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Sample records for culebra dolomite member

  1. Mineralogy of the Culebra Dolomite Member of the Rustler Formation

    Energy Technology Data Exchange (ETDEWEB)

    Sewards, T.; Williams, M.L.; Keil, K. (New Mexico Univ., Albuquerque, NM (USA))

    1991-03-01

    This report characterizes the mineralogy of the Culebra Member of the Rustler Formation based on studies of samples from cores of eight boreholes surrounding the WIPP repository. This investigation has three main goals: to obtain accurate modal compositions of all the samples selected; to investigate both the lateral and vertical variation of the mineralogy of the Culebra unit; and, to characterize water-bearing fracture surfaces in particular detail. The Culebra Dolomite member of the Rustler Formation is mineralogically and texturally heterogeneous, both vertically and horizontally. Although the predominant mineral is dolomite, important constituents of the formation are clay, quartz, gypsum, and calcite. Trace minerals include halite, phyllosilicates of metamorphic origin, feldspar, and pyrite. 24 refs., 90 figs., 27 tabs.

  2. Conceptual model for transport processes in the Culebra Dolomite Member, Rustler Formation

    Energy Technology Data Exchange (ETDEWEB)

    Holt, R.M. [Holt Hydrogeology, Placitas, NM (United States)

    1997-08-01

    The Culebra Dolomite Member of the Rustler Formation represents a possible pathway for contaminants from the Waste Isolation Pilot Plant underground repository to the accessible environment. The geologic character of the Culebra is consistent with a double-porosity, multiple-rate model for transport in which the medium is conceptualized as consisting of advective porosity, where solutes are carried by the groundwater flow, and fracture-bounded zones of diffusive porosity, where solutes move through slow advection or diffusion. As the advective travel length or travel time increases, the nature of transport within a double-porosity medium changes. This behavior is important for chemical sorption, because the specific surface area per unit mass of the diffusive porosity is much greater than in the advective porosity. Culebra transport experiments conducted at two different length scales show behavior consistent with a multiple-rate, double-porosity conceptual model for Culebra transport. Tracer tests conducted on intact core samples from the Culebra show no evidence of significant diffusion, suggesting that at the core scale the Culebra can be modeled as a single-porosity medium where only the advective porosity participates in transport. Field tracer tests conducted in the Culebra show strong double-porosity behavior that is best explained using a multiple-rate model.

  3. Laboratory column experiments for radionuclide adsorption studies of the Culebra dolomite member of the Rustler Formation

    Energy Technology Data Exchange (ETDEWEB)

    Lucero, D.A.; Heath, C.E. [Sandia National Labs., Albuquerque, NM (United States); Brown, G.O. [Oklahoma State Univ., Stillwater, OK (United States). Biosystems and Agricultural Engineering Dept.

    1998-04-01

    Radionuclide transport experiments were carried out using intact cores obtained from the Culebra member of the Rustler Formation inside the Waste Isolation Pilot Plant, Air Intake Shaft. Twenty-seven separate tests are reported here and include experiments with {sup 3}H, {sup 22}Na, {sup 241}Am, {sup 239}Np, {sup 228}Th, {sup 232}U and {sup 241}Pu, and two brine types, AIS and ERDA 6. The {sup 3}H was bound as water and provides a measure of advection, dispersion, and water self-diffusion. The other tracers were injected as dissolved ions at concentrations below solubility limits, except for americium. The objective of the intact rock column flow experiments is to demonstrate and quantify transport retardation coefficients, (R) for the actinides Pu, Am, U, Th and Np, in intact core samples of the Culebra Dolomite. The measured R values are used to estimate partition coefficients, (kd) for the solute species. Those kd values may be compared to values obtained from empirical and mechanistic adsorption batch experiments, to provide predictions of actinide retardation in the Culebra. Three parameters that may influence actinide R values were varied in the experiments; core, brine and flow rate. Testing five separate core samples from four different core borings provided an indication of sample variability. While most testing was performed with Culebra brine, limited tests were carried out with a Salado brine to evaluate the effect of intrusion of those lower waters. Varying flow rate provided an indication of rate dependent solute interactions such as sorption kinetics.

  4. Interpretations of Tracer Tests Performed in the Culebra Dolomite at the Waste Isolation Pilot Plant Site

    Energy Technology Data Exchange (ETDEWEB)

    MEIGS,LUCY C.; BEAUHEIM,RICHARD L.; JONES,TOYA L.

    2000-08-01

    This report provides (1) an overview of all tracer testing conducted in the Culebra Dolomite Member of the Rustler Formation at the Waste Isolation Pilot Plant (WPP) site, (2) a detailed description of the important information about the 1995-96 tracer tests and the current interpretations of the data, and (3) a summary of the knowledge gained to date through tracer testing in the Culebra. Tracer tests have been used to identify transport processes occurring within the Culebra and quantify relevant parameters for use in performance assessment of the WIPP. The data, especially those from the tests performed in 1995-96, provide valuable insight into transport processes within the Culebra. Interpretations of the tracer tests in combination with geologic information, hydraulic-test information, and laboratory studies have resulted in a greatly improved conceptual model of transport processes within the Culebra. At locations where the transmissivity of the Culebra is low (< 4 x 10{sup -6} m{sup 2}/s), we conceptualize the Culebra as a single-porosity medium in which advection occurs largely through the primary porosity of the dolomite matrix. At locations where the transmissivity of the Culebra is high (> 4 x 10{sup -6} m{sup 2}/s), we conceptualize the Culebra as a heterogeneous, layered, fractured medium in which advection occurs largely through fractures and solutes diffuse between fractures and matrix at multiple rates. The variations in diffusion rate can be attributed to both variations in fracture spacing (or the spacing of advective pathways) and matrix heterogeneity. Flow and transport appear to be concentrated in the lower Culebra. At all locations, diffusion is the dominant transport process in the portions of the matrix that tracer does not access by flow.

  5. Ground-water flow modeling of the Culebra dolomite

    Energy Technology Data Exchange (ETDEWEB)

    LaVenue, A.M.; Cauffman, T.L.; Pickens, J.F. (INTERA, Inc., Austin, TX (USA))

    1990-10-01

    This hydrogeologic modeling study has been performed as part of the regional hydrologic characterization of the Waste Isolation Pilot Plant (WIPP) site in southeastern New Mexico. The study has produced an estimation of the transmissivity and Darcy-velocity distributions in the Culebra Dolomite Member of the Permian Rustler Formation at the WIPP site. The results of this study are intended to support Sandia National Laboratories performance-assessment calculations. The three-dimensional finite-difference code SWIFT II was employed for the numerical modeling, using a variable-fluid-density and single-porosity formulation. The spatial scale of the model, 21.3 km by 30.6 km, was chosen to allow simulation of regional-scale pumping tests conducted at the H-3 and H-11 hydropads and the WIPP-13 borehole, which are located south, southeast, and northwest, respectively, of the center of the WIPP site. The modeled area includes and extends beyond the controlled area defined by the WIPP-site boundaries. The work performed in this study consisted of modeling the hydrogeology of the Culebra in two stages: steady-state modeling to develop the best estimate of the undisturbed head distribution (i.e., of the hydraulic conditions before excavation of the WIPP shafts, which began in 1981) and superimposed transient modeling of local hydrologic response to excavation of the four WIPP shafts at the center of the WIPP site, as well as to various well tests. The transient modeling used the calculated steady-state freshwater heads as initial conditions. 144 refs., 98 figs., 23 tabs.

  6. Core analyses for selected samples from the Culebra Dolomite at the Waste Isolation Pilot Plant site

    Energy Technology Data Exchange (ETDEWEB)

    Kelley, V.A.; Saulnier, G.J. Jr. (INTERA, Inc., Austin, TX (USA))

    1990-11-01

    Two groups of core samples from the Culebra Dolomite Member of the Rustler Formation at and near the Waste Isolation Pilot Plant were analyzed to provide estimates of hydrologic parameters for use in flow-and-transport modeling. Whole-core and core-plug samples were analyzed by helium porosimetry, resaturation and porosimetry, mercury-intrusion porosimetry, electrical-resistivity techniques, and gas-permeability methods. 33 refs., 25 figs., 10 tabs.

  7. Core analyses for selected samples from the Culebra Dolomite at the Waste Isolation Pilot Plant site

    Energy Technology Data Exchange (ETDEWEB)

    Kelley, V.A.; Saulnier, G.J. Jr. (INTERA, Inc., Austin, TX (USA))

    1990-11-01

    Two groups of core samples from the Culebra Dolomite Member of the Rustler Formation at and near the Waste Isolation Pilot Plant were analyzed to provide estimates of hydrologic parameters for use in flow-and-transport modeling. Whole-core and core-plug samples were analyzed by helium porosimetry, resaturation and porosimetry, mercury-intrusion porosimetry, electrical-resistivity techniques, and gas-permeability methods. 33 refs., 25 figs., 10 tabs.

  8. Geochemical evolution of groundwater in the Culebra dolomite near the Waste Isolation Pilot Plant, southeastern New Mexico, USA

    Science.gov (United States)

    Siegel, M.D.; Anderholm, S.

    1994-01-01

    The Culebra Dolomite Member of the Rustler Formation, a thin (10 m) fractured dolomite aquifer, lies approximately 450 m above the repository horizon of the Waste Isolation Pilot Plant (WIPP) in southeastern New Mexico, USA. Salinities of water in the Culebra range roughly from 10,000 to 200,000 mg/L within the WIPP site. A proposed model for the post-Pleistocene hydrochemical evolution of the Culebra tentatively identifies the major sources and sinks for many of the groundwater solutes. Reaction-path simulations with the PHRQPITZ code suggest that the Culebra dolomite is a partial chemical equilibrium system whose composition is controlled by an irreversible process (dissolution of evaporites) and equilibrium with gypsum and calcite. Net geochemical reactions along postulated modern flow paths, calculated with the NETPATH code, include dissolution of halite, carbonate and evaporite salts, and ion exchange. R-mode principal component analysis revealed correlations among the concentrations of Si, Mg, pH, Li, and B that are consistent with several clay-water reactions. The results of the geochemical calculations and mineralogical data are consistent with the following hydrochemical model: 1. (1) solutes are added to the Culebra by dissolution of evaporite minerals 2. (2) the solubilities of gypsum and calcite increase as the salinity increases; these minerals dissolve as chemical equilibrium is maintained between them and the groundwater 3. (3) equilibrium is not maintained between the waters and dolomite; sufficient Mg is added to the waters by dissolution of accessory carnallite or polyhalite such that the degree of dolomite supersaturation increases with ionic strength 4. (4) clays within the fractures and rock matrix exert some control on the distribution of Li, B, Mg, and Si via sorption, ion exchange, and dissolution. ?? 1994.

  9. Krypton-81 in groundwater of the Culebra Dolomite near the Waste Isolation Pilot Plant, New Mexico.

    Science.gov (United States)

    Sturchio, Neil C; Kuhlman, Kristopher L; Yokochi, Reika; Probst, Peter C; Jiang, Wei; Lu, Zheng-Tian; Mueller, Peter; Yang, Guo-Min

    2014-05-01

    The Waste Isolation Pilot Plant (WIPP) in New Mexico is the first geologic repository for disposal of transuranic nuclear waste from defense-related programs of the US Department of Energy. It is constructed within halite beds of the Permian-age Salado Formation. The Culebra Dolomite, confined within Rustler Formation evaporites overlying the Salado Formation, is a potential pathway for radionuclide transport from the repository to the accessible environment in the human-disturbed repository scenario. Although extensive subsurface characterization and numerical flow modeling of groundwater has been done in the vicinity of the WIPP, few studies have used natural isotopic tracers to validate the flow models and to better understand solute transport at this site. The advent of Atom-Trap Trace Analysis (ATTA) has enabled routine measurement of cosmogenic (81)Kr (half-life 229,000 yr), a near-ideal tracer for long-term groundwater transport. We measured (81)Kr in saline groundwater sampled from two Culebra Dolomite monitoring wells near the WIPP site, and compared (81)Kr model ages with reverse particle-tracking results of well-calibrated flow models. The (81)Kr model ages are ~130,000 and ~330,000 yr for high-transmissivity and low-transmissivity portions of the formation, respectively. Compared with flow model results which indicate a relatively young mean hydraulic age (~32,000 yr), the (81)Kr model ages imply substantial physical attenuation of conservative solutes in the Culebra Dolomite and provide limits on the effective diffusivity of contaminants into the confining aquitards.

  10. Analysis of hydraulic tests of the Culebra and Magenta Dolomites and Dewey Lake Redbeds conducted at the Waste Isolation Pilot Plant Site

    Energy Technology Data Exchange (ETDEWEB)

    Beauheim, R.L. [Sandia National Labs., Albuquerque, NM (United States). Geohydrology Dept.; Ruskauff, G.J. [Duke Engineering and Services, Inc., Albuquerque, NM (United States)

    1998-09-01

    This report presents interpretations of hydraulic tests conducted at 15 well locations in the vicinity of the Waste Isolation Pilot Plant (WIPP) in southeastern New Mexico between 1980 and 1996. The WIPP is a US Department of Energy (DOE) facility to demonstrate safe disposal of transuranic wastes arising form the nation`s defense programs. The WIPP repository lies within bedded halite of the Salado Formation, 2,155 ft below ground surface. The tests reported herein were, with two exceptions, conducted in the Culebra Dolomite member of the Rustler Formation, which overlies the Salado Formation. The remaining tests were conducted in the Magenta Member of the Rustler and in the overlying formation, the Dewey Lake Redbeds. This report completes the documentation of hydraulic-test interpretations used as input to the WIPP Compliance Certification Application (US DOE, 1996).

  11. Interpretation of actinide-distribution data obtained from non-destructive and destructive post-test analyses of an intact-core column of Culebra dolomite.

    Science.gov (United States)

    Perkins, W G; Lucero, D A

    2001-02-01

    The US Department of Energy (DOE), with technical assistance from Sandia National Laboratories, has successfully received EPA certification and opened the Waste Isolation Pilot Plant (WIPP), a nuclear waste disposal facility located approximately 42 km east of Carlsbad, NM. Performance assessment (PA) analyses indicate that human intrusions by inadvertent, intermittent drilling for resources provide the only credible mechanisms for significant releases of radionuclides from the disposal system. For long-term brine releases, migration pathways through the permeable layers of rock above the Salado formation are important. Major emphasis is placed on the Culebra Member of the Rustler Formation because this is the most transmissive geologic layer overlying the WIPP site. In order to help quantify parameters for the calculated releases, radionuclide transport experiments have been carried out using intact-core columns obtained from the Culebra dolomite member of the Rustler Formation within the WIPP site. This paper deals primarily with results of analyses for 241Pu and 241Am distributions developed during transport experiments in one of these cores. Transport experiments were done using a synthetic brine that simulates Culebra brine at the core recovery location (the WIPP air-intake shaft (AIS)). Hydraulic characteristics (i.e., apparent porosity and apparent dispersion coefficient) for intact-core columns were obtained via experiments using the conservative tracer 22Na. Elution experiments carried out over periods of a few days with tracers 232U and 239Np indicated that these tracers were weakly retarded as indicated by delayed elution of the species. Elution experiments with tracers 241Pu and 241Am were attempted but no elution of either species has been observed to date, including experiments of many months' duration. In order to quantify retardation of the non-eluted species 241Pu and 241Am after a period of brine flow, non-destructive and destructive analyses of

  12. Interpretation of data obtained from non-destructive and destructive post-test analyses of an intact-core column of culebra dolomite

    Energy Technology Data Exchange (ETDEWEB)

    Lucero, Daniel L.; Perkins, W. George

    1998-09-01

    The U.S. Department of Energy (DOE) has been developing a nuclear waste disposal facility, the Waste Isolation Pilot Plant (WIPP), located approximately 42 km east of Carlsbad, New Mexico. The WIPP is designed to demonstrate the safe disposal of transuranic wastes produced by the defense nuclear-weapons program. Pefiormance assessment analyses (U.S. DOE, 1996) indicate that human intrusion by inadvertent and intermittent drilling for resources provide the only credible mechanisms for significant releases of radionuclides horn the disposal system. These releases may occur by five mechanisms: (1) cuttings, (2) cavings, (3) spallings, (4) direct brine releases, and (5) long- term brine releases. The first four mechanisms could result in immediate release of contaminant to the accessible environment. For the last mechanisq migration pathways through the permeable layers of rock above the Salado are important, and major emphasis is placed on the Culebra Member of the Rustler Formation because this is the most transmissive geologic layer in the disposal system. For reasons of initial quantity, half-life, and specific radioactivity, certain isotopes of T~ U, Am, and Pu would dominate calculated releases from the WIPP. In order to help quantifi parameters for the calculated releases, radionuclide transport experiments have been carried out using five intact-core columns obtained from the Culebra dolomite member of the Rustler Formation within the Waste Isolation Pilot Pknt (WIPP) site in southeastern New Mexico. This report deals primarily with results of analyses for 241Pu and 241Am distributions developed during transport experiments in one of these cores. All intact-core column transport experiments were done using Culebra-simukmt brine relevant to the core recovery location (the WIPP air-intake shaft - AK). Hydraulic characteristics (i.e., apparent porosity and apparent dispersion coefficient) for intact-core columns were obtained via experiments using conservative

  13. Radionuclide and colloid transport in the Culebra Dolomite and associated complementary cumulative distribution functions in the 1996 performance assessment for the Waste Isolation Pilot Plant

    Energy Technology Data Exchange (ETDEWEB)

    RAMSEY, JAMES L.; BLAINE,R.; GARNER,J.W.; HELTON,JON CRAIG; JOHNSON,J.D.; SMITH,L.N.; WALLACE,M.

    2000-05-22

    The following topics related to radionuclide and colloid transport in the Culebra Dolomite in the 1996 performance assessment for the Waste Isolation Pilot Plant (WIPP) are presented: (1) mathematical description of models, (2) uncertainty and sensitivity analysis results arising from subjective (i.e., epistemic) uncertainty for individual releases, and (3) construction of complementary cumulative distribution functions (CCDFs) arising from stochastic (i.e., aleatory) uncertainty. The presented results indicate that radionuclide and colloid transport in the Culebra Dolomite does not constitute a serious threat to the effectiveness of the WIPP as a disposal facility for transuranic waste. Even when the effects of uncertain analysis inputs are taken into account, no radionuclide transport to the boundary with the accessible environment was observed; thus the associated CCDFs for comparison with the boundary line specified in the US Environmental Protection Agency's standard for the geologic disposal of radioactive waste (40 CFR 191, 40 CFR 194) are degenerate in the sense of having a probability of zero of exceeding a release of zero.

  14. Hydrostatic pressure and fluid-density distribution of the Culebra Dolomite member of the Rustler Formation near the Waste Isolation Pilot Plant, southeastern New Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Crawley, M.E.

    1988-05-01

    The primary objectives of the Pressure - Density Survey were to obtain the middle-of-formation pressures, determine well-bore fluid densities, define well-bore fluid density stratification, and to provide, where possible, formation water density values for wells where little or no information on densities exists. The survey collected ground-water pressure and density data during three field testing periods during the years 1986 and 1987. Data were collected from 33 individual wells located in the vicinity of the WIPP Site. 18 refs., 10 figs., 10 tabs.

  15. Culebra National Wildlife Refuge: Comprehensive Conservation Plan

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This Comprehensive Conservation Plan (CCP) was written to guide management on Culebra NWR for the next 15 years. This plan outlines the Refuge vision and purpose and...

  16. Dolomitization and Uniformitarianism

    Science.gov (United States)

    Zenger, Donald H.

    1972-01-01

    Reviews research of the past 15 years related to the occurrence of stratigraphic dolomite, confronting especially the main dolomite issue - the discrepancy between the amount of modern and ancient dolomite. (PR)

  17. Fundamentals of Sintering Dolomite

    Institute of Scientific and Technical Information of China (English)

    LIMaoqiang

    1996-01-01

    The difficulties in sintering of dolomite rise form the low mutual diffusibilites of Ca2+ in MgO and Mg2+ in CaO ,and from unique pore and agglomerate structures formed after calcination of dolomite.These microstructures in decompsoed dolomite play a great role in inhibition of densification during sintering.The measures ,which can destroy these stuctures,such as hydration or isostatic pressing after calcination of dolomite,result in increasing the sintered density and reducting the sintering temperature,Addition of ome oxide such as Fe2O3,ater the sintering mechanism from solid state sintering to liquid phase sintering,therefore,dense dolomite ody can be obtained at relatively low sintering temperature,Com-minution of dolomite before its calcination can lower the sintering temperature and enhance the sinterd ensity due to increasing both the quantity and homogeneity of Fe2O3 in dolomite.

  18. Northeast Puerto Rico and Culebra Island Accuracy Assessment Points - 2015

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This shapefile denotes the location of underwater photos and videos taken in shallow water (0-35m) benthic habitats surrounding Northeast Puerto Rico and Culebra...

  19. Northeast Puerto Rico and Culebra Island Ground Validation Points 2015

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This shapefile denotes the location of underwater photos and videos taken in shallow water (0-35m) benthic habitats surrounding Northeast Puerto Rico and Culebra...

