STRONTIUM ISOTOPE VARIATIONS IN THE SEDIMENTARY SEQUENCE OF LAKE BAIKAL

Abstract

The study of Sr isotope variations in sedimentary sequences shows that this geochemical parameter is an indicator of both climatic and endogenous processes. It has been established that an increase in 87Sr/86Sr values in ocean carbonates over the last 600 Ma correlates with the scale of orogenic movements at the divergent plate margins and global cooling events. In particular, collision of the Indian Eurasian plates 380 Ma ago triggered the growth of the largest mountain systems (the Himalayas and Tibet plateau) and undoubtedly provoked changes in global atmospheric circulation. This mountainous area occupies 4.7 mln km2 (4.2% of the present-day land area). However, 25% of dissolved salts transported from continents due to weathering are delivered from this region. Significant volumes of rocks exhumed during growth of the Himalayas and Tibet are composed of granitoids and felsic schists.