Mineral Characteristics and the Mineralization of Leptynite-Type Nb–Ta Ore Deposit in the Western Qilian Orogenic Belt

A large Nb–Ta ore deposit was found in the Yushishan leptynite west Qilian Orogenic Belt (QOB). Based on a field geological survey and using Mineral Liberation Analyser (MLA, including scanning electron microscopy (SEM) energy-dispersive spectrometer (EDS)) methods, eight Nb minerals (fergusonite, polycrase, columbite, Nb-rutile, aeschynite, pyrochlore, microlite, ilmenorutile) were to occur leptynite. This accounted for approximately 69% of Nb, with fergusonite, columbite being dominant phases. The other 17.90% as minor element dispersed titanium magnetite–maghemite, another 13.00% gangue minerals. are formed mainly by two metallogenesis stages. first stage is magmatic genesis form four minerals, euhedral-subhedral which crystallized within or between primary such quartz feldspar. Late alteration phenomena locally observed. second hydrothermal anhedral fissures wall rocks irregular veins lump assemblages. Meanwhile, they closely associated metasomatic chlorite, albite, secondary quartz. Furthermore, direct metasomatism among different also at local scale. percentage these mineral mineralization types equal, reflects main mineralizing periods. occurred Neoproterozoic Era (834–790 Ma). Magmatism this period produced early niobium zircon. initial enrichment Ta, rare metals during stage. Caledonian (490–455 Large-scale intense tectonic–magmatic thermal events western part QOB due plate subduction convergence (510–450 Hydrothermal activity aeschynite. Moreover, metal elements Nb-bearing activated migrated short distances, forming situ Nb–Ta-rich deposits.