  20. ORIGIN OF DOLOMITE IN THE SECOND MEMBER OF JIANLINGJIANG FORMATION OF LOWER TRIASSIC,SOUTHWESTERN HUBEI PROVINCE,CHINA%鄂西南下三叠统嘉陵江组二段白云岩化机制

    Institute of Scientific and Technical Information of China (English)

    胡广成; 鲍志东

    2011-01-01

    The Jialingjiang Formation of Lower Triassic in the southwestern Hubei Province consists primarily of carbonate rocks characterized by limestone interbedded with dolomite. According to field outcrop investigation and laboratory analysis,the dolomite has been divided into micritic dolomite and doloarenite respectively. Based on the study of petrological characteristics, combined with the research of cathodoluminescence and geochemical properties of trace elements, carbon and oxygen isotopes, the genesis of dolomitization in the Jialingjiang Formation is thoroughly investigated. It is considered that the genesis of micritic dolomite is related to penecontem-poraneous dolomitization characterized by birdseyes,fenestral fabrics,gypsum pseudomorph,lower ordering degree and red or purplish red cathodeluminescence. While the genesis of doloarenite is related to mixed water dolomitization characterized by higher ordering degree,lower value of Na and Mn/Sr,higher value of Mn and Fe,relatively negative δ18O value,positive δ13C value and purplish red cathodeluminescence. Meanwhile, the abnormity of Sr reveals that burial dolomitization is the succession of mixed water dolomitization,and the dolomitizing fluids come from the Mg2+-riched brine of micritic dolomite.%鄂西南恩施地区下三叠统嘉陵江组为碳酸盐岩沉积,发育石灰岩与白云岩的互层,通过野外观察和室内分析表明,嘉二段主要发育两种类型的白云岩,即泥晶-粉晶白云岩和砂屑白云岩.在沉积环境和岩石学特征研究的基础上,结合微量元素、碳氧同位素和阴极发光等技术,对白云岩的形成机理进行了分析.泥晶-粉晶白云岩发育有鸟眼构造、窗格构造和石膏假晶等暴露沉积特征,有序度低,白云石发红色光、紫红色光,与准同生白云岩化作用有关;砂屑白云岩有序度高、Mn和Fe含量高、Na含量和Mn/Sr小,具有较负的δ18O值和较正的δ13C值,形成于受大气淡水影响的氧

  1. Geology of the Dolomites

    Institute of Scientific and Technical Information of China (English)

    AlfonsoBosellini; PieroGianolla; MarcoStefani

    2003-01-01

    The Dolomites region is a spectacularly exposed portion of the Southern Alps, a northern Italian chain derived from the comparatively gentle deformation of the Tethyan passive continental margin of Adria. The regionhad an active Permo-Jurassic tectono-magmatic evolu-tion, leading from Permian magmatism, through a Mid-die Triassic episode offast subsidence and volcanism, to the Jurassic oceanic break-up. Although the sedimentary succession ranges in age from Middle Permian to Creta-ceous, the geological landscape is largely dominated by the majestic Triassic carbonates, making the area a clas-sical one for the early Mesozoic stratigraphy. Particu-larly noteworthy are the Anisian to Carnian carbonate platforms, recording an evolution from regional muddy banks to isolated high-relief builduos. The hlline of the various basins and the development of a last generation of regional peritidal platform followed. The carbonate platforms of the Dolomites bear witness to a remarkable set of changes in the carbonate production and to signif-icant palaeoclimatic fluctuations,from arid to moist con-difions and vice versa; a great range of margin and slope depositional styles is therefore recorded. Alpine tectonic shortening strongly affected the area, with a first Eocenede formation, followed by later Neogene overthrusting and strike-slip movements.

  2. Entre historias y culebras: más que una bahía (Bahía Culebra, Guanacaste, Costa Rica Among stories and snakes: more than a bay (Bahía Culebra, Guanacaste, Costa Rica

    Directory of Open Access Journals (Sweden)

    Celeste Sánchez-Noguera

    2012-04-01

    Full Text Available Bahía Culebra (Golfo de Papagayo, Guanacaste, Costa Rica es una unidad geomorfológica semicerrada y bastante protegida, que cuenta con una amplia diversidad de recursos naturales, favoreciendo el asentamiento de poblaciones humanas y su consecuente desarrollo marinocostero. La reseña histórica de Bahía Culebra indica que este ha sido un sitio muy importante desde la perspectiva histórica, política, cultural y económica. La consulta bibliográfica incluyó documentos que datan de mediados del siglo XIX hasta el año 2011, los cuales fueron recopilados del Archivo Nacional de Costa Rica, la Biblioteca Nacional, el Centro de Documentación del Centro de Investigaciones Históricas de América Central y algunas colecciones privadas. Su notoria belleza escénica, la disponibilidad de redes viales en buen estado y la cercanía a un aeropuerto internacional han facilitado que la bahía se convierta en un centro turístico intensivo, generando un acelerado desarrollo costero a raíz de la creación del proyecto Polo Turístico Golfo de Papagayo (PTGP. Se debe fortalecer el marco jurídico e implementar acciones que promuevan el bienestar de las poblaciones locales y la adecuada gestión de los recursos naturales, tomando en cuenta todos los factores y actores involucrados.Among stories and snakes: more than a bay (Bahía Culebra, Guanacaste, Costa Rica. Bahía Culebra (Culebra Bay is a semi-closed and protected geomorphological unit, which has a wide diversity of natural resources, encouraging the settlement of human populations and consequent coastal development. Bahía Culebra has been an important place from the historical, political, cultural and economic perspective, according to the literature search which included documents dating from the mid nineteenth century until 2011, from the National Archive of Costa Rica, the National Library, the Historical Research Center in Central America and some private collections. Its beauty, road

  3. 33 CFR 334.1460 - Atlantic Ocean and Vieques Sound, in vicinity of Culebra Island; bombing and gunnery target area.

    Science.gov (United States)

    2010-07-01

    ..., in vicinity of Culebra Island; bombing and gunnery target area. 334.1460 Section 334.1460 Navigation...; bombing and gunnery target area. (a) The danger zone. From Punta Resaca on the north coast of Culebra at... danger zone is subject to use as a target area for bombing and gunnery practice. It will be open to...

  4. Plant Life of the Dolomites

    Directory of Open Access Journals (Sweden)

    Rob Brooker

    2015-02-01

    Full Text Available Reviewed: Plant Life of the Dolomites. By Erika Pignatti and Sandro Pignatti. Heidelberg, Germany: Springer, 2014. xxxvii + 769 pp. US$ 209.00, £ 135.00, J 149.95. Also available as an e-book. ISBN 978-3-642-31042-3.

  5. Thermal decomposition of natural dolomite

    Indian Academy of Sciences (India)

    S Gunasekaran; G Anbalagan

    2007-08-01

    Thermal decomposition behaviour of dolomite sample has been studied by thermogravimetric (TG) measurements. Differential thermal analysis (DTA) curve of dolomite shows two peaks at 777.8°C and 834°C. The two endothermic peaks observed in dolomite are essentially due to decarbonation of dolomite and calcite, respectively. The TG data of the decomposition steps have also been analysed using various differential, difference-differential and integral methods, viz. Freeman–Carroll, Horowitz–Metzger, Coats–Redfern methods. Values of activation entropy, Arrhenius factor, and order of reaction have been approximated and compared. Measured activation energies vary between 97 and 147 kJ mol-1. The large fluctuation in activation energy is attributed to the presence of impurities such as SiO2, Al2O3, Fe2O3, Cl- etc in the samples. FTIR and XRD analyses confirm the decomposition reaction. SEM observation of the heat-treated samples at 950°C shows cluster of grains, indicating the structural transformation.

  6. Efluent treatment with dolomite mining

    OpenAIRE

    Romero Baylón, Alfonso; UNMSM; Flores Chávez, Silvana; UNMSM; Arévalo, Walter; UNMSM

    2014-01-01

    The article shows a methodology for acid water treatment, through the remediation of effluents from the mining industry, based on the use of treated dolomite, which reduces the concentrations of dissolved heavy metal ions in metallurgical and mining effluent to reducing high levels of heavy metals, which are indicators of improved water quality of industrial wastes, mainly from metallurgical processes concentrator plants. This treatment technique solves the problem of effluent generation with...

  7. Enrico Fermi and the Dolomites

    Energy Technology Data Exchange (ETDEWEB)

    Battimelli, Giovanni, E-mail: giovanni.battimelli@uniroma1.it; Angelis, Alessandro de, E-mail: alessandro.de.angelis@cern.ch

    2014-11-15

    Summer vacations in the Dolomites were a tradition among the professors of the Faculty of Mathematical and Physical Sciences at the University of Roma since the end of the XIX century. Beyond the academic walls, people like Tullio Levi-Civita, Federigo Enriques and Ugo Amaldi sr., together with their families, were meeting friends and colleagues in Cortina, San Vito, Dobbiaco, Vigo di Fassa and Selva, enjoying trekking together with scientific discussions. The tradition was transmitted to the next generations, in particular in the first half of the XX century, and the group of via Panisperna was directly connected: Edoardo Amaldi, the son of the mathematician Ugo sr., rented at least during two summers, in 1925 and in 1949, and in the winter of 1960, a house in San Vito di Cadore, and almost every year in the Dolomites; Enrico Fermi was a frequent guest. Many important steps in modern physics, in particular the development of the Fermi-Dirac statistics and the Fermi theory of beta decay, are related to scientific discussions held in the region of the Dolomites.

  8. Enrico Fermi and the Dolomites

    Science.gov (United States)

    Battimelli, Giovanni; de Angelis, Alessandro

    2014-11-01

    Summer vacations in the Dolomites were a tradition among the professors of the Faculty of Mathematical and Physical Sciences at the University of Roma since the end of the XIX century. Beyond the academic walls, people like Tullio Levi-Civita, Federigo Enriques and Ugo Amaldi sr., together with their families, were meeting friends and colleagues in Cortina, San Vito, Dobbiaco, Vigo di Fassa and Selva, enjoying trekking together with scientific discussions. The tradition was transmitted to the next generations, in particular in the first half of the XX century, and the group of via Panisperna was directly connected: Edoardo Amaldi, the son of the mathematician Ugo sr., rented at least during two summers, in 1925 and in 1949, and in the winter of 1960, a house in San Vito di Cadore, and almost every year in the Dolomites; Enrico Fermi was a frequent guest. Many important steps in modern physics, in particular the development of the Fermi-Dirac statistics and the Fermi theory of beta decay, are related to scientific discussions held in the region of the Dolomites.

  9. 77 FR 40895 - Culebra National Wildlife Refuge, PR; Draft Comprehensive Conservation Plan and Environmental...

    Science.gov (United States)

    2012-07-11

    ... boundary verification; and (9) developing renewable energy projects. CCP Alternatives, Including Our... cooperation with partners, we would also continue surveys and protection of nesting hawksbill, green, and... ] resources on offshore cays and conduct limited invasive species removal. Culebra NWR would maintain its...

  10. Mineralogical correlation between primary and replacement dolomites

    Institute of Scientific and Technical Information of China (English)

    黄志诚; 杨守业; 陈智娜

    1997-01-01

    Primary dolostones occur in the Upper Sinian Dengying Formation. Based on mineralogieal study the indicators for correlation between the primary dolomites which are not influenced by the diagenesis and the replacement dolomites of different periods have been obtained. It is shown that the primary dolomites are characterized by crystal forms precipitated and deposited directly from sea water, stable and homogeneous distribution of Mg and Ca, ideal chemical composition, regular modulated microstructures, low positive δ13C and low negative δ18O.

  11. Proposal - Herpetofaunal inventory and occurrence species mapping in the Culebra National Wildlife Refuge’s offshore cays.

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This proposal is designed to address the inventory of herpetofauna on the 12 cays of Culebra NWR and determine if the Virgin Island tree boa or the giant anole are...

  12. Bibliografia sobre organismos, ambientes y procesos marinos y atmosfericos en Bahia Culebra, Pacifico norte, Guanacaste, Costa Rica

    National Research Council Canada - National Science Library

    Cortes, Jorge

    2012-01-01

    .... En este trabajo compilo y analizo una lista de 182 publicaciones en revista cientifcas y 23 tesis, informes y libros sobre organismos, ambientes y procesos marinos y atmosfericos en Bahia Culebra...

  13. Interim Report -Herpetofaunal inventory and occurrence species mapping in the Culebra National Wildlife Refuge’s offshore cays.

    Data.gov (United States)

    US Fish and Wildlife Service, Department of the Interior — This proposal is designed to address the inventory of herpetofauna on the 12 cays of Culebra NWR and determine if the Virgin Island tree boa or the giant anole are...

  14. Enrico Fermi and the Dolomites

    CERN Document Server

    Battimelli, Giovanni

    2014-01-01

    Summer vacations in the Dolomites were a tradition among the professors of the Faculty of Mathematical and Physical Sciences at the University of Roma since the end of the XIX century. Beyond the academic walls, people like Tullio Levi-Civita, Federigo Enriques and Ugo Amaldi sr., together with their families, were meeting friends and colleagues in Cortina, San Vito, Dobbiaco, Vigo di Fassa and Selva, enjoying trekking together with scientific discussions. The tradition was transmitted to the next generations, in particular in the first half of the XX century, and the group of via Panisperna was directly connected: Edoardo Amaldi, the son of the mathematician Ugo sr., rented at least during two summers, in 1925 and in 1949, and in the winter of 1960, a house in San Vito di Cadore, and almost every year in the Dolomites; Enrico Fermi was a frequent guest. Many important steps in modern physics, in particular the development of the Fermi-Dirac statistics and the Fermi theory of beta decay, are related to scient...

  15. Ab Initio Study of the Structure and Stability of High-Pressure Iron-Bearing Dolomite

    Science.gov (United States)

    Solomatova, N. V.; Asimow, P. D.

    2016-12-01

    Carbon is subducted into the mantle primarily in the form of metasomatically calcium-enriched basaltic rock, calcified serpentinites and carbonaceous ooze, all of which often contain dolomite. End-member CaMg(CO3)2 dolomite typically breaks down upon compression into two carbonates at 5-6 GPa in the temperature range of 800-1200 K [1]. However, high-pressure X-ray diffraction experiments have recently shown that the presence of iron may be sufficient to stabilize high-pressure dolomite over single-cation carbonates above 35 GPa [2,3]. The structure and equation of state of high-pressure dolomite phases have been debated, creating a need for theoretical calculations. Using density functional theory interfaced with a genetic algorithm that predicts crystal structures (USPEX), we have found a monoclinic phase with space group C2/c. The C2/c structure has a lower energy than previously reported dolomite structures at relevant pressures. It is possible that this phase is not achieved experimentally due to a large energy barrier and a correspondingly large required volume drop, resulting in the transformation to metastable dolomite II. We calculate the equation of state of trigonal dolomite, dolomite III and monoclinic C2/c dolomite to 80 GPa with 0 and 50 mol% CaFe(CO3)2 and compare their enthalpies to single-carbonate assemblages. Although end-member C2/c CaMg(CO3)2 dolomite is not stable relative to single-cation carbonates, C2/c CaMg0.5Fe0.5(CO3)2 is preferred over single-cation carbonates at high pressures. Thus, iron-bearing C2/c dolomite may be an important host phase for carbon in slabs subducted into the lower mantle. [1] Shirasaka, M., et al. (2002) American Mineralogist, 87, 922-930. [2] Mao, Z. et al. (2011) Geophysical Research Letters, 38. [3] Merlini, M. et al. (2012) Proceedings of the National Academy of Sciences, 109, 13509-13514.

  16. First description of Phanerozoic radiaxial fibrous dolomite

    Science.gov (United States)

    Richter, D. K.; Heinrich, F.; Geske, A.; Neuser, R. D.; Gies, H.; Immenhauser, A.

    2014-05-01

    The petrographic analysis and crystallographic analysis of concretionary carbonate cements ("coal balls") from Carboniferous paralic swamp deposits reveal the presence of (length fast) radiaxial fibrous dolomite (RFD), a fabric not previously reported from the Phanerozoic. This finding is of significance as earlier reports of Phanerozoic radiaxial fibrous carbonates are exclusively of calcite mineralogy. Dolomite concretions described here formed beneath marine transgressive intervals within palustrine coal seams. This is of significance as seawater was arguably the main source of Mg2 + ions for dolomite formation. Here, data from optical microscopy, cathodoluminescence, electron backscattered diffraction, X-ray diffraction and geochemical analyses are presented to characterize three paragenetic dolomite phases and one calcite phase in these concretions. The main focus is on the earliest diagenetic, non-stoichiometric (degree of order: 0.41-0.46) phase I, characterized by botryoidal dolomite constructed of fibres up to 110 μm wide with a systematic undulatory extinction and converging crystal axes. Petrographic and crystallographic evidence clearly qualifies phase I dolomite as radiaxial fibrous. Conversely, fascicular optical fabrics were not found. Carbon-isotope ratios (δ13C) are depleted (between - 11.8 and - 22.1‰) as expected for carbonate precipitation from marine pore-fluids in organic-matter-rich, paralic sediment. Oxygen isotope (δ18O) ratios range between - 1.3 and - 6.0‰. The earliest diagenetic nature of these cements is documented by the presence of ubiquitous, non-compacted fossil plant remains encased in phase I dolomite as well as by the complex zoned luminescence patterns in the crystals and is supported by crystallographic and thermodynamic considerations. It is argued that organic matter, and specifically carboxyl groups, reduced thermodynamic barriers for dolomite formation and facilitated Mg/CaCO3 precipitation. The data shown here

  17. Treating tar sands formations with dolomite

    Energy Technology Data Exchange (ETDEWEB)

    Vinegar, Harold J.; Karanikas, John Michael

    2013-10-15

    A method for treating a karsted formation containing heavy hydrocarbons and dolomite includes providing heat to at least part of one or more karsted layers in the formation from one or more heaters located in the karsted layers. A temperature in at least one of the karsted layers is allowed to reach a decomposition temperature of dolomite in the formation. The dolomite is allowed to decompose and at least some hydrocarbons are produced from at least one of the karsted layers of the formation.

  18. Pityriasis rubra pilaris following exposure to dolomite.

    Science.gov (United States)

    Iraji, Fariba; Siadat, Amir H

    2013-07-01

    In this case report, we present a 30-year-old man who developed pityriasis rubra pilaris (PRP) following exposure to Dolomite. The diagnosis of PRP was confirmed histologically and the patient was successfully treated with acitretin and cyclosporine.

  19. Treating tar sands formations with dolomite

    Energy Technology Data Exchange (ETDEWEB)

    Vinegar, Harold J.; Karanikas, John Michael

    2010-06-08

    Methods for treating a tar sands formation are described herein. The tar sands formation may include dolomite and hydrocarbons. Methods may include providing heat at less than the decomposition temperature of dolomite from one or more heaters to at least a portion of the formation. At least some of the hydrocarbon fluids are mobilized in the formation. At least some of the hydrocarbon fluids may be produced from the formation.

  20. Entre historias y culebras: más que una bahía (Bahía Culebra, Guanacaste, Costa Rica

    Directory of Open Access Journals (Sweden)

    Celeste Sánchez-Noguera

    2012-04-01

    Full Text Available Bahía Culebra (Golfo de Papagayo, Guanacaste, Costa Rica es una unidad geomorfológica semicerrada y bastante protegida, que cuenta con una amplia diversidad de recursos naturales, favoreciendo el asentamiento de poblaciones humanas y su consecuente desarrollo marinocostero. La reseña histórica de Bahía Culebra indica que este ha sido un sitio muy importante desde la perspectiva histórica, política, cultural y económica. La consulta bibliográfica incluyó documentos que datan de mediados del siglo XIX hasta el año 2011, los cuales fueron recopilados del Archivo Nacional de Costa Rica, la Biblioteca Nacional, el Centro de Documentación del Centro de Investigaciones Históricas de América Central y algunas colecciones privadas. Su notoria belleza escénica, la disponibilidad de redes viales en buen estado y la cercanía a un aeropuerto internacional han facilitado que la bahía se convierta en un centro turístico intensivo, generando un acelerado desarrollo costero a raíz de la creación del proyecto Polo Turístico Golfo de Papagayo (PTGP. Se debe fortalecer el marco jurídico e implementar acciones que promuevan el bienestar de las poblaciones locales y la adecuada gestión de los recursos naturales, tomando en cuenta todos los factores y actores involucrados.

  1. Adsorption of arsenate on untreated dolomite powder.

    Science.gov (United States)

    Ayoub, G M; Mehawej, M

    2007-09-05

    Raw dolomite powder was evaluated for its efficiency in adsorbing As(V) from water. An experimental setup comprised of a fluidized dolomite powder bed was used to assess the impact of various test variables on the efficiency of removal of As(V). Test influents including distilled water (DW), synthetic groundwater (SGW) and filtered sewage effluent (FSE) were employed to assess the effect of influent parameters on the adsorption process and the quality of the effluent generated. Dolomite exhibited good As(V) removal levels for distilled water (>92%) and synthetic ground water (>84%) influents at all initial As(V) concentrations tested (0.055-0.600 ppm). Breakthrough of dolomite bed occurred after 45 bed volumes for DW and 20 bed volumes for SGW influents with complete breakthrough taking place at more than 300 bed volumes. As(V) removal from FSE influents was relatively unsuccessful as compared to the DW and SGW influents. Partial removal in the order of 32% from filtered sewage effluent at initial concentration of 0.6 mg/L started at 75 bed volumes and gradually stopped at 165 bed volumes. Varying degrees of As(V) adsorption capacities were observed by the different test influents employed, which indicate that the adsorption of As(V) is adversely affected by competing species, mainly sulfates and phosphates present in the influent. The adsorptive behavior of dolomite was described by fitting data generated from the study into the Langmuir and Freundlich isotherm models. Both models described well the adsorption of dolomite. The average isotherm adsorptive capacity was determined at 5.02 mug/g. Regeneration of the dolomite bed can be achieved with the use of caustic soda solution at a pH of 10.5.

  2. Kinetics of Leaching Calcium from Dolomite

    Directory of Open Access Journals (Sweden)

    Azizi, A.

    2011-06-01

    Full Text Available Magnesia is obtained from magnesite ore and the production process applied should remove accompanying minerals that reduce its refractoriness. Given that magnesite reservoirs are more exploited and largely exhausted, there is a growing need for production of magnesia on the basis of other magnesium minerals. Dolomite is a promising source of magnesia because it forms large deposits, is easy to exploit, and generally contains a small quantity of impurities.The kinetics of calcium leaching from dolomite by magnesium-nitrate solution has been studied. The research program included the influence of temperature, mass fraction of magnesium nitrate in solution, dolomite particle size and leaching time. Time dependence of calcium leaching is described by relevant kinetic equations. Rate coefficients, their temperature dependence and Arrhenius activation energy have been determined.

  3. Preliminary Geologic Map of the Culebra Peak Area, Sangre de Cristo Mountains, Las Animas and Costilla Counties, Colorado

    Science.gov (United States)

    Fridrich, Christopher J.; Kirkham, Robert M.

