Lithia-cesium-tantalum pegmatites of mountain Vaza-Khokh (Northern Caucasus)

Abstract

Relevance. Different types ore mineralization related with granitoids on the Northern Caucasus are described. A granitic pegmatites of Vaza-Khokh did not received elucidating in public press although they contain high concentrate ore mineralization of strategic metals: Li, Cs, Ta, that are in very short supply for mineral-raw materials base of Russia. Consequently, the updating of modern information about the pegmatites of the indicated area is beyond doubt. The aim of the study is to obtain a comprehensive petrological and geochemical characteristic of the Vaza-Khokh granite pegmatites and their typification at the modern level. The objects for research were the bodies of the Vaza-Khokh pegmatites, identified as a potential rare metal ore field. Materials. The materials used in the article were obtained by the author in the process of specialized metallogenic studies carried out in 1989, 2021-2022 on the Vaza-Khokh pegmatite field. Methods. Research methods, in addition to the geological and petrographic description of pegmatites, included obtaining quantitative characteristics of the composition of the rocks. Silicate analysis of rocks for the main components was determined by the X-ray spectral fluorescence method, Co, Ni, Zn, Pb, Li, Sc, Cu – ISP-AES, other elements, including rare earth elements – by the ISP-MS method in the laboratory of the Institute of Mineralogy, Geochemistry and crystal chemistry of rare elements (Moscow). Results and conclusions. As a result of complex studies, new data on the petro-geochemistry of pegmatites were obtained, assigning them to the lithium-cesium-tantalum (LCT) type and identifying several stages of mineralization. In the vertical zoning of a pegmatite field, the most productive rare metal mineralization is the uppermost bodies of pegmatites. For the first time, the following minerals have been described in pegmatites: spodumene, pollucite, pyrrrochlore, zircon, and allanite. The rocks exhibit a tetrad effect of fractionation of M-type rare earth elements. The changing physicochemical conditions of pegmatite fluids led to the preferential enrichment of the latter in ore components under conditions of increasing acidity of the environment.