| Project/Area Number |
07454131
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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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 | Kanazawa University |
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Principal Investigator |
ARAI Shoji Kanazawa Univ.Faculty of Science, Professor, 理学部, 教授 (20107684)
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| Co-Investigator(Kenkyū-buntansha) |
TORAMARU Atsushi Kanazawa Univ.Faculty of Science, Assistant Professor, 理学部, 助教授 (50202205)
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| Project Period (FY) |
1995 – 1996
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| Project Status |
Completed (Fiscal Year 1996)
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| Budget Amount *help |
¥5,800,000 (Direct Cost: ¥5,800,000)
Fiscal Year 1996: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 1995: ¥4,600,000 (Direct Cost: ¥4,600,000)
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| Keywords | UPPER MANTLE / PERIDOTITE / MOHO TRANSITION ZONE / CHROMITITE / OPHIOLITE / CHROMIAN SPINEL / Magma / Mantle Interaction / ピクライト玄武岩 / トロクトライト / ホモ遷移帯 |
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| Research Abstract |
The interaction between upper mantle peridotite and melt has been studied both for deep-seated rocks and for effusive rocks. Our results are summarized as follows.
1. The highly depleted peridotite is possibly polygenetic. The Cr# of spinel in high-Mg harzburgite is higher in the Papuan ophiolite than in the Kamuikotan zone. the melting condition was hydrous in the Kamuikotan dunite-harzburgite and was anhydrous in the Papuan ophiolite.
2. The Moho transition zone of the Oman ophiolite is basically composed of the interaction product between harzburgite and MORB.The rocks are similar to the equivalents from Hess Deep, the Pacific Ocean, a fast-spreading ridge system.
3. The primitive MORB is possibly in equilibrium with dunite (and troctolite) of the Moho transition zone, an interaction product between more primitive MORB and mantle peridotite. The oceanic dunite is slightly variable in petrological characteristics whereas the mantle peridotite is highly variable depending on the spreading rate.
4. The secondary melt produced by the peridotite/melt interaction can concentrate both some compatible elements simultaneously and incompatible components, leading to precipitate podiform chromities.
5. The podiform chromitite is characteristically hosted by moderately depleted harzburgite with small smount of cpx and chromian spinel of moderate Cr# (around 0.5). Their chromian spinel often has high Cr#s (around 0.8), indicating supra-subduction zone environment for their formation.
6. The picrite basalt is an effusive facies of the peridotite/melt interaction product. The reaction product between peridotite xenolith and its host alkali basalt is a good analogue of the picritic mixture.
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