Geological and Geochemical Constraints on the Newly Discovered Yangchongli Gold Deposit in Tongling Region, Lower Yangtze Metallogenic Belt

Abstract

AbstractThe newly discovered Yangchongli gold deposit is a unique independent gold deposit in the Tongling ore‐cluster region controlled by the tectonic alteration firstly discovered in the Lower Yangtze Metallogenic Belt (LYMB). The host magmatic rocks mainly consist of monzodiorite and K‐feldspar granite. The LA‐ICP‐MS U‐Pb zircons dating yielded weighted mean 206Pb/238U ages of 140.7 ± 1.8 Ma and 126.4 ± 1.2 Ma for the monzodiorite and K‐feldspar granite, respectively. Monzodiorites are enriched in Sr, Ba, Rb, and depleted in Y, Yb with high Sr/Y and La/Yb ratios, similar to the geochemical features of adakite, considered as products of differentiation of mafic magmas originating from lithospheric mantle melt/fluids caused by metasomatism during paleo‐Pacific Plate subduction in the Mesozic. In contrast, the compositions of K‐feldspar granites are A‐type granites, indicating an extensional tectonic background. Gold ores hosted in the fracture zone occurred as quartz vein within cataclastic rock. Sulfur and lead isotopes from pyrites show crust‐mantle mixing characteristics. Metal components from strata also took part in the gold mineralization, and resulted from two episodes of magmatism that were probably related to tectonic transition from a compressive to an extensional setting between 140–126 Ma, which led to the Mesozoic large‐scale polymetallic mineralization events in eastern China.