Introduction: This study was made in conjunction with a core drilling program designed to trace ore trends from existing mines eastward under deeper cover. The exploration drilling covered an area of about 1 square mile. The results of previous drilling by the Commission, which covered an additional 10 square miles, have been incorporated in this report.

Abstract: A low-level airborne radioactivity survey of parts of Beaverhead and Madison Counties in southwestern Montana was undertaken from June 6 to October 14, 1955. Flying centered around the Ruby Range-Sweetwater Basin area and concentrated on the Precambrian metamorphic complex and Tertiary lake-bed sediments. No commercial uranium deposits were discovered, and no extensions were found of the few known small occurrences. Five areas of high background detected through the survey were investigated on the ground.

Although uranium gas first discovered in the Carrizo Mountains area in 1918, the ores were not developed until 1942. They have, however, been mined continuously since that time. Formations in the area range from the Pernian Cutler through the Cretaceous Mancos shale, and all are intruded by a dioritic laccolith and its related dikes. The older structures, which include the Defiance Uplift, the San Juan Basin, and the Four Corners Platform are somewhat disrupted by the effects of the intrusion. A number of mines are described and mineralogical and geochemical studies made are outlined. The primary uranium mineral is unknown, but the chief uranium ore-mineral is the secondary mineral, tyuyamunite. It is concluded that there is at least minor structural control of the ore bodies along sedimentary trends and joints, and that all ore bodies of 500 tons or more are on the Defiance monocline or its extensions. The uranium may have been syngenetic in the sediments, and redistributed by solutions or, more likely, that it rose vertically in hydrothermal solutions from the local intrusive bodies.

From Purpose, Scope, and Methods: The objective of this study was an evaluation of resources of the Carrizo Mountains area. Four factors: distribution of ore bodies, relation of uranium to the host rock, relation of ore to structure, and circumstances that might precipitate uranium were studied in search of data bearing on manner of distribution of ore, the time and causes of deposition, and the probable source of the uranium-bearing solutions.

Abstract: In a study of the comparative importance of sedimentary and tectonic ore controls and in search of data bearing on the origin of the deposits, ten mines in the Lukachukai Mountains, Apache County, Arizona were examined in detail. All commercial deposits in the area are in the Salt Wash Member of the Morrison Formation of Jurassic age. The ore bodies are elongate and horizontally lenticular in shape and consist of one or more ore pockets surrounded or separated by protore. The composite length of ore bodies consisting of two or more ore pockets separated by subore grade material ranges up to 1,100 feet; individual ore pockets range up to 350 feet in length. Elongation is usually at least three times the width and is parallel to paleostream depositional trends measured in and near the ore bodies. Claystone and/or siltstone units nearly always underlie and frequently overlie the host sandstone units. Ore occurs most frequently in trough-type, cross-stratified sandstone which fills scours and channels in the underlying claystone units. Lithofacies maps and mine mapping show that ore bodies are restricted to areas of rapid lateral color change which in general are also areas of rapid change in the ratio of …

This report records the study of the geology and uranium deposits of Haiwee Ridge, Inyo County, California, on the west flank of the Coso Mountains.

Discussing a drilling program planned to investigate the lithology and internal stratigraphy of the Wasatch formation and to determine the depth to the underlying surface of unconformity of the basal contact of the Wasatch formation.

Describing and comparing the uranium deposits in the Morrison formation, except those of the Ambrosia Lake locality.

Discussing an investigation made to search for the evidence of channels for hydrothermal uraniferous solutions in the diatremes of the Hopi Buttes volcanic field.

Reporting investigations into the lithologic and structural ore controls as revealed by this exploration program.

A report regarding regional fracture systems mapped for an area of about 90,000 square miles, embracing most of the Colorado Plateau and small strips of the adjoining Rocky Mountains, by the use of aerial photographs and mosaics. The data interpreted from the photographically reduced to produce the final map.

A report regarding uranium deposits of the Urvan Mineral belt.

Geologic map of the Crooks Map District, Freemont District, Wyoming showing core drill holes prepared for a report by U.S. Atomic Energy Commission, Grand Junction Office.