deposit is Late Triassic. The Huangshui’an carbonatite–hosted deposit was formed in the post–collisional setting of the Qinling orogenic belt. The partial melting of Mo–fertile lower crust and enriched mantle formed the carbonatite magma, and the recycling of crustal material is one of the key factors for the formation of carbonatite–hosted Mo–REE mineralization.