Abstract

The Ol’khon region represents a fragment of the West Baikal collision belt that resulted from Early Caledonian accretionary‐collisional processes related to the closure of the Paleo-Asian ocean in the southern margin (in present-day coordinates) of the Siberian Craton [1‐3]. This communication is dedicated to analysis of the internal structure and age of protoliths from this region based on U‐Pb dating and the Sm‐Md isotopic composition of igneous complexes. The U‐Pb (SHRIMP-II) age of rocks was measured at the Center of Isotopic Studies (VSEGEI, St. Petersburg) using the technique described in [4]. The Sm‐Nd isotope composition of bulk rock samples was determined by the standard method [5] at the Laboratory of Isotope Geochronology and Geochemistry (Geological Institute, Kola Scientific Center, Russian Academy of Sciences, Apatity). Figures 1 and 2 demonstrate experimental results obtained for two periods (500‐485 and 475‐465 Ma ago) (Figs. 1, 2), which reflect the scale and spatial distribution of synmetamorphic and intrusive igneous rocks in the southwestern part of the Ol’khon region. 1

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