Geological and S–Pb–He–Ar isotope constraints on the origin of the Muping–Rushan gold belt, Jiaodong Peninsula, eastern China

The Muping–Rushan gold belt is one of three gold mineralization belts in Jiaodong Peninsula, eastern China, comprising between the Sulu ultrahigh-pressure metamorphic belt and North China Craton. This study investigates the source of gold and ore-forming fluids in the Muping–Rushan gold belt, based on a detailed analyses of typical gold deposits. Electron microprobe elemental mapping of pyrite and pyrrhotite shows that gold and silver occur mainly as thin veins in cracks in stage I pyrite (Py1) or around stage II pyrite (Py2). The arsenic contents are higher at the rims and in cracks of stage I pyrite (Py1) and around stage II pyrite (Py2), and are positively correlated with gold contents. In situ sulphur isotope data for sulphides in the study area range between 5.8‰ and 10.1‰. The sulphides in the belt are generally character ised by δ 34 S Py > δ 34 S Sp > δ 34 S Ccp and δ 34 S Py4 > δ 34 S Py2 > δ 34 S Py1 . The δ 34 S values of mineralization stages II and III are similar to those of the Jiaodong and Jingshan Groups and the Kunyushan Complex. Lead isotopic compositions are consistent with those of the lower crust and orogenic belts. 3 He/ 4 He, 40 Ar/ 36 Ar, and 40 Ar*/ 4 He ratios of the gold deposits in the study area are 0.01–5.06 Ra, 389.8–4674.7, and 0.03–2.78, respectively, indicating that the ore-forming fluids were derived mainly from the crust, with a minor mantle contribution.