Thermal expansion and inferred permeability of climax quartz monzonite to 3000C and 27.6 MPa

The coefficient of linear thermal expansion (α) has been evaluated for Climax Stock quartz monzonite at effective pressures (P) of 0, 13.8 and 27.6 MPa (0 to 276 bars) and at temperature (T) from 19 to 3000C. The samples evaluated were deliberately chosen to include imperfections such as healed fractures and large phenocrysts characteristic of the Climax pluton near the site of a highlevel waste repository demonstration test at the Nevada Test Site. Values for α are neither constant with nor a simple function of T or P. For the range of T investigated, α ranges from 10 to 15.10-60C-1 at 0 MPa, from 7 to 13.10-60C-1 at 13.8 MPa, and from 7 to 12.10-60C-1 at 27.6 MPa. These values of α are greater than those expected for a similar but crack-free rock. Observations on the heated rock indicate that the thermal expansion is accompanied by new microcrack formation. At the temperatures to be expected in the wall rock near a waste canister, this increase in crack porosity is inferred to increase local permeability by factors of 2 to 5