HR: 1340h
AN: T23B-0561    [Abstracts]
TI: Modification of the Semicircular Tube Aquifer Model by Including Water Geochemistry Temperature Constraints to Evaluate Geothermal Potential: An Example From the Clifton Hot Springs, in the Southeastern Quadrant of Arizona
AU: * Morgan, P
EM: Paul.Morgan@nau.edu
AF: Northern Arizona University, Department of Geology, Box 4099, Frier Hall, Knoles Drive, Flagstaff, AZ 86011-4099 United States
AB: Lack of young volcanism associated with hot spring where these thermal manifestations are associated with significant topographic relief and young faulting, indicates that the thermal waters may be heated by deep circulation driven primarily by piezometric (natural water table) gradients. If the deep circulation is dominated by fracture control, a useful first order simplification of the flow for thermal modeling is that of a vertical semicircular tube in a homogeneous medium, with the inlet slightly higher than the outlet, and uniform thermal gradient increasing downward (Turcotte and Schubert, Geodynamics, 2nd e., 2001, p. 264). This model may be further constrained using water temperature data derived from water geochemistry data. These data may be used to estimate the maximum temperature to which the water was heated in its passage through the system, which, combined with its outflow temperature may in turn be used to determine a dimensionless flow rate number in terms of the thermal gradient and the parameters of the semicircular tube. This technique has been applied to the Clifton Hot Springs, located adjacent to the San Francisco River, north of the town of Clifton, in Safford County in the southeastern quadrant of Arizona. The springs are in a valley in rugged topography on the southern margin of the Colorado Plateau, providing gravitational gradients driving the flow through the systems, and regionally high heat flow provides a high background geothermal gradient so that relatively high temperatures are encountered by groundwater at relatively shallow penetration depths. The waters exiting the system at 30C to 70C at Clifton Hot Springs are thermal waters mixed with cold ground water, and water geochemistry data indicate that the thermal waters have a maximum reservoir temperature of about 180C. The minimum depth of the reservoir required for heating to 180C is calculated to be about 4.25 km, and flow rate calculations are in good agreement with chloride budget estimates from the San Francisco River into which the springs emerge. Success of this simple model provides valuable information in terms of assessing the economic uses of these hot springs. Clifton Hot Springs are thought to be typical of many hot spring systems in the Southwestern US and other gravitationally driven hot spring systems. For economic assessment of these systems, the simple semicircular tube aquifer model, combined with water chemistry data, may provide valuable information with relatively low exploration costs.
UR: http://jan.ucc.nau.edu/~pm8/PM_dwnld
DE: 5114 Permeability and porosity
DE: 8010 Fractures and faults
DE: 8030 Microstructures
DE: 8135 Hydrothermal systems (0450, 1034, 3017, 3616, 4832, 8424)
DE: 8424 Hydrothermal systems (0450, 1034, 3017, 3616, 4832, 8135)
SC: Tectonophysics [T]
MN: Fall Meeting 2005