Geology, Pyrite Geochemistry and Metallogenic Mechanism of the Wulong Gold Deposit in Liaodong Peninsula, North China Craton

Abstract

The Wulong deposit is a large gold deposit in the Liaodong peninsula (North China Craton). Silicic and pyrite alterations are well-developed in the deposit and closely related to mineralization. The least altered and silicified microdiorite samples were selected for major and trace element analyses to reveal the elemental migration/enrichment. Pyrites of stage 1 (Py1) were selected for backscattered electron (BSE) imaging and LA-ICP-MS trace element analyses to reveal their possible metallogenic link. Mass balance calculation showed that Al2O3, CaO, Fe2O3, K2O, SiO2, Ag, As, Cu, and Pb were brought in, whereas MgO, Na2O, FeO, Cr, Zn, and Ni were leached out during silicification. LA-ICP-MS trace element analyses show that Py1 has higher Au and Zn contents than Py2 and Py3, Py2 has higher Au and Cu contents than Py1 and Py3, and Py3 has higher Pb, Cu, and As contents than Py1 and Py2. During the process of silicification and pyritization, the depleted H+ concentration and HS− concentration in the ore-forming fluids led to instability of the Au(HS)2− complexes and led to gold precipitation. The depleted sulfur and the reduced temperature during the precipitated of bismuthinite also led to instability of the Au(HS)2− complexes and gold precipitation.