Ore genesis of the Devonian superimposed Yulekenhalasu porphyry Cu-Mo deposit in CAOB: Insights from paragenesis and fluid inclusions

The Yulekenhalasu porphyry Cu-Mo deposit is located in the Devonian Halasu copper belt, part of the East Junggar block in northwest China. At Yulekenhalasu, Cu and Mo mineralization commonly occurs as disseminations or veinlets in both porphyry-type alteration zones and late high-grade Cu sulfidebearing veins. Seven hydrothermal alteration stages were identified at the deposit, including sodic-calcic alteration (Stage I), potassic alteration (Stage II), propylitic alteration (Stage III), phyllic alteration (Stage IV), late Cu sulfide-bearing veins (Stage V), argillic alteration (Stage VI), and supergene alteration (Stage VII). Fluid inclusion assemblage (FIA) microthermometry coupled with cathodoluminescence (CL) imaging reveals that mineralizing fluid for Stage II IV had intermediate to high temperatures and variable salinities. The Stage V late Cu sulfide-bearing veins were associated with intermediate temperatures and dilute hydrothermal fluid, in contrast to low-temperature and dilute fluid in Stage VI. Stage II and III veins were overprinted by hydrothermal fluid associated with Stage V and VI via reopening of early hydrothermal veins. Discrete multi-stage alteration features in Yulekenhalasu can represent a typical example of the Paleozoic porphyry copper deposit (PCD) systems formed in the Central Asian Orogenic Belt (CAOB).