ARKOSE SANDSTONES OF THE KEBEKTA GROUP OF THE UGUI GRABEN (ALDAN SHIELD): AGE, SOURCES, AND DEPOSITION SETTING

Abstract

The paper presents the results of U-Pb (ID-TIMS) and U–Th–Pb (LA-ICP-MS) geochronological studies of baddeleyite from dolerite dikes of the Sulumat Complex and detrital zircon from red arkose sandstones of the Kebekta Group of the Ugui graben, the Aldan Shield. It has been established that the Kebekta Group have an age of 2.011.87 Ga. The sources of the Kebekta Group deposits were the Archean (2.92–2.52 Ga) igneous and metamorphic complexes of the Chara-Olekma geoblock and the zone of its junction with the West Aldan megablock of the Aldan Shield, as well as unidentified on the present erosion level the Paleoproterozoic (ca. 2.01 Ga) complexes. The obtained geochronological data do not contradict the correlation of terrigenous rocks of the Kebekta Group of the Ugui graben and the Kemen Group of the Kodaro-Udokan trough. The deposition of arkose sandstones of the Kebekta Group correlates in age with the glaciations in Australia and Sweden (ca. 1.9–1.8 Ga) associated with the formation of the Columbia/Nuna supercontinent. It also cannot be ruled out that the deposition of the rocks of the Ugui graben was related to the inflow of glacial material into the intracontinental extensional basin from the southern and/or western (in modern coordinates) framing of the Chara-Olekma geoblock at the stage of collapse of the Paleoproterozoic orogen.