Elastic moduli, thermal expansion, and inferred permeability of Climax quartz monzonite and Sudbury gabbro to 500/sup 0/C and 55 MPa

Abstract

Young's modulus (E), bulk modulus (K), and the coefficient of thermal linear expansion (..cap alpha..) have been determined for Climax quartz monzonite to 500/sup 0/C and pressures (P) to 55 MPa and for Sudbury gabbro to 300/sup 0/C and 55 MPa. For each rock, both E and K decreased with T and increased with P in a nonlinear manner. In the monzonite, E and K decreased by up to 60% as P decreased from 55.2 to 6.9 MPa isothermally, while the gabbro indicated a decrease up to 70% over the same pressure range. As T increased isobarically, E and K for the monzonite decreased by up to a factor of approx. 80% from 19 to 500/sup 0/C. The moduli of the gabbro decreased by as much as 70% from 19 to 300/sup 0/C. ..cap alpha.. for the monzonite increased with T and decreased with P in a nonmonotonic fashion, with most measured values for ..cap alpha.. greater than values calculated for the crack-free aggregate. Depending on P, ..cap alpha.. in the monzonite increased from 8 to 11.10/sup -6/ /sup 0/C/sup -1/ at 40/sup 0/C to 22 to 25.10/sup -6/C/sup -1/ at 475/sup 0/C. For the gabbro, ..cap alpha.. also generally decreased with increasing P. Values ranged from 6 to 11.10/sup -6/ /sup 0/C/sup -1/, showing a nonlinear trend and very little net increas over the T range from 19 to 300/sup 0/C. Calculated permeability of these rocks based on the ..cap alpha.. determinations indicated that permeabilities may increase by up to a factor of 3 over the temperature interval 19 to 300/sup 0/C, and the permeability of the monzonite is inferred to increase by up to a factor of 8 by 500/sup 0/C. In both rocks, most measurements are consistent with microcracks controlling the thermoelastic response by opening with T and closing with sigma and P.