Tectonics-Fluids-Mineralization System Of Jiapigou Gold Belt In Jilin Province, China

The Jiapigou Gold Belt in Jilin Province, northeast China, has been an important areaof gold mining and production in the Circum-Pacific metallogenic zone for more than 190years. The region produces about 1500 kg of gold per year and currently has more than 100t of gold reserves. To preliminary construction of tectonics–fluids - mineralization systemin Jiapigou gold belt, and also to establish the metallogenic model, a systematic regionalgeological, deposit geological, geochronological, major elements, trace elements, rare earthelements, stable isotope, and fluid inclusions geochemical investigation on the basis ofmineralization system theoretical framework was conducted.Jiapigou Gold Belt is located in the eastern section on the northern edge of the NorthChina Craton (NCC), and the southern flank of Jilin-Heilongjian block in eastern Siberiaplate. The gold deposits are mainly distributed in the area between the Jiapigou granite–greenstone (GGSB) belt and the Paleoproterozioc potassic granite, but closer to the GGSB,and also control by the NW-trending Jiapigou–Dashilazi ductile shear zone. This shearzone is also called Jiapigou gold belt, where the ore deposit type is mainly gold-bearingquartz vein type (up to 90%), as well as disseminated ore type and altered rock type. Theore bodies are mainly occurred in the NWW, NNE to NEE-trending brittle - ductile shearzone or fractures.The study revealed that metallogenic materials are extracted from wall rock stratum(GGSB), However, that the metallogenic fluids are mainly derived from magmatichydrothermal, though probably contaminated by metamorphic fluids and mantle fluids, andare CO₂-H₂O-NaCl (CaCl₂) solutions featured by low to medium temperature, CO₂-rich,low salinity and density, low fO₂, weak reduction and acidity, that the mineralizationdepths are 1.73 - 3.7 km with the trend of deeper when the deposit more close to thesoutheast, that the research area underwent two rapid uplift periods after Mesozoic era, andthe thickness of uplift and denudation are 2.28 - 3.05 km and 2.66–2.83 km, respectively.A two phases and multistage metallogenic model are proposed as well in this study. Inthe early Paleoproterozoic Era, the intrusion of magmatic fluids that generated in thepotassic granitic magma which came from partial melting of basic rock in the late orogenicstage along the Jiapigou ductile shear zone, and the contamination with the gold-bearingmetamorphic hydrothermal fluids that produced by large scale regional metamorphismresulted in the changes of pH and other parameters, and then formed the NW-trending ore bodies, the mineralization epoch is 2475 - 2468 Ma. In the Triassic, large-scale sinistralstaike-slip displacements on the NE-trending Huifahe and Liangjiang Faults resulted fromthe collision and subduction of the Izanagi plate beneath the Eurasian plate. The JiapigouFault was folded and a series of radial NW and NNE-ENE-trending tensional joints andfractures was derived near the hinge zone. At the same time, anatexis granitic magmaticfluids derived from the intensive tectonic activity, extracted the gold from the wall rocks(TTG, greenstone) and intruded into the joints and fractures, leading to a new goldmineralization, and reformation the earlier ore bodies as well, the mineralization epoch is158–152 Ma.