Preliminary investigations of radioelement distribution in an Archean granite gneiss from drill hole MG-CR-2A, Republic area, Michigan
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Open-File Report↗
Geology topics
Carl M. Bunker
Publications and source records attributed to Carl M. Bunker.
Radiometric results and areal distribution for granitic samples from the Granite Mountains, Wyoming
Analyses of surface samples from the Granite Mountains, Wyoming, generally agree with the findings from drilling at two different localities. The dominant Precambrian granitic rock type is the biotitic phase of the granite of Lankin Dome. This rock type is characterized by high potassium and anomalously high thorium concentrations, and is the most favorable granitic source for the uranium deposits in the surrounding area. Areal distribution patterns for radioelement concentrations show that the most favorable source regions are located closest to known uranium deposits. Most of the granitic rocks in the Granite Mountains region are characterized by high thorium-uranium ratios. These high ratios are interpreted to be the result of uranium loss. Non-gaussian distribution of radioelement contents and poor correlation between radioelement pairs are interpreted to be the result of some redistribution of radioelements during the last phase of granite crystallization and to recent uranium loss. A good correlation between thorium and iron is attributed to the mobilization of thorium into microcrystalline iron oxides during a late portion of the magmatic history. A comparison of sulfur data for surface and shallow drill-hole samples suggests that sulfur has been removed from the granite to at least a depth of 20 m. The loss of uranium and sulfur from these samples suggests that other trace elements found in association with uranium deposits might have been removed from the granite.
Wyoming↗
A comparison of some analytical techniques for determining uranium, thorium, and potassium in granitic rocks
Geochemical exploration for uranium requires accurate and precise determinations of low-level concentrations. We have used seven different techniques and four different treatments of the fluorometric method to analyze for uranium in granitic rocks. In addition we have used four analytical techniques for thorium and three analytical techniques for potassium, two elements that are commonly present in anomalous amounts within uranium provinces. Our results show that commonly used techniques for thorium and potassium determinations are both adequately precise and accurate, but that many techniques used for uranium determinations lack the necessary precision or accuracy for complete geochemical prospecting. We suggest that a combination of delayed-neutron determinations for uranium and γ -ray spectrometric analyses for radium equivalent uranium, thorium, and potassium provides the best data base for geochemical exploration for uranium. If more detailed interpretations are desired, the combination of γ -ray spectrometry and α -spectrometry may be best. Carefully done fluorometric analyses should be adequate for water, ore, mineralized rock, and other applications where high precision and accuracy are not required.
Journal of Research of the U.S. Geological Survey↗
A reconnaissance study of the uranium and thorium contents of plutonic rocks of the southeastern Seward Peninsula, Alaska
Large granitic Cretaceous plutons are exposed along and adjacent to an arcuate belt of igneous and high-grade raetamorphic rocks in the southeastern Seward Peninsula of Alaska. Reconnaissance studies of these plutons have shown that the Darby pluton has well above average amounts of uranium and thorium (11.2 ppm and 58.7 ppm, respectively), the Kachauik pluton contains average to above average uranium and thorium (5.7 ppm and 22.5 ppm, respectively), and the Bendeleben pluton contains average amounts of uranium and thorium (3.4 ppm and 16.7 ppm, respectively). The three plutons show compositional and textural differences indicative of different source materials that may have controlled the distribution of uranium and thorium. The high uranium and thorium contents of the Darby pluton, similar to those of the Conway Granite of New Hampshire which has been mentioned as a possible low-grade thorium resource, suggest that this pluton may be a favorable area for economic concentrations of uranium and thorium.
Alaska↗
U, Th, and K analyses of selected plutonic rocks from west-central Alaska
Numerous samples of plutonic rocks collected during reconnaissance mapping in western Alaska have been analyzed for K, U, and Th. The U and Th content of the plutonic rocks from the southeastern Seward Peninsula have been discussed in a separate report (Miller and Bunker, 1975); because of the current interest in U and Th, the analyses of the remaining samples are given in this report.
Alaska↗
A reconnaissance study of the U and Th contents of plutonic rocks of the southeastern Seward Peninsula, Alaska
Large granitic Cretaceous plutons are exposed along and adjacent to an arcuate belt of igneous and high-grade metamorphic rocks in the southeastern Seward Peninsula of Alaska. Reconnaissance studies of these plutons have shown that the Darby pluton has well above average amounts of U and Th (11.2 ppm and 58.7 ppm respectively), the Kachauik pluton ranges from average to above average U and Th (5.7 ppm and 22.5 ppm respectively), and the Bendeleben pluton contains average amounts of U and Th (3.4 ppm and 16.7 ppm respectively). The three plutons show compositional and textural differences indicative of different source materials which may have controlled the distribution of U and Th. The high U and Th contents of the Darby pluton, similar to that of the Conway Granite of New Hampshire which has been mentioned as a possible low grade Th resource, suggests that this pluton may be a favorable area for economic concentrations of U and Th.
Alaska↗
Potassium, thorium, and uranium contents of upper Cenozoic basalts of the southern Rocky Mountain region, and their relation to the Rio Grande depression
Late Cenozoic basaltic volcanism in southern Colorado and northern New Mexico was most intense near the Rio Grande rift depression but extended onto stable platforms to the west (Colorado Plateau) and to the east (High Plains). Tholeiitic rocks are largely confined to the Rio Grande depression, and the basalts become increasingly alkalic with distance from the depression. The K, Th, and U contents and the Th/K and U/K ratios consistently increase away from the depression, and Th/U ratios also tend to increase slightly. Geographically distinct suites of petrographicaUy related basalts that are very similar in major-oxide compositions are readily distinguishable by K, Th, and U contents. Sialic crustal contamination did not contribute significantly to development of these compositional variations, and the lateral change from tholeiitic to alkalic basaltic volcanism may be related to different depths of or degrees of partial melting in the mantle. The compositions and compositional ranges of basalts in the southern Rocky Mountain region are similar to those of many Pacific islands, despite the contrasting geologic settings.
Colorado, New Mexico↗
Comparison of thickness, grade, and depth of radioactive layers as determined by gamma-ray logging and by core sampling
Thickness, grade, and depth data were obtained by analyzing gamma-ray logs and core samples from 56 diamond drill holes penetrating uranium deposits in the Colorado Plateau. The data from the two methods were compared to determine variations found in gamma-ray log interpretation and chemical and radiometric analyses of the drill core. Correlations within each parameter varied among the drilling areas analyzed. Gamma-ray interpretations of grade compared to chemical analyses were within the range of -10 to +25 percent. Most depth measurements determined by gamma-ray log interpretation compared to drill core measurement were within 0.5 percent. Results of the study indicate a need for better thickness definition in both gamma-ray logging and core scanning equipment.
Trace Elements Investigations↗