Percent Pyrite Research Articles

839 AMBULATORY BLOOD PRESSURE MONITORING AS PREDICTOR OF SUBCLINICAL ATHEROSCLEROSIS IN ADOLESCENTS

Upper Paleocene to middle Miocene coal samples collected from active mines in the western Venezuelan States of Táchira, Mérida and Zulia have been characterized through an integrated geochemical, mineralogical and petrographic investigation. Proximate, ultimate, calorific and forms of sulfur values, major and trace element, vitrinite reflectance, maceral concentrations and mineral matter content have been determined for 16 channel samples from 14 mines. Ash yield generally is low, ranging from < 1 to 17 wt.% (mean = 5 wt.%) on a dry basis (db). Total sulfur content is low to moderate, ranging from 1 to 6 wt.%, db (average = 1.7 wt.%). Calorific value ranges from 25.21 to 37.21 MJ/kg (10,840–16,000 Btu/lb) on a moist, mineral-matter-free basis (average = 33.25 MJ/kg, 14,300 Btu/lb), placing most of the coal samples in the apparent rank classification of high-volatile bituminous. Most of the coal samples exhibit favorable characteristics on the various indices developed to predict combustion and coking behavior and concentrations of possible environmentally sensitive elements (As, Be, Cd, Cr, Co, Hg, Mn, Ni, Pb, Sb, Se, Th and U) generally are similar to the concentrations of these elements in most coals of the world, with one or two exceptions. Concentrations of the liptinite maceral group range from < 1% to 70 vol.%. Five samples contain > 20 vol.% liptinite, dominated by the macerals bituminite and sporinite. Collotelinite dominates the vitrinite group; telinite was observed in quantities of ≤ 1 vol.% despite efforts to better quantify this maceral by etching the sample pellets in potassium permanganate and also by exposure in an oxygen plasma chamber. Inertinite group macerals typically represent < 10 vol.% of the coal samples and the highest concentrations of inertinite macerals are found in distantly spaced (> 400 km) upper Paleocene coal samples from opposite sides of Lago de Maracaibo, possibly indicating tectonic controls on subsidence related to construction of the Andean orogen. Values of maximum reflectance of vitrinite in oil (Ro max) range between 0.42% and 0.85% and generally are consistent with the high-volatile bituminous rank classification obtained through ASTM methods. X-ray diffraction analyses of low-temperature ash residues indicate that kaolinite, quartz, illite and pyrite dominate the inorganic fraction of most samples; plagioclase, potassium feldspar, calcite, siderite, ankerite, marcasite, rutile, anatase and apatite are present in minor or trace concentrations. Semiquantitative values of volume percent pyrite content show a strong correlation with pyritic sulfur and some sulfide-hosted trace element concentrations (As and Hg). This work provides a modern quality dataset for the western Venezuela coal deposits currently being exploited and will serve as the foundation for an ongoing coal quality research program in Venezuela.

English

Fourteen samples of pyrite-bearing Archean greenstone rock (d < 6.35 mm, 0.08 ≤ FeS2 ≤ 2.25 wt. %) were characterized and subjected to laboratory dissolution testing for periods of 154 or 204 weeks. Rates of pyrite oxidation were determined based on the observed rates of sulfate release between weeks 20 and 60 and the calculated pyrite surface areas exposed. The pyrite surface areas exposed were determined based on the particle size distribution, sulfur content of individual size fractions, and percent pyrite liberation. The pyrite oxidation rates, normalized for exposed surface area, ranged from 4 × 10 −10 to 18 × 10 −10 mol m −2 s −1 and tended to increase as drainage pH decreased from 7.3 to 3.3. For eight rock samples with median pH values above 6.0, rates were roughly 0.6 to 1.3 times those predicted in the literature for the abiotic oxidation of pyrite by oxygen. Median pH values for the remaining six samples ranged from 3.3 to 5.0, and pyrite oxidation rates were roughly 2 to 8 times the published abiotic rates, suggesting the influence of oxidation by ferric iron.

