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At least 325 records · Page 18Linked to original sources
USGS1946

General principles of artificial ground-water recharge

The natural subterranean reservoirs formed by the porous and permeable rocks differ from surface reservoirs chiefly in that they have complex structure and great internal resistanc• to the How of water. Their full utilization requires systematic development based on the geology and hydrology of the aquifer and the principles of hydraulics distinctive of ground water. The methods of increasing recharge are of two kinds: (1) Indirect methods, in which increased recharge is accomplished by locating production wells as close as practicable to areas of rejected recharge or natural discharge, and (2) direct methods, in which water from surface sources is conveyed to points from which it percolates into a body of ground water. The direct methods can also be divided into two groups: (1) Recharge by surface application, and (2) recharge through wells. This paper discusses the different methods in relation to geologic structure and ground-water hydraulics and gives numerous examples.

Economic Geology↗
USGS1959

The geochemistry of rhenium, with special reference to its occurrence in molybdenite

Little has been added to our knowledge of the geochemistry of Re since the work of Noddack and Noddack in 1931, except that many determinations have been published of the Re content of molybdenite, the only present source. These determinations, 150 in all, have been assembled. The Re content of molybdenite ranges from none to 3,250 p.p.m. Re, and varies widely, even in samples from a single deposit. No generalizations are yet possible as to correlations of Re content with geological conditions of formation. Other possible sources of Re are considered briefly.

Economic Geology↗
USGS1992

A new model for tabular-type uranium deposits

Tabular-type uranium deposits occur as tabular, originally subhorizontal bodies entirely within reduced fluvial sandstones of Late Silurian age or younger. This paper proposes that belts of tabular-type uranium deposits formed in areas of mixed local and regional ground-water discharge shortly after deposition of the host sediments. The general characteristics of tabular-type uranium deposits, especially the most studied deposits, those in the Uravan mineral belt, Henry basin, and Grants uranium region, indicate that their essential feature was the formation at a density-stratified ground-water interface in areas of local and regional ground-water discharge. Reconstruction of the paleohydrogeology is the key to understanding the formation of these deposits. Gravity-driven ground water recharged in major highlands and discharged in lowlands at major concave changes in paleotopographic slope. Shallow local and deep regional ground-water systems were characterized by dilute and saline water, respectively. Typically, underlying marine rocks, especially evaporites, provided the solutes to the deep regional ground water. A density-stabilized interface existed at the ground-water divide between local and regional flow systems. Tabular-type uranium deposits formed where these divides or interfaces intersected pockets of reduction where organic matter accumulated. The precipitation of humate and uranium at an interface accounts for the tabular shape and the tendency of deposits to rise stratigraphically into the basin. Geologic ground-water controls that favor discharge, such as the pinch-out of major aquifers, are also favorable for uranium ore. The combination of topographic and geologic features that both cause discharge is most favorable for ore deposition.

Economic Geology↗
USGS2019

Resource Assessment Economic Filter (RAEF)—A graphical user interface supporting implementation of simple engineering mine cost analyses of quantitative mineral resource assessment simulations

Economic evaluations of undiscovered mineral resources provide important context in which to consider the results of quantitative mineral resource assessments. The U.S. Geological Survey economic analysis method uses a simple engineering cost model approach developed by the U.S. Bureau of Mines that applies mine and mill engineering cost equations to simulated undiscovered deposits. The important characteristics of these deposits are derived from Monte Carlo simulations that combine probabilistic estimates of undiscovered deposits that might occur in a study area and a grade-tonnage model defined for a specific deposit type. This report describes the Resource Assessment Economic Filter (RAEF), a graphical user interface (GUI) tool that applies a set of mine cost equations to the deposits under consideration. RAEF, which is written in the open-source statistical programming language R, is an easy-to-use tool to apply user-defined mine, mill, and study area parameters to simulated deposits. For a given deposit type, it estimates the undiscovered resources that might be economic to extract. In addition, RAEF provides a series of graphical, tabular, and statistical summaries that document the results of the economic filter analysis.

Techniques and Methods↗
USGS1946

Artificial recharge of artesian limestone at Orlando, Florida

The principal aquifer in the Orlando area consists of 900 feet or more of permeable artesian limestones of upper and middle Eocene age. As in most other parts of the Florida peninsula, these limestones are overlain by the Hawthorn formation of Miocene age which contains relatively impervious beds. The Hawthorn at Orlando is 45 to 200 feet thick and prevents or retards natural recharge to the lime. stones except where it is penetrated by what appear to be old sinkholes that are now filled with pervious material. Owing to the lack of adequate surface drainage, more than 200 wells have been drilled into the limestones in the Orlando area to drain streets, control lake levels, and dispose of sewage and other waste liquids. Generally the piezometric surface of the water in the limestones is fat enough below the land surface to allow drainage by gravity. As the limestones are cavernous, most of the wells have large capacities for receiving water and seldom become clogged although a considerable amount of rubbish is carried into them. The piezometric surface is conspicuously higher where drainage wells are concentrated, probably because of recharge through wells. However, the effect of the artificial recharge cannot be clearly differentiated from that of natural recharge. A deep-well current meter was used to determine the horizons at which the polluted surface water enters the limestones. The investigation was made in cooperation with the Florida Geological Survey and the Corps of Engineers of the U.S. Army.

