New Mexico Geological Society Annual Spring Meeting — Abstracts

A number of areas within New Mexico have geothermal gradients which seem to be altered by the movement of ground water, or possibly magma and other hydrothermal fluids. Along the Rio Grande rift many high heat flow sites are in proximity to large normal faults, cauldron boundaries, and possible zones of crustal weaknesssites near volcanic boundaries where heat flow exceeds 300 mWm^-2 may be found in the southern, central, and northern parts of the rift at San Diego Mountain, Socorro Peak, and the Valles Caldera, respectively. In the Albuquerque-Belen Basin a northeast-southwest zone of relatively high heat flow (~100 mwm^-2 ) appears to cut across a region of intermediate background heat flow (~80 mWm^-2). Along the southern boundary of the Colorado Plateau, west-central New Mexico, high heat flows are concentrated within 5-6 km of fracture zones. The crustal fractures in these areas seem to act as avenues for ground water, magma, or possibly other hydrothermal fluids to advect heat upward. Considering the magnitude and timing of the apparent igneous activity it would seem necessary that ongoing heat transfer processes are operating in order to cause the observed high heat flows. In the San Juan Basin coal maturation is believed to be influenced by ground-water movement advecting heat from probable sources in the northern basin or the San Juan volcanic field. Conduction alone appears to be insufficient to maturate coals in the central basin to observed maturation levels (this includes consideration of reasonable increased burial depths). In the Socorro area the observed heat flow pattern, high in the east and low in the west, appears to result from ground-water flow controlled by the geology of the area. Preliminary estimates of heat flow in the northwest shelf of the Permian Basin indicate higher values at shallow depths than at deep depths for about 30 km on either side of the Pecos River. From this observation we suggest that ground water is flowing upward from below ~1000 m, and probably recharging to the Pecos River. The Jornada del Muerto in the south-central Rio Grande rift is an area of high heat flow (background about 95 mWm^-2) and relatively thin crust, with little evidence of synrift extension, volcanism, or tectonism. These facts may be implicit evidence for crustal thinning by upper mantle-lower crustal convection.