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IDENTIFYING CLAY MINERALS FROM UPPER CENOZOIC STRATONS IN BARGUZIN VALLEY OF THE BAIKAL RIFT ZONE

R. Alokla 1, I. S. Chuvashova 1,2, S. V. Rasskazov 1,2, A. V. Oshchepkova 1,3, T. S. Fileva 2

1 Irkutsk State University, Irkutsk, Russia; 2 Institute of the Earth’s Crust SB RAS, Irkutsk, Russia; 3 A.P.Vinogradov Institute of Geochemistry SB RAS, Irkutsk, Russia

Sedimentary sequence of Upper Oligocene Pre-Tankhoi stratum, Upper Miocene – Lower Pliocene lacustrine stratum of Tankhoi Formation, Upper Pliocene – Eopleistocene ocherous alluvial stratum of Anosovka Formation, and overlapping Quaternary sediments are studied in wells of the southern Barguzin Valley. Clay minerals are identified in the stratigraphic sequence using physicochemical modeling of the mineral compositions. Lacustrine deposits of the Tankhoi Formation are characterized by minerals–indicators chlorite and montmorillonite. A microcline is calculated in a transitional layer and Anosovka Formation, biotite and microcline in Pre-Tankhoi unit. In all samples, quartz, kaolinite, smectite group phases, and hydromica were determined. The calculated data are consistent with the results of X-ray phase studies of pelitic fractions. The compositional change of clay minerals from Tankhoi to Anosovka Formations in Barguzin Valley is correlated with a similar change in clay mineral assemblages revealed by 600-meter BDP-98 well of the Academic Ridge in Baikal Depression.

Keywords: clay minerals, Barguzin Valley, X-ray phase method, physicochemical modeling.

DOI 10.20403/2078-0575-2020-2-68-80