    2008-01-01

    This geologic map provides new geologic mapping at 1:50,000-scale in the Culebra Peak area of the Sangre de Cristo Mountains of south-central Colorado. The map area includes all of the El Valle Creek, Stonewall, Culebra Peak, and Torres 7.5' quadrangles. Paleoproterozoic crystalline basement rocks are exposed along the crest of the Culebra Range which include a calc-alkaline gneiss sequence and a metasedimentary and bimodal metavolcanic sequence which are strongly foliated and display a northeast-southwest oriented structural trend. These rocks are intruded by several large granitic bodies and smaller amphibolitic and pegmatitic bodies which are also foliated. These basement rocks are intruded by a set of younger Neoproterozoic to lower Paleozoic gabbro dikes which are nonfoliated. These crystalline rocks are overlain to the east of the Culebra Range by a thick sequence of Phanerozoic sedimentary rocks which include upper Paleozoic syn-tectonic sedimentary rocks of the Colorado Trough related to the Ancestral Rocky Mountains, Mesozoic post-tectonic sedimentary rocks, Cretaceous interior seaway sediments, and Laramide-age syn-tectonic sedimentary rocks of the Raton Basin. These rocks are faulted and folded by Laramide-age deformation. Tertiary igneous and volcaniclastic rocks that postdate the Laramide Orogeny are exposed throughout the map area and to the west of the Culebra Range, syntectonic sedimentary and volcanic rocks of the Sante Fe Group were deposited as fill in basins of the Rio Grande rift. These deposits are cut by rift-related extensional faults. Surficial units include alluvial, lacustrine, glacial, and mass-wasting deposits.

  4. Antiviral activities of heated dolomite powder.

    Science.gov (United States)

    Motoike, Koichi; Hirano, Shozo; Yamana, Hideaki; Onda, Tetsuhiko; Maeda, Takayoshi; Ito, Toshihiro; Hayakawa, Motozo

    2008-12-01

    The effect of the heating conditions of dolomite powder on its antiviral activity was studied against the H5N3 avian influenza virus. Calcium oxide (CaO) and magnesium oxide (MgO), obtained by the thermal decomposition of dolomite above 800 degrees C, were shown to have strong antiviral activity, but the effect was lessened when the heating temperature exceeded 1400 degrees C. Simultaneous measurement of the crystallite size suggested that the weakening of the activity was due to the considerable grain growth of the oxides. It was found that the presence of Mg in dolomite contributed to the deterrence of grain growth of the oxides during the heating process. Although both CaO and MgO exhibited strong antiviral activity, CaO had the stronger activity but quickly hydrated in the presence of water. On the other hand, the hydration of MgO took place gradually under the same conditions. Separate measurements using MgO and Mg(OH)2 revealed that MgO had a higher antiviral effect than Mg(OH)2. From the overall experiments, it was suggested that the strong antiviral activity of dolomite was related to the hydration reaction of CaO.

  5. Geothermal convection: a mechanism for dolomitization at Enewetak Atoll?

    Science.gov (United States)

    Wilson, A.M.; Sanford, W.; Whitaker, F.; Smart, P.

    2000-01-01

    Geothermal convection in carbonate platforms could drive massive dolomitization by supplying mass transport of magnesium over long periods and at temperatures high enough to overcome kinetic limitations. Reactive-transport simulations based on Enewetak Atoll show dolomitization in a thin band at a permeability contrast near the base of the platform, which is consistent with field observations of dolomitized Eocene deposits. Dolomitization is predicted at approximately 6% per My at temperatures of 45–60°C, and complete dolomitization could be accomplished in ∼16 My. Calcium enrichment of pore fluids and upward transport of these fluids is established early, prior to 30 ky.

  6. [Medusae (Cnidaria: Hydrozoa) from a coastal upwelling zone, Culebra Bay, Pacific, Costa Rica].

    Science.gov (United States)

    Rodríguez-Sáenz, Karina; Vargas-Zamora, José A; Segura-Puertas, Lourdes

    2012-12-01

    The hydromedusae have an important role in marine trophic webs due to their predatory feeding habits. This is the first study of this group of gelatinous marine zooplankton in a coastal upwelling area of Central America. The composition and abundance variability of hydromedusae were studied during six months in 1999 at four stations in Culebra Bay, Gulf of Papagayo, Pacific coast of Costa Rica (10 degrees 37' N-85 degrees 40' W). A total of 53 species were identified, of which 26 are new records for Costa Rica, 21 are new records for Central America, and eight are new records for the Eastern Tropical Pacific. The more abundant species (more than 30% of the total abundance) were Liriope tetraphylla, Solmundella bitentaculata and Aglaura hemistoma. Six species occurred throughout the sampling period, 10 were present only during the dry season (December-April), and 17 were so during the rainy season (May-November). Significant differences of medusan abundances were found between seasons (dry vs. rainy). Maximum abundance (2.1 +/- 4.3ind./m3) was recorded when upwelled deeper water influenced the Bay, as indicated by local higher oxygen concentrations and lower water temperatures. The relatively high species richness of medusae found in Culebra Bay is probably related to factors like the pristine condition of the Bay, the arrival of oceanic species transported by the Equatorial Counter Current (ECC), the eastward shoaling of the Costa Rica Dome, and local currents. Illustrations of the 15 more important species are included to facilitate their identification and foster future work in the region.

  7. Atmospheric forcing of cool subsurface water events in Bahía Culebra, Gulf of Papagayo, Costa Rica

    Directory of Open Access Journals (Sweden)

    Eric J. Alfaro

    2012-04-01

    Full Text Available Bahía Culebra, at Gulf of Papagayo on the north Pacific coast of Costa Rica, is an area of seasonal upwelling where more intense cooling events may occur during some boreal winter weeks mainly. To study these extreme cool events, records of nine sea subsurface temperature stations from 1998 to 2010 were analyzed. Five events associated with extremely cool temperatures in this region were identified from these records and taken as study cases. Sea temperatures decreased about 8-9ºC during these events and occurred while cold fronts were present in the Caribbean, with strong trade wind conditions over Central America. These strong wind conditions may have favored the offshore displacement of the sea surface water. The axis of Bahía Culebra runs northeastsouthwest, a condition that favors and triggers cool water events, mainly because the displaced water is replaced by water from deeper levels.

  8. Resetting of Mg isotopes between calcite and dolomite during burial metamorphism: Outlook of Mg isotopes as geothermometer and seawater proxy

    Science.gov (United States)

    Hu, Zhongya; Hu, Wenxuan; Wang, Xiaomin; Lu, Yizhou; Wang, Lichao; Liao, Zhiwei; Li, Weiqiang

    2017-07-01

    Magnesium isotopes are an emerging tool to study the geological processes recorded in carbonates. Calcite, due to its ubiquitous occurrence and the large Mg isotope fractionation associated with the mineral, has attracted great interests in applications of Mg isotope geochemistry. However, the fidelity of Mg isotopes in geological records of carbonate minerals (e.g., calcite and dolomite) against burial metamorphism remains poorly constrained. Here we report our investigation on the Mg isotope systematics of a dolomitized Middle Triassic Geshan carbonate section in eastern China. Magnesium isotope analysis was complemented by analyses of Sr-C-O isotopic compositions, major and trace element concentrations, and petrographic and mineralogical features. Multiple lines of evidence consistently indicated that post-depositional diagenesis of carbonate minerals occurred to the carbonate rocks. Magnesium isotope compositions of the carbonate rocks closely follow a mixing trend between a high δ26Mg dolomite end member and a low δ26Mg calcite end member, irrespective of sample positions in the section and calcite/dolomite ratio in the samples. By fitting the measured Mg isotope data using a two-end member mixing model, an inter-mineral Δ26Mgdolomite-calcite fractionation of 0.72‰ was obtained. Based on the experimentally derived Mg isotope fractionation factors for dolomite and calcite, a temperature of 150-190 °C was calculated to correspond to the 0.72‰ Δ26Mgdolomite-calcite fractionation. Such temperature range matches with the burial-thermal history of the local strata, making a successful case of Mg isotope geothermometry. Our results indicate that both calcite and dolomite had been re-equilibrated during burial metamorphism, and based on isotope mass balance of Mg, the system was buffered by dolomite in the section. Therefore, burial metamorphism may reset Mg isotope signature of calcite, and Mg isotope compositions in calcite should be dealt with caution in

  9. Clumped Isotopes in Bahamian Dolomites: A Rosetta Stone?

    Science.gov (United States)

    Murray, S.; Swart, P. K.; Arienzo, M. M.

    2014-12-01

    Low temperature dolomite formation continues to be an enigmatic process. However, with the advent of the clumped isotope technique, there is an opportunity to determine the temperature of formation as well as the δ18O of the fluid (δ18Ow) from which it formed. By using samples with a well constrained geologic and thermal history, we have attempted to accurately develop a technique for the application of clumped isotopes to varying dolomite systems. Samples for this study were taken from two cores, one from the island of San Salvador and one on Great Bahama Bank (known as Clino), located on the eastern and western edges respectively of the Bahamian Archipelago. Both cores penetrate through Pleistocene to Miocene aged carbonates. The San Salvador core has a 110m section of pure, near stoichiometric dolomite, while the Clino core is of a mixed carbonate composition with varying abundances (0% - 50%) of calcian dolomite (42-46 mol % MgCO3). The water temperature profile of the Bahamas can be assumed over time due to the stable geology and no influence of higher temperature waters. Because of its location and the present burial depth, the largest influence on dolomite formation has been changes in sea level. As the dolomites from San Salvador are 100% dolomite, the Δ47 was determined directly. The Clino dolomites however were only partially dolomitized and so were treated with buffered acetic acid to remove non-dolomite carbonates. This was carried out in stages, using X-ray diffraction to determine composition, followed by the measurement of Δ47 after each leaching episode. Because the dolomite formation temperature and δ18Ow can be constrained, it becomes possible to evaluate the applicability of the multitude of clumped isotope correction schemes that have been applied to various dolomite samples. Also tested were several different equations which link temperature to the δ18O of the dolomite allowing the δ18O of the water to be calculated. This is a necessary

  10. Historia de la investigación marino-costera en Bahía Culebra, Pacífico Norte, Guanacaste, Costa Rica

    Directory of Open Access Journals (Sweden)

    Jorge Cortés

    2012-04-01

    Full Text Available Bahía Culebra está ubicada en la costa Pacífica norte de Costa Rica en una región de afloramiento estacional. En este trabajo presento la historia de la investigación marina en Bahía Culebra, para sintetizar lo que se ha hecho y resaltar lo que falta por investigar. Los organismos marinos de Bahía Culebra se empezaron a estudiar en la década de 1920 y muy intensamente en la década de 1930 con las expediciones de la Fundación Allan Hancock y de la Sociedad Zoológica de Nueva York. La mayor parte de la investigación marina se ha realizado desde la década de 1980 por investigadores y estudiantes del Centro de Investigación en Ciencias del Mar y Limnología (CIMAR de la Universidad de Costa Rica. Los ecosistemas mejor estudiados son las comunidades y arrecifes coralinos, seguido por las investigaciones sobre zooplancton. Se han publicado registros de 577 especies marinas en Bahía Culebra y se le suman 20 especies más con las publicadas en este Suplemento. Aún así, todavía falta estudiar varios ecosistemas y grupos de organismos. Es imperativo realizar esfuerzo para proteger y conservar los ecosistemas y biodiversidad marina de Bahía Culebra.

  11. Dolomite in caves: Recent dolomite formation in oxic, non-sulfate environments. Castañar Cave, Spain

    OpenAIRE

    Alonso-Zarza, Ana María; Martín Pérez, Andrea

    2008-01-01

    Dolomite is a common mineral in the rock record but rare in recent superficial environments. Where it does occur, it is related to anoxic, sulfate-rich environments and microbial activity. The occurrence of some dolomite deposits in caves, however, indicates that dolomite formation is also possible in oxic, non-sulfate settings. Dolomite is forming at 17 °C and in oxic-vadose conditions on the host rocks and aragonite speleothems of the Castañar Cave, Cáceres, Spain. It appears as...

  12. Petrologic and geochemical constraints on the origin of subsurface dolomite, Enewetak Atoll: An example of dolomitization by normal seawater

    Science.gov (United States)

    Saller, Arthur H.

    1984-04-01

    Dolomite is present 1,250 1,400 m below sea level in Eocene strata of Enewetak Atoll. Petrographically, the deep Enewetak dolomite postdates brittle compaction of rigid grains in the host Eocene strata. The 87Sr/86Sr ratio of these dolomites (0.70865 0.70901) indicates that they formed at one or more times between the middle Miocene and the present. Since the top of the lower Miocene is more than 900 m above the deep dolomitic interval, the dolomite must have formed at a minimum burial depth of 900 m. Stable-oxygen-isotope determinations suggest dolomite precipitation from cold marine water. Lower Miocene and Eocene carbonate strata on the atoll are apparently in open communication with cold, modern ocean water, suggesting that those same strata were in open communication with ocean water during dolomitization. At a depth of about 1,000 m, modern Pacific Ocean water becomes undersaturated with respect to calcite but is still supersaturated with respect to dolomite. Therefore, it is proposed that the deep Enewetak dolomite precipitated from cold, deep ocean water (undersaturated with respect to calcite) at a burial depth of more than 900 m.

  13. Dolomite microstructures between 390° and 700 °C: Indications for deformation mechanisms and grain size evolution

    Science.gov (United States)

    Berger, Alfons; Ebert, Andreas; Ramseyer, Karl; Gnos, Edwin; Decrouez, Danielle

    2016-08-01

    Dolomitic marble on the island of Naxos was deformed at variable temperatures ranging from 390 °C to >700 °C. Microstructural investigations indicate two end-member of deformation mechanisms: (1) Diffusion creep processes associated with small grain sizes and weak or no CPO (crystallographic preferred orientation), whereas (2) dislocation creep processes are related with larger grain sizes and strong CPO. The change between these mechanisms depends on grain size and temperature. Therefore, sample with dislocation and diffusion creep microstructures and CPO occur at intermediate temperatures in relative pure dolomite samples. The measured dolomite grain size ranges from 3 to 940 μm. Grain sizes at Tmax >450 °C show an Arrhenius type evolution reflecting the stabilized grain size in deformed and relative pure dolomite. The stabilized grain size is five times smaller than that of calcite at the same temperature and shows the same Arrhenius-type evolution. In addition, the effect of second phase particle influences the grain size evolution, comparable with calcite. Calcite/dolomite mixtures are also characterized by the same difference in grain size, but recrystallization mechanism including chemical recrystallization induced by deformation may contribute to apparent non-temperature equilibrated Mg-content in calcite.

  14. Descubrimiento de pinturas rupestres en la Sierra de la Culebra (Zamora

    Directory of Open Access Journals (Sweden)

    Ramón GRANDE DEL BRÍO

    2009-10-01

    Full Text Available En el mes de enero de 1977, un recorrido de prospección arqueológica me llevó hasta Linarejos, aldea situada cabe la falda oriental de la sierra de la Culebra, al noroeste de la provincia de Zamora. Tomé desde allí el antiguo camino que conducía a Villarino de Manzanas, hacia el sur. Un grupo de canchales de naturaleza cuarcítica con orientación noroeste-sureste (armoricana se extendían cabe el paso del Portillón. El reconocimiento por mi parte de varios covachos que se abrían en la canchalera en cuestión me permitió descubrir pinturas rupestres de tipo esquemático en uno de ellos. Las pinturas se presentan distribuidas en un panel interior del covacho, a una altura de un metro setenta centímetros respecto del suelo. Están pintadas en color rojo. Ligeramente desvaídas.

  15. Constraining dolomitization by Mg isotopes: A case study from partially dolomitized limestones of the middle Cambrian Xuzhuang Formation, North China

    Science.gov (United States)

    Peng, Yang; Shen, Bing; Lang, Xian-Guo; Huang, Kang-Jun; Chen, Ji-Tao; Yan, Zhen; Tang, Wen-bo; Ke, Shan; Ma, Hao-Ran; Li, Fang-Bing

    2016-03-01

    The "dolomite problem" refers to the rare dolomite formation in modern oceans that is in sharp contrast to the widespread ancient dolostone in rock record, as well as failure of laboratory inorganic dolomite precipitation at near Earth-surface temperature. Novel Mg isotope systematics provides a promising tool in resolving the "dolomite problem". Here, we develop a protocol to place constraints on the dolomitization process by using Mg isotopes. In this study, we measured Mg isotopic compositions (δ26Mg) of two batches of partially dolomitized limestone samples from the middle Cambrian Xuzhuang Formation in North China. δ26Mg varies between -0.55‰ and -3.18‰, and shows a negative linear correlation with 1>/[Mg>], suggesting that δ26Mg can be described by a binary mixing between the calcite and dolomite components. Mg isotopic composition of the dolomite component (δ26Mgdol) for the lower sample set that is collected from a 4 m stratigraphic interval containing three high-frequency ribbon rock-packstone cycles is -1.6‰, while δ26Mgdol for the upper sample set (from a thick sequence of ribbon rock) is significantly higher (-0.3‰). However, neither mineralogical and elemental compositions, carbon and oxygen isotopes, nor crystal morphologies of dolomite provides diagnostic criteria to differentiate these two batches of samples. δ26Mgdol of the Xuzhuang limestone is simulated by the Advective Flow (AF) and the Diffusion-Advection-Reaction (DAR) models. The AF model assumes that Mg is transported by advective fluid flows, while the DAR model simulates a contemporaneous seawater dolomitization process, in which Mg is delivered by diffusion. The AF modeling result indicates that δ26Mg of the dolomitization fluid is +0.4‰ and +1.7‰ for the lower and upper sample sets, respectively. These values are significantly higher than modern and Cenozoic seawater Mg isotopic composition, suggesting that the dolomitization fluid is not contemporaneous seawater. The

  16. Review of Dolomite as Precursor of Geopolymer Materials

    Directory of Open Access Journals (Sweden)

    Azimi E.A.

    2016-01-01

    Full Text Available Geopolymer is an environmentally friendly cementitious binder that does not require the existence of ordinary Portland cement (OPC. Geopolymer has many excellent advantages, including high early strength, low shrinkage, good thermal resistance and good chemical resistance. Previous commonly used materials include fly ash, clay and slag. The used of dolomite as precursor material in geopolymer field is still new and at the early stage of study. Only a few researchers have done studies on dolomite in geopolymer. Dolomite (CaMg(CO32 is abundant and generally inexpensive natural minerals. The possible use of these bulk calcium carbonate materials in improving the mechanical properties of geopolymers will therefore be of great interest. This paper summarizes some research outcomes on dolomite in geopolymer along with the potential of dolomite as geopolymer composites.

  17. Study of dolomite dissolution at various temperatures - Evidence for the formation of nanocrystalline secondary phases at dolomite surface and influence on dolomite interactions with other minerals

    Science.gov (United States)

    Debure, M.; Andreazza, P.; Grangeon, S.; Lerouge, C.; Montes-Hernandez, G.; MADE, B.; Tournassat, C.

    2015-12-01

    In most clay-rock geological formation studied for the storage of nuclear waste, pore water compositions are expected to be at equilibrium with carbonate minerals, which are always included in predictive models for pore water composition calculations [1]. Among the carbonates known to be present, dolomite may be problematic in the pore water composition calculation because its solubility spans a large range of values as a function of its crystallinity in thermodynamic databases. In addition, the composition of dolomite minerals observed in clay-rock formations such as Callovian-Oxfordian or Opalinus clay formation differs from this of a pure dolomite: the Ca/Mg stoichiometry is not ideal, and the minerals contain minor amounts of Fe and traces of many other elements [2]. To understand the influence of secondary phases precipitation during dolomite dissolution on pore water chemistry, the dissolution of monocrystals of dolomite were investigated at 25 °C and at 80 °C in a pH range 3 to 8 for various time periods (30 minutes to 21 days) in sealed PTFE reactors. Solution analyses evidenced a stoichiometric release of Ca and Mg in solution during dolomite dissolution. Scanning Electron Microscopy (SEM), Raman and X-Ray Diffraction (XRD) analyses did not evidence secondary Mg-bearing minerals precipitation, but revealed the formation of Fe-bearing particles on the dolomite surface. Morphological characterizations performed with Small-angle X-ray scattering (SAXS) evidenced that the precipitation occurs along a specific crystallographic plane of the dolomite monocrystal. Thus, the precipitated nanoparticles clustered on specific surface sites, and are made of Fe-rich phases poorly crystallized (carbonates, oxides and hydroxides). [1] Tournassat et al. 2015. Ch. 3: Chemical Conditions in Clay-Rocks. Natural and Engineered Clay Barriers, Elsevier. [2] Lerouge et al. 2011. Geochim. et Cosmoch. Acta, 2011, 75, 2633-2663.

  18. Biomineralization of dolomite and magnesite discovered in tropical coralline algae: a biological solution to the geological dolomite problem

    Science.gov (United States)

    Nash, M. C.; Troitzsch, U.; Opdyke, B. N.; Trafford, J. M.; Russell, B. D.; Kline, D. I.

    2011-06-01

    Dolomite is a magnesium-rich carbonate mineral abundant in fossil carbonate reef platforms but surprisingly rare in modern sedimentary environments, a conundrum known as the ''Dolomite Problem". Marine sedimentary dolomite has been interpreted to form by an unconfirmed, post-depositional diagenetic process, despite minimal experimental success at replicating this. Here we show that dolomite, accompanied by magnesite, forms within living crustose coralline alga, Hydrolithon onkodes, a prolific global tropical reef species. Chemical micro-analysis of the coralline skeleton reveals that not only are the cell walls calcitised, but that cell spaces are typically filled with magnesite, rimmed by dolomite, or both. Mineralogy was confirmed by X-ray diffraction. Thus there are at least three mineral phases present (magnesium calcite, dolomite and magnesite) rather than one or two (magnesium calcite and brucite) as previously thought. Our results are consistent with dolomite occurrences in coralline algae rich environments in fossil reefs. Instead of a theory of post-depositional dolomitisation, we present evidence revealing biomineralization that can account for the massive formations seen in the geologic record. Additionally, our findings imply that previously unrecognized dolomite and magnesite have formed throughout the Holocene. This discovery together with the scale of coralline algae dominance in past shallow carbonate environments raises the possibility that environmental factors driving this biological dolomitisation process have influenced the global marine magnesium/calcium cycle. Perhaps, most importantly, we reveal that what has been considered a geological process can be a biological process, having many implications for both disciplines.

