Reaction fronts, permeability and fluid pressure development during dehydration reactions



Leclere, Henri, Faulkner, Daniel ORCID: 0000-0002-6750-3775, Llana-Funez, Sergio, Bedford, John ORCID: 0000-0002-2077-4797 and Wheeler, John ORCID: 0000-0002-7576-4465
(2018) Reaction fronts, permeability and fluid pressure development during dehydration reactions. EARTH AND PLANETARY SCIENCE LETTERS, 496. pp. 227-237.

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Abstract

Fluids released by prograde metamorphism are often invoked to explain a range of crustal processes from earthquake triggering to metasomatism. These fluids can be either trapped and overpressured or released and channelized depending on the interplay between permeability, reaction rate and compaction. Experimental data are presented, measuring permeability, porosity and microstructural evolution throughout the dehydration of gypsum to form bassanite. Reaction fronts, regions over which the reaction largely occurs, are used as a framework to explain the results. Experiments were conducted under hydrostatic conditions at a constant temperature of 115 °C at two effective pressures of 60 MPa and 110 MPa and three pore-fluid pressures of 20, 40 and 60 MPa. At high effective pressure, creep of the gypsum solid framework results in low porosity and permeability, producing high pore-fluid pressure build-up that slows the reaction rate. A clearly defined narrow reaction front migrates along the sample and the average permeability remains low until the front sweeps across the entire sample. Conversely, at low effective pressure the reaction front is wide producing a permeable, drained network. Average permeability is enhanced significantly after only a small fraction of the reaction has completed, by the interconnection of open pores. This study shows that the width of reaction fronts and hence the permeability development is strongly controlled by compaction. The reaction front velocity is broadly dependent on permeability and the reaction driving force. A simple quantitative model for these relationships is developed.

Item Type: Article
Additional Information: publisher: Elsevier articletitle: Reaction fronts, permeability and fluid pressure development during dehydration reactions journaltitle: Earth and Planetary Science Letters articlelink: https://doi.org/10.1016/j.epsl.2018.05.005 content_type: article copyright: © 2018 The Author(s). Published by Elsevier B.V.
Uncontrolled Keywords: reaction front, gypsum dehydration, permeability, pore-fluid pressure, compaction, subduction zone
Depositing User: Symplectic Admin
Date Deposited: 09 Jul 2018 06:06
Last Modified: 19 Jan 2023 01:30
DOI: 10.1016/j.epsl.2018.05.005
Related URLs:
URI: https://livrepository.liverpool.ac.uk/id/eprint/3023454