Carbon and oxygen isotopic ratios of carbonates filling gaps in the Ogi basalt, Sado-ga-shima, Niigata, Japan

Abstract

-The carbon and oxygen isotopic abundances were determined for calcites and dolomites filling gaps in the Ogi basalt. The isotopic ratios of the carbonates are in the range from -24 to -32 ‰ in δ13CPDB and from 31 to 36 ‰ in δ18OSMOW. They were too low in δ13C and too high in δ18O to understand that they were derived from carbonatite. The δ18O values are also too high to interpret that they were derived from basaltic magma. The isotopic data suggest that they were precipitated probably from lagoonal sea water under anaerobic conditions.