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At least 433 records · Page 24Linked to original sources
USGS1975

Geology of the Midnite uranium mine, Stevens County, Washington; a preliminary report

The Midnite mine is one of only two mines in the United States currently producing uranium from discordant deposits in crystalline host rocks. Ore bodies are in metamorphosed steeply dipping Precambrian pelitic and calcareous rocks of a roof pendant adjacent to a Cretaceous(?) porphyritic quartz monzonite pluton. Production during 14 years, of operation has been about 8 million pounds of U3O8 from oxidized and reduced ores averaging 0.23 percent U3O8. Uranium deposits are generally tabular in form and dimensions range up to 380 m long, 210 m wide, and 50 m thick. Deposits are bounded on at least one side by unmineralized intrusive ribs of granitic rock, and thickest mineralized zones invariably occur at depressions in the intrusive contact. Upper limits of some deposits are nearly horizontal, and upper elevations of adjacent mineralized zones separated by ribs of granite are similar. Near surface ore is predominantly autunite, but ore at depth consists of pitchblende and coffinite with abundant pyrite and marcasite. Uranium minerals occur as .disseminations along foliation, replacements, and stockwork fracture-fillings. No stratigraphic controls on ore deposition are recognized. Rather, mineralized zones cut across lithologic boundaries if permeability is adequate. Most ore is in muscovite schist and mica phyllite, but important deposits occur in calc-silicate hornfels. Amphibolite sills and mid-Tertiary dacite dikes locally, carry ore where intensely fractured. High content of iron and sulfur, contained chiefly in FeS2, appear to be an important feature of favorable host rocks. Geometry of deposits, structural, and geochemical features suggest that uranium minerals were deposited over a span of time from late Cretaceous to late Tertiary. Ore occurs in but is not offset by a shear zone that displaces mid-Tertiary rocks.. Economic zones of uranium are interpreted to have been secondarily enriched in late Tertiary time by downward and lateral migration of uranium into permeable zones where deposition was influenced by ground water controls and minerals that could reduce or neutralize uranium-bearing solutions.

Open-File Report↗
USGS1975

Preliminary report on the use of LANDSAT-1 (ERTS-1) reflectance data in locating alteration zones associated with uranium mineralization near Cameron, Arizona

LANDSAT-I (ERTS-I) multispectral reflectance data were used to enhance the detection of alteration around uranium deposits near Cameron, Ariz. The technique involved stretching and ratioing computer-enhanced data from which electronic noise and atmospheric haze had been removed. Using present techniques, the work proves that LANDSAT-I data are useful in detecting alteration around uranium deposits, but the method may still be improved. Bluish-gray mudstone in the target area could not be differentiated from the altered zones on the ratioed images. Further experiments involving combinations of ratioed and nonratioed data will be required to uniquely define the altered zones.

Open-File Report↗
USGS1975

Preliminary report on the reconnaissance engineering geology of the Yakutat area, Alaska, with emphasis on evaluation of earthquake and other geologic hazards

Yakutat, situated about 225 miles northwest of Juneau, Alaska, near the shores of the Gulf of Alaska, has a setting that calls for superlatives. Within the Yakutat region are some of the tallest mountains, some of the heaviest snowfalls, and the largest glacier in North America. Between the abrupt mountain front and the Gulf of Alaska lies a very gently sloping plain of outwash derived from repeated cycles of advance followed by melt and retreat of glaciers during the Quaternary Period. The latest melting probably took place 500 to 600 years ago. Yakutat is built upon the moderately steep moraine that is the product of melting of one of these glaciers. Near Yakutat, surficial deposits are as much as 700 feet thick and probably overlie siltstone, sandstone, and mudstone. The eight general categories of mapped surficial deposits include artificial fill, organic, eolian, beach, delta-estuarine, alluvial, and outwash deposits, and deposits of the outer Yakutat Bay moraine complex.

