Data/hora: 09/06/2024 06:40:08

Provedor de dados: 	5	
País: 	France	
Título: 	Tectonic structure, lithology, and hydrothermal signature of the Rainbow massif (Mid-Atlantic Ridge 36°14′N)	
Autores: 	Andreani, Muriel; Escartin, Javier; Delacour, Adelie; Ildefonse, Benoit; Godard, Marguerite; Dyment, Jerome; Fallick, Anthony E.; Fouquet, Yves.	
Data: 	2014-09	
Ano: 	2014	
Palavras-chave: 	Rainbow; Hydrothermal; Serpentinization; Atlantic ridge.	
Resumo: 	Rainbow is a dome-shaped massif at the 36°14′N nontransform offset along the Mid-Atlantic Ridge. It hosts three ultramafic-hosted hydrothermal sites: Rainbow is active and high temperature; Clamstone and Ghost City are fossil and low temperature. The MoMARDREAM cruises (2007, 2008) presented here provided extensive rock sampling throughout the massif that constrains the geological setting of hydrothermal activity. The lithology is heterogeneous with abundant serpentinites surrounding gabbros, troctolites, chromitites, plagiogranites, and basalts. We propose that a W dipping detachment fault, now inactive, uplifted the massif and exhumed these deep-seated rocks. Present-day deformation is accommodated by SSW-NNE faults and fissures, consistent with oblique teleseismic focal mechanisms and stress rotation across the discontinuity. Faults localize fluid flow and control the location of fossil and active hydrothermal fields that appear to be ephemeral and lacking in spatiotemporal progression. Markers of high-temperature hydrothermal activity (∼350°C) are restricted to some samples from the active field while a more diffuse, lower temperature hydrothermal activity (&lt;220°C) is inferred at various locations through anomalously high As, Sb, and Pb contents, attributed to element incorporation in serpentines or microscale-sulfide precipitation. Petrographic and geochemical analyses show that the dominant basement alteration is pervasive peridotite serpentinization at ∼160–260°C, attributed to fluids chemically similar to those venting at Rainbow, and controlled by concomitant alteration of mafic-ultramafic units at depth. Rainbow provides a model for fluid circulation, possibly applicable to hydrothermalism at oceanic detachments elsewhere, where both low-temperature serpentinization and magmatic-driven high-temperature outflow develop contemporaneously, channeled by faults in the footwall and not along the detachment fault.	
Tipo: 	Text	
Idioma: 	Inglês	
Identificador: 	http://archimer.ifremer.fr/doc/00210/32151/30609.pdf

http://archimer.ifremer.fr/doc/00210/32151/30610.pdf

DOI:10.1002/2014GC005269

http://archimer.ifremer.fr/doc/00210/32151/	
Editor: 	Amer Geophysical Union	
Formato: 	application/pdf	
Fonte: 	Geochemistry Geophysics Geosystems (1525-2027) (Amer Geophysical Union), 2014-09 , Vol. 15 , N. 9 , P. 3543-3571	
Fonte: 	2014. American Geophysical Union. All Rights Reserved.

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