2001 Fiscal Year Final Research Report Summary
Process of magma channel formation in the upper mantle
| Project/Area Number |
12640462
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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 | HOKKAIDO UNIVERSITY |
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Principal Investigator |
NIIDA Kiyoaki Hokkaido Univ., Graduate School of Sci., Asso. Prof., 大学院・理学研究科, 助教授 (30111149)
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| Project Period (FY) |
2000 – 2001
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| Keywords | upper mantle peridotite / magma channel / basaltic primary magma / dunite / chromitite / harzburgite / Iherzolite / ophiolite |
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| Research Abstract |
Traces of channels formed by high temperature magma channeling through the upper mantle can be recognized in peridotites derived from the upper mantle. Dunite dykes in orogenic Iherzolites and discordant dunite-chromitite associations in ophiolitic peridotites are representative samples of magma channels formed in the upper mantle.
Mode of occurrence of channels, structures and textures of rocks, and the constituent minerals ware examined on the channel samples from the Iwanai-dake peridotite and the Horoman peridotite complexes in Hokkaido, together with those from the Fethiye ophiolite of SW Turkey and the Malakand ophiolite of Northern Pakistan. The sampling were performed as a systematic one across the magma channels to detect the effect of the channeling magma/peridotite wall interactions. The major constituent minerals such as olivine, orthopyroxene, clinopyroxene, and spinel, were analyzed by EPMA for major elements and also by LA-ICPMS for trace elements to detect the melt components and to characterize the type of the channeled magmas.
The dunite-chromitite channels from the Iwanai-dake peridotite complex are characterized by minerals with extremely high Mg# and Cr# signatures, suggesting a high-Mg andesite or a baninite magma for the magma type of the channel formation. The dunite enveloping the chromitite layer can be explained as replasive dunite formed by a melt/wall peridotite interaction during the magma channeling in the wall harzburgite. A number of dunite dykes were found as magma channel swarm in the host harzburgite and Iherzolite in the Horoman peridotite complex. Several kinds of magma types such as MORB-type basalt and a more refractory basalt were detected for magmas channeled in the Horoman peridotites.
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Research Products
(6 results)
