CARBONATE DEPOSITS OF EARLY ARCHEAN AGE. THEIR LIMESTONE-DOLOMITE RATIO

Abstract

We consider the composition and the genesis of oldest carbonates from recently obtained data on Early Archean greenstone belts and granulite complexes older than 3 b.y. These data cover about 300 chemical analyses, including those listed as average estimates. For rocks that lost much CO2 as a result of amphibolite- and granulite-facies metamorphism, we calculated the original content of their alumino-silicate component. The data, the rock ages and the decarbonatization-correcting method used by us are plotted. One characteristic example of a greenstone belt is the Vedlozero-Segozero, central Karelia.