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Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

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At least 631 records · Page 35Linked to original sources
USGS1975

Possible extension of mineral belts, northern part of Coeur d'Alene district, Idaho

The ore deposits in the northern part of the Coeur d'Alene district are located within rocks of the Belt Supergroup that have been intruded by Cretaceous quartz monzonites. Lead-zinc-silver replacement veins constitute most of the deposits. The geometry of the district has been modified by post-ore faulting along the Osburn, Dobson Pass, and other faults. The original position of the Gem stocks, before their separation from the Diego Peak stocks by the Dobson Pass fault, can be approximately reconstructed by moving the truncated stocks and associated geochemical dispersion patterns back into matching positions. The known mineral belts are defined by dispersion patterns of both lead and the Pb:Zn ratio. Similar dispersion patterns of lead and the Pb:Zn ration northwest of the original position of the Gem stocks suggest that the mineral belts extend into that area.

Idaho↗
USGS1978

Natural radioactivity in geothermal waters, Alhambra Hot Springs and nearby areas, Jefferson County, Montana

Radioactive hot springs issue from a fault zone in crystalline rock of the Boulder batholith at Alhambra, Jefferson County, in southwestern Montana. The discharge contains high concentrations of radon, and the gross alpha activity and the concentration of adium-226 exceed maximum levels recommended by the Environmental Protection Agency for drinking water. Part of the discharge is diverted for space heating, bathing, and domestic use. The radioactive thermal waters at measured temperatures of about 60°C are of the sodium bicarbonate type and saturated with respect to calcium carbonate. Radium-226 in the rock and on fractured surfaces or coprecipitated with calcium carbonate probably is the principal source of radon that is dissolved in the thermal water and discharged with other gases from some wells and springs. Local surface water and shallow ground water are of the calcium bicarbonate type and exhibit low background activity. The temperature, percent sodium, and radioactivity of mixed waters adjacent to the fault zone increase with depth. Samples from most of the major hot springs in southwestern Montana have been analyzed for gross alpha and beta activity. The high level of radioactivity at Alhambra appears to be related to leaching of radioactive material from siliceous veins by ascending thermal waters and is not a normal characteristic of hot springs issuing from fractured crystalline rock in Montana.

Montana↗
USGS1978

Porphyry-type metallization and alteration at La Florida de Nacozari, Sonora, Mexico

Pervasive secondary biotite-rich mineral assemblages, characteristic of potassic alteration found in the cores of most commercial porphyry copper systems, are associated spatially with a conspicuous color and a geochemical anomaly at La Florida de Nacozari, Sonora. These composite biotite-magnetite assemblages, with or without actinolite, quartz, rutile, sphene, chalcopyrite, and pyrite assemblages, are primarily the result of early dispersed biotitic (EDB) alteration of andesite. The bulk of the near-surface copper in the area, however, was introduced later by the veins that cut the EDB-altered andesite. These late veins are distinguished by a quartz-calcite-chlorite±laumontite±chalcopyrite assemblage, and the chalcopyrite in these veins may reflect upward remobilization of deep EDB copper by fluids associated with the emplacement of nearby coarse-grained granite. Fluid-inclusion relations in the late veins suggest that their fluids were nonboiling and relatively dilute.

Sonora↗
USGS1977

High-resolution gamma-ray spectrometry in uranium exploration

Sedimentary-type uranium deposits accumulate at favorable sites along a migration path which may be kilometers in length. Their source is a large volume of rock from which the uranium has been leached. The geochemical mobilities and half lives of uranium and its daughter products vary widely so that they are transported from the source rocks, at different rates, along the migration path to their ultimate site. The radioactive disequilibrium resulting from this process has been well documented in the immediate vicinity of ore deposits, and disequilibrium is commonly recorded on gamma-ray logs up the hydraulic gradient from uranium ore. Little is known about the state of secular equilibrium in the leached host rocks, which often represent the only part of the migration path that is at or near the surface and is thus most accessible to the exploration geophysicist. High-resolution gamma-ray spectrometry provides a means of investigating the disequilibrium associated with uranium leaching and migration. Direct measurement of uranium can be made by this method, and the equivalent weight percents can be determined for six of the seven daughter-product decay groups that characterize the state of radioactive equilibrium. The technique has been used quantitatively in laboratory studies, where the results compare favorably with radiochemical analyses; field experiments suggest that semi-quantitative data may be obtained at the outcrop.