Petrology, mineralogy and geochemistry of mined coals, western Venezuela

Upper Paleocene to middle Miocene coal samples collected from active mines in the western Venezuelan States of Táchira, Mérida and Zulia have been characterized through an integrated geochemical, mineralogical and petrographic investigation. Proximate, ultimate, calorific and forms of sulfur values, major and trace element, vitrinite reflectance, maceral concentrations and mineral matter content have been determined for 16 channel samples from 14 mines. Ash yield generally is low, ranging from < 1 to 17 wt.% (mean = 5 wt.%) on a dry basis (db). Total sulfur content is low to moderate, ranging from 1 to 6 wt.%, db (average = 1.7 wt.%). Calorific value ranges from 25.21 to 37.21 MJ/kg (10,840–16,000 Btu/lb) on a moist, mineral-matter-free basis (average = 33.25 MJ/kg, 14,300 Btu/lb), placing most of the coal samples in the apparent rank classification of high-volatile bituminous. Most of the coal samples exhibit favorable characteristics on the various indices developed to predict combustion and coking behavior and concentrations of possible environmentally sensitive elements (As, Be, Cd, Cr, Co, Hg, Mn, Ni, Pb, Sb, Se, Th and U) generally are similar to the concentrations of these elements in most coals of the world, with one or two exceptions. Concentrations of the liptinite maceral group range from < 1% to 70 vol.%. Five samples contain > 20 vol.% liptinite, dominated by the macerals bituminite and sporinite. Collotelinite dominates the vitrinite group; telinite was observed in quantities of ≤ 1 vol.% despite efforts to better quantify this maceral by etching the sample pellets in potassium permanganate and also by exposure in an oxygen plasma chamber. Inertinite group macerals typically represent < 10 vol.% of the coal samples and the highest concentrations of inertinite macerals are found in distantly spaced (> 400 km) upper Paleocene coal samples from opposite sides of Lago de Maracaibo, possibly indicating tectonic controls on subsidence related to construction of the Andean orogen. Values of maximum reflectance of vitrinite in oil ( R o max) range between 0.42% and 0.85% and generally are consistent with the high-volatile bituminous rank classification obtained through ASTM methods. X-ray diffraction analyses of low-temperature ash residues indicate that kaolinite, quartz, illite and pyrite dominate the inorganic fraction of most samples; plagioclase, potassium feldspar, calcite, siderite, ankerite, marcasite, rutile, anatase and apatite are present in minor or trace concentrations. Semiquantitative values of volume percent pyrite content show a strong correlation with pyritic sulfur and some sulfide-hosted trace element concentrations (As and Hg). This work provides a modern quality dataset for the western Venezuela coal deposits currently being exploited and will serve as the foundation for an ongoing coal quality research program in Venezuela.

98/03521 High-temperature desulfurization of fossil fuels by microbes

Upper Paleocene to middle Miocene coal samples collected from active mines in the western Venezuelan States of Táchira, Mérida and Zulia have been characterized through an integrated geochemical, mineralogical and petrographic investigation. Proximate, ultimate, calorific and forms of sulfur values, major and trace element, vitrinite reflectance, maceral concentrations and mineral matter content have been determined for 16 channel samples from 14 mines. Ash yield generally is low, ranging from < 1 to 17 wt.% (mean = 5 wt.%) on a dry basis (db). Total sulfur content is low to moderate, ranging from 1 to 6 wt.%, db (average = 1.7 wt.%). Calorific value ranges from 25.21 to 37.21 MJ/kg (10,840–16,000 Btu/lb) on a moist, mineral-matter-free basis (average = 33.25 MJ/kg, 14,300 Btu/lb), placing most of the coal samples in the apparent rank classification of high-volatile bituminous. Most of the coal samples exhibit favorable characteristics on the various indices developed to predict combustion and coking behavior and concentrations of possible environmentally sensitive elements (As, Be, Cd, Cr, Co, Hg, Mn, Ni, Pb, Sb, Se, Th and U) generally are similar to the concentrations of these elements in most coals of the world, with one or two exceptions. Concentrations of the liptinite maceral group range from < 1% to 70 vol.%. Five samples contain > 20 vol.% liptinite, dominated by the macerals bituminite and sporinite. Collotelinite dominates the vitrinite group; telinite was observed in quantities of ≤ 1 vol.% despite efforts to better quantify this maceral by etching the sample pellets in potassium permanganate and also by exposure in an oxygen plasma chamber. Inertinite group macerals typically represent < 10 vol.% of the coal samples and the highest concentrations of inertinite macerals are found in distantly spaced (> 400 km) upper Paleocene coal samples from opposite sides of Lago de Maracaibo, possibly indicating tectonic controls on subsidence related to construction of the Andean orogen. Values of maximum reflectance of vitrinite in oil (Ro max) range between 0.42% and 0.85% and generally are consistent with the high-volatile bituminous rank classification obtained through ASTM methods. X-ray diffraction analyses of low-temperature ash residues indicate that kaolinite, quartz, illite and pyrite dominate the inorganic fraction of most samples; plagioclase, potassium feldspar, calcite, siderite, ankerite, marcasite, rutile, anatase and apatite are present in minor or trace concentrations. Semiquantitative values of volume percent pyrite content show a strong correlation with pyritic sulfur and some sulfide-hosted trace element concentrations (As and Hg). This work provides a modern quality dataset for the western Venezuela coal deposits currently being exploited and will serve as the foundation for an ongoing coal quality research program in Venezuela.

