Comparison of fluid inclusion decrepitation and acoustic emission profiles of Westerly granite and Sioux quartzite.
Tectonophys 1989 Nov; 168(4):283-296
Acoustic emissions recorded during slow heating of rocks at 1 atm have generally been attributed to intergranular stresses generated by differences in thermal expansion coefficients and elastic moduli of neighboring grains. Only the solid phases have been considered, and little attention has been given to the role of intragranular or grain boundary fluid inclusions in initiating or facilitating fracturing. Samples of Westerly granite (wg) and Sioux quartzite (sq) were heated at 2 deg. C/min in a gas-flow stage in order to determine the decrepitation profiles (number of decrepitations as a function of temperature) of these rocks. Four types of inclusions were noted in wg and one type in sq. Decrepitation profiles found display many similarities and differences when compared with previously published acoustic emission profiles of wg and sq. Owing to fundamental differences in the techniques used to measure acoustic emission and decrepitation, it is unclear whether decrepitating fluid inclusions are recorded during acoustic emission studies. However, if they are, our studies suggest that (1) decrepitation contributes more to low-temperature than to high- temperature acoustic emissions for both wg and sq, (2) a larger percentage of acoustic emissions in the low-temperature decrepitation profile is due to fluid inclusions for sq than for wg, and (3) decrepitation fluid inclusions, not stresses generated by solid-solid interactions, cause the majority of intragranular fracturing in quartz below the a-b transition in both wg and sq.
Stone-processing; Stone-products; Fluids; Fluid-mechanics; Acoustics; Acoustic-absorption; Acoustical-measurements
Donald L. Hall, Department of Geological Sciences, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061 (U.S.A.)
OP; Journal Article
MIR 28-90; Grant-Number-G1164151
Virginia Polytech. Institute