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The determination of the elastic constants for a solid material may be conveniently accomplished by measuring resonances corresponding to the elastic normal modes of a sample. Isotropic materials should be particularly straightforward, since they involve only two independent elastic constants, the shear modulus and the longitudinal modulus. In practice one typically measures the shear modulus and Young's modulus, but for some problematic materials these are not truly independent. Probing the microscopic processes of solid mechanical behavior requires knowledge of independent moduli. In this paper, a resonance method for directly measuring the independent moduli for problematic materials is described.

A powerful method for measuring the elastic properties of solid materials is resonance spectroscopy. An advantage of this method is that the experimental measurement is relatively easy, and the difficult analysis is accomplished with a computer program. A particular computer algorithm has become standard because it is fast and may be applied to a wide range of shapes of solid samples. However, the algorithm does not work well for solids with layers of different materials. Fortunately, a relatively easy modification of the customary computer algorithm enables it to work for layered solids.

The Kope Formation is a rock unit that extends over southwest Ohio and adjacent areas of Kentucky and Indiana, USA. It is characterized by meter-scale cycles of mudstones and limestones where thick mudstone is sandwiched between thin limestone layers. Kope Formation mudstones are less durable than the mudstones in the area. They cause abundant slope failures in areas of their outcrops. This study evaluates chemical, mineralogical and textural properties of Kope mudstones to determine why it is less durable. The Two-cycle slake durability index (ID 2 ) was measured on thirty mudstones belonging to three consecutive cycles of the Kope Formation. Chemical composition and mineralogy of Kope mudstones do not show significant relationship with the ID 2 . Instead, a relationship to fabric was found. Kope mudstones with two main fabric types were observed in the field; laminated mudstones and non-laminated mudstones. Detailed micro-fabric analysis on Kope mudstones was done using the scanning electron microscope. Laminated mudstones with turbostratic fabric showed higher ID 2 and lower moisture content than the non-laminated mudstones with matrix fabric. The difference in the ID 2 of laminated mudstones and non-laminated mudstones is statistically significant. Both mudstone types exist in many cycles of the Kope Formation. Thus, core samples should be selected from both types for preliminary tests in geotechnical practice, to obtain more accurate estimations of the geotechnical properties of the Kope mudstones. The results and data interpretations of this study can be correlated with the mudstones and shale in different areas of the world. Specifically, a great attention should be paid to the macro and micro textural properties of any rock type regardless of their classification.

Most studies on roadside soil pollution have been performed in areas where petrol is the main fuel. Very little work has been conducted in regions where diesel predominates. We collected soil samples from four sites that span a precipitation gradient along the Manali-Leh Highway in northwestern Himalaya, India. This road traverses rough terrain and most of the vehicles that travel along it are diesel-driven. At each site, we collected samples at incremental distances from the highway (0, 2, 5, 10, 20, and 150 m), and at each distance we collected samples from three depths (3, 9, and 15 cm). We assessed the concentrations of 10 heavy metals (Al, Fe, Cr, Cu, Pb, Ni, Co, Zn, V, and Ba), total sulphur, and total organic carbon (TOC) at each distance, and we measured the concentration of 16 polycyclic aromatic hydrocarbons (PAHs) at 2 m from the highway. Overall, we found that metal concentrations are low and there is no relationship between concentrations and distance from the highway, or depth within the soil profile. Sulphur concentrations, on the other hand, are high in roadside soils and there is a negative relationship between concentration and distance from the highway. PAH concentrations are low, but the proportion of different ringed species suggests that their source is anthropogenic. Correlations between TOC and the various pollutants further suggest that diesel vehicles and potentially biomass combustion are starting to affect the roadside environment in remote northwestern India. We suggest that pollutant concentrations be regularly monitored.

International audience; The large manganese (Mn) deposit at Obrochishte (NE Bulgaria) is part of a cluster of similar Early Oligocene deposits located around present-day Black Sea. They collectively constitute the Earth's second largest endowment of Mn, after the Kalahari Manganese Field in Africa. We have employed a battery of isotopic techniques (C, O, Fe, Sr, Nd, Pb) to help understand the genesis of this deposit. Carbon isotope data indicates that some sections of the Mn-ore layer have diagenetic MnCO3 mineralization, formed by reaction of Mn oxides with organic carbon (C-org, whereas other sections have MnCO3 precipitated directly from the seawater column. Oxygen isotopes show that the high-grade Mn mineralization had seawater as the fluid source, whereas some lower-grade sections had a mix of ground water and seawater as fluid sources. Sr and Nd isotope values of ore leachates also indicate that the Mn deposition occurred in normal Early Oligocene seawater. Nd and Pb isotope values suggest that the clastic host sediments were sourced from continental bedrock rather than younger arc volcanic rocks to the west. Iron isotope composition of the Mn ore implies deposition in a redox-stratified basin, similar to the modern Black Sea, with much of the Fe sequestered in deep, anoxic-euxinic water as sulfides. Similar to the modern Black Sea, most of the detrital Fe was transferred from shallow oxic sediments into deep, anoxic-euxinic water by an "iron shuttle" and remobilized Mn sequestered in the upper suboxic water layer. However, during the Oligocene, the "iron shuttle" operated intermittently due to the chemocline falling mostly below the shelf break, thereby limiting the efficiency of the shuttle mechanism. We propose a model for the Lower Oligocene strata in which intense weathering during the Eocene weathering phase produced a thick lateritic crust on the southern European continent. The drastic sea-level drop at the end of the Eocene initiated downcutting of streams through this weathered material, transferring Fe- and Mn-oxides to the redox-stratified Western Black Sea. Here, these oxides were partly or entirely dissolved in the suboxic (Mn-oxides partly, Fe-oxyhydroxides entirely dissolved) and anoxic-euxinic (Mn-oxides entirely dissolved, dissolved Fe2+ re-precipitated) water layers. Eventually, Fe was re-precipitated as sulfide in the deep anoxic-euxinic water, while Mn accumulated in the suboxic water layer. Transgression in the Early Oligocene brought this Mn-rich water onto the shallow shelf where it precipitated as Mn-oxide, then converted to Mn-carbonates during early diagenesis. Some Mn was also contributed by submarine groundwater discharge. Further transgression brought lower-oxygen water onto the shelf and Mn-carbonate precipitated directly from the water column. The findings from this work provide insights about the unique Oligocene geochemical event in the region that lead to the formation of the 2nd largest cluster of Mn deposits in the world.

The Trent-Crede Medal is presented to an individual, irrespective of nationality, age, or society affiliation, who has made an outstanding contribution to the science of mechanical vibration and shock, as evidenced by publication of research results in professional journals or by other accomplishments in the field.