An evaluation of trace element release associated with acid mine drainage

The determination of trace element release from geologic materials, such as oil shale and coal overburden, is important for proper solid waste management planning. The objective of this study was to determine a correlation between trace element residency and concentration to trace element release using the following methods: (1) sequential selective dissolution for determining trace element residencies, (2) toxicity characteristic leaching procedure (TCLP), and (3) humidity cell weathering study simulating maximum trace element release. Two eastern oil shales were used, a New albany shale that contains 4.6 percent pyrite, and a Chattanooga shale that contains 1.5 percent pyrite. Each shale was analyzed for elemental concentrations by soluble, adsorbed, organic, carbonate, and sulfide phases. All leachates were analyzed to determine total trace element concentrations.

Solubility relationships of aluminum and iron minerals associated with acid mine drainage

The ability to properly manage the oxidation of pyritic minerals and associated acid mine drainage is dependent upon understanding the chemistry of the disposal environment. One accepted disposal method is placing pyritic-containing materials in the groundwater environment. The objective of this study was to examine solubility relationships of Al and Fe minerals associated with pyritic waste disposed in a low leaching aerobic saturated environment. Two eastern oil shales were used in this oxidizing equilibration study, a New Albany Shale (unweathered, 4.6 percent pyrite), and a Chattanooga Shale (weathered, 1.5 percent pyrite). Oil shale samples were equilibrated with distilled-deionized water from 1 to 180 d with a 1∶1 solid-to-solution ratio. The suspensions were filtered and the clear filtrates were analyzed for total cations and anions. Ion activities were calculated from total concentrations. Below pH 6.0, depending upon SO 4 2− activity, Al3+ solubility was controlled by AlOHSO4 (solid phase) for both shales. Initially, Al3+ solubility for the New Albany Shale showed equilibrium with amorphous Al(OH)3. The pH decreased with time, and Al3+ solubility approached equilibrium with AlOHSO4(s). Below pH 6.0, Fe3+ solubility appeared to be regulated by a basic iron sulfate solid phase with the stoichiometric composition of FeOHSO4(s). The results of this study indicate that below pH 6.0, Al3+ solubilities, are limited by basic Al and Fe sulfate solid phases (AlOHSO4(s) and FeHSO4(s)). The results from this study further indicate that the acidity in oil shale waters is produced from the hydrolysis of Al3+ and Fe3+ activities in solution. These results indicate a fundamental change in the stoichiometric equations used to predict acidity from iron sulfide oxidation. The results of this study also indicate that water quality predictions associated with acid mine drainage can be based on fundamental thermodynamic relationships. As a result, waste management decisions can be based on waste-specific/site-specific test methods.

