S. Karato et al., EXPERIMENTAL STUDIES OF SHEAR DEFORMATION OF MANTLE MATERIALS - TOWARDS STRUCTURAL GEOLOGY OF THE MANTLE, Pure and Applied Geophysics, 151(2-4), 1998, pp. 589-603
A brief outline is given on experimental studies carried out in the Mi
nnesota Mineral and Rock Physics Laboratory of microstructural evoluti
on and rheology of mantle mineral aggregates or their analogues, using
a simple shear deformation geometry. A simple shear deformation geome
try allows us to unambiguously identify controlling factors of microst
ructural evolution and to obtain large strains at high pressures and t
emperatures, and thus provides a unique opportunity to investigate the
''structural geology of the mantle.'' We have developed a simple shea
r deformation technique for use at high pressures and temperatures (pr
essure up to 16 GPa and temperature up to 2000 K) in both gas-medium a
nd solid-medium apparati. This technique has been applied to the follo
wing mineral systems: (i) olivine aggregates, (ii) olivine basaltic me
lt, (iii) CaTiO3 perovskite aggregates. The results have provided impo
rtant data with which to understand the dynamics of the earth's mantle
, including the geometry of mantle convection, mechanisms of melt dist
ribution and migration beneath mid-ocean ridges, and the mechanisms of
shear localization. Limitations of laboratory studies and future dire
ctions are also discussed.