Description
Is uranium deposit variability a function of singular or multiple interdependent stratigraphic parameters? This investigation studies the mineralized area of two Jurassic uranium deposits in New Mexico and Utah. Various parameters of each deposit were studied to discover, through statistical modelling, certain equations that would simplify, quantify, and define certain interdependent relationships. In this way the "structured system" of each uranium deposit could be depicted, allowing exploration within this "structured system" to be undertaken with the minimum of risk and error. Multiple regression analysis was the research tool employed. The result of a given deposit parameter's variability was estimated by solving for the coefficient and known values of certain stratigraphic criteria which are weighted in respect to their relative importance. Stratigraphic variables were only included in the models if they met a specific desired probability level assigned by the researcher. Only terms that could improve on pure chance were included. This research was conducted to show the plausibility of such a method in simplifying the complexities associated with the two deposits studied. The stratigraphic parameters included rock unit thicknesses, sand-shale ratios and vertical variability facies indicators, and structural tops and bottoms of lithologic units. Some chemical data were included because of its availability. Deposit parameters included vertical grade-cutoff, elevations of tops and bottoms of deposits, number of mineral horizons, grade-thickness, thickness and grade of uranium. The variables used are basic and do not exhaust the potential qualities that can be measured if certain basic data are available, as it is for most uranium deposits. The results were significant at the 95 percent F-statistic confidence level for most of the models presented. The models that were non-probable are potentially definable if a more accurate stratigraphic or set of stratigraphic parameters is found. The New Mexico deposit was generally best defined stratigraphically by the variability of the structural top of the Poison Canyon Sandstone, the ore host. It was proposed that differential compaction of the ore host was responsible for the enrichment of the uranium in the thinner portions of the bed. The model study also proposed the possibility of early uranium emplacement. The Utah deposit was best defined stratigraphically by the thickness of the ore-bearing sandstone. The thicker portions contained the higher grade values of the deposit. Local facies changes also were proposed to be a major determinant in the deposit habit. An east-west mineral solution path was postulated for deposit enrichment. Uranium grade variation as a function of space indicated the high probability of a predictable trend linearly in the two deposits. A study of geographical variation of uranium, vanadium, and lime concentration in the Utah deposit indicated a probable northwestward increase in the deposit area.
