Geochronology of the metamorphic rocks in the Kurai accretionary prism (south-eastern Gorny Altai)

Abstract

The paper provides a review of the published and new geological and geochronological data on the metamorphic rocks in the Kurai accretionary prism, considering the evolution of the Kuznetsk-Altai island-arc paleosubduction channel of the Siberian continent. The following two stages are distinguished by 40Ar/39Ar and U/Pb dating: (1) 636-619 Ma and earlier: sinking of ophiolites into the subduction zone; (2) 604-585 Ma: sinking of the large bodies of oceanic uplifts into the subduction zone. These processes led to the exhumation of the high-pressure rocks and the hot Chagan-Uzun peridotites. The dynamo-thermal effect of the latter on the basalts is reflected in the inverted metamorphic zoning and the occurrence of garnet amphibolites and plagiogranite migmatites. It is probable that the paleo-seamounts collided with the island arc during the Vendian-Early Cambrian. The data reviewed in this paper give evidence of an active margin of the West Pacific type in the western Altai-Sayan folded region in the Vendian-Cambrian.