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At least 145 records · Page 8Linked to original sources
USGS2010

Distribution and mode of occurrence of radionuclides in phosphogypsum derived from Aqaba and Eshidiya Fertilizer Industry, South Jordan

Phosphogypsum (PG) is a by-product of the chemical reaction called the "wet process" whereby sulphuric acid reacts with phosphate rock (PR) to produce phosphoric acid, needed for fertilizer production. Through the wet process, some impurities naturally present in the PR become incorporated in PG, including U decay-series radionuclides, are the main important concern which could have an effect on the surrounding environment and prevent its safe utilization. In order to determine the distribution and bioavailability of radionuclides to the surrounding environment, we used a sequential leaching of PG samples from Aqaba and Eshidiya fertilizer industry. The results showed that the percentages of 226Ra and 210Pb in PG are over those in the corresponding phosphate rocks (PG/PR), where 85% of the 226Ra and 85% of the 210Pb fractionate to PG. The sequential extraction results exhibited that most of 226Ra and 210Pb are bound in the residual phase (non-CaSO4) fraction ranging from 45-65% and 55%-75%, respectively, whereas only 10%-15% and 10%-20% respectively of these radionuclides are distributed in the most labile fraction. The results obtained from this study showed that radionuclides are not incorporated with gypsum itself and may not form a threat to the surrounding environment. ?? 2010 Science Press, Institute of Geochemistry, CAS and Springer Berlin Heidelberg.

Chinese Journal of Geochemistry↗
USGS2015

Application of U-Th-Pb phosphate geochronology to young orogenic gold deposits: New age constraints on the formation of the Grass Valley gold district, Sierra Foothills province, California

The Grass Valley orogenic gold district in the Sierra Nevada foothills province, central California, the largest historic gold producer of the North American Cordillera, comprises both steeply dipping east-west (E-W) veins located along lithologic contacts in accreted ca. 300 and 200 Ma oceanic rocks and shallowly dipping north-south (N-S) veins hosted by the Grass Valley granodiorite; the latter have yielded about 70 percent of the 13 million ounces of historic lode gold production in the district. The oceanic host rocks were accreted to the western margin of North America between 200 and 170 Ma, metamorphosed to greenschist and amphibolite facies, and uplifted between 175 and 160 Ma. Large-scale magmatism in the Sierra Nevada occurred between 170-140 Ma and 120-80 Ma, with the Grass Valley granodiorite being emplaced during the older episode of magmatism. Uranium-lead isotopic dating of hydrothermal xenotime yielded the first absolute age of 162&plusmn;5 Ma for the economically more significant N-S veins. The vein-hosted xenotime, as well as associated monazite, are unequivocally of hydrothermal origin as indicated by textural and chemical characteristics, including grain shape, lack of truncated growth banding, lack of a Eu anomaly, and low U and Th concentrations. Furthermore, the crack-seal texture of the veins, with abundant wallrock slivers, suggests their formation as a result of episodic fluid flow possibly related to reoccurring seismic events, rather than a period of fluid exsolution from an evolving magma. The N-S veins are temporally distinct from a younger 153-151 Ma gold event that was previously reported for the E-W veins. Overlapping U-Pb zircon (159.9&plusmn;2.2 Ma) and 40Ar/39Ar biotite and hornblende (159.7&plusmn;0.6 to 161.9&plusmn;1.4 Ma) ages and geothermobarometric calculations indicate that the Grass Valley granodiorite was emplaced at ca. 160 Ma at elevated temperatures (~800&deg;C) within approximately 3 km of the paleosurface and rapidly cooled to the ambient temperature of the surrounding country rocks (<300&deg;C). The age of the granodiorite is indistinguishable from that of the N-S veins, as recorded by the U-Pb age of xenotime in those veins. Consequently, the N-S veins must have formed between 162 and 157 Ma, the maximum permissive age of magma emplacement and the youngest permissive xenotime U-Pb age, respectively, during an E- to ENE-directed compressional regime. The geochemistry of the Grass Valley granodiorite is consistent with it being the product of arc magmatism. It served as a receptive host for mineralization, but it is has no direct genetic relationship to gold mineralization. Initial uplift of the intrusive mass correlates with the initial voluminous fluid flow event and vein formation at depths of no greater than 3 km. The E-W gold-bearing veins hosted within greenschist-facies country rocks adjacent to the intrusion formed during a second hydrothermal event 5-10 million years later than the magmatism and were contemporaneous with a shift to a transtensional deformation denoted by sinistral strike-slip faulting.

