Can Dihedral Angle Measurements be Used to Determine Textural Equilibrium?
M. T. Elliott (mikee@liv.ac.uk) & M. J. Cheadle (mjc44@liv.ac.uk) Jane Herdman Labs., Department of Earth Sciences, University of Liverpool, Brownlow Hill, Liverpool L69 3BX. The identification of textural equilibrium in igneous and metamorphic rocks can provide important information about the physical conditions and processes that affected the rocks during their formation. In particular, fluid distribution and hence permeability in a crystallizing rock is governed by the degree of equilibrium attained. The current practice for assessing textural equilibrium is to measure the dihedral angle; this is the angle between the tangents to the grain boundaries where three grains meet or where two grains and a fluid meet. These measurements are then compared with theoretically predicted measurements for a totally equilibrated texture. If the measurements match, then the texture is said to be equilibrated. However, if there is a mis-match little can be deduced about the degree of equilibrium be
