CONCEPTUAL MODEL FOR BOKU HYDROTHERMAL AREA (NAZARETH), MAIN ETHIOPIAN RIFT VALLEY

Abstract

In tectonically active areas, fractures of various extent playa very important role in groundwater circulation and storage, increasing also the permeability of rocks. Since hot springs are generally non-gravity types, tectonic discontinuities act as a vertical pipe line for zenithal flow of thermal water and steam. On the Baku rhyolite ridges, active deep faults tap steam from high thermal anomaly area to the surface. Tension and laminar fractures within the rhyolite flow foliation structure increase the vertical permeability of the rock and the discharging surface area. The applied conceptual model has shown that the
major deep aquifers are within the floor complex ignimbrites overlain by rhyolite lava domes. By using a simple mathematical equation, the minimum theoretical depth of the provenance of thermal water has been determined (about 400 m) which could be taken as the minimum depth of open fractures that act as conduits for hydrothermal fluids.