Concerning the Formation of the Neoproterozoic Central Taimyr Accretionary Belt: Petrogenesis and Geochronology of 900–840 Ma Granites and Rhyolites and Tectonic Paleoreconstructions

Valery Vernikovsky

The structure and tectonic position of the Neoproterozoic Central Taimyr accretionary belt of northwestern Siberia is dominated by the Faddey and Mamont-Shrenk granite-gneiss terranes, ophiolites, island-arc and back-arc volcanic rocks. The Early Neoproterozoic acid igneous rocks of the Central Taimyr accretionary belt are mostly represented by granites, located in two terranes: Mamont-Shrenk and Faddey. The emplacement of the Mamont-Shrenk granites took place between 894–885 Ma, while Faddey granites formed later – 846–838 Ma as follows from zircon U–Pb data (Vernikovsky, 1996; Pease et al., 2001; Vernikovsky, Vernikovskaya, 2001; Kuzmin et al., 2007). These mostly peraluminous and in fewer cases metaluminous granites belong to the calc-alkalic and alkali-calcic magmatic series. The granites display characteristics of fractionated differentiates – transitional between I- and S-type and A-type after the geochemical classification of Whalen et al., (1987). Their isotopic features are related to the mixing of continental crust and mantle sources. We obtained new geochronological and geochemical data for the metarhyolites of Leningradskaya River (Faddey terrane), which are comagmatic to the granites of this region. These metarhyolites form a flow 1–20 meters thick in the upper part of a volcanogenic-sedimentary series and associate with metamorphosed tuffs and basalts. U-Pb ages (SHRIMP II method) of zircons from the metarhyolites vary in the interval of 869–823 Ma. These geochemical and isotopic data can indicate the genesis of these granites in accretionary-collisional tectonic conditions (continent-island arc or island arc-island arc). Paleomagnetic data indicate that the acid volcanic rocks of Leningradskaya River formed at some distance from Siberia, which allows us to reconstruct an accretionary setting between an island arc and the Faddey and Mamont-Shrenk continental terranes in the interval 900–840 Ma during the formation of the Central Taimyr accretionary belt. Our investigations do not contradict our earlier conclusion on the formation of an island arc close to the northern margin of Siberia 960 Ma. Taking into account the measurement error in paleomagnetic determinations the size of the back-arc basin, separating the island arc and the continent could reach 500–1200 km (Vernikovsky et al., 2011).

AAPG Search and Discovery Article #90177©3P Arctic, Polar Petroleum Potential Conference & Exhibition, Stavanger, Norway, October 15-18, 2013