Zircon U-Pb dating and geochemical characteristics of the tonalite in the Dashuigou gold deposit of Eastern Kunlun Mountains, Qinghai Province

Abstract: The Dashuigou gold deposit is located in the middle segment of Eastern Kunlun, and nine orebodies were delineated in the west of the Dashuigou gold deposit. In combination with geochemical anomalies and regional geological background, the authors hold that the Dashuigou gold deposit has good ore-search prospect. Gold ore prospecting has achieved new breakthrough. LA-MC-ICPMS zircon U-Pb dating shows that the weighted mean age of tonalite, which is closely related to mineralization in the Dashuigou gold deposit, is (239.5±0.9)Ma, with MSWD being 1.3, suggesting Middle Triassic. Geochemical studies indicate that tonalite belongs to the calc-alkaline series, with obvious fractionation of REE, enrichment of LREE and slightly negative Eu anomalies. This suite of rocks are enriched in LILE (such as Rb, K), LREE and more mobile incompatible elements (such as Th), and relatively depleted in HFSE (such as Nb, Ta, Ti, P). Rb/Sr and Nb/Ta ratios reflect the characteristics of mantle-derived magma. Based on a combined study of geochronology, geochemistry and evolutionary characteristics of regional structures, the authors hold that tonalite was formed at the subduction stage. Subduction promoted the migration of mantle-derived fluids, which precipitated in favorable?parts?of?structure, forming the gold orebody.