ISOTOPIC PROVINCES AND FORMATION STAGES OF THE CONTINENTAL CRUST IN THE BAIKAL-MUYA BELT: Sm-Nd ISOTOPIC EVIDENCE FOR GRANITIC AND SILICIC VOLCANIC ROCKS

Abstract

Recent geological, geochronological, geochemical, and isotopic data made it possible to establish the main stages of the formation and evolution of the oceanic and continental crusts of the Central Asian Foldbelt (CAFB), to outline isotopic provinces, and to elaborate geodynamic models of the crust formation related to the origin and breakdown of Rodinia and Gondwana supercontinents. Nevertheless, many problems related to the earliest, Late Riphean–Vendian periods of the geological history remain a matter of debate due to the lack of isotopic geochronological and geochemical data. The Baikal fold region as a tectonotype of the Baikalides is the key domain for solving these problems. This communication is a synthesis of the original geochronological and Nd isotopic data on granitic rocks and silicic volcanics of the Baikal–Muya Belt (BMB) of the Baikal fold region. Isotopic provinces and formation stages of the crust are outlined on the basis of these data.