Destruction of the North China Craton account for the Shijia gold deposit in the Jiaodong Peninsula, eastern China

Abstract

The Jiaodong Peninsula hosts the largest gold reserves in China, with proven gold reserves exceeding 5000 tons. Although the continuous discovery of new gold deposits in this region, the geodynamic background and the source of ore-forming materials of mineralization remain subjects of debate. Resolving this issue will be of great significance for further mineral exploration. This study focuses on the Shijia quartz vein-type gold deposit, which is hosted in Guojialing-stage granitoids within the Jiaodong Peninsula. We employ a variety of analytical techniques, including zircon LA-ICP-MS U–Pb isotopic dating, pyrite Rb–Sr isochron dating, geochemical analyses of the Shijia granodiorite, in-situ sulfur isotope and trace element analyses of pyrites, in order to obtain the accurate timing of gold mineralization and to uncover the origin of ore-forming materials. Our results show that the Shijia granodiorite was emplaced at 122.9 ± 0.2 Ma. The Rb–Sr isochron analysis of gold-bearing pyrite determines its mineralization age to be 121.3 ± 2.4 Ma, which agrees well with both the crystallization age of the Shijia intrusion and the time of destruction of the North China Craton, implying their genetic connections. Whole-rock geochemical data indicate that the Shijia granodiorite originated from a mixing magma source, primarily composed of ancient lower continental crust with approximately 20 % contribution from asthenospheric mantle, which is possibly formed in the background of the North China Craton destruction. The sulfur isotope values (6.22 to 7.59 ‰) of the gold-bearing pyrites point to a primary contribution from deep mantle sources for the ore-forming fluids. Based on the aforementioned features and the strong spatial and temporal correlation between mafic dykes and gold mineralization, we suggest that the Shijia gold deposit is a product of cratonic destruction. The destruction of the North China Craton is likely responsible for the ascent of asthenospheric material, which in turn triggered the partial melting of the metasomatized subcontinental lithospheric mantle and the ancient lower crust. This process generated large-scale contemporary granitic rocks, mafic dykes, and associated gold mineralization.