Zircon U-Pb geochronology,geochemistry and geological significance of Xiarihamu granodiorite in Eastern Kunlun orogenic belt,Qinghai

作者：YANG Baorong,MA Zhongxian,ZHANG Libin,WANG Xiaoyun,YAN Zhengping

摘要：Zircon U-Pb geochronology and geochemistry of the granodiorites in Xiarihamu Cu-Ni mining area are studied to determine the formation age,genesis and tectonic setting.The results show that the granodiorites formed in the Middle Triassic with weighted average age of 242±1 Ma.The granodiorites comprise of SiO 2 of 61.34%--62.54%,Al 2O 3 of 16.46%--16.87%,MgO of 2.37%--2.66%,(Na 2O+K 2O)of 5.39%--5.74%with the Na2O/K 2O of 1.46--1.88,Mg^#of 47.03--48.04,and show metaluminous characteristics with A/CNK of 0.94--0.96,belonging to calc-alkaline I-type granites geochemically.The light and heavy rare earth elements in the rocks are distinctly fractionated and have"right-inclined"distribution patterns with weak negative Eu anomalies(δEu=0.84--0.91).Moreover,these samples show enrichments in LILEs(e.g.,Rb,Ba,K and Sr),especially in Sr[(343--452)×10^-6],and obvious depletions in HFSEs(e.g.,Nb,Ta,Ti and P),indicating geochemical characteristics similar to subduction-related magmatic rocks.According to the regional tectonic evolution,the Xiarihamu granodiorites were emplaced under an Andean-type active continental margin environment in the early Indosinian,possessing a crust-mantle mixing origin.

发文机构：Qinghai Provincial Bureau of Nonferrous Metaland Geological Exploration

关键词：MiddleTRIASSICPETROGENESIStectonicsettinggranodioriteXiarihamuNI-CUminingarea

分类号： P[天文地球]