DELINEATION AND CHARACTERIZATION OF CENTRAL TEXAS MINERALIZED SPRINGS

Mineralized springs in the Central Texas, including Burnet, Lampasas and San Saba Counties, contain high total dissolved solids with minor thermal signatures, minor acidity and associated hydrogen sulfide degassing. Freshwater springs with normal karst physicochemical compositions are common throughout the region, while mineralized springs appear to be largely random. Mineralized springs exhibit minor correlation to localized brittle deformation but no consistent trends are evident. Mineralized springs include Sulphur Spring, Sulfur Springs, Hancock Spring and Hannah Spring, all on the northern region of the Llano Uplift in Ordovician and Cretaceous carbonate strata, indicating no consistent associations with lithology.

The lack of consistent structural and lithologic associations coupled with the spatial distribution of mineralized springs indicates that these springs are associated with deep-seated circulation systems. Oxidation of sulfide minerals (e.g. galena, sphalerite and pyrite) associated with the Central Texas Lead District is the likely source of hydrogen sulfide and high total dissolved solids associated with mineralized springs. Sulfate-reducing bacteria identified at spring sites indicate a component of microbially-mediated diagenesis. Current research is focusing on characterizing the source and spatial distribution of mineralized fluid circulation in the Central Texas region.