Epigenetic mineralization and areas favorable for uranium exploration in Tertiary continental sedimentary rock in south-central Alaska: A preliminary report

Abstract

One of the most important questions about the potential for epigenetic uranium deposits in the Tertiary sedimentary rocks of Alaska is whether or not geochemical conditions conducive to the epigenetic processes could have existed in the warm to cool-temperate moist climatic conditions that apparently were present during much of the Tertiary in south-central Alaska. Evidence bearing on this problem is meager, but uranium analyses of samples taken in this study suggest that low-level enrichment by uranium-bearing ground water has occurred. Another important question is whether or not valid ranking of areas for uranium potential on the basis of average uranium content of host rocks can be made. This report offers no answer to this question, but consistent differences in uranium background in host rocks of different areas suggests that such a procedure is feasible. The five areas discussed are ranked according to favorability for uranium exploration as follows: first, Susitna Lowlands; second, northwest Cook Inlet; third, Matanuska Valley; fourth, Kenai Peninsula; and fifth, Copper River basin. The Susitna Lowlands are ranked most favorable because they have the highest average uranium content and because low-level secondary enrichment has occurred there. Northwest Cook Inlet is second and Matanuska Valley is third onmore » the basis of average uranium content. The Kenai Peninsula is fourth because of its low average uranium content and because most of the sediments in this area were derived from the east from the Kenai Mountains, which lack large areas of granitic or volcanic rock that might have provided a source for uranium. Copper River basin is ranked least favorable because it has the lowest uranium content.« less