  19. Selección natural, genética cuantitativa y evolución en culebras

    OpenAIRE

    Javier Manjarrez Silva

    2001-01-01

    Se describen los conceptos, términos y técnicas empleadas en la genética cuantitativa y la selección natural, en particular de los componentes de la varianza fenotípica y sus técnicas para reducirla. Se utiliza a las serpientes como ejemplo por las características que presentan y se justifica la aplicación de este tipo de estudios, en particular para las estimaciones de la heredabilidad de caracteres cuantitativos de las culebras, con el fin de visualizar su posible base genética e implicacio...

  20. Atmospheric forcing of cool subsurface water events in Bahía Culebra, Gulf of Papagayo, Costa Rica

    Directory of Open Access Journals (Sweden)

    Eric J. Alfaro

    2012-04-01

    Full Text Available Bahía Culebra, at Gulf of Papagayo on the north Pacific coast of Costa Rica, is an area of seasonal upwelling where more intense cooling events may occur during some boreal winter weeks mainly. To study these extreme cool events, records of nine sea subsurface temperature stations from 1998 to 2010 were analyzed. Five events associated with extremely cool temperatures in this region were identified from these records and taken as study cases. Sea temperatures decreased about 8-9ºC during these events and occurred while cold fronts were present in the Caribbean, with strong trade wind conditions over Central America. These strong wind conditions may have favored the offshore displacement of the sea surface water. The axis of Bahía Culebra runs northeastsouthwest, a condition that favors and triggers cool water events, mainly because the displaced water is replaced by water from deeper levels.Bahía Culebra, localizada en el Golfo de Papagayo, al norte de la costa del Pacífico de Costa Rica, es un área de afloramiento estacional, en donde pueden ocurrir eventos de enfriamiento más intensos, principalmente durante algunas semanas del invierno boreal. Para estudiar estos eventos de enfriamiento extremo, se analizaron datos de nueve estaciones con registros de la temperatura subsuperficial del mar, desde 1998 hasta el 2010. A partir de estos registros, se identificaron cinco casos de estudio asociados a enfriamientos del mar en la región. Los descensos de la temperatura de estos eventos fueron de aproximadamente 8-9ºC y se asociaron al paso de empujes fríos en la región del Caribe y una fuerte magnitud del viento alisio sobre América Central. Este reforzamiento del flujo alisio favorece el desplazamiento del agua superficial hacia afuera de Bahía Culebra, cuyo eje principal se ubica en la dirección noreste-suroeste. Lo anterior favorece y provoca un enfriamiento de la temperatura del mar en la bahía, ya que el agua desplazada es

  1. Selección natural, genética cuantitativa y evolución en culebras

    Directory of Open Access Journals (Sweden)

    Javier Manjarrez Silva

    2001-01-01

    Full Text Available Se describen los conceptos, términos y técnicas empleadas en la genética cuantitativa y la selección natural, en particular de los componentes de la varianza fenotípica y sus técnicas para reducirla. Se utiliza a las serpientes como ejemplo por las características que presentan y se justifica la aplicación de este tipo de estudios, en particular para las estimaciones de la heredabilidad de caracteres cuantitativos de las culebras, con el fin de visualizar su posible base genética e implicaciones evolutivas.

  2. Patrones espaciales de la riqueza específica de las culebras Thamnophis en México

    OpenAIRE

    Crystian Sadiel Venegas-Barrera

    2011-01-01

    Se identificaron tanto las áreas de mayor riqueza específica de las culebras del género Thamnophis y su presencia en las provincias biogeográficas y las Regiones Terrestres Prioritarias (RTP), como los factores antropogénicos que pueden influir en su distribución. Con la combinación de mapas de distribución potencial de las especies se creó un mapa de riqueza específica para calcular el porcentaje de celdas ocupadas por el género dentro de cada provincia biogeográfica, de cada RTP y conocer e...

  3. Hydrogeology of Puerto Rico and the outlying islands of Vieques, Culebra, and Mona

    Science.gov (United States)

    Gómez-Gómez, Fernando; Rodríguez-Martínez, Jesús; Santiago, Marilyn

    2014-01-01

    The availability of hydrogeologic maps for Puerto Rico and the outlying islands of Vieques, Culebra, and Mona are important to hydrogeologists, groundwater specialists, and water resource managers and planners. These maps, in combination with the report, serve as a source of information to all users by providing basic hydrogeologic and hydrologic knowledge in a concise illustrated format. Puerto Rico and the outlying islands cover a total area of 8,927 square kilometers (km2). Of this total area, about 3,500 km2 are underlain by hydrogeologic units that are classified as intergranular or fissured. These hydrogeologic units form the principal aquifer systems throughout Puerto Rico and the outlying islands. In Puerto Rico, the most extensive and intensely developed aquifers are the North Coast Limestone aquifer system and the South Coastal Alluvial Plain aquifer system. Withdrawals from these two aquifer systems constitute nearly 70 percent of the total groundwater withdrawn in Puerto Rico. The spatial extent of the North Coast Limestone aquifer system is about 2,000 km2. Within this aquifer system, groundwater development is greatest in the 800-km2 area between the Río Grande de Arecibo and the Río de la Plata. This also is the area for which concern is the highest regarding the future use of groundwater as a primary source of water for domestic and industrial use. With an estimated withdrawal of 280,000 cubic meters per day (m3/d), groundwater constituted the principal source of water within this area providing 100 percent of the water for self-supplied industries and about 85 percent for public water supplies in 1985. By 2005, groundwater withdrawals decreased to 150,000 m3/d. The spatial extent of the South Coastal Alluvial Plain aquifer system is about 470 km2. The estimated consumptive groundwater withdrawal from the aquifer system was 190,000 m3/d in 1980 and 170,000 m3/d in 2005. About 60 percent and 40 percent of the groundwater withdrawal from the South

  4. Geología de Bahía Culebra, Guanacaste, Costa Rica

    Directory of Open Access Journals (Sweden)

    Pablo Herrera Zúñiga

    2012-04-01

    Full Text Available La geología de Bahía Culebra, Guanacaste, Costa Rica, está compuesta por rocas volcánicas de corteza oceánica; sedimentos marinos depositados en el talud, la plataforma continental y zonas someras cerca de la costa; secuencias de rocas piroclásticas intercaladas con sedimentos continentales y depósitos Cuaternarios recientes. En la base de la secuencia estratigráfica afloran los basaltos masivos, algunas veces en almohadilla, del Complejo de Nicoya con textura afanítica con fenocristales de olivino, augitas y plagioclasas. Dentro de la misma Formación se incluyen intrusivos de gabro masivos con piroxenos y plagiogranitos con fenocristales de plagioclasas y hornblenda. Seguidamente afloran las calizas de la Formación El Viejo constituida por colonias arrecifales e intercalaciones calcáreas. La Formación Montezuma compuesta por facies de arenisca media fosilífera, facies de arenisca media con laminación cruzada y facies rítmicas de areniscas y lutitas. Las Dacitas Carbonal están compuestas por lavas hexagonales y variaciones brechosas con clastos de pómez y minerales de alteración. La Formación Bagaces se constituye de varios eventos eruptivos con secuencias de ignimbritas y un depósito sedimentario posiblemente pluvial de arenas volcaniclásticas. En la parte superior de la secuencia estratigrafica se incluyen los depósitos producto de factores erosivos tales como coluvios, arenas de playa, sedimentos de zonas de manglar y aluviones.

  5. DOLOMITE AS AN ALTERNATIVE WEIGHTING AGENT IN DRILLING FLUIDS

    Directory of Open Access Journals (Sweden)

    M. J. BADRUL

    2007-08-01

    Full Text Available A series of experimental tests have been conducted to assess the suitability of using dolomite as an alternative weighting agent in drilling fluids. Currently, barite is widely used as weighting agent in drilling fluids slurry to ensure proper weights are achieved. However, barite contains toxic materials which make it unattractive from health and environment point of views. This is especially true when drilling operations are offshore, where most of the used drilling fluids will be dumped back into the sea. In this work, rheological properties of dolomite blend drilling fluids slurry were studied. Dolomite rocks were first crushed to produce dolomite powder, before being mixed with water and bentonite at various proportions. A total of 10 samples which contains various percentages of water, bentonite and dolomite were studied. For each sample, its rheological properties were determined. Such properties include density from mud balance, viscosity from viscometer, filtrate loss from API filter press and gel strength. The effect of aging on the properties of drilling fluids was also studied. From the study, it is concluded that Sample E, which consists of 70% dolomite by weight, produces the most stable drilling fluids. It is also observed that the amount of 336 g of dolomite in the sample shows the similar physical and rheological properties to that of the 480 g barite in the sample although the density for both samples is not same.

  6. Nanotoxicity of dolomite mineral of commercial importance in India.

    Science.gov (United States)

    Patil, Govil; Khan, Mohd Imran; Akhtar, Mohd Javed; Ashquin, Mohd; Sultana, Sarwat; Ahmad, Iqbal

    2011-02-01

    The risk of occupational exposure to dolomite, an important mineral exists both in organized as well as unorganized sectors. Toxicological profiles of bulk dolomite are meagerly known in general and its nanotoxicity in particular. Effects of micro- and nano particles on cell viability, LDH leakage and markers of oxidative stress were observed. The study indicated that cytotoxicity of dolomite nanoparticles is significantly higher than the microparticles. The study thus suggests for the prescription of exposure limit for nanodolomite in the best interest of health of workers at risk of exposure under mining, milling and industrial environment.

  7. An Assessment of the Condition of Coral Reefs off the Former Navy Bombing Ranges at Isla De Culebra and Isla De Vieques, Puerto Rico

    Science.gov (United States)

    2005-04-01

    Isla De Culebra and Isla De Vieques, Puerto Rico the town of Esperanza , had better reef conditions than Dewey Reef. We did not notice any evidence of...Hurricane control on shelf-edge-reef architecture around Grand Cayman. Sedimentology 44:479-506. Bohnsack, J.A., and S.P. Bannerot. 1986. A

  8. Threats and opportunities for post-closure development in dolomitic ...

    African Journals Online (AJOL)

    Threats and opportunities for post-closure development in dolomitic ... in the form of sinkholes and widespread radioactive pollution exacerbate such fears. ... developments such as aquaculture, agriculture and different forms of tourism relating ...

  9. Rheology of cement mixtures with dolomite filler

    Directory of Open Access Journals (Sweden)

    Martínez de la Cuesta, P. J.

    2000-06-01

    Full Text Available This experimental program has studied the behavior of fresh paste made up from cements mixed with dolomite filler. Through prior experiments the starting point is obtained for the designs 22 and 23 factorials. With these designs the governing equations are established that influence the specific surface of the filler, the filler percentage and the ratio water/(cement + filler, used as objective functions: test probe penetration, flow on table and shear stress in viscometer. Also the type of rheological conduct is determined and the influence over initial and final setting is observed.

    Este programa experimental estudia el comportamiento de las pastas frescas fabricadas a partir de cementos mezclados con filler dolomítico. En los experimentos previos se obtiene el punto central para los diseños 22 y 23 factoriales. Con estos diseños se establecen las ecuaciones que rigen la influencia de la superficie específica del filler, el porcentaje de filler y la relación agua/(cemento + filler, utilizando como funciones objetivos la penetración de sonda, la mesa de sacudidas y la tensión de corte en el viscosímetro. También se determina el tipo de conducta reológica y la influencia sobre el principio y fin de fraguado.

  10. Microbial dolomite crusts from the carbonate platform off western India

    Digital Repository Service at National Institute of Oceanography (India)

    Rao, V.P.; Kessarkar, P.M.; Krumbein, W.E.; Krajewski, K.P.; Schneider, R.J.

    -water dolomites involve pumping of © 2003 International Association of Sedimentologists large volumes of normal sea water or brines through the sediments (Adams & Rhodes, 1960; Carballo et 01., 1987; Vahrenkamp et 01., 1991; Swart & Melim, 2000; Melim & Scholle... ancient dolomite depDsits are associated with stromatolitic lime stones or organic-rich sediments (Valdiya, 1972; Gebelian & Hoffman, 1973; Montanez & Read, 1992; Montanez & Osleger, 1993; Wright, 1997), suggesting a possible mechanistic link to micro...

  11. Invertebrados asociados al coral constructor de arrecifes Pocillopora damicornis en Playa Blanca, Bahía Culebra, Costa Rica Invertebrates associated with the reef-building coral Pocillopora damicornis at Playa Blanca, Bahía Culebra, Costa Rica

    Directory of Open Access Journals (Sweden)

    Juan José Alvarado

    2012-04-01

    Full Text Available Los arrecifes coralinos son uno de los ecosistemas más diversos en el planeta, tanto por los organismos constructores como por aquellos que viven encima, sobre, dentro y debajo de ellos. Los corales del genero Pocillopora son reconocidos mundialmente por albergar una importante fauna de invertebrados entre sus ramas, los cuales son considerados como simbiontes obligatorios en una gran cantidad de casos. La presente investigación describe la fauna de invertebrados asociados al coral Pocillopora damicornis en Bahía Culebra, Costa Rica, describiendo sus densidades, frecuencias, riquezas y diversidades a través del tiempo. Para esto se colectaron 5 colonias cada 3-4 meses en Playa Blanca, Bahía Culebra. En total se encontraron 448 individuos en 35 especies, siendo Harpiliopsis depressa, Lithophaga aristata, Trapezia ferruginea, Alpheus lottini, Fennera chacei, y Petrolisthes haigae las especies predominantes. Noviembre fue el mes en el que se encontraron los mayores valores en los índices de riqueza, diversidad y diferenciación taxonómica, mientras que agosto fue el que presento los valores más bajos de todos. En términos generales, la época lluviosa mostro mayor riqueza de especies que la época seca. Así mismo, las especies colectados y los valores obtenidos son muy similares a otras zonas del Pacifico Oriental Tropical. Culebra ha venido sufriendo una perdida en la cobertura coralina, que podría tener consecuencias en la diversidad y abundancia de organismos asociados a corales. Estas consecuencias incluyen perdida en la fecundidad de estos organismos, una reducción en su función como limpiadores y protectores de depredadores del coral, poniendo en riesgo su diversidad, lo que puede afectar los stocks de peces depredadores que depende de ellos. Realizar monitoreos permanentes de la criptofauna asociada al coral Pocillopora va a ser determinante para cuantificar perdidas o recuperaciones en la composición de invertebrados asociados

  12. Nuevas adiciones a la fauna de crustáceos decápodos de Bahía Culebra, Guanacaste, Costa Rica

    Directory of Open Access Journals (Sweden)

    Rita Vargas-Castillo

    2012-04-01

    Full Text Available La fauna de crustáceos de Bahía Culebra, Guanacaste, Pacífico norte de Costa Rica, fue estudiada antes de la década de 1940. Basado en recolectas, principalmente de las últimas dos décadas y depositadas en el Museo de Zoología, Universidad de Costa Rica, se presentan aquí 15 nuevos registros de crustáceos decápodos pertenecientes a 11 familias. Estos registros se suman a las 94 especies conocidas previamente para la bahía, para un total de 109 especies de crustáceos decápodos y 130 de crustáceos. Probablemente hay más especies ya que algunos ambientes no han sido estudiados, como tampoco los microcrustáceos bénticos. Este tipo de estudio de línea base es importante especialmente en regiones donde se están dando alteraciones ambientales muy rápidas.New additions to the crustacean decapod fauna of Bahía Culebra, Guanacaste, Costa Rica. The crustacean fauna of Bahía Culebra, Guanacaste, north Pacific, Costa Rica, was studied before the 1940’s. Based on the collections, mainly of the last two decades, deposited in the Zoology Museum of the University of Costa Rica, 15 species of decapods crustaceans belonging in 11 families are added to the 94 species previously reported for Bahía Culebra. This results in a total of 109 decapod species, and 130 crustacean species for the bay. Probably more species are present since several environments of the bay have not been studied, as well as the benthic microcrustaceans. This type of baseline data studies are important because of the rapid changes taking place in Bahía Culebra.

  13. A Raman spectroscopic comparison of calcite and dolomite.

    Science.gov (United States)

    Sun, Junmin; Wu, Zeguang; Cheng, Hongfei; Zhang, Zhanjun; Frost, Ray L

    2014-01-03

    Raman spectroscopy was used to characterize and differentiate the two minerals calcite and dolomite and the bands related to the mineral structure. The (CO3)(2-) group is characterized by four prominent Raman vibrational modes: (a) the symmetric stretching, (b) the asymmetric deformation, (c) asymmetric stretching and (d) symmetric deformation. These vibrational modes of the calcite and dolomite were observed at 1440, 1088, 715 and 278 cm(-1). The significant differences between the minerals calcite and dolomite are observed by Raman spectroscopy. Calcite shows the typical bands observed at 1361, 1047, 715 and 157 cm(-1), and the special bands at 1393, 1098, 1069, 1019, 299, 258 and 176 cm(-1) for dolomite are observed. The difference is explained on the basis of the structure variation of the two minerals. Calcite has a trigonal structure with two molecules per unit cell, and dolomite has a hexagonal structure. This is more likely to cause the splitting and distorting of the carbonate groups. Another cause for the difference is the cation substituting for Mg in the dolomite mineral.

  14. Dolomite limits acidification of a biofilter degrading dimethyl sulphide

    Science.gov (United States)

    Smet; Van Langenhove H; Philips

    1999-01-01

    The applicability of dolomite particles to control acidification in a Hyphomicrobium MS3 inoculated biofilter removing dimethyl sulphide (Me2S) was studied. While direct inoculation of the dolomite particles with the liquid microbial culture was not successful, start-up of Me2S-degradation in the biofilter was observed when the dolomite particles were mixed with 33% (wt/wt) of Hyphomicrobium MS3-inoculated compost or wood bark material. Under optimal conditions, an elimination capacity (EC) of 1680 g Me2S m(-3) d(-1) was obtained for the compost/dolomite biofilter. Contrary to a wood bark or compost biofilter, no reduction in activity due to acidification was observed in these biofilters over a 235 day period because of the micro environment neutralisation of the microbial metabolite H2SO4 with the carbonate in the dolomite material. However, performance of the biofilter decreased when the moisture content of the mixed compost/dolomite material dropped below 15%. Next to this, nutrient limitation resulted in a gradual decrease of the EC and supplementation of a nitrogen source was a prerequisite to obtain a long-term high EC (> 250 g Me2S m(-3) d(-1)) for Me2S. In relation to this nitrogen supplementation, it was observed that stable ECs for Me2S were obtained when this nutrient was dosed to the biofilter at a Me2S-C/NH4Cl-N ratio of about 10.

  15. Biomineralization of dolomite and magnesite discovered in tropical coralline algae: a biological solution to the geological dolomite problem

    Directory of Open Access Journals (Sweden)

    M. C. Nash

    2011-06-01

    Full Text Available Dolomite is a magnesium-rich carbonate mineral abundant in fossil carbonate reef platforms but surprisingly rare in modern sedimentary environments, a conundrum known as the ''Dolomite Problem". Marine sedimentary dolomite has been interpreted to form by an unconfirmed, post-depositional diagenetic process, despite minimal experimental success at replicating this. Here we show that dolomite, accompanied by magnesite, forms within living crustose coralline alga, Hydrolithon onkodes, a prolific global tropical reef species. Chemical micro-analysis of the coralline skeleton reveals that not only are the cell walls calcitised, but that cell spaces are typically filled with magnesite, rimmed by dolomite, or both. Mineralogy was confirmed by X-ray diffraction. Thus there are at least three mineral phases present (magnesium calcite, dolomite and magnesite rather than one or two (magnesium calcite and brucite as previously thought. Our results are consistent with dolomite occurrences in coralline algae rich environments in fossil reefs. Instead of a theory of post-depositional dolomitisation, we present evidence revealing biomineralization that can account for the massive formations seen in the geologic record. Additionally, our findings imply that previously unrecognized dolomite and magnesite have formed throughout the Holocene. This discovery together with the scale of coralline algae dominance in past shallow carbonate environments raises the possibility that environmental factors driving this biological dolomitisation process have influenced the global marine magnesium/calcium cycle. Perhaps, most importantly, we reveal that what has been considered a geological process can be a biological process, having many implications for both disciplines.

