Alteration Heterogeneities in Peridotites Exhumed on the Southern Wall of the Atlantis Massif (IODP Expedition 357)
Open access
Date
2018-07Type
- Journal Article
Abstract
Serpentinized and metasomatized peridotites intruded by gabbros and dolerites have been drilled on the southern wall of the Atlantis Massif (Mid-Atlantic Ridge, 30°N) during International Ocean Discovery Program (IODP) Expedition 357. They occur in seven holes from five sites making up an east–west-trending, spreading-parallel profile that crosscuts this exhumed detachment footwall. Here we have taken advantage of this sampling to study heterogeneities of alteration at scales less than a kilometer. We combine textural and mineralogical observations made on 77 samples with in situ major and trace element analyses in primary and serpentine minerals to provide a conceptual model for the development of alteration heterogeneities at the Atlantis Massif. Textural sequences and mineralogical assemblages reveal a transition between an initial pervasive phase of serpentinization and subsequent serpentinization and metasomatism focused along localized pathways preferentially used by hydrothermal fluids. We propose that these localized pathways are interconnected and form 100 m- to 1 km-sized cells in the detachment footwall. This change in fluid pathway distribution is accompanied by variable trace element enrichments in the serpentine textures: deep, syn-serpentinization fluid–peridotite interactions are considered the source of Cu, As, and Sb enrichments, whereas U and Sr enrichments are interpreted as markers of later, shallower fluid–serpentinized peridotite interaction. Alteration of gabbros and dolerites emplaced in the peridotite at different lithospheric levels leads to the development of amphibole-, chlorite- and/or talc-bearing textures as well as enrichments in light rare earth elements, Nb, Y, Th, and Ta in the serpentine textures of the surrounding peridotites. Combining these observations, we propose a model that places the drill holes in a conceptual frame involving mafic intrusions in the peridotites and heterogeneities during progressive alteration and emplacement on the seafloor. Show more
Permanent link
https://doi.org/10.3929/ethz-b-000302158Publication status
publishedExternal links
Journal / series
Journal of PetrologyVolume
Pages / Article No.
Publisher
Oxford University PressSubject
Atlantis Massif; Fluid-rock interaction; International Ocean Discovery Program (IODP); SerpentinizationOrganisational unit
08808 - Bernasconi-Green, G. (Tit.-Prof.) (em.)
Funding
200021_156011 - Hierarchical carbon-fiber composites with tailored interphase obtained via electrophoretic deposition of magnetized and funtionalized carbon nanotubes (SNF)
163187 - Hydration and carbonation of mantle peridotite: Drilling the Atlantis Massif (MAR 30°N) and the Samail ophiolite (Oman) (SNF)
Notes
It was possible to publish this article open access thanks to a Swiss National Licence with the publisher.More
Show all metadata