INFLUENCE OF OCEANIC TEMPERATURE ON THERMAL CONDUCTIVITY OF ROCKS IN THE SOUTHWEST SUB-BASIN OF SOUTH CHINA SEA

The influence of temperature on thermal conductivity of rocks is an important research topic in earth sciences. On the basis of previous experiments on thermal conductivity of rocks, we further solved nonlinear differential heat conduction equation with numerical methods, and then estimated the coefficients of reciprocal, linear and exponent thermal conductivity-temperature models in this paper. After that, based on the above postulated models and related actual crustal data of the Southwest Sub-basin in the South China Sea, we constrained Moho depths and explored the correlations between seafloor heat flux and Moho temperature using thermal simulation and inversion methods. The results indicate that the coefficients that constituted the reciprocal or linear model were linearly related, while the coefficient relationship in the exponent model was more according to quadratic polynomial fitting form. By that way, we can simplify the model expression and make a further step towards the quantified expression about thermal conductivity and temperature. Through comparing the results of numerical simulation and experimental statistics, we obtained that the crustal thickness of Southwest Sub-basin was 14~16 km, and according to the inversion results about model coefficients we drew another conclusion that seafloor heat flux and Moho temperature was positively related when thermal conductivity was influenced by temperature. When seafloor heat flux is 100~125 mW/m² and Moho depth is 10.3 km, Moho temperature of Southwest Sub-basin is 420~540℃; Moho temperature increases with Moho depth, being as large as 600~1 000℃ when Moho depth increases to 14~16 km.