Directional resistivity measurements in exploration for uranium deposits on the Colorado Plateau

Abstract

A study of the electrical properties of the Morrison formation in the Uravan mineral belt of the Colorado Plateaus province indicated that there is a significant correlation between electrical resistivity and the relative favorability for occurrence of ore. The differences in resistivity were not large enough to provide a recognizable target for standard resistivity' field methods, especially where the ore-bearing sandstone member is more than a few hundred feet deep. Measurement of resistivity trends by placing one electrode in a drill hole and spreading the others out radially on the surface seemed to offer a means of exploiting the resistivity-favorability correlation. Field tests of such directional resistivity measurements were made in the Spud Patch area in San Miguel County, Colo., and the White Canyon district) San Juan County, Utah. In the Spud Patch area two methods were tried; in one a current electrode was placed in the drill. hole, and in the other, a potential electrode. The second was the more tedious but provided the more readily interpretable results. A comparison of the resistivity trends thus determined with the favorability estimated from geologic indexes indicated that directional resistivity methods could predict the location of favorable areas at distances of 600 to 1,000 feet with a high degree of success. In the White Canyon district directional resistivity measurements were made on the assumption that the conglomerate which is found in many channels filled with the Shinarump member of the Chinle formation has a high resistivity. The measurements were successful in tracing the channel conglomerate where surface conditions were favorable.