Jurassic-cretaseous high-potassic volcanism of tne Nerchinsk depression in Eastern Transbaikalia and its geodynamic nature

The geochronological, geochemical and Sr-Nd isotopic features of Late Mesozoic volcanic rocks associated with the development of the Nerchinsk depression in Eastern Transbaikalia are presented. Its structure involves the sequences of high-potassium subalkaline volcanic rocks containing of 55 to 73 wt.% SiO2.40Ar/39Ar isotope dating of bulk rock samples was performed. 40Ar/39Ar dating results from high-K basaltic andesite gives value of 150.8±1.8 Ma and from latite is 131.0±1.6 Ma. Volcanic rocks are characterized by depletion of hydrophobic Ti, Nb and Ta, slightly negative εNd(T) values, but increased in εSr(T), that probably indicates contamination processes of primary melts by crust component. In terms of their geological and geochemical characteristics, the volcanic rocks of the Nerchinsk depression belong to the shoshonite-latite series of the rear part of the Greater Khingan volcanic region, which formed in the subduction setting of a continental active margin.