An Analysis of the Interior Structure of the Gold Hydrothermal Metallogenic System of the Northwestern Jiaodong Peninsula, Shandong Province

The study of metallogenic systems includes two branches: the geological background and the system's interior structure. The geological background analysis is based on the dissection of the macroscopic environments of representative metallogenic belts or typical ore deposit concentration areas. It emphasizes the contributions of both the layered structure of the earth and the coupling processes of the transformation of tectonic regimes, magmatic activity and fluid influx to the activation of regional ore-forming fluid and the initiation of large-scale mineralization. The study of interior structure aims to clarify the temporal-spatial structure of the mineralized web, the physical mechanism of ore-forming fluid transportation and the chemical process of the enrichment-migration-precipitation of metallogenic elements. It considers the relationship between these elements by analyzing the tectonics-fluids-mineralization process in multi-scales, including orefield, ore deposit and ore body scale. Taking the Northwestern Jiaodong ore deposit concentration area as an example, and using a method of interior system analysis, the authors try to reveal the influence of the exterior geological environment of the ore-forming system on the metallogenesis of the interior ore deposit concentration area, and to establish the intrinsic relations of ore-forming factors (ore-forming products, ore-forming processes etc.).Resultsshow that the transition of stress-strain field properties, created by the transformation of regional tectonic regimes, leads to regional ore-forming activity, which occurs in the temporal-spatial interfaces where the shearing stress alters from compression to tensile. The transformation also forms the complex and multivariate ore-controlled structural features. The differences of spatial structural features and mechanical properties result in the variety of regional metallogeny. Variations of stress-strain field properties in the ore deposit concentration area range cause the mutation of physicochemical parameters of ore-forming fluid, initiating the deposition of the metallogenic materials in the fluid. Over geological time, the fluid's Eh declined, and changed from an oxidation state to a deoxidation state. The fluid transport mode, which was under the control of different structural features, is the internal cause of metallogenic variety. The complexity of the ore-forming process mainly shows in the multi-fractal features of the spatial distribution of the gold ore bodies' grade and thickness, the self-similarity of alteration zoning, the inflation of ore-forming activity, and the variety of ore-forming products. This research is a new method of study in metallogeny and also an important approach to deepen the understanding of metallogenesis.