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At least 973 records · Page 54Linked to original sources

USGS1989

Multiple hydrothermal and metamorphic events in the Kidd Creek volcanogenic massive sulphide deposit, Timmins, Ontario: evidence from tourmalines and chlorites

Tourmaline and chlorite are the principal ferromagnesian silicate minerals in the Kidd Creek massive sulphide deposit. Tourmaline is most common in sphalerite-rich peripheral margins of the chalcopyrite stringer zone. Within the north orebody, samples typically contain <1% tourmaline, but small areas (hand-specimen scale) may have 10–20%. Chlorite is more widely distributed and in places constitutes 30–50% of rock volumes. Associated assemblages may include quartz, sulphides (principally chalcopyrite, sphalerite, and (or) pyrite), carbonate, albite, sericite, and rare fluorite, allanite, or zoisite(?).The tourmalines and chlorites record a series of multiple hydrothermal and metamorphic events. Paragenetic studies suggest that tourmaline was deposited during several discrete stages of mineralization, as evidenced by brecciation and cross-cutting relationships. Most of the tourmalines have two concentric growth zones defined by different colours (green, brown, blue, yellow). Some tourmalines also display pale discordant rims that cross-cut and embay the inner growth zones and polycrystalline, multiple-extinction domains. Late sulphide veinlets (chalcopyrite, pyrrhotite) transect the inner growth zones and pale discordant rims of many crystals. The concentric growth zones are interpreted as primary features developed by the main ore-forming hydrothermal system, whereas the discordant rims, polycrystalline domains, and cross-cutting sulphide veinlets reflect post-ore metamorphic processes.Detailed electron microprobe analyses of tourmalines show a wide compositional range, from Fe-rich dravite nearly to end-member schorl, with Fe/(Fe + Mg) ratios varying from 0.33 to 0.92; only minor amounts of Ca are present, yielding uniformly high Na/(Na + Ca) ratios of 0.84–0.99. Two sets of chemical zoning trends are identified in the tourmalines, involving systematic changes in Fe/(Fe + Mg), Na/(Na + Ca), Al, and Ti that are believed to reflect internal coupled substitutions (e.g., ⁮ + Ti = Na + Al) and local mineral equilibria (e.g., tourmaline–chlorite). Analyses of the pale discordant reaction rims show consistent depletion of Fe, Ca, and Ti, presumably by fluid–solid reactions during post-ore metamorphism.Chlorites also show an extensive range in composition, from ripidolite nearly to end-member daphnite, with Fe/(Fe + Mg) ratios of 0.43–0.98 and Si cation values of 5.00–5.39. Chlorites from the fringes of the footwall stringer zone have narrow compositional ranges, whereas chlorites near footwall rhyolite sills in the core of the stringer zone display major variations in Fe/(Fe + Mg) ratios, including one sample with a range of 0.68–0.95. The former group of chlorites has Fe/(Fe + Mg) ratios that correlate well with those of coexisting tourmalines (exclusive of late reaction rims). Data for the latter group, in contrast, fall off equilibrium K D curves, indicating that the tourmalines and chlorites within these samples are not in chemical equilibrium. The chlorites are believed to have been altered (overprinted) by Fe-rich hydrothermal fluids apparently generated during intrusion of the rhyolite sills. The tourmalines, however, are unaffected and retain primary chemical signatures.Variations in mineral proportions and mineral chemistry within the deposit mainly depend on fluctuations in temperature, pH, water/rock ratios, and amounts of entrained seawater. The major proposed control is mixing between high-temperature, Fe-rich end-member hydrothermal fluids and cold, Mg-rich entrained seawater. Fe/(Fe + Mg) variations in footwall tourmalines (and equilibrium chlorites) are believed to largely reflect the progressive infiltration of Mg-rich seawater into the margins and top of the hydrothermal system. The more Fe-rich compositions of Kidd Creek tourmalines relative to those from sediment-hosted massive sulphide deposits (e.g., Sullivan, British Columbia) may be related to the preferential generation of end-member hydrothermal fluids in proximal volcanic environments like that at Kidd Creek.

