Home – Home – Jornals – Russian Geology and Geophysics 2005 number 7

New Rb-Sr dates have been obtained for metabasalts of the Tyya Formation of the Olokit structure-lithological complex (SLC) (927±10 Ma), as well as model Nd ages for the Purpol (Patom SLC) and Anai (Sarma SLC) Formations (2.54 and 2.61-2.82 Ga, respectively). The Tyya metabasalts are intermediate in geochemical composition between flood basalts and N-MORB and were produced from a primitive source ((⁸⁷Sr/⁸⁶Sr)₀ = 0.7025-0.7032). They are similar to metabasalts of the Medvezhevka and Anai Formations that occur at the same stratigraphic level. High-alumina schists and quartzites of the Purpol and Anai Formations are compositionally identical to redeposited weathering crusts and, together with the Tuluokit Formation of the Olokit SLC, form a single basal level of the Patom SLC, which frames the Chuya and Cisbaikalian uplifts of the Precambrian basement of the Siberian Platform. We have summarized data on the ages of all formations of the northern Baikal area published for the last 15 years and have considered the evolution history of these objects.