Silica heat flow estimates and heat flow in the Colorado Plateau and adjacent areas

The Colorado Plateau is a large lithospheric block in the western United States, approximately 700 km in diameter, that has remained relatively stable during major Phanerozoic tectonic episodes that have deformed the lithosphere surrounding the Plateau, and was most recently uplifted in the Cenozoic. The thermal structure of the Plateau is important for understanding the mechanism of the plateau uplift and the reasons for its tectonic stability. Heat flow data indicate the Plateau has an average heat flow thermal interior with a high heat flow margin, but these data are too sparcely distributed in many areas to accurately map the thermal transition. We have generated a new heat flow map of the Colorado Plateau and surrounding areas using heat flow estimates based upon groundwater silica analyses. With 4094 data points in the Plateau and 5566 data points in areas immediately adjacent, the silica heat flow estimates provide more uniform coverage than the available heat flow data and indicate the following: 1. The interior of the Plateau has a mean heat flow of 55±11 mW m ^-2; 2. the Plateau margins generally have high heat flow (60-110 mW m) ^-2, averaging approx. 85 mW m ^-2), typical of theat for the surrounding Basin and Range and Southern Rocky Mountain-Rio Grande rift provinces; 3. to the north no high heat flow margin exists and the Plateau interior is thermally indistinguishable from the adjacent Uinta Uplift and Wyoming Basin; 4. There is significant of variation of heat flow within the thermal interior of the Plateau, with generally lower heat flow in the west and higher heat flow in the east where many of the traditional heat flow sites are concentrated. Silica heat flow estimates indicate that high heat flow is less extensive than typically interpreted from heat flow data. We suggest that a transition zone exists between the thermal boundaries defined by the two data sets, in which data sets, in which the heat flow is typically similar to the thermal interior, but where local thermal disturbances are common due to magmatic heating and heat transfer by groundwater flow.