Characteristics Of The Au-Ag-Te Minerals And Its Ore Genesis Of Sandaowanzi Gold Deposit,Heilongjiang Province

Sandaowanzi gold deposit, located in the northern Daxing’anling in Heilongjiang province, is the only single telluride type gold deposit so far documented in the world, in which90%of gold is hosted in gold-silver telluride minerals. In this paper, we made a detailed study on the characteristics of the Au-Ag-Te minerals, combined with the changes of physicochemical conditions of ore-forming fluids and the research of helium and argon isotopes studies of mineral inclusions, we made a discussion on the genesis of the deposit.(1) A new crystalline Au2Te was disvovered. The Compound Au2Te was found in auriferous quartz in the shape of round sphere, surrounded by calaverite "wrapper".It has weak anisotropy according to the optical microscope and boundary with surrounding minerals is clear. Its composition is stable according to the electron probe and has stable strong peaks of X-ray diffraction analysis. Au2Te is a new Au-Te crystalline compound, probable a new kind of mineral.(2) Primary minerals have obviously zonation in space. The silver minerals enriched in upper of the deposit except for a small amount of sulfide and native gold, while the lead minerals enriched in the bottom of the deposit except for some tellurides The tellurides are abundant in the h130m level.(3) Eight telluride minerals were observed and intergrowth textures are abundant among them, the texture can Implications for ore-forming environment. The intergrowth textures of sylvanite-hosting hessite crystals and hessite-hosting petzite crystals imply that the veined tellurides formed at150-220℃according to the phase-transformation temperature derived from synthesis experiments of tellurides(4) According to the ore-forming temperature and the changes of mineral assemblages combined with the phase diagram; we inferred The early stage disseminated tellurides formed at logf(Te2) range ranging from-13.6to-7.8,log f(S2) from-11.7to-7.6, whereas the late stage veined tellurides formed at log f(Th2) ranging from-11.2to-9.7and log f(S2) from-16.8to-12.2. The low sulfur fugacity, High tellurium fugacity and the tellurium fugacity increased firstly and then decreaed from the upper to the bottom of the ore body in space is in accordance with the characteristics of the distribution of minerals of the deposit.(5) Helium and argon isotope studies of fluid inclusions indicate that mantle fluid were involved in the ore-forming fluid in the stage of tellurides. the ratio3He/4He is 0.01-0.03Ra in the stage of pyrite-quartz, while it is0.08-1.04Ra in the stage of tellurides, which indicated that large quantities of mantle fluid were involved in the ore-forming fluid in the stage of tellurides.