U–Pb zircon and geochemical constraints on age and genesis of granitoids from the Jinchang Au deposit in Heilongjiang, NE China


The Jinchang Au deposit is a large-sized deposit in Heilongjiang Province, and mineralization is closely related to the Early Cretaceous granitoids. The orebodies occurred within granite, granite porphyry, granodiorite, and diorite. Gold mineralization type consists of crypto-explosive breccia, vein, and veinlet-disseminated types. In this paper, we present U–Pb age as well as major and trace element geochemistry of intrusive bodies from the Jinchang deposit. Our study indicates that granite, granite porphyry, and granodiorite from the Jinchang deposit are calc-alkaline to high-K calc-alkaline with geochemical characteristics of typical island-arc environment. Diorite and diorite porphyrite show calc-alkaline affinities with geochemical characteristics of adakite or adakitic rock. Concordant zircon U–Pb ages of 184.69 ± 0.98 Ma and 203.62 ± 0.86 Ma are obtained from granites; 190.4 ± 4.7 Ma, 205.88 ± 0.95 Ma, and 109.0 ± 2.4 Ma are obtained from granite porphyry, granodiorite, and quartz diorite. Combined with previous geochronological data, the diagenetic ages for granitoids in the Jinchang deposit are mainly focused on 2 episodes: 110 ~ 120 Ma and 185 ~ 200 Ma. The corresponding tectonic settings for the 2 episodes of magmatic activities are subduction of the Izanagi Plate towards the Eurasian Plate, and post-collision system after the collision of North China Craton and Jiamusi-Khanka Massif, respectively. We suggest that the magmatism (110 ~ 120 Ma) formed adakitic diorite and diorite porphyrite and closely associated with mineralization. Upwelling mantle results in partial melting of the lower crust and extract and transfer metals to the upper crust for further concentration. It also reveals that Jinchang Au deposit is an adakite-associated deposit.

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