期刊
GEOCHIMICA ET COSMOCHIMICA ACTA
卷 70, 期 7, 页码 1728-1738出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.gca.2005.12.013
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We investigated the dissolution behaviour of polished calcite surfaces in situ using a fluid-cell atomic force microscope. Polished calcite surfaces enabled us to study the effects of applied surface stress and crystallographic orientation on calcite dissolution pattern formation. Thin-sections of Iceland spar single-crystals polished either parallel or with a 5 degrees miscut angle to {10 (1) over bar4} cleavage planes were studied. Compressive surface stresses of up to 50 MPa were applied to some of the thin-section samples by means of elastic concave bending. Experiments were carried out in semi-stagnant deionized water under mainly transport limited dissolution conditions. Samples polished parallel to {10 (1) over bar4} cleavage planes dissolved by the formation of etch-pits originating from polishing defects. The dissolution behaviour of 5 degrees miscut surfaces was relatively unaffected by polishing defects, since no etch-pits developed in these samples. Dissolution of the miscut samples led to stepped or rippled surface patterns on the nanometer scale that coarsened during the first 30-40 min of the experiments. Possible reasons for the pattern-coarsening were: (i) progressive bunching of retreating dissolution steps and (ii) surface energy driven recrystallization (Ostwald ripening) under transport limited dissolution conditions. A flat polished miscut surface in calcite may recrystallize into a hill-and-valley structure in a (near-)saturated solution so as to lower its total surface free energy in spite of a larger surface area. No clear effect of applied stress on dissolution pattern formation has been observed. (c) 2006 Elsevier Inc. All rights reserved.
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