Characteristics Of Ore-forming Fluid And Ore Genesis Of Dahu Gold Deposit, In Xiaoqinling Gold Area

Xiaoqinling gold area, the most important Au metallogenic area in China, locatedin south margin of North China Platform, which is evolved in and become onecomponent of Qinling orogenic belt. In the area, there are more than one thousandgold quartz veins and forty gold deposits have been explored. In this paper, we choosethe Dahu gold deposit located in the north part of Xiaoqingling area as the target.Geological characters of the deposit, geochemistry condition and regional tectonicevolution have been comprehensively studied in order to understand the metallogenicGeological Condition of the Dahu gold deposit.Though systematical study in geology character, fluid inclusion geochemistry,stable isotope, radioactive isotope and the contrast with other typical gold quartz veinin the Xiaoqinling gold area, we discussed the character and genesis of ore-formingfluid and the mineralization and precipitation process of Dahu gold deposit. The mainresult we got as follow:The orebody are controlled by ductile shear zone and F5 is the main ore-controlstructure. There are some tensional fracture well developed in the belt whichcontrolling the occurrence of gold quartz vein and gold ore-body.The study of fluid inclusions indicate that the ore-forming fluid are characterizedin mid-temperature, mid-salinity with low ore-forming press and depth compared withother quartz vein type deposits in Xiaoqinling area.H, O, S, Pb and He isotopes of gold-bearing quartz veins indicate that theore-forming fluids were dominately derived from the upper mantle and gradually mixed with crustal fluids along with the metallogenic process. According tothe temporal and spatial link between the gold mineralization and tectonic evolution of regional extension in combination with researcher's achievements, the authors hold that the main gold mineralization occurred at the post collisional stage of late Mesozoic, being products of the regional extension resulting from the deep process. The extensional tectonic system provided dilatational space formigration, mixing and water/rock interaction of the ore-forming fluids as wellas gold enrichment and deposition.