This study provides a physicochemical assessment of manganese deposits on brass and lead components from two fully operational drinking water distributions systems. One of the systems was maintained with chlorine; the other, with secondary chloramine disinfection. Synchrotron-based in-situ micro X-ray adsorption near edge structure was used to assess the mineralogy. In-situ micro X-ray fluorescence mapping was used to demonstrate the spatial relationships between manganese and potentially toxic adsorbed metal ions. The Mn deposits ranged in thickness from 0.01 to 400 μm. They were composed primarily of Mn oxides/oxhydroxides, birnessite (Mn(3+) and Mn(4+)) and hollandite (Mn(2+) and Mn(4+)), and a Mn silicate, braunite (Mn(2+) and Mn(4+)), in varying proportions. Iron, chromium, and strontium, in addition to the alloying elements lead and copper, were co-located within manganese deposits. With the exception of iron, all are related to specific health issues and are of concern to the U.S. Environmental Protection Agency (U.S. EPA). The specific properties of Mn deposits, i.e., adsorption of metals ions, oxidation of metal ions and resuspension are discussed with respect to their influence on drinking water quality.

Divalent cationic strontium (Sr 2+ ) adsorption to and desorption from iron corrosion products were examined in two model drinking water distribution systems (DWDS). One system was maintained with chlorine-disinfected drinking water and the other with the same water with secondary chloramine disinfection. Flow conditions simulated primary transmission lines (constant flow) and residential mains (periods of stagnation). Accumulation of Sr 2+ to iron corrosion products in model DWDS was independent of disinfection type. Adsorption and desorption mechanisms are discussed. X-ray adsorption near edge structure (XANES) spectroscopy and linear combination fitting determined Sr 2+ was primarily associated with iron oxyhydroxide corrosion products. At the end of the desorption study, the amount of Sr 2+ remaining in iron corrosion products equilibrated to approximate levels observed at the end of the constant flow adsorption experiments. These results suggest that enhanced iron corrosion product loading of Sr 2+ during stagnation could be short lived under constant flow conditions. Differences between adsorption and desorption based on disinfection type (chlorine versus chlorine plus chloramine) cannot be used to control Sr 2+ desorption.

Results of multiple sulfur isotope analyses from five Archean paleosols show the widespread presence of mass-independently fractionated sulfur in the regolith developed on the pre-2.5 Ga Earth. Analysis of sulfur from a small set of diamictite samples gave similar results. All values of Δ 33 S are negative, indicating that the Archean surface environments preferentially retained atmospheric S from the SO 4 2 − pathway, which carried a negative Δ 33 S signal, whereas a portion of the S from the S 8 pathway, with a positive Δ 33 S, was transferred to the oceans. The soil SO 4 2 − was then converted to sulfide by bacterial sulfate reduction with terrestrial organic matter in the weathering horizon acting as a reductant. Some S from the S 8 pathway also included, which resulted in a net soil Δ 33 S anomaly from atmospheric S in the range − 0.3 to − 0.6‰, similar to values for pyrites from floodplain sediments. Excess S 8 -derived S was carried to the oceans, resulting in the negative/positive dichotomy between terrestrial and marine systems. Pyrite that formed in paleosols and pyrite grains that formed in flood-plain deposits, both carrying the terrestrial Δ 33 S signal, were then recycled into detrital pyrite grains now found in sandstones and conglomerates deposited before the rise of atmospheric oxygen. Therefore the Earth's early regolith constituted a reservoir of S with negative Δ 33 S values that could be important for balancing the predominantly positive Δ 33 S signature found in marine sediments.

The United States Environmental Protection Agency (US EPA) will require some U.S. drinking water distribution systems (DWDS) to monitor nonradioactive strontium (Sr(2+)) in drinking water in 2013. Iron corrosion products from four DWDS were examined to assess the potential for Sr(2+) binding and release. Average Sr(2+) concentrations in the outermost layer of the corrosion products ranged from 3 to 54 mg kg(-1) and the Sr(2+) drinking water concentrations were all ≤0.3 mg L(-1). Micro-X-ray adsorption near edge structure spectroscopy and linear combination fitting determined that Sr(2+) was principally associated with CaCO3. Sr(2+) was also detected as a surface complex associated with α-FeOOH. Iron particulates deposited on a filter inside a home had an average Sr(2+) concentration of 40.3 mg kg(-1) and the associated drinking water at a tap was 210 μg L(-1). The data suggest that elevated Sr(2+) concentrations may be associated with iron corrosion products that, if disturbed, could increase Sr(2+) concentrations above the 0.3 μg L(-1) US EPA reporting threshold. Disassociation of very small particulates could result in drinking water Sr(2+) concentrations that exceed the US EPA health reference limit (4.20 mg kg(-1) body weight).

© 2015 American Society of Civil Engineers. A common phenomenon observed in natural and constructed wetlands is short-circuiting of flow and formation of stagnant zones that are only indirectly connected with the incoming water. Biogeochemistry of passive areas is potentially much different than that of active zones. In the research reported in this paper, the spatial resolution of a previously developed wetland nutrient cycling model was improved in order to capture the spatial variability of concentrations and reaction rates regarding nitrogen and carbon cycles throughout active and passive zones of wetlands. The upgraded model allows for several compartments in the horizontal domain, with all neighboring compartments connected through advective and dispersive/diffusive mass transport. The model was applied to data collected from a restored wetland in California that was characterized by the formation of a large stagnant zone at the southern end of the wetland due to close vicinity of the inlet and outlet structures in the northern end. Mass balance analysis revealed that over the course of the research period, about 23.4±3.9% of the incoming total nitrogen load was removed or retained by the wetland. It was observed that mass of all exchanges (physical and biogeochemical) regarding nitrogen cycling decreased along the activity gradient from active to passive zones. Model results also revealed that anaerobic processes become more significant along the activity gradient towards passive areas.

Two Permian/Triassic boundary sections in central Japan provide a rare window into environmental conditions within the Panthalassic Ocean, which encompassed more than half the Earth's surface at 252 Ma. Integration of petrographic, geochemical, and time series data provides new insights regarding the fluxes of major and trace components to the sediment as well as environmental conditions in both the deep and intermediate water masses at each study site. The Ubara section was located in a high-productivity peri-equatorial location, whereas the Gujo-Hachiman section was located in a moderate-productivity location at some distance from the paleoequator. An upward transition from gray organic-poor cherts to black siliceous mudstones at both sites occurred in conjunction with increased primary productivity, intensified euxinia within the oxygen-minimum zone (OMZ), and decimation of the radiolarian zooplankton community. Euxinia in the OMZ of the equatorial Panthalassic Ocean developed episodically for a ~ 200–250 kyr interval during the Late Permian, followed by an abrupt intensification and lateral expansion of the OMZ around the Permian–Triassic boundary. Throughout the study interval, bottom waters at both sites remained mostly suboxic, a finding that counters hypotheses of development of a “superanoxic” Permo-Triassic deep ocean as a consequence of stagnation of oceanic overturning circulation.

