EXHUMATION OF HIGH-PRESSURE ROCKS OF THE KOKCHETAV MASSIF: FACTS AND MODELS

Abstract

The exhumation of ultrahigh-pressure (UHP) metamorphic units from depths more than 100–120 km is one of the most intriguing questions in modern petrology and geodynamics. We use the diamondiferous Kumdy-Kol domain in the Kokchetav Massif to show that exhumation models should take into consideration initially high uplift velocities (from 20 down to 6 cm/year) and the absence of the deformation of UHP assemblages. The high rate of exhumation are indicated by ion microprobe (SHRIMP) dating of zircons from diamondiferous rocks and supported by the low degree of nitrogen aggregation in metamorphic diamonds.