Description
Twenty-three warm spring wells from six different areas were sampled along parts of the San Jacinto and San Andreas fault zones. An additional 51 well water analyses in the studied areas were obtained from other sources. The waters were analysed for 15 different elements plus Si02 to determine: 1) if near surface mixing with local cold ground water occurs, 2) reservoir temperatures, 3) estimated depth of circulation of thermal waters, 4) water-rock reactions at depth, and 5) relationships between springs. Tritium samples were taken at each of the six areas and indicate no mixing between the ascending thermal waters and cold ground waters except for Arrowhead Springs, which was found to have a 13.5% component of cold water. Surface temperatures of the warm springs and wells range from 29°C to 85°C. Estimated reservoir temperatures vary from 48°C at Ocotillo Wells to 120°C at San Bernardino. Depth of circulation in these two areas are 0.9 km and 3.3 km, respectively, with the four other areas having intermediate values. Two of the four warm springs are sodium carbonate dominated due to water-rock reactions with originally calcium carbonate ground waters. The other two warm springs are sodium sulfate dominated and appear to be oxidized from originally sodium carbonate springs. The warm wells fall into two categories: calcium bicarbonate and sodium-calcium sulfate-chloride dominated. The different chemistries can be explained on the basis of the original recharge water and various mechanical and chemical reactions.
