Homogeneous basalts from the East Pacific Rise at 21° N: seady state magma reservoirs at moderately fast spreading centers
| Other titles | Homogénéité des basaltes de la Dorsale Est-PacifIque à 21°N réservoirs magmatiques permanents sous les zones d'accrétion moyennement rapide. | ||||||||
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| Type | Article | ||||||||
| Date | 1980 | ||||||||
| Language | English | ||||||||
| Author(s) | Juteau T1, Eissen Jp1, Francheteau J2, Needham David2, Choukroune P3, Rangin C4, Seguret M5, Ballard Rd6, Fox Pj7, Normark Wr8, Carranza A9, Cordoba D10, Guerrero J10 | ||||||||
| Affiliation(s) | 1 : Université de Strasbourg, Laboratoire de Minéralogie et Pétrographie, 1, rue Blessig, 67084 Strasbourg Cedex 2 : CTR OCEANOL BRETAGNE, F-29273 BREST, FRANCE. 3 : UNIV PARIS 06, GEOL STRUCT LAB, F-75230 PARIS 05, FRANCE. 4 : UNIV RENNES, GEOL STRUCT LAB, F-35031 RENNES, FRANCE. 5 : UNIV MONTPELLIER 2, GEOL STRUCT LAB, F-34060 MONTPELLIER, FRANCE. 6 : WOODS HOLE OCEANOG INST, WOODS HOLE, MA 02543 USA. 7 : SUNY ALBANY, ALBANY, NY 12222 USA. 8 : US GEOL SURVEY, PACIFIC ARCTIC BRANCH MARINE GEOL, MENLO PK, CA 94025 USA. 9 : NATL AUTONOMOUS UNIV MEXICO, CTR CIENCIAS MAR & LIMNOL, MEXICO CITY 20, MEXICO. 10 : NATL AUTONOMOUS UNIV MEXICO, INST GEOL, MEXICO CITY 20, MEXICO. |
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| Source | Oceanologica Acta (0399-1784) (Gauthier-villars), 1980 , Vol. 3 , N. 4 , P. 487-503 | ||||||||
| WOS© Times Cited | 40 | ||||||||
| Mot-Clé(s) | Dorsale Est-PacifIque, Pétrologie des basaltes sous-marins, Coussins, laves fluides, piliers, Générations de cristaux, Globules de sulfure | ||||||||
| Keyword(s) | East Paciflc Rise, Petrology of submarine basalts, Pillows, sheet flows, pillars, Generations of crystals, Sulphide globules | ||||||||
| Abstract | Fort y basaltic rocks collected by submersible during the "Cyamex" expedition (1978) on the East PacifIc Rise at 21 oN, a moderately fast spreading segment (6 cm/year opening rate) of the mid-ocean ridge, consist of angular pillow fragments and glass buds, sheet-flow slabs and samples of columnar pillars standing in collapsed fossillava pools. Most of the rocks are from the crestal are a of the Rise. The collection shows a striking petrographic homogeneity wh en compared with the range of basalts found on other segments of midocean ridges: olivine-phyric, or highly plagioclase-phyric rocks, so common in the slowspreading "Famous" are a in the Atlantic, are absent. All samples are typical lowpotassium oceanic tholeiites with a limited fractionation trend. Pillow-lavas, thin and thick sheet-flows cannot be distinguished by their major element compositions, as in the Galapagos rift which has the same spreading rate as the EPR at 21°N. Further, ferrobasalts have been described from the Galapagos rift, but do not appear in the Cyamex rocks. In the Cyamex area, olivine and plagioclase are the main silicate phases, and clinopyroxene is absent. In the pillows and sheet-flow samples, four generations of olivine and plagioclase crystals are distinguished. Samples from the fossillava pools are aphyric. The corresponding magma batches are presumed to have migrated rapidly through the magma chamber, and to have been extruded in large volumes, possibly during episodes ofhigh instantaneous opening rate. Fe-Ni and Fe-Cu-rich sulphide phases are common in an lava types as massive globules scatterred through the glass, or as microglobules decorating the walls of empty vesicles. Palagonite and Fe-Mn oxide thicknesses across the strike of the Rise indicate relative ages compatible with successive extrusions at the Rise axis. The few basaltic samples collected in the Western BrunhesMatuyama reversaI area and the Tamayo transform fault zone are not signiflcantly different from those described in the crestal area, except that they are more altered and have .thicker palagonite and manganese coats. | ||||||||
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