Tin–rare-earth element greisens of the Solnechnoe cassiterite–silicate deposit, Russian Far East

Resumo

The paper considers for the first time the morphology, composition, and conditions of formation of the greisens of the Solnechnoe deposit (Komsomol’sk ore district), a typical cassiterite–silicate assemblage. The greisens are localized in the root parts of the deposit and represent a system of veins and veinlets formed in the contraction fractures of the metasomatically altered roof of the monzogranite intrusion (age of 94–92 Ma). The cassiterite–chlorite–carbonate–muscovite–quartz composition of the greisens with admixture of topaz, fluorite, and apatite reflects the composition of the monzogranites. The greisens are close in age (85.3 Ma on muscovite) to the granitic aplites (80–85 Ma on the whole-rock and biotite) of the final phase of the intrusive magmatism. The fluid regime of their formation differs from that of the economic ores in higher temperature, pressure, and salinity. One distinguishing feature of the greisens is elevated contents of LREE, U, and Th, which are incorporated in the REE fluorcarbonates, thorite, and uranothorite crystallizing together with cassiterite.