| Реферат: | eng: Petrochemical study and U–Pb SIMS (SHRIMP–II) zircon analyses of subalkaline leucogranite of the Khariusikha Massif have been carried out. They have revealed for the first time a rare-metal mineralization. The elevated concentrations of rare elements (wt %) are Nb (0.5–0.7), Ta (0.12–0.16), REEs (0.08–0.24), Y (0.06–0, 1), Zr (2.3–2.6), Hf (0.1–0.12), U (0.05–0.1), and Th (0.08–0.1) and are confined to albitized granites. The main mineral phases concentrating the rare elements, U and Th, are tantalo–niobates: fergusonite, euxenite, U–pyrochlore, tantalite, as well as thorite, monazite, zircon, and sphene. These minerals associate with cassiterite, sulfides, and gold. The simultaneity of the intraplate granitoid magmatism (753 ± 4 Ma) and bimodal rhyolite–basalt volcanism (753 ± 6 Ma) in the neighboring rift structure has been demonstrated. Presumably, the Neoproterozoic rifting and intraplate magmatism relate to the plume activity that caused the supercontinent Rodinia to break up. © 2018, Pleiades Publishing, Ltd.
|