I need to know/research the effect of thermal modification of devonic rocks and it's effect on ERT results. Particularly devonic rocks that have been covered by massive basalt and tuff layers show different resistivities than ecpected. Talking 50 to 100m of very very high resistivity until the expected low resistivities begin.
It could be the case that the rocks have metamorphosed, deformed and fractured intensely. The reduction in electrical resistivity values of basement or hard rocks is an indication of fracturing.
Several factors exist that affects the resistivity of the rock. For example in the fractured zones, the enrichment in clay decrease the resistivity and the water content too. On the other hand alterations like: argilitic and phyllic can decreases, and propilitic increase.
It could also be the case that the basaltic mass overlies a sedimentary formation. Usually, basalts show relatively high resistivities especially when dry. So the drop in electrical resistivity at depths beyond the basaltic shield could result from the sedimentary formation which probably may have been thermally modified.
- Badges
- Science topic