Thermal conductivity of Higher Himalayan Crystallines from Garhwal Himalaya, India

We report the measurements of thermal conductivity for some Higher Himalayan Crystalline rocks from Joshimath and Uttarkashi areas of the Garhwal Himalaya. Seventy-three rock samples including gneiss, metabasic rock and quartzite were measured. Gneissic rocks, which include augen gneiss, banded gneiss, felsic gneiss and fine-grained gneiss, exhibit a wide range in conductivity, from 1.5 to 3.6 Wm− 1K− 1 for individual samples, and 2.1 to 2.7 Wm− 1K− 1 for the means. Among these, augen gneisses and banded gneisses show the largest variability. Of all the rock types, quartzites (mean 5.4 Wm− 1K− 1) and metabasic rocks (mean 2.1 Wm− 1K− 1) represent the highest and lowest mean values respectively. The range in conductivity observed for gneissic rocks is significantly higher than that generally found in similar rock types in cratonic areas. The rock samples have very low porosity and exhibit feeble anisotropy, indicating that they do not contribute to the variability in thermal conductivity. Besides variations in mineralogical composition, the heterogeneous banding as well as intercalations with metabasic rocks and quartz veins, a common occurrence in structurally complex areas, appears to cause the variability in conductivity. The study therefore brings out the need for systematic characterization of thermophysical properties of major rock types comprising the Himalayan region for lithospheric thermal modeling, assessment of geothermal energy and geo-engineering applications in an area. The dataset constitutes the first systematic measurements on the Higher Himalayan Crystalline rocks.