Rare-Earth Mineralization in Terrigenous Rocks of the Shatak Complex (Southern Urals): Species Diversity and Features of Chemical Composition

The study of terrigenous rocks of the Shatak Complex, which includes rocks of the Kuz”elga and Karan subformations (Mashak Formation, Upper Riphean) revealed numerous rare-earth minerals: allanite-(Ce), monazite-(Se), monazite-(Nd), xenotime-(Y), REE-bearing epidote, and unidentified compounds. It has been established that the detrital zircon plays the role of a selective concentrator of Y, HREE, and Th during the terrigenous rock metamorphism. The comparative analysis showed that rare-earth minerals, such as monazite-(Ce) and xenotime-(Y), in the Shatak Complex differ significantly (in terms of chemical composition) from counterparts in other complexes located on the western slope of the Southern Urals by the presence of Gd in monazite, and LREE (Ce, Nd, Sm) in xenotime. In the case of similar thermobaric parameters of rock metamorphism characterizing the alteration degree of lithostructural complexes in the Southern Urals, the chemistry of mineral formation environment is among the main factors governing the compositional features of rare-earth minerals.