Almost all economic manganese ores are ultimately or directly derived from hydrothermal vents associated with intermediate volcanic rocks. This source is in contrast to deep-sea nodules, which likely have a larger component of sediment-derived manganese and whose volcanic sources are more mafic. Manganese deposits can be divided into sedimentary rock-hosted, volcanic rock-hosted and karst-hosted, in order of predominance. Two genetic types of sedimentary rock-hosted deposits can also be identified: those with Mn derived via upwelling from oxygen-minimum zones and those formed on the margins of euxinic basins. Most of the large tonnage deposits appear to form by the euxinic mechanism. Manganese ores, like those of Fe, show a strong concentration of deposits in the Paleoproterozoic and a lesser occurrence in the Neoproterozoic, but, unlike Fe, there is an additional strong peak in the Oligocene. Therefore, Mn is not controlled entirely by the level of oxygen in the Earth’s atmosphere. At each peak of Mn deposition, the associated ore deposits are concentrated in a few districts, suggesting a more local than global control on manganese metallogenesis. Age trends can, however, be discerned in some chemical properties of manganese deposits. Overall, there is a trend to progressive increases in chemical diversity from the Archean to the Recent, with a particularly steep increase in the Neoproterozoic-Early Cambrian, corresponding in time to the radiation of metazoans. Also beginning in the Cambrian is the development of upwelling-linked deposits. There is another sharp increase in chemical diversity at the Jurassic-Cretaceous boundary, which includes increased SiO 2 /Al 2 O 3 ratios and corresponds to the radiation of diatoms. There is a conspicuous gap in sedimentary rock-hosted Mn deposits between 1800 and 800 Ma that may correspond to a monotonous, low-oxygen ocean, but one without sulfidic deep water. Alternatively, Mn may have been precipitated entirely in the deep ocean, beneath a sulfidic oxygen minimum layer. The positive Eu anomalies, which in iron formations are equated to vent-sourced metals, are not seen in most Mn deposits, although they are found in Mn-rich iron formations. By contrast, Fe deposits interbedded with major Mn ores lack the usual Eu signal. Therefore, mechanisms of transport between hydrothermal vents and the sites of deposition differed for Fe and for Mn deposits in the Archean-Paleoproterozoic. The dominant pattern in the time trend of Mn deposition is increasing chemical diversity, which reflects an increasing compartmentalization of the Earth’s depositional environments. This compartmentalization was a response to, but also provided a spur to, the diversification of life forms.

The Gujo-Hachiman section in central Japan provides a rare window into environmental conditions within the Panthalassic Ocean, which encompassed more than half the Earth’s surface at 251 Ma. The section is characterized by a sharp transition from green-gray organicpoor cherts to black siliceous shales in the uppermost Permian. Normalization to the clay fraction demonstrates that apparent increases in the concentrations of organic matter and trace metals above this transition were due primarily to the loss of a diluent biogenic (radiolarian) silica fl ux and only secondarily to a small shift toward more reducing bottom waters. In the black shale, pyrite abundance increases by a factor of ~30× and is dominated by framboidal grains of probable syngenetic origin. These observations suggest that the expansion of lowoxygen conditions within the Panthalassic Ocean was focused within the oxygen-minimum zone rather than at the seafl oor. Such a pattern implies that (1) changes in nutrient fl uxes and primary productivity rates, rather than stagnation of oceanic circulation, were a key factor infl uencing oceanic redox conditions around the Permian-Triassic boundary, and (2) large regions of the Panthalassic Ocean underwent only limited redox changes, providing potential refugia for marine taxa that survived into the Triassic.

Articular cartilage degeneration in osteoarthritis has been linked to abnormal mechanical stresses that are known to cause chondrocyte apoptosis and metabolic derangement in in vitro models. Evidence implicating oxidative damage as the immediate cause of these harmful effects suggests that the antioxidant defenses of chondrocytes might influence their tolerance for mechanical injury. Based on evidence that antioxidant defenses in many cell types are stimulated by moderate oxidant exposure, we hypothesized that oxidant preconditioning would reduce acute chondrocyte death and proteoglycan depletion in cartilage explants after exposure to abnormal mechanical stresses. Porcine cartilage explants were treated every 48 h with tert-butyl hydrogen peroxide (tBHP) at nonlethal concentrations (25, 100, 250, and 500 microM) for a varying number of times (one, two, or four) prior to a bout of unconfined axial compression (5 MPa, 1 Hz, 1800 cycles). When compared with untreated controls, tBHP had significant positive effects on post-compression viability, lactate production, and proteoglycan losses. Overall, the most effective regime was 100 microM tBHP applied four times. RNA analysis revealed significant effects of 100 microM tBHP on gene expression. Catalase, hypoxia-inducible factor-1alpha (HIF-1alpha), and glyceraldehyde 6-phosphate dehydrogenase (GAPDH) were significantly increased relative to untreated controls in explants treated four times with 100 microM tBHP, a regime that also resulted in a significant decrease in matrix metalloproteinase-3 (MMP-3) expression. These findings demonstrate that repeated exposure of cartilage to sublethal concentrations of peroxide can moderate the acute effects of mechanical stress, a conclusion supported by evidence of peroxide-induced changes in gene expression that could render chondrocytes more resistant to oxidative damage.

Kyanite Mining Corporation, located in Dillwyn, Virginia has been in operation for over 50 years and their local operation is the largest kyanite mine in the world. As part of the processing at this location, a magnetic separate is generated and a minimum estimation of 3.57 million tons of waste has accumulated. Currently no use for the magnetic separate has been identified. We investigated eight representative samples of the magnetic mine waste which varied in color from a dark tan to black, to determine if the waste could be recycled as an ore or could be used as an environmental media. Mineralogical investigations indicate the composition of the magnetic mine waste is dominated by magnetite, kyanite, lesser amounts of hematite and charcoal. Magnetite occurs as fine grained crystals and as inclusions in kyanite. Hematite occurs largely as botryoidal textures, as discrete grains, and as coatings on kyanite grains. Fe-oxide spheres ranging in diameter from approximately 5–100 µm are common and may compose up to 10% in some samples. Titanium dioxide was rarely observed as coatings on silicate mineral grains. Energy dispersive spectroscopy analysis on magnetite crystals indicates they have end-member compositions. Bulk property investigations indicate that grain size distributions of samples are primarily unimodal with 20–40% of material being between 0.600 and 0.250 mm. Hydraulic conductivity values of samples investigated vary between 0.0036 and 0.0077 cm/s and are broadly consistent with those expected of sands with similar grain size distributions. In addition to the magnetic waste stream a light blue, water soluble, amorphous Cu sulfate occurs as a coating on surfaces of boulders. The coating is composed of rounded interlocking particles 5–60 μm in diameter. This material is of some environmental concern for freshwater invertebrates, but can be managed using sorption media. Hyperspectral data were gathered of the magnetic separate, kyanite ore samples, and the light blue Cu sulfate. The signatures of the kyanite ore, the blue mineral coating, and a mixture of the two provide spectral fingerprints that an imaging spectrometer could exploit for rapid detection and subsequent environmental monitoring.

