V.G. KOLOKOL’TSEV, I.V. OSADCHIY, A.N. KHABAROV (VSEGEI)

Ferruginous quartzite formation in the crystalline basement of the Nepa-­Botuoba anteclise, Republic of Sakha (Yakutia)

Mineralogical and petrographic characteristics of hematite­magnetite ore discovered by two oil prospecting wells in the dome of the Nepa­-Botuoba anteclise at a depth of about 1,5 km are discussed for the first time. Geological conditions of two deep-­seated iron deposits are identified; they suggest that the latter probably belong to the Archean­-Proterozoic ferruginous quartzite formation. The important role of this formation in the Early Vendian geomorphogenesis is shown. Results of U-­Pb dating of zircons from granitoids surrounding ferruginous quartzite obtained from three wells are presented. The derived ages corresponding to the crystallization of melts parental for granitoids (2005 ± 12, 1969 ± 13, and 1857 ± 6 Ma) indicate their Early Proterozoic age. On the basis of the obtained materials, probable relationship of the described formation with the Late Archean-­Early Proterozoic Borsalinsky Series, widespread in the Aldan Shield, was suggested.
Keywords: hematite­-magnetite ore, ferruginous quartzite formation, Borsalinsky series, geomorphogenesis, U­-Pb isotope zircon dating, Early Proterozoic, Nepa­-Botuoba anteclise.