TY JOUR TI Geochemistry and Mineralogy of Organic-Mineral Bottom Sediment of Small Lakes in the Middle Mountains of the Russian Altai: A Case Study of the Chibitka Lake System KW sapropel KW small lakes KW nival type of lithogenesis KW authigenic minerals KW Russian Altai JO Russian Journal of Earth Sciences AU Ovdina, E.A. AU Strakhovenko, V.D. AU Malov, G.I. AU Malov, V.I. PY 2025 IS 25 PB Geophysical Center of the Russian Academy of Sciences