A Combined EMPA and LA-ICP-MS Study of Muscovite from Pegmatites in the Chinese Altai, NW China: Implications for Tracing Rare-Element Mineralization Type and Ore-Forming Process

The mineralogical studies of rare-element (REL) pegmatites are important for unraveling the ore-forming process and evaluating REL mineralization potential. Chinese Altai orogenic belt hosting more than 100,000 pegmatite dykes is famous rare-metal resources worldwide diverse types. In this paper, we present results EMPA LA-ICP-MS muscovite from typical Altai. studied Li-Be-Nb-Ta, Li-Nb-Ta, Nb-Ta, Be-Nb-Ta, Be barren pegmatites. Li+ accompanied with Fe, Mg Mn substitute Al3+ at octahedral site in pegmatites, substitution Rb by Cs interlayer space identified P B contents increase evolution degree lenses Nb-Ta produced late fluid-rich stage high fluxes (P B). enrichment HFSE indicates a Nb-Ta-Sn-W rich magma Be-Nb-Ta pegmatite. From pegmatite, beryl-bearing zone, to spodumene-bearing degrees pegmatite-forming magmas progressively increase. Altai, possible indicators types include (ca. 400–600 ppm, pegmatite; ca. 1200–4000 >4500 Li pegmatite), 5–50 100–500 >300 pegmatite) Ge (<3 4–6 6–12 coupled Ta, (both <10 FeO 3–4 wt%, 1–2.5 pegmatite). plots Nb/Ta vs. K/Rb proposed discriminate barren, Be- Nb-Ta-(Li-Be-Rb-Cs) Li, Be, Rb, F concentrations forming liquid evaluated based on trace element compositions muscovite. lower beryl saturation value indicate that both highly evolved low temperature emplacement contribute formation. liquids saturated spodumene have large variations possibly related metastable state unsaturation–supersaturation or heterogeneous distribution lithium system.