Temperature, Thermal Conductivity, and Heat Flow Near Yucca Mountain, Nevada: Some Tectonic and Hydrologic Implications.

摘要

Repeated temperature logs were obtained in 18 geologic and hydrologic test wells near Yucca Mountain, Nevada. Single logs were also obtained (using a specially designed sonde with fast response in air) in the air column of 17 wells drilled to monitor water level below and around Yucca Mountain. The temperature data suggest that the thermal regimes of both the saturated and unsaturated zones are strongly influenced by a complex hydrologic regime in the saturated tuffs and underlying Paleozoic carbonate rocks. Temperature gradients in the unsaturated zone (UZ) appear primarily conductive, but they range from about 15 C km(sup -1) to nearly 60 C km(sub -1). However, one profile indicates rapid penetration to a depth of 150 m beneath a major channel by water from run-off following a local heavy rain. From the water table (which ranges in depth from about 300 m to over 700 m) to depths of 1 km or more, the temperature gradient in the saturated zone (SZ) typically is very irregular with evidence for locally controlled water movement in the Tertiary volcanic rocks, laterally and both up and down vertically. Vertical seepage velocities inferred from one-dimensional hydrologic models range from a few millimeters to 100 millimeters or more per year. Below depths of 1 km, temperature profiles are linear, suggesting conductive heat flow, but as in the case of the UZ, the gradients are quite variable, suggesting that the heat flux here is being controlled by fluid flow in the Paleozoic carbonate aquifer that underlies Yucca Mountain. 26 refs., 18 figs., 6 tabs. (ERA citation 14:002877)