Evidence for intergranular fluid films in the lower crust and uppermost mantle from HRCT and crystal surface microtopography of xenoliths

Abstract

We have examined lower crustal and uppermost mantle xenoliths from the Ichinomegata Maar and found the characteristic microtopography of two dimensional crystal surfaces such as growth steps, growth hills and etch pits. We also found by using an X-ray micro tomography that two dimensional, film-shaped pores are common, especially in the interphase boundaries, and that they are well interconnected. These observations show that interconnected fluid films exist in the lower crust and uppermost mantle, being responsible for the high electrical conductivity that was required from MT observations.