COMPOSITION AND SOURCES OF DEVONIAN VOLCANISM IN THE VILYUI RIFT

Abstract

Riftogenic processes were widespread in the Middle Paleozoic history of the Earth. They produced several rift systems and regions in the Siberian Craton. The Vilyui rift zone (VRZ) or paleorift (~800 km long and 450 km wide) occupies a special place among them. The VRZ represents a blind offshoot of a three-member rift system. The other two offshoots of this system split the Siberian paleocontinent in the Middle Paleozoic and defined its present-day boundary. The paleorift has a complex structure with dike belts extending along its walls. The internal structure of the paleorift represents a system of longitudinal depressions separated by uplifts. The depressions are filled with Upper Devonian–Lower Carboniferous sedimentary, volcanic, and volcanosedimentary rocks. The northwestern wall of the rift incorporates the Vilyui–Markha mafic dike belt with the Mirnin and Nakyn diamondiferous kimberlite fields.