Downflow Limestone Beds for Treatment of Net-Acidic, Oxic, Iron-Laden Drainage from a Flooded Anthracite Mine, Pennsylvania, USA: 2. Laboratory Evaluation

Acidic mine drainage (AMD) containing elevated concentrations of dissolved iron and other metals can be neutralized to varying degrees by reactions with limestone in passive treatment systems. We evaluated the chemical and mineralogical characteristics and the effectiveness of calcitic and dolomitic limestone for the neutralization of net-acidic, oxic, iron-laden AMD from a flooded anthracite mine. The calcitic limestone, with CaCO3 and MgCO3 contents of 99.8 and \u3c0.1 wt%, respectively, and the dolomitic limestone, with CaCO3 and MgCO3 contents of 60.3 and 40.2 wt%, were used to construct a downflow treatment system in 2003 at the Bell Mine, a large source of AMD and baseflow to the Schuylkill River in the Southern Anthracite Coalfield, in east-central Pennsylvania. In the winter of 2002–2003, laboratory neutralization-rate experiments evaluated the evolution of effluent quality during 2 weeks of continuous contact between AMD from the Bell Mine and the crushed calcitic or dolomitic limestone in closed, collapsible containers (cubitainers). The cubitainer tests showed that: (1) net-alkaline effluent could be achieved with detention times greater than 3 h, (2) effluent alkalinities and associated dissolution rates were equivalent for uncoated and Fe(OH)3-coated calcitic limestone, and (3) effluent alkalinities and associated dissolution rates for dolomitic limestone were about half those for calcitic limestone. The dissolution rate data for the cubitainer tests were used with data on the volume of effuent and surface area of limestone in the treatment system at the Bell Mine to evaluate the water-quality data for the first 1.5 years of operation of the treatment system. These rate models supported the interpretation of field results and indicated that treatment benefits were derived mainly from the dissolution of calcitic limestone, despite a greater quantity of dolomitic limestone within the treatment system. The dissolution-rate models were extrapolated on a decadal scale to indicate the expected decreases in the mass of limestone and associated alkalinities resulting from the long-term reaction of AMD with the treatment substrate. The models indicated the calcitic limestone would need to be replenished approaching the 5-year anniversary of treatment operations to maintain net-alkaline effluent quality

Downflow Limestone Beds for Treatment of Net-Acidic, Oxic, Iron-Laden Drainage from a Flooded Anthracite Mine, Pennsylvania, USA: 2. Laboratory Evaluation

Acidic mine drainage (AMD) containing elevated concentrations of dissolved iron and other metals can be neutralized to varying degrees by reactions with limestone in passive treatment systems. We evaluated the chemical and mineralogical characteristics and the effectiveness of calcitic and dolomitic limestone for the neutralization of net-acidic, oxic, iron-laden AMD from a flooded anthracite mine. The calcitic limestone, with CaCO3 and MgCO3 contents of 99.8 and \u3c0.1 wt%, respectively, and the dolomitic limestone, with CaCO3 and MgCO3 contents of 60.3 and 40.2 wt%, were used to construct a downflow treatment system in 2003 at the Bell Mine, a large source of AMD and baseflow to the Schuylkill River in the Southern Anthracite Coalfield, in east-central Pennsylvania. In the winter of 2002–2003, laboratory neutralization-rate experiments evaluated the evolution of effluent quality during 2 weeks of continuous contact between AMD from the Bell Mine and the crushed calcitic or dolomitic limestone in closed, collapsible containers (cubitainers). The cubitainer tests showed that: (1) net-alkaline effluent could be achieved with detention times greater than 3 h, (2) effluent alkalinities and associated dissolution rates were equivalent for uncoated and Fe(OH)3-coated calcitic limestone, and (3) effluent alkalinities and associated dissolution rates for dolomitic limestone were about half those for calcitic limestone. The dissolution rate data for the cubitainer tests were used with data on the volume of effuent and surface area of limestone in the treatment system at the Bell Mine to evaluate the water-quality data for the first 1.5 years of operation of the treatment system. These rate models supported the interpretation of field results and indicated that treatment benefits were derived mainly from the dissolution of calcitic limestone, despite a greater quantity of dolomitic limestone within the treatment system. The dissolution-rate models were extrapolated on a decadal scale to indicate the expected decreases in the mass of limestone and associated alkalinities resulting from the long-term reaction of AMD with the treatment substrate. The models indicated the calcitic limestone would need to be replenished approaching the 5-year anniversary of treatment operations to maintain net-alkaline effluent quality

Alpersite (Mg,Cu)SO\u3csub\u3e4\u3c/sub\u3e•7H\u3csub\u3e2\u3c/sub\u3eO, A New Mineral of the Melanterite Group, and Cuprian Pentahydrite: Their Occurrence Within Mine Waste

