Tectonic structure, lithology, and hydrothermal signature of the Rainbow massif (Mid-Atlantic Ridge 36°14′N)
| Type | Article | ||||||||||||
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| Date | 2014-09 | ||||||||||||
| Language | English | ||||||||||||
| Author(s) | Andreani Muriel1, Escartin Javier2, Delacour Adelie3, Ildefonse Benoit4, Godard Marguerite4, Dyment Jerome2, Fallick Anthony E.5, Fouquet Yves6 | ||||||||||||
| Affiliation(s) | 1 : Univ Lyon 1, ENS, Lab Geol Lyon, UMR 5672, F-69365 Lyon, France. 2 : CNRS, Inst Phys Globe Paris, UMR 7154, Paris, France. 3 : Univ St Etienne, CNRS, UMR 6524, Lab Magmas & Volcans, St Etienne, France. 4 : Univ Montpellier 2, CNRS, UMR 5243, Geosci Montpellier, Montpellier, France. 5 : Scottish Univ Environm Res Ctr, Glasgow, Lanark, Scotland. 6 : IFREMER, Ctr Brest, Plouzane, France. |
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| Source | Geochemistry Geophysics Geosystems (1525-2027) (Amer Geophysical Union), 2014-09 , Vol. 15 , N. 9 , P. 3543-3571 | ||||||||||||
| DOI | 10.1002/2014GC005269 | ||||||||||||
| WOS© Times Cited | 55 | ||||||||||||
| Note | ggge20526-sup-0002-suppinfotabS1.xlsx Tables S1 ggge20526-sup-0003-suppinfotabS2.xlsx Tables S2 ggge20526-sup-0004-suppinfotabS3.xlsx Tables S3 ggge20526-sup-0005-suppinfotabS4.xlsx Tables S4 ggge20526-sup-0006-suppinfofigS1.jpg Figure S1 | ||||||||||||
| Keyword(s) | rainbow, hydrothermal, serpentinization, Atlantic ridge | ||||||||||||
| Abstract | 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 (<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. | ||||||||||||
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