The Teya Polymetamorphic Complex in the Transangarian Yenisei Ridge: An Example of Metamorphic Superimposed Zoning of Low- and Medium-Pressure Facies Series

摘要

Two successive phases of metamorphism can be recognized based on mineralogical and petrolog-ical observations coupled with geothermobarometric estimates for chemical zoning in Fe- and Al-rich metapelites from the Teya crystalline rocks of the Transangarian Yenisei Ridge. The first phase is marked by the formation of low-pressure regional metamorphic complexes of the andalusite-sillimanite type (P= 3.9-5.1 kbar; T= 510-640℃), which were most likely related to the Middle Riphean Grenville events. In the second phase, metapelitic rocks underwent Late Riphean medium-pressure collisional metamorphism of the kyanite—sillimanite type (P= 5.7-7.2 kbar, T= 660-700℃), which resulted locally in an increase in pres?sure in the vicinity of thrusts. These results suggest that medium-pressure kyanite-bearing metapelitic rocks were formed as a result of collision-related metamorphism caused by thrusting of the Siberian cratonal blocks onto the Yenisei Ridge in the vicinity of the Tatarka deep fault.