Magmatism of the Khambin Graben and Early History of the Late Mesozoic Rift System Formation in the Western Transbaikal Region

摘要

The western Transbaikal region was repeatedly subjected to rifting during the Mesozoic. The Early Mesozoic was marked by the formation of a system of gra-bens filled in with Late Triassic-Early Jurassic bimodal volcanic sequences of the Tsagan-Khurtei Group and Kunalei Complex, which is traced by massifs of alkalic granites. In the Late Mesozoic, a new rift system, generally conformable with the previous one, appeared and began to develop until the Late Cenozoic. Therefore, the grabens and horsts of the rift system are readily traceable in the present-day topography. The Late Mesozoic epoch commenced with the formation of the bimodal basalt-trachybasaltic andesite-trachy-dacite-trachyrhyolite-comendite volcanic association of the Ichetui Formation.