Genesis of the Xiling gold deposit, Jiaodong Peninsula, eastern China: Constraints from in situ trace elements and s-pb isotopes of pyrite

Abstract

The Xiling gold deposit, a newly discovered ultra-large-scale gold deposit in the Jiaoxibei ore concentration area, has a proven gold reserves of 592 tons and is classified as a fault-related hydrothermal alteration type gold deposit. This study presents in-situ trace element and sulfur-lead isotope data of pyrite from different mineralization stages in the Xiling gold deposit, providing new insights into the genesis of giant gold deposits from the Early Cretaceous. Based on petrographic observation of rocks extracted from drill holes and analysis of backscattered electron (BSE) images, the development of pyrite in the Xiling gold deposit can be divided into 4 stages and 6 subclasses. In situ trace element analysis of pyrite shows that except for stage III, the gold content in the pyrite lattice is very low, mostly less than 1 ppm, with gold mainly existing as invisible gold (lattice gold). From Py1 to Py4, there is a good positive correlation between Au and Ag, As, Sb, Cu, Pb, and Bi, with a trend of increasing content. The trace element analysis results of pyrite indicate that the initial ore-forming fluid originated from the enriched lithospheric mantle. The in situ δ³⁴S values of pyrite indicate a transition in the mineralization environment from compression and reduction to extension and oxidation. In situ Pb isotope results show that the ore-forming fluid extracted lead from the surrounding rocks during migration and mineralization. During the upward migration of the fluid, the tectonic environment experienced a transition from compression to extension, and extracted the ore-forming materials from the surrounding rocks, resulting in the deposition of a huge amount of gold.