Oxygen isotopic alteration of carbonates in the non-metamorphosed calcareous shales and sandstones from the South Kitakami Belt, northeastern Japan.
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Accession number;00A0651314
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| Title;Oxygen isotopic alteration of carbonates in the non-metamorphosed calcareous shales and sandstones from the South Kitakami Belt, northeastern Japan. |
| Author;
MORIKIYO TOSHIRO
(Assoc. Geological Collaboration in Japan (A.G.C.J.), JPN)
MATSUNAGA KINUKO
(Assoc. Geological Collaboration in Japan (A.G.C.J.), JPN)
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Journal Title;Earth Science
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Journal Code:F0193A
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ISSN:0366-6611
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VOL.54;NO.3;PAGE.153-158(2000)
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| Figure&Table&Reference;FIG.3, TBL.1, REF.12 |
| Pub. Country;Japan |
| Language;Japanese |
| Abstract;Carbon and oxygen isotope ratios were measured for calcite contained in non-metamorphosed calcareous clastic rocks from the South Kitakami Belt, northern Japan, ranging in age from late Permian to early Jurassic. The rocks studied include calcareous shales, calcareous sandstones, and diagenetic carbonate concretions. The calcite in the calcareous shales and sandstones has .DELTA. 13C values similar to that of marine limestones indicating its precipitation from seawater. On the other hand, .DELTA. 18O values of the calcite (+15.5.PERMIL. relative to SMOW, on an average) are lower than those of marine limestones by approximately 10.PERMIL., but remarkably uniform in spite of the diversity in its origin and in age. It is clear that the calcite does not retain its primary oxygen isotope ratios. The depletion in 18O of the calcite could be a result of isotope exchange with 18O-poor aqueous fluids, which had infiltrated into the formations after the stage of diagenesis. (author abst.) |
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