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Stable isotope study of carbonate sediments from the Coorong Area, South Australia
Author(s) -
BOTZ REINER W.,
BORCH CHRISTOPHER C.
Publication year - 1984
Publication title -
sedimentology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.494
H-Index - 108
eISSN - 1365-3091
pISSN - 0037-0746
DOI - 10.1111/j.1365-3091.1984.tb00890.x
Subject(s) - dolomite , aragonite , geology , dolomitization , carbonate , carbonate minerals , calcite , geochemistry , mineralogy , seawater , mineral , chemistry , facies , paleontology , oceanography , organic chemistry , structural basin
The mineralogy and isotope geochemistry of carbonate minerals in the Coorong area are determined by the water chemistry of different depositional environments ranging from seawater to evaporitically modified continental water. The different isotopic compositions of coexisting calcite and dolomite suggest that each of the above two minerals was formed from water of composition and origin unique to that specific mineral. In addition, the dolomite was not formed by simple solid state cation exchange. The occurrence of two types of dolomite was shown by isotope analysis and SEM observations. The dolomite, which is isotopically light (δ 13 C = ‐1 to ‐2% 0 ; δ 18 O=+3 to +5% 0 ) and of fine grain size (˜ 0·5 μm) probably precipitated under the influence of evaporitically modified continental water. Coarser grained dolomite (up to 4 μm) is isotopically heavier (δ 13 C=+3 to +4% 0 ; δ 18 O=+5 to + 6% 0 ) contains Mg in excess of Ca and was formed in or close to equilibrium with atmospheric CO 2 probably by the dolomitization of aragonite.