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[S24-P-06] Thermal conductivity variation of granites at elevated temperatures
The knowledge of the downward variation of thermal conductivity (TC) within Earth's interior is an important key parameter to estimate the sub-surface temperature distribution accurately. The depth wise variation is dominantly controlled by temperature and to less extent by the pressure. In the present study, we have measured thermal conductivity (TC) variation with temperature for 20 granite rocks from the Bundelkhand craton (BC), central India, one of the oldest cratons in the Indian shield. The BC predominantly consists of granites and gneisses, covering 80% of its areal extent. In this craton, granites exhibit three different varieties based on their geochemical composition.
Measurements are carried out in the laboratory using a steady-state apparatus (guarded heat flow meter, DTC-300) in the temperature range 25 to 300 oC. Thermal conductivity is measured at an interval of 25 oC between 25 and 100 oC and 50oC between 100 and 300 oC. Studied temperature range corresponds to a upper to middle crustal scenario. We found that for the three varieties of the granites, TC at room temperature varies between 2.3 and 3.4 W/m/K whereas TC at 300 oC varies between 1.9 and 2.2 W/m/K. Drop in thermal conductivity in the studied temperature range is significant (10 to 30%) for the all types of granite rocks. Also, this variations in TC are distinctly different among all the three varieties of granites. Moreover, within each type of granite, the drop in TC with temperature is dependent on their TC at room temp. Thus, the observed large variation in thermal conductivity with temperature indicates that the systematic study of thermal conductivity variation with temperatures for granites is essential for precise estimation of the sub-surface thermal regime.
Measurements are carried out in the laboratory using a steady-state apparatus (guarded heat flow meter, DTC-300) in the temperature range 25 to 300 oC. Thermal conductivity is measured at an interval of 25 oC between 25 and 100 oC and 50oC between 100 and 300 oC. Studied temperature range corresponds to a upper to middle crustal scenario. We found that for the three varieties of the granites, TC at room temperature varies between 2.3 and 3.4 W/m/K whereas TC at 300 oC varies between 1.9 and 2.2 W/m/K. Drop in thermal conductivity in the studied temperature range is significant (10 to 30%) for the all types of granite rocks. Also, this variations in TC are distinctly different among all the three varieties of granites. Moreover, within each type of granite, the drop in TC with temperature is dependent on their TC at room temp. Thus, the observed large variation in thermal conductivity with temperature indicates that the systematic study of thermal conductivity variation with temperatures for granites is essential for precise estimation of the sub-surface thermal regime.