Temperature-dependent thermal transport properties of carbonate minerals and rocks

To address thermal processes involving carbonate rocks, we measured thermal diffusivity (D) of a suite of carbonate minerals and rocks using laser flash analysis at temperatures from ∼300 K up to ∼1000 K. For different minerals, D was governed by density or unit cell size. Near room temperature, for example, D ranged from 4.36 mm2 s–1 for magnesite to 1.61 mm2 s–1 for calcite. At any given temperature, D decreases from magnesite to dolomite to rhodochrosite to calcite. As temperature increases, D decreases for all samples, with the strongest drop occurring in the interval ∼300–500 K. For rocks, mineralogy and porosity were also strong controls on rock D. Calcitic limestones showed proportionally lower D than the mineral, scaling with measured pore fraction, whereas dolomitized rocks produced higher D than calcitic rocks across the interval 300–600 K. Measurements of heat capacity and density were used to calculate thermal conductivity (k) for the suite, and these results show a stronger temperature dependence for k of carbonate rocks and minerals than previous studies, with k decreasing by ∼50% between ambient and ∼600 K.