Ontario↗

USGS1970

Morphology of certain viruses of Salmonid Fishes. I. in vitro studies of some viruses causing Hematopoietic Necrosis

An electron microscope study was performed on three virus isolates that caused hematopoietic necrosis in salmonid fishes: infectious hematopoietic necrosis (IHN), Oregon Sockeye Disease (OSD), and Sacramento River Chinook Salmon Disease (SRCD). All three isolates were examined by negative staining of fathead minnow (FHM) monolayer tissue culture concentrates and IHN virus was also examined in thin sections of FHM cells. Viruslike particles were observed in infected tissues, but similar structures were not found in uninfected cultures. All three isolates were bullet-shaped, but oval and truncated forms were also observed. Mean measurements of particles from IHN-virus-infected tissue were 158&ensp;×&ensp;90&ensp;mμ. They consisted of an outer coat 15&ensp;mμ thick, a core 60&ensp;mμ in diameter, subunits about 5&ensp;mμ, and an axial pore about 20&ensp;mμ in diameter. These particles also were seen budding from the cytoplasmic membrane. Similar particles from SRCD were 159&ensp;×&ensp;90&ensp;mμ and isolates from OSD were 181&ensp;×&ensp;91&ensp;mμ. The three isolates were morphologically indistinguishable from one another and the greater length of OSD was considered insignificant. IHN, SRCD, and OSD viruses were tentatively placed in the rhabdovirus group, but serological studies are needed to determine if they are antigenically identical or should be included as separate members. Biochemical and physical characteristics of these viruses and a comparison with other salmonid viruses is also discussed.

Journal of the Fisheries Research Board of Canada↗

USGS1970

Morphology of certain viruses of Salmonid fishes. II. In vivo studies of infectious Hematopoietic Necrosis Virus

Juvenile sockeye salmon ( Oncorhynchus nerka ) were injected with the infectious hematopoietic necrosis (IHN) virus, and tissue samples from the anterior kidney, spleen, liver, intestine, and pyloric caeca of moribund fish were prepared for electron microscopy. Bullet-shaped virus particles measuring 158&ensp;×&ensp;90&ensp;mμ were observed in the hematopoietic tissues of the anterior kidney and spleen. Virus particles were also observed in the outer connective tissues of the pancreas or pyloric caeca, or both. No virus was found in the intestine or liver. The healthy appearance of erythrocytes, reticular cells, and endothelial cells in necrotic areas of the spleen and anterior kidney, and the absence of lymphocytes in these areas, suggested that lymphocytes might be one source of the virus.

Journal of the Fisheries Research Board of Canada↗

USGS1976

Glomerular mesangial fibrosis in hatchery-reared rainbow trout (Salmo gairdneri)

Light and electron microscopic studies were performed on tissues of hatchery-reared rainbow trout ( Salmo gairdneri ) having a disease of currently unknown etiology with external symptoms of severe edema which causes increased mortality rate. Comparison with unaffected trout tissues revealed loss of cellularity in glomerular tufts with a replacement of mesangial cells by connective tissue. Ultrastructural studies showed the material to be collagen and established the diagnosis of glomerular mesangial fibrosis. The glomerular lesion was associated with alterations in lining epithelium of proximal tubules and extensive debris within tubule lumens. The findings are compared to glomerular lesions in mammalian and amphibian kidney.

Journal of the Fisheries Research Board of Canada↗

USGS1980

Viral erythrocytic necrosis: Some physiological consequences of infection in chum salmon ( Oncorhynchus keta )

Erythroid cells in chum salmon ( Oncorhynchus keta ) susceptible to infection with erythrocytic necrosis virus (ENV) were examined by light and electron microscopy. Cells of stages II, III, IV, V, and VI contained complete eyrthrocytic necrosis virions in the cytoplasm. Viruses closely resembling ENV were also detected in the nuclei of some erythroblasts. Some secondary consequences of ENV infection were a threefold greater mortality rate from vibriosis, a significantly decreased tolerance to oxygen depletion, and a decreased ability to regulate serum sodium and potassium in saltwater.