Iron sulfide oxidation and the chemistry of acid generation

Acid mine drainage, produced from the oxidation of iron sulfides, often contains elevated levels of dissolved aluminum (AI), iron (Fe), and sulfate (SO4) and low pH. Understanding the interactions of these elements associated with acid mine drainage is necessary for proper solid waste management planning. Two eastern oil shales were leached using humidity cell methods. This study used a New Albany Shale (4.6 percent pyrite) and a Chattanooga Shale (1.5 percent pyrite). The leachates from the humidity cells were filtered, and the filtrates were analyzed for total concentrations of cations and anions. After correcting for significant solution species and complexes, ion activities were calculated from total concentrations. The results show that the activities of Fe3+, Fe2+, Al3+, and SO4 2− increased due to the oxidation of pyrite. Furthermore, the oxidation of pyrite resulted in a decreased pH and an increased pe+pH (redox-potential). The Fe3+ and Fe2+ activities appeared to be controlled by amorphous Fe(OH)3 solid phase above a pH of 6.0 and below pe+pH 11.0. The Fe3+, Fe2+, and SO4 2− activities reached saturation with respect to FeOHSO4 solid phase between pH 3.0 and 6.0 and below pe+pH 11.0 Below a pH of 3.0 and above a pe+pH of 11.0, Fe2+, Fe3+, and SO4 2− activities are supported by FeSO4·7H2O solid phase. Above a pH of 6.0, the Al3+ activity showed an equilibrium with amorphous Al(OH)3 solid phase. Below pH 6.0, Al3+ and SO4 2− activities are regulated by the AlOHSO4 solid phase, irrespective of pe+pH. The results of this study suggest that under oxidizing conditions with low to high leaching potential, activities of Al and Fe can be predicted on the basis of secondary mineral formation over a wide range of pH and redox. As a result, the long-term chemistry associated with disposal environments can be largely predicted (including trace elements).

Petrography and Taphonomic Significance of the Vertebrate-Bearing Cannel Coal of Linton, Ohio (Westphalian D, Upper Carboniferous)

ABSTRACT Petrographic study of a vertebrate-bearing cannel coal which underlies the Upper Freeport coal (late Westphalian D, Upper Carboniferous) in the area of Linton, Ohio, provides information on the depositional conditions represented by fossiliferous sapropelic coals. Samples of the cannel obtained from an approximately 10-km-long curvilinear area were prepared as polished blocks and point counted in reflected light. The cannel typically consists of over 50 percent very finely grained, micrinite-rich groundmass; approximately 25 percent exinite and 10 percent pyrite; and varying amounts of vitrinite and inertinite. Sporinite is the most abundant exinite, but no alginite occurs; euhedra and framboids are the most common forms of pyrite; and vitrinite is poorly preserved and virtually struc ureless. Vertebrate scales, teeth, and bones preserved in the cannel show no significant mineralogic alteration. These petrographic findings agree with results from an investigation of the physical paleoenvironment of the Linton deposit, and together these data sets indicate that the vertebrate-bearing cannel represents a freshwater sapropelic peat that formed within abandoned segments of a fluviodeltaic channel. In the absence of clastic influx, macerated plant debris and resistant spores accumulated in the bottom of the channel, and decay of these organic-rich sediments led to anaerobic conditions in which sulfate-reducing bacteria thrived. Vertebrate remains introduced from the overlying oxygenated waters were not subjected to scavenging in this anoxic, nonacidic setting but slowly rotted, leaving skeletal parts intact.

A Diffraction-Based Pyrite Monitor

The design and performance of a pyrite monitor for use in coal cleaning production plants is described. The method used is that of X-ray diffraction. It has been demonstrated that pyrite and most other minerals even if embedded in a coal matrix still yield sharp characteristic diffraction patterns which are superimposed on the broad diffuse peaks due to coal itself. The monitor has been designed to measure a strong, characteristic pyrite diffraction peak at 15.10°2θ obtained by using a Mo K x X-ray source. Use of this source appreciably reduces absorption effects; therefore percent pyrite can be obtained from the pyrite diffraction intensity via a simple calibration curve. A sample delivery system incorporating a computer-controlled moving belt mechanism is an integral part of this instrument and ensures the monitoring of a reasonable fraction of the coal stream. The X-ray detector scans a 3° range centered on the pyrite peak under computer control; intensity data are then smoothed, background is subtracted, the percent pyrite determined, and the results displayed on the computer's monitor screen. Operation is via response to menu items on a computer screen; stored data can be displayed in a variety of forms. Results are given for coals from a number of sources. Good agreement ( ± 0.2%) with ASTM wet chemical analysis is demonstrated.