Physiochemical data were obtained for five iron tubercles from a single drinking water distribution system (DS). Texturally, there were two groups based on internal morphology: one with a core of soft brownish material marbled with veins of a hard black material, the other has a core consisting mostly of the hard, black material. Three iron mineral phases occur, α-FeOOH, γ-FeOOH, or Fe 3 O 4 . All three coexist in each tubercle but in widely varying proportions. These iron pipe tubercles exhibit a greater diversity within a single DS than previously thought. Because the chemical conditions for the formation of each material is different, water quality parameters may not be the main control of tubercle formation and growth.

The Permian–Triassic boundary at Nhi Tao, Cao Bang Province, Vietnam was sampled in a 7.5-m-thick outcrop section at high resolution (∼ 5 cm intervals) for chemostratigraphic and magnetic susceptibility analysis. The section consists entirely of slightly argillaceous limestone representing shallow-marine facies of the Jinxi Platform, one of several large carbonate platforms within the Nanpanjiang Basin, located on the southern margin of the South China Craton. Upper Permian strata (Beds 1–7) are mainly dark-gray, cherty fossiliferous wackestones and packstones containing a diverse open-marine fauna, whereas uppermost Permian and Lower Triassic strata (Beds 9 and higher) are medium-gray calcimicrobial framestones containing rare macrofossils. These facies are separated by a 12-cm-thick oolitic–pisolitic grainstone (Bed 8) that coincides with the disappearance of most Late Permian faunal elements as well as with the first appearance of various geochemical anomalies that continue into the Lower Triassic part of the section. This “Late Permian event horizon” is characterized by (1) an abrupt decline in total organic carbon to near-zero values, (2) the onset of a sustained decline in carbonate δ13C, and (3) the first of eight concentration peaks in pyrite sulfur. Significantly, each sulfide peak is associated with lower pyrite δ34S values as well as with the onset of a negative carbonate δ13C excursion (or the acceleration of an excursion already in progress). These chemostratigraphic relationships are consistent with multiple episodes of upwelling of sulfidic, 34S- and 13C-depleted deep-ocean waters onto the Jinxi Platform. The first upwelling event was the most intense and caused a drastic reduction in primary productivity and the demise of the Late Permian fauna; subsequent episodes were less intense but may have contributed to a delay in recovery of Early Triassic marine ecosystems. A ten-fold increase in magnetic susceptibility in Bed 9 may record the influx of fine detrital particles following destruction of terrestrial ecosystems and massive soil erosion. The terrestrial signal of the end-Permian catastrophe thus follows the marine signal with a 12-cm lag, which may reflect the time-of-transit of soil-derived particles across the Nanpanjiang Basin, suggesting that the marine and terrestrial crises in the Nhi Tao region occurred more-or-less synchronously. These observations suggest a model in which renewal of global-ocean overturn followed a prolonged interval of deep-ocean stagnation during the Late Permian, with upwelling intensity modulated by short-term (∼ 20 kyr) climate cyclicity.

The Southern California Continental Borderland (SCCB) is part of the broad San Andreas transform-fault plate boundary that consists of a series of fault-bounded, petroleum-generating basins. The SCCB has high heat flow and geothermal gradients produced by thinned continental crust and Neogene volcanism. Barite deposits in the SCCB occur along faults. Barite samples from two sea-cliff sites and four offshore sites in the SCCB were analyzed for mineralogy, chemical (54 elements) and isotopic (S, Sr) compositions, and petrography. Barite from Palos Verdes (PV) Peninsula sea-cliff outcrops is hosted by the Miocene Monterey Formation and underlying basalt; carbonate rocks from those outcrops were analyzed for C, O, and Sr isotopes and the basalt for S isotopes. Cold-seep barite from Monterey Bay, California was analyzed for comparison. SCCB offshore samples occur at water depths from about 500 to 1800 m. Those barites vary significantly in texture and occurrence, from friable, highly porous actively growing seafloor mounds to dense, brecciated, vein barite. This latter type of barite contrasts with cold-seep barite in being much more coarse grained, forms thick veins in places, and completely replaced rock clasts in breccia. The barite samples range from 94 to 99 wt% BaSO4, with low trace-element contents, except for high Sr, Zr, Br, U, and Hg concentrations compared to their crustal abundances. δ34S for SCCB offshore barites range from 21.6‰ to 67.4‰, and for PV barite from 62‰ to 70‰. Pyrite from PV sea-cliff basalt and sedimentary rocks that host the barites averages 7.8‰ and 2.2‰, respectively. Two offshore barite samples have δ34S values (21.6‰, 22.1‰) close to that of modern seawater sulfate, whereas all other samples are enriched to strongly enriched in 34S. 87Sr/86Sr ratios for the barites vary over a narrow range of 0.70830–0.70856 and are much lower than that of modern seawater and also lower than the middle Miocene seawater ratio, the time of deposition of the host rocks for the PV samples. This indicates that the mineralizing fluids were not unaltered seawater. We develop a model in which the barites precipitated both below the sediment–water interface and at the seafloor from low-temperature fluids that circulated along faults. The isotopic, chemical, and textural data indicate that the barites formed by several processes. Mesozoic and Cenozoic basement rocks (crystalline and overlying sedimentary rocks), Quaternary basin fill, turbidite fans, and seawater provided various elements for the barites in different environments. The fluids had a deep-seated source and were hydrothermal in the deeper parts of the system for all the barite types, including the seafloor cold-seep deposit, based on Sr isotopes and regional geothermal gradients. These deep-seated fluids mixed with other fluids as they ascended, including seawater at and near the seafloor. The high δ34S values may have resulted from extreme Rayleigh fractionation during bacterially mediated (semi)closed-system sulfate reduction, probably driven by the flux of methane- and hydrocarbon-bearing fluids through basement rocks and basin sediments. Early diagenetic dolomite and pyrite in the host Monterey Formation in the PV Headland also formed in a zone of sulfate reduction, but within sediment buried only centimeters to a few meters and with a predominantly seawater source for the sulfur. Dolomite occurring with vein barite in the PV Headland formed at temperatures in the range of 40–90 °C. The cold-seep barites have δ34S values near that of modern seawater, although still somewhat fractionated. The barites that precipitated below the sediment–water interface have higher δ34S values, suggesting that the fluids were relatively reduced with molar dissolved barium in excess of dissolved sulfate. Those samples were exposed at the seafloor by uplift along faults and are composed predominantly of massive, brecciated, and vein barite.

