Thin, Dipping Ore Zone Logging Models. Log Studies

摘要

Thin, dipping mineralized zones are associated with a number of uranium deposits in various regions of the United States. In response to uncertainties about thin bed log interpretation, two thin, dipping ore zone logging models were constructed. Preliminary log studies with these models have established the following relation for gross gamma-ray logs of thin, dipping beds: GT = KA cos(theta), where G = radiometric equivalent uranium grade, T = true zone thickness, K = probe calibration constant. A = area under zone response curve, and theta = dip angle of thin zone. For horizontal (theta = 0) thin beds, this expression is identical to the well-known relation for gross gamma-ray logs of thick horizontal zones: GT = KA. In resource mapping, the cos (theta) factor is applicable if resources are to be projected onto a plane that is parallel to the plane of the dipping mineralized zone. If mapping is to be done on a plane that is perpendicular to the borehole, then the appropriate expression is GT = KA, regardless of the dip angle. A satisfactory method has not been found for determining T in thin beds, whether inclined to the borehole or not. (ERA citation 05:023676)