Geochronology and geochemistry of Tianhexing porphyry Cu Mo deposit, northeast China

Abstract

Abstract The Tianhexing porphyry Cu Mo deposit is located in the southeastern Jilin on the northeastern margin of the North China Craton (NCC). In this paper, we present a study on the geochemical and Sr-Nd-Hf, sulfur and lead isotopic data for the ore-bearing granite porphyry and sulfide minerals in the deposit. Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) dating of zircon grains from granite-porphyry yields age of 120.9\u202f±\u202f0.3\u202fMa. Six molybdenite samples separated from Tianhexing deposit are used for Re Os dating and obtained the weight mean age of 120.8\u202f±\u202f0.75\u202fMa and an isochron age of 121.5\u202f±\u202f1.4\u202fMa. These ages suggest that the hydrothermal Cu Mo mineralization and felsic magmatism are nearly contemporary. Geochemically, the Tianhexing granite porphyry belongs to a medium-K to high-K calc-alkaline, weakly peraluminous series, is enriched in Rb, Th, U, K but is depleted in Ba, Sr, P, Ti. with intermediate Eu negative anomalies (δEu\u202f=\u202f0.46–0.52). The ore-bearing porphyry has relatively low eNd(t)(−13.3 to −11.8), eHf(t) (−18.3 to −11.4) and high 87Sr/86Sr ratios (0.7105 to 0.7172). We infer that the parental magma formed Tianhexing granite porphyry originated from mixed sources of mature crust and enriched mantle. The δ34S values of ten sulfides range from +2.1‰ to +4.0‰, with a mean of +3.3‰, and three other sulfides have 206Pb/204Pb ratios from 16.69 to 16.80, 207Pb/204Pb ratios from 15.44 to 15.47, and 208Pb/204Pb ratios from 37.7 to 38.40. Concentrations of total Re range between 0.53 and 3.84\u202fppm from six molybdenite samples. It is considered that metallogenic materials may be derived from the mixed sources parent magma, and metal Cu source of Tianhexing deposit was most likely generated from enriched mantle metasomatized by fluid, but the metal Mo source was derived from mixed ancicent crustal melting. Combined with the regional geological background, it is suggested that the Tianhexing deposit formed under an extensional regime related to peak subduction of the Paleo-Pacific plate beneath Eurasia, and the late Early Cretaceous hypabyssal to super hypabyssal calc-alkaline acid intrusions are important targets in exploration for porphyry Cu, Cu Mo deposits in northeast China.