Dielectric properties of pyrite samples at 1 100 MHz

Pyrite occurs in many petroleum reservoirs and significantly affects density and electric well logs even in low concentrations. Ultrahigh‐frequency dielectric measurements also are significantly affected by pyrite. Dielectric properties of core samples containing approximately 50 percent pyrite by volume were measured from 800 to 1 200 MHz ([Formula: see text]). These measurements demonstrate the high, complex dielectric permittivity of pyrite and provide data for calculation of pyrite permittivity at ultrahigh frequencies. The measured complex‐permittivity of water‐saturated pyrite nodules is approximately [Formula: see text] at 1 100 MHz and 25 °C. The measured permittivity of pyrite nodules depends upon the concentration of pyrite and only slightly on saturating‐water salinity. Two geometric mixing models, the complex refractive‐index method (CRIM) and a modified Hanai‐Bruggeman‐Sen (HBS) model, are used to analyze the data. CRIM analysis of water‐saturated and oil‐saturated core data gives inconsistent results because the porosity is poorly connected. HBS, with a variable dielectric exponent, provides more consistent results. [Formula: see text] is the complex permittivity of pyrite at 1 100 MHz and 25 °C determined by applying HBS to laboratory measurements. CRIM‐determined pyrite permittivity is about 50 percent greater in both real and imaginary parts. This high [Formula: see text] has important implications for high‐frequency dielectric well‐logging tools. Signal amplitudes are highly attenuated in formations with large concentrations of pyrite. Where pyrite nodules occur, wave scattering may cause inconsistent data indicative of formation heterogeneity. Low concentration, disseminated pyrite increases the rock “matrix” permittivity. Mineralogical variations, particularly in trace quantities of heavy minerals, are a likely explanation for significant variations in measured matrix permittivities for sandstones. Comparison of pyrite permittivity with available values for the permittivity of rutile, another heavy mineral found in sedimentary rocks, suggests employing pyrite and rutile in artificial sandpack experiments. The real parts of pyrite and rutile permittivities are nearly equal, but the imaginary part of the permittivity of rutile is lower than pyrite by about [Formula: see text]. Experiments with both minerals could test mixing models and the effects of distribution in mixtures of conductive minerals.

Oil field brines as ore-forming solutions

Analyses of oil field brines from the Pleasant Bayou in the upper Texas Gulf Coast and the Rayleigh Field in central Mississippi were used to calculate the pH of the brines under reservoir conditions by assuming equilibrium with the reservoir mineral assemblages. The calculated pH values are less than 5.7 for the Pleasant Bayou brines at 138 degrees C and 787 bars and 4.3 (+ or -0.3) for the Rayleigh Field brines at 130 degrees C and 390 bars. Typical water-rock interactions have been investigated by theoretical evaluation of the thermodynamic consequences of the reactions of a hypothetical low-pH oilfield brine with quartz sandstone and dolostone aquifers that contain about 3 percent K-feldspar, 0.2 percent muscovite, and 0.01 percent pyrite by volume. The correlation of lead-rich (Southeast Missouri and Laisvall, Sweden) and zinc-rich (upper Mississippi Valley and East Tennessee) deposits with sandstone and dolostone aquifers, respectively, suggests that the reaction capacity of sandstone is more efficiently exhausted than that of dolostone. Importance in explaining geochemical characteristics of base-metal sulfide ore deposits. --Modified journal abstract.

