1989 Fiscal Year Final Research Report Summary
Sm-Nd, Rb-Sr isotope compositions of accretionary complex
| Project/Area Number |
63540614
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
地質学一般
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| Research Institution | Kyushu University |
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Principal Investigator |
HAMAMOTO Reiko Kyushu Univ., Science, Researcher, 理学部, 教務員 (40089917)
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| Co-Investigator(Kenkyū-buntansha) |
YANAGI Takeru Kyushu Univ., Science, Professor, 理学部, 教授 (90037234)
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| Project Period (FY) |
1988 – 1989
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| Keywords | Sr isotope composition / Subduction complex / Pelagic sediment / Aeolian deposit / Shimanto terrain / Umber / Red shale / Pillow basalt |
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| Research Abstract |
Aradani Formation of Hyuga Group in the Shimanto terrain is a subduction complex, Middle Eocene in age. 16 whole rock samples of greenstone-pelagic sequence (pillow basalt-umber-red shale-green shale black shale) in Aradani Formation were analyzed by Rb-Sr isotope dilution method. The results are as follows.
(1) Average Rb concentration is 1.1 ppm, which is similar to average Rb content of MORB (Mid Oceanic Ridge Basalt). Rare elements pattern supported that the pillow basalt was MORB type. But its 87Sr/86Sr ratio(average 0.70876) is higher than MORB(average 87Sr/86Sr=0.703). It suggests that the basalt magma reacts to sea water. 87Sr/86Sr ratio of interpillow limestone indicate that the Sr ratio of sea water in Early Eocene is 0.70876.
(2) 87Sr/86Sr variation of each umber and red shale samples relates to the distance from pillow basalt, and the variation indicates the umber is derived from mixing of basalic magma (hydrothermal) and red shale.
(3) 87Sr/86Sr ratios of the pelagic sediments(red shale and black shale) are extremely higher than the ratio of sea water, therefore The pelagic sediments are aeolian deposits derived from old continental crusts.
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Research Products
(2 results)
