Age of the host granites, mineral composition, and formation conditions of quartz-molybdenite mineralization at the Zharchikhinskoye deposit (Western Transbaikalia)

Abstract

This article considers the results of a study of the mineral composition of the main productive molybdenite-quartz association of the Zharchikhinskoye molybdenum deposit and presents new data on the crystallization time of the granites hosting the ore mineralization. Two U-Pb isotope dates
(LA-ICP-MS method) were obtained for zircons from the brecciated and massive granites: 282±3 Ma and 281±3 Ma. The main ore mineral is molybdenite; secondary molybdenum minerals wulfenite, powellite, and ferrimolybdite form under supergene conditions. It was established that the ores of the deposit are characterized by the absence of tungsten minerals and the presence of non-commercial beryllium, polysulfide, and aluminum fluoride mineralization. Based on the study of fluid inclusions in quartz and fluorite, homogenization temperatures were established in the range from 245 to 402 °C. Taking into account the pressure data of 1255–1372 bar, the range of calculated temperatures for the FI capture is 538–554 °C. The ore-forming solutions had relatively low salinity, on the order of ~5.7–11.7 wt. % NaCl equiv. The main salt components are represented by iron and magnesium chlorides.