Journal of Research of the U.S. Geological Survey↗
USGS1978

Morphology of chasma walls, Mars

The landforms developed on the walls of the Valles Marineris system of chasmas are of three major types, which are locally transitional. The most common type is composed of steep spurs and gullies. The dominant process in the formation or modification of this type appears to be the downslope movement of. material under the influence of gravity, resulting in the accumulation of extensive talus deposits. The type is morphologically similar to high, steep terrestrial scarps in desert or alpine environments. The second morphologic type consists of walls dissected by tributary canyons with characteristic V-shaped cross profiles and blunt canyon heads that locally contain lobate deposits. The tributary canyons may be relict features of the time, when the existence of running water was possible on the surface of Mars. The third morphologic type consists of landslide scars forming broad curved or straight recessed sections of chasma wall. This type is accompanied by landslide deposits that form hummocky floors at the base of the recessed sections. The landslides developed at the expense of other wall morphologies. Chains of rimless depressions and craters that parallel the main structural trends of the chasmas are best interpreted as collapse holes. The origin of the chasmas on Mars is conjectural and may have been structural (grabens), but, on the basis of morphologic studies of their walls, it is suggested that most of the present wall configuration is the result of erosional scarp retreat, where erosion follows preestablished structural planes of weakness.

Journal of Research of the U.S. Geological Survey↗
USGS1977

Combined use of digital aquifer models and field base-flow data to identify recharge-leakage areas of artesian aquifers

As a result of continuous pumping since the 1890's, a regional cone of depression encompassing 363 km 2 has developed within the artesian Miocene Cheswold aquifer at Dover, Del. The aquifer is not being recharged significantly by leakage near the center of the cone, nor is major recharge induced in the updip subcrop area. The source of pumped water is apparently an area of about 65 km 2 northwest of Dover, where vertical leakage is substantial. This area was delineated by use of a digital aquifer model and streamflow data. A model of the unconfined aquifer was used to compute the unconfined aquifer's natural discharge to streams, assuming no leakage to underlying artesian aquifers. The area of substantial leakage to the underlying Cheswold was delineated as being coincident with that area where model-computed values of stream discharge were substantially larger than actual values of stream discharge determined in the field.

Delaware↗
USGS1973

Fluorite equilibria in thermal springs of the Snake River Basin, Idaho

Some thermal water sources of the Snake River basin, Idaho, are near saturation with respect to fluorite. That mineral was identified by X-ray diffraction in precipitates induced in three water samples by adding sodium fluoride. The derived solubility product (K S0 ) for zero ionic strength was close to that calculated from Latimer's thermodynamic data (10 -9.7 7 ). The relative ease of precipitation of fluorite from these water samples indicates that equilibrium with respect to fluorite may occur in some ground-water systems.

Idaho↗
USGS1977

Urban and regional land use change detected by using Landsat data

The Atlanta Regional Commission and the Earth Resources Observation Systems Data Center participated in a demonstration of the use of Landsat digital data to detect land use change in the Atlanta, Ga., area. Temporal overlays combining Landsat band-5 data from October 1972 and 1974 were made by using the General Electric Image 100 system. The 1972 data were divided by the 1974 data, and low ratios indicate areas where land use and land cover had changed. These low ratios were classified into a land-use-change theme. A classification based on the use of the four bands of the multispectral scanner data, taken in 1974, yielded six land use categories: (1) Commercial-industrial-multifamily, (2) single-family residential, (3) cleared land, (4) open space, (5) forested land, and (6) water. These six 1974 categories and the change theme were combined to determine changes between 1972 and 1974.

Georgia↗
USGS1978

Use of a remote computer terminal during field checking of Landsat digital maps

Field checking of small-scale land classification maps made digitally from Landsat data is facilitated by use of a remote portable teletypewriter terminal linked by teleplume to the IDIMS (Interactive Digital Image Manipulation System) at the EDC (EROS Data Center), Sioux Falls, S. Dak. When field checking of maps 20 miles northeast of Baker, Calif., during the day showed that changes in classification were needed, the terminal was used at night to combine image statistical files, remap portions of images, and produce new alphanumeric maps for field checking during the next day. The alphanumeric maps can be used without serious difficulty in location in the field even though the scale is distorted, and statistical files created during the field check can be used for full image classification and map output at the EDC. This process makes field checking faster than normal, provides interaction with the statistical data while in the field, and reduces to a minimum the number of trips needed to work interactively with the IDIMS at the EDC, thus saving significant amounts of time and money. The only significant problem is using telephone lines which at times create spurious characters in the printout or prevent the line feed (paper advance) signal from reaching the terminal, thus overprinting lines which should be sequential. We recommend that maps for field checking be made with more spectral classes than are expected because in the field it is much easier to group classes than to reclassify or separate classes when only the remote terminal is available for display.

