Type and Distribution of Gold Deposits along the Northern Margin of the North China Craton, People's Republic of China

Abstract

Gold deposits and prospects are widely distributed along the northern margin of the North China craton. Up to the present, about 900 individual gold deposits, which constitute one of the most important gold metallogenic belts and the second largest gold-producing base in China, have been discovered, explored, and mined. About one-third of China's endogenic gold deposits and 45% of its gold reserve come from this belt, particularly in the Early Precambrian metamorphic terrains. All these gold deposits can be classified into five principal types according to their host rocks: (1) gold-bearing quartz or albite-quartz veins hosted by Archean amphibolite, gneiss, and migmatite; (2) gold-quartz veins hosted by Proterozoic schist, slate, sandstone, and marble; (3) gold deposits hosted by or related to intrusive complexes, including (3a) calc-alkaline granitoids, (3b) alkaline syenite and monzonite, and (3c) ultramafic intrusions; (4) gold deposits occurring in Phanerozoic volcanics; and (5) a group containing placer gold. The tectonic settings, geological features, and temporal and spatial distribution of these different types of gold occurrences indicate that gold mineralization reflects to a great extent the evolution of tectonic environments at the northern margin of the North China craton throughout geological time. Type-1 and -2 deposits generally are hosted by Archean and Proterozoic volcano-sedimentary rocks with variable degrees of metamorphism. The ore-forming materials of these two categories were derived from their wall rocks and were enriched by late metamorphism and magmatism. Types 3 and 4 are recognized in different stages and in various intrusive rocks and volcanics that were formed during Hercynian and Mesozoic Yanshanian orogenies. Gold and base metals were deposited from aqueous fluids with relatively low CO2 content (<20 mol%) and low to moderate salinity (5 to 16 wt% NaCl equiv.) that were related to a mixed fluid of magmatic and meteoric water. Type 5 results from recent weathering of existing gold-bearing volcano-sedimentary, metamorphic, and intrusive rocks as well as gold ores or protores.