California↗
USGS2002

Ubiquitous tar balls with a California-source signature on the shorelines of Prince William Sound, Alaska

Although the shorelines of Prince William Sound still bear traces of the 1989 Exxon Valdez oil spill, most of the flattened tar balls that can be found today on these shorelines are not residues of Exxon Valdez oil. Instead, the carbon-isotopic and hydrocarbonbiomarker signatures of 61 tar ball samples, collected from shorelines throughout the northern and western parts of the sound, are all remarkably similar and have characteristics consistent with those of oil products that originated from the Monterey Formation source rocks of California. The carbonisotopic compositions of the tar balls are all closely grouped (<513Cpdb = -23.7 ± 0.2%o), within the range found in crude oils from those rocks, but are distinct from isotopic compositions of 28 samples of residues from the Exxon ValdezoW spill (<513Cpdb = -29.4 ± 0.1%o). Likewise, values for selected biomarker ratios in the tar balls are all similar but distinct from values of residues from the 1989 oil spill. Carbon-isotopic and biomarker signatures generally relate the tar balls to oil products used in Alaska before ~1970 for construction and pavements. How these tar balls with such similar geochemical characteristics became so widely dispersed throughout the northern and western parts of the sound is not known with certainty, but the great 1964 Alaska earthquake was undoubtedly an important trigger, causing spills from ruptured storage facilities of California-sourced asphalt and fuel oil into Prince William Sound.

Alaska↗
USGS1951

Iron formation and associated rocks in the Iron River district, Michigan

The iron formation of the Iron River district is part of a Precambrian sequence of strata characterized by a high iron content and varied mineralogy. The iron formation, where unoxidized, consists largely of interlaminated chert and siderite. It is underlain by a graphitic slate containing about 20 per cent iron in the form of very finely disseminated pyrite. Graywacke overlies the iron formation with at least local disconformity; this rock consists of clastic grains in a matrix of siderite or iron-rich chlorite. Above the gray-wacke is a magnetic ironstone, a laminated rock that now consists of iron-rich chlorite, magnetite, chert, and siderite, each layer being an intermixture of two or more of these constituents. The average iron content of the entire sequence, including the iron formation, is approximately 20 per cent. The rocks are only slightly metamorphosed, although the area is one of intense structural deformation. The origin of the rocks is discussed, and it is concluded that the high iron content is primary. The rocks are believed to be the products of an era of iron-rich sedimentation in which the specific iron mineral formed —sulfide, carbonate, or silicate—depended upon the immediate depositional environment. Inasmuch as the formation of iron-rich minerals continued despite extensive changes in both the basin of deposition and the adjacent land areas, the ultimate cause for such an epoch is one that transcended such factors. Evidence is presented to show that the climate of the era, when linked with certain other factors, is entirely adequate to explain the formation of these iron-rich rocks.

