Rare Arsenates of REEs and Y in Ores of the Verkhnee Greisen Deposit within the Khingan–Olonoiskii District (Primorye, Russia).

In the Sn–W greisen deposits of the Karadub ore field, rare arsenates of REEs chernovite-(Y) and gasparite-(Ce), associated with topaz, fluorite, fluocerite, and bastnaesite, have been identified. They replace early xenotime-(Y) and monazite-(Ce). Chernovite-(Y) and gasparite-(Ce) from Sn–W greisens differ in their chemical composition from the same minerals previously described elsewhere. Chernovite-(Y) differs in the minimum content of Y with only 0.47 to 0.26 atoms in the formula (a.p.f.) and a relatively high content of light REEs of 0.111–0.254 (a.p.f.). Gasparite-(Ce) has a high Nd content of 0.28 (a.p.f.). REE arsenates were formed by substituting xenotime (Y), monazite (Ce), and REE-bearing fluorite under strongly oxidizing conditions. [ABSTRACT FROM AUTHOR]