05 Jan 2022
05 Jan 2022
Status: a revised version of this preprint is currently under review for the journal SE.

Progressive veining during peridotite carbonation: insights from listvenites in Hole BT1B, Samail ophiolite (Oman)

Manuel D. Menzel1, Janos L. Urai1, Estibalitz Ukar2, Thierry Decrausaz3, and Marguerite Godard3 Manuel D. Menzel et al.
  • 1Tectonics and Geodynamics, RWTH Aachen University, Lochnerstrasse 4-20, D-52056 Aachen, Germany
  • 2University of Texas at Austin, Bureau of Economic Geology, TX, USA
  • 3Géosciences Montpellier, CNRS, Université de Montpellier, Montpellier, France

Abstract. The reaction of serpentinized peridotites with CO2-bearing fluids to listvenite (quartz-carbonate rocks) requires massive fluid flux and significant permeability despite increase in solid volume. Listvenite and serpentinite samples from Hole BT1B of the Oman Drilling Project help to understand mechanisms and feedbacks during vein formation in this process. Samples analyzed in this study contain abundant magnesite veins in closely spaced, parallel sets and younger quartz-rich veins. Cross-cutting relationships suggest that antitaxial, zoned carbonate veins with elongated grains growing from a median zone towards the wall rock are among the earliest structures to form during carbonation of serpentinite. Their bisymmetric chemical zoning of variable Ca and Fe contents, a systematic distribution of SiO2 and Fe-oxide inclusions in these zones, and cross-cutting relations with Fe-oxides and Cr-spinel indicate that they record progress of reaction fronts during replacement of serpentine by carbonate in addition to dilatant vein growth. Euhedral terminations and growth textures of carbonate vein fill together with local dolomite precipitation and voids along the vein – wall rock interface suggest that these antitaxial veins acted as preferred fluid pathways allowing infiltration of CO2-rich fluids necessary for carbonation to progress. Fluid flow was probably further enabled by external tectonic stress, as indicated by closely spaced sets of subparallel carbonate veins. Despite widespread subsequent quartz mineralization in the rock matrix and veins, which most likely caused a reduction in the permeability network, carbonation proceeded to completion in listvenite horizons.

Manuel D. Menzel et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on se-2021-152', Dennis Quandt, 07 Feb 2022
    • AC1: 'Reply on RC1', Manuel Menzel, 06 Apr 2022
  • RC2: 'Comment on se-2021-152', Anonymous Referee #2, 07 Feb 2022
    • AC2: 'Reply on RC2', Manuel Menzel, 06 Apr 2022

Manuel D. Menzel et al.

Manuel D. Menzel et al.


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Short summary
Mantle rocks can bind large quantities of carbon by reaction with CO2, but this capacity requires that fluid pathways are not clogged by carbonate. We studied mantle rocks from Oman to understand the mechanisms allowing their reaction to carbonate and quartz. Using advanced imaging techniques, we show that abundant fractures were essential fluid pathways driving the reaction. Our results show that tectonic stress was important for fracture opening and a key ingredient for carbon fixation.