Florida↗
USGS1988

Physiography of the western United States Exclusive Economic Zone

GLORIA (Geologic Long-Range Inclined Asdic) sidescan sonar images were collected over the entire Exclusive Economic Zone (EEZ) west of the conterminous United States. The continuous, overlapping, swath-mapping technique provides, for the first time, a reconnaissance plan view off the entire sea floor from the edge of the continental shelf to 370 km from shore. The mid-ocean ridges, transform faults, seamount provinces, and sediment fans that dominate this region of the EEZ are seen in detail, and many features never before mapped in this region, such as canyons, seamounts, and meandering channels, have been located. Marked differences are apparent in the morphology of the continental slope and in sedimentary features both on the slope and in the deep ocean. Anticlinal ridges and diapirs crossed by large submarine canyon systems are clearly defined on the continental slope north of the Mendocino Fracture Zone. In contrast, the slope south of the fracture zone is incised by a dense network of smaller scale canyons and only a few large canyon systems. The first-order causes of these differences are related to differences in tectonic setting between the subduction-dominated margin north of Cape Mendocino and the strike-slip-dominated margin to the south.

Geology↗
USGS2006

Teachers doing science: An authentic geology research experience for teachers

Fairmont State University (FSU) and the West Virginia Geological and Economic Survey (WVGES) provided a small pilot group of West Virginia science teachers with a professional development session designed to mimic experiences obtained by geology majors during a typical summer field camp. Called GEOTECH, the program served as a research capstone event complimenting the participants' multi-year association with the RockCamp professional development program. GEOTECH was funded through a Improving Teacher Quality Grant administered by West Virginia Higher Education Policy Commission. Over the course of three weeks, eight GEOTEACH participants learned field measurement and field data collection techniques which they then applied to the construction of a surficial geologic map. The program exposed participants to authentic scientific processes by emphasizing the authentic scientific application of content knowledge. As a secondary product, it also enhanced their appreciation of the true nature of science in general and geology particular. After the session, a new appreciation of the effort involved in making a geologic map emerged as tacit knowledge ready to be transferred to their students. The program was assessed using pre/post instruments, cup interviews, journals, artifacts (including geologic maps, field books, and described sections), performance assessments, and constructed response items. Evaluation of the accumulated data revealed an increase in participants demonstrated use of science content knowledge, an enhanced awareness and understanding of the processes and nature of geologic mapping, positive dispositions toward geologic research and a high satisfaction rating for the program. These findings support the efficacy of the experience and document future programmatic enhancements.

Journal of Geoscience Education↗
USGS2011

Digital Mapping Techniques '09-workshop proceedings, Morgantown, West Virginia, May 10-13, 2009

The Digital Mapping Techniques '09 (DMT'09) workshop was attended by 90 technical experts from 42 agencies, universities, and private companies, including representatives from 24 State geological surveys. This workshop, the thirteenth in the annual series, was hosted by the West Virginia Geological and Economic Survey, May 10-13, 2009, on the West Virginia University campus in Morgantown, West Virginia. Each DMT workshop has been coordinated by the National Geologic Map Database project and the Association of American State Geologists (AASG). As in the previous years' meetings, the objective was to foster informal discussion and exchange of technical information, principally in order to develop more efficient methods for digital mapping, cartography, GIS analysis, and information management. At this meeting, oral and poster presentations and special discussion sessions emphasized (1) methods for creating and publishing map products (here, "publishing" includes Web-based release); (2) field data capture software and techniques, including the use of LiDAR; (3) digital cartographic techniques; (4) migration of digital maps into ArcGIS Geodatabase format; (5) analytical GIS techniques; and (6) continued development of the National Geologic Map Database.

Open-File Report↗
USGS1984

U. S. GEOLOGICAL SURVEY'S RESEARCH PROGRAM IN THE NEWLY PROCLAIMED EXCLUSIVE ECONOMIC ZONE.

The U. S. Geological Survey (USGS) has been developing a program which would emphasize broad-scale surveys of the continental margin and intensive studies of 'baseline corridors' in various areas of the U. S. EEZ to gather energy and mining information in this new frontier as quickly as possible. Of twelve baseline corridors identified to date along the east and west coasts and the Gulf of Mexico, the highest priority would be placed on areas off the west coast, including Juan De Fuca and Gorda Ridges and off Hawaii. Each corridor assessment will involve collection of multi-channel and high resolution geophysical data, bottom relief and sampling, and production of reports and cartographic products displaying the scientific findings of the assessments.

Conference Paper↗
USGS2015

Book review: Natural resources in Afghanistan: Geographic and geologic perspectives on centuries of conflict

This book is the outcome of four decades of work in Afghanistan by the author, John (Jack) Shroder. His travels and research throughout Afghanistan and his understanding of its place in regional and world history provide the foundation for this comprehensive 572-page reference. The book describes the interrelated nature of Afghanistan’s physical and political landscape over time and the role resources have, and have not, played in Afghanistan’s past and could play in its future. Review info: Natural resources in Afghanistan: Geographic and geologic perspectives on centuries of conflict by John F. Shroder, 2014. ISBN 978-01280013356, 572 pp.

