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IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy
(S) - IASPEI - International Association of Seismology and Physics of the Earth's
Interior
JSS017 Oral Presentation 2365
Thermal diffusivity of granulite rocks at elevated temperatures
Dr. Labani Ray
Heat Flow and Heat Production Study National Geophysicsl Research Institute, Hyderabad
IASPEI
H.-J. Frster, F.R. Schilling, A. Frster
The thermal diffusivity of felsic, intermediate, and mafic granulites from the South Indian Granulite
Province has been measured at elevated temperatures (up to 550 C), using a transient technique.
Measurements were carried out at intervals of 25 oC up to 100 C, and 50 oC at temperatures above 100
C. At room temperature, the thermal diffusivity of felsic and intermediate granulites ranges between 1.3
and 2.2 mm2 s− 1, whereas that of the mafic granulites ranges between 1.2 and 1.4 mm2 s− 1. The
effect of radiative heat transfer is generally observed above 450 C. Below 450 C, i.e., in the conductive
heat transfer zone, thermal diffusivity decreases between 35% and 45%. Rocks having a high thermal
diffusivity at room temperature show a greater proportional decrease in diffusivity with increasing
temperature and vice versa. The parameter, which has the greatest impact on the temperature
dependence of thermal diffusivity, is the room-temperature thermal diffusivity, which itself is a function
of the mineralogical composition of the rock. An equation has been derived for estimating thermal
diffusivity D of granulites at higher temperature (T) and pressure (P) as D = 0.7 mm2s-1 + 144 K (DRT
- 0.7 mm2s-1) x (0.1 GPa-1) / (T-150 K) + CT3 where DRT is room-temperature thermal diffusivity, T is
the absolute temperature in Kelvin, constant C varies from 10− 9 to 10− 10 depending on intrinsic rock
properties (opacity, absorption behavior, grain size, grain boundary, etc). This equation may be used in
thermal modeling of deep crustal sections involving granulitic rocks, with the room-temperature thermal
diffusivity being the only parameter to measure if heat transport by radiation can be neglected
Keywords: thermal diffusivity, temperature dependence, granulite rock