COMPOSITION AND TECTONIC FORMATION HISTORY OF OPHIOLITES IN THE TATARKA-ISHIMBA SUTURE ZONE OF THE YENISEI RIDGE
E.A. Bogdanov1,2, N.Yu. Matushkin1,2, A.E. Vernikovskaya1,2, A.V. Travin3
1Novosibirsk State University, Novosibirsk, Russia
2Trofimuk Institute of Petroleum Geology and Geophysics SB RAS, Novosibirsk, Russia
3V.S. Sobolev Institute of Geology and Mineralogy SB RAS, Novosibirsk, Russia
Keywords: Ophiolite, 40Ar/39Ar geochronological data, accretion, late Mesoproterozoic, Neoproterozoic, oblique collision, Tatarka-Ishimba suture zone, Yenisei Ridge
Abstract
We report results of geostructural, mineralogical, petrographic, geochemical and geochronological (40Ar/39Ar) investigations of ophiolites in the northern and southeastern fragments of the Tatarka-Ishimba suture zone of the Yenisei Ridge combined into the Rybnyi-Panimba belt. They consist of massive and pillow-lava metabasalt, massive and layered metagabbro and metadolerite, and represent fragments of the upper part of the oceanic crust. They formed in a mid-ocean ridge or marginal sea setting from depleted mantle sources corresponding to components of N-MORB and E-MORB geochemical types. We propose a model for the tectonic history of emplacement of ophiolites on the margin of the Siberian craton in the Neoproterozoic time. At the Meso–Neoproterozoic boundary (Stenian–Tonian), 1051–916 Ma, the thrust structure was formed and the oceanic crust fragments (ophiolites) were accreted to the passive margin of the Central Angara Terrane (microcontinent). The subsequent convergence and collision of this microcontinent with the Siberian craton (786–749 Ma) caused the formation of strike-slip/thrust deformation in the rocks of the Tatarka-Ishimba suture zone including ophiolites. In the Cryogenian (708–700 Ma), strike-slip and reverse fault deformations occurred in these rocks due to a new episode of tectonic activity caused by the transition between convergent settings – end of the collision and start of the active continental margin.
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