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| Format: | Dataset Open Access |
| Language: | en |
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PANGAEA
2015
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| Online Access: | https://doi.org/10.1594/PANGAEA.856546 |
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| _version_ | 1867169109188280320 |
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| author | Nakamura, Kentaro Kato, Yasuhiro Tamaki, Kensaku Ishii, Teruaki |
| author_facet | Nakamura, Kentaro Kato, Yasuhiro Tamaki, Kensaku Ishii, Teruaki |
| collection | Datos científicos de ciencias marinas y ambientales |
| contents | Petrographic and geochemical analyses of basaltic rocks dredged from the first segment of the Southwest Indian Ridge near the Rodriguez Triple Junction have been completed in order to investigate water-rock interaction processes during mid-ocean ridge (MOR) hydrothermal alteration in the Indian Ocean. In the study area, we have successfully recovered a serial section of upper oceanic crust exposed along a steep rift valley wall which was uplifted and emplaced along a low angle normal fault. On the basis of microscopic observation, dredged samples are classified into three types: fresh lavas, low-temperature altered rocks, and high-temperature altered rocks. The fresh lavas have essentially the same chemical composition as typical N-MORB, although LILE and Nb are slightly enriched and depleted, respectively. Low temperature alteration brought about the enrichment of K2O, Rb, and U due to the presence of K-rich celadonite and U-adsorption onto Fe-oxyhydroxide and clay minerals. On the other hand, chloritization, albitization, and addition of base metals by high temperature hydrothermal alteration result in enrichments of MnO, MgO, Na2O, Cu, and Zn and depletions of CaO, K2O, Cr, Co, Ni, Rb, Sr, and Ba. In addition, U-enrichment is also observable in the high temperature altered rocks probably due to the decrease of uranite solubility in the reducing high-temperature hydrothermal solution. These petrological and geochemical features are comparable to those of the volcanic zone to transition zone rocks in the DSDP/ODP Hole 504B, indicating that our samples were recovered from the upper ~1000 m section of the oceanic crust. Only the alteration minerals related to off-axis alteration are absent in our samples dredged from near the spreading axis. The similarity of alteration between our samples from the Indian Ocean and the Hole 504B rocks from the Pacific Ocean suggests that MOR hydrothermal systems are probably similar across all world oceans. |
| format | Dataset Open Access |
| id | pangaea_https___doi_org_10_1594_PANGAEA_856546 |
| institution | PANGAEA |
| language | en |
| publishDate | 2015 |
| publisher | PANGAEA |
| record_format | pangaea |
| spellingShingle | (Supplement Table1) Abundances of major elements from KH93-3_DR10 at the Southwest Indian Ridge near the Rodriguez Triple Junction Nakamura, Kentaro Kato, Yasuhiro Tamaki, Kensaku Ishii, Teruaki Aluminium oxide; Barium; Calcium oxide; Cerium; Chromium; Cobalt; Copper; Depth, bottom/max; DEPTH, sediment/rock; Depth, top/min; Dredge; DRG; Dysprosium; Erbium; Europium; Gadolinium; Hafnium; Holmium; Iron oxide, Fe2O3; KH93-3_DR10; Lanthanum; Loss on ignition; Lutetium; Magnesium oxide; Manganese oxide; Neodymium; Nickel; Niobium; Phosphorus pentoxide; Potassium oxide; Praseodymium; Rock type; Rodriguez Triple Junction; Rubidium; Samarium; Sample ID; Scandium; Silicon dioxide; Sodium oxide; Strontium; Tantalum; Terbium; Thorium; Thulium; Titanium dioxide; Total; Type; Uranium; Vanadium; X-ray diffraction (XRD); Ytterbium; Yttrium; Zinc; Zirconium Petrographic and geochemical analyses of basaltic rocks dredged from the first segment of the Southwest Indian Ridge near the Rodriguez Triple Junction have been completed in order to investigate water-rock interaction processes during mid-ocean ridge (MOR) hydrothermal alteration in the Indian Ocean. In the study area, we have successfully recovered a serial section of upper oceanic crust exposed along a steep rift valley wall which was uplifted and emplaced along a low angle normal fault. On the basis of microscopic observation, dredged samples are classified into three types: fresh lavas, low-temperature altered rocks, and high-temperature altered rocks. The fresh lavas have essentially the same chemical composition as typical N-MORB, although LILE and Nb are slightly enriched and depleted, respectively. Low temperature alteration brought about the enrichment of K2O, Rb, and U due to the presence of K-rich celadonite and U-adsorption onto Fe-oxyhydroxide and clay minerals. On the other hand, chloritization, albitization, and addition of base metals by high temperature hydrothermal alteration result in enrichments of MnO, MgO, Na2O, Cu, and Zn and depletions of CaO, K2O, Cr, Co, Ni, Rb, Sr, and Ba. In addition, U-enrichment is also observable in the high temperature altered rocks probably due to the decrease of uranite solubility in the reducing high-temperature hydrothermal solution. These petrological and geochemical features are comparable to those of the volcanic zone to transition zone rocks in the DSDP/ODP Hole 504B, indicating that our samples were recovered from the upper ~1000 m section of the oceanic crust. Only the alteration minerals related to off-axis alteration are absent in our samples dredged from near the spreading axis. The similarity of alteration between our samples from the Indian Ocean and the Hole 504B rocks from the Pacific Ocean suggests that MOR hydrothermal systems are probably similar across all world oceans. |
| title | (Supplement Table1) Abundances of major elements from KH93-3_DR10 at the Southwest Indian Ridge near the Rodriguez Triple Junction |
| topic | Aluminium oxide; Barium; Calcium oxide; Cerium; Chromium; Cobalt; Copper; Depth, bottom/max; DEPTH, sediment/rock; Depth, top/min; Dredge; DRG; Dysprosium; Erbium; Europium; Gadolinium; Hafnium; Holmium; Iron oxide, Fe2O3; KH93-3_DR10; Lanthanum; Loss on ignition; Lutetium; Magnesium oxide; Manganese oxide; Neodymium; Nickel; Niobium; Phosphorus pentoxide; Potassium oxide; Praseodymium; Rock type; Rodriguez Triple Junction; Rubidium; Samarium; Sample ID; Scandium; Silicon dioxide; Sodium oxide; Strontium; Tantalum; Terbium; Thorium; Thulium; Titanium dioxide; Total; Type; Uranium; Vanadium; X-ray diffraction (XRD); Ytterbium; Yttrium; Zinc; Zirconium |
| url | https://doi.org/10.1594/PANGAEA.856546 |