Thermal conductivity and radioactive heat-producing element content determinations for rocks from Zhangzhou region, SE China, and their constraints on lithospheric thermal regime

Radioactive heat-producing element content and rock thermal conductivity together with rock density have been determined for rocks from surface and drilling holes within Zhangzhou region, SE China. The results suggest that the average radiogenic heat production rate of granites is 3.70 μW/m³, markedly higher than that of middle-acid volcanic rocks, mafic dykes and sedimentary rocks from the same region. Additionally, the main heat production rate is sourced from the decay heat of U and Th with ⁴⁰K thermal contribution being less than 10 %. The average rock thermal conductivity is 2.83 W/mK, approaching that of the middle-upper crustal rocks. Our new data, in combination with previous geology, geophysics and geothermics data, indicate that mantle contributes more heat flow than crust to the surface heat flow, i.e., Qm/Qc > 1, and that Zhangzhou region has a relatively thinner crustal thickness.