Mechanisms of formation of deep basins on continental crust in the Verkhoyansk fold belt; miogeosynclines and cratonic basins

Abstract

The Verkhoyansk fold belt is a wide, folded area in Northeastern Asia. A large sedimentary basin, 10–15 km deep, was formed there by a slow subsidence of continental crust during ~ 1000 Ma in the Late Proterozoic-Middle Paleozoic. There are no deformations in the sedimentary cover that could indicate significant lithospheric stretching or shortening during this slow subsidence. A number of deep basins (5–15 km) of the same type exist or existed in other areas. They can be called “cratonic basins”. A slow gabbro-eclogite transformation in the lowermost crust that occurred in a thick cratonic lithosphere can be suggested as a mechanism for their formation. Several deep-water basins were formed in the Verkhoyansk fold belt by rapid subsidence of continental crust during ~1–5 Ma in the Late Paleozoic and Early Mesozoic. The subsidence occurred without significant stretching or thrust loading. The basins formed were strongly folded in the Late Mesozoic under the convergent plate motions. There were many basins of the same type in the other fold belts. Among deep basins on continental crust only those produced by rapid subsidence were intensely folded. They can be called “miogeosynclines”. Rapid gabbro-eclogite transformation with the destruction of the basaltic layer may be suggested as the mechanism of their formation. This probably occurred under upwelling of hydrous anomalous mantle to the base of the crust.