Origin of secondary sulfate minerals on active andesitic stratovolcanoes

Sulfate minerals in altered rocks on the upper flanks and summits of active andesitic stratovolcanoes result from multiple processes. The origin of these sulfates at five active volcanoes, Citlalte´petl (Mexico), and Mount Adams, Hood, Rainier, and Shasta (Cascade Range, USA), was investigated using field observations, petrography, mineralogy, chemical modeling, and stable-isotope data. The four general groups of sulfate minerals identified are: (1) alunite group, (2) jarosite group, (3) readily soluble Fe- and Al-hydroxysulfates, and (4) simple alkaline-earth sulfates such as anhydrite, gypsum, and barite. Generalized assemblages of spatially associated secondary minerals were recognized: (1) alunite+silica±pyrite±kaolinite±gypsum±sulfur, (2) jarosite+alunite+silica; (3) jarosite+smectite+silica±pyrite, (4) Fe- and Al-hydroxysulfates+silica, and (5) simple sulfates+silica±Al-hydroxysulfates±alunite. Isotopic data verify that all sulfate and sulfide minerals and their associated alteration assemblages result largely from the introduction of sulfur-bearing magmatic gases into meteoric water in the upper levels of the volcanoes. The sulfur and oxygen isotopic data for all minerals indicate the general mixing of aqueous sulfate derived from deep (largely disproportionation of SO2 in magmatic vapor) and shallow (oxidation of pyrite or H2S) sources. The hydrogen and oxygen isotopic data of alunite indicate the mixing of magmatic and meteoric fluids. Some alunite-group minerals, along with kaolinite, formed from sulfuric acid created by the disproportionation of SO2 in a condensing magmatic vapor. Such alunite, observed only in those volcanoes whose interiors are exposed by erosion or edifice collapse, may have δ34S values that reflect equilibrium (350±50 °C) between aqueous sulfate and H2S. Alunite with δ34S values indicating disequilibrium between parent aqueous sulfate and H2S may form from aqueous sulfate created in higher level low-temperature environments in which SO2 is scrubbed out by groundwater or where H2S is oxidized. Jarosite-group minerals associated with smectite in only slightly altered volcanic rock are formed largely from aqueous sulfate derived from supergene oxidation of hydrothermal pyrite above the water table. Soluble Al- and Fehydroxysulfates form in low-pH surface environments, especially around fumaroles, and from the oxidation of hydrothermal pyrite. Anhydrite/gypsum, often associated with native sulfur and occasionally with small amounts of barite, also commonly form around fumaroles. Some occurrences of anhydrite/gypsum may be secondary, derived from the dissolution and reprecipitation of soluble sulfate. Edifice collapse may also reveal deep veins of anhydrite/gypsumFbarite that formed from the mixing of saline fluids with magmatic sulfate and dilute meteoric water. Alteration along structures associated with bot

Sour gas hydrothermal jarosite: ancient to modern acid-sulfate mineralization in the southern Rio Grande Rift

As many as 29 mining districts along the Rio Grande Rift in southern New Mexico contain Rio Grande Rift-type (RGR) deposits consisting of fluorite–barite±sulfide–jarosite, and additional RGR deposits occur to the south in the Basin and Range province near Chihuahua, Mexico. Jarosite occurs in many of these deposits as a late-stage hydrothermal mineral coprecipitated with fluorite, or in veinlets that crosscut barite. In these deposits, many of which are limestone-hosted, jarosite is followed by natrojarosite and is nested within silicified or argillized wallrock and a sequence of fluorite–bariteFsulfide and late hematite– gypsum. These deposits range in age from ~10 to 0.4 Ma on the basis of 40Ar/39Ar dating of jarosite. There is a crude north– south distribution of ages, with older deposits concentrated toward the south. Recent deposits also occur in the south, but are confined to the central axis of the rift and are associated with modern geothermal systems. The duration of hydrothermal jarosite mineralization in one of the deposits was approximately 1.0 my. Most Δ18OSO4 –OH values indicate that jarosite precipitated between 80 and 240 °C, which is consistent with the range of filling temperatures of fluid inclusions in late fluorite throughout the rift, and in jarosite (180 °C) from Pen˜a Blanca, Chihuahua, Mexico. These temperatures, along with mineral occurrence, require that the jarosite have had a hydrothermal origin in a shallow steam-heated environment wherein the low pH necessary for the precipitation of jarosite was achieved by the oxidation of H2S derived from deeper hydrothermal fluids. The jarosite also has high trace-element contents (notably As and F), and the jarosite parental fluids have calculated isotopic signatures similar to those of modern geothermal waters along the southern rift; isotopic values range from those typical of meteoric water to those of deep brine that has been shown to form from the dissolution of Permian evaporite by deeply circulating meteoric water. Jarosite δ34S values range from ‒24%◦to 5%◦, overlapping the values for barite and gypsum at the high end of the range and for sulfides at the low end. Most δ34S values for barite are 10.6%◦ to 13.1%◦ , and many δ34S values for gypsum range from 13.1%◦ to 13.9%◦ indicating that a component of aqueous sulfate was derived from Permian evaporites (δ34S=12±2%◦). The requisite H2SO4 for jarosite formation was derived from oxidation of H2S which was likely largely sour gas derived from the thermochemical reduction of Permian sulfate. The low δ34S values for the precursor H2S probably resulted from exchange deeper in the basin with the more abundant Permian SO4 2‒ at ~150 to 200 °C. Jarosite formed at shallow levels after the pH buffering capacity of the host rock (typically limestone) was neutralized by precipitation of earlier minerals. Some limestone-hosted deposits contai