  16. Mountain geomorphosites in Odle Group (Dolomites, Italy)

    Science.gov (United States)

    Coratza, Paola; Ghinoi, Alessandro; Marchetti, Mauro; Soldati, Mauro

    2016-04-01

    The area, considered in the present study, is located in the north-eastern sector of the Gardena valley, in the Odle Group, a popular destination of summer and winter tourism (more than 3000 m a.s.l.). The area has a strong hiking-tourism vocation thanks to its spectacular high-mountain landscape and a dense network of hiking tracks. The well-developed network of hiking paths and slopes for many different climbing skills offers a lot of possibilities for high-mountain excursions. Permanent dwelling-places are absent with the exceptions of a few tourist structures nearby opened during certain periods of the year. This area, as all Dolomites, which became UNESCO Word Heritage Site in 2009, represent landscape mosaics, which express the summation of landscape histories and processes offering an almost complete educational open-air laboratory due to the variety and complexity of phenomena and processes taking place during present climate conditions and during recent geological periods. These mountains, due to the aggregation of relict, recent and active landforms constitute an outstanding geoheritage, suitable for educational and tourist purposes. Landforms typical of past morphoclimatic conditions (inherited geomorphosites) share the stage with forms and processes active in the current morphoclimatic conditions (active geomorphosites); their spatial and geometrical relationships may be sufficient to trace a relative time-line of the geomorphological history of the area. Several glacial landforms testify for the presence and the activity of a glacial tongue hosted in the valley during the Lateglacial, mainly located in the northern sector of the area, where altitudes range from about 2000 m to about 2300 m a.s.l. Among these, worth of note are the well-preserved glacial cirques of Val dla Roa and those located at the southern margin of the Odle Group. Quite well preserved moraine ridges are present at a mean altitude of some 2000 m at the Alpe di Cisles as well as

  17. Invertebrados asociados al coral constructor de arrecifes Pocillopora damicornis en Playa Blanca, Bahía Culebra, Costa Rica

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    Juan José Alvarado

    2012-04-01

    Full Text Available Los arrecifes coralinos son uno de los ecosistemas más diversos en el planeta, tanto por los organismos constructores como por aquellos que viven encima, sobre, dentro y debajo de ellos. Los corales del genero Pocillopora son reconocidos mundialmente por albergar una importante fauna de invertebrados entre sus ramas, los cuales son considerados como simbiontes obligatorios en una gran cantidad de casos. La presente investigación describe la fauna de invertebrados asociados al coral Pocillopora damicornis en Bahía Culebra, Costa Rica, describiendo sus densidades, frecuencias, riquezas y diversidades a través del tiempo. Para esto se colectaron 5 colonias cada 3-4 meses en Playa Blanca, Bahía Culebra. En total se encontraron 448 individuos en 35 especies, siendo Harpiliopsis depressa, Lithophaga aristata, Trapezia ferruginea, Alpheus lottini, Fennera chacei, y Petrolisthes haigae las especies predominantes. Noviembre fue el mes en el que se encontraron los mayores valores en los índices de riqueza, diversidad y diferenciación taxonómica, mientras que agosto fue el que presento los valores más bajos de todos. En términos generales, la época lluviosa mostro mayor riqueza de especies que la época seca. Así mismo, las especies colectados y los valores obtenidos son muy similares a otras zonas del Pacifico Oriental Tropical. Culebra ha venido sufriendo una perdida en la cobertura coralina, que podría tener consecuencias en la diversidad y abundancia de organismos asociados a corales. Estas consecuencias incluyen perdida en la fecundidad de estos organismos, una reducción en su función como limpiadores y protectores de depredadores del coral, poniendo en riesgo su diversidad, lo que puede afectar los stocks de peces depredadores que depende de ellos. Realizar monitoreos permanentes de la criptofauna asociada al coral Pocillopora va a ser determinante para cuantificar perdidas o recuperaciones en la composición de invertebrados asociados

  18. Medusas (Cnidaria: Hydrozoa de una zona de afloramiento costero, Bahía Culebra, Pacífico, Costa Rica Medusae (Cnidaria: Hydrozoa from a coastal upwelling zone, Culebra Bay, Pacific, Costa Rica

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    Karina Rodríguez-Sáenz

    2012-12-01

    Full Text Available Las hidromedusas tienen un papel importante en redes tróficas marinas debido a sus hábitos alimenticios depredadores. Este es el primer estudio de este grupo del zooplancton gelatinoso en un area de afloramiento costero en América Central. Durante seis meses de 1999, se estudió la abundancia de hidromedusas en cuatro estaciones en Bahía Culebra, Golfo de Papagayo, costa Pacífica de Costa Rica (10º 37’N-85º40’W. Se identificó un total de 53 especies de las que 26 son registros nuevos para Costa Rica, 21 son registros nuevos para América Central y 8 son nuevos registros para el Pacífico Oriental Tropical. Las especies más abundantes durante el estudio (con más de 30% de la abundancia total fueron Liriope tetraphylla, Solmundella bitentaculata y Aglaura hemistoma. Seis especies se presentaron en todos los muestreos, 10 especies se presentaron únicamente durante la época seca y 17 se presentaron únicamente durante la época lluviosa. Se mostraron diferencias significativas entre las épocas lluviosa y seca. La máxima abundancia promedio de hidromedusas (2.1±4.3 ind./m³ fue encontrada durante las fechas que se espera el afloramiento costero, indicado por alta concentración de oxígeno y baja temperatura. La rica composición de especies encontrada en Bahía Culebra puede ser el resultado de varios factores, incluyendo la condición prístina de la bahía, el transporte de especies por la Contra Corriente Nor-Ecuatorial (NECC y los aportes de origen terrestre. Se incluyen ilustraciones de las 15 especies más importantes para facilitar su identificación y promover estudios futuros en la región.The hydromedusae have an important role in marine trophic webs due to their predatory feeding habits. This is the first study of this group of gelatinous marine zooplankton in a coastal upwelling area of Central America. The composition and abundance variability of hydromedusae were studied during six months in 1999 at four stations in

  19. The interaction of dolomite surfaces with metal impurities: a computer simulation study.

    Science.gov (United States)

    Austen, Kat F; Wright, Kate; Slater, Ben; Gale, Julian D

    2005-12-21

    This study investigates the behaviour of selected, morphologically important surfaces of dolomite (CaMg(CO3)2), using computational modelling techniques. Interatomic potential methods have been used to examine impurity substitution at cationic sites in these surfaces. Environmentally prevalent cations were studied to this end, namely Ni2+, Co2+, Zn2+, Fe2+, Mn2+ and Cd2+, all of which are also found as end-member carbonate minerals. Solid-solution substitution was investigated and showed that Cd and Mn will substitute from their end-member carbonate phase at either dolomite cation site. Mn is found to preferentially substitute at Mg sites, in agreement with experimental findings. For Ni2+, Co2+ and Zn2+, the magnitude of substitution energies is approximately equal for all surfaces, with the exception of the (1014) surface. However, for the larger cations, a far greater disparity in substitution energies is observed. At a stepped surface, analogous substitutions were performed and it was found that substitution energies for all impurity cations were reduced, indicating that uptake is more viable during growth. The predominant surface, the (1014), was solvated with a monolayer of water in order to investigate the influence of hydration on substitution energetics. The addition of water changes the relative preference for substitution of the different cations. Under aqueous conditions, the substitution energy is determined by three competing factors, the relative importance of which cannot be predicted without this type of computational investigation.

  20. Comparación intraespecífica de la conducta antidepredatoria de la culebra Thamnophis melanogaster

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    María del Rosario Sanabria Monroy

    2014-01-01

    Full Text Available Se explora la variación geográfica, ontogénica y sexual de la conducta antidepredatoria presentada en laboratorio de una culebra endémica de México. El diseño experimental no demostró que la conducta antidepredatoria fuera influida por la ontogenia, diferencias sexuales o geográficas, aunque el tamaño del cuerpo posiblemente sí la afecta. Se sugiere que la selección natural por depredación es similar en ambas poblaciones y entre sexos, pero posiblemente está sujeta a cambios ontogénicos en Cuitzeo, Michoacán.

  1. Ondas no lineales en la locomoción de las culebras Thamnophis melanogaster y Thamnophis eques

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    Javier Manjarrez Silva

    2013-01-01

    Full Text Available Se reportan los resultados experimentales comparados con los teóricos sobre la posible existencia de ondas no lineales solitónicas durante el desplazamiento de un ser vivo a través de la observación de la locomoción de huida terrestre de las culebras Thamnophis melanogaster y Thamnophis eques. En T. eques se encontró que el número total de puntos de contacto disminuyó al aumentar la velocidad y la longitud de onda, mientras que la amplitud de onda disminuyó. En el caso de T. melanogaster solo se encontró que el número total de puntos de contacto disminuyó conforme la velocidad aumentó; en contraste la amplitud y longitud de onda permanecían casi constantes.

  2. Thermodynamic Modelling of Dolomite Behavior in Aqueous Media

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    Tadeusz Michałowski

    2012-01-01

    Full Text Available The compact thermodynamic approach to the systems containing calcium, magnesium, and carbonate species is referred to dissolution of dolomite, as an example of nonequilibrium ternary salt when introduced into aqueous media. The study of dolomite is based on all attainable physicochemical knowledge, involved in expressions for equilibrium constants, where the species of the system are interrelated. The species are also involved in charge and concentration balances, considered as constraints put on a closed system, separated from the environment by diathermal walls. The inferences are gained from calculations performed with use of an iterative computer program. The simulated quasistatic processes occurred under isothermal conditions, started at a preassumed pH0 value of the solution where dolomite was introduced, and are usually involved with formation of other solid phases. None simplifying assumptions in the calculations were made.

  3. Self-diffusion of carbon and oxygen in dolomite.

    Science.gov (United States)

    Anderson, T. F.

    1972-01-01

    Self-diffusion of carbon and oxygen in dolomite was measured by isotopic exchange with CO2 at 645-785 C at 120-935 bars pressure. Several runs were also made with calcite under comparable experimental conditions. The principal findings of this study are that (1) the self-diffusion coefficients of both carbon and oxygen in dolomite are approximately 100 times larger than the values in calcite over the temperature range investigated and (2) oxygen self-diffusion in calcite is accelerated by high CO2 pressure.

  4. Mechanism of separating pyrite and dolomite by flotation

    Institute of Scientific and Technical Information of China (English)

    Anping Liu; Wen Ni; Wei Wu

    2007-01-01

    To study the mechanism of separating pyrite and dolomite by flotation, the acting mechanisms of WHL depressor and both the minerals were studied by means of thermogravimetric and differential thermal analysis (TG-DTA), Fourier transform infrareddiffuse reflection spectroscopy (FTIR-DRS), and X-ray photoelectron spectroscopy (XPS). The results indicated that WHL formed metal salts with metal ions dissolved in water from dolomite and pyrite, which then deposited on their surfaces. Both of the minerals could be depressed by WHL. In the process of flotation, sulfur was created besides the WHL being absorbed on the surface of the sulfur concentrate, and its recovery rate was slightly affected.

  5. Historia de la investigación marino-costera en Bahía Culebra, Pacífico Norte, Guanacaste, Costa Rica History of coastal-marine research in Bahía Culebra, North Pacific, Guanacaste, Costa Rica

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    Jorge Cortés

    2012-04-01

    Full Text Available Bahía Culebra está ubicada en la costa Pacífica norte de Costa Rica en una región de afloramiento estacional. En este trabajo presento la historia de la investigación marina en Bahía Culebra, para sintetizar lo que se ha hecho y resaltar lo que falta por investigar. Los organismos marinos de Bahía Culebra se empezaron a estudiar en la década de 1920 y muy intensamente en la década de 1930 con las expediciones de la Fundación Allan Hancock y de la Sociedad Zoológica de Nueva York. La mayor parte de la investigación marina se ha realizado desde la década de 1980 por investigadores y estudiantes del Centro de Investigación en Ciencias del Mar y Limnología (CIMAR de la Universidad de Costa Rica. Los ecosistemas mejor estudiados son las comunidades y arrecifes coralinos, seguido por las investigaciones sobre zooplancton. Se han publicado registros de 577 especies marinas en Bahía Culebra y se le suman 20 especies más con las publicadas en este Suplemento. Aún así, todavía falta estudiar varios ecosistemas y grupos de organismos. Es imperativo realizar esfuerzo para proteger y conservar los ecosistemas y biodiversidad marina de Bahía Culebra.History of coastal-marine research in Bahía Culebra, North Pacific, Guanacaste, Costa Rica. Bahía Culebra (Culebra Bay is located on the north Pacific coast of Costa Rica in a seasonal upwelling area. In this paper I present the history of marine research at Bahía Culebra, to summarize what is known and to point out research that should be carried out. Marine organisms of the Bay have been stud ied since the 1920’s and very intensely during the 1930’s, with the Alan Hancock Pacific Expeditions and the New York Society Zoological Expeditions. Most marine research has been done since 1980 by the Marine Science and Limnology Reseach Center (Centro de Investigación en Ciencias del Mar y Limnología, CIMAR at the University of Costa Rica. The best studied systems are the coral communities

  6. The Lawn Hill annulus: An Ordovician meteorite impact into water-saturated dolomite

    Science.gov (United States)

    Darlington, Vicki; Blenkinsop, Tom; Dirks, Paul; Salisbury, Jess; Tomkins, Andrew

    2016-12-01

    The Lawn Hill Impact Structure (LHIS) is located 250 km N of Mt Isa in NW Queensland, Australia, and is marked by a highly deformed dolomite annulus with an outer diameter of 18 km, overlying low metamorphic grade siltstone, sandstone, and shale, along the NE margin of the Georgina Basin. This study provides detailed field observations from sections of the Lawn Hill annulus and adjacent areas that demonstrate a clear link between the deformation of the dolomite and the Lawn Hill impact. 40Ar-39Ar dating of impact-related melt particles provides a time of impact in the Ordovician (472 ± 8 Ma) when the Georgina Basin was an active depocenter. The timing and stratigraphic thickness of the dolomite sequence in the annulus suggest that there was possibly up to 300 m of additional sedimentary rocks on top of the currently exposed Thorntonia Limestone at the time of impact. The exposed annulus is remarkably well preserved, with preservation attributed to postimpact sedimentation. The LHIS has an atypical crater morphology with no central uplift. The heterogeneous target materials at Lawn Hill were probably low-strength, porous, and water-saturated, with all three properties affecting the crater morphology. The water-saturated nature of the carbonate unit at the time of impact is thought to have influenced the highly brecciated nature of the annulus, and restricted melt production. The impact timing raises the possibility that the Lawn Hill structure may be a member of a group of impacts resulting from an asteroid breakup that occurred in the mid-Ordovician (470 ± 6 Ma).

  7. Diagenetic setting, dolomitization and reservoir characterization of Late Cretaceous Kawagarh Formation, Khanpur Dam section, Hazara, Pakistan

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    Maqsood Ur Rahman

    2016-12-01

    Full Text Available The Kawagarh Formation is well exposed in Hazara basin in different sections. Due to deep depositional settings, the Kawagarh Formation is least appealing to geologists to investigate it as a hydrocarbon reservoir. In the present study, the diagenetic settings of Kawagarh Formation were chronologically studied to interpret its diagenetic history and the effect of different diagenetic phases on the reservoir potential. The dolomitization is also studied in depth to use it as a key for its reservoir potential. Kawagarh Formation is sampled at Khanpur Dam Section for porosity analysis. The samples were taken from limestone and dolomite facies randomly. The dolomites are in the form of veins and well developed thick size beds. These dolomites are secondary in nature which is hosted by fractures and joints of limestone, which affect about 25% of limestone facies. At outcrop scale different types of dolomites are recognised on the basis of color and texture, yellowish fine-grained, brown blackish coarse-grained in the top portion and saddle dolomites. In petrographic study partial and complete dolomitization are observed. On the basis of crystal sizes and geometry different types of dolomites are recognized which are; (1 fine crystalline planar-euhedral dolomite, (2 medium crystalline planar-subhedral dolomite, (3 medium crystalline non-planar-anhedral dolomite, (4 coarse crystalline planar-subhedral dolomite, (5 coarse crystalline, non-planar-anhedral dolomite and (6 saddle dolomites (SD1. In petrographic study, high inclusions and disturbance are observed at the surfaces of dolomitic rhombs which indicate low Mg replacement or dedolomitization phenomena. On image J porosity analysis, the porosity is found of limestone and dolomitic samples. In limestone facies which is mostly, non-laminated mudstone has very low up to 2 to 3% in the form of vugs and fractures. In dolomitic facies, the porosity is ranging from 5% to 14%. In most of the dolomitic

  8. Avistamientos del delfín manchado, Stenella attenuata (Cetacea: Delphinidae en Bahía Culebra, Costa Rica, 1999-2000

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    Karina Rodríguez Sáenz

    2004-12-01

    Full Text Available Paralelo a un estudio de zooplancton (1999-2000, se hicieron observaciones a bordo de un bote inflable, sobre la presencia o ausencia de delfines a lo largo de un transecto (~8 km long en la parte central de Bahía Culebra (24 km² , Golfo de Papagayo. Se realizaron 34 muestreos en total y hubo avistamientos de delfines en 20 de ellos. La única especie de cetáceo observado en la Bahía fue el delfín manchado (Stenella attenuata. Estos avistamientos fueron más frecuentes durante la época lluviosa, en particular durante el mes de mayo de ambos años. La presencia de S. attenuata en Bahía Culebra podría estar asociada a la abundancia de presas potenciales como peces y moluscos (calamares, como se evidencia por las estadísticas pesqueras disponibles para la zona Pacífica de Costa RicaParallel to a zooplankton study (1999-2000 observations were made (from an inflatable boat, on the presence of dolphins along a transect (~8 km long on the axis of Culebra Bay (24 km² , Gulf of Papagayo, Pacific coast of Costa Rica. Dolphins were found during 20 of the 31 boat surveys conducted. The only species of cetacean found in the bay was Stenella attenuata, the spotted dolphin. These sightings were more frequent during the rainy season, particularly during the month of May of both years. The presence of S. attenuata in Culebra Bay might be associated to the abundances of fish and mollusks (their presumed prey: for example, squids, as evidenced by fishery statistics available for this zone of the Pacific coast of Costa Rica

  9. Relationship between fracturing and porogenesis in a carbonate reservoir: Example from the Middle Turonian Bireno Member in Jebel M'rhila, Central Tunisia

    Science.gov (United States)

    Haj Ali, Hajer; Belghithi, Hanen; Ouali, Jamel Abdennaceur; Touir, Jamel

    2016-09-01

    The aim of the present work is to study the Middle Turonian carbonate Bireno Member in Jebel M'rhila area (Central Tunisia). This member mainly consists of dolostones. The sampling of the dolomitic rocks was carried out on both sides of the several fractures affecting the Bireno Member. We also measured the directions and dips of the fractures. The Studied dolomites basically consist of subhedral to euhedral dolospar. The porosity associated to the dolomites show a gradual variation both laterally and vertically. In fact, porosity increases respectively, laterally while going toward the fractures and vertically from the bottom to the top of the dolomitic member. The mineralogical and geochemical analyses of dolomite, carried out respectively by X-Ray Diffraction and Atomic Absorption, show that the studied dolomites broadly range from a sub-stoechiometric dolomite (48% CaCO3) far from the fractures to a dolomitic calcite (84% CaCO3) near the fractures. In the same way, the MgCO3 contents vary from 35% to 11%. Such high contents in Ca against low contents in Mg could probably related to the dilution of the dolomitizing marine waters by meteoric waters which would have been introduced within the platform during the Middle Turonian sea-level fall and the subsequent subaerial exposure of the Bireno platform. The Sr and Na contents (respectively, 4 ppm and 15 ppm in average) are rather low and they gradually decrease while approaching the fractures. Such a gradual decrease in Sr and Na concentrations may be the result of salinity lowering caused by the meteoric waters that would have circulated through the existing fractures networks. The previous analyses were supplemented by the SEM examination of the dolomite and the measurement of porosity and permeability. The SEM allowed us to identify the dolomite petrographic phases and the associated diagenetic products (solution, cementing, dedolomitization.), whereas the porosity and permeability evaluation highlights the

  10. The mechanical and microstructural behaviour of calcite-dolomite composites: An experimental investigation

    OpenAIRE

    Kushnir, Alexandra R. l.; Kennedy, L. A.; Misra, Santanu; Benson, Philip; White, J C

    2015-01-01

    The styles and mechanisms of deformation associated with many variably dolomitized limestone shear systems are strongly controlled by strain partitioning between dolomite and calcite. Here, we present experimental results from the deformation of four composite materials designed to address the role of dolomite on the strength of limestone. Composites were synthesized by hot isostatic pressing mixtures of dolomite (Dm) and calcite powders (% Dm: 25%-Dm, 35%-Dm, 51%-Dm, and 75%-Dm). In all comp...

  11. First discovery of dolomite and magnesite in living coralline algae and its geobiological implications

    OpenAIRE

    M. C. Nash; Troitzsch, U; B. N. Opdyke; Trafford, J. M.; Russell, B. D.; Kline, D. I.

    2011-01-01

    Dolomite is a magnesium-rich carbonate mineral abundant in fossil carbonate reef platforms but surprisingly rare in modern sedimentary environments, a conundrum known as the "Dolomite Problem". Marine sedimentary dolomite has been interpreted to form by an unconfirmed, post-depositional diagenetic process, despite minimal experimental success at replicating this. Here we show that dolomite, accompanied by magnesite, forms within living crustose coralline alga, Hydrolithon onkodes<...

  12. PHOSPHORUS REMOVAL IN A VERTICAL FLOW CONSTRUCTED WETLAND USING DOLOMITE POWDER AND CHIPPINGS AS FILTER MEDIA

    OpenAIRE

    Gražina Žibienė; Midona Dapkienė; Jurgita Kazakevičienė; Algirdas Radzevičius

    2015-01-01

    Different kinds of natural and artificial filter media are able to retain phosphorus in the constructed wetlands. Due to the fact that the constructed wetland needs huge amounts of the filter media, it is very important to find locally available material which distinguishes itself by its ability to retain phosphorus. The materials found in Lithuania were considered and dolomite was chosen. Two dolomite fractions, dolomite powder (1–2 mm) and dolomite chippings (2–5 mm), and sand media were us...

  13. Sporicidal characteristics of heated dolomite powder against Bacillus subtilis spores.

    Science.gov (United States)

    Yasue, Syogo; Sawai, Jun; Kikuchi, Mikio; Nakakuki, Takahito; Sano, Kazuo; Kikuchi, Takahide

    2014-01-01

    Dolomite is a double salt composed of calcium carbonate (CaCO3) and magnesium carbonate (MgCO3). The heat treatment of CaCO3 and MgCO3 respectively generates calcium oxide (CaO) and magnesium oxide (MgO), which have antimicrobial activity. In this study, heated dolomite powder (HDP) slurry was investigated for its sporicidal activity against Bacillus subtilis ATCC 6633 spores. The B. subtilis spores used in this study were not affected by acidic (pH 1) or alkaline (pH 13) conditions, indicating that they were highly resistant. However, dolomite powder heated to 1000℃ for 1 h could kill B. subtilis spores, even at pH 12.7. Sporicidal activity was only apparent when the dolomite powder was heated to 800℃ or higher, and sporicidal activity increased with increases in the heating temperature. This temperature corresponded to that of the generation of CaO. We determined that MgO did not contribute to the sporicidal activity of HDP. To elucidate the sporicidal mechanism of the HDP against B. subtilis spores, the generation of active oxygen from HDP slurry was examined by chemiluminescence analysis. The generation of active oxygen increased when the HDP slurry concentration rose. The results suggested that, in addition to its alkalinity, the active oxygen species generated from HDP were associated with sporicidal activity.

  14. Gravity tectonics in the Northwestern Dolomites (N. Italy)

    NARCIS (Netherlands)

    Engelen, G.B.

