Stages and regularities in the development of Late Paleozoic anorogenic volcanism in the southern Mongolia Hercynides

Abstract

811 An important role in the formation of the Central Asia Hercynides belonged to postaccretionary pro� cesses, both orogenic and anaorogenic. The accre� tionary structures proper were formed in the Middle Paleozoic in response to the convergence between the Siberian and Tarim paleocontinents. This conver� gence was responsible for the gradual closure of the intervenient PaleoAsian ocean branch (1-3) and was accompanied by the convergence at its boundaries, which resulted locally in the formation of accretionary terranes, island arcs, and active margins along conti� nental blocks. The most significant consequence of these processes was accretion of juvenile crustal blocks to the margin of the Siberian continent. This led to the formation of the Hercynides folded domain, which is traceable in the presentday structure from eastern Kazakhstan through northwestern China to southern and southeastern Mongolia (2). After the formation of this folded domain, its struc� tures were involved in a long period of their transfor� mation by postaccretionary magmatism that lasted from the Early Carboniferous until the Early Permian. Two stages are distinguishable in its history. The early stage was related to the formation of the active margin