A Paleoproterozoic Gold Pre-Enrichment Mineralization Event in the Wangjiawaizi Gold Deposit, Liaodong Peninsula

The Wangjiawaizi gold deposit is a middle tonnage and quartz-vein type deposit in the Maoling gold district of Liaodong Peninsula, China. The orebody is hosted in the Gaixian Formation of Paleoproterozoic Liaohe Group, and is mainly controlled by a series of nearly parallel NW ductile shear zones in the mine area. In this study, we studied pyrite that is genetically closely related to gold mineralization, as well as sphalerite and galena for S-Pb isotopes and trace elements characteristics by using in-situ microanalytic techniques. LA-MC-ICP-MS in-situ S isotope analyses show that sulfides from the Wangjiawaizi gold deposit yielded delta S-34 values of 8.2 parts per thousand similar to 11.5 parts per thousand, which is significantly higher than that of magmatic sulfur, but overlaps with the range of delta S-34 value of the Gaixian Formation, thus inferring that the sulfur in the ore-forming fluids is derived from the Gaixian Formation. The in-situ Pb isotope analyses by LA-MC-ICP-MS show that sulfides yielded Pb-208/Pb-204, Pb-207/Pb-204, and Pb-206/Pb-204 ratios of 39.000 similar to 39.084, 15.691 similar to 15.707, and 18.623 similar to 18.664, respectively. They cluster near the upper crust evolution line and plot in the field of the Gaixian Formation, indicating that the Pb was primarily derived from the upper crustal rock of the Gaixian Formation. LA-ICP-MS trace element analyses show that pyrite yielded low Co/Ni and Te/Au ratios, and is obviously enriched in Au, As, Ag, Cu, Pb and Zn, indicating a metamorphic-hydrothermal origin. In combination with previous research, we propose that there is an early stage of Paleoproterozoic gold pre-enrichment in this Maoling gold district, and that the subsequent Early Jurassic magmatic-hydrothermal activity extracted the pre-enriched ore-forming materials from the Gaixian Formation to account for most of the gold mineralization in the Wangjiawaizi deposit. The Gaixian Formation is a significant source bed for gold mineralization in the Liaodong Peninsula, which should be given full attention in future mineral exploration work.