Genesis of the Xinfang Gold Deposit, Liaodong Peninsula: Insights from Fluid Inclusions and S-Sr Isotopic Constraints

Abstract

The North China Craton (NCC) has been continuously reactivated since the Mesozoic and this decratonization is responsible for its economically important gold mineralization in the Mesozoic. The Early Cretaceous (110–130 Ma) gold mineralization in the NCC has been well-studied due to its significance, but little attention has been given to other episodes of gold mineralization related to polyphased reactivation of the NCC. The Xinfang mesozonal gold deposit (143 Ma) in the Liaodong Peninsula is related to the one of the episodes of the Yanshanian orogeny. The orebodies of the Xinfang gold deposit were controlled by the low angle transpressive fault systems and hosted by the Neoarchean monzogranitic gneiss. Fluid inclusion microthermometry reveals that the mineralizing temperatures range from 220 to 280 °C, with salinities from 6 wt.% NaCl eqv. to 15 wt.% NaCl eqv., pressures from 199 to 321 Ma. The S isotopic characteristics of sulfides not only record a heterogeneous source including magmatic or gneissic sulfur but also record inter-mineral isotope fractionation. The initial 87Sr/86Sr values of pyrite (0.713 480–0.729 031) indicate a radiogenic crustal origin for the sources. The metamorphic dehydration of the underlying basement resulted in the genesis of the Xinfang gold deposit. We summarize three episodes of gold mineralization in the Liaodong Peninsula related to continuous reactivation of the NCC, which indicates a great exploration potential of this area.