Mineralogical evolution of clay-bearing rock during alkaline alteration (Khushaym Matruk, Central Jordan)

The Bituminous Marl of Khushaym Matruk (Central Jordan) is being investigated in order to identify the clays, to estimate their amounts and to investigate their reaction products when leached by hyper-alkaline fluids. The marl contains at least 9 wt% of a clay fraction (< 2 mum) which is sufficient to conduct most of the studies necessary to describe and evaluate the behaviour of clay in the presence of a propagating hyper-alkaline plume. Rock samples collected along a profile from unaltered marl to a metamorphic (i.e. natural cement) zone are being investigated using standard methods. Some indicators of the effects of alkaline perturbation have been detected. Results show that the clay is mostly a mixed-layer illite/smectite containing 80% of smectite in the unaltered marl. The smectite content of the mixed-layer varies along the profile, from 80% to 60%.