Affiliation:
1. Vinogradov Institute of Geochemistry, Siberian Branch of the Russian Academy of Sciences, ul. Favorskogo 1a, Irkutsk, 664033, Russia
Abstract
Abstract
—Cenozoic alkali basaltoids are developed in southern Transbaikalia (Dauria–Khentei Ridge). They are represented by thin flows and sheets. Unlike the volcanic fields of the South Baikal Volcanic Region (SBVR), the investigated fields are not associated with rifting. Volcanics from the flow of the Zharnichikha River were studied. Compositionally, they belong to basanites. For the first time, the mineral compositions of the volcanics have been determined. In their geochemical parameters, the basanites correspond to basic volcanics of oceanic islands. The P–T parameters of the equilibrium crystallization of olivine and clinopyroxene phenocrysts have been determined. For the calculated parental melt, the temperature of formation was 1536 °C, and the pressure was 3.28 GPa. The obtained original data on Sr, Nd, and Pb isotope composition have shown that the isotope composition of the magmatic melt formed from a PREMA source with a minor contribution of the latter. The mantle source for the studied basanites is assumed to be olivine pyroxenites (Ol + Cpx + Grt). The generation of basaltic melts occurred under the influence of a mantle plume, which caused Cenozoic activation.
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