Hydrothermal metallogeny of the Shanggong gold deposit, east Qinling: Evidence from mineralogical study

Abstract

This paper documents the research results in mineralogy for the Shanggong gold depost, E Qinling, China, and defines a three-stage evolution of the hydrothermal metallogenesis. The early stage was marked by milky coloured, coarse-grained quartz veins, in which minerals were obviously broken and deformed with little gold. The early stage mineralization was caused by a lithostatic fluid-system of metamorphic origin in a compressive setting. The middle stage is characterized by fine-disseminated stockworks composed of polymetallic sulfides-tellurides-native elements. The stockworks filled in conjugate joints or other fissures, and show no deformation. Minerals of this generation contain much high gold and non-lattice elements. Native gold and minerals of the generation precipitated coevally in boiling phase of a metamorphic fluid-system. The fluid-boiling event was resulted from rapidly crustal uplift and erosion. The late stage formed comb-like quartz-carbonate veinlets with very low content of Au. In a extensional tectonic setting, input of hydrostatic, meteoric water into extensional fractures resulted in development of late-stage veinlets. Geological and geochemical characteristics of the Shanggong gold deposit was are similar to those of orogenic-type. Metallogenesis of the Shanggong deposit was coeval with continental collision between the Yangtze and North China plates. This shows that the Shanggong deposit is a typical example of orogenic-type gold deposit and its genesis can be interpreted by the CMF model.