Alpersite, Mg0.58 Cu0.37 Zn0.02 Mn0.02 Fe0.01SO4 •7H2 O, a new mineral species with direct relevance to reactions in mine waste, occurs in a mineralogically zoned assemblage in sheltered areas at the abandoned Big Mike mine in central Nevada at a relative humidity of 65% and T = 4 °C. Blue alpersite, which is isostructural with melanterite (FeSO4 •7H2 O), is overlain by a light blue to white layer dominated by pickeringite, alunogen, and epsomite. X-ray diffraction data (MoKα radiation) from a single crystal of alpersite were refined in P21/c, resulting in wR = 0.05 and cell dimensions a = 14.166(4), b = 6.534(2), c = 10.838(3) Å, β = 105.922(6)°, Z = 4. Site-occupancy refinement, constrained to be consistent with the compositional data, showed Mg to occupy the M1 site and Cu the M2 site. The octahedral distortion of M2 is consistent with 72% Cu occupancy when compared with the site-distortion data of substituted melanterite. Cuprian pentahydrite, with the formula (Mg0.49 Cu0.41 Mn0.08Zn0.02)SO4 •5H2 O, was collected from an effl orescent rim on a depression that had held water in a large waste-rock area near Miami, Arizona. After dissolution of the efflorescence in de-ionized water, and evaporation of the supernatant liquid, alpersite precipitated and quickly dehydrated to cuprian pentahydrite. These observations are consistent with previous experimental studies of the system MgSO4 -CuSO4 -H2 O. It is suspected that alpersite and cuprian pentahydrite are widespread in mine wastes that contain Cu-bearing sulfi des, but in which solubilized Fe2+ is not available for melanterite crystallization because of oxidation to Fe3+ in surface waters of near-neutral pH. Alpersite has likely been overlooked in the past because of the close similarity of its physical properties to those of melanterite and chalcanthite. Alpersite is named after Charles N. Alpers, geochemist with the United States Geological Survey, who has made significant contributions to our understanding of the mineralogical controls of mine-water geochemistry

Mineralogical and Chemical Characteristics of Some Natural Jarosites

This paper presents a detailed study of the mineralogical, microscopic, thermal, and spectral characteristics of jarosite and natrojarosite minerals. Systematic mineralogic and chemical examination of a suite of 32 natural stoichiometric jarosite and natrojarosite samples from diverse supergene and hydrothermal environments indicates that there is only limited solid solution between Na and K at low temperatures, which suggests the presence of a solvus in the jarosite-natrojarosite system at temperatures below about 140 °C. The samples examined in this study consist of either end members or coexisting end-member pairs of jarosite and natrojarosite. Quantitative electron-probe microanalysis data for several natural hydrothermal samples show only end-member compositions for individual grains or zones, and no detectable alkali-site deficiencies, which indicates that there is no hydronium substitution within the analytical uncertainty of the method. In addition, there is no evidence of Fe deficiencies in the natural hydrothermal samples. Hydronium-bearing jarosite was detected in only one relatively young supergene sample suggesting that terrestrial hydronium-bearing jarosites generally are unstable over geologic timescales. Unit-cell parameters of the 20 natural stoichiometric jarosites and 12 natural stoichiometric natrojarosites examined in this study have distinct and narrow ranges in the a- and c-cell dimensions. There is no overlap of these parameters at the 1r level for the two end-member compositions. Several hydrothermal samples consist of fine-scale (2–10 lm) intimate intergrowths of jarosite and natrojarosite, which could have resulted from solid-state diffusion segregation or growth zoning due to variations in the Na/K activity ratio of hydrothermal solutions

Mineralogical and Chemical Characteristics of Some Natural Jarosites

This paper presents a detailed study of the mineralogical, microscopic, thermal, and spectral characteristics of jarosite and natrojarosite minerals. Systematic mineralogic and chemical examination of a suite of 32 natural stoichiometric jarosite and natrojarosite samples from diverse supergene and hydrothermal environments indicates that there is only limited solid solution between Na and K at low temperatures, which suggests the presence of a solvus in the jarosite-natrojarosite system at temperatures below about 140 °C. The samples examined in this study consist of either end members or coexisting end-member pairs of jarosite and natrojarosite. Quantitative electron-probe microanalysis data for several natural hydrothermal samples show only end-member compositions for individual grains or zones, and no detectable alkali-site deficiencies, which indicates that there is no hydronium substitution within the analytical uncertainty of the method. In addition, there is no evidence of Fe deficiencies in the natural hydrothermal samples. Hydronium-bearing jarosite was detected in only one relatively young supergene sample suggesting that terrestrial hydronium-bearing jarosites generally are unstable over geologic timescales. Unit-cell parameters of the 20 natural stoichiometric jarosites and 12 natural stoichiometric natrojarosites examined in this study have distinct and narrow ranges in the a- and c-cell dimensions. There is no overlap of these parameters at the 1r level for the two end-member compositions. Several hydrothermal samples consist of fine-scale (2–10 lm) intimate intergrowths of jarosite and natrojarosite, which could have resulted from solid-state diffusion segregation or growth zoning due to variations in the Na/K activity ratio of hydrothermal solutions

Weathering of Sulfidic Shale and Copper Mine Waste: Secondary Minerals and Metal Cycling in Great Smoky Mountains National Park, Tennessee, and North Carolina, USA

