Zircon geochronology, geochemistry and stable isotopes of the Wang’ershan gold deposit, Jiaodong Peninsula, China

Abstract

The Early Cretaceous gold deposits of the Jiaodong Peninsula, eastern China, define China’s largest gold province with an overall endowment estimated more than 3000tAu. The Wang’ershan gold deposit at the northern margin of the Jiaolai Basin in Jiaodong Peninsula of eastern China is located in the central-southern segment of the Wang’ershan fault zone. The major Mesozoic intrusions exposed in this region are the Linglong granite and the Guojialing granodiorite to the northeast of the deposit. Both these intrusions show high-K and alkaline signature. The Linglong granite displays peraluminous feature whereas the Guojialing granodiorite is metaluminous. Zircon U–Pb dating of the Linglong granite yields 206Pb/238U weighted mean age of 149.0±1.3Ma. The muscovite from the alteration zones associated with mineralization in the Linglong granite yields a plateau age of 130.35±0.96Ma, representing the initial phase of the hydrothermal activity. The δ34S values of pyrite from the gold mineralized veins range from 6‰ to 8.3‰ with the mean value of 7.66‰. The 3He/4He ratios of pyrite are in the range 1.58–2.71 Ra with a mean value at 2.168 Ra. The 40Ar/36Ar ratios show variation from 1220.3 to 1625.7 with an average of 1483.8. The δ18O values of the mineralizing fluids show a range of −2.13‰ to 7.5‰, with an average of 2.4‰. The δ18Dw values are in the range of −97.5‰ to −61.4‰, with a mean at −82.6‰. Detailed elemental and isotopic data suggest that the hydrothermal fluids in early stage were mainly magmatic and derived from the Guojialing granodiorite, and the ore-forming fluids in the main ore-forming stages evolved into a mixture of magmatic and meteoric water. The ore-forming materials were primarily derived from crust, with minor input of mantle components. The ore-forming fluids might be related to the subduction of the paleo-Pacific slab beneath the North China Craton and the associated asthenosphere upwelling and consequent lithospheric thinning.