The Neoproterozoic Age of the Crystalline Basement of Bogdoingol Block of the Dzabkhan Terrane, the Central Asian Orogenic Belt
The Dzabkhan terrane was considered as a fragment of an ancient craton in the structure of the Central Asian orogenic belt, which is the basement of the carbonate strata of the Tsaganolom Formation of the Ediacaran shelf cover. They were supposed to record regional unconformity between Early and Late Precambrian formations. The occurrence of the Tsaganolom Formation on the high-temperature metamorphic rocks is determined only in Bogdoingol block of the eastern Dzabkhan terrane, where the dolomites with disconformity overlap migmatized gneisses and granitoids intruding them; the latter were previously dated at 717 ± 5 Ma. Synmetamorphic quartz diorites with a zircon age of 847 ± 3 Ma (U–Pb, ID-TIMS) were found in gneisses and migmatites of the Bogdoingol block. The values of t<sub>Nd(DM-2st)</sub> are equal to 1.97 Ga in gneiss and 2.0 Ga in quartz diorites.