Geochronology,Geochemistry and Zircon Hf Isotopic Compositions of the Ore-Bearing Porphyry in the Lakang'e Porphyry Cu-Mo Deposit,Tibet

Leng Qiufeng; Tang Juxing; Zheng Wenbao; Wang Baohong; Tang Pan; Wang Hao

doi:10.3799/dqkx.2016.083

Abstract：The Lakang'e Cu-Mo deposit is a typical porphyry deposit in the eastern Gangdese metallogenic belt,on which previ-ous geochemical studies are not adequate and systematic.In this paper,we present the results of the systematic logging of drill-holes and provide new petrological zircon U-Pb age,and Hf isotope data for the deposit that allow the identification of the tim-ing of formation and mineralization of the Lakang'e porphyry Cu-Mo deposit and the relationship between this deposit and other porphyry-type deposits in the Gangdese belt.Chemical analyses show that the ore-bearing granodiorite-porphyry has high SiO2 , low Mg and Ca (SiO2 =62.51% to 72.41%,MgO=0.59% to 1.30%,CaO=0.95% to 3.44%),highalkaline (Na2 O=3.51% to 4.75%,K2 O=3.30% to 4.97%),metaluminous (A/CNK=0.90 to 1.01),enriched in LILES such as Rb,Ba, Th,U,Sr,and depleted in HFSES such as Nb,Ta,Ti,P and Zr.The rocks also display low total REEcontents (∑REE=82.80×10-6 to 132.09×10-6 ),enriched LREE and differentiate obviously,with weakly negative Eu and Ce anomalies.LA-ICP-MS zircon U-Pb dating indicates that the Lakang'e ore-bearing granodiorite-porphyry emplaced at 13.58±0.42 Ma.εHf (t) values and two-stage model ages of zircons are -3.99 to 4.49 and 808 to 1349 Ma respectively.The results indicate that the ore-bearing granodiorite-porphyry in the Lakang'e deposit has adakitegeochemical characteristics,and the parental magmas were mainly derived from a juvenile crust and partly mixed with old continental crust rock during the evolution.The porphyry in Lakang'edeposit was formed in post-collisional extension setting of India-Asia continental collision orogenic belt.