Tertiary granitic plutons of the Alaska Range

• Main Authors: Michael Beyth, Carlotta Mcinteer
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: alaska range; Alaska
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.603.785; http://www.minersoc.org/pages/Archive-MM/Volume_46/46-341-475.pdf

A B S TR A C T, Favourabi l i ty of u ran ium mineral izat ion i six tertiary granitic plutons of the Alaska Range in the Talkeetna nd Mt McKinley quadrangles was studied. The uranium concentrations of drainage sediment samples, which were collected and analysed by the Los Alamos Scientific Laboratory for the National Uranium Resources Evaluation, were statistically evaluated and compared to those of the surrounding area using factor and cluster analyses. The results of this study suggest that five of the six plutons under consideration are likely to contain uranium mineralization. These plutons are probably a potential source rock for uranium in the region. THE purpose of this study is to evaluate the favourability of uranium mineralization i six granitic plutons (Table I) of the Alaska Range in the Talkeetna nd Mt McKinley NTMS quad-rangles, Alaska (fig. 1), mapped by Reed and Nelson (1977) and Reed (1961). The evaluation is based mainly on criteria suggested by Simpson et al. (1979), using Hydrogeochemical and Stream Sedi-ment Reconnaissance (HSSR) data which was published by Aamodt et al. (1979) and Van Eeck-bout et al. (1979). Simpson et al. (1979) suggest that uranium mineralization is associated with intrusive com-plexes with a high average content of U, but which also exhibit a high concentration f incompatible elements (e.g. Li, Be, Rb, B, and F), high K concentration, but a low K/Rb ratio, low total Sr, low initial 87Sr/86Sr atio, and high geothermal gradient. The standard eviations for U data are greater where such intrusives are mineralized, but their average values are relatively unaltered. Hence, Simpson et al. (1979) suggested that U is enriched in the granitic magma primarily by scavenging from the subcontinental lithosphere, but also by mag-matic differentiation. They further suggest hat