Alaska↗
USGS1975

Mineral deposits in western Saudi Arabia; a preliminary report

Mineral deposits in Saudi Arabia include a variety of deposits which were formed in many geologic environments. These include magmatic and late magmatic deposits in igneous masses, contact metamorphic deposits along the margins of igneous bodies, and stratiform sulfide deposits and veins. Notable deposits of sedimentary origin include deposits of iron oxides and phosphate. Strata-bound massive sulfide deposits containing copper, zinc, and nickel sulfides associated with pyrite and pyrrhotite in complexly deformed volcanic rocks in Saudi Arabia have been the subject of controversy. They are considered by some geologists to be of syngenetic or volcanogenic origin, and by others to be epigenetic. The principal mineral deposits in western Saudi Arabia are localized in mineral belts within tectonic zones that trend northerly, northeasterly, and northwesterly. These belts contain the exploration target areas most promising for future exploration. Noteworthy among these are: 1) the northerly-trending Bidah copper-zinc belt; 2) the Sayid copper-zinc zone; 3) the northwest-trending Nuqrah copper zinc-silver belt; and 4) the north-northwesterly-trending Al Amar belt. Gold and silver deposits are mainly localized in north-trending structural features of the Hijaz geotectonic cycle and northwest Najd trends. Saudi Arabian metal deposits known thus far contain reserves in the 2 billion dollar range. Further exploration should result in discoveries that could significantly increase this amount; Saudi Arabia may well have workable metallic and nonmetallic mineral resources for industrial developments in many parts of the Kingdom. In order to effectively carry on a search for new mineral deposits, the belts should be mapped in detail, with emphasis on the delineation of stratigraphic and structural features that control metallization. In addition, geochemical and geophysical studies should be made of promising areas to outline exploration targets. These targets could then be systematically explored.

Open-File Report↗
USGS1976

Preliminary report on coal resources of the Otter Creek EMRIA site, Powder River County, Montana

The Knoblock coal bed in the Otter Creek EMRIA (Energy Minerals Rehabilitation Inventory and Analysis) site--an area of about 1,177 acres (476 hectares)--contains estimated identified coal resources of about 126 million short tons (114 million metric tons). The area around and including the Otter Creek EMRIA slte--an area of about 2,975 acres (1,204 hectares)--contalns estimated identified coal resources of about 318 million short tons (289 million metric tons). All estimated coal resources in the Knoblock bed are categorized as measured and indicated resources, and all but about 62 million tons (56 million metric tons) are at depths of less than 200 feet (60 metres). The average thickness of the Knoblock is about 61 feet (18.6 metres) and the overall relationship of quantity of overburden to tons of coal in the area with 200 feet (60 metres) or less of overburden is about 2 cubic yards (1.5 cubic metres) of overburden per ton of coal. The coal is subbituminous C in rank, has an average sulfur content of less than 0.2 percent, and has an average ash content of about 5.5 percent. The major and minor element composition of coal, coal-ash, and rock samples from the area is similar to the average composition of other coals of the Northern Great Plains and to the average rock composition of the Earth's crust. Only the selenium content of the Knoblock coal is more than an order of magnitude higher than that in the continental crust.

Open-File Report↗
USGS1976

Preliminary report on uranium-, thorium-, and rare-earth-bearing rocks near Golovin, Alaska

Uranium-, thorium-, and rare-earth bearing rocks were found by a U.S. Geological Survey field party 15 miles northeast of Golovin, Alaska, in the southeastern Seward Peninsula (fig. 1) in June 1976. The mineralized areas occur in syenite and appear to be concentrated along the margins of alkaline dikes, with allanite tentatively identified as the principal mineral containing the uranium-, thorium-, and rare-earths. Samples contain as much as 0.15 percent U 3 0 8 and 1.05 percent Th0 2 , and over 2 percent rare-earth elements. These mineralized rocks are closely associated with alkaline dikes which are part of a dike swarm that crops out over at least 250 km 2 (100 mi 2 ). This large dike swarm is thus of considerable economic interest. These uranium-, thorium-, and rare-earth-rich rocks occur near the west end of the western Alaska uranium-thorium province (West, 1953; Clark and others, 1975; Miller, 3976) and were found during a regional investigation of this province by the Geological Survey. The alkaline dikes were known from previous mapping by the two senior authors (Miller and others, 1972) to be anomalously radioactive. The mineralized areas described in this report were found while making a brief study of (1) alteration and/or mineralization associated with these dikes and (2) their relation to similar dikes and rocks which occur elsewhere in the province (Miller, 1972).

Alaska↗