Radiative heat transfer in molten and glassy obsidian

Journal Article · Fri Aug 10 00:00:00 EDT 1984 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JB089iB08p07107· OSTI ID:6409608

Gable, C W; Shankland, T J

We have measured optical transmittance spectra in rhyolitic obsidian samples in the wavelength range lambda = 380-5500 nm and at temperatures T from 19/sup 0/-1145/sup 0/C, above and below the softening point. From the transmittance, we calculated the absorption coefficient ..cap alpha..(lambda,T) and the radiative thermal conductivity K/sub R/(T). K/sub R/ ranges from 3 x 10/sup -3/ cal cm/sup -1/s/sup -1/K/sup -1/ (1.2Wm/sup -1/K/sup -1/) at 700/sup 0/C to 12 x 10/sup -3/ cal cm/sup -1/s/sup -1/K/sup -1/(5Wm/sup -1/K/sup -1/) at 1145/sup 0/C. The 700/sup 0/C value is comparable with lattice thermal conductivity K/sub L/ of about 4 x 10/sup -3/ cal cm/sup -1/ s/sup -1/K/sup -1/(1.7 Wm/sup -1/K/sup -1/). Removing scattering effects due to bubbles from the transmittance spectra by lowering the absorption baseline increased K/sub R/ to 20 x 10/sup -3/ cal cm/sup -1/ s/sup -1/ K/sup -1/(8.4Wm/sup -1/K/sup -1/) at 1145/sup 0/C. Because scattering bubbles is likely to be small in confined magmas, these numbers are probably minimum values for K/sub R/ and indicate that in active plutons radiative heat transport could be greater than lattice conductivity by more than a factor of 2 at 1000/sup 0/C. Thus melting markedly strengthens K/sub R/, and radiative heat transport is probably the dominant component of the total conductivity K = K/sub L/+K/sub R/ in silicic magmas. These relatively large values of K can be applied to models of the thermal evolution of magma bodies and to cooling of intrusives.

• Research Organization: Department of Geology and Geophysics, University of California, Berkeley
• OSTI ID: 6409608
• Journal Information: J. Geophys. Res.; (United States), Vol. 89:B8
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
RHYOLITES
RADIANT HEAT TRANSFER
HIGH TEMPERATURE
MEDIUM TEMPERATURE
OPACITY
SPECTRA
TEMPERATURE DEPENDENCE
THERMAL CONDUCTIVITY
THERMAL RADIATION
VERY HIGH TEMPERATURE
ELECTROMAGNETIC RADIATION
ENERGY TRANSFER
HEAT TRANSFER
IGNEOUS ROCKS
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
RADIATIONS
ROCKS
THERMODYNAMIC PROPERTIES
VOLCANIC ROCKS
580300* - Mineralogy
Petrology
& Rock Mechanics- (-1989)