Mineralogical and geochemical characteristics of scheelite from the Vostok-2 au-bi-cu-w skarn deposit (Primorsky krai)

The scheelite (CaWO4) is main ore mineral from the Vostok-2 reduced skarn type deposit, which located in Primorie region (Russia) and connected with the Sikhote-Alin central fault. By mineral composition and geochemical characteristics ore rocks were divided into two most common types: skarns and quartz-veins. This study presented results of complex (mineragraphy, cathodoluminescence (CL), electron-probe microanalysis (EPMA), laser-ablation inductively-connected plasma mass-spectrometry (LA-ICP-MS)) researching of scheelite. These parameters for scheelite like inner structure, illumination character in CL and UV, contents of micro- and macroimpurities, Eu/Eu* value, REE spectral shape are crucial indicators of the conditions of mineralization. These signs allowed to identify different mechanism of REE entering in scheelite from skarns and quartz-veins (3Ca2+ ↔ 2REE3+ + □ and Ca2+ + W6+ ↔ REE3+ + Nb5+ where □ is vacancy in the Ca site). By distribution specific of REE three types of scheelite were identified and their temporal relationships were established. Because scheelite inherits REE characteristics from mineral-forming environment some conclusions were shown: evolution of the ore-forming fluid, pulsation nature of the substance’s intake and its single source, and reductive conditions of mineralization were proved for the deposit as a whole.