Journal of Research of the U.S. Geological Survey↗
USGS1978

Regional gravity and magnetic anomalies in the eastern Snake River Plain, Idaho

Over the eastern Snake River Plain, the Bouguer gravity anomaly and the magnetic intensity are, in general, high. In detail, both the gravity and the magnetic anomalies are a complex of highs and lows, in contrast to the simpler anomalies over the western Snake River Plain. The broad gravity high associated with the eastern Snake River Plain cannot be produced by a dense mass at shallow depth under the plain, but must be produced either by a deep feature under the plain or by a broader, shallower feature extending well beyond the plain. The high could be produced by a thinning of the crust under the plain by 4.5 to 7 kilometers. The data suggest that the Cenozoic rocks of the plain are underlain by rocks that have density and magnetization similar to the density and magnetization of the pre-Cenozoic rocks north and south of the plain. The data do not suggest rifting of the upper crust such as is inferred for the western Snake River Plain. The plain is in approximate isostatic equilibrium with adjoining regions to the north and south and thus contrasts with the adjoining areas where the basin-and-range topography is not in isostatic equilibrium. The local gravity anomalies on the plain are probably produced by variations in the thickness of Cenozoic rocks, but the wavelength of the anomalies is about twice that of the basin-and-range structural features in areas adjoining the plain. The gravity expression of basin-and-range structural features does not extend far onto the plain. Magnetic anomalies on the plain are produced by Cenozoic volcanic rocks.

Idaho↗
USGS1978

Helium in soil gases of the Roosevelt Hot Springs Known Geothermal Resource Ares, Beaver County, Utah

Soil samples were collected in two parallel traverses across the Dome fault zone of the Roosevelt Hot Springs Known Geothermal Resource Area. The samples were sealed in air-tight aluminum cans, and the soil gas was allowed to equilibrate with the atmospheric air in the cans. Gas from the cans was analyzed by mass spectrometry. Samples collected over faults contained anomalously high concentrations of helium. Samples collected close to a geothermal well 884 m deep contained more helium than samples collected near another geothermal well 1370 m deep.

Utah↗
USGS1978

CS 2 and COS in soil gases of the Roosevelt Hot Springs Known Geothermal Resource Area, Beaver County, Utah

Soil-gas samples were collected in two parallel traverses across the Dome fault zone of the Roosevelt Hot Springs Known Geothermal Resource Area. Gas chromatographic analyses of the samples showed anomalous concentrations of CS 3 and COS east of the Dome fault; higher concentrations of CS 2 and COS also occurred over an area in which the hydrothermal system is close to the surface. Measurement of these gases may be useful in exploration for new geothermal sources.

Utah↗
USGS1978

Petrographic differentiation of depositional environments of sandstones of the Pennsylvanian Breathitt Formation, northeastern Kentucky and southwestern West Virginia

Petrographic properties of sandstone samples from the lower and middle Pennsylvanian Breathitt Formation in northeastern Kentucky and southwestern West Virginia were utilized to classify their environments of deposition. Simultaneous consideration of mineral composition, grain size, and sorting of the sandstones by using stepwise multiple discriminant-function analysis has permitted differentiation between alluvial-plain and delta-plain sandstones. Stepwise multiple discriminant-function analysis of the sandstone samples- was performed in two parts. The first analysis assigned the sandstones of all grain-size classes to one of three environments of deposition: (1) alluvial plain, (2) upper delta plain, and (3) lower delta plain. The second analysis classed the sandstones by grain size and subdivided each grain-size class into these environmental groups. Discriminant analyses of sandstones of all grain-size classes led to correct assignment of depositional environment to 76 percent of the samples. Analyses of the sandstones classed by grain size led to correct classification of 67 percent of the medium-grained sandstones, 83 percent of the fine-grained sandstones, and 91 percent of the very fine grained sandstones. The discriminantfunction method was adopted to classify the depositional environment and stratigraphic position of test sandstone samples. Analyses of fine-grained and very fine grained sandstones resulted in correct classification of 84 percent of the test samples to their depositional setting and stratigraphic position. The best discrimination is offered by analyses of fine-grained sandstones, which resulted in correct classification of 88 percent of the samples. Thus, this statistical method can be adopted as a powerful tool for exploration programs that concern delineation of genetically similar sandstones.

