Indications of Spatial Associations between Deep-seated Groundwater Flow systems and Thermal Springs in Paleozoic Sedimentary Basins of Brazil

We present evidences indicative of the existence of spatial associations between deep lateral flow systems of groundwater and geographic distributions of thermal springs in several of the Paleozoic interior basins of Brazil. Specifically, thermal springs are found to be absent in regions inferred to have deep seated lateral flows of groundwater. This trend is remarkably evident in the basins of the Amazon region, in the central parts of the Parnaiba basin and in the west-central parts of the Parana basin. We also report progress obtained in model studies of processes responsible for mutual exclusion of regions of thermal springs and lateral flows of groundwater. Results of numerical simulations indicate that lateral flows are potentially capable of masking the occurrences of thermal anomalies. Also, lateral flows lead to development of large low temperatures zones, capable of suppressing surface manifestations of deep geothermal resources. Analysis of Peclet - Rayleigh domains of flow systems indicate that lateral movements are capable of obliterating the effects of thermal buoyancy. We conclude that an understanding of the perturbing effects of subsurface flow systems is important in assessment of geothermal resources.