Canadian Journal of Fisheries and Aquatic Sciences↗

USGS1998

Methyl mercury dynamics in littoral sediments of a temperate seepage lake

The sites and rates of methyl mercury (MeHg) production and transport in littoral zone sediments were investigated at Pallette Lake in northern Wisconsin. In littoral areas where groundwater inflow occurs, sulfate supply from groundwater creates profiles of electron acceptors (sulfate) and donors (methane, sulfide) that are reversed from those found in sediments whose sulfate supply is delivered from overlying water. The highest MeHg concentrations in porewaters and the maximal advective MeHg flux rates (4.5-61.7 ng ·m -2 ·day -1 ) were observed in the spring, while highest bulk phase concentrations occur later in the summer. These estimated MeHg fluxes are greater than the mean areal production rates estimated previously for the water column and are similar to the atmospheric flux. Gross MeHg production was measured using the addition of 203 Hg as a tracer to sediments. The depth at which maximal 203 Hg methylation occurred coincided with the observed maximums in solid-phase and porewater MeHg concentrations. Because input, advection, and accumulation of MeHg in these sediments were measured directly, an independent estimate of MeHg production could be made and compared with 203 Hg-derived rates. This comparison suggests that that the 203 Hg tracer method provides reasonable estimates of gross methylation rates and that a substantial fraction of solid-phase Hg is available for methylation

Canadian Journal of Fisheries and Aquatic Sciences↗

USGS2000

Sperm-cell ultrastructure of North American sturgeons The lake sturgeon (Acipenser fulvescens Rafinesque, 1817)

Lake sturgeon ( Acipenser fulvescens ) sperm cell fine structure was examined using transmission electron microscopy. The cell possesses a distinct acrosome, a defined head region, a midpiece, and a single flagellum. Sperm cells of this species share a general radial symmetry, an elongate shape, a distinct acrosome, and the presence of endonuclear canals with those of other sturgeons. The mean length of the lake sturgeon sperm cell body (acrosome + nucleus + midpiece) is approximately 7.13 µm and the length of the flagellum is about 50 µm, resulting in a total cell length of about 57 µm. The lake sturgeon sperm cell is much longer and slightly wider than that of the Atlantic sturgeon. The sperm-cell nuclei of lake, shortnose, white, and stellate sturgeons are elongate trapezoids in shape, with the anterior (acrosome) end narrowest but, in the Atlantic sturgeon, the anterior portion of the trapezoid is wider than the posterior. Although slightly smaller in total length and width, the lake sturgeon sperm cell is most similar to the shortnose sperm cell in ultrastructure, overall size, and shape; it also shares similarity of shape with the stellate and white sturgeon sperm cells. The cell nuclei of these four sturgeons have three endonuclear canals. The acrosome of the lake sturgeon sperm cell has longer posterolateral projections than that of the Atlantic or shortnose sturgeon sperm cell. A structural connection, the fibrous body, is present in the lake sturgeon sperm cell between the nuclear fossa and the proximal centriole, as in the Atlantic and shortnose sturgeon sperm cells. Our results suggest a more recent evolutionary linkage between the lake and shortnose sturgeons than with the Atlantic sturgeon. This work presents the first ultrastructural description of the lake sturgeon sperm cell.

Canadian Journal of Zoology↗

USGS2022

Spectral reflectance properties (0.4-2.5 μm) of secondary Fe-oxide, Fe-hydroxide, and Fe-sulphate-hydrate minerals associated with sulphide-bearing mine wastes

Diffuse reflectance spectra of 15 mineral species commonly associated with sulphide-bearing mine wastes show diagnostic absorption bands related to electronic processes involving ferric and/or ferrous iron, and to vibrational processes involving water and hydroxyl. Many of these absorption bands are relatively broad and overlapping; however, spectral analysis methods, including continuum removal and derivative analysis, permit most of the minerals to be distinguished. Key spectral differences between the minerals are illustrated in a series of plots showing major absorption band centres and other spectral feature positions. Because secondary iron minerals are sensitive indicators of pH, Eh, relative humidity, and other environmental conditions, spectral mapping of mineral distributions promises to have important application to mine waste remediation studies.

