2005 Fiscal Year Final Research Report Summary
The geologic events causing oxygen isotopic alteration of sedimentary carbonate minerals in the rocks of the North and South Kitakami Belts.
| Project/Area Number |
16540415
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Geology
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| Research Institution | Department of Geology, Faculty of Science, Shinshu University |
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Principal Investigator |
MORIKIYO Toshiro Shinshu University, Geology, Professor, 理学部, 教授 (90115379)
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| Project Period (FY) |
2004 – 2005
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| Keywords | oxygen isotopes / sedimentary carbonate / Oshima orogeny / isotopic alteration / South Kitakami belt |
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| Research Abstract |
Carbon and oxygen isotope ratios were measured for calcite contained in non-metamorphosed calcareous clastic rocks from the North and South Kitakami Belts, northern Japan, ranging in age from late Permian to Cretaceous. The rocks studied include calcareous shales, calcareous sandstones, and diagenetic carbonate concretions. The calcite in the calcareous shales and sandstones has δ^<13>C values similar to that of marine limestones indicating its precipitation from seawater. On the other hand, δ^<18>O values of the calcite (+15.5‰ realative to SMOW, on an average) are lower than those of marine limestones by approximately 10‰, but remarkably uniform in spite of the diversity in its origin and in age. It is clear that calcite dose not retain its primary oxygen isotope ratios. The depletion in ^<18>O of the calcite is interpreted as being due to the result of isotope exchange with ^<18>O-poor aqueous fluids, which had infiltrated into the formations after the diagenesis.
The carbonates contained in the strata deposited after the Oshima Orogeny do not show any sign of oxygen isotope alteration. Thus it is considered that the lowering in δ^<18>O in the carbonates is related to the hydrothermal activity during the Oshima orogeny.
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Research Products
(1 results)
