Research On Geochemical Characteirstics And Genesis Of Jinchangyu Gold Deposit,Estern Hebei Province

Jinchangyu Gold Deposit which is one of the largest gold deposits in China isoccurred in amphibolites in Wangchang Formation within Archean Badaohe Group.Based on Regional Metallogenic theories and field surveys, the characteristics of ore,mineralgraphy, and electron microprobe are analyzed detailedly, and major elements,REE and isotope components of rocks (ores) in the deposit, and the LA-ICP-MSU-Pb age of zircon are researched systematically. Results are as follows:(1) Amphibolites are the ore source rocks of Jinchangyu Gold Deposit.(2) Au ore bodies are hosted in ductile shear zone, however, on the basis of theprevious results and microstructure studies, we conclude that there are no directrelations between ductile shear zones and ore bodies, according which we suggestJinchangyu Gold Deposit is not one of ductile shear zone deposits.(3) REE distributed patterns indicate slight differentiations between two veinsand host rocks. In addition, S isotope researches show that S in ores are mainlyoriginated from magmas, which is different from host rocks. Furthermore, H-Oisotope studies indicate that mineralizing fluids are dominant in magmatic waters.Finally, Pb isotope values suggest that Pb in ores are mainly originated from the deepand orogenes.(4) Zircon LA-ICP-MS U-Pb Chronology studies indicate tectonic events in lateArchean-early Proterozoic, with the intruding ages collected dolerite veins being95.2±2.5Ma; and the another age of186.3±6.7Ma is related to the loss of Pb whichshows magmatic events reflected by it are posterior to this concordant age which isagree with the intrusive age of Qingshankou Granite Body.(5) Au in amphibolites were preconcentrated by ductile shearing, with the brittlefaults or tectonic foliation belts overlying on the ductile shear zones being thecontrolling structures of Jinchangyu Gold Deposit. In early Yanshanian, the intrusionsof granites in the deposit provided heating sources for Au mineralization, in whichAu-bearing mineralizing fluids extracted Au from host rocks, then concentrated andprecipitated in the favorable locations. In conclusion, Jinchangyu Gold Depositbelongs to magmatic hydrothermal deposits.