Michigan↗
USGS1979

Ground-water resources of Monroe County, Pennsylvania

Monroe County is on the eastern border of Pennsylvania and includes much of the area popularly called the Poconos. It is an area long used for outdoor recreation and includes a part of the Delaware Water Gap National Recreation Area. Water resources in the county are derived from precipitation. The Lehigh and Delaware Rivers, bordering the northwestern and southeastern parts, respectively, are the drains for surface-water and ground-water discharge and are essentially unused for water supply. Water budgets were calculated for average conditions when annual precipitation is 45 in. Sixty percent of this or 27 in. runs off and 65 percent of that runoff or 17 in. moves through the ground-water reservoir. Evapotranspiration varies little between wet and dry years and averages 18 in. Bedrock consists of Silurian and Devonian sedimentary rocks, which are intensely deformed by folding in the southeastern third of the county and are moderately deformed in the remainder. During the Pleistocene Epoch, glaciers repeatedly advanced across most of the county. The last of these advances deposited a terminal moraine that extends across the southwestern part of the county. The glaciers eroded pre-existing deposits, veneered the upland, and filled valleys with unconsolidated deposits that changed surface-water drainage and altered ground-water gradients. Water occurs in fractures and solution openings in the consolidated rocks and in intergranular openings in the unconsolidated rocks and weathered calcareous sandstones. Water that reaches the water table moves down the hydraulic gradient to points of discharge, moving both laterally and vertically away from ground-water divides and toward streams. The thickness of the fresh-water system is 800 ft or more, but little water is yielded to wells by aquifers more than 500 ft below land surface. Ground-water recharge is 600 to 650 (gal/min)/mi 2 ; and about 1.6 billion gallons per square mile is stored in the ground-water reservoir. Currently the most productive wells are in consolidated-rock aquifers; however, specific-capacity data suggest that wells in the unconsolidated deposits have potentially larger yields. Well yield is affected primarily by the distribution, size, and interconnection of the water-bearing openings and by topographic location, available recharge, well-depth, location within the flow system, pumping rate and duration of pumping, and interference from other pumping wells. Potential yields of properly located, drilled, and developed wells have been calculated for the aquifers. The median yields calculated from specific capacity data from the unconsolidated deposits, are 200 gal/min; from the Bloomsburg Formation, 100 gal/min; and from the Poplar Gap Member of the Catskill Formation, 70 gal/min. Median yields of the other units range from 15 to 40 gal/min. In general, enough water for domestic use can be obtained throughout the county. Large-scale development and consumptive use of the ground water will diminish baseflow of the streams. The temperature of water measured in wells ranges from 44° to 57°F and is largely dependent on altitude of the land surface and depth to the producing zone. Hardness of water in the noncarbonate rocks averages 3 to 4 grains per gallon, or about half that of the carbonate rocks. Water from most of the bedrock aquifers is low in dissolved solids, acidic, and soft. In carbonate rocks, the water tends to be hard and slightly alkaline. Excessive amounts of iron and manganese are encountered in water from the unconsolidated deposits and, locally, from the Catskill and Shawangunk Formations.

Pennsylvania↗
USGS2023

Rock-to-metal ratios of the rare earth elements

The relative quantities of ore mined and waste rock (i.e., overburden) removed to produce the rare earth elements—their rock-to-metal ratios—were calculated for 21 individual operations or regions covering nearly all mine production in 2018. The results indicate that the rock-to-metal ratios for the total rare earth elements ranged from a low of 1.6 × 10 1 to a high of 3.6 × 10 3 , with operations in Brazil and Russia having the lowest ratios and ion-adsorption clays operations in China and Myanmar having the highest. For comparison, the global average rock-to-metal ratio for the total rare earth elements (9.8 × 10 2 ) fell between that of cobalt (8.6 × 10 2 ) and tungsten (1.1 × 10 3 ). Driven by their relative abundance in the ore and unit prices that were used in the economic allocation of the environmental burdens, the global rock-to-metal ratio for individual rare earth elements was lowest for cerium (2.3 × 10 1 ) and lanthanum (7.7 × 10 1 ) and highest for dysprosium (1.7 × 10 4 ), terbium (3.7 × 10 4 ), and lutetium (6.4 × 10 4 ). Like the rock-to-metal ratios for the total rare earth elements, rock-to-metal ratios for individual rare earth elements varied by roughly two orders of magnitude among the various operations examined. An alternative perspective of only accounting for the overburden that is physically removed in ion-adsorption clays in-situ operations yielded global rock-to-metal ratios that were an order of magnitude lower or less for many of the rare earth elements.

