Data/hora: 01/06/2024 12:35:10

Provedor de dados: 	5	
País: 	France	
Título: 	Homogeneous basalts from the East Pacific Rise at 21° N: seady state magma reservoirs at moderately fast spreading centers	
Autores: 	Juteau, T; Eissen, Jp; Francheteau, J; Needham, David; Choukroune, P; Rangin, C; Seguret, M; Ballard, Rd; Fox, Pj; Normark, Wr; Carranza, A; Cordoba, D; Guerrero, J.	
Data: 	1980	
Ano: 	1980	
Palavras-chave: 	Dorsale Est-PacifIque Pétrologie des basaltes sous-marins Coussins; Laves fluides; Piliers Générations de cristaux Globules de sulfure East Paciflc Rise Petrology of submarine basalts Pillows; Sheet flows; Pillars Generations of crystals Sulphide globules.	
Resumo: 	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.	
Tipo: 	Text	
Idioma: 	Inglês	
Identificador: 	http://archimer.ifremer.fr/doc/00323/43430/43112.pdf

http://archimer.ifremer.fr/doc/00323/43430/	
Editor: 	Gauthier-villars	
Formato: 	application/pdf	
Fonte: 	Oceanologica Acta (0399-1784) (Gauthier-villars), 1980 , Vol. 3 , N. 4 , P. 487-503	
Fonte: 	Gauthier-Villars

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