1999 Fiscal Year Final Research Report Summary
System dynamics in a subduction zone
| Project/Area Number |
09640572
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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 |
Petrology/Mineralogy/Science of ore deposit
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| Research Institution | Ehime University |
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Principal Investigator |
SAKAKIBARA Masayuki Ehime University, Department of Earth Sciences, Associated Professor, 理学部, 助教授 (80202084)
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| Project Period (FY) |
1997 – 1999
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| Keywords | subduction / fluid / accretionary prism / mass transfer / oxygen isotope / out-of-sequence thrust / deep part of accretionary complex / shallow part of accretionary complex |
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| Research Abstract |
A subduction is a main process for the circulation of fluids from deep sea to crust and mantle. The fluids trapped as pore fluids or in hydrous minerals of oceanic crust or overlying sediments are released during an early subduction. Released fluids mostly pass through the accretionary complex and have physical and chemical effects upon it.
In this research project, we have succeeded in elucidating a series of mass transfer by fluids. The results are as follows.
(1) Oxygen isotope ratios of shallow parts of the accretionary complex (<10km depth) are not greatly influenced by fluids.
(2) In medium parts of accretionaly complex (10-15km depth), fluids pass through shear zones and give rise to mass transfer of the vicinity of shear zones such as out-of-sequence thrusts.
(3) In deep part of accretionaly complex, fluid released by dehydration pass through along the lithological boundaries and regionally give oxygen isotopic alterations.
(4) Oxygen isotopic ratios of pelitic and basic rocks are the largest in medium parts of the accretionary complex. On the other hand, oxygen isotopic ratios of calcareous rocks decreases with increasing depth.
(5) In shallow accretionary complex, domains of isotopic alterations are smaller than a size of hand speciman, whereas in deep one, those are a mappable order.
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