Journal of Cleaner Production↗
USGS1971

Chemical compositions of rock types as factors in our environment

The types of rocks that form geologic units in the Earth’s crust supply most of the raw materials from which soils are formed and from which water derives its inorganic constituents. The compositions of what we eat and drink thus depend in part upon the compositions of the source rocks. Igneous rocks are formed by crystallization and solidification of a rock melt. Metamorphic rocks are formed by recrystallization of both igneous and sedimentary rocks caused by heat and pressure within the Earth’s crust. Sedimentary rocks are formed chiefly by the deposition in water of weathering and erosion products of pre-existing igneous, metamorphic, or other sedimentary rocks. The compositions of metamorphic rocks are generally similar to the compositions of the rocks that were metamorphosed, and only igneous and sedimentary rock compositions are considered here. Igneous rocks range in SiO 2 content from about 40 to nearly 80 percent, and other constituents increase in amount as SiO 2 decreases. The changes in the other constituents are not large, however, except for the quantitatively unimportant least silicic rocks; these contain conspicuously more magnesium and less aluminum than the other kinds of igneous rocks. Sedimentary rocks range in SiO 2 content from nearly zero for the carbonate rocks to almost 100 percent for quartzite and pure sandstone. Shale and clay contain intermediate amounts of SiO 2 and as much as 25 percent AI 2 O 3 , more than any of the igneous rocks. Carbonate rocks are composed mostly of calcium and magnesium carbonates. The contents of individual trace elements vary widely with rock type. Chromium, titanium, nickel, and cobalt are conspicuously concentrated in low-silica igneous rocks that are quantitatively unimportant. Arsenic, iodine, molybdenum, and selenium are conspicuously concentrated in shale and clay. In addition, most other elements occur in largest amounts in shale and clay compared to other sedimentary rocks, and in amounts nearly equal to those in igneous rocks. Soils derived from different kinds of igneous rocks do not differ from each other as much as do soils derived from different kinds of sedimentary rocks. This is partly because igneous rocks generally are more resistant to weathering than sedimentary rocks that were deposited in water. Some of the important constituents of sedimentary rocks have been precipitated from solution, which makes them more susceptible to weathering and re-solution. Similarly, sedimentary rocks have a greater effect than igneous rocks on the composition of ground water. Determination of areal variations in composition should be more detailed than normal petrologic investigations if the results are to be usable for environmental studies. Statistical principles should be used in planning the sampling, analysis, and interpretation of results.

Book chapter↗
USGS2010

Multiple well-shutdown tests and site-scale flow simulation in fractured rocks

A new method was developed for conducting aquifer tests in fractured-rock flow systems that have a pump-and-treat (P&T) operation for containing and removing groundwater contaminants. The method involves temporary shutdown of individual pumps in wells of the P&T system. Conducting aquifer tests in this manner has several advantages, including (1) no additional contaminated water is withdrawn, and (2) hydraulic containment of contaminants remains largely intact because pumping continues at most wells. The well-shutdown test method was applied at the former Naval Air Warfare Center (NAWC), West Trenton, New Jersey, where a P&T operation is designed to contain and remove trichloroethene and its daughter products in the dipping fractured sedimentary rocks underlying the site. The detailed site-scale subsurface geologic stratigraphy, a three-dimensional MODFLOW model, and inverse methods in UCODE_2005 were used to analyze the shutdown tests. In the model, a deterministic method was used for representing the highly heterogeneous hydraulic conductivity distribution and simulations were conducted using an equivalent porous media method. This approach was very successful for simulating the shutdown tests, contrary to a common perception that flow in fractured rocks must be simulated using a stochastic or discrete fracture representation of heterogeneity. Use of inverse methods to simultaneously calibrate the model to the multiple shutdown tests was integral to the effectiveness of the approach.

Groundwater↗
USGS1996

Eutrophication trends inferred from hypolimnetic dissolved-oxygen dynamics within selected White River reservoirs, northern Arkansas-southern Missouri, 1974-94

The White River Basin in northern Arkansas and southern Missouri contains four major reservoirs. Beaver, Table Rock, and Bull Shoals Lakes form a chain of reservoirs on the main stem of the White River. Norfork Lake is on the North Fork River, a tributary of the White River. Vertical water- column profiles of temperature and dissolved- oxygen concentrations have been collected monthly, in general, at sites near the dam of each reservoir since 1974. Hypolimnetic dissolved- oxygen dynamics of these reservoirs from 1974 through 1994 were examined based on the near-dam data and used to infer temporal changes in eutrophication. Regression models indicated that a positive relation existed between discharge through the dam during the stratification season and the areal hypolimnetic deficit. Temporal changes in the relative areal hypolimnetic oxygen deficit, a model that adjusts the areal hypolimnetic oxygen deficit to standard temperature and depth, showed a decreasing trend in Beaver Lake from 1974 through 1994, indicating that the level of eutrophication decreased. Little or no change in the relative areal hypolimnetic oxygen deficit occurred in Table Rock, Bull Shoals, or Norfork Lakes over the period of record. Temporal analysis of the residuals from the oxygen deficit-discharge model indicated that the oxygen deficit-discharge function changed over time in Beaver and Table Rock Lakes. There was little or no temporal trend in residuals of areal hypolimnetic oxygen deficit over the period of record for Bull Shoals and Norfork Lakes. Multiple regression using a time variable and discharge through the dam during the stratification season was examined for the four reservoirs. The slope coefficient of the time variable for both Beaver and Table Rock Lakes was negative, indicating that the temporal function driving the discharge related areal hypolimnetic oxygen deficit decreased over the period of record. This temporal function may be an expression of biological productivity or eutrophication. Based on these results, the level of eutrophication may have decreased in Beaver and Table Rock Lakes and remained stable in Bull Shoals and Norfork Lakes from 1974 through 1994. It is possible that the aging and evolutionary processes in Beaver, Table Rock, Bull Shoals, and Norfork Lakes are dominant in controlling biological productivity and eutrophication in each reservoir immediately above the dam. Beaver Lake is the youngest of the four reservoirs, constructed in 1963, and for the period of record, may have been in the initial stage of high productivity followed by a declining stage of productivity that generally occurs within a reservoir soon after impoundment. Table Rock Lake was constructed in 1959 and, for the period of record, may have been in the stage of declining productivity following the peak of productivity resulting from impoundment. The impoundment of Beaver Lake upstream also may have influenced the inferred decline of productivity within Table Rock Lake. Bull Shoals and Norfork Lakes are older than Beaver and Table Rock Lakes, constructed in 1951 and 1944, respectively. The reason that changes in eutrophication were not detected in Bull Shoals and Norfork Lakes could be that these reservoirs, for the period of record, were characterized by the stage of low and stable productivity that generally occurs within a reservoir many years after impoundment.