Geochemistry: Exploration, Environment, Analysis↗

USGS2025

Evaluating sediment transport and metal sorption in the San Juan River watershed

The physical and chemical characteristics of sediment influence the transport of metals in rivers. The San Juan River and its tributaries are located in the Four Corners Region in the southwestern United States and the watershed contains a wide variety of potential metal sources. Comparisons of past and present sediment data provide insight into the effects of seasonality and storm events on the transport of sediment within a watershed. Comparisons suggest finer (<0.63 µm) sediment particles increase at a greater rate during intense storm events than coarser sediment particles. These fine, clay-sized sediments have a greater potential for metal sorption. Statistical analyses compared upper and lower portions of the San Juan River. Results show that total elemental concentration decreases in sediments (1785.15 μ g l −1 ) and that concentrations increase in the aqueous phase (2063.08 μ g l −1 ) downstream in the San Juan River. Analyses using geochemical and scanning electron microscopy with energy dispersive spectroscopy suggest that sediment clay particles are the most likely constituent to transport metals in the San Juan River. Metal transport is further aided by metal oxide coatings that develop on the surfaces of larger particles. Increases in aggregation of fine-grained particles in the downstream portions of the San Juan River are also likely to bind elements within sediments, which can act as both a source and sink for metals in the lower watershed. CEC , geochemistry , PSD

Arizona, Colorado, New Mexico, Utah↗

USGS2002

Seismicity, gas emission and deformation from 18 July to 25 September 1995 during the initial phreatic phase of the eruption of Soufrière Hills Volcano, Montserrat

On 18 July 1995, after more than three years of irregularly increasing seismicity, phreatic explosions opened a new vent on Soufrière Hills Volcano, about 4 km east of the capital city of Plymouth, Montserrat. By early August 1995, the volcano was monitored by a nine-station seismic network, three telemetered electronic tiltmeters, and daily correlation spectroscopy (COSPEC) flights to measure SO 2 emission rates and to observe vent areas. Seismicity and SO 2 emission rates implicated magma intrusion as the cause of the seismic unrest. Strong evidence of magma ascent to shallow levels, however, did not appear until late September 1995, when increasing numbers of hybrid events heralded the formation of a small dome and spine. We infer from the data that intrusion of a small volume of magma occurred in July, but stalled on ascent. Degassing of the stalled magma formed a carapace that thickened with time. We suggest that either volatile build-up beneath the degassed carapace, or aseismic intrusion of fresh material, finally forced the stalled magma to the surface in late September 1995. A similar cycle of activity appears to have occurred during the second phreatic phase between late September and mid-November 1995.

Soufrière Hills Volcano↗

USGS2003

Distinguishing palagonitized from pedogenically-altered basaltic Hawaiian tephra: Mineralogical and geochemical criteria

Palagonitization is a common, but imperfectly defined process that greatly modifies the physical and chemical properties of glassy basaltic tephra deposited in subaquatic/subglacial environments on Earth and perhaps Mars. It also results in textures and mineralogies that are distinct from other forms of (mainly pedogenic) low temperature alteration. Specifically, the process of palagonitization (1) initially results in the formation of 'palaginitized glass', a quasi- or nano-crystalline, rind-like material that contains smectite, as well as lesser amounts of other clays (e.g. serpentine), and (2) eventually results in consolidation of tephra, mediated through the accretion of palagonitized glass and later- formed authigenic cements. Conversely, pedogenic weathering of glassy basaltic tephra is characterized by disaggregation of tephra, and formation of a wide range of pedogenic products, including layer silicates (although not primarily smectite), short-range-order aluminosilicates and oxyhydroxides, whose composition reflects the intensity of the weathering environment. These mineralogical and textural properties can be readily recognized through a variety of techniques including electron microscopy/microprobe analysis, reflectance spectroscopy, X-ray diffraction and soil chemistry. Analyses of samples collected from the summit regions of Kilauea and Mauna Kea volcanoes on the island of Hawaii are presented here in order to illustrate differences between palagonitization and pedogenic weathering of glassy basaltic tephra. In the young Hawaiian tephras studied, palagonitization has occurred in response to hydrothermal activity shortly after deposition. Although some, non-hydrothermally affected tephras may eventually become palagonitized, those that have been strongly desilicated by intense pedogenic weathering will probably never become palagonitized.

