Late Riphean age of the crystalline basement of the carbonate cover of the Dzabkhan microcontinent

Abstract

The Dzabkhan microcontinent was earlier considered as a fragment of an ancient craton in the structure of the Central Asian Orogenic Belt. Deposits of the Tsagaan Oloom Formation were included in the shelf zone, under the assumption that they were related to the regional unconformity between the Early-Late Precambrian crystal formations. The carbonate sequence of the Tsagaan Oloom Formation overlaps crystal line rocks only in the eastern part of the Dzabkhan microcontinent, where dolomites lie unconformably on high grade metamorphic rocks intruded by granitoids of the Bogdyngol massif. The latter were included in the composition of both the Early Precambrian basement and the Middle Riphean intrusive complex. We have determined the U Pb zircon age of these granitoids at 717 ± 5 Ma and the Nd model ages of granitoids and gneisses of the basement of the Tsagaan Oloom Formation at 2.0-1.9 Ga at ε Nd = -10.0…-6.6. Recent geochronological and Nd and Pb Pb isotopic and geochemical data indicate that intrusive and high grade metamorphic complexes are absent in the crystalline basement of the Dzabkhan microcontinent, similar to those in ancient cratons. One can assume that the Late Riphean carbonate cover (Tsagaan Oloom Formation) deposited on the Late Precambrian continental block.

Lower Permian basaltic agglomerate from the Tsengel River valley, Mongolian Altai

“…The studied sample forms a massive part of fluidal agglomerate lava and it is classified as pyroxene basalt composed of glassy matrix with pyroxene phenocrysts. The chemical composition of this high-Mg basalt does not correspond to the alkaline character of Permian intraplate volcanism described further to the east in the Khar Argalantyn area by Buriánek et al (2012) or on the NE slopes of the Khantaishir ridge by Kozakov et al (2015). Dominating concordia cluster with two age peaks corresponding to 288 Ma resp.…”

Zircon ages and Nd–Hf isotopes in UHT granulites of the Ider Complex: A cratonic terrane within the Central Asian Orogenic Belt in NW Mongolia

“…In contrast to the northwestern part of the Dzabkhan block, zircon ages and whole-rock Nd isotopic data for the southern part indicate extensive early Neoproterozoic crustal reworking [Kozakov et al, 2015;Bold et al, 2016].…”

An Active Neoproterozoic Continental Margin of the Zavkhan Microcontinent (Mongolia): Isotopic-Geochronological Evidence

“…в недавних работах [Kozakov et al, 2014[Kozakov et al, , 2015[Kozakov et al, , 2020[Kozakov et al, , 2021Kovach et al, 2019Kovach et al, , 2021Bold et al, 2016aBold et al, , 2016b. Согласно цитированным работам Дзабханский блок представляет собой неопротерозойский композитный террейн, фундамент которого сложен преимущественно породами амальгамированных в позднем неопротерозое островодужных и окраинно-континентальных комплексов, большей частью в разной степени метаморфизованных.…”