Water-Resources Investigations Report↗
USGS2012

Tektites in Cretaceous-Tertiary boundary rocks on Haiti and their bearing on the Alvarez impact extinction hypothesis

Relic tektites are associated with a Pt-group metal abundance anomaly and shocked minerals in a thin marl bed that marks the K-T boundary on Haiti. The presence of these three impact-produced materials at the precise K-T boundary enormously strengthens the Alvarez impact extinction hypothesis. The tektites occur in smectite spherules that have external shapes typical of tektites. Their chemical and physical properties are broadly similar to those of other tektite groups, except that the Haitian tektites have lower Si and higher Fe, Ca, and Na. On average, they contain more Sc, V, Cu, Zn, Ga, Sr, Sn, and Ba and less Cr, Ni, Co, B, Mn, and Hf than Other tektite groups. Amounts of rare earth elements (REE) in the tektites indicate that their progenitor materials were not melted mafic or ultramafic oceanic crust; rather they were sedimentary deposits having a bulk composition of andesite. Rare tektites contain unusually high amounts of CaO (∼20%) and S (0.4%), and these data suggest that some target materials consisted of CaSO 4 . Anhydrite beds occur in the subsurface at two candidate impact sites (Chicxulub and Manson). Sm-Nd isotopic data for the tektites indicate that the melted precursor sediments were most likely deposited less than −400 m.y. between the Late Cretaceous and Silurian periods. Major chemical changes accompanied the diagenetic change of glass to smectite. The Haitian tektites are the first datable impact products in K-T boundary rocks, and 40 Ar- 39 Ar ages of the glass show that the K-T boundary and impact event are coeval at 64.5±0.1 Ma.

Journal of Geophysical Research↗
USGS2017

Cobalt—Styles of deposits and the search for primary deposits

Cobalt (Co) is a potentially critical mineral. The vast majority of cobalt is a byproduct of copper and (or) nickel production. Cobalt is increasingly used in magnets and rechargeable batteries. More than 50 percent of primary cobalt production is from the Central African Copperbelt. The Central African Copperbelt is the only sedimentary rock-hosted stratiform copper district that contains significant cobalt. Its presence may indicate significant mafic-ultramafic rocks in the local basement. The balance of primary cobalt production is from magmatic nickel-copper and nickel laterite deposits. Cobalt is present in several carbonate-hosted lead-zinc and copper districts. It is also variably present in Besshi-type volcanogenic massive sulfide and siliciclastic sedimentary rock-hosted deposits in back arc and rift environments associated with mafic-ultramafic rocks. Metasedimentary cobalt-copper-gold deposits (such as Blackbird, Idaho), iron oxide-copper-gold deposits, and the five-element vein deposits (such as Cobalt, Ontario) contain different amounts of cobalt. None of these deposit types show direct links to mafic-ultramafic rocks; the deposits may result from crustal-scale hydrothermal systems capable of leaching and transporting cobalt from great depths. Hydrothermal deposits associated with ultramafic rocks, typified by the Bou Azzer district of Morocco, represent another type of primary cobalt deposit. In the United States, exploration for cobalt deposits may focus on magmatic nickel-copper deposits in the Archean and Proterozoic rocks of the Midwest and the east coast (Pennsylvania) and younger mafic rocks in southeastern and southern Alaska; also, possibly basement rocks in southeastern Missouri. Other potential exploration targets include— The Belt-Purcell basin of British Columbia (Canada), Idaho, Montana, and Washington for different styles of sedimentary rock-hosted cobalt deposits; Besshi-type VMS deposits, such as the Greens Creek (Alaska) deposit and the Ducktown (Tennessee) waste and tailings; and Known five-element vein districts in Arizona and New Mexico, as well as in the Yukon-Tanana terrane of Alaska; and hydrothermal deposits associated with ultramafic rocks along the west coast, in Alaska, and in the Appalachian Mountains.

