Characteristics And Genesis Of The Xiangtanzi Gold Deposit In Gansu Province

The Xiangtanzi gold deposit is a recently discovered large gold deposit in the western Qinling Mountains.The geological characteristics of the Xiangtanzi gold deposit are similar to those of the magmatic hydrothermal deposits,but are different from the orogenic gold deposits.Therefore,a detailed study on the deposit would provide important evidence for understanding gold mineralization mechanism and further gold exploration in the western Qinling Mountains.A detailed geological and geochemical study has been carried out on the Xiangtanzi gold deposit,with a focus on an analysis of source of ore-forming materials and genesis of the deposit.There are three types of ores in the Xiangtanzi gold deposit:?,?and?,they are distributed in NW trending faults,granite veins and EW trending faults respectively.These three types of ores have similar ore characteristics and hydrothermal alteration.Ore textures are mainly anhedral granular and metasomatic relict,and structures are mainly of vein type.Ore minerals include pyrite,and minor chalcopyrite,pyrrhotite and arsenopyrite,while gangue minerals include quartz,feldspar,sericite and carbonates.Gold minerals occur mainly as intergranular gold and inclusive gold in pyrite.Hydrothermal alteration is chiefly represented by alkaline metasomatism,silicification,serotonization and carbonation.The three types of ores in the Xiangtanzi gold deposit have similar geochemical characteristics,suggesting that they are the products of the same mineralization system.The trace and rare earth elements distribution patterns of the ores in the Xiangtanzi gold deposit are consistent with those of Indosinian magmatic rocks,but are different from those of metamorphic rocks,indicating the ore-forming materials were from Indosinian magmatic system.The?³⁴S values of sulfide minerals from the Xiangtanzi gold deposit display remarkable homogeneity and range from-5.2‰to+2.0‰,similar to those of Indosinian magmatic rocks,further indicating that the sulfur was derived mainly from a magmatic source.The comprehensive analysis shows that the Xiangtanzi gold deposit is one of the magmatic hydrothermal gold deposit.