Bastnäsite nanoparticles in carbonatite-syenite-hosted REE deposit
Description
SEM images of the bastnäsite in the Maoniuping REE deposit, showing that bastnäsite is associated with fluorite (a). High magnification SEM images of the bastnäsite associated with fluorite (b). The SEM-EDS patterns of bastnäsite associated with fluorite, showing that F (c) and Ca (d) are mainly distributed in fluorite and La (e) and Ce (f) are mainly distributed in bastnäsite. Fl: fluorite; Bsa: bastnäsite. HRTEM image of bastnäsite (a), showing that nanoparticle is abundant in bastnäsite. The EDS image (b) and FFT pattern (c) showing small bastnäsite nanoparticles distributed in the outer surface of bastnäsite crystal. The EDS image (d) and FFT pattern (e) showing large nanoparticles distributed in the interior surface of bastnäsite crystal. The EDS image (f) and FFT pattern (g) showing the composition and lattice characteristics of bastnäsite crystal. Schematic illustration of the process of bastnäsite crystal via random attachment. Under external pressure (tectonic stress), growth and realignment of small nanoparticles occurred in the outer surface of bastnäsite crystal. The tectonic stress and the inherent surface stress induce realignment of large nanoparticles to form bastnäsite crystal. Lattice match was neither observed between the small bastnäsite nanoparticle and large bastnäsite nanoparticle nor between large bastnäsite nanoparticle and the main bastnäsite crystal demonstrate the random attachment pathway. Bastnäsite nanoparticles occurred in different bastnäsite mineral samples (M2-M6), indicating that bastnäsite nanoparticles are widely occurred in the Maoniuping REE deposit. Bastnäsite nanoparticles occurred in fluorite (a). The FFT patterns of bastnäsite nanoparticles (b) and fluorite (c). Table S1. EDS results (wt.%) of small bastnäsite nanoparticles Table S2. EDS results (wt.%) of large bastnäsite nanoparticles