Open-File Report↗
USGS2016

Alaska geology revealed

This map shows the generalized geology of Alaska, which helps us to understand where potential mineral deposits and energy resources might be found, define ecosystems, and ultimately, teach us about the earth history of the State. Rock units are grouped in very broad categories on the basis of age and general rock type. A much more detailed and fully referenced presentation of the geology of Alaska is available in the Geologic Map of Alaska ( http://dx.doi.org/10.3133/sim3340 ). This product represents the simplification of thousands of individual rock units into just 39 broad groups. Even with this generalization, the sheer complexity of Alaskan geology remains evident.

Alaska↗
USGS1969

Heat flow measurements on the southeast coast of Australia

Three boreholes have been drilled for the Australian National University near the southeast coast of New South Wales, Australia. The heat flows found are 1.1, 1.0, and 1.3 μcal/cm 2 sec. The errors resulting from the proximity of the sea and a lake, surface temperature change, conductivity structure and water flow have been examined. The radioactive heat production in some of the intrusive rocks of the area have also been measured. The heat flows are much lower than the values of about 2.0 found elsewhere in south eastern Australia. The lower values appear to be part of a distinct heat flow province in eastern Australia.

Earth and Planetary Science Letters↗
USGS2012

Development of vegetation based soil quality indices for mineralized terrane in arid and semi-arid regions

Soil quality indices (SQIs) are often management driven and attempt to describe key relationships between above- and below-ground parameters. In terrestrial systems, indices that were initially developed and modified for agroecosystems have been applied to non-agricultural systems in increasing number. We develop an SQI in arid and semi-arid ecosystems of the Western US impacted by different types of geologic mineralization using the relationship between vegetation community parameters and soil abiotic and biotic properties. We analyze these relations in soils associated with three different mineralization types: podiform chromite, Cu/Mo porphyry, and acid-sulfate gold vein systems at four different sites in California and Nevada. Soil samples were collected from undisturbed soils in both mineralized and nearby unmineralized substrates as well as from waste rock and tailings. Aboveground net primary productivity (ANPP), canopy cover and shrub density were measured for the vegetative communities. Minimum data sets were developed based on correlations between the soil and vegetation parameters, refined using principal components analysis, scored using non-linear functions, and combined into an overall SQI. The indices are comprised of one or two microbial parameters and three to six abiotic parameters, the latter consisting of nutrients and metals. Given the preliminary development of this approach, the parameters and combinations to arrive at an SQI for a given site cannot at this time be correlated or compared with that of another site. This SQI approach provides a means of quantifying disturbed ecosystem recovery resulting from mining, and could be applied to other disturbances in a way that readily distills the information for potential use by land managers. However, severely disturbed areas with little to no aboveground biomass, such as unreclaimed tailings, have likely crossed an ecological threshold that precludes the use of this type of monitoring tool.

California↗
USGS2008

Linking landscapes and habitat suitability scores for diadromous fish restoration in the susquehanna river basin