Subsurface flow constructed wetlands in the village of Akumal, Quintana Roo, Mexico were surveyed to determine the general status of the wetland systems and provide baseline information for long term monitoring and further study. Twenty subsurface flow wetlands were surveyed and common problems observed in the systems were overloading, poor plant cover, odor, and no secondary containment. Bulk mineral composition of aggregate from two subsurface flow constructed wetlands was determined to consist solely of calcite using bulk powder X-ray diffraction. Some soil structure is developed in the aggregate and aggregate levels in wetlands drop at an estimated rate between 3 and 10 cm/year for overloaded wetlands owing to dissolution. Mineral composition from fresh aggregate samples commonly is a mixture of calcite and aragonite. Trace amounts of Pb, Zn, Co, and Cr were observed in fresh aggregate. Coefficients of permeability (k) varied from 0.006 to 0.027 cm/s with an average values being 0.016 cm/s. Grain size analysis of fresh aggregate samples indicates there are unimodal and multimodal size distributions in the samples with modes in the coarse and fine sand being common. Investigations of other geologic media from the Reforma region indicate that a dolomite with minor amounts of Fe-oxide and palygorskite is abundant and may be a better aggregate source that the current materials used. A Ca-montmorillonite bed was identified in the Reforma region as well and this unit is suitable to serve as a clay liner to prevent leaks for new and existing wetland systems. These newly discovered geologic resources should aid in the improvement of subsurface flow constructed wetlands in the region. Although problems do exist in these wetlands with respect to design, these systems represent a successful implementation of constructed wetlands at a community level in developing regions.

Provenience studies provide insights concerning trade in various goods, such as millstones. This is the first attempt to source millstones from Albania. Thirty-one vesicular volcanic millstones, predominately from the Greek and Roman periods, were obtained from two sites, 21 from Apollonia and ten from Butrint. The purpose of this study was to determine the provenience of these millstones using textural, mineralogical, and chemical data. The compositions of the samples were compared to those of vesicular volcanic sources in the central and eastern Mediterranean. Eight viable sources were initially identified based on major element chemistry; these were ultimately reduced to three based on trace element provenience studies. All of the Apollonia and five of the Butrint millstones have chemical signatures similar to those of Sicilian sources (the Iblean Fields and Mt. Etna). The remaining five Butrint millstones are chemically similar to stones from quarries other on the Cycladic island of Melos othe...

Iron-sulfur geochemistry is important in many natural and engineered environments, including drinking water systems. In the anaerobic environment beneath scales of corroding iron drinking water distribution system pipes, sulfate-reducing bacteria (SRB) produce sulfide from naturally occurring sulfate in the bulk water. This sulfide subsequently can affect iron geochemistry of the scale and the protective qualities of the scale. The authors studied the effect of bacterial sulfate reduction on the nature of iron corrosion scales collected from two drinking water distribution systems-one using surface water and the other groundwater but both with relatively high sulfate concentrations. Reduced sulfur proved to be a significant component of all iron scales studied, reaching up to 22% (wt%) in the scale from the groundwater system and 2% in the surface water system. X-ray diffraction showed the presence of elemental sulfur (S°) and marcasite (FeS 2 ). Sulfur extractions showed major S° and FeS 2 in all scales but only minor amounts of iron(ll) sulfide (FeS) and sulfate ion (SO 4 2- ). Sulfur isotope measurements showed δ 34 S in the scales to be 20-40 permil (parts perthousand) lighter than in the source SO 4 2- , confirming the important role of SRB in forming the reduced sulfur. Other important iron minerals found were goethite (α-FeOOH) and lepidocrocite (γ-FeOOH). Magnetite (Fe 3 O 4 ), which is believed to be an important mineral in protecting iron pipes from extensive corrosion and iron release, was present in iron scales collected from the surface water system but not in those from the groundwater system.

Geochemical and petrographic data from the Konkola North deposit of the Zambian Copperbelt permits construction of a basement topography-driven fluid mixing model for mineralization. In this drill-core based study, the basement topography is inferred from the topography at the top of the footwall. Petrographic evidence suggests mineralization was a relatively late event and we have therefore assumed that present day basin floor topography is roughly similar to that at the time of mineralization. The basement topography appears to have controlled cross-strata migration of mineralizing fluids and to have induced fluid mixing that resulted in Cu mineralization, as well as in deposition of barite and other non-ore minerals. For the portion of the basin sampled, the footwall, and by inference the basement, shows considerable relief, with the deepest part of the basin on the southeastern end of the line of cores sampled. Following the line of cores to the Northwest, the footwall rises sharply to a local high and then drops into a local low before rising on the basin flank. Geochemical and petrographic data suggest that an oxidizing fluid enriched in Cu, Ba, K, and possibly Co migrated laterally within the footwall from the deep basin toward the basin flank. As the footwall and basement rose, the footwall fluid was forced upward into the Ore Shale horizons. Another fluid, likely a reducing one carrying H2S, traveled at a higher stratigraphic level and may have sunk into the Ore Shale horizons where the basin floor fell. Mixing between the two fluids in the vicinity of the lowest Ore Shale horizon resulted in sulphide mineralization. The fluid mixing also appears to be demarcated by barite immediately above or below the sulphide mineralization. The barite is generally below the base of the Ore Shale where falling basement topography permitted the upper fluid to sink and above where rising topography may have driven the footwall fluid upward to meet the upper fluid. Barite is rare above the basement highs, suggesting that the upper fluid may have been largely forced higher than the Ore Shale. Mineralization is strong above basement highs, but is dominated by more oxidized phases, not by sulphides common deeper in the basin. Both mineralization and barite are scarce between the local basement high and the high flank, suggesting that the footwall fluid, forced upward on the high, did not fully descend into the local low. In general, mineralization is stronger where basement topography is rising or high and weaker in the basement lows. It is likely that more than one episode of fluid flow has affected the basin and that the model presented is simplistic, but it may still provide useful insight into the possible relationship between basement topography and mineralization for this deposit and possibly others in the Copperbelt.

The black shale submember of core shales of Pennsylvanian Kansas-type cyclothems is highly enriched in redox-sensitive trace elements (TEs) relative to the overlying gray shale submember as well as to many other modern and ancient organic-rich deposits. Controls on trace-element behavior in the black shale can be inferred from trace-element enrichment factors (EFs, relative to gray shale) and the relationship of TEs to total organic carbon (TOC). Most TEs conformed to one of two patterns: (1) Mo, U, V, Zn, and Pb exhibited moderate EFs and strong covariation with TOC in samples having 10 wt.% TOC; and (2) Cu, Ni, Cr, and Co exhibited low EFs and moderate to strong covariation with TOC in all samples. These patterns are inferred to represent different responses to benthic redox conditions. The first pattern is characteristic of TEs of ‘‘strong euxinic affinity’’, i.e., those taken up in solid solution by Fe-sulfide or involved in other reactions catalyzed by free H2S, and resident mainly in authigenic phases, whereas the second pattern is characteristic of TEs of ‘‘weak euxinic affinity’’, i.e., those not strongly influenced by the presence of free H2S and resident mainly in the organic carbon or detrital fractions of the sediment. These inferences allowed development of a multiproxy technique for assessing redox facies in black shale samples: euxinic conditions were considered to have existed if at least two of four ‘‘redox-indicator’’ trace elements (Mo, U, V, Zn) showed euxinic levels of enrichment, and nonsulfidic anoxic conditions were inferred otherwise. The validity of the procedure is indicated by (1) agreement among all four ‘‘redox indicators’’ for a large majority of samples (69% of 185); (2) among samples yielding a mixed redox signal, a systematic sequence of TE enrichment (V !Zn !Mo !U); and (3) for TEs of ‘‘weak euxinic affinity’’, reduced variance among samples representing each redox facies. Sequential enrichment may be a response to differential redox thresholds for accumulation (e.g., V) or postdepositional remobilization of trace elements (e.g., U) and may provide a basis for finer assessment of redox conditions in low-oxygen paleoenvironments than permitted by simple classification schemes. The multiproxy procedure for redox-facies analysis developed in this study is likely to be more reliable than widely used single-proxy indicators based on trace elements (e.g., Mo, authigenic U, or V/(V+Ni)) or C–S–Fe systematics (e.g., S/TOC or DOP). D 2004 Elsevier B.V. All rights reserved.

