New insight into the genesis of giant Maoling arsenopyrite-type gold deposit, Liaodong Peninsula, NE China

Abstract

The genesis of the giant Maoling gold deposit in the Liaodong Peninsula of the North China Craton remains enigmatic due to the intricate gold distribution patterns and unresolved Au incorporation mechanism into arsenopyrite. The ore bodies are hosted by Proterozoic metamorphic rocks. Arsenopyrite is notably depleted in As and Fe but enriched in S. Gold contents in arsenopyrite, determined by the LA–ICP–MS spot analysis, range from 0.25 to 17.23 ppm. They are negatively correlated with Ag, Pb, and Bi, but positively correlated with Cu, Zn, Ni, Te and Se contents. Elemental concentration maps reveal Au-rich core, Mo-rich rim and Ag-rich microfracture within arsenopyrite. Our results, together with ionic radius and stoichiometric arsenopyrite, support the hypothesis that gold substitutes for Fe and As within the arsenopyrite crystal structure. New δ³⁴S ratios determined on sulfides range from 6.9 ‰ to 10.9 ‰, closely matching sulfur isotope compositions of complex magmatic origin. Additionally, much low and linear distribution along the upper-crust trend, with values of 35.411 to 36.297 for ²⁰⁸Pb/²⁰⁴Pb, 15.430 to 15.486 for ²⁰⁷Pb/²⁰⁴Pb, and 15.800 to 16.477 for ²⁰⁶Pb/²⁰⁴Pb, respectively, thus pointing to a Proterozoic magmatic origin, with contributions from late-stage magmatic activity. Collectively, the available data support a three-stage hydrothermal history for Maoling gold deposit: Proterozoic intrusion-related gold event, a Jurassic intrusion-related molybdenum event, and Cretaceous structure-controlled silver hydrothermal event.