Mineralogy And Fluid Inclusions Of The Sandaowanzi Gold Telluride Deposit, Heilongjiang

Sandaowanzi Deposit is an independent gold telluride's deposit, which is first reported in China or even in the world, whose industrial type is Quartz vein type. The wall rock is trachyte andesite of Talimugou Group, and the main ore body is the quartz veins which located in NWW trending fractures. The most important alteration in quartz veins and wall rock is solidification as well as hybridization, eroticization, kaolinization, chlorination, carbonation and so on, all of which represented multistage and diversification.Telluride dominates the metal ore minerals, and more than 95% of gold budget in the ores occurs as telluride. Almost all the gold occurs as gold tellurides, with petzite and sylvanite as the dominant minerals and hessite, calaverite, krennerite and stuetzite as the substantial minerals, which is symbiotic with a small amount of altaite and coloradoite. Gold and silver minerals are of very little amount. The main sulfides are pyrite, chalcopyrite, sphalerite, galena and chalcocite sorted by volume percentage from maximum to minimum.In this dissertation, the composition, distribution, occurrence of the main metal mineral are analyzed and ore occurrence and paragenetic association of tellurides are analyzed by optical microscopy and scanning electron microscopy, based on which the mineralization stage are divided and the mineral paragenetic sequence is established. Mineralization of gold and silver tellurides in Sandaowanzi gold deposit shows the characteristics of multi-stage in a period. A Six-stage paragenetic sequence of mineralization is proposed, which consist of an early period of high sulphide mineral associations, a late period of low sulphide mineral associations and a general trend of increasing gold in tellurides. The first stage is quartz-pyrite stage. The second stage is quartz-sulphide multi-metal stage. The third stage is characterized by the coexisting assemblages of Au, Ag tellurides. The fourth stage is micro-veinlet of telluride stage. The fifth stage is the stage of gold and silver telluride (telluride vein phase). The sixth stage is the native gold stage. The first two stages of mineralization are divided into early stage, after the four-stage is divided into the main ore-forming stage.Fluid inclusions in quartz are the main types of liquid-rich inclusions. The results of fluid inclusions temperature tests can be divided into four steps: 230-396℃with an ambiguous peak; 220-320℃with the peak 260-280℃; 140-300℃with the peak 180-240℃, which corresponds to early stages of mineralization, the main ore-forming stage and quartz veins of late stage. The result of probe in-situ by laser Raman shows that the main composition of fluid inclusions are H2O, some containing methane, propane, acetylene and other hydrocarbons. The pure gas inclusions of ore-forming period are composed of methane, followed by propane, acetylene and other hydrocarbons, which may indicates Mantle-derived fluids.Theδ³⁴S value of sulfur isotope in Sandaowanzi is near 0, i.e., small positive or negative, with the characteristics of mantle sulfur. Hydrogen and oxygen isotope data line in the vicinity of the Meteoric water line, indicating meteoric water's enrollment at the late stage.Sandaowanzi gold deposit occurs in the late Mesozoic extensional tectonic environment. Mineralization is closely related to subalkaline volcanism during regional extension from late Jurassic to early Cretaceous. Regionally, the deposit is controlled by the northeast trending deep fault, and the northwest trending tensional fault system is the ore-hosting structure. Open space filling and crack-sealing in an extensional setting predominates over replacement and other processes.