Scheelite of the Bystrinsky skarn-porphyry Cu-Au-Fe deposit (Eastern Transbaikalia, Russia): genetic implications

Abstract

The first results of the study (methods of mineragraphy, cathodoluminescence (CL), electron-probe microanalysis (EPMA) and laser-ablation inductively-coupled plasma-mass spectrometry (LA-ICPMS)) of scheelite from quartz-molybdenite and quartz-carbonate-sulfide vein-veinlet (porphyry type) are considered, as well as the magnetite-sulfide massive, veinlets and disseminated (skarn type) mineralization of the skarn-porphyry Cu-Au-Fe deposit of Bystrinskoye (East Transbaikalia) one of the largest gold-copper porphyry ore-fields in Russia. It has been established that scheelite, being not the main mineral of the deposit ores, is found almost everywhere, which makes it possible to identify its key features reflecting the specific features of the genesis, both of different types of mineralization and the deposit as a whole. It is shown that scheelite from different types of ore mineralization has clearly determined individual characteristics, differing in prevalence, ensembles of associated minerals, color of CL and fluorescence in the UV-light, composition and concentrations of macro- and microelements, as well as the nature of REE-spectra. These distinctive features testify to a significant difference in the conditions for the formation of the studied ore types and reveal the dependence on the physicochemical and compositional parameters of the mineral-forming medium, which makes it possible to consider scheelite as a fundamentally important genetic indicator of the evolution of mineral formation patterns. Concentrations of Mo in scheelite, the type and form of REE-spectra, which are generally, determined both by the inheritance of the mineral-forming fluid chemistry and the peculiarities of isomorphic occurrence of REE in the structure of the mineral, and variations in the redox properties of the mineral-forming fluid, are of key importance.