Some Features of Epigenesis Based on Isotope Geochemistry

Problems of postsedimentary transformation are considered on the basis of isotope data. Epigenetic transformations affect all rock types. Data on sulfur isotopic composition show that sulfate sediments in evaporite sequences may become as much as two times thinner as a result of sulfate reduction. These processes are accompanied by the enrichment of solutions in Sr and Ba. This may leak to ore-grade accumulation of these elements. Data on strontium isotopic ratio indicate that carbonate rocks underwent partial dissolution and repeated recrystallization. The Rb–Sr isotope data demonstrate that silicate rocks (mainly mudrocks) were affected by the same processes.