    1963-01-01

    The NW Dolomites (see fig. 1 and 2) have an area of approximately 1500 sq. km and are situated on the southern flank of the east alpine mountain range. The region consists mainly of permo-triassic and some younger mesozoic strata with a maximal thickness of about 3000 m. This sedimentary series was

  15. Processes and controlling factors of polygenetic dolomite formation in the Transdanubian Range, Hungary: a synopsis

    Science.gov (United States)

    Haas, János; Hips, Kinga; Budai, Tamás; Győri, Orsolya; Lukoczki, Georgina; Kele, Sándor; Demény, Attila; Poros, Zsófia

    2016-06-01

    In the Transdanubian Range (Hungary), dolostone and dolomitic limestone appear in a number of sedimentary successions formed from the Late Permian to the Late Triassic in various depositional settings and under various diagenetic conditions, whereas only a negligible amount of dolomite was detected in the post-Triassic formations. Seven dolomite-bearing units representing ramp, small and large carbonate platforms, and intraplatform basin settings are presented in this synopsis. In most cases, multi-stage and polygenetic dolomitization was inferred. The main mass of the dolostones was formed via near-surface diagenetic processes, which were commonly preceded by the formation of synsedimentary dolomite. Accordingly, surficial conditions that prevailed during sediment deposition controlled the dolomite-forming processes and thus the lateral extension and the time span of dolomitization. The area of episodic subaerial exposure was a critical controlling factor of the lateral extension of the near-surface dolomite genesis, whereas its temporal extension was mostly governed by climate. Burial diagenesis usually resulted in only moderate dolomitization, either in connection with compactional fluid flow or via thermal convection. The Triassic fault zones provided conduits for fluid flow that led to both replacive dolomitization and dolomite cement precipitation. In the Late Triassic extensional basins, synsedimentary fault-controlled dolomitization of basinal deposits was reconstructed.

  16. Thermal decomposition of dolomite under CO2-air atmosphere

    Science.gov (United States)

    Subagjo, Wulandari, Winny; Adinata, Pratitis Mega; Fajrin, Anita

    2017-01-01

    This paper reports a study on thermal decomposition of dolomite under CO2-air. Calcination was carried out non-isothermally by using thermogravimetry analysis-differential scanning calorimetry (TGA-DSC) with a heating rate of 10°C/minute in an air atmosphere as well as 10 vol% CO2 and 90 vol% air atmosphere from 25 to 950°C. In addition, a thermodynamic modeling was also carried out to simulate dolomite calcination in different level of CO2-air atmosphere by using FactSage® 7.0. The the main constituents of typical dolomite from Gresik, East Java include MgCO3 (magnesite), CaCO3 (calcite), Ca(OH)2, CaO, MgO, and less than 1% of metal impurities. Based on the kinetics analysis from TGA results, it is found that non-isothermal dolomite calcination in 10 vol% CO2 atmosphere is occurred in a two-stage reaction; the first stage is the decomposition of magnesite at 650-740 °C with activation energy of 161.23 kJ/mol, and the second stage is the decomposition of calcite at 775-820 °C with activation energy of 162.46 kJ/mol. The magnesite decomposition is found to follow nucleation reaction mechanism of Avrami Eroveyef (A3), while calcite decomposition follows second order chemical reaction equation. Thermodynamic modeling supports these kinetic analyses. The results of this research give insight to the kinetics of dolomite decomposition in CO2-air atmosphere.

  17. Medusas (Cnidaria: Hydrozoa de una zona de afloramiento costero, Bahía Culebra, Pacífico, Costa Rica

    Directory of Open Access Journals (Sweden)

    Karina Rodríguez-Sáenz

    2012-12-01

    Full Text Available Las hidromedusas tienen un papel importante en redes tróficas marinas debido a sus hábitos alimenticios depredadores. Este es el primer estudio de este grupo del zooplancton gelatinoso en un area de afloramiento costero en América Central. Durante seis meses de 1999, se estudió la abundancia de hidromedusas en cuatro estaciones en Bahía Culebra, Golfo de Papagayo, costa Pacífica de Costa Rica (10º 37’N-85º40’W. Se identificó un total de 53 especies de las que 26 son registros nuevos para Costa Rica, 21 son registros nuevos para América Central y 8 son nuevos registros para el Pacífico Oriental Tropical. Las especies más abundantes durante el estudio (con más de 30% de la abundancia total fueron Liriope tetraphylla, Solmundella bitentaculata y Aglaura hemistoma. Seis especies se presentaron en todos los muestreos, 10 especies se presentaron únicamente durante la época seca y 17 se presentaron únicamente durante la época lluviosa. Se mostraron diferencias significativas entre las épocas lluviosa y seca. La máxima abundancia promedio de hidromedusas (2.1±4.3 ind./m³ fue encontrada durante las fechas que se espera el afloramiento costero, indicado por alta concentración de oxígeno y baja temperatura. La rica composición de especies encontrada en Bahía Culebra puede ser el resultado de varios factores, incluyendo la condición prístina de la bahía, el transporte de especies por la Contra Corriente Nor-Ecuatorial (NECC y los aportes de origen terrestre. Se incluyen ilustraciones de las 15 especies más importantes para facilitar su identificación y promover estudios futuros en la región.

  18. Islas de Puerto Rico y de Culebra: regularidades geomoríológicas de su relieve costero y submarino

    Directory of Open Access Journals (Sweden)

    José Ramón Hernández Santana

    2001-09-01

    Full Text Available The littoral s morphodynamic survey, its correlation with the main tectonic designs and the coastal morphc-structural analysis of Puerto Rico, and especially of the Culebra island, allowed to differentiate and assess the significant influence of island tectogénesis upon the configuration of geomorphological patterns at the land-sea interface as well as its submarine surroundings. The major tectogenetic peculiarities of island morphostructure and its littoral morpho-sculpture include: the morphotectonic alignment of small groups of islands as well as their internal morpho-sculptural features; the appearance and alignment of abrasive rock outcrop ranges; the littoral´s parallel and interrupted alignment; the tectonic control of the coastal configuration and its accidents derived from the orthogonal design of the prevailing NW-SE and NE-SW diagonal disjunctive systems; tombolos development by faulting parallel to the coastline and uprising of small contiguous island blacks; ample distribution of microbays and microinlets generated by a high faulting density and parallel transversal cracking, the diffusion of concave shell-shaped coasts of a cumulative and biogenic nature between discreet abrasive projections; and the presence of alternating horst and graben systems as a conditioning factor for the alternation of abrasive (ends, capes and promontories and cumulative coasts (beaches, marshes and mangroves or inlets and bays. This latter features is unique and determinant in coastal morpho-dynamics at western Puerto Rico and the Northern coast of Culebra island. Separately, this work includes the structural-geomorphic pattern of submarine relief of seas and oceans surrounding the Puerto Rico island, derived from the evolution of the major and most characteristic elements of the northern Caribbean´s earth crust. The principles of its typological classification differentiate the major structures within which morphogenetic complexes develop. At the

  19. Basic Data Report for Drillhole SNL-3 (C-2949)

    Energy Technology Data Exchange (ETDEWEB)

    Dennis W. Powers; Washington Regulatory and Environmental Services

    2005-01-20

    SNL-3 (permitted by the New Mexico State Engineer as C-2949) was drilled to provide geological data and hydrological testing of the Culebra Dolomite Member of the Permian Rustler Formation within a dissolution reentrant north of the WIPP site and well east of Livingston Ridge. SNL-3 is located in the southeast quarter of section 34, T21S, R31E, in eastern Eddy County, New Mexico. SNL-3 was drilled to a total depth of 970 ft below ground level (bgl). Below surface dune sand, SNL-3 encountered, in order, the Mescalero caliche, Gatuna, Dewey Lake, Rustler, and upper Salado Formations. Two intervals were cored: (1) from the lower Forty-niner Member through the Magenta Dolomite and into the upper Tamarisk Member; and (2) from the lower Tamarisk Member through the Culebra Dolomite and Los Meda?os Members and into the uppermost Salado.

  20. Water origin and flow pathways investigated by tracers in a small Dolomitic catchment

    Science.gov (United States)

    Penna, Daniele; Zuecco, Giulia; Cavalli, Marco; Trevisani, Sebastiano; Crema, Stefano; Pianezzola, Luisa; Dalla Fontana, Giancarlo; Marchi, Lorenzo; Borga, Marco

    2015-04-01

    Understanding runoff generation and water origin in mountain headwater catchments is often hampered by the superimposition of topographic, geomorphologic and hydrogeologic factors. Particularly, the complexity of catchments in Dolomitic regions is enhanced by karst processes that create preferential flow paths and make even more challenging to follow the water from its sources to the outlet. Environmental tracers, such as stable isotopes of water (18O and 2H) and electrical conductivity (EC), can help to unravel such a complexity. In this work, isotopic and EC measurements were used to i) identify the main end-members that contribute to streamflow, ii) quantify the role of snowmelt in spring water and surface runoff, and iii) assess the hydrological connection between runoff from springs and ephemeral water courses in rocky channels in the upper part, and surface and subsurface runoff in the lower part of a small Dolomitic catchment. The experimental activities were carried out in the 1.9 km2 Vauz Creek catchment, Dolomites, Central-Eastern Italian Alps. The elevation range is 1835-3152 m a.s.l.. Dolomite rocks prevail in the upper part of the catchment (above 2200 m a.s.l.), which is mostly non-vegetated. The lower sector, where mudstone, sandstone and marls outcrop, is covered by Alpine grassland and sparse trees. We took water samples for isotopic analyses roughly monthly from 2010 to 2014 in the lower part and from June to October 2011-2013 in the upper part of the catchment. We sampled precipitation (by rainfall collectors), snow (by snow corers), snowmelt (by snow lysimeters or by dripping snow patches), soil water (by suction cups) and, manually, stream water, spring water and groundwater in piezometric wells at different locations. Isotopic analyses were conducted by laser spectroscopy. EC was measured in the field with a portable meter. Results show a high variability in the tracer signature among the different sampled waters, reflecting the complex

  1. Hydrothermal recrystallization of the Lower Ordovician dolomite and its significance to reservoir in northern Tarim Basin

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Discovered in S15 and some other wells, the Lower Ordovician in the northern Tarim Basin consists mainly of brown gray-dark gray very fine-fine crystalline dolomite, with a minor portion of locally light gray-white medium-coarse crystalline dolomite. Silicification can be observed in the medium-coarse dolomite, and some euhedral drusy quartz can also be found in pores and fractures of the dolomite. The homogenization temperature of the fluid inclusions in the medium-coarse dolomite is between 110 and 200°C with maximum between 140 and 190°C, and the salinity is between 10.7 and 18.5 wt.% NaCl Eq. The homogenization temperature and salinity of the fluid inclusions in the medium-coarse dolomite are similar to those in the drusy quartz. Compared with the very fine-fine dolomite, the medium-coarse phase contains relatively high Fe and Mn. The average concentration of FeO and MnO in the medium-coarse dolomite is 1.917% and 0.323%, respectively. The medium-coarse dolomite has a remarkable negative Eu anomaly, consistent with the REE pattern of the intermediate-felsic igneous rocks in the Tarim Basin. The oxygen isotopic composition of the medium-coarse dolomite is relatively lighter than that of the very fine-fine dolomite. The δ18OPDB values of the medium-coarse dolomite are between -10.35‰ and -7.31‰. The δ18OSMOW values of the fluid associated with the medium-coarse dolomite can be calculated according to homogenization temperature and oxygen isotope fractionation factor between dolomite and fluid, and the calculated values are between +4‰ and +10‰, consistent with those of the hydrothermal fluid. The medium-coarse dolomite has relatively high 87Sr/86Sr ratios as well, indi- cating an origin associated with intermediate-felsic igneous rock. The homogenization temperature, element composition, REE pattern, oxygen and strontium isotopes demonstrate that the medium-coarse dolomite is the result of recrystallization of very fine-fine dolomite under

  2. First discovery of dolomite and magnesite in living coralline algae and its geobiological implications

    Directory of Open Access Journals (Sweden)

    M. C. Nash

    2011-11-01

    Full Text Available Dolomite is a magnesium-rich carbonate mineral abundant in fossil carbonate reef platforms but surprisingly rare in modern sedimentary environments, a conundrum known as the "Dolomite Problem". Marine sedimentary dolomite has been interpreted to form by an unconfirmed, post-depositional diagenetic process, despite minimal experimental success at replicating this. Here we show that dolomite, accompanied by magnesite, forms within living crustose coralline alga, Hydrolithon onkodes, a prolific global tropical reef species. Chemical micro-analysis of the coralline skeleton reveals that not only are the cell walls calcitised, but that cell spaces are typically filled with magnesite, rimmed by dolomite, or both. Mineralogy was confirmed by X-ray Diffraction. Thus there are at least three mineral phases present (magnesium calcite, dolomite and magnesite rather than one or two (magnesium calcite and brucite as previously thought. Our results are consistent with dolomite occurrences in coralline algae rich environments in fossil reefs of the last 60 million years. We reveal that the standard method of removing organic material prior to Xray Diffraction analysis can result in a decrease in the most obvious dolomite and magnesite diffraction patterns and this may explain why the abundant protodolomite and magnesite discovered in this study has not previously been recognized. This discovery of dolomite in living coralline algae extends the range of palaeo-environments for which biologically initiated dolomite can be considered a possible source of primary dolomite.

  3. First discovery of dolomite and magnesite in living coralline algae and its geobiological implications

    Science.gov (United States)

    Nash, M. C.; Troitzsch, U.; Opdyke, B. N.; Trafford, J. M.; Russell, B. D.; Kline, D. I.

    2011-11-01

    Dolomite is a magnesium-rich carbonate mineral abundant in fossil carbonate reef platforms but surprisingly rare in modern sedimentary environments, a conundrum known as the "Dolomite Problem". Marine sedimentary dolomite has been interpreted to form by an unconfirmed, post-depositional diagenetic process, despite minimal experimental success at replicating this. Here we show that dolomite, accompanied by magnesite, forms within living crustose coralline alga, Hydrolithon onkodes, a prolific global tropical reef species. Chemical micro-analysis of the coralline skeleton reveals that not only are the cell walls calcitised, but that cell spaces are typically filled with magnesite, rimmed by dolomite, or both. Mineralogy was confirmed by X-ray Diffraction. Thus there are at least three mineral phases present (magnesium calcite, dolomite and magnesite) rather than one or two (magnesium calcite and brucite) as previously thought. Our results are consistent with dolomite occurrences in coralline algae rich environments in fossil reefs of the last 60 million years. We reveal that the standard method of removing organic material prior to Xray Diffraction analysis can result in a decrease in the most obvious dolomite and magnesite diffraction patterns and this may explain why the abundant protodolomite and magnesite discovered in this study has not previously been recognized. This discovery of dolomite in living coralline algae extends the range of palaeo-environments for which biologically initiated dolomite can be considered a possible source of primary dolomite.

  4. Actinide Sorption in a Brine/Dolomite Rock System: Evaluating the Degree of Conservatism in Kd Ranges used in Performance Assessment Modeling for the WIPP Nuclear Waste Repository

    Science.gov (United States)

    Dittrich, T. M.; Reed, D. T.

    2015-12-01

    The Waste Isolation Pilot Plant (WIPP) near Carlsbad, NM is the only operating nuclear waste repository in the US and has been accepting transuranic (TRU) waste since 1999. The WIPP is located in a salt deposit approximately 650 m below the surface and performance assessment (PA) modeling for a 10,000 year period is required to recertify the operating license with the US EPA every five years. The main pathway of concern for environmental release of radioactivity is a human intrusion caused by drilling into a pressurized brine reservoir below the repository. This could result in the flooding of the repository and subsequent transport in the high transmissivity layer (dolomite-rich Culebra formation) above the waste disposal rooms. We evaluate the degree of conservatism in the estimated sorption partition coefficients (Kds) ranges used in the PA based on an approach developed with granite rock and actinides (Dittrich and Reimus, 2015; Dittrich et al., 2015). Sorption onto the waste storage material (Fe drums) may also play a role in mobile actinide concentrations. We will present (1) a conceptual overview of how Kds are used in the PA model, (2) technical background of the evolution of the ranges and (3) results from batch and column experiments and model predictions for Kds with WIPP dolomite and clays, brine with various actinides, and ligands (e.g., acetate, citrate, EDTA) that could promote transport. The current Kd ranges used in performance models are based on oxidation state and are 5-400, 0.5-10,000, 0.03-200, and 0.03-20 mL g-1 for elements with oxidation states of III, IV, V, and VI, respectively. Based on redox conditions predicted in the brines, possible actinide species include Pu(III), Pu(IV), U(IV), U(VI), Np(IV), Np(V), Am(III), and Th(IV). We will also discuss the challenges of upscaling from lab experiments to field scale predictions, the role of colloids, and the effect of engineered barrier materials (e.g., MgO) on transport conditions. Dittrich

  5. Neutron activation analysis of multimetallic accumulation in dolomites

    Directory of Open Access Journals (Sweden)

    Zovko Emira

    2008-01-01

    Full Text Available The reason for exploring polymetallic ores, which are found in dolomite structures of the Veovača and Borovica zone near Vareš, lies in the fact that there is very little information about its chemical structure. The isolated concentrates that we analyzed from surface mines, have shown significant difference in quantity of trace elements. Deep probing of the whole area was not performed, but there are presumptions that there are roots of ore-rich dolomites in the areas of 30 - 40 km. The future concept of exploitation of these mines in the Vareš zone would probably require deeper probing. There are prospects for finding higher quality deposits with significant quantities of polymetallic components. By the method of neutron activation analysis the existence of mercury in amounts of about 0.4 % was confirmed. Because of the presence of mercury, these concentrates are not appropriate for pyrometallurgy, since it may result in environment contamination.

  6. Order–disorder–reorder process in thermally treated dolomite samples

    DEFF Research Database (Denmark)

    Zucchini, Azzurra; Comodi, Paola; Katerinopoulou, Anna;

    2012-01-01

    A combined powder and single-crystal X-ray diffraction analysis of dolomite [CaMg(CO3)2] heated to 1,200oC at 3 GPa was made to study the order–disorder–reorder process. The order/disorder transition is inferred to start below 1,100oC, and complete disorder is attained at approximately 1,200o...

  7. Fluid inclusion and isotopic evidence on dolomitization, Devonian of Western Canada

    Energy Technology Data Exchange (ETDEWEB)

    Aulstead, K.L.; Spencer, R.J.; Krouse, H.R. (Univ. of Calgary, Alberta (Canada))

    1988-05-01

    The Presqu'ile and Manetoe Facies are diagenetic features developed in Lower and Middle Devonian Formations of the Elk Point Basin (Presqu'ile) and the Mackenzie Shelf (Manetoe). Both facies contain coarsely crystalline dolomite and white sparry dolomite cement. Less extensive diagenetic phases, in order of paragenesis, include fluorite, anhydrite, barite, calcite, quartz, sphalerite and galena. Conditions of dolomitization are outlined from core and outcrop examination, thin section and cathodoluminescent petrography, fluid inclusion analyses, and C and O isotopic data. Fluid inclusion and stable isotope analyses from dolomite are combined to determine the isotopic composition of the dolomitizing fluids. Chemical analyses of fluid inclusion waters are compared with formation water analyses to derive a proposed origin for the diagenetic fluids. Dolomite formed from hot, high salinity fluids early in the diagenetic history of the basin. Limestone was dolomitized as a result of the same process that created white sparry dolomite cement in the Manetoe Facies. Remnants of the dolomitizing fluids are present as formation waters in some Devonian formations in Alberta. Subsequent invasion of meteoric waters produced more dilute diagenetic fluids which resulted in the precipitation of calcite and quartz cement in the Manetoe Facies. These fluids are present in fluid inclusions and are responsible for the low {sup 18}O content of the calcite cement. The temperatures of calcite and quartz formation differ as a function of burial depth within the Manetoe Facies during the Mesozoic and Cenozoic, while the temperature of formation for dolomite does not.

  8. Hydrothermal dolomites in SW Sardinia (Italy): evidence for a widespread late-Variscan fluid flow event

    Science.gov (United States)

    Boni, M.; Parente, G.; Bechstädt, T.; De Vivo, B.; Iannace, A.

    2000-03-01

    Epigenetic replacive and saddle dolomite, frequently forming zebra structures (Geodic dolomite), affected Cambrian limestones and early diagenetic dolomites across large areas of the Iglesiente-Sulcis mining district (SW Sardinia, Italy). The dolomite crops out in an area of more than 500 km 2 and reaches a thickness of up to 600 m (or even more). This rock represents one of the most extensive dolomites of epigenetic origin yet documented. Prior to dolomitization, the Cambrian carbonates underwent ductile deformation and greenschist facies metamorphism. The same is true for the overlying tectonic nappes. Fluid inclusion analysis combined with O- and Sr-isotope data indicate that the dolomitizing fluid can be categorized as a "basinal brine". The spread in homogenization temperatures shows a gradient with values decreasing from east to west. The higher temperatures (mean of around 100°C) have been measured in eastern parts of the Iglesiente area, whereas the lowermost temperatures (mean of about 85°C) have been found along the western coast of Iglesiente. This fluid certainly can neither have come directly from the low-grade metamorphic lithotypes undergoing dolomitization, nor from the low-temperature metamorphic rocks within the overlying nappes. It is assumed that a late-Variscan hydrothermal event, which coincided with extensional tectonics, set brine circulation into motion. Dolomitization may have occurred within circulation cells, which were driven by high heat flow. Fluids originated in the underlying rocks and circulated upward to affect the overlying Cambrian carbonates. An alternative model is that the dolomitization was caused by hydrothermal brines that originated within basinal areas of the Variscan orogenic pile circulating deep within the crust, and ascended in the External Zone (Iglesiente-Sulcis). Whatever the origin, these reducing saline fluids, which carried radiogenic Sr, dolomitized a large volume of Early Paleozoic rocks. The many

  9. Physical factors contributing to the benthic dominance of the alga Caulerpa sertularioides (Caulerpaceae, Chlorophyta in the upwelling Bahía Culebra, north Pacific of Costa Rica

    Directory of Open Access Journals (Sweden)

    Cindy Fernández-García

    2012-04-01

    Full Text Available Caulerpa sertularioides has been spreading in Bahía Culebra, a seasonal upwelling bay in the north Pacific of Costa Rica, since 2001. The survey was carried out from December 2003 to March 2005, in several locations around Bahía Culebra, located inside the Gulf of Papagayo. This study investigated spatial and temporal patterns, percent coverage, monthly growth rate, reproductive adaptations, and morphological variations of frond length and stolon diameter of Caulerpa sertularioides, at different environmental physical and chemical factors at the bay. The alga extended to depths of 23 m on a variety of substrates. The stolons extended quickly, with a maximum growth rate of 31.2 cm month-1. This alga grows mainly by fragmentation of its fronds and stolons; nevertheless it can also reproduce sexually by releasing gametes in the water column. These two modes of spreading promote the adaptation of this opportunistic species to environmental, chemical, and physical changes at this bay. At the same time the alga showed variations in the length of its fronds and stolons, adapting to conditions such as depth and season. Average percent cover and frond density increased during the dry season when the upwelling of nutrients and cold water occurs. In the rainy season the average percent cover and frond density decreased; however there was a peak in September, when high precipitation resulted in runoff into the bay of nutrient-rich waters. The morphological and physiological plasticity of C. sertularioides, in synergy with its predominant clonal propagation and sexual reproduction provided this species with a great adaptability to changes in temperature and nutrient concentration at Bahía Culebra.