Geological Society Special Publication↗

USGS2022

Potassium-Argon ages for minerals from the Ross of Mull, Argyllshire, Scotland

Sixteen K-Ar ages for samples of biotite and amphibole from the Ross of Mull and analytical data for the standards Bern 4M and W1 are presented. Ages determined for biotite and amphibole samples from the Caledonian pluton average 423 ± 4 m.y. and 416 ± 4 m.y. respectively. Field observations combined with gravity data indicate that this intrusion was guided by the Moine thrust plane. These ages therefore provide a minimum age for the Moine thrust and their concordance is interpreted in relation to the retentivity of the dated amphiboles to 40 Ar inferred from electron microprobe analyses of their composition. A biotite sample from a minette dyke cutting the pluton yielded an age of 406 ± 10 m.y., whereas two samples of amphibole from a fourchite dyke in the Moine country rock yielded early Permian ages of 276 ± 7 m.y. and 274 ± 8 m.y.

Argyllshire↗

USGS2017

The application of microtextural and heavy mineral analysis to discriminate between storm and tsunami deposits

Recent work has applied microtextural and heavy mineral analyses to sandy storm and tsunami deposits from Portugal, Scotland, Indonesia and the USA. We looked at the interpretation of microtextural imagery (scanning electron microscopy) of quartz grains and heavy mineral compositions. We consider inundation events of different chronologies and sources (the AD 1755 Lisbon and 2004 Indian Ocean tsunamis, the Great Storm of 11 January 2005 in Scotland, and Hurricane Sandy in 2012) that affected contrasting coastal and hinterland settings with different regional oceanographic conditions. Storm and tsunami deposits were examined along with potential source sediments (alluvial, beach, dune and nearshore sediments) to determine provenance. Results suggest that tsunami deposits typically exhibit a significant spatial variation in grain sizes, microtextures and heavy minerals. Storm deposits show less variability, especially in vertical profiles. Tsunami and storm quartz grains had more percussion marks and fresh surfaces compared to potential source material. Moreover, in the studied cases, tsunami samples had fewer fresh surfaces than storm deposits. Heavy mineral assemblages are typically site-specific. The concentration of heavy minerals decreases upwards in tsunamigenic units, whereas storm sediments show cyclic concentrations of heavy minerals, reflected in the laminations observed macroscopically in the deposits.

Geological Society, London, Special Publications↗

USGS2010

Archiving strategy for USGS EROS center and our future direction

The U. S. Geological Survey's Earth Resources Observation and Science Center has the responsibility to acquire, manage, and preserve our Nation's land observations. These records are obtained primarily from airplanes and satellites dating back to the 1930s. The ability to compare landscapes from the past with current information enables change analysis at local and global scales. With new observations added daily, the records management challenges are daunting, involving petabytes of electronic data and tens of thousands of rolls of analog film. This paper focuses upon the appraisal and preservation functions employed to ensure that these records are available for current and future generations.

Conference Paper↗

USGS2006

Arsenic and selenium in microbial metabolism

Arsenic and selenium are readily metabolized by prokaryotes, participating in a full range of metabolic functions including assimilation, methylation, detoxification, and anaerobic respiration. Arsenic speciation and mobility is affected by microbes through oxidation/reduction reactions as part of resistance and respiratory processes. A robust arsenic cycle has been demonstrated in diverse environments. Respiratory arsenate reductases, arsenic methyltransferases, and new components in arsenic resistance have been recently described. The requirement for selenium stems primarily from its incorporation into selenocysteine and its function in selenoenzymes. Selenium oxyanions can serve as an electron acceptor in anaerobic respiration, forming distinct nanoparticles of elemental selenium that may be enriched in (76)Se. The biogenesis of selenoproteins has been elucidated, and selenium methyltransferases and a respiratory selenate reductase have also been described. This review highlights recent advances in ecology, biochemistry, and molecular biology and provides a prelude to the impact of genomics studies.

