CONDITIONS OF FORMATION AND FLUID SOURCES OF YUBILEYNOE VMS DEPOSIT (SOUTHERN URALS): FLUID INCLUSION DATA AND ISOTOPIC AND GEOCHEMICAL STUDY

Abstract

The relevance of the research is related to the problem of determining the PT (P – pressure, Т – temperature) and isotopic and geochemical parameters of formation of massive sulfide ore and seafloor sulfide edifices of Yubileynoe VMS deposit, including various mineral types of paleohydrothermal chimneys, sulfide diffusers and biomorfic ores, in comparison with other VMS deposits of the Southern Urals and modern ocean tubes. The aim of the research is to determine the conditions of formation and isotopic and geochemical composition of ore-bearing fluid formed seafloor sulfide edifices from Yubileynoe VMS deposit. The object of the research is Yubileynoe VMS deposit located in Bashkortostan Republic area in the Southern Urals. Methods. The trace element amounts in calcite were determined using Tescan Vega 3 sbu SEM (Institute of Mineralogy SU FRC MG UB RAS, Miass). Fluid inclusions were analyzed in TMS-600 (Linkam) thermostage equipped with Olympus BX-51 microscope (SUSU, Miass). The gas phases of fluid inclusions in quartz were determined by Raman spectroscopy on a Horiba Lab Ram HR 800 spectrometer (IGM SB RAS, Novosibirsk). The isotopic compositions of carbon (δ13C ‰ VPDB) and oxygen (δ18O ‰ VSMOW) were carried out on a DeltaPlus Advantage mass spectrometer (Thermo Finnigan) coupled to an EA Flash 1112 elemental analyzer with a ConFlo III interface (Institute of Mineralogy SU FRC MG UB RAS, Miass). Results. Homogenization of fluid inclusions in calcite and quartz occurred in the range between 120 and 225 °С, the salinity is 3,3–10,2 wt. % NaCl eq. A significant part of fluid inclusions (Th200 °C were probably formed during relatively low-temperature stages of primary massive sulfide formation. The isotopic composition of δ13C and δ18O of calcite, as well as the calculated values of δ18OH2O and δ13СCO2 of the ore-forming fluid, indicate the mixing of seawater and magmatic fluid.

Keywords

• sulfide paleohydrothermal chimneys
• fluid inclusions
• c and o isotopes
• massive sulfide deposits
• southern urals