Empowering Youth Through Research: Adolescents’ Perceptions of Physical Activity Interventions in Appalachian Communities

Active participation in evaluation and research projects can empower youth and effect community change. Adolescents along with supervising teachers participating in after-school Health Sciences and Technology Academy clubs conducted research projects to increase physical activity in Appalachian communities. The sample involved 50 adolescents who participated across one of six focus groups. Two primary themes emerged from the focus groups, indicating the impact of the research experiences on students, teachers, and their communities. First, students reported increased public health and research competence as well as feelings of self-worth. Second, the participants reported developing a stronger sense of the barriers to and facilitators of physically active lifestyles relevant in their local communities. This research substantiates the “youth as asset” paradigm and suggests that involving adolescents in community health research benefits both them and their communities

Adolescents and Teachers as Partners in a School-Based Research Project to Increase Physical Activity Opportunities in a Rural Community

Schools are an important resource in combating the physical inactivity and obesity epidemics in rural economically depressed areas. Through a University-community partnership, teachers and adolescents in a rural West Virginia county with one of the highest obesity rates in the state developed a school-based research intervention to increase physical activity opportunities. The intervention included walking routes, educational sessions, and pedometers. A survey about barriers to physical activity revealed that “lack of willpower” was a barrier of concern among program participants (mostly school employees) and had a statistically significant (p = .0033) pre to post mean score decrease during the year two offering. Focus groups with the adolescent researchers revealed that pedometers may facilitate maintenance of physical activity and a broader community impact. Focus group dialogue combined with teacher-researcher perspectives suggested that the adolescents changed their weight control paradigm from “dieting” to include the critical role of energy expenditure. Approval to conduct this research was provided by the West Virginia University Institutional Review Board for the Protection of Human Subjects Protocols No. 16041 and 15632. A poster based on this paper was presented at the 135th Annual Meeting & Exposition of the American Public Health Association, Washington, DC, November, 2007. The authors are very appreciative of the HSTA students for their continued efforts in addressing important public health problems in their community. The project described was supported by funds from the Centers for Disease Control and Prevention (CDC) Grant Award No. H75CCH322130-02 through the West Virginia University Prevention Research Center and by Grant Number 2R25RR12329-04 from the National Center for Research Resources (NCRR), a component of the National Institutes of Health (NIH). Its contents are solely the responsibility of the authors and do not necessarily represent the official views of CDC, NCRR, or NIH

Microbial sulfate reduction and metal attenuation in pH 4 acid mine water

Sediments recovered from the flooded mine workings of the Penn Mine, a Cu-Zn mine abandoned since the early 1960s, were cultured for anaerobic bacteria over a range of pH (4.0 to 7.5). The molecular biology of sediments and cultures was studied to determine whether sulfate-reducing bacteria (SRB) were active in moderately acidic conditions present in the underground mine workings. Here we document multiple, independent analyses and show evidence that sulfate reduction and associated metal attenuation are occurring in the pH-4 mine environment. Waterchemistry analyses of the mine water reveal: (1) preferential complexation and precipitation by H2S of Cu and Cd, relative to Zn; (2) stable isotope ratios of 34S/32S and 18O/16O in dissolved SO4 that are 2–3 ‰ heavier in the mine water, relative to those in surface waters; (3) reduction/oxidation conditions and dissolved gas concentrations consistent with conditions to support anaerobic processes such as sulfate reduction. Scanning electron microscope (SEM) analyses of sediment show 1.5-micrometer, spherical ZnS precipitates. Phospholipid fatty acid (PLFA) and denaturing gradient gel electrophoresis (DGGE) analyses of Penn Mine sediment show a high biomass level with a moderately diverse community structure composed primarily of iron- and sulfate-reducing bacteria. Cultures of sediment from the mine produced dissolved sulfide at pH values near 7 and near 4, forming precipitates of either iron sulfide or elemental sulfur. DGGE coupled with sequence and phylogenetic analysis of 16S rDNA gene segments showed populations of Desulfosporosinus and Desulfitobacterium in Penn Mine sediment and laboratory cultures

Stable Hydrogen Isotope Analysis of Bat Hair as Evidence for Seasonal Molt and Long-Distance Migration

Although hoary bats (Lasiurus cinereus) are presumed to be migratory and capable of long-distance dispersal, traditional marking techniques have failed to provide direct evidence of migratory movements by individuals. We measured the stable hydrogen isotope ratios of bat hair (∂Dh) and determined how these values relate to stable hydrogen isotope ratios of precipitation (∂Dp). Our results indicate that the major assumptions of stable isotope migration studies hold true for hoary bats and that the methodology provides a viable means of determining their migratory movements. We present evidence that a single annual molt occurs in L. cinereus prior to migration and that there is a strong relationship between ∂Dh and ∂Dp during the molt period. This presumably reflects the incorporation of local ∂Dp into newly grown hair. Furthermore, we present evidence that individual hoary bats are capable of traveling distances in excess of 2,000 km and that hair is grown at a wide range of latitudes and elevations. Stable hydrogen isotope analysis offers a promising new tool for the study of bat migration