The Botucatu Sandstone of the Parana basin of Brazil, a Jurassic eolianite, exhibits unusually deep, basinwide penetration of meteoric water. This flow of dilute groundwater has removed calcite cement for an average distance of about 140 km from the outcrop and down to a burial depth of about 250 m. Feldspar has been leached from the framework for about 30 km downdip, transforming what was deposited as a feldspathic sandstone into a diagenetic quartz arenite on outcrop. These two dissolution processes have generated appreciable secondary porosity by weathering reactions at sites far removed from contact with the atmosphere. Between 100 and 500 pore volumes of water have passed through the aquifer system to produce this leaching, making this an end-member case of extensive meteoric diagenesis of sandstone. Consideration of other basins with meteoric incursion suggests that basin-scale leaching is favored when uplift of one margin provides a steep gradient and there is a downdip escape route via faults or outcrop of the aquifer. Cratonic basins close to rifted-continental margins seem to provide the best chance of meeting these conditions.

Previous surgical crown lengthening studies have investigated positional changes of the free gingival margin but not the biological width. Histological studies utilizing animal models have shown that postoperative crestal resorption allowed reestablishment of the biological width. However, very little work has been done in humans. Therefore, the purpose of this study was to evaluate the positional changes of the periodontal tissues, particularly the biological width, following surgical crown lengthening in human subjects.Twenty-three (23) patients who needed surgical crown lengthening to gain retention necessary for prosthetic treatment and/or to access caries, tooth fracture, or previous prosthetic margins entered the study. The following parameters were obtained from line angles of treated teeth (teeth requiring surgical crown lengthening) and adjacent teeth with adjacent and non-adjacent sites: plaque and gingival indexes, free gingival margin, probing depth, attachment level, bone level, direct bone level, and biological width. During surgery, the bone level was reduced based on the future prosthetic margin and predetermined biological width; flaps were placed at the bony crest. Patients were examined at baseline and at 3 and 6 months postoperatively.Eighteen patients completed the study. Overall, the amount of bone resected was 1 to 5 mm. At 90% of treated sites,or = 3 mm of bone was removed. At 3 months, the apical displacement of the free gingival margin at non-adjacent, adjacent, and treated sites was 2.46 +/- 0.25 mm, 2.68 +/- 0.20 mm, and 3.07 +/- 0.16 mm, respectively. There was no significant change in the position of the free gingival margin from 3 to 6 months. The biological width at all sites was smaller at 3 and 6 months compared to baseline (P0.05) except for the treated sites, which were not significantly different from baseline at 6 months.During surgical crown lengthening, the bone level was lowered for placement of the prosthetic margin and reestablishment of the biological width. The biological width, at treated sites, was reestablished to its original vertical dimension by 6 months. In addition, a consistent 3 mm gain of coronal tooth structure was observed at the 3- and 6-month examinations.

Water chemical data from the Botucatu Sandstone aquifer in the Sao Paulo State part of the Parana Basin, Brazil, was evaluated using geochemical methods and two statistical analyses: cluster analysis and factor analysis. The results were used to develop a conceptual geochemical model, in which three geochemical regions were identified, and their chemical behavior was modeled. The characteristic chemicals, changing from the recharge area to the center of the basin, are: SiO2—(HCO3− and Ca2+)—(Na+, CO32−, and SO42−). The distribution of the chemicals is interpreted as controlled by different water–rock interaction processes in the different regions. In the recharge area, dissolution of alkali–feldspar minerals in the sandstone is the main reaction observed; in the mid-section of the basin, calcite dissolution results in high calcium and bicarbonate concentration; in the center of the basin, leakage from underlying layers becomes the governing factor.

The Pinar del Rio district of western Cuba contains several examples of stratiform Pb–Zn mineralization underlain by stockwork Cu mineralization. Similar deposits in Canada and Australia have been variously interpreted as products of seafloor hydrothermal systems or of much later hydrothermal activity associated with peak metamorphism during deep burial. The Cuban deposits are Jurassic in age and are less overprinted by later tectonic events than other deposits of this type, so they offer a useful opportunity to resolve these controversies. Vitrinite reflectance and illite and chlorite crystallinity were studied from cores and mine exposures from several localities in western Cuba. Dispersed vitrinite in host shales shows a sharp increase in thermal maturity over three distinct stages from host-rock to stratiform mineralization to stock-work mineralization. Based on vitrinite data from modern hydrothermal systems, the paleotemperatures are 175, 250, and 300 °C. The clay mineral results also show a step-wise increase in the crystallinity of illite and chlorite. In addition, there is an increasing dominance of chlorite over illite. When compared to burial diagenetic trends, chlorite crystallinity in the Cuban samples matches values expected from R r , whereas illite tends to yield lower-than-expected crystallinities. The clay results indicate that chlorite is an ore-stage mineral that equilibrated at the same temperature/pressure conditions as the vitrinite, whereas the illite is largely detrital and only incompletely recrystallized in the relatively short times available. These results are best explained as reflecting relatively low amounts of heating of shales in the country rock by burial diagenesis, progressing to intermediate heating by exhalative seafloor hydrothermal fluids in the stratiform portion of the deposits, and finally to still higher temperatures in the sub-seafloor stockwork portion.

