A Large-Scale Cluster of Gold Deposits and Metallogenesis in the Eastern North China Craton

Abstract

The eastern North China craton contains the largest association of gold deposits in China. Hundreds of gold deposits of different scales, commonly in groups or belts, constitute seven subclusters. In contrast, there are no industrial gold deposits in the neighboring areas of the UHP Sulu region and the northern Yangtze craton. The host rocks of the gold deposits are chiefly Precambrian high-grade metamorphic rocks and granites (anatectic melts derived from Precambrian metamorphic rocks). Traditionally the gold deposits were considered to be of the Archean greenstone type. However, recent geochronology of granitoid bodies and veins related to gold mineralization and gold-bearing minerals in ore lodes reveals that the main metallogenic episode was 110-130 Ma in all seven subclusters. Geochemical data also indicate that the metallogenic materials mainly came from the Precambrian basement of the North China craton and its underlying mantle. Sr-Nb-Pb and S-O-H isotopic data of the ore lodes show crust-mantle mixing characteristics, corresponding to the metamorphic host rocks and basic-alkaline dikes. The main structures controlling the mineralization are Mesozoic faults that trend roughly NE-ENE and NW. Therefore, Precambrian rocks and Mesozoic magma-tectonic events provide fundamental controls on the mineralization. Problematic relationships between the Mesozoic tectonic events (Yanshanian movements) and large-scale metallogenic activity have attracted substantial attention from Chinese and foreign geologists. Mesozoic tectonic inversion in eastern China mainly involved a thick lithosphere that thinned at depth and a reconstructed basin-and-range structure at the surface, which resulted from a catastrophic lithosphere-asthenosphere event. This tectonic event led to a large-scale mantle upwelling, which induced disturbance and adjustment of thermal, density, and chemical phenomena, resulting in large-scale crustal remelting (especially the lower crust), material exchange and mixing between mantle and crust, movement and circulation of fluids, and finally a new magma-fluid-mineralization system.