New Mexico Geological Society Annual Spring Meeting — Abstracts

New Mexico geothermal systems, with the exception of that in the Valles caldera, are considered by many to be small in size and adjective. New Mexico warm springs do not resemble circum-Pacific, volcanic-rock-hosted geothermal systems in discharge temperatures, an association with large, low-conductivity anomalies, nor in a temporal association with volcanism. However, quartz and cation geothermometry indicates subsurface water temperature well above 100 C, and in some cases > 200 C, for a large number of thermal springs that discharge 30 to 60 C waters. Examples are the Gila Springs, Grant Country; Hillsborro Warm Springs, Sierra County; Bosque del Apache Well #13, Socorro County; and Ojo Caliente, Taos County.

There is a remarkable similarity between New Mexico warm-spring gas chemistry and New Mexico Fluorite-Pb-Barite-Mn-W mineral deposit fluid-inclusion-gas-chemistry. Fluid inclusion microthermometry studies of the mineral deposits commonly indicates maximum temperatures > 150 C. The few detailed isotopic studies performed on these deposits show no evidence for a magmatic contribution to the ore solutions. Evidence of fluid boiling and stratigraphic reconstruction constrain mineralization depths to less than 1.5 km. Hence, the paleo record tells us that non-magmatic, 150+ C geothermal fluids were present at depths of 1.5 km or less throughout portions of the State affected by basin and range tectonics. Warm-spring gas chemistry and chemical geothermometry suggests that the springs may represent surface expressions of fluids systems similar to those that formed mineral deposits in the past. If this is true, there are serval implications from our knowledge of past geothermal systems. Fluid migration is structurally controlled, fluids have little H₂S, alteration is minimal, and the size may be large. The size of the mineralized districts, like those at Luis Lopez and Hansonburg, suggest the volume of hot waters could be equal to that of the largest volcanic-hosted geothermal systems. Hot waters at depth may remain hidden because of the lack of clay-mineral alteration does not allow detection by electrical methods; mixing with near surface waters limits the thermal anomaly; and the solutions do not have driving force characteristic of volcanic-hosted geothermal systems that have near 300 C temperatures and high gas contents. Mechanisms for amagmatic geothermal fluid=flow are not clear. Some proposed mechanisms for mineralizing fluids in other states and countries call on tectonic forced, other differential heat flow between basins and basin margins, both of which are compatible with basin and range tectonics and geology.

New Mexico geothermal fluids may be a much more significant resource than here-to-fore considered.