1999 Fiscal Year Final Research Report Summary
Thermal conductivity measurments of earth materials under high pressure and high temperature
| Project/Area Number |
09640511
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
固体地球物理学
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| Research Institution | National Science Museum |
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Principal Investigator |
OSAKA Masahiro Department of Science and Engineering, National Science Museum, 理工学研究部, 室長 (60132693)
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| Project Period (FY) |
1997 – 1999
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| Keywords | MANTLE MATERIALS / THERMAL CONDUCTIVITY / THERMAL DIFFUSIVITY / HIGH-PRESSURE / DEEP INTERIOR OF THE EARTH |
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| Research Abstract |
To investigate the thermal state of the earth's mantle, the author measured the thermal conductivity and the thermal diffusivity of mantle candidate minerals under high pressure and at high temperature.
A pulse method using one-dimensional heat flow has been applied to simultaneous thermal diffusivity and thermal conductivity measurements. The sample, made in the form of three identical thin disks, is heated by a pulse current in a thin heater inserted into one interface of the stacked disks. Change of temperature is detected by a thermocouple on the other interface. Thermal diffusivity is determined from decay time of the temperature profile, and thermal conductivity is calculated from the rise of temperature and an electric power for the known thickness of the sample.
Experiments were performed using a uniaxial split-sphere high-pressure apparatus. A magnesia octahedron with a edge length of 18 mm was used as a pressure medium in tungsten carbide anvils with a truncation of 11 mm. Size
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s of the samples were 4 mm in diameter and 1 mm in height. A pair of metallic planar furnaces in the octahedron was used for experiments at high temperatures.
Measurements were made on fused silica, garnet and olivine under pressures up to 8.2 GPa. Extrapolated values of thermal conductivity or thermal diffusiivity to zero pressure agree with those obtained by other methods. Reproducibilities of measurements are within 7 per cent for thermal diffusively and within 15 per cent for thermal conductivity.
Pressure dependences on thermal diffusively or thermal conductivity of mantle minerals are tow or three per cent increase per 1 GPa for garnets and five per cent increase per 1 GPa for the b-axis direction of olivine.
Garnet and olivine were measured at temperatures up to 1000 K under 8.2 GPa. The thermal diffusively or the thermal conductivity of garnet decreases moderately with temperature increase unlike normal insulators in the T-inverse law of thermal conductivity. This is the same effect as seen in previous results under zero pressure. Less
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