GEOCHEMISTRY AND PROVENANCES OF THE PALEOPROTEROZOIC TERRIGENOUS ROCKS OF THE URIK-IYA GRABEN (southern Siberian craton)
Z.L. Motova, T.V. Donskaya, D.P. Gladkochub, A.M. Mazukabzov, E.I. Demonterova
Institute of the Earth’s Crust, Siberian Branch of the Russian Academy of Sciences, ul. Lermontova 128, Irkutsk, 664033, Russia
Keywords: Terrigenous rocks, geochemistry, Nd isotope composition, paleogeodynamic reconstructions, Paleoproterozoic, Urik-Iya graben, Siberian craton
Abstract
We present results of petrographic, geochemical, and isotope-geochemical (Sm-Nd) studies of the Paleoproterozoic terrigenous rocks of the Urik-Iya graben, which formed during three successive stages of extension. We have established that these rocks are both petrogenic (Ingashi and Daldarma formations) and lithogenic (Ermosokha Formation) sediments. It is concluded that the rocks in the lower and, partly, middle parts of the Urik-Iya graben section (Ingashi Formation and Lower Daldarma Subformation) resulted mostly from the disintegration of felsic igneous rocks. The terrigenous rocks in the middle part of the section (Upper Daldarma Subformation) might have formed through the disintegration of both felsic and mafic igneous rocks. The rocks in the upper part of the section (Ermosokha Formation) probably formed from the underlying terrigenous rocks of the Ingashi and Daldarma formations. The Nd model age (2.3-2.5 Ga) estimated for the rocks of the three studied sections points to a predominance of rocks of the Neoarchean and Paleoproterozoic upper continental crust in the provenance.
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