Discovery of a mineralized breccia pipe using gradient array induced polarization

The Promontorio breccia pipe located in southern Sonora, Mexico, has been mined intermittently for silver since the turn of the century. Mineralization occurs as sulfides in the matrix of the breccia. Two to five percent pyrite also occurs in the premineral andesite that the breccia pipe has intruded. Geologic mapping led to the discovery of a small, unmineralized breccia in andesite 200 m west of Promontorio. The discovery of this breccia encouraged the search for other hidden mineralized breccias in areas obscured by postmineral alluvium. Exploration of the covered areas was carried out with an induced polarization (IP) and resistivity survey after a test line indicated that a distinct IP anomaly occurs over the Promontorio breccia pipe. The gradient array was chosen as the most effective electrode configuration to explore the covered areas because it can provide rapid detailed IP coverage necessary to locate small breccia pipes. Several anomalous IP trends were located. The most interesting one has an apparent response of 60 to 90 msec in low‐resistivity rocks similar to Promontorio. Additional information provided by dipole‐dipole profiles indicates that this anomalous zone is close to surface and about 20 m wide with a vertical to steep dip. Trenching and drilling confirmed the presence of a 20-m wide elongate breccia with sulfide mineralization similar to Promontorio. Silver grades were marginal for making ore in 1977.

APPLICATION OF BOREHOLE GEOPHYSICS AT AN EXPERIMENTAL WASTE STORAGE SITE*

AbstractA suite of electrical, radiation, and mechanical borehole probes were run in a 76‐mm‐diameter borehole drilled to a slant depth of 380 m in leptite and granite. The hole is located in Precambrian bedrock in central Sweden where a site is dedicated to in‐situ experiments pertaining to the disposal of radioactive wastes. The challenge to borehole logging methods for such site investigations is to resolve geological features and fluid flow parameters in geological sites which are initially chosen for their homogeneity, low porosity, and minimal fracturing. The Stripa borehole is characterized by high electrical resistivity values in the 20–100 kΩm range, by acoustic velocities around 5800 m s‐1 (which is close to laboratory values on intact specimens), and by total porosity of around one volume percent. In this context, probe resolution was adequate to produce interpretable information on almost all of the logs.Two principal rock types were encountered in the hole: granite, of quartz monzonitic composition, and leptite. The granite and leptite intercepts are subdivided into units characterized by mafic mineral content, sulfide mineral content, and electrical and radiation properties. Iron‐rich zones in the leptite are highly anomalous on the gamma‐gamma and neutron logs; thin mafic zones in the granite can also be distinguished. Occurrences of a few percent pyrite are detected by the electrical, gamma‐gamma, and neutron logs. Although overall porosity is quite low throughout the hole, analysis of the resistivity and neutron logs indicates the porosity increases by a few volume percent at fracture zones. The differential resistance and caliper probes detect borehole diameter roughness of less than 1 mm, helping to confirm acoustic waveform anomalies which are indicative of fracture zones. Compres‐sional wave transit time and shear‐wave interference patterns usually occur coincident with open fractures observed in core, the correlation being especially good at major fracture zones.

Lithologic determination of mass transfer mechanisms of multiple-stage porphyry copper mineralization at Butte, Montana; vein formation by hypogene leaching and enrichment of potassium-silicate protore

Lithologic determination of mass transfer mechanisms of multiple-stage porphyry copper mineralization at Butte, Montana; vein formation by hypogene leaching and enrichment of potassium-silicate protore

