Geology topics
Frank Clarkson Armstrong
Publications and source records attributed to Frank Clarkson Armstrong.
Eastern and central Montana as a possible source area of uranium
Geologic settings in central and eastern Montana and in a few places in southwestern Montana are similar to the settings in areas favorable for the occurrence of uranium deposits. Several areas in Montana seem especially favorable for the occurrence of uranium.The alkalic igneous rock province of central Montana is similar to the one of the Colorado Plateau. On the basis of this analogy, certain areas in Montana, where the lithology and (or) structure are considered favorable for the occurrence of uranium, are suggested for prospecting. Seleniferous plants, similar to those that are uranium indicators on the Colorado Plateau, might be used as an aid in prospecting for uranium provided that the seleniferous shale areas are taken into account.Uranium deposits, similar to those in North and South Dakota, may be found in Cretaceous and Tertiary sandstones, lignites, and low-grade coals of eastern Montana; also, the magnetite-bearing beds of certain Cretaceoussandstones may contain fossil placer deposits of radioactive black minerals. Theoccurrence of uranium in basal conglomerates, quartzites, and sandstones in Africa and Ontario suggests that similar basal sedimentary rocks in central Montana may contain uranium.Many of the radioactivity anomalies in Montana found from the air are closely associated with the Eagle sandstone; others are associated with Precambrian basement rocks, Upper Cretaceous and Lower Tertiary igneous rocks, or sedimentary rocks of Jurassic and Cretaceous age. Glacial cover and lack of outcrops locally may hinder prospecting for uranium.
The Garm-Lamoreaux mine, Lemhi County, Idaho
The Garm-Lamoreaux property, Lemhi County, Idaho is known to have uranite and zippsite on two of its dumps. The property has been explored by five adits, two of which are now caved, and one of which is partly caved. The country rock is schistose micaceous quartzite and argillaceous quartzite of Belt age. An east-west fault cuts the quartzite, and the Lamoreaux vein, a gold-sulfide-quartz vein, occurs in the fault. The uramium minerals are believed to have come from the vein, on the now inaccessible No. 3 level. An alidade and plane-table map was made to tie in the positions of the five underground workings. The lowest adit, the first 200 feet of Tunnel 2 and the Eardrock tunnel were mapped. Maps of the other workings made by Gilbert in 1933 were combined with the writers maps. Samples were collected from the radioactive parts of the number two and number three dumps. Chemical analyses of the samples showed a range from 0.001 to 0.54 percent uranium. It appears probably that at least some uranium could have been leached by sulfate-bearing waters in the dump material. The presence of as much as 0.54 uranium in one sample from the Tunnel 3 dump suggests that exploration program would be advisable.
Preliminary report on the geology of the Atlantic City-South Pass mining district, Wyoming
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