Dams within the Susquehanna River drainage, Pennsylvania, are potential barriers to migration of diadromous fishes, and many are under consideration for removal to facilitate fish passage. To provide useful input for prioritizing dam removal, we examined relations between landscape-scale factors and habitat suitability indices (HSIs) for native diadromous species of the Susquehanna River. We used two different methods (U.S. Fish and Wildlife Service method: Stier and Crance [1985], Ross et al. [1993a, 1993b, 1997], and Pardue [1983]; Pennsylvania State University method: Carline et al. [1994]) to calculate HSIs for several life stages of American shad Alosa sapidissima, alewives Alosa pseudoharengus, and blueback herring Alosa aestivalis and a single HSI for American eels Anguilla rostrata based on habitat variables measured at transects spaced every 5 km on six major Susquehanna River tributaries. Using geographical information systems, we calculated land use and geologic variables upstream from each transect and associated those data with HSIs calculated at each transect. We then performed canonical correlation analysis to determine how HSIs were linked to geologic and land use factors. Canonical correlation analysis identified the proportion of watershed underlain by carbonate rock as a positive correlate of HSIs for all species and life stages except American eels and juvenile blueback herring. We hypothesize that potential mechanisms linking carbonate rock to habitat suitability include increased productivity and buffering capacity. No other consistent patterns of positive or negative correlation between landscape-scale factors and HSIs were evident. This analysis will be useful for prioritizing removal of dams in the Susquehanna River drainage, because it provides a broad perspective on relationships between habitat suitability for diadromous fishes and easily measured landscape factors. This approach can be applied elsewhere to elucidate relationships between fine- and coarse-scale variables and suitability of habitat for fishes. ?? Copyright by the American Fisheries Society 2008.

North American Journal of Fisheries Management↗
USGS1962

Trace element distribution in the searchlight, Nevada quartz monzonite stock

Gold, silver, copper, and lead-bearing veins, non-radially zoned, occur just beyond the southern and western margins of the Searchlight , Nevada , quartz monzonite stock . Seven samples of the quartz monzonite and purified individual constituent minerals of the rock, representing apophyses and marginal and interior parts of the intrusive mass, were analyzed petrographically and spectrographically. A semiquantitative total-energy spectrographic method proved satisfactory for Cu, Pb, Ni, Co, Ga, Mo, Mn, Ti, V, Cr, Sr, and Zr, but too insensitive for Zn, Ag, and Au. A synthetic silicate base was used for preparation of standards and working curves. The modal trace element content of unaltered (hypothetical) quartz monzonite samples was determined from the trace element content of the purified minerals. Ferromagnesian minerals contain concentrations of Cu, Pb, Ni, Co, Mn, and Cr. Felsic minerals are low in these but high in Sr and Ga. Cu appears to have been partly released during chloritization of the mafic minerals. Ni, Cr, Zr show little difference between the unaltered (hypothetical) and actual rock. Ga, V, Mn, Sr are in lesser quantities in the altered rock. Pb and Cu also show a loss, especially nearest largest Pb and Cu producers. Pb, Cu, V occur in the spatially related veins, but Sr or Ga have not been reported to date. Pb/Cu in unaltered rock compared to altered rock is 1.6/1; past mining production ratio of Pb/Cu is 2.6/1. While further work is needed, the trace element pattern suggests a possible means of identifying a "productive" intrusive body.

Economic Geology↗
USGS2010

Magmatic sulfide-rich nickel-copper deposits related to picrite and (or) tholeiitic basalt dike-sill complexes: A preliminary deposit model

Magmatic sulfide deposits containing nickel (Ni) and copper (Cu), with or without (±) platinum-group elements (PGEs), account for approximately 60 percent of the world’s Ni production and are active exploration targets in the United States and elsewhere. On the basis of their principal metal production, magmatic sulfide deposits in mafic rocks can be divided into two major types: those that are sulfide-rich, typically with 10 to 90 percent sulfide minerals, and have economic value primarily because of their Ni and Cu contents; and those that are sulfide-poor, typically with 0.5 to 5 percent sulfide minerals, and are exploited principally for PGE. Because the purpose of this deposit model is to facilitate the assessment for undiscovered, potentially economic magmatic Ni-Cu±PGE sulfide deposits in the United States, it addresses only those deposits of economic significance that are likely to occur in the United States on the basis of known geology. Thus, this model focuses on deposits hosted by small- to medium-sized mafic and (or) ultramafic dikes and sills that are related to picrite and tholeiitic basalt magmatic systems generally emplaced in continental settings as a component of large igneous provinces (LIPs). World-class examples (those containing greater than 1 million tons Ni) of this deposit type include deposits at Noril’sk-Talnakh (Russia), Jinchuan (China), Pechenga (Russia), Voisey’s Bay (Canada), and Kabanga (Tanzania). In the United States, this deposit type is represented by the Eagle deposit in northern Michigan, currently under development by Kennecott Minerals.

Open-File Report↗