Reaction-induced microcracking; an experimental investigation of a mechanism for enhancing anatectic melt extraction

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doi: 10.1130/0091-7613(1997)025<0591:RIMAEI>2.3.CO;2
Authors:Connolly, J. A. D.; Holness, M. B.; Rubie, D. C.; Rushmer, T.
Author Affiliations:Primary:
Swiss Federal Institute of Technology, Institute for Mineralogy and Petrography, Zurich, Switzerland
University of Edinburgh, Edinburgh, United Kingdom
Bayreuth University, Bayreuth, Federal Republic of Germany
University of Vermont, Burlington, VT, United States
Volume Title:Geology (Boulder)
Source:Geology (Boulder), 25(7), p.591-594. Publisher: Geological Society of America (GSA), Boulder, CO, United States. ISSN: 0091-7613
Publication Date:1997
Note:In English. 30 refs.; illus., incl. 1 table
Summary:Melting reactions can create melt overpressure that may induce microcracking. To determine whether such microcracking can enhance rock permeability and melt extraction, we have studied the partial melting of a muscovite-bearing metaquartzite at 800 MPa and 950-1126 K. Melting begins at muscovite-quartz grain boundaries and results in progressive replacement of muscovite by melt pools containing mullite and biotite. The volume change for the reaction (0.021 m3 per m3 of original rock) generates randomly oriented microcracks that emanate from melting sites. The mean crack length in two-dimensional sections is 151±5 µm and reflects the spacing between melting sites. Experiments in which quartz sand was loaded with the metaquartzite to act as a drain verified that the microcracks, together with the melt pools, form a connected network. The estimated network permeability is 10-14±1 m2, at least four orders of magnitude greater than permeabilities characteristic of regional metamorphic environments. For reaction-induced microcracking to occur, the reaction must take place on a time scale such that creep cannot accommodate the associated volume change. Our analysis suggests that that requirement can be met on regional metamorphic time scales and that reaction-induced microcracking is a feasible mechanism of permeability enhancement during partial melting and devolatilization. [R.A.H.]
Subjects:Anatexis; Cracks; Dilatancy; Experimental studies; High pressure; High temperature; Metamorphic rocks; Metamorphism; Microcracks; P-T conditions; Partial melting; Permeability; Pressure; Quartzites; Regional metamorphism; Rock mechanics; Temperature
Abstract Numbers:98M/2580
Record ID:1997056009
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
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