Deformation of Mine Floors by Sulfide Alteration

Research Article| January 01, 1977 Deformation of Mine Floors by Sulfide Alteration RAYMOND M. COVENEY; RAYMOND M. COVENEY Raymond M. Coveney and Eldon J. Parizek are with the Department of Geosciences at the University of Missouri, Kansas City, Missouri. Search for other works by this author on: GSW Google Scholar ELDON J. PARIZEK ELDON J. PARIZEK Raymond M. Coveney and Eldon J. Parizek are with the Department of Geosciences at the University of Missouri, Kansas City, Missouri. Search for other works by this author on: GSW Google Scholar Author and Article Information RAYMOND M. COVENEY Raymond M. Coveney and Eldon J. Parizek are with the Department of Geosciences at the University of Missouri, Kansas City, Missouri. ELDON J. PARIZEK Raymond M. Coveney and Eldon J. Parizek are with the Department of Geosciences at the University of Missouri, Kansas City, Missouri. Publisher: Association of Environmental & Engineering Geologists First Online: 02 Mar 2017 Online Issn: 1558-9161 Print Issn: 1078-7275 © 1977 Association of Engineering Geologists Environmental & Engineering Geoscience (1977) xiv (3): 131–156. https://doi.org/10.2113/gseegeosci.xiv.3.131 Article history First Online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation RAYMOND M. COVENEY, ELDON J. PARIZEK; Deformation of Mine Floors by Sulfide Alteration. Environmental & Engineering Geoscience 1977;; xiv (3): 131–156. doi: https://doi.org/10.2113/gseegeosci.xiv.3.131 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyEnvironmental & Engineering Geoscience Search Advanced Search Abstract Heaving of mine floors in Kansas City's underground space facilities appears to be the result of volume changes caused by the oxidation of sulfides contained in shale. The Hushpuckney shale which underlies and forms the mine floors contains 2–6 weight percent pyrite, which is sufficient to account for an average 3–4 inch floor deformation after oxidation. Favored possible countermeasures to alleviate the floor deformation, when necessary, include (1) immediate coating of the shale after excavation with bitumen or a comparable airtight substance, (2) flooding the shales with water, and (3) complete removal of shales beneath the floors and mine pillars of the space facilities with a concrete fill emplaced to form the bases of the pillars. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Syngenetic pyrite associated with a Precambrian iron ore deposit

The Steeprock pyritic zones are conformable, lenticular bodies in and along the hanging wall of an iron ore-bearing member of a Precambrian volcanic-sedimentary sequence in north western Ontario. The zones contain about 50 percent pyrite. About 90 percent of this pyrite consists of fragments possessing coloform and cryptocrystalline textures. This type of pyrite does not replace any minerals or rocks, but is veined and replaced by later crystalline pyrite, goethite, and hematite. A trace element study reveals a marked paucity in the number and quantity of the trace elements present. This, combined with the low cobalt content, low cobalt-nickel ratios, presence of arsenic in the pyrite, and the negligible selenium content, indicates that, with respect to the trace element content, the Steeprock pyrite is more akin to known sedimentary pyrite than it is to hydrothermal pyrite. The Steeprock pyrite, contrary to other published opinions, is regarded as a syngenetic sedimentary deposit of Precambrian age precipitated in restricted basins under anaerobic conditions. Iron is considered to have been derived through chemical weathering of a nearby ferruginuous limestone-dolomite member of the Steeprock group; sulfur is thought to have been contributed by anaerobic bacteria and volcanic activity that is clearly closely related in time and space to the pyrite.

A STUDY IN INDUCED POLARIZATION

Induced polarization in pyritic sandstone arises in part from overvoltage effects and in part from electrolytic polarization. Because induced‐polarization measurements are commonly used to search for sulfides, the electrolytic polarization is an undesirable background effect. Pyrite in sandstone can be located only when overvoltage polarization substantially exceeds electrolytic polarization. Laboratory measurements indicate this is true only if there is ten percent or more pyrite in a rock. However, overvoltage polarization is much larger when low current densities are used, particularly if the matrix resistivity is high. Field measurements indicate that at low current densities as little as one or two percent pyrite may provide sufficient overvoltage polarization to be recognizable in the presence of electrolytic polarization.

Determination of Carbon Dioxide and other Volatiles in Pyritic Limestones by Loss on Ignition

ABSTRACT A loss-on-ignition of limestones to 1000° C interrupted at 550° C for an intermediate weighing provided much of the information needed to calculate carbon dioxide gravimetrically but was complicated by the oxidation of pyrite, which is present in small quantities in many limestones. Upon oxidation pyrite formed Fe2O3 and oxides of sulfur which in turn reacted with CaCO3 below the intermediate temperature to form CaSO4 and cause a premature evolution of CO2. It is necessary to determine sulfate sulfur and total sulfur in the raw sample and sulfate sulfur after loss-on-ignition at 1000° C. In limestones containing one percent or more pyrite, a sulfate determination after ignition at 550° C is necessary in addition to the other three sulfate determinations. These data enable calculation of a true CO2 value and a single value for all other volatiles gravimetrically in each sample.