Economic Geology↗
USGS1971

Ore fluids in the porphyry copper deposit at Copper Canyon, Nevada

The large, low-grade copper and gold deposit at Copper Canyon, Lander County, Nevada, formed in the contact metasomatic environment adjacent to a shallow Tertiary intrusion. Vein and disseminated chalcopyrite-pyrite-pyrrhotite-arsenopyrite mineralization, with lesser amounts of gold, galena, sphalerite, marcasite, and siderite occur in the Upper Cambrian Harmony and Middle Pennsylvanian Battle Formations. Studies of fluid inclusions in stages of vein quartz and in healed fractures through quartz phenocrysts and pebbles reveal the presence of very saline, sometimes CO 2 -rich fluids in the early and middle stages of mineralization. Ore fluid salinities during the base metal mineralization were approximately 40 wt percent, and temperatures were near 375 degrees C. Circulation of this hot brine was apparently restricted to an elongate highly fractured zone within 3,000 feet laterally of the intrusive. Later fluids in this central zone were somewhat cooler, near 300 degrees C, and had significantly lower salinities in the range 12 to 1.2 wt percent. Smaller lode deposits approximately 1 to 5 miles from the intrusion appear to have formed from low to moderate salinity fluids at temperatures generally in the range 250 to 335 degrees C. Geologic and fluid considerations suggest formation at approximately 6,000 feet in depth.

Nevada↗
USGS1951

Stabilization of some rockslides in Grainger County, Tennessee

Slides in dipping Cambrian sandstone, resulting from highway relocation along Norris Reservoir, have been stabilized by the use of steel dowels and concrete anchor blocks. Geologic conditions favored this type of treatment, as sliding took place in thin shales between thick sandstone beds.

Tennessee↗
USGS1983

Map showing characteristics of lode gold in the Medford 1 degree by 2 degrees Quadrangle, Oregon-California

About 500 lode gold occurrences, prospects, and mines have been reported from the Medford 1 o x 2 o quadrangle, Oregon-California. Summary descriptions of individual lode gold deposits and districts which include those occurrences in the Medford 1 o x 2 o quadrangle have been published by Brooks and Ramp (1968) and Hotz (1971) and by others cited in the reference lists in these two publications. As part of the Medford CUSMAP project between 1974 and 1980, some of these deposits were examined in the field during geologic mapping and geochemical sampling and most of the available information on individual deposits was compiled into a CRIB computer file (Computerized Resource Information Bank). This report is a summary of the more pertinent geologic and economic characteristics of the lode gold deposits for use in the resource evaluation part of the Medford CUSMAP project. The significant features described include the distribution of deposits and their relation to gross geologic and lithologic features, production information, mineralogy of the ore and gangue, gold-silver ratios, and speculations on possible genetic models for some types of deposits.

California, Oregon↗
USGS2000

Regional Crustal Structures and Their Relationship to the Distribution of Ore Deposits in the Western United States, Based on Magnetic and Gravity Data

Upgraded gravity and magnetic databases and associated filtered-anomaly maps of western United States define regional crustal fractures or faults that may have guided the emplacement of plutonic rocks and large metallic ore deposits. Fractures, igneous intrusions, and hydrothermal circulation tend to be localized along boundaries of crustal blocks, with geophysical expressions that are enhanced here by wavelength filtering. In particular, we explore the utility of regional gravity and magnetic data to aid in understanding the distribution of large Mesozoic and Cenozoic ore deposits, primarily epithermal and porphyry precious and base metal deposits and sediment-hosted gold deposits in the western United States cordillera. On the broadest scale, most ore deposits lie within areas characterized by low magnetic properties. The Mesozoic Mother Lodge gold belt displays characteristic geophysical signatures (regional gravity high, regional low-to-moderate background magnetic field anomaly, and long curvilinear magnetic highs) that might serve as an exploration guide. Geophysical lineaments characterize the Idaho-Montana porphyry belt and the La Caridad-Mineral Park belt (from northern Mexico to western Arizona) and thus indicate a deep-seated control for these mineral belts. Large metal accumulations represented by the giant Bingham porphyry copper and the Butte polymetallic vein and porphyry copper systems lie at intersections of several geophysical lineaments. At a more local scale, geophysical data define deep-rooted faults and magmatic zones that correspond to patterns of epithermal precious metal deposits in western and northern Nevada. Of particular interest is an interpreted dense crustal block with a shape that resembles the elliptical deposit pattern partly formed by the Carlin trend and the Battle Mountain-Eureka mineral belt. We support previous studies, which on a local scale, conclude that structural elements work together to localize mineral deposits within regional zones or belts. This study of mineral deposits of the western United States demonstrates the ability of magnetic and gravity data to elucidate the regional geologic framework or structural setting and to contribute in locating favorable environments for hydrothermal mineralization.

Economic Geology↗