Thermal properties of rocks

Abstract

All the important thermal properties of rocks can be estimated from the graphs and tables in this report. Most of the useful published data are summarized herein to provide fairly accurate evaluations of thermal coefficients and parameters of rocks for many engineering and scientific purposes. Graphs of the published data on common rocks and minerals were prepared to show the relationships of thermal conductivity with decimal solidity (one minus decimal porosity), water or air pore content, content of certain highly conducting minerals, and temperature. Tables are given of pressure effect on thermal conductivity of minerals and rocks, anisotropy of conductivity, thermal expansion, heat transfer, density, heat generation in rocks, and activation energies of conduction mechanisms in single crystals of minerals. A series of graphs show the specific heats of rock-forming minerals as a function of temperature; with these graphs the specific heat of a rock can be calculated from its mode as accurately as it can be measured. Calculations of conductivity, diffusivity, and thermal inertia of a rock from its mode are described. Discussions of radiative thermal conductivity, radioactive heat generation, and heat transfer in rocks are provided. The best published compilation of thermal conductivities of rocks is in the tables of Clark (1966, section 21). The theory of conduction of heat is described for geologic purposes by Ingersoll and others (1954), and the classic treatise is by Carslaw and Jaeger (1959). The basis for the graphs of conductivity shown hereafter is the finding for vesicular basalt by Robertson and Peck (1974) that thermal conductivity varies as a function of the complement of porosity squared, air or water pore saturation, and content of highly-conducting phenocrysts. Thermal conductivity is given emphasis in this compilation because it is needed in all calculations involving heat conduction in the earth. (An earlier compilation is in Robertson, 1979.) In figures 1-13 the effects of porosity, water content, and quartz, olivine, pyroxene, and clay content on conductivities of most felsic and mafic rocks are shown. Data for other less-common igneous rocks are listed in table 1. Anisotropy data for metamorphic rocks are given in table 2. The effect of temperature on conductivity is shown for the common rocks in figures 14-19 and for rock-forming minerals in figures 21-26. Conduction mechanisms and activation energies as a function of temperature in mineral crystals and aggregates are considered in the text associated with figures 28 and 29 and tables 3-5; however, the data on conduction mechanisms in rocks are still inaccurate. The available data on the effect of pressure and vacuum on conductivity of rocks and minerals are given in tables 7 and 8. The conductivities of most of the common minerals, both single crystal and polycrystalline, are given in an accompanying open-file report of Diment and others (1988), as well as in Horai (1971) and in Clark (1966, Sec. 21). Thermal expansions (from Skinner, 1966),...

Factors Affecting the Thickness of Thermal Aureoles

“…Wang and Manga (2015) show that hydrothermal convection induces complexlyshaped thermal aureoles. Diffusivities decrease with temperatures (Robertson, 1988;Whittington et al, 2009). As a magma cools down and transfer heat to its surrounding, the magma diffusivity increases and the country rock diffusivity decreases.…”

“…The thermal conductivity of a rock is the sum of the conductivities of its minerals (Robertson, 1988). Porous rocks that are poor in quartz and contain water or air in pores are the most insulating (Robertson, 1988). They are most FIGURE 10 | Aureole thickness induced by an incrementally growing magma body as a function of the time interval between magma increments.…”

“…Heat is transferred more rapidly within the intrusion than through the country rock if the country rock is insulating or if the magma is convecting. The thermal conductivity of a rock is the sum of the conductivities of its minerals (Robertson, 1988). Porous rocks that are poor in quartz and contain water or air in pores are the most insulating (Robertson, 1988).…”

Ambient effects on basalt and rhyolite lavas under Venusian, subaerial, and subaqueous conditions

“…The present abundance of water in Venus' atmosphere is very low relative to Earth, but this probably was not the case in the past. The greenhouse effect on Venus strongly suggests that the atmosphere was once wetter than it is today [Shimazu and Urabe, 1968 Submarine tholeiitic basalts generally contain-0.1-0.5 wt % H20 [Moore, 1965[Moore, , 1970 [Robertson, 1988] and should show a similar dependence on vesicularity. A more useful thermal parameter is the thermal diffusivity, <, which controls the rate at which temperature changes in a conductively cooling body.…”

“…Therefore, diffusivities of basalt and rhyolite used in the subsequent thermal analyses are assumed to be the same in the three environments and are taken as 6 and 7.5 x 10 '7 m2's -1, respectively [Peck et al, 1977, Williams and McBirney, 1979]. Specific heat is taken as 1200 J kg -1 K -1, a common value for both felsic and mafic rocks [Robertson, 1988]. Thermal conductivity is encapsulated within the thermal diffusivity term (<), where as discussed above, its proportionality with density nullifies its effect.…”