Variety and origin of magmas on Shatsky Rise, northwest Pacific Ocean
Shatsky Rise consists of thick (∼30 km maximum) 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 is the most abundant in volume and appears on all three large...
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Wiley
2012-08-01
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| Series: | Geochemistry, Geophysics, Geosystems |
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| Online Access: | https://doi.org/10.1029/2012GC004235 |
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| author | Takashi Sano Kenji Shimizu Akira Ishikawa Ryoko Senda Qing Chang Jun‐Ichi Kimura Mike Widdowson William W. Sager |
| author_facet | Takashi Sano Kenji Shimizu Akira Ishikawa Ryoko Senda Qing Chang Jun‐Ichi Kimura Mike Widdowson William W. Sager |
| author_sort | Takashi Sano |
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| description | Shatsky Rise consists of thick (∼30 km maximum) 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 is the most abundant in volume and appears on all three large edifices of the plateau: Tamu, Ori, and Shirshov massifs. Composition of the normal type is similar to normal mid‐ocean ridge basalt (N‐MORB) composition, but with slight relative enrichment of the more incompatible elements. The low‐Ti type is distinguished from the normal type basalt by slightly lower Ti content at a given MgO. Composition of the high‐Nb type is characterized by distinctively high contents of incompatible trace elements. U1349 type basalts are composed of more primitive and depleted compositions compared with the others. The normal type basalts constitute ∼94% of the lava units of the oldest Tamu Massif and non‐normal types (i.e., the other three types) basalts comprise ∼57% on the younger Ori Massif, implying that geochemical compositions may have become heterogeneous with time. Petrological examination demonstrates that compositions of the normal‐, low‐Ti‐, and high‐Nb‐type basalts evolved through fractional crystallization of olivine, plagioclase, and augite in shallow magma chambers (<200 MPa). Model calculations of immobile trace elements estimate that the normal type basalt can be formed by ∼15% melting of a depleted mantle source in the presence of residual garnet. This degree of melting is similar to N‐MORB, but the larger effect of residual garnet during petrogenesis implies that a greater depth of melting. |
| format | Article |
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| institution | Kabale University |
| issn | 1525-2027 |
| language | English |
| publishDate | 2012-08-01 |
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| series | Geochemistry, Geophysics, Geosystems |
| spelling | doaj-art-5a768fd3dfba4e19acd75d2d592fbaf12025-08-20T03:32:19ZengWileyGeochemistry, Geophysics, Geosystems1525-20272012-08-01138n/an/a10.1029/2012GC004235Variety and origin of magmas on Shatsky Rise, northwest Pacific OceanTakashi Sano0Kenji Shimizu1Akira Ishikawa2Ryoko Senda3Qing Chang4Jun‐Ichi Kimura5Mike Widdowson6William W. Sager7Department of Geology and Paleontology, National Museum of Nature and Science, 4-1-1 Amakubo, Tsukuba 305-0005, JapanInstitute for Research on Earth Evolution, Japan Agency of Marine-Earth Science and Technology, 2-15 Natsushima-Cho, Yokosuka, Kanagawa 237-0061, JapanDepartment of Earth Science and Astronomy, University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902, JapanInstitute for Research on Earth Evolution, Japan Agency of Marine-Earth Science and Technology, 2-15 Natsushima-Cho, Yokosuka, Kanagawa 237-0061, JapanInstitute for Research on Earth Evolution, Japan Agency of Marine-Earth Science and Technology, 2-15 Natsushima-Cho, Yokosuka, Kanagawa 237-0061, JapanInstitute for Research on Earth Evolution, Japan Agency of Marine-Earth Science and Technology, 2-15 Natsushima-Cho, Yokosuka, Kanagawa 237-0061, JapanDepartment of Earth and Environmental Sciences, Open University, Walton Hall, Milton Keynes MK7 6AA, UKDepartment of Oceanography, Texas A&M University, College Station, Texas 77843-3146, USAShatsky Rise consists of thick (∼30 km maximum) 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 is the most abundant in volume and appears on all three large edifices of the plateau: Tamu, Ori, and Shirshov massifs. Composition of the normal type is similar to normal mid‐ocean ridge basalt (N‐MORB) composition, but with slight relative enrichment of the more incompatible elements. The low‐Ti type is distinguished from the normal type basalt by slightly lower Ti content at a given MgO. Composition of the high‐Nb type is characterized by distinctively high contents of incompatible trace elements. U1349 type basalts are composed of more primitive and depleted compositions compared with the others. The normal type basalts constitute ∼94% of the lava units of the oldest Tamu Massif and non‐normal types (i.e., the other three types) basalts comprise ∼57% on the younger Ori Massif, implying that geochemical compositions may have become heterogeneous with time. Petrological examination demonstrates that compositions of the normal‐, low‐Ti‐, and high‐Nb‐type basalts evolved through fractional crystallization of olivine, plagioclase, and augite in shallow magma chambers (<200 MPa). Model calculations of immobile trace elements estimate that the normal type basalt can be formed by ∼15% melting of a depleted mantle source in the presence of residual garnet. This degree of melting is similar to N‐MORB, but the larger effect of residual garnet during petrogenesis implies that a greater depth of melting.https://doi.org/10.1029/2012GC004235Expedition 324Integrated Ocean Drilling ProgramShatsky Risechemical stratigraphylarge igneous provinceoceanic plateau |
| spellingShingle | Takashi Sano Kenji Shimizu Akira Ishikawa Ryoko Senda Qing Chang Jun‐Ichi Kimura Mike Widdowson William W. Sager Variety and origin of magmas on Shatsky Rise, northwest Pacific Ocean Geochemistry, Geophysics, Geosystems Expedition 324 Integrated Ocean Drilling Program Shatsky Rise chemical stratigraphy large igneous province oceanic plateau |
| title | Variety and origin of magmas on Shatsky Rise, northwest Pacific Ocean |
| title_full | Variety and origin of magmas on Shatsky Rise, northwest Pacific Ocean |
| title_fullStr | Variety and origin of magmas on Shatsky Rise, northwest Pacific Ocean |
| title_full_unstemmed | Variety and origin of magmas on Shatsky Rise, northwest Pacific Ocean |
| title_short | Variety and origin of magmas on Shatsky Rise, northwest Pacific Ocean |
| title_sort | variety and origin of magmas on shatsky rise northwest pacific ocean |
| topic | Expedition 324 Integrated Ocean Drilling Program Shatsky Rise chemical stratigraphy large igneous province oceanic plateau |
| url | https://doi.org/10.1029/2012GC004235 |
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