Description
Thirty to forty thermal water samples from southern and Baja California were analyzed tor the three elements--tin, arsenic, and antimony. Tin was essentially undetected in the waters analyzed, leading to no conclusions other than Sn is not soluble in these waters. Only two occurrences of antimony were detected--Warner Springs and San Juan Hot Springs. The best explanation of these two anomalies is the probable presence at depth of antimony-bearing rock bodies. The transport of the Sb to the surface is thought to be accomplished by a combination of relatively high flow rate, high surface temperatures, and high hydrogen sulfide concentrations. Arsenic is present in thirty-five of forty thermal waters sampled. Concentrations range from 4 to 105 mg/l As. The higher concentrations were found along the San Andreas fault and are believed to be the result of chemical weathering of arsenic-bearing sulfides in the thermal waters reservoir rocks. Chemical correlations were found between arsenic and surface temperatures, sulfate, fluoride, and hydrogen sulfide. The potential of As as a geothermometer, at temperatures below l50°C, is doubtful.
