LOOKING INTO THE EARTH'S MANTLE DEFORMATION MICROSTRUCTURES

摘要

The Earth's mantle covers the region from 30 to 2,900 km depth and represents the volumetrically most significant part of the Earth (Fig. 1). The P,T conditions reach from 1 to about 125 GPa and 800 to about 3,000 ℃. Mineralogically it consists largely of Mg,Fe,Ca,Al-bearing silicates which undergo a number of phase transitions with increasing pressure and temperature, defining the so-called mantle transition zone at a depth of about 410 to 670 km (Fig. 2) (e.g., [1]). The whole mantle is deforming due to heat driven large scale convection and seismological studies (especially the results on seismic anisotropy) indicate that deformation is particularly intense in the boundary regions at the top and the bottom of the mantle. Whereas the upper region of mantle (i.e., down to about 150 - 200 km) is at least partially accessible through rocks that have been brought back to the surface by tectonic or magmatic processes, the lower boundary region (i.e., the so-called D" layer above the liquid outer core) is completely inaccessible in terms of direct sampling.