Annual Review of Microbiology↗

USGS1995

Evidence from tooth surface morphology for a posterior maxillary origin of the proteroglyph fang

Although the front-fanged venom delivery system of the Elapidae is believed to be derived from an aglyphous or opisthoglyphous colubroid ancestor, opinion is divided as to the end of the maxilla on which the proteroglyph fang originated. This study was undertaken to determine whether the evolutionary precursor of the proteroglyph fang was (a) a grooved posterior fang which migrated anteriorly, or (b) an enlarged anterior tooth which secondarily developed a groove for the conduction of venom. The surface morphology of the maxillary teeth of colubrid genera was examined using scanning electron microscopy. Ridges present on the lingual and labial surfaces of anterior maxillary teeth and on the anterior and posterior surfaces of posterior maxillary teeth were identified as morphological markers of potential value in distinguishing the anterior and posterior maxillary teeth of colubrid snakes, and in determining the origin of the proteroglyph fang. Patterns of ridges on the surfaces of elapid fangs examined were found to be consistent with the hypothesis that the evolutionary precursor of the proteroglyph fang was an opisthoglyph fang which migrated anteriorly.

Amphibia-Reptilia↗

USGS2022

Demonstration of a novel quantitative microscopy technique for automated characterization of in situ particulate matter in coal miners with progressive massive fibrosis

Rationale: Increasing exposure to respirable crystalline silica (RCS) linked to changes in mining production processes has been implicated in the resurgence of severe lung disease in U.S. coal miners. Lung mineralogy can provide insight into particle pathogenesis. However, standard approaches to characterizing in situ particulate matter (PM) by pulmonary pathologists have poor inter-rater comparability, and consensus agreement is time consuming. Scanning electron microscopy/energy-dispersive spectroscopy (SEM/EDX) is technically complex and labor intensive. We developed a method for quantitative in situ PM characterization using conventional polarized light microscopy (PLM) and explored PM features in lung tissue of coal miners with progressive massive fibrosis (PMF). Methods: With institutional review board approval, PLM images were obtained from 30 miners with PMF, classified by pathologists consensus based on PM profusion; 10 from each profusion group (mild/moderate/severe) were selected. Automated PM counting and characterization (including dimensions and grayscale intensity of PM > 0.3 m diameter) was performed on image samples using PLM with modified cell-counting software (BZ-X800 light microscope, Keyence Corporation, Osaka, Japan) (Figure 1). Quantitative PM density loge(PM count)/mm3 tissue was calculated for each sample and compared to pathologist PM profusion groups. PMF lesion type using consensus pathologist classification (13 coal-type, 9 mixed-type, and 8 silicotic-type) was compared to automated PM birefringence level (% particles with mean grayscale intensity <65, range 0-255). RCS particles are expected to be weakly birefringent (lower intensity) relative to other common minerals (e.g., silicates) contained in coal mine dust. PM features were analyzed in R 4.0.3 using one-way ANOVA for between-group comparisons. Results: Measured PM log-density increased significantly with higher qualitative profusion group (mild=10.480.98/mm3, moderate=11.460.81/mm3, severe=12.520.86/mm3, p<0.0001). Prevalence of weakly birefringent particles was significantly higher among silicotic-type PMF samples (31.57.9%) compared to either coal-type (21.510.1%, p=0.022) or mixed-type lesions (21.510.5%, p=0.025). Conclusion: This pilot study demonstrates the feasibility of a novel quantitative microscopy technique for counting and characterizing in situ lung PM in coal miners with PMF. Quantitative PM burden was comparable to pulmonary pathologists consensus profusion classification, but this method was substantially less time consuming and labor intensive and provided additional information about relevant PM features. The higher prevalence of weakly birefringent particles seen in silicotic-type PMF lesions may help inform mineralogic pathogenesis of RCS. Future efforts will expand the number of PMF cases analyzed, further validate our mineralogic findings using data from SEM/EDX and lung tissue digestate methods, and compare findings in historical versus contemporary coal miners with PMF.

Conference Paper↗

USGS2013

Three new Psammothidium species from lakes of Olympic and Cascade Mountains in Washington State, USA

Populations of several Psammothidium species were found in core sediments from nine remote, high elevation, ultraoligotrophic and oligotrophic, Olympic and Cascade Mountain lakes. Three of these species, P. lacustre, P. alpinum , and P. nivale , are described here as new. The morphology of the silica frustules of these species was documented using light and scanning electron microscopy. We discuss the similarities and differences with previously described Psammothidium species.

Washington↗