The Jiaodong peninsula contains the most important concentration of gold deposits in China, with more than 150 known deposits and the proven gold reserves of as much as 4000 tonnes . The Jiaodong hydrothermal gold deposits are hosted by Precambrian basement and ultra-high pressure (UHP) metamorphic rock terranes. The terranes were overprinted by Mesozoic tectonism and magmatic events, with gold formation at about 130 to 110 Ma and thus 2 billion years later than the regional high-grade metamorphism (Deng et al., 2006). . The gold deposits cluster mainly along regional NE-NNE detachment faults between Precambrian metamorphic rocks and Mesozoic granites. The mineralization types mainly include disseminated ore in altered granites and breccias, sulphide-bearing quartz veins, and deposits with both styles of mineralization. Metallic minerals mainly include pyrite, chalcopyrite, galena, and sphalerite; nonmetallic minerals mainly include quartz, sericite, Kfeldspar and calcite. Gold minerals mainly include the electrum, free gold and minor küstelite, which mainly occur in fractures in pyrite and in quartz, with some as inclusions in sulfides. Hydrothermal alteration is mainly pyritization, silicification, sericitization, and carbonatization. The ore-forming fluids came from both the crust and mantle, with mainly a crustal source of metamorphic fluids (Yang et al., 2009). Metals were derived from the Precambrian metamorphic basement rocks that were remobilized in the Mesozoic, mingling with a small amount of material from the shallow crust and mantle (Wang et al., 2014a). The consistency of regional metallogenic characteristics indicates that the Early Cretaceous large-scale gold metallogenesis in the Jiaodong gold province is controlled by uniform geological event, and the gold deposits belong to an epigenetic mesozonal-epizonal hydrothermal metallogenic system.
Spatio-Temporal Cluster Distribution of the Gold DepositsThese gold deposits have an obvious spatio-temporal clustering and lie mainly along the contact zones between different lithofacies surrounding the three metamorphic core complexes. From west to east, the gold mineralization age changes from older to younger . Therefore, three gold subsystems can be distinguished, which are the altered rock and quartz vein type in the Jiaobei Uplift, the sulfide-bearing quartz vein type in Sulu UHP metamorphic belt, and the altered breccia type along the northern margin of the Jiaolai Basin. The respective mineralization style changes from disseminated-veinlet, veinlet-stockwork and quartz vein type, to sulfide-quartz vein type, and then to altered breccia type. The texture and structure of the ores changes from veinlet-disseminated structure, to band structure and comb structure, and then to breccia structure, indicating mineralization occurred respectively in the brittle -ductile transformation zone (approx. 15 km), a brittle extensional shear fault environment, and a brittle breccia zone setting (approx. 5 km). The decrease in the volume and intensity of alteration an...