Kentucky, Virginia↗
USGS1978

Ferroaxinites from the Feather River area, northern California, and from the McGrath and Russian Mission quadrangles, Alaska

In the Feather River area, California, and in the McGrath quadrangle, Alaska, axinite-bearing veins occur as fracture fillings along or near the fault zones, suggesting that boron was introduced along the fractures. An unusual occurrence of axinite as a possible primary constituent of a plutonic rock is in the Russian Mission quadrangle, Alaska. The four analyzed axinites from these widely different localities and from different host rocks are surprisingly similar in chemistry and optics. All are ferroaxinites, having high iron and low manganese and magnesium contents. The number of calcium ions is very close to two, which is in agreement with the idealized formula Ca 2 (Fe,Mn,Mg)Al 2 BSi 4 O 15 (OH). The indices of refraction increase slightly with increasing FeO:MgO ratio over the small range studied.

California, Alaska↗
USGS1978

Holocene pyroclastic-flow deposits from Shastina and Black Butte, west of Mount Shasta, California

A broad apron of pyroclastic-flow deposits derived from dacitic domes of Holocene age at Black Butte and Shastina covers an area of more than 110 km 2 on the west flank of Mt. Shasta volcano. The stratigraphy of the deposits is exposed in readouts along a northwest-southeast line between the cities of Weed and Mount Shasta and includes, from bottom to top, pre-Shastina diamictons, a Shastina pyroclasticflow assemblage, and a Black Butte pyroclastic-flow assemblage. Pyroclastic flows from Shastina, a volcanic cone on the west flank of Mt. Shasta, form a fan of nonvesicular rock debris that overlies part of the Shastina cone and pre-Shastina deposits; the fan deposits thicken northward and underlie the town of Weed. Pyroclastic-flow deposits of both vesicular and nonvesicular rock debris caused by eruptions at the site of Black Butte, a large volcanic dome at the foot of Mt. Shasta, thicken southward and underlie part of the city of Mount Shasta. Soil-profile oxidation is 75-80 cm thick on deposits from both Shastina and Black Butte. As much as 10 m of vertical displacement occurred along east-trending faults 3.5 km northwest of Black Butte after deposition of the youngest two pyroclastic flows from that source. Evidence that faulting and volcanism were nearly simultaneous suggests that the area northwest of Black Butte subsided during a late eruptive phase of the plug dome. Future eruptions similar to those that produced the pyroclastic flows could endanger people and property in any direction downslope from vents, including the communities of Weed and Mount Shasta and possibly other communities in the Shasta Valley and upper Sacramento River area.

California↗
USGS1978

Tribolbina Latham, 1932, an early Carboniferous through Permian palaeocopid ostracode genus

The type-species of Tribolbina Latham, 1932, T. carnegiei , and T. gigantea (Jones, Kirkby, and Brady, 1884) are redefined and reillustrated, and lectotypes for both are designated. T. permiana (Kellett, 1933) and T. tumida (Scott and Borger, 1941) are also redefined and reillustrated. Beyrichiana Kellett, 1933, is considered a junior subjective synonym of Tribolbina Latham, 1932. On the basis of abundant silicified specimens from the Permian of Greece, T. doescheri n. sp. is described, and T. aff. T. doescheri and T . sp. 1 are illustrated. The stratigraphic range of Tribolbina as redefined is lower Carboniferous through Permian, and its known distribution is Europe and North America where representatives lived in shallow seas. Tribolbinidae and Tribolbinecea are established as new suprageneric categories in the Palaeocopida for Tribolbina and the Silurian Kolmodinia Martinsson, 1962.

Episkopi↗
USGS1977

Application of a selenium hydride-atomic absorption technique to test for homogeneity of USGS standard rock

After acid decomposition of the sample, selenium hydride was generated by means of sodium borohydride, and the gas was swept through a resistance-heated quartz cell mounted in an atomic absorption spectrometer to determine as little as 5 ng/g selenium in 0.25 g rock sample. One-way analyses of variance of data from nine USGS standard rocks indicated no significant differences in selenium content among bottles of any of these rocks.

Journal of Research of the U.S. Geological Survey↗
USGS1977

Determination of arsenic, antimony, and selenium in coal by atomic absorption spectrometry with a graphite tube atomizea

Submicrogram quantities of antimony, arsenic, and selenium in coal samples are determined by an atomic absorption procedure using an electrically heated graphite atomizer. The samples are decomposed in a mixture of nitric, sulfuric, and perchloric acids and are separated and concentrated by extraction from sulfuric acid-iodide solution into toluene. The results obtained on several intralaboratory reference samples and the National Bureau of Standards coal 1632 are compared with results from other methods. The determination can be made routinely for concentrations as small as 0.1 parts per million for arsenic, antimony, and selenium in the coal.

Journal of Research of the U.S. Geological Survey↗