The Hydrothermal Outflow Plume of Valles Caldera, New Mexico, and a Comparison with Other Outflow Plumes

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Journal Article: The Hydrothermal Outflow Plume of Valles Caldera, New Mexico, and a Comparison with Other Outflow Plumes

Abstract
Stratigraphic, temperature gradient, hydrogeochemical, and hydrologic data have been integrated with geologic data from previous studies to show the structural configuration of the Valles caldera hydrothermal ouflow plume. Hydrologic data suggest that 25-50% of the discharge of the Valles outflow is confined to the Jemez fault zone, which predates caldera formation. Thermal gradient data from bores penetrating the plume show that shallow gradients are highest in the vicinity of the Jemez fault zone (up to 190°C/km). Shallow heat flow above the hydrothermal plume is as high as 500 mW m-2 near core hole VC-1 (Jemez fault zone) to 200 mW m-2 at Fenton Hill (Jemez Plateau). Chemical and isotopic data indicate that two source reservoirs within the caldera (Redondo Creek and Sulphur Springs reservoirs) are parents to mixed fluids flowing in the hydrothermal plume. However, isotopic data, borehole data, basic geology, and inverse relations between temperature and chloride content at major hot springs indicate that no single reservoir fluid and no single diluting fluid are involved in mixing. The Valles caldera hydrothermal plume is structurally dominated by lateral flow through a belt of vertical conduits (Jemez fault zone) that strike away from the source reservoir. Stratigraphically confined flow is present but dispersed over a wide area in relatively impermeable rocks. The Valles configuration is contrasted with the configuration of the hydrothermal plume at Roosevelt Hot Springs, which is dominated by lateral flow through a near-surface, widespread, permeable aquifer. Data from 12 other representative geothermal systems show that outflow plumes occur in a variety of magmatic and tectonic settings, have varying reservoir compositions, and have different flow characteristics. Although temperature reversals are commonly observed in wells penetrating outflow plumes, reversals are not observed in all plumes. Less information is available on the absolute age of hydrothermal outflow plumes, although the data show that they can be as old as 106 years and display episodic behavior.

Authors 
Fraser E. Goff, Lisa Shevenell, Jamie N. Gardner, Francois D. Vuataz and Charles O. Grigsby








Published Journal 
Journal of Geophysical Research, 1988





DOI 
10.1029/JB093iB06p06041

Online 
Internet link for The Hydrothermal Outflow Plume of Valles Caldera, New Mexico, and a Comparison with Other Outflow Plumes

Citation

Fraser E. Goff,Lisa Shevenell,Jamie N. Gardner,Francois D. Vuataz,Charles O. Grigsby. 1988. The Hydrothermal Outflow Plume of Valles Caldera, New Mexico, and a Comparison with Other Outflow Plumes. Journal of Geophysical Research. 93(B6):6041-6058.