Va. Makrygina et al., Geochemistry of isotopes of carbon, oxygen, and rare-earth elements in metasediments of the Ol'khon metamorphic complex (Western Prebaikalia), GEOL GEOFIZ, 41(10), 2000, pp. 1360-1368
The isotopic compositions of carbon, oxygen, and strontium in marbles and q
uartzites in various metamorphic zones of the Ol'khon metamorphic complex a
nd the REE patterns of these rocks prove that the source rocks of the latte
r formed in a shallow-sea environment under reducing conditions preventing
a complete loss of organic relies. The variations in carbon isotope ratio i
n graphites and calcites of marbles are related to isotope exchange between
these minerals with increasing temperature of regional metamorphism. The c
arbonate-free metasediments are most similar in isotopic composition of car
bon to biogenic source rocks.