Mineralogical and Chemical Characterization of Zr-REE-Nb Ores from Khalzan Buregtei (Mongolia)—Approaches to More Efficient Extraction of Rare Metals from Alkaline Granitoids

Abstract

Alkaline rocks are worldwide observed as hosts for rare metal (Zr-REE-Nb) minerals. The classification of the ore bearing rock type is challenging due to the fact that textures and mineral assemblage are obscured by post-magmatic alteration. In addition, the alteration causes fine and intricate intergrowth of the ore minerals with associated gangue. Hence, intensive comminution is necessary to liberate the ore minerals, which is one parameter hampering the economical use of this deposit type. This study provides a quantitative mineralogical investigation of the ore bearing rock suite at Khalzan Buregtei as an example of rare metal deposits. R1-R2 multication parameters are shown to be highly appropriate as quantitative mineralogical indicators based on readily available major element datasets to visualize and quantify alteration types of the ore bearing rock suite. The ore minerals were found to be associated with a cluster-forming assemblage of post-magmatic phases. Automated mineralogy was applied to quantify the textural properties of the ore mineral clusters. This finding permits efficient pre-concentration of rare metal ore at coarser particle size fraction, requiring less energy consuming comminution.

Niobium Mineralogy of Pliocene A1-Type Granite of the Carpathian Back-Arc Basin, Central Europe

“…Granite xenoliths fromČamovce correspond to the peraluminous calc-alkali granite, except for one barren xenolith devoid of HFSE-bearing phases (except zircon), which paradoxically projected within the alkali granite field [17]. The assemblage of HFSE-bearing minerals dominated by pyrochlore, fergusonite, samarskite, and columbite is thus typical of alkalic granites [58,59]. Allanite as the main Y-REE carrier in calc-alkali peraluminous granites [60] is missing in the granites fromČamovce, most likely due to a strong water deficiency (<2 wt.%) in the parental magma needed for the crystallization of OH-bearing silicates.…”

REE Minerals as Geochemical Proxies of Late-Tertiary Alkalic Silicate ± Carbonatite Intrusions Beneath Carpathian Back-Arc Basin

“…Pyrochlore, columbite, subordinate Ca-niobate (fersmite/viggezite), Nb-ilmenite, and Nb-rutile also occur in the productive calc-alkalic, peraluminous granite. The AMA is normally diagnostic of peralkaline magmas [45,46]. The relatively Ca-rich granite composition is mirrored in the crystallization of oxycalciopyrochlore and Ca-niobates.…”

Editorial for Special Issue “Applications of SEM Automated Mineralogy: From Ore Deposits over Processing to Secondary Resource Characterization”

“…The characterization of primary ores, and the optimisation of comminution, flotation, mineral concentration and metallurgical processes in the mining industry by generating quantified data, is still the major field of application for SEM-AM. An article by Gronen et al [19] on Zr-REE-Nb ores from alkaline granitoids in Mongolia addresses the problem of post-magmatic alteration causing fine and intricate intergrowth of the ore minerals with associated gangue. This hampers the economic recovery of this deposit type, as intensive comminution is necessary to liberate the ore minerals.…”