Study Of Geologic Characters Of The Duolanasayi Gold Deposit In Xinjiang

Duolanasayi gold deposit is a large gold deposit .it located at the northwest of Eerqisi metallogenetic belt in Xinjiang, it occurred in the low-grade metamorphic rock in the third lithologic unit of Devonian Tuokesalei formation.The features of Structural ore-control in Duolanasayi gold deposit is very obvious, tectonic altered rock type is the mainly ore type, the primary ore from Duolanasayi gold deposit is mainly of Altered Quartz-diorite Type and albitite- Quartz Vein Type.The alteration types of the country rocks mainly include albitization,silicification, sericitization, scarnization, chloritization and pyritization. The ore-forming temperature is between 140℃～315℃, the metallogenic pressure is mainly between 21～64.8Mpa., The pyrites are mostly widespread in all kinds of rocks . Being carrier minerals, the pyrites from Duolanasayi gold deposit are closely associated with gold. In this paper the author do some research on the typomorphic composition features of pyrites in Duolanasayi gold deposit.The average content of element Co in pyrites from Duolanasayi gold deposit is less than 500ppm , ratio ofω(Au)/ω(Ag) in pyrites is between 1～5, the average Content of element Co,element Ni and element As in pyrites from Duolanasayi gold deposit shows that the metamorphic hydrothermal fluid is the main fluid in the ore-forming fluid.Ratio ofω(Au)/ω(Ag) in pyrites is more than 0.5, which indicate that the ore-forming fluid is metamorphic genesis. Theδ34S(‰)of gold-bearing ore in Duolanasayi gold deposit is between -7.02‰～-2.46‰, Theδ34S(‰)of limestone near the gold-bearing ore is between -3.72‰～-23.74‰, it shows that the element S of Duolanasayi gold deposit comes from many ways.Duolanasayi gold deposit is hydrothermal deposit, the ore-forming fluid comes from many ways,i.e.,magmatic water, metamorphic water, underground water water, meteoric water and formation water in rocks.The Ore-forming Process of Duolanasayi gold deposit is very complicated physical and chemical process. Duolanasayi gold deposit is one of polygenetic compound deposits.According to the physical and chemical mineralization condition ,the evolution of geologic strata, the diferences of magmatic evolution, tectonic activities related to ore-forming, mineral assemblages, structure and texture of ores, alteration and physicochemical conditions, the mineralization process of Duolanasayi gold deposit can be divided into five mineralization periods ,i.e., the sedimentary period, the metamorphic period, the magmatic period, post-magmatic hydrothermal period, epigenetic period, in every period the main mineralization factor is different ,in the same period every mineralization factor has different effect on ore-formation. In this paper the author give some views about the Ore-forming Process in three aspects : regional geology, deposit geology and cause of formation.