| Project/Area Number |
15540453
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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., Grad.School of Sci., Asso.Prof., 大学院・理学研究科, 助教授 (30111149)
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| Project Period (FY) |
2003 – 2004
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| Project Status |
Completed (Fiscal Year 2004)
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| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2004: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 2003: ¥2,800,000 (Direct Cost: ¥2,800,000)
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| Keywords | upper mantle / ophiolitic peridotite / basaltic magma / dunite / chromitite / harzburgite / olivine / spinel |
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| Research Abstract |
A trace of channels formed by high temperature magma channeling through the upper mantle can be ovserved in peridotites derived from the upper mantle. Dunite dykes in orogenic lherzolites and discordant dunite-chromitite associations in ophiolitic peridotites are representative samples for magma channels formed in the upper mantle.
Modes of occurrence of channels, structures and textures of rocks, and the constituent minerals were examined on the channel samples from the Iwanai-dake peridotite and the Horoman peridotite complexes in Hokkaido. The sampling were performed systematically across the channels to detect 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 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 boninite magma for the magma type. The dunite enveloping the chromitite layer can be explained as replacive dunite formed by a melt/wall peridotite interactions during the magma channeling in the wall harzburgite. A number of dunite dykes were found as magma channel swarm in the host harzburgite and lherzolite 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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