Composite Metallogenic Systems in the Weihai Area of Shandong and Evolution of Continental Dynamic Regimes

Abstract: Based on 9 sheets of l:50,000‐scale regional geological survey and guided by the theory of metallogenic systems and integrated analyses of the structural and metallogenic features, this paper hereby puts forward the composite metallogenic systems of the Weihai area, Shandong Province, aiming at solving the problems on the origins and ore‐controlling structures of the numerous deposits in the area. Its scientific significance is reflected in the following three aspects: (1) The basic features of the composite metallogenic systems can be recognized, which consist of two types: the Proterozoic metamorphic‐hydrothermal metallogenic system and the Mesozoic magmatic‐hydrothermal metallogenic system (i.e. the Indosinian‐early Yanshanian contact metasomatic metallogenic series and the mid‐late Yanshanian magmatic‐hydrothermal metallogenic series). The two series display arcuate and NW‐right lateral arrangements and a N‐S parallel zonal distribution respectively, with the corresponding mineral assemblages being Au+Ag+Pb+Zn, etc.; and Cu+Mo+Fe, Au+Ag+Cu+Pb‐Zn+Mo+Co‐Ni+suIfides+silicides+K‐feldspar, etc. (2) The composite metallogenic systems may be used to interpret the complicated genetic relations of the deposits. Through analyses of the relations between the three main metallogenic intervals and their corresponding source rock series (the Jingshan and Rongcheng groups; the Wendong super‐unit and the early‐middle Yanshanian Weideshan super‐unit; and the mid‐late Yanshanian Weideshan and Laoshan super‐units) as well as a case study of the Fanjiabu gold deposit, we have distinguished the consanguinity between the contact metasomatic (skarn‐type) metallogenic series and the magmatic‐hydrothermal metallogenic series as well as the noncognate superposition between the two and the metamorphic‐hydrothermal metallogenic system. (3) The composite metallogenic systems are easily related to the evolution of continental dynamic regimes. The formation of the metamorphic‐hydrothermal metallogenic system has undergone transformations of three different types of tectono‐dynamic regimes from extensionŕcompressionŕshearing that of the contact metasomatic (skarn‐type) metallogenic system from compressionŕextensionŕcompression; and that of the magmatic‐hydrothermal metallogenic system from extensionŕsubductive compression of the Pacific Plate. The evolutions of the three types are all attributed to the opening‐closing or divergence‐convergence of the paleocontinent, and all their mineralization corresponds to the interval of transformation from the end of convergence to early integration of the Weihai paleocontinent. All these will benefit our deeper study of the dynamics of continental metallogenic processes.