  10. Patrones espaciales de la riqueza específica de las culebras Thamnophis en México Spatial patterns of species richness of garter snakes Thamnophis in Mexico

    OpenAIRE

    Crystian Sadiel Venegas-Barrera; Javier Manjarrez

    2011-01-01

    Se identificaron tanto las áreas de mayor riqueza específica de las culebras del género Thamnophis y su presencia en las provincias biogeográficas y las Regiones Terrestres Prioritarias (RTP), como los factores antropogénicos que pueden influir en su distribución. Con la combinación de mapas de distribución potencial de las especies se creó un mapa de riqueza específica para calcular el porcentaje de celdas ocupadas por el género dentro de cada provincia biogeográfica, de cada RTP y conocer e...

  11. Third Jesús Culebras Lecture - Molecular biology and clinical nutrition; where do we stand and where do we go?

    Science.gov (United States)

    Gil, Angel

    2013-01-01

    Nutrition plays a fundamental role in the maintenance of health and the treatment of disease, and serves as the crossroads for many disciplines. Biochemistry and Molecular Biology represents a key brand of science to ascertain the mechanism of action of nutrients and other food bioactive compounds in health and disease. The aim of the present Jesús M. Culebras lecture is to consider the future of the relationships between Molecular Biology and Clinical Nutrition and to discuss the use of molecular and genetic tools to study molecular responses to dietary factors and the metabolic consequences of food and to consider major challenges on human nutrition sciences in the 21(st) century. Particular emphasis is given to the identification and use of novel biomarkers in inflammatory diseases. Likewise, the importance of the human microbiome and how microorganisms can be safely utilized in the prevention and management of infectious and chronic diseases are discussed. Moreover, the key role of nutrigenetics, nutrigenomics and epigenetics in the new era of nutrition is considered. Nutrigenetics refers to the role of DNA sequence variation in the responses to nutrients, whereas nutrigenomics is the study of the role of nutrients in gene expression. Epigenetics is the study of mitotically heritable alterations in gene expression potential that are not caused by DNA sequence alterations. In the past decade, it has increasingly been recognized that dysregulation of epigenetic mechanisms may play an important role in human disease. Indeed, there is increasing interest in epigenetic mechanisms underlying phenotype modification modulated by nutrients. Further research in those areas should contribute to evaluate functionality of specific nutrients and bioactive compounds in Clinical Nutrition and allow personalized nutritional advice.

  12. Assessing the Incidence of Ciguatera Fish Poisoning with Two Surveys Conducted in Culebra, Puerto Rico, during 2005 and 2006

    Science.gov (United States)

    Luber, George; Conklin, Laura; Tosteson, Thomas R.; Granade, Hudson R.; Dickey, Robert W.; Backer, Lorraine C.

    2012-01-01

    Background: Although ciguatera fish poisoning (CFP) is the most common seafood intoxication worldwide, its burden has been difficult to establish because there are no biomarkers to diagnose human exposure. Objective: We explored the incidence of CFP, percentage of CFP case-patients with laboratory-confirmed ciguatoxic meal remnants, cost of CFP illness, and potential risk factors for CFP. Methods: During 2005 and again during 2006, we conducted a census of all occupied households on the island of Culebra, Puerto Rico, where locally caught fish are a staple food. We defined CFP case-patients as persons with gastrointestinal symptoms (abdominal pain, vomiting, diarrhea, or nausea) and neurological symptoms (extremity paresthesia, arthralgia, myalgia, malaise, pruritus, headache, dizziness, metallic taste, visual disturbance, circumoral paresthesia, temperature reversal, or toothache) or systemic symptoms (e.g., bradycardia) within 72 hr of eating fish during the previous year. Participants were asked to save fish remnants eaten by case-patients for ciguatoxin analysis at the Food and Drug Administration laboratory in Dauphin Island, Alabama (USA). Results: We surveyed 340 households during 2005 and 335 households during 2006. The estimated annual incidence of possible CFP was 4.0 per 1,000 person-years, and that of probable CFP was 7.5 per 1,000 person-years. One of three fish samples submitted by probable case-patients was positive for ciguatoxins. None of the case-patients required respiratory support. Households that typically consumed barracuda were more likely to report CFP (p = 0.02). Conclusions: Our estimates, which are consistent with previous studies using similar case findings, contribute to the overall information available to support public health decision making about CFP prevention. PMID:22275728

  13. SELECTED CHARACTERISTICS OF LIMESTONE AND DOLOMITE RESERVOIRS IN THE UNITED STATES.

    Science.gov (United States)

    Schmoker, James W.; Krystinik, Katherine B.; Halley, Robert B.

    1985-01-01

    Limestone reservoirs are more numerous in the United States than dolomite reservoirs (by a ratio of about 3 to 1) because limestones are more abundant than dolomite. However, in the eight states that account for over 90% of United States carbonate reservoirs, there is a statistical tendency for carbonate reservoirs to occur preferentially in dolomites. Dolomite reservoirs, on the average, are larger and deeper than those of limestone, yet they often have lower matrix porosities and permeabilities. This line of investigation offers supplemental evidence that dolomitization tends to improve the reservoir properties of a given formation, and that effective fracture systems at reservoir depths are more likely to occur in dolomites than in limestones. Refs.

  14. Growth and subsidence of carbonate platforms: numerical modelling and application to the Dolomites, Italy

    Directory of Open Access Journals (Sweden)

    A. Bosellini

    2004-06-01

    Full Text Available The phenomenon of subsidence induced by the growth of carbonate platforms has been investigated with the aid of numerical modelling. The research aimed to quantify the relative contribution of this process in the creation of the accommodation space required to pile up thick neritic bodies. We analysed two end-member deformation styles, namely the elastic behaviour of the lithosphere when locally loaded and the plastic-like reaction of a sedimentary succession underlying a growing carbonate buildup. The former process, analysed using a modified flexural model, generates a regional subsidence. In contrast, the latter process, simulated by considering the compaction occurring in soft sediments, generates a local subsidence. We attempted to quantify the amount and distribution of subsidence occurring below and surrounding an isolated platform and in the adjacent basin. The major parameters playing a role in the process are discussed in detail. The model is then applied to the Late Anisian-Early Ladinian generation of carbonate platforms of the Dolomites, Northern Italy, where they are spectacularly exposed. Taking also into account the Tertiary shortening that occurred in the area, both local and regional subsidence contributions of major platform bodies have been calculated aimed at a reconstruction of the map of the induced subsidence. A major outcome of this study is that the accommodation space, that allowed the accumulation of very thick shallow-water carbonate successions in the Dolomites, was only partially due to lithospheric stretching while the contribution given by the 'local' overload is as high as 20-40% of the total subsidence. Our results also shed some light on the water-depth problem of the Triassic basins as well as on the basin-depth to platform-thickness relationships.

  15. Surface chemistry allows for abiotic precipitation of dolomite at low temperature

    OpenAIRE

    Roberts, Jennifer A.; Kenward, Paul A.; Fowle, David A.; Goldstein, Robert H.; Luis A. González; Moore, David S.

    2013-01-01

    Abundant in the geologic record, but scarce in modern environments below 50 °C, the mineral dolomite is used to interpret ancient fluid chemistry, paleotemperature, and is a major hydrocarbon reservoir rock. Because laboratory synthesis of abiotic dolomite had been unsuccessful, chemical mechanisms for precipitation are poorly constrained, and limit interpretations of its occurrence. Here we report the abiotic synthesis of dolomite at 25 °C, and demonstrate that carboxylated surfaces on organ...

  16. Dolomitized cells within chert of the Permian Assistência Formation, Paraná Basin, Brazil

    Science.gov (United States)

    Calça, Cléber P.; Fairchild, Thomas R.; Cavalazzi, Barbara; Hachiro, Jorge; Petri, Setembrino; Huila, Manuel Fernando Gonzalez; Toma, Henrique E.; Araki, Koiti

    2016-04-01

    Dolomitic microscopic structures in the form of microspheres, "horseshoe- shaped" objects, and thin botryoidal crusts found within microfossiliferous chert within stromatolites of the Evaporite Bed (EB) of the Permian Assistência Formation, Irati Subgroup, Paraná Basin, Brazil, have been investigated by means of optical microscopy, X-ray fluorescence, scanning electron microscopy, Raman spectrometry and energy-dispersive X-ray spectrometry. The microspheres were identified as dolomitized coccoidal cyanobacteria based on similarity in size, spheroidal and paired hemispheroidal morphologies and colonial habit to co-occurring silicified organic-walled cyanobacteria embedded within the same microfabric and rock samples. The co-occurrence of dolomite, pyrite framboids, and abundant dispersed carbonaceous material and silicified cells is consistent with a hypersaline depositional environment with abundant cyanobacterial mats and elevated Mg2 +/Ca2 + ratios and reducing conditions with active anoxic microbial processes near the water-(bio)sediment interface. The abundance of extracellular polymeric substances facilitated anoxic microbial processes (sulfate reduction), providing essential conditions for possible primary microbially induced dolomitization. In most of the dolomitized cells dolomite occurs only as an external layer; in fully dolomitized cells magnesium is richest in the outermost layer. Presumably, the dolomitization process was favored by the presence of anoxic microbial degraders and negatively charged functional groups at the surface of the cyanobacterial cells. Botryoidal dolomite rims of silica-filled fenestrae formed by a similar process and inherited the botryoidal morphology of the cell as originally lining the fenestrae. Silicification interrupted the dolomitization of the largely organic biosediment, mostly by permineralization, but locally by substitution, thereby preserving not only dolomitic microspheres, but also huge numbers of structurally

  17. Microtextural Characteristics and Origin of Dolomites in the Tepearasi Formation, SW of Beysehir-Konya, Turkey

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The Tepearasi Formation of the autochthonous Geyikdagi Group in the Central Tauride Belt, SE of Beysehir, is Dogger in age and consists dominantly of massive limestones and greyish dolomites occurring within the middle to upper sections. The total thickness of the dolomitic levels ranges from 100–300 m and laterally extends 500–700 m. Three types of dolomite were distinguished through petrographic analyses: homogeneous, mottled (saddle-crystalline) and joint-filling dolomite, which were interpreted to have formed in two different stages, early diagenetic and late diagenetic. The homogeneous dolomite of the early diagenetic stage is light-coloured and monotonous-textured and shows the form of a dolosparite mosaic. The mottled dolomite formed in the late diagenetic stage is light- to dark-coloured and coarsely granular idiomorphic. The other type of late diagenetic dolomite, described as the joint-filling type, presents a crystal growth pattern from the joint walls towards the centre of the joint space. It is associated with coarse calcite crystals as well as primary dolomite crystal clasts which were formed in the early diagenetic stage. In addition to these characteristics, cataclastic texture indicating the influence of tectonism is also observed. Microtexture-oriented scanning electron microscopy (SEM) studies indicate that mottled dolomites show zonal structures and contain secondary dissolution vugs. SEM studies also revealed the existence of some remains (calcite, clay etc.) in joint-filling dolomites. Analyses by energy dispersive spectrometry (EDS) indicate the existence of clay minerals (likely to be illite) in the pores of dolomite. Isotope studies conducted to shed light onto the origin of the dolomites of the Tepearasi Formation yielded the results of ?18O= –2.48 to – 3.87‰ and ?13C=0.93 to 1.12‰ for the early diagenetic homogeneous dolomites. Mottled and joint-filling type dolomites of the late diagenetic stage, on the other hand, gave the

  18. Relationship between karstification and burial dolomitization in Permian platform carbonates (Lower Khuff - Oman)

    Science.gov (United States)

    Beckert, Julia; Vandeginste, Veerle; John, Cédric M.

    2016-08-01

    Large breccia fabrics associated with karst constitute an important structure in massive limestone successions. The dimensions and shapes of breccia structures are controlled by the initial fracture pattern of the limestone and preferential pathways of the karstifying fluids, but subsequently breccia fabrics can also govern the migration of later fluids. Therefore, breccias are highly relevant features to capture for reservoir characterisation. Outcrop analogues for Lower Khuff units in the Middle East present in the Central Oman Mountains reveal brecciated fabrics up to 10s of metres in diameter. These brecciated units are closely associated with dolomite bodies of late diagenetic origin. Based on an integrated set of data, the breccias are interpreted as collapsed karst cavities either formed by meteoric or hypogenic fluids. The exact origin of the fluids could not be constrained due to an overprint by later dolomitizing fluids. Based on the composition of the clasts and matrix in the breccias, two dolomitization events are interpreted to have affected the succession, one prior to (early diagenetic [ED] dolomite) and one after brecciation (late diagenetic [DT2] dolomite). Dolomite of shallow burial origin (ED dolomite) was only observed as clasts within breccia and is much more frequent than late diagenetic (medium to deep burial) dolomite clasts. Thus, the timing of the brecciation and collapse is assumed to postdate shallow burial early diagenetic dolomitization. Late diagenetic replacive dolomite (DT2 dolomite) forms 90% of the matrix in the breccia fabrics with the exception of a small area that was not affected by dolomitization, but is rarely present as clasts. Stable isotope measurements [δ18O: - 2.5‰ to - 6‰ VPDB and δ13C: 2.9‰ to 4.8‰ VPDB] suggest a burial origin for the late diagenetic dolomite potentially with the participation of hydrothermal fluids. The dolomitized matrix indicates a migration of late dolomitizing fluids subsequent to or

  19. High salinity facilitates dolomite precipitation mediated by Haloferax volcanii DS52

    Science.gov (United States)

    Qiu, Xuan; Wang, Hongmei; Yao, Yanchen; Duan, Yong

    2017-08-01

    Although most modern dolomites occur in hypersaline environments, the effects of elevated salinity on the microbial mediation of dolomite precipitation have not been fully evaluated. Here we report results of dolomite precipitation in association with a batch culture of Haloferax volcanii DS52, a halophilic archaeon, under various salinities (from 120‰ to 360‰) and the impact of salinity on microbe-mediated dolomite formation. The mineral phases, morphology and atomic arrangement of the precipitates were analyzed by XRD, SEM and TEM, respectively. The amount of amino acids on the archaeal cell surface was quantified by HPLC/MS. The XRD analysis indicated that disordered dolomite formed successfully with the facilitation of cells harvested from cultures with relatively high salinities (200‰ and 280‰) but was not observed in association with cells harvested from cultures with lower salinity (120‰) or the lysates of cells harvested from extremely high salinity (360‰). The TEM analysis demonstrated that the crystals from cultures with a salinity of 200‰ closely matched that of dolomite. Importantly, we found that more carboxyl groups were presented on the cell surface under high salinity conditions to resist the high osmotic pressure, which may result in the subsequent promotion of dolomite formation. Our finding suggests a link between variations in the hydro-chemical conditions and the formation of dolomite via microbial metabolic activity and enhances our understanding about the mechanism of microbially mediated dolomite formation under high salinity conditions.

  20. Preparation and Characterization of Malaysian Dolomites as a Tar Cracking Catalyst in Biomass Gasification Process

    Directory of Open Access Journals (Sweden)

    M. A. A. Mohammed

    2013-01-01

    Full Text Available Three types of local Malaysian dolomites were characterized to investigate their suitability for use as tar-cracking catalysts in the biomass gasification process. The dolomites were calcined to examine the effect of the calcination process on dolomite’s catalytic activity and properties. The modifications undergone by dolomites consequent to thermal treatment were investigated using various analytical methods. Thermogravimetric and differential thermal analyses indicated that the dolomites underwent two stages of decomposition during the calcination process. The X-ray diffraction and Fourier-transform infrared spectra analyses showed that thermal treatment of dolomite played a significant role in the disappearance of the CaMg(CO32 phase, producing the MgO-CaO form of dolomite. The scanning electron microscopy microphotographs of dolomite indicated that the morphological properties were profoundly affected by the calcination process, which led to the formation of a highly porous surface with small spherical particles. In addition, the calcination of dolomite led to the elimination of carbon dioxide and increases in the values of the specific surface area and average pore diameter, as indicated by surface area analysis. The results showed that calcined Malaysian dolomites have great potential to be applied as tar-cracking catalysts in the biomass gasification process based on their favorable physical properties.

  1. Effect of SO2 Dry Deposition on Porous Dolomitic Limestones

    Science.gov (United States)

    Olaru, Mihaela; Aflori, Magdalena; Simionescu, Bogdana; Doroftei, Florica; Stratulat, Lacramioara

    2010-01-01

    The present study is concerned with the assessment of the relative resistance of a monumental dolomitic limestone (Laspra – Spain) used as building material in stone monuments and submitted to artificial ageing by SO2 dry deposition in the presence of humidity. To investigate the protection efficiency of different polymeric coatings, three commercially available siloxane-based oligomers (Lotexan-N, Silres BS 290 and Tegosivin HL 100) and a newly synthesized hybrid nanocomposite with silsesquioxane units (TMSPMA) were used. A comparative assessment of the data obtained in this study underlines that a better limestone protection was obtained when treated with the hybrid nanocomposite with silsesquioxane units.

  2. Effect of SO2 Dry Deposition on Porous Dolomitic Limestones

    Directory of Open Access Journals (Sweden)

    Florica Doroftei

    2010-01-01

    Full Text Available The present study is concerned with the assessment of the relative resistance of a monumental dolomitic limestone (Laspra – Spain used as building material in stone monuments and submitted to artificial ageing by SO2 dry deposition in the presence of humidity. To investigate the protection efficiency of different polymeric coatings, three commercially available siloxane-based oligomers (Lotexan-N, Silres BS 290 and Tegosivin HL 100 and a newly synthesized hybrid nanocomposite with silsesquioxane units (TMSPMA were used. A comparative assessment of the data obtained in this study underlines that a better limestone protection was obtained when treated with the hybrid nanocomposite with silsesquioxane units.

  3. Modern marine dolomite cement in a north Jamaican fringing reef

    Energy Technology Data Exchange (ETDEWEB)

    Mitchell, J.T.; Land, L.S.; Miser, D.E.

    1987-06-01

    Minor quantities of ordered dolomite (..delta../sup 18/O = +2.0 per thousand PDB; composition = Ca/sub 1.22/Mg/sub 0.78/ (CO/sub 3/)/sub 2/) have formed from near-normal seawater in a subtidal hardground as part of a modern fringing coral reef. Crystals 5 ..mu..m in diameter precipitated within the past 1.8 ka in the form of syntaxial fringes on Mg-calcite marine cements and skeletal allochems. The crystals have a fine modulated microstructure and c reflections, both apparently formed during crystal growth

  4. Using in situ REE analysis to study the origin and diagenesis of dolomite of Lower Paleozoic, Tarim Basin

    Institute of Scientific and Technical Information of China (English)

    WANG XiaoLin; JIN ZhiJun; HU WenXuan; ZHANG JunTao; QIAN YiXiong; ZHU JingQuan; LI Qing

    2009-01-01

    In situ REE concentrations of various dolomites from Tarim Basin were obtained by LA-ICP-MS analysis, and the data were normalized to standard seawater (Seawater Normalized=SWN). Most of the samples have a ΣREE range of less than 20 ppm. All samples show similar REE distributions with heavy REE depletion, and positive Ce anomaly, which indicates that they have the same dolomitization fluids (seawater). According to the origin and diagenetic process of dolomite, two types of dolomite are de-termined and described as follows: 1) syndepositional dolomite, with the highest REE concentrations (more than 20 ppm), the cores of which are more enriched in REE compared with their cortexes, indicating that they underwent the dolomitization of calcareous sediments by hypersaline and subsequent diagenesis decreased the REE content of the cortex because of the low REE concentration of the diagenetic fluids; 2) diagenetic dolomite, which can be subdivided into four groups. (1) burial dolomite which has higher REE concentrations than limestone, but lower than syndepositional dolomite. This shows that pore fluids with high salinity dolomitized the pre-existing limestone; (2) void filling dolomite which has the similar REE patterns with the matrix dolomite. In addition, the Eu anomaly is not obvious, suggesting that the dolomitization fluids originated from the diagenetic fluids; (3) recrystallized dolomite, whose REE concentration was obviously decreased, indicating that the REE concentration was decreased during the recrystallization processes; and (4) hydrothermal altered void-filling dolomite, which has the lowest REE concentration, but obvious positive Eu anomaly, reflecting its hydrothermal activity related origin. Thus, the diverse REE signatures, which were recorded in different dolomites, retain the information of their formation conditions and subsequent diagenetic processes. In situ REE analysis of dolomite is an effective probe into the origin and diagenetic process of

  5. Using in situ REE analysis to study the origin and diagenesis of dolomite of Lower Paleozoic,Tarim Basin

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    In situ REE concentrations of various dolomites from Tarim Basin were obtained by LA-ICP-MS analysis,and the data were normalized to standard seawater(Seawater Normalized=SWN).Most of the samples have a ΣREE range of less than 20 ppm.All samples show similar REESWN distributions with heavy REE depletion,and positive Ce anomaly,which indicates that they have the same dolomitization fluids(seawater).According to the origin and diagenetic process of dolomite,two types of dolomite are determined and described as follows:1) syndepositional dolomite,with the highest REE concentrations(more than 20 ppm),the cores of which are more enriched in REE compared with their cortexes,indicating that they underwent the dolomitization of calcareous sediments by hypersaline and subsequent diagenesis decreased the REE content of the cortex because of the low REE concentration of the diagenetic fluids;2) diagenetic dolomite,which can be subdivided into four groups.(1) burial dolomite which has higher REE concentrations than limestone,but lower than syndepositional dolomite.This shows that pore fluids with high salinity dolomitized the pre-existing limestone;(2) void filling dolomite which has the similar REE patterns with the matrix dolomite.In addition,the Eu anomaly is not obvious,suggesting that the dolomitization fluids originated from the diagenetic fluids;(3) recrystallized dolomite,whose REE concentration was obviously decreased,indicating that the REE concentration was decreased during the recrystallization processes;and(4) hydrothermal altered void-filling dolomite,which has the lowest REE concentration,but obvious positive Eu anomaly,reflecting its hydrothermal activity related origin.Thus,the diverse REE signatures,which were recorded in different dolomites,retain the information of their formation conditions and subsequent diagenetic processes.In situ REE analysis of dolomite is an effective probe into the origin and diagenetic process of dolomite.

