Geochronology,Geochemistry and Petrogenesis of the Harizha-Nagengkangqieer Granites in the East Kunlun Orogen
Several large silver deposits occur in the East Kunlun Orogen but their tectonic setting and related Paleo-Tethyan evolution are highly debated.Geochronological and geochemical works on the granites and porphyritic granites in the Harizha-Nagengkangqieer silver deposits of the East Kunlun Orogen were made in this study.LA-ICP-MS zircon U-Pb dating shows that the Harizha granites were emplaced at 255 Ma and the porphyritic granites in both areas between 220 Ma and 224 Ma.Late Permian Harizha granites have high SiO2 and K2O+Na2O but low CaO and MgO contents with enriched light rare earth elements,depleted heavy rare earth elements and high field strength elements,negative Eu anomalies,high Ga/Al ratios and Zr+Nb+Ce+Y values,and thus are A-type.These rocks were generated by partial melting of crustal calc-alkaline I-type granitoids in a back-arc extensional setting because of their relatively high K2O/Na2O,Ga/Al,FeO/MgO ratios.The Late Triassic calc-alkaline,peraluminous porphyritic granites are related to silver mineralization with similar major elements but low contents of trace elements compared to the Late Permian granites,are thus the result of fractional crystallization in a post-collisional background according to this and numerous previous data.
East KunlunHarizhaNagengkangqieergranitegeochronologygeochemistry
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