STRUCTURAL-METAMORPHIC EVOLUTION OF THE SOUTHERN YENISEY RANGE OF EASTERN SIBERIA: IMPLICATIONS FOR THE EMPLACEMENT OF THE KANSKIY GRANULITE COMPLEX

Abstract

The Southern Yenisey Range of Eastern Siberia consists of the granulite facies Kanskiy Complex bordered in the west by the lower-grade Yeniseyskiy and Yukseevskiy Complexes. Three deformational events were recognized in each of the three complexes along the Yenisey River cross-section: a D1 fabric forming event, a D2 shear and folding event, and a D3 shear event. Thrust kinematics across the Southern Yenisey Range suggest that during the D2 event the Kanskiy Complex was thrusted along a regional ductile shear zone onto the lower-grade complexes. This resulted in shearing and folding as well as the development of a dynamic metamorphic zonation. In the low-grade greenstone belt part of the cross section (Yukseevskiy complex) D2 shearing is associated with peak prograde (T similar to 660 degrees C and P similar to 5.8 kbar) metamorphism. The retrograde P-T path of the Yukseevskiy Complex coincides with minimum Tof the near-isobaric cooling P-T paths for the adjacent granulites of the Kanskiy Complex (Perchuk et al., 1989). The metamorphism can therefore be attributed to deformation and heat transfer caused by exhumation of the Kanskiy Complex in the time period 2000-1800 Ma which also defines the most significant tectono-thermal event in the Southern Yenisey Range. The tectono-metamorphic pattern and evolution of the low- to high-grade metamorphic complexes of the Southern Yenisey Range is very similar to that described for the similar to 2600 Ma Limpopo Complex of Southern Africa and the similar to 1900 Ma Lapland Complex of the Kola Peninsula. Similar geodynamic processes were therefore possibly responsible for the formation of these high-grade terrains suggesting that their formation is linked to a general geodynamic model.