Rainfall runoff from urban roadways oftencontains elevated amounts of heavy metals in both particulate anddissolved forms (Sansalone and Buchberger, 1997). Because metalsdo not degrade naturally, high concentrations of them in runoffcan result in accumulation in the roadside soil at levels thatare toxic to organisms in surrounding environments. This studyinvestigated the accumulation of metals in roadside soils at asite for which extensive runoff data were also available.For this study, 58 soil samples, collected from I-75 nearCincinnati, Ohio, were examined using X-ray fluorescence, C-Sanalyzer, inductively coupled plasma spectroscopy, atomicabsorption spectrometry and X-ray diffraction. The resultsdemonstrated that heavy metal contamination in the top 15 cm ofthe soil samples is very high compared to local backgroundlevels. The maximum measured amount for Pb is 1980 ppm (at 10–15 cm depth) and for Zn is 1430 ppm (at 0–1 cm depth). Metal content in the soil falls off rapidly with depth, and metalcontent decreases as organic C decreases. The correlation toorganic C is stronger than the correlation to depth. The resultsof sequential soil extraction, however, showed lower amounts ofPb and Zn associated with organic matter than was expected basedon the correlation of metals to % organic C in the whole soil.Measurement of organic C in the residues of the sequentialextraction steps revealed that much of the carbon was not removedand hence is of a more refractory nature than is usual inuncontaminated soils. Cluster analysis of the heavy metal datashowed that Pb, Zn and Cu are closely associated to one another,but that Ni and Cr do not show an association with each other orwith either organic C or depth. ICP spectroscopy of exchanged cations showed that only 4.5%of Pb, 8.3% of Zn, 6.9% of Cu and 3.7% of Cr in the soil isexchangeable. Combined with the small amounts of metals bound tosoluble organic matter, this result shows that it is unlikelythat these contaminants can be remobilized into water. At thissite, clays are not an important agent in holding the metals inplace because of low amounts of swelling clays. Instead, insoluble organic matter is more important. Mass balancecalculations for Pb in soil showed that most of the Pb came fromexhausts of vehicles when leaded gasoline was in use, and thatabout 40% of this Pb is retained in the soil.This study shows that, highway environments being a relativelyconstant source of anthropogenic organic matter as well as heavymetals, heavy metals will continue to remain bound to organicmatter in-situ unless they are re-mobilized mechanically. Removalof these heavy metals as wind-blown dust is the most likelymechanism. Another possibility is surface run-off carrying themetals into surface drainages, bypassing the soil. This studyalso shows that for those countries still using leaded gasoline,important reductions in Pb contamination of soils can be achievedby restricting the use of Pb additives.

The use of guided tissue regeneration (GTR) has become an effective procedure for the treatment of gingival recession. No reports exist on the use of a bioabsorbable membrane in combination with a demineralized freeze-dried bone allograft (DFDBA) for the treatment of these defects.Fourteen (14) patients with 17 recession defects were included in this clinical study. Each patient had at least 1 tooth with 3 mm or greater marginal tissue recession on the facial surface as measured from the cemento-enamel junction (CEJ). Each patient was treated by GTR using a bioabsorbable membrane. When the first patient presented for inclusion in the study, a coin was flipped to determine if the tooth being treated would be a test tooth (DFDBA) or a control tooth (no DFDBA). Each subsequent patient was alternated between test and control. Immediately prior to the surgical procedure, measurements were made which included recession depth, recession width at the widest point, probing depth, amount of keratinized tissue, and marginal tissue thickness. Local anesthesia was administered, and a measurement from the CEJ to the bone crest was made by sounding through the attachment.The mean initial recession for all defects was 3.35 mm (SD +/- 0.49) and at 6 months postsurgery, mean recession was 0.47 mm (SD +/0.62). This correlated to 86% root coverage for both treatments. For all defects treated, there was a statistically significant increase in keratinized tissue (mean 0.88 mm) and tissue thickness (mean 0.47 mm) and a significant decrease in probing bone level (mean 0.76 mm). No statistically significant differences were observed between groups for any parameter.Although only 14 subjects with 17 defects were included in this study, the results suggest that the treatment of human gingival recession with a bioabsorbable membrane with or without the use of DFDBA results in significant root coverage, and slight, but significant improvements in keratinized tissue, tissue thickness, and bone level. The greatest limitation of the study was its lack of statistical power. Twenty-two (22) subjects would have been required for the results of the study to show equivalence between groups.

CD44 has been identified at the time of extracellular matrix formation and expansion in several sites of the developing embryo (Wheatley et al. [1993] Development 119:295-306). The nucleus pulposus, consisting of a hydrated extracellular matrix tissue at birth, not previously closely analyzed, was examined for expression of CD44 in the developing and aging rat intervertebral disc. CD44 was identified solely on notochordal cells from the first onset of intervertebral disc formation (day 15 embryo) through the loss of notochordal cells from the nucleus pulposus (12-24 months of age). No CD44 expression was found in the notochordal cells prior to disc formation or in any cells other than the notochordal cells in the annulus fibrosus or nucleus pulposus of the intervertebral disc. Using reverse transcriptase-polymerase chain reaction methodology, the single 365 amino acid CD44 standard, CD44s, open reading frame was amplified from notochordal cells isolated from the nucleus pulposus. Western blot analysis of a cultured nucleus pulposus notochordal cells total protein extract identified a single CD44 species devoid of chondroitin sulfate with a mass of approximately 85 kDa, characteristic of CD44s. Cell surface detection for CD44 was co-localized with hyaluronan and proteoglycans at first appearance of disc formation in the nucleus pulposus.

Acid drainage containing high levels of iron, manganese, and sulfate is a pollution problem widely associated with abandoned coal mines. The remediation of these sites commonly falls to public agencies, so policy-makers need to allocate scarce resources over many sites and to find cost-effective remediation strate- gies. In recent years, constructed wetlands have become a popular alternative to more labor- and capital-intensive treatment systems. Within these wetlands, bacterial sulfate reduction occurs and is often cited as an impor- tant remediation process, but few measurements of reduction rates have been made. We studied the Wills Creek site in NE Ohio, a series of staged constructed wetlands, to evaluate the use of stable isotopes of sulfur as a rapid technique to assess the effectiveness of wetland design. Sulfur isotopes are widely used in marine sedi- ments to measure the rates of bacterial processes, but have not previously been applied to constructed wetlands. Water chemistry measurements indicated that the wetland system as a whole was effectively removing acidity and iron, but not sulfate. We found that sulfate reduction rates were slow relative to the sulfate loadings and that therefore sulfate reduction was ineffective as a remediation process for sulfate contamination in constructed wetlands designed like those at Wills Creek, in agreement with the five-year record of water chemistry measurements. Moreover, our results showed that cells especially constructed to enhance sulfate reduction in fact showed slower reduction rates than more typical compost wetland cells. We conclude that the concept of staged wetlands, although intuitively appealing, is no more effec- tive than a series of ordinary wetlands of the same size. This study illustrates that stable isotopes of sulfur can be a quick and cost-effective way of assessing the func- tioning of bacterial remediation processes in constructed wetlands and could be used by regulatory agencies to evaluate various design strategies. 1 problem of acid mine drainage Acid mine drainage is formed when sulfides (commonly pyrite) from coals and from shales associated with coal beds oxidize by coming in contact with oxygenated water, releasing acid, sulfate, and metals such as Fe, Mn, and Al into the water. The acidic conditions and elevated

The highly permeable sand and gravel of the Little Miami River Valley Aquifer System near Milford, Ohio provide the community with a high-yielding source of drinking water. While this hydrogeologic setting is ideal from a water quantity standpoint, it is greatly vulnerable to contamination. The future viability of the well-field came into question when it was discovered that the wellfield was contaminated with volatile organic contaminants, leaving the City with the costly cleanup. Milford’s perseverance is also challenged by having to deal with a deteriorating treatment plant. Furthermore, larger water suppliers in the area have threatened the community’s independence. The question facing this community, and many other smaller communities, was whether to surrender its independence or invest in their future. The city has decided to keep their wellfield and to conduct a groundwater study. The objectives of the study were to: (a) collect and evaluate hydrogeological data; (b) develop a conceptual model of the groundwater system; (c) construct groundwater flow and geochemical models; (d) delineate wellhead protection area; and (e) develop a comprehensive management program. Collected hydro-geologic data served as a basis for the conceptual model. The U.S. Geological Survey (USGS) three-dimensional groundwater flow model MODFLOW was used in conjunction with MODPATH, a particle-tracking program, to identify travel times and paths of contaminants. This approach ultimately lead to the delineation of the wellhead protection area (WHPA). Geochemical mixing models were constructed using the USGS PHREEQC to verify the flow model results. The use of both flow and geochemical models to delineate the WHPA and to manage groundwater resources is a unique approach. The modeling results provide the City of Milford a management tool in making difficult policy decisions regarding future land use, siting for new monitoring and production wells, and identification of potential pollution sources.

