ISOTOPIC PROVINCES AND EVOLUTION STAGES OF THE PRECAMBRIAN CRUST AT THE SOUTHWESTERN MARGIN OF THE SIBERIAN CRATON AND ITS FOLDED FRAMING

Abstract

Highly metamorphosed rock associations of the Kan, Derba, and Arzybei blocks in the Central Asian Foldbelt are usually correlated with Early Precambrian basement complexes of the southwestern margin of the Siberian Craton. The tectonic blocks are often considered fragments of its crystalline basement. Recent precision datings revealed that the blocks include Paleoproterozoic–Early Paleozoic igneous rocks and granitoids. In order to find isotopic signs of the Early Precambrian (primarily, Archean) crust in the folded framing of the Siberian Craton and to correlate rock complexes of Precambrian terranes with rock associations of the exposed craton basement, we carried out the first systematic investigation of the Nd isotopic composition of metamagmatic and metasedimentary rocks. The results obtained made it possible to identify isotopic provinces and major stages of crust-forming events at the Siberian Craton margin.