Abstract

Preliminary heat-flow estimates were calculated for 32 sites in the Colorado Plateau, the eastern Basin and Range Province, and the Middle Rocky Mountains. At 23 of these sites, the heat-flow estimates are believed to have merit. The heat-flow estimates often agree with nearby measurements and correlate reasonably well with interpretations from other geophysical techniques. The mean of the heat-flow estimates hi the northern Colorado Plateau interior (66 to 69 mWm−2) is within ∼5% or ∼18% of the mean of deep or shallow heat-flow measurements, respectively. Estimates in the peripheral areas of the plateau, in the San Juan Basin, agree with higher heat-flow measurements at sites approaching the San Juan volcanic field. Estimates along the western periphery of the Colorado Plateau are higher than in the interior and therefore suggest an anomalously shallow mantle (asthenosphere), extending ∼50 km under the plateau; this is consistent with previous studies. Above-average Basin and Range heat flows are estimated in the eastern Basin and Range Province (99–102 mWm−2), and this concurs with a high energy-flux zone proposed for the area. The transition from high to low heat-flow estimates between the eastern Basin and Range Province and the Middle Rocky Mountains seems to occur over a small distance (∼36 km). The narrow heat-flow transition implies shallow thermal sources in proximity to the Basin and Range–Middle Rocky Mountains transition; this may correspond to a shallow crustal low-velocity zone previously interpreted along the transition.

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