The first finds of paragenetic Th-REE mineralization in precambrian rocks of the Shatak complex (Southern Urals)

Detailed characterization of Th-REE mineralization confined to terrigenous deposits of the Shatak complex is presented. For the first time the veinlet xenotime mineralization, unknown in the scientific literature, as well as diverse unidentified Th-REE compounds of variable composition were described in terrigenous deposits. It was concluded that permanent Th and REE admixtures and rare-earth minerals and thorite, respectively, as well as the occurrence of paragenetic intergrowths of Th and REE minerals of variable composition, are evidence that Th-REE mineralization crystallized as a result of the influence of the fluid phase on the sedimentary substrate upon magmatic melt intrusion into the frame rocks. The superimposed dynamothermal greenschist-facies metamorphism led to decay of metastable Th-REE phases without affecting significantly the redistribution of thorium and rare earth elements.