Metal cycling via physical and chemical weathering of discrete sources (copper mines) and regional (non-point) sources (sulfide-rich shale) is evaluated by examining the mineralogy and chemistry of weathering products in Great Smoky Mountains National Park, Tennessee, and North Carolina, USA. The elements in copper mine waste, secondary minerals, stream sediments, and waters that are most likely to have negative impacts on aquatic ecosystems are aluminum, copper, zinc, and arsenic because these elements locally exceed toxicity guidelines for surface waters or for stream sediments. Acid-mine drainage has not developed in streams draining inactive copper mines. Acid-rock drainage and chemical weathering processes that accompany debris flows or human disturbances of sulfidic rocks are comparable to processes that develop acid-mine drainage elsewhere. Despite the high rainfall in the mountain range, sheltered areas and intermittent dry spells provide local venues for development of secondary weathering products that can impact aquatic ecosystems

Cretaceous plutons of the Peninsular Ranges batholith, San Diego and westernmost Imperial Counties, California : intrusion across a Late Jurassic continental margin

The Peninsular Ranges batholith of southern California and Baja California was emplaced across the litho spheric boundary between North America and Pacific plates in the Jurassic and Cretaceous, In San Diego County, the locus of Cretaceous plutonism migrated eastward from oceanic lithosphere across the continental margin into early Mesozoic continental lithosphere Uplift and westward tilting of the Peninsular Ranges block associated with Late Cenozoic rifting and transform faulting resulted in au erosional depth profile from volcanic levels in the west to mid-crustal depths in the east. Our study of Cretaceous plutons in a west-to-east transect across southern San Diego County shows that granitic plutons have distinctive geophysical, geobarometric, mineralogical, geochemical, and isotopic characteristics that vary systematically with geographic position within the batholith, On the basis of these characteristics, granitic plutons are grouped into 10 plutonic suites, each comprising numerous plutons In the west-central part of the study area, five granitic suites and a suite of gabbroic rocks comprise a series of large, concentrically zoned plutonic complexes, possibly the roots of ring complexes. Mingling contacts between granitic and gabbroic plutons within these complexes indicate that mafic and silicic magmas were produced simultaneously during Cretaceous intrusion. Published and unpublished isotopic age studies indicate that plutons in the western zone are primarily of Early and middle Cretaceous age, whereas those in the eastern zone are middle to Late Cretaceous in age. Our delineation of western and eastern plutonic zones on the basis of the geographic distribution and compositions of plutonic suites corresponds closely with previously noted west-to-east batholithic asymmetries. Primary among these is a steep aeromagnetic- and gravity-anomaly gradient that coincides closely with the westernmost limit of Jurassic granites and their early Mesozoic wallrocks. This gradient is interpreted as the manifestation of an east-dipping fault of crustal dimensions that formed in the latest Jurassic-earliest Cretaceous (Shaw et al., this volume, Chapter 7). The distribution of Cretaceous plutonic suites, together with compositional changes in suites that intrude both western and eastern zones of the batholith, are considered to reflect the location of the fault-bounded Late Jurassic continental margin. Geochemical studies of the Cretaceous granitic suites characterize them as low-K₂0, low-Rb, calcic granites with aluminium saturation indices (ASI, i.e., molar Al����O����/[CaO+Na���O+K₂O] values) between 0.67 and 1.20, reflecting a significant mantle contribution in the source of the magmas. Systematic variations in the geographic distribution and composition of suites indicate that partial melting of chemically inhomogeneous, pH₂O -variable metaigneous rocks in the lower crust played a significant role in their origin. Constant rare earth element patterns and low Sr₁ values of the suites across the gravity-magnetic boundary suggest that source rocks of basaltic composition were present in the lower crust and/or as underplates from earlier subduction episodes beneath both western and eastern zones of the batholith. Compositional differences among five tonalite suites reflect (1) increasing crustal thickness flam the Early to Late Cretaceous, causing a phase transition of the zone of melting toward eclogitic assemblages, and/or (2) increasing depths of melting as the magmatic arc migrated eastward. Four leucogranite suites apparently represent fractionates of mafic melts, and/or partial melts of lithologically distinctive lower crustal rocks. The interaction of magmas with western and eastern lithosphere during ascent and emplacement was responsible for slight eastward increases in K₂O, Rb, initial ⁸⁷Sr/⁸⁶Sr ratios, δ¹⁸0 values, and radiogenic lead isotopes in suites that are present in both western and eastern zones, as well as for east-west differences in opaque oxide mineralogy and magnetic properties. The data of our study imply that a single Cretaceous magmatic arc migrated eastward across a pre-existing Late Jurassic-earliest Cretaceous lithospheric boundary, the distribution of known Cretaceous pluton ages does not require an age break, but rather suggests continuous eastward migration of a single magmatic arc. Published and unpublished Early Cretaceous pluton ages for the oldest Cretaceous granitic suite that stitched across the lithospheric boundary in this region constrain the minimum age of its formation as early EarIy Cretaceous.51 page(s