TUVA-MONGOLIA TERRANE (IN THE CONTEXT OF MICROCONTINENTS IN THE PALEOASIAN OCEAN)

Abstract

The Tuva-Mongolia block has become commonly recognized and is often invoked in palisnpastic reconstructions as a separate terrane. However, its position has been doubted recently despite abundant geological evidence providing new details of its origin and evolution. We analyze the available geological data to reconsider the structure and outlines of the Tuva-Mongolia terrane and justify its existence as an independent tectonic unit in the Central Asian belt of Paleozoids. The terrane has a pre-Vendian accretionary basement overlain by Vendian-Cambrian carbonates. In Vendian-Cambrian time it was a microcontinent in the Paleoasian ocean, and platform carbonate deposition within its limits was synchronous with the formation of ophiolites and island arcs in the surrounding oceanic space. Paleozoic plutonism and metamorphism record the Ordovician collision rather than the preorogenic tectonic history of the terrane.