Experimental deformation of synthetic aragonite marble

Abstract

We deformed synthetic polycrystalline aragonite aggregates in a Griggs-type apparatus using a molten salt cell at temperatures between 600 and 900?C, confining pressures between 1.6 and 2.8 GPa, and strain rates between 3 ? 10-6 and 5 ? 10-3 s-1. At temperatures above 600?C, triaxial compression tests to ?15% axial strain are characterized by a constant flow stress. The strength of the aragonite marble is comparable to strength data previously published for calcite rocks of comparable grain size, i.e., 50 to 100 ?m. The mechanical data and microstructures of the deformed aragonite specimens indicate dislocation creep as the dominant deformation mechanism. A power law flow law, ?? = ?exp(-QIRT)?n, fits the mechanical data with a preexponential factor In(A[MPa-5.2 s-1]) = -0.6 ? 2.5, an activation energy Q = 249 ? 29 kJ mol-1, and a stress exponent n = 5.2 ? 0.6. Extrapolated to natural strain rates, the flow law provides an upper bound to the strength of carbonate rocks at (ultra-) high-pressure metamorphic conditions.