| Abstract |
Quantitative mineralogical studies of over 1,000 cores and cuttings from 31 wells drilled in a 2x3 km area of the Ahuachapan, El Salvador, Geothermal Field, together with structural and volcanological observations, have shown that geothermal fluids originating beneath the recent volcanics to the south of the field rise from the depth along open sections of the Southern Boundary Fault of the Central Valley. Their rise is hindered at a certain level by the volcanic products themselves. The fluid flow is thus forced to alter course along transverse NNW-SSE faults which intercept the Boundary Faults beneath the volcanics and to a lesser extent, along fractured horizons of the Ahuachapan Andesites. The fluids veer northwards along these new channelways, moving along two major NNW-SSE faults, with minor flows along other parallel faults and along the horizon of Ahuachapan Andesites. As the masses move north, a further hindrance is caused by an E-W fault acting both as a barrier to the northerly flow and as a channellway to any E-W and W-E flows. The result is that the water masses mix along this EW fault plane and its parallel equivalents. Reduced in mass and temperature, the fluid finds further conduits to the north along other open sections of the NNW-SSE faults. The flow is finally hindered by ever decreasing opening size along the faults and by an opposed influx of cold waters from the north. |