Circular 83 — Chemical Characteristics of New Mexico's Thermal Waters – A Critique

By W. K. Summers, 1965, 36 pages.

As part of a preliminary report on the geothermal energy resources of New Mexico, chemical analyses of thermal water (65°F or higher) and thermal wells (75°F or higher) were compiled. This paper summarizes the data available on waters 90°F or greater and discusses their significance and shortcomings.

The thermal waters of New Mexico are located along faults and generally can be related to nearby igneous rocks of Tertiary or Quaternary age. Many of the thermal waters are related to the faults at the margin of the Rio Grande trough. The discussion of the chemistry of thermal water is limited to those waters with temperatures of 90°F or more because this temperature seems to mark a lower limit of thermal anomaly.

These waters are sodium-rich with chloride, sulfate, bicarbonate, bicarbonate-sulfate, and bicarbonatechloride. Fluoride concentrations range from 0 to 24 ppm (parts per million) and are generally higher than in nonthermal waters.

The pH of the thermal waters is usually greater than 7.0, but at Sulphur Springs and Alamo Canyon Spring, the pH is low-2.0 and 2.9. At these springs, aluminum and hydrogen are the principal cations and sulfate is the anion. Chemical analyses of water from Sulphur Springs show many inconsistencies.

Unusual concentrations of boron occur at Soda Dam Springs and at Jemez Springs, and unusual concentrations of radium occur at Faywood Hot Springs.

The thermal waters at Truth or Consequences are sodium-chloride waters and are amazingly uniform in chemistry, whether the water issues as springs from the alluvium or is intercepted by wells penetrating the limestone.

Some of the thermal springs have built large travertine deposits; others (with similar chemical make-up) have not. Some of the springs show remarkable uniformity in discharge and temperature; others fluctuate over a wide range. Some of the thermal waters are clearly warmed meteoric waters; others may have a component of juvenile water. Some thermal waters have circulated to only shallow depths, whereas others have circulated to depth—possibly great depth.

Although the available data reveal much about the character of the thermal waters of New Mexico, they leave much to be desired for a geological interpretation of the hydrothermal process, because the analyses were made largely from the standpoint of water supply. The available data do not answer many questions relating to the active hydrothermal process; yet, such data may lead to a complacency that bodes ill for understanding of the hydrothermal process in New Mexico.