ISSN 00168521, Geotectonics, 2011, Vol. 45, No. 1, pp. 51–70. © Pleiades Publishing, Inc., 2011. Original Russian Text © N.M. Levashova, A.S. Gibsher, J.G. Meert, 2011, published in Geotektonika, 2011, Vol. 45, No. 1, pp. 58–79. Precambrian Microcontinents of the Ural–Mongolian Belt: New Paleomagnetic and Geochronological Data N. M. Levashovaa, A. S. Gibsherb, and J. G. Meertc a Geological Institute, Russian Academy of Sciences, Pyzhevskii per. 7, Moscow, 119017 Russia email:
[email protected] b Institute of Geology and Mineralogy, Siberian Branch, Russian Academy of Sciences, pr. Akad. Koptyuga 3, Novosibirsk, 630090 Russia c Department of Geological Sciences, University of Florida, 274 Williamson Hall, Gainesville, FL, 32611 USA Received May 14, 2009 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 sec tions 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.