E3S Web Conf.
Volume 98, 201916th International Symposium on Water-Rock Interaction (WRI-16) and 13th International Symposium on Applied Isotope Geochemistry (1st IAGC International Conference)
|Number of page(s)
|Applied Isotope Geochemistry
|07 June 2019
Cl/Br and δ37Cl evolution in seawater expelled during the compaction of MX-80 smectite
Université de Lorraine, CREGU, GeoRessources laboratory, UMR CNRS 7359, BP70239, 54506 Vandoeuvre-lès-Nancy, France
2 Institut de Physique du Globe de Paris, 1, rue Jussieu 75238 Paris cedex 05, France
3 Total CSTJF, Avenue Larribau, Pau, F-64000, France
* Corresponding author: email@example.com
During a high pressure (up to 150 MPa) high temperature (up to 150°C) compaction experiment of MX-80 smectite equilibrated with ocean water, it was found that the Cl and Br concentrations in the expelled solution are progressively being decreased while simultaneously being increased in the compacted clay. This significant retention of Cl and Br in the pore water of the compacted clay is indicative of ultrafiltration by the clay. Despite the size difference between the two anions no significant chemical partitioning between Cl and Br is observed in the expelled water. The δ37Cl value of the expelled water shows a sharp decrease (from -0.1 ‰ down to -0.5‰) during the first steps of compactions (between 45MPa – 21°C and 65MPa – 30°C) and then remains stable until 125MPa – 120°C. The largest impact on anion and stable isotope composition is seen during the earlier phases of the compaction. It is supposed that the surface chemistry of the clay in combination with decreasing porosity result in re-equilibration of compressed and overlapping diffuse double layers which in part, drive the anion and δ37Cl evolution.
© The Authors, published by EDP Sciences, 2019
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