  6. Dolomitization and sedimentary cyclicity of the Ordovician, Silurian, and Devonian rocks in South Estonia

    Directory of Open Access Journals (Sweden)

    Kallaste, Toivo

    2006-03-01

    Full Text Available The distribution and composition of dolomitized rocks and stoichiometry of dolomite in southern Estonia in the Ordovician, Silurian, and Devonian were studied on the background of the facies, sedimentary cyclicity (nine shallowing-up cycles, and evolution of the palaeobasins. The composition of rocks and lattice parameters of dolomite were investigated using the X-ray diffraction, X-ray fluorescence, titration and gravimetric analyses, and porosity measurements. The formation of dolostones is directly determined by the cyclic evolution of palaeobasins. Dolomitized rocks belong to the shallow-water inner shelf or tidal/lagoonal facies belt of regressive phases of sedimentary cycles. Sediments of the deep shelf/transitional environment and transgressive phases are not dolomitized. The most stoichiometric is secondary replacive dolomite of Silurian and upper Ordovician dolostones, formed during the early diagenesis of normal-marine (saline shallow-shelf calcitic sediments. The content of insoluble residue does not affect the stoichiometry. The changes in lattice parameters are induced by the Ca/Mg ratio in the dolomite lattice. The dolomite of the dolostones contacting limestone or containing calcite has an expanded lattice. The primary (syngenetic dolostone of the lagoonal or tidal flat belt has also an expanded lattice. No dolomitizing effect of the waters of the Devonian palaeobasin on the underlying rocks was revealed. The whole data set of the studied dolostones is consistent with the marine water environment in the palaeobasin at the corresponding time and shows no sign of the inflow of external fluids. It suggests that the microbial model of dolomite formation may characterize the Ordovician, Silurian, and Devonian in southern Estonia. The occurrence of dolostones between undolomitized rocks limits the time of dolomitization to the early diagenetic stage.

  7. Dolomite flotation of high magnesium phosphate ores using fatty acid soap collectors

    Science.gov (United States)

    Gu, Zhengxing

    The separation of dolomite from apatite has been recognized as one of the most difficult subjects in mineral processing due to the similarities in their physiochemical properties. In this study, selective surfactants were used with a fatty acid soap collector to improve the flotation performance of separating dolomite from high magnesium phosphate ores. Three surfactants, diethyl phthalate (DP), Tween-80 (TW) and derivative of sulfonate salt (DSS1) were used. Hallimond cell flotation was conducted using pure dolomite sample to determine the effects of various factors including dosages, particle size, Ca2+ ions and slimes on the dolomite flotation recovery. The results showed that the surfactants can significantly improve dolomite flotation performance by increasing collecting ability and tolerating the effect of calcium ions and slime contents. The stirrer-tank cell batch flotation tests were carried out using two natural high magnesium phosphate ore samples containing 3.3% and 1.5% MgO. The test results showed that the surfactant DP could improve dolomite flotation at low dosages, and DSS1 could enhance the separation of dolomite from phosphate by improving both collecting ability and flotation selectivity. When 10% of DSS1 was used with the fatty acid soap as collector, at least 10% more dolomite can be removed with less P2O5 loss. The effectiveness of the surfactant DSS1 in enhancing dolomite flotation was further demonstrated in modified packed column flotation with natural dolomitic phosphate ore sample. The addition of the surfactant DSS1 into fatty acid soap collector could improve its frothability and froth stability, and reduce the bubble size. It has been found that the dolomite flotation performance has a close relationship with the frothability and froth stability of the collector.

  8. Frictional properties of simulated anhydrite-dolomite fault gouge and implications for seismogenic potential

    NARCIS (Netherlands)

    Pluymakers, A.M.H.; Niemeijer, A.R.; Spiers, C.J.

    2016-01-01

    The frictional properties of anhydrite-dolomite fault gouges, and the effects of CO2 upon them, are of key importance in assessing the risks associated with CO2 storage in reservoir formations capped by anhydrite-dolomite sequences, and in understanding seismicity occurring in such formations (such

  9. Surface chemistry allows for abiotic precipitation of dolomite at low temperature.

    Science.gov (United States)

    Roberts, Jennifer A; Kenward, Paul A; Fowle, David A; Goldstein, Robert H; González, Luis A; Moore, David S

    2013-09-03

    Although the mineral dolomite is abundant in ancient low-temperature sedimentary systems, it is scarce in modern systems below 50 °C. Chemical mechanism(s) enhancing its formation remain an enigma because abiotic dolomite has been challenging to synthesize at low temperature in laboratory settings. Microbial enhancement of dolomite precipitation at low temperature has been reported; however, it is still unclear exactly how microorganisms influence reaction kinetics. Here we document the abiotic synthesis of low-temperature dolomite in laboratory experiments and constrain possible mechanisms for dolomite formation. Ancient and modern seawater solution compositions, with identical pH and pCO2, were used to precipitate an ordered, stoichiometric dolomite phase at 30 °C in as few as 20 d. Mg-rich phases nucleate exclusively on carboxylated polystyrene spheres along with calcite, whereas aragonite forms in solution via homogeneous nucleation. We infer that Mg ions are complexed and dewatered by surface-bound carboxyl groups, thus decreasing the energy required for carbonation. These results indicate that natural surfaces, including organic matter and microbial biomass, possessing a high density of carboxyl groups may be a mechanism by which ordered dolomite nuclei form. Although environments rich in organic matter may be of interest, our data suggest that sharp biogeochemical interfaces that promote microbial death, as well as those with high salinity may, in part, control carboxyl-group density on organic carbon surfaces, consistent with origin of dolomites from microbial biofilms, as well as hypersaline and mixing zone environments.

  10. Effect of dolomite oral exposure in Wistar rats during organogenesis period of pregnancy.

    Science.gov (United States)

    Lagarto, Alicia; Bellma, Addis; Tillán, Juana; Gabilondo, Tatiana; Guerra, Isbel; Ocanto, Zuleira; Couret, Micaela; González, Ricardo

    2008-09-01

    The potential of oral exposure to dolomite, a natural product that contains calcium and magnesium, to initiate teratogenesis was analyzed in Wistar rats. Animals received dolomite oral dosages of 500 and 1500mg/kg during the period of gestation from day 6-15 post conceptionem (p.c.). Maternal, embryo and fetal toxicity were evaluated. Dolomite exposure did not produce maternal toxicity assessed by clinical observations, body weight gain, hematology parameters and relative organs weight. Signs of embryo-fetal toxicity were not observed. Skeletal malformations and visceral variations were similar in control and dolomite-treated groups. On the other hand, slight increase was observed in fetal body weight in the dolomite-treated group. Treatment with dolomite resulted in significantly decreased incidences of unossified xiphisternum, incomplete ossification of xiphisternum and sternebrae. These effects could be caused by a beneficial influence of calcium and magnesium salts present in dolomite on ossification process. In conclusion, in this study we found that the oral exposure to rats of up to 1500mg/kg of dolomite during organogenesis did not induce significant maternal and embryo-fetal toxicity.

  11. Dolomite supplementation improves bone metabolism through modulation of calcium-regulating hormone secretion in ovariectomized rats.

    Science.gov (United States)

    Mizoguchi, Toshihide; Nagasawa, Sakae; Takahashi, Naoyuki; Yagasaki, Hiroshi; Ito, Michio

    2005-01-01

    Dolomite, a mineral composed of calcium magnesium carbonate (CaMg (CO3)2), is used as a food supplement that supplies calcium and magnesium. However, the effect of magnesium supplementation on bone metabolism in patients with osteoporosis is a matter of controversy. We examined the effects of daily supplementation with dolomite on calcium metabolism in ovariectomized (OVX) rats. Dolomite was administered daily to OVX rats for 9 weeks. The same amount of magnesium chloride as that supplied by the dolomite was given to OVX rats as a positive control. Histological examination revealed that ovariectomy decreased trabecular bone and increased adipose tissues in the femoral metaphysis. Dolomite or magnesium supplementation failed to improve these bone histological features. Calcium content in the femora was decreased in OVX rats. Neither calcium nor magnesium content in the femora in OVX rats was significantly increased by dolomite or magnesium administration. Urinary deoxypyridinoline excretion was significantly increased in OVX rats, and was not affected by the magnesium supplementation. Serum concentrations of magnesium were increased, and those of calcium were decreased, in OVX rats supplemented with dolomite or magnesium. However, there was a tendency toward decreased parathyroid hormone secretion and increased calcitonin secretion in OVX rats supplemented with dolomite or magnesium. Serum 1,25-dihydroxyvitamin D(3) and osteocalcin levels were significantly increased in the supplemented OVX rats. These results suggest that increased magnesium intake improves calcium metabolism in favor of increasing bone formation, through the modulation of calcium-regulating hormone secretion.

  12. Carbon dioxide absorption and release properties of pyrolysis products of dolomite calcined in vacuum atmosphere.

    Science.gov (United States)

    Wang, Fei; Kuzuya, Toshihiro; Hirai, Shinji; Li, Jihua; Li, Te

    2014-01-01

    The decomposition of dolomite into CaO and MgO was performed at 1073 K in vacuum and at 1273 K in an Ar atmosphere. The dolomite calcined in vacuum was found to have a higher specific surface area and a higher micropore volume when compared to the dolomite calcined in the Ar atmosphere. These pyrolysis products of dolomite were reacted with CO2 at 673 K for 21.6 ks. On the absorption of CO2, the formation of CaCO3 was observed. The degree of absorption of the dolomite calcined in vacuum was determined to be above 50%, which was higher than the degree of absorption of the dolomite calcined in the Ar atmosphere. The CO2 absorption and release procedures were repeated three times for the dolomite calcined in vacuum. The specific surface area and micropore volume of calcined dolomite decreased with successive repetitions of the CO2 absorption and release cycles leading to a decrease in the degree of absorption of CO2.

  13. Presence of sulfate does not inhibit low-temperature dolomite precipitation

    Science.gov (United States)

    Sánchez-Román, Mónica; McKenzie, Judith A.; de Luca Rebello Wagener, Angela; Rivadeneyra, Maria A.; Vasconcelos, Crisógono

    2009-07-01

    The hypothesis that sulfate inhibits dolomite formation evolved from geochemical studies of porewaters from deep-sea sedimentary sequences and has been tested with hydrothermal experiments. We examined the sulfate inhibition factor using aerobic culture experiments with Virgibacillus marismortui and Halomonas meridiana, two moderately halophilic aerobic bacteria, which metabolize independent of sulfate concentration. The culture experiments were conducted at 25 and 35 °C using variable SO 42- concentrations (0, 14, 28 and 56 mM) and demonstrate that halophilic aerobic bacteria mediate direct precipitation of dolomite with or without SO 42- in the culture media which simulate dolomite occurrences commonly found under the Earth's surface conditions. Hence, we report that the presence of sulfate does not inhibit dolomite precipitation. Further, we hypothesize that, if sedimentary dolomite is a direct precipitate, as in our low-temperature culture experiments, the kinetic factors involved are likely to be quite different from those governing a dolomite replacement reaction, such as in hydrothermal experiments. Consequently, the occurrence and, presumably, growth of dolomite in SO 42--rich aerobic cultures may shed new light on the long-standing Dolomite Problem.

  14. Substrate pH and butterfly bush response to dolomitic lime or steel slag amendment

    Science.gov (United States)

    Steel slag is a fertilizer amendment with a high concentration of calcium oxide, and thus capable of raising substrate pH similar to dolomitic lime. Steel slag, however, contains higher concentrations of some nutrients, such as iron, manganese, and silicon, compared to dolomitic lime. The objectiv...

  15. Tectonics of the crystalline Basement of the Dolomites in North Italy

    NARCIS (Netherlands)

    Agterberg, F.P.

    1961-01-01

    The present thesis deals with a number of crystalline regions around the Dolomites in North Italy. The geographic position is shown on sheet I, which is depicted in fig. 105. The Dolomites proper consist mainly of Permotriassic, overlying a transgression plane, which cuts off the studied crystalline

  16. Physical factors contributing to the benthic dominance of the alga Caulerpa sertularioides (Caulerpaceae, Chlorophyta in the upwelling Bahía Culebra, north Pacific of Costa Rica

    Directory of Open Access Journals (Sweden)

    Cindy Fernández-García

    2012-04-01

    Full Text Available Caulerpa sertularioides has been spreading in Bahía Culebra, a seasonal upwelling bay in the north Pacific of Costa Rica, since 2001. The survey was carried out from December 2003 to March 2005, in several locations around Bahía Culebra, located inside the Gulf of Papagayo. This study investigated spatial and temporal patterns, percent coverage, monthly growth rate, reproductive adaptations, and morphological variations of frond length and stolon diameter of Caulerpa sertularioides, at different environmental physical and chemical factors at the bay. The alga extended to depths of 23 m on a variety of substrates. The stolons extended quickly, with a maximum growth rate of 31.2 cm month-1. This alga grows mainly by fragmentation of its fronds and stolons; nevertheless it can also reproduce sexually by releasing gametes in the water column. These two modes of spreading promote the adaptation of this opportunistic species to environmental, chemical, and physical changes at this bay. At the same time the alga showed variations in the length of its fronds and stolons, adapting to conditions such as depth and season. Average percent cover and frond density increased during the dry season when the upwelling of nutrients and cold water occurs. In the rainy season the average percent cover and frond density decreased; however there was a peak in September, when high precipitation resulted in runoff into the bay of nutrient-rich waters. The morphological and physiological plasticity of C. sertularioides, in synergy with its predominant clonal propagation and sexual reproduction provided this species with a great adaptability to changes in temperature and nutrient concentration at Bahía Culebra.Desde el 2001 se ha observado una propagación del alga verde Caulerpa sertularioides en Bahía Culebra, zona de afloramiento costero, en el Pacífico norte de Costa Rica. El muestreo se llevó acabo entre Diciembre 2003 a marzo 2005, en varias localidades de Bah

  17. 3D-Mapping of Dolomitized Structures in Lower Cambrian Phosphorites

    Science.gov (United States)

    Hippler, Dorothee; Stammeier, Jessica A.; Brunner, Roland; Rosc, Jördis; Franz, Gerhard; Dietzel, Martin

    2016-04-01

    Dolomitization is a widespread phenomenon in ancient sedimentary rocks, particularly close to the Precambrian-Cambrian boundary. Dolomite can form in synsedimentary or hydrothermal environments, preferentially via the replacement of solid carbonate precursor phases. Synsedimentary dolomite formation is often associated with microbial activity, such as bacterial sulfate reduction or methanogenesis. In this study, we investigate dolomitic phosphorites from the Lowermost Cambrian Tal Group, Mussoori Syncline, Lesser Himalaya, India, using micro-CT 3D-mapping, in order to unravel the complex diagenetic history of the rocks. The selected sample shows alternating layering of phosphatic mudstones and sparitic dolostone, in which brecciated layers of phosphorite or phosphatic mudstones are immersed in a dolomite-rich matrix. Lamination occurs on a sub-millimetre scale, with lamination sometimes wavy to crinkly. This fabric is interpreted as former microbial mats, providing the environment for early diagenetic phosphatization. Preliminary electron backscatter imaging with scanning microscopy revealed that dolomite crystals often occur in spherical to ellipsoidal structures, typically with a high porosity. This dolomite is associated with botryoidal apatite, organic matter and small amounts of calcite. Micro-CT 3D-mappings reveal that dolomite structures are cigar-shaped, elongated and up to 600 μm long. They are further arranged in a Mikado-like oriented framework spanning a layer thickness of a few millimetres. Analyses of ambient pore space, with similar elongated outlines and filled with organic matter, suggest a potential coherence of ambient pore space and shape of the dolomite structures. Allowing for other associated mineral phases, such as pyrite and silicates, and their spatial distribution, the present approach can be used to unravel distinct diagenetic reaction pathways, and might thus constrain the proxy potential of these Lower Cambrian dolomitic phosphorites

  18. Re-evaluation of temperature of replacement dolomitization in the Triassic Latemar platform with clumped isotope thermometry

    Science.gov (United States)

    Müller, Inigo Andreas; Rodriguez-Blanco, Juan D.; Storck, Julian-Christopher; Benning, Liane G.; Wilson, Edith N.; Brack, Peter; Bernasconi, Stefano M.

    2017-04-01

    The Triassic Latemar platform shows different types of dolomitization styles including features such as dolomitized zones around basaltic dykes and patchy reddish or greyish dolomitization features in the central part of the platform. The processes leading to this partial dolomitization are still debated. Different geochemical tools were applied to determine the formation temperature of the patchy dolomite phases, thereby microthermometry on fluid inclusions and clumped isotope thermometry revealed significantly different temperature ranges (100 to 200 °C vs. 40 to 80 °C, from Wilson et al., 1990 and Ferry et al., 2011, respectively). We re-evaluated the origin of these patchy dolomites at Latemar using a new dolomite-specific clumped isotope temperature calibration based on dolomites synthetized in the laboratory at different temperatures. We directly compare the clumped isotope temperatures of patchy dolomites from Latemar with those obtained on the same samples by fluid inclusion microthermometry. With the new dolomite specific clumped isotope temperature calibration it is possible to determine more precisely the dolomite formation temperature and the oxygen isotope composition of the fluid source. Both are critical parameters for better constraining the origin of different dolomite fabrics on the Earth's surface and in ancient sediments. E.N. Wilson, L.A. Hardie and O.M. Phillips, 1990. Dolomitization front geometry, fluid flow patterns, and the origin of massive dolomite: the Triassic Latemar buildup, northern Italy. American Journal of Science 290, 741-796. J.M. Ferry, B.H. Passey, C. Vasconcelos and J.M. Eiler, 2011. Formation of dolomite at 40-80 °C in the Latemar carbonate buildup, Dolomites, Italy, from clumped isotope thermometry. Geology 39, 571-574.

  19. Desulfovibrio brasiliensis sp. nov., a moderate halophilic sulfate-reducing bacterium from Lagoa Vermelha (Brazil) mediating dolomite formation.

    Science.gov (United States)

    Warthmann, Rolf; Vasconcelos, Crisogono; Sass, Henrik; McKenzie, Judith A

    2005-06-01

    A novel halotolerant sulfate-reducing bacterium, Desulfovibrio brasiliensis strain LVform1, was isolated from sediments of a dolomite-forming hypersaline coastal lagoon, Lagoa Vermelha, in the state of Rio de Janeiro, Brazil. The cells are vibrio-shaped and 0.30 to 0.45 microm by 1.0 to 3.5 microm in size. These bacteria mediate the precipitation of dolomite [CaMg(CO3)2] in culture experiments. The strain was identified as a member of the genus Desulfovibrio in the delta-subclass of the Proteobacteria on the basis of its 16S rRNA gene sequence, its physiological and morphological properties. Strain LVform1 is obligate sodium-dependent and grows at NaCl concentrations of up to 15%. The 16S rRNA sequence revealed that this strain is closely related to Desulfovibrio halophilus (96.2% similarity) and to Desulfovibrio oxyclinae (96.8% similarity), which were both isolated from Solar Lake, a hypersaline coastal lake in the Sinai, Egypt. Strain LVform1 is barotolerant, growing under pressures of up to 370 bar (37 MPa). We propose strain LVform1 to be the type strain of a novel species of the genus Desulfovibrio, Desulfovibrio brasiliensis (type strain LVform1 = DSMZ No. 15816 and JCM No. 12178). The GenBank/EMBL accession number for the 16S rDNA sequence of strain LVform1 is AJ544687.

  20. Biofacies evolution in the Triassic platforms of the Dolomites, Italy

    Directory of Open Access Journals (Sweden)

    Franco Russo

    2005-10-01

    Full Text Available The Triassic of the Dolomites includes many carbonate platform generations, ranging in age from the Anisian to the Norian-Rhaetian. After the Permian-Triassic biological crisis, “reef” communities reappeared during the Anisian time. These buildups were generally characterized by a limited relief, lacking any primary skeletal framework and evidence of syndepositional cementation. The microfacies are dominated by micrites, mainly allochthonous or detrital in origin. The sparse biota are generally binder and buffler organisms, such as dasycladacean algae, sphinctozoans and briozoans.The second generation of carbonate buildups (late Anisian–early Ladinian, Sciliar Fm are dominated by syndepositional cements (e.g. Marmolada Platform. These cements represent the main component of margin and upper slope facies. They form more or less isolated or laterally linked bodies: the “evinosponges”. During the late Ladinian and Carnian p.p., the post-volcanic platforms developed (Cassian Dolomite. The microfacies of these platforms manly consist of micrites, cements and skeletons. The automicrites constitute more than 50% of the rock volume, the cements the 20%, and the skeletal organisms less than the 10%. The metazoan contribution is subordinated to that of skeletal cyanobacteria, like Cladogirvanella cipitensis and microproblematica, like Tubyphites. The primary marine cements provide