Abstract
The publication presents the first results of geochemical, isotope-geochemical (Sm-Nd) and geochronological (U-Pb, LA-ICP-MS) studies on acid volcanic rocks collected in the Bogdanikha River basin of the Amur fragment of the Nora-Sukhotino terrane in the northeast of the South Mongoli–Khingan orogenic belt. In terms of the content of rock-forming components, the studied volcanic rocks correspond to high-silica and high-alumina rhyolites. Elevated contents of alkalis, Ga, Zr, Nb and Y, reduced concentrations of Ba, Sr, Ti, Eu, and mantle values of εNd(t) = +3.0…+3.6 enable the rhyolites from the Bogdanikha river basin to be classified as A2-type rhyolites. The concordant age of the youngest zircon population from the rhyolite, according to geochronological (U-Pb, LA-ICP-MS) studies, is 301 4 Ma which corresponds to the Late Carboniferous. Taking into account the geochemical features of the studied rhyolites and the existing models for the formation of the South Mongolian–Khingan orogenic belt, it is most likely that they formed in a collisional setting as a result of slab detachment.
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