Neoproterozoic-middle Paleozoic tectono-magmatic evolution of the Gorny Altai terrane, northwest of the Central Asian Orogenic Belt: Constraints from detrital zircon U-Pb and Hf-isotope studies

The absence of middle Ordovician to early Devonian detrital zircons possibly implies that the area changed to a passive margin in the middle Ordovician. Of special significance are the 2431-772 Ma zircons in the early Devonian sample, which are quite comparable to the Precambrian detrital zircons from the Altai-Mongolian terrane (AM) but distinct from those from the Siberian continent. This indicates that the AM is a plausible source for the 2431-772 Ma zircons. Our data therefore imply that the GA possibly amalgamated with the AM before the early Devonian rather than in the late Devonian to early Carboniferous as previously suggested.