Evolution of mineral forms of rare element accumulation in ore-bearing granites and metasomatites of Verkhneurmiysk ore cluster (Priamur region)

Abstract

It has been attempted to expand existing understanding of accessory mineralization evolution of rare metal-granite series at post-magmatic stage of their development and formation of associated hydrothermal deposits. Composition and distribution of rare elements of Verkhneurmiysk ore cluster have been examined from the position of mineralogy: the study focused on accessory and ore minerals Sn, W, Nb, Ta, Bi, Y, rare earth elements in rare metal Li-F granites and associated metasomatites. It has been discovered that accessory magmatic and hydrothermal mineral complexes share the same geochemical features, are formed under the leading role of abovementioned elements and consistently follow each other over time. It has been traced how mineral forms of accumulation of Sn, W, Nb, Ta, Y and rare earth elements evolve in the processes of magmatic crystallization and post-magmatic metasomatism in the time series: rare metal granites → zwitters → tourmalinites → chloritites. Mineral rocks of each stage were noted to inherit mineralogical and geochemical distinctions from the rocks of the previous stage. A significant number of minerals, forming in the course of two-three stages, have been discovered, as well as omnipresent magmagene-hydrothermal minerals. For a number of accessory minerals of rare metal granites post-magmatic generations have been identified. Special diversity among accessories of rare metal granites and zwitters was observed in tungsten, tin and bismuth minerals. Composition of Verkhneurmiysk ore cluster mineralization is in many aspects similar to the one of metasomatic accessory minerals of rare metal granites. Tungsten-tin deposits of Verkhneurmiysk ore cluster are polyformational and combine mineralogical features of cassiterite-quartz and cassiterite-silicate formations. Evolution of mineral forms of the key rare elements (Sn, W, Bi, Nb, Ta, rare earth elements) points to a genetic link between tungsten-tin mineralization of zwittertourmalinite formation and rare metal Li-F granites of the region. The evidence of that is a specific genetic category of accessory materials, formed as a result of pseudomorphism of protominerals, – transformational minerals or metasomatic accessory minerals. The list of metasomatic accessories includes exactly those minerals which are considered indicators of ore generation capacity of Far Eastern leucogranites: cassiterite, wolframite, scheelite, a number of sulphides. Similar qualitative composition of magmatic and post-magmatic minerals demonstrates metallogenic specialization of parent granite magma. Predicted mineragenic significance of research in the field of mineral forms evolution of rare elements accumulation in ore-bearing granites and metasomatites is associated with possibilities to assess metallogenic specialization of parent granite magma. Understanding of accessory paragenesis evolution should serve as a base for exploration geo-technologies in the Far East metallogenic province.