2011 Fiscal Year Final Research Report
Evaluation of oceanic crust evolution based on melting experiments on gabbro
| Project/Area Number |
21540500
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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 | National Museum of Nature and Science, Tokyo |
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Principal Investigator |
SANO Takashi 独立行政法人国立科学博物館, 地学研究部, 研究主幹 (40329579)
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| Project Period (FY) |
2009 – 2011
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| Keywords | 統合国際深海掘削計画 / 中央海嶺 / マグマ / シャツキー海台 / ハンレイ岩 / 巨大火成区 / 玄武岩 / マントル |
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| Research Abstract |
A continuous section from extrusive lavas, through sheeted dikes, and uppermost gabbros recovered from Ocean Drilling Program Hole 1256D provides important information regarding magma plumbing systems beneath superfast spreading ridges. Melting experiments demonstrate that a model of fractional crystallization from a magma of composition similar to one of the more primitive gabbros in a shallow melt lens reasonably explains mineral and whole-rock compositions of many lavas and dikes. About half of the dike samples have more evolved Fe-rich compositions than the extrusive lava samples. Magma densities of the Fe-rich dikes are a little higher than those of lavas, suggesting that these dike magmas would not reach the surface. Major cyclic variations of Mg#(100 X Mg/(Fe+Mg) in mole) occur within the extrusive lava pile. In each cycle, Mg# increases with depth, suggesting successive episodes of fractionation caused by intermittent magma injection to the melt lens. Shatsky Rise consists of thick(> 22 km) basaltic crust with various geochemical compositions. Geochemistry data indicate that four magma types exist on the plateau ; namely normal, low-Ti, high-Nb, and U1349 types. The normal type basalts constitute～94% lava units of the oldest edifice(Tamu Massif) and non-normal type(the low-Ti, high-Nb and U1349 types) basalts are～57% on the younger Ori Massif, implying that geochemical compositions may have become heterogeneous with time.
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[Journal Article] Massive basalt flows on the southern flank of Tamu Massif, Shatsky Rise : a reappraisal of ODP Site 1213 basement units, In Sager, W. W., T. Sano, J. Geldmacher(Editors)2011
Author(s)
Koppers, A. A. P., T. Sano, J. H. Natland, M. Widdowson, R. Almeev, A. R. Greene, D. T. Murphy, A. Delacour, M. Miyoshi, K. Shimizu, S. Li, N. Hirano, J. Geldmacher, and the Expedition 324 Scientists
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Journal Title
Proceeding of the Integrated Ocean Drilling Program
Volume: 324
DOI
Peer Reviewed
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