Metallogenic characteristics and ore-forming material sources of the Huachanggou gold deposit in Shaanxi Province

Located in L ueyang County of Shaanxi Province,the Huachanggou gold deposit is a small-sized deposit which is currently being mined.The gold deposit occurs in the slightly metamorphosed Middle and Lower Devonian strata composed of mafic volcanic rocks(spilite) and marine carbonate rocks.Gold mineralization is strictly controlled by a fault zone.There are mainly three types of ores: altered spilite gold ore,limestone quartz gold ore and quartz sandstone gold ore.These three types of ores occur respectively in the main ore belt,the north ore belt and the south ore belt,and the south-south ore belt.The S,C,Pb,H and O isotopic compositions show that there is a distinctive difference between the spilite ore and the limestone ore: the oreforming material source of the former ore came from deep source while that of the latter ore was derived from the upper crust.The Q-type cluster analysis of the trace elements and the REE distribution patterns show that the spilite ore and the limestone ore were closely related to the wall rocks.The geochemical characteristics clearly show that the ore-forming material sources came from the mafic volcanic rocks and the marine carbonate rocks.The data obtained also suggest that the ore-forming fluid was derived predominantly from an active meteoric groundwater system with the addition of small amounts of volcanic water.