Thermal properties of basalts from the Bouvet triple junction and their implications for petrophysical characteristics

Thermophysical characteristics of the oceanic basalts and their implication s for the structure and composition of the rocks are studied for the first time using a representative collection of samples dredged in the area of th e Bouvet triple junction, Southern Atlantic. The structural factor (grain s ize and amount of the amorphous component) is shown to have a predominant e ffect on the thermal conductivity and diffusivity of basalts. The results a re discussed in terms of the microscopic theory of thermal conductivity. Th e conclusion on the mechanism of the structural effect on the intensity of heat transfer in effusive rocks is drawn. The thermal diffusivity is shown to be independent of the porosity within the groups of study basalts that a re similar in composition and structure and range in porosity from 0 to 35% , and this phenomenon is interpreted within the framework of the theory of thermal conductivity of solids. Based on this effect, a simple procedure is proposed for extrapolating the thermal conductivity in a porous medium to a zero porosity. This technique was utilized in studying the influence of t he amorphous phase concentration on the thermal conductivity of oceanic bas alt glasses. The results obtained are applicable to the study of the therma l conditions in the oceanic lithosphere under the Bouvet triple junction an d to the thermal physics of rocks and composite materials.