The evaluation of the temperature distribution in the mantle from geomagnetic,
geoelectric, and magnetotelluric data requires detailed information on
the electrical conductivity of the constituent minerals. In addition, electrical
properties of minerals and rocks are used in studies of electronic and
ionic transport processes, defect chemistry, and other mineral physical
properties. Until now, accurate measurements of electrical conductivity
at high pressure and high temperature have been difficult. We are attempting
to overcome the previous experimental difficulties by reducing leakage
current caused by pressure medium, lead wires, and reaction products (between
pressure medium and sample), and to control oxygen fugacity. The aim is
to measure the electrical conductivity of Earth's minerals and rocks in
the multianvil apparatus up to 25 GPa and 1600°C under controlled conditions.
We will determine the mantle geotherm by using the laboratory conductivity
data of the most abundant mantle minerals and rocks, including olivine
( ), modified spinel (
), spinel(
), perovskite, and peridotite.