Zircon SHRIMP U-Pb dating of granodiorite in the Kaerqueka polymetallic ore deposit, Qimantage Mountain, Qinghai Province, and its geological implications

Abstract：Based on a detailed analysis of the Kaerqueka polymetallic ore deposit in Qimantage area of Qinghai Province, the authors consider that the granodiorite is closely related to the Fe-Cu-Pb-Zn skarn polymetallic mineralization. A petrological-geochemical study and SHRIMP zircon U-Pb dating of the granodiorite show that the granodiorite is composed of intermediate-acid rocks of the high-potash calc-alkaline series. The rocks are characterized by obvious fractionation of REE, enrichment of LREE, δEu values of 0.61~0.91 that indicate a weak negative Eu anomaly, high LILE (such as Rb, Th, K ) and depletion of Nb, Sr, Ti. 15 data points from SHRIMP zircon U-Pb dating show that the age is (237±2)Ma (MSWD=0.8), suggesting that the granodiorite was formed in Middle Triassic. Based on a combined study of geochronology, petrological geochemistry and evolutionary characteristics of regional structures, the authors hold that the granodiorite was formed at the post-collisional development stage in the continental orogen.