| Abstract: | The knowledge on the early stages of evolution of the Ural-Mongolian Belt (UMB) (Late Neoproterozoic-Cambrian) is a key for
understanding of its evolution in the Paleozoic. Unfortunately, this stage remains poorly studied. The tectonic reconstructions
of the UMB for this time primarily depend on the views on the kinematics and tectonic evolution of numerous sialic massifs
with Precambrian basement in the structure of the Tien Shan, Kazakhstan, Altai, and Mongolia. At present, the concept of the
origin of these massifs is largely based on the lithostratigraphic similarity of the Neoproterozoic and Lower Paleozoic sections
of the Tarim, South China, and Siberian platforms with coeval sections of Precambrian massifs within the UMB. New paleomagnetic
and geochronological data can serve as additional sources of information on the origin and paleotectonic position of the microcontinents.
In this paper, we present new isotopic datings and a new paleomagnetic determination for the Neoproterozoic volcanic rocks
of the Zabhan Formation from the Baydrag microcontinent in central Mongolia. It is established that 805−770 Ma ago (U-Pb LA-MC-ICP-MS
age of zircon) the Baydrag microcontinent was situated at a latitude of 47 ± 14° in the Northern or Southern hemisphere. These
data provide new insights into the possible origin of the Precambrian micro-continents in the UMB. Analysis of paleomagnetic
data and comparison of the age of the basement beneath various plates allow us to state rather confidently that ∼800 Ma ago
the micro-continents of the UMB belonged to one of the North Rodinian plates: Indian, Tarim, or South China; their Australian
origin is less probable. |
