Reconnaissance for radioactive deposits in the Eagle-Nation area, east-central Alaska, 1948
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Geology topics
Publications and source records attributed to Helmuth Wedow.
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Summaries of the geology and mineral deposits, and appraisals of the uranium possibilities of the various regions of Alaska are presented in this report. A short statement on previous knowledge and investigation of radioactive materials in the Territory is also given. The review of data and appraisal for the Seward Peninsula-Jobuk, Lower Yukon-Kuskokwim, Upper Yukon, Alaska Railroad-Iliamna, and southeastern Alaska regions are essentially complete. Those of the Copper River, Gulf of Alaska, Aleutian and northern Alaska regions are not yet complete. A more detailed presentation of these latter regions will be made in the final report. The appraisals are based on known occurrences of radioactive materials and geologic criteria that suggest the presence of uranium. Review of published and unpublished data to date shows that the Seward Peninsula-Kobuk region and southeastern Alaska followed by the Alaska Railroad, Gulf of Alaska and Lower Yukon-Kuskokwim regions are perhaps the more promising regions of the Territory for the occurrence of high-grade uranium ores.
Investigation of radioactivity anomalies at the Copper Creek copper lode prospect, Eagle district, east-central Alaska, during 1949 disclosed that the radioactivity is associated with copper mineralization in highly metamorphosed sedimentary rocks. These rocks are a roof pendant in the Mesozoic "Charley River" batholith. The radioactivity is probably all due to uranium associated with bornite and malachite.
Thorium-bearing minerals are known at 47 localities in Alaska. At these localities the thorium occurs as a major constituent or in minor amounts as an impurity in one or more of the following 12 minerals: allanite, columbite, ellsworthite, eschynite, gummite, monazite, orangite, parisite, thorianite, thorite, xenotime, and zircon. In addition other minerals, such as biotite and sphene, are radioactive and may contain thorium. Several unidentified columbate minerals with uranium or thorium and uranium as major constituents have been recognized at some localities. The distribution, by type of deposit, of the 57 thorium occurrences is as follows: lode - 3, lode and placer - 1, granitic rock - 3, granitic rock and related placer - 14, and placer - 26. Of the four lode occurrences only the radioactive veins at Salmon Bay in southeastern Alaska and the contact metamorphic deposit in the Nixon Fork area of central Alaska warrant further consideration, although insufficient data are available to determine whether these two deposits have commercial possibilities. The remaining occurrences of thorium-bearing minerals in Alaska are limited to placer deposits and disseminations of accessory minerals in granitic rocks. In most of these occurrences the thorium-bearing minerals occur in only trace amounts and consequently warrent little further consideration. More data are needed to determine the possibilities of byproduct recovery of thorium-bearing minerals from several of the gold and tin placers.
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