Conference proceeding
Prior tectonic brecciation favors carbonation of abyssal serpentinites; a petrographic and stable isotope study of Southwest Indian Ridge dredged samples
American Geophysical Union Fall Meeting, Vol.2014
American Geophysical Union 2014 fall meeting
12/2014
Abstract
Partial carbonation of the uppermost oceanic lithosphere represents a significant natural reservoir for long term carbon storage. About 25% of the oceanic basement formed at slow spreading ridges is made of tectonically exhumed and variably serpentinized abyssal peridotites in which carbonates veins have been documented. Previous studies indicate formation of these veins at temperatures between nearly equal 180 degrees C and <10 degrees C, at the seafloor or in shallow levels of the exhumation faults, and from fluids ranging from pure seawater to seawater-hydrothermal fluids mixtures. In this presentation we show that partial carbonation of serpentinites dredged at and near the easternmost Southwest Indian Ridge (SWIR) similarly occurred in two settings: dolomite formed at temperatures nearly equal 50 degrees C presumably in shallow fluid-rich domains of the exhumation fault(s), while aragonite formed at yet lower temperatures within a few meters of the seafloor. We also present a detailed petrographic study of carbonation textures showing that while carbonate veining is prevalent in the seafloor-type carbonation, it is superseded by serpentine dissolution and replacement in our samples of the fault zone-type carbonation. In these samples, dolomite preferably replaces the matrix of a tectonic breccia, that comprises angular clasts of serpentinite. TEM observations and diffraction patterns identify this matrix as microcrystalline to amorphous serpentine and document the contacts between this material and the dolomite. A comparison with textures reported for carbonated serpentine breccia from the Alps, and the Galicia margin suggests that prior tectonic brecciation enhances the potential for pervasive carbonation of serpentinites in the oceanic lithosphere at both mid-ocean ridges and the ocean-continent transition of divergent continental margins.
Details
- Title: Subtitle
- Prior tectonic brecciation favors carbonation of abyssal serpentinites; a petrographic and stable isotope study of Southwest Indian Ridge dredged samples
- Creators
- Mathilde Cannat - CNRS, Institut de Physique du Globe de Paris Paris FRA FranceValerie PayreI. Martinez
- Resource Type
- Conference proceeding
- Publication Details
- American Geophysical Union Fall Meeting, Vol.2014
- Conference
- American Geophysical Union 2014 fall meeting
- Publisher
- American Geophysical Union
- Alternative title
- AGU 2014 fall meeting
- Language
- English
- Date published
- 12/2014
- Academic Unit
- Earth and Environmental Sciences
- Record Identifier
- 9984318245002771
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