Hyaluronan is an integral component of proteoglycan-rich extracellular matrices such as hyaline cartilage. Hyaluronan is commonly found in embryonic tissue and is important in the formation of hydrated matrices that allow cellular expansion and migration. Cell surface hyaluronan-binding proteins such as CD44 are presumed to be important in the cellular interactions with hyaluronan in both of these processes. The primary aim of this study was to document the spatial and temporal expressions of CD44 isoforms during the development and growth of the diarthrodial joints of rat limbs. With use of in situ hybridization and immunohistochemistry, the CD44s isoform is selectively identified as localized to a single cell layer on opposing sides of the joint at the first appearance of joint cavitation (on the 18th day of gestation). After joint formation in the neonate, the expression of the CD44s isoform in the cells at the joint surface is lost. These findings suggest that the CD44s isoform has a role in the development of the diarthrodial joint, presumably through interaction with hyaluronan.

Manganese is of great interest in geochemistry because its minerals are both tracers of redox processes and accumulators of other elements of geochemical significance. The solubility of manganese compared to iron under reducing and mildly oxidizing conditions leads to its export from low-oxygen environments, be they basalt-hydrothermal systems or euxinic sedimentary basins, and its accumulation in oxidizing environments of the shallow ocean or in low-productivity areas of the deep sea. Therefore tracking Mn/Fe ratios provides us a means of reconstructing the oxidation structure of ocean basins, soils, or groundwater systems.

At a previous meeting (June 1995) a report was given on anomalous behavior of the Rayleigh–Ritz method for calculating the normal mode frequencies of elastic solids (the method that forms the basis for most resonant ultrasound work), when those solids had the shapes of slightly perturbed parallelepipeds. These shapes are of interest to understand the effects of sample preparation errors on the overall elastic constant determination. In an effort to understand these effects, a systematic study of the various interrelated computational issues in RUS has been undertaken. Attempts are made to address the following issues: (1) whether the anomalous behavior of the Rayleigh‐Ritz solutions is algorithmic or numerical; (2) whether these anomalies may result from problems with the inverse calculation (where the frequencies are inverted to obtain elastic constants) as well; and (3) what relationship exists between the RMS error in the frequencies and the confidence in the elastic constant determination. Results wil...

The basement-Lamotte Formation unconformity in southeastern Missouri shows evidence of several distinctive alteration events, some of which may be related to migration of ore-forming fluids or K-rich basinal brines. The alterations are spatially related to the unconformity, suggesting that the unconformity was a preferred pathway for fluid migration. Unconformity-related rocks in five cores penetrating both the Lamotte Formation and the basement have been characterized by bulk chemistry, mineralogy, textures, and paleotopographic position. The alteration history along the unconformity includes: (1) Pre-Lamotte hydrothermal alteration affecting basement, (2) Pre-Lamotte weathering, and (3) Post-Lamotte hydrothermal and diagenetic events. The third group is particularly complex, including early diagenetic hematite and calcite cementation, later quartz cementation, secondary biotite growth, K-metasomatism that generated adulaira, and K-leaching that left a narrow dickite-rich zone along the unconformity. Sev...

Near Delmas, in the Transvaal, a paleoweathering surface is developed beneath the Black Reef on hydrothermally altered granite (HAG). Au in the weathering profile averages 10 ppb, compared with 5 ppb in the HAG. The hydrothermal alteration converted all plagioclase to muscovite and K-feldspar, removing Na and Ca from the rock, and converting ferromagnesian minerals to chlorite. Discontinuous zones in the core were enriched in As, Sb, Co, Au, and La. Superimposed on this hydrothermal alteration was a weathering event that penetrated to about 15 m. K, Rb, Cs, Sr, and Ba were leached. Mg and Fe were depleted in about equal proportion, whereas Ti and Al were conserved, consistent with weathering under a low-$$O_{2}$$ atmosphere. Magnetite in the soil was destroyed and Fe-Ti oxides converted to anatase. Sc and Ta were also leached as a result of destruction of sphene and Fe-Ti oxide without formation of secondary iron oxyhydroxides that re-adsorb these elements in younger soils. A later diagenetic event added ...

It is common to construct a subsidence model for a sedimentary basin when exploring the basin for oil and gas, but subsidence models rarely are used in the search for mineral deposits. To demonstrate the potential of this technique for mineral exploration, we examined geochronologic data from basins with exceptionally large mineral deposits hosted by sedimentary rocks. We chose as examples three basins: one thought to be dominated by foreland thrust loading, one by rifting, and one by strike-slip motion. As a foreland example, we chose the Witwatersrand basin of South Africa, host to the world's largest Au accumulation and regarded by many workers as a rift that subsequently evolved into a ret-roarc foreland basin. Application of a tectonic subsidence model, however, shows that the flexural subsidence expected in the later stages of evolution of a foreland basin did not occur; instead, the basin is dominated by the initial mechanical subsidence of the rift, followed after a long break by renewed rapid subsidence suggestive of a pull-apart basin. The end of this second subsidence episode saw very slow tectonic subsidence and the deposition of the Au-bearing conglomerates. As a rift basin example, we chose the Keweenaw basin, host to the large Cu deposit at White Pine, Michigan. The subsidence model shows two episodes of early rapid subsidence accompanied by great thicknesses of basalt. This volcanic phase was followed by sedimentary infilling of the basin that we equate to the thermal subsidence phase. The model output shows interruption of the thermal phase by two episodes of enhanced subsidence rate, each associated with epigenetic introduction of Cu. The first event was dominantly extensional, the second dominantly compressional. As a basin in a strike-slip terrane, we examined the Huayacocotla basin of eastern Mexico, host to the giant syngenetic Mn deposit at Molango. The model output shows highly episodic subsidence, consistent with deposition in a basin marginal to a major zone of strike-slip activity. Mineralization occurred when sea-level rise and basement subsidence combined to allow Mn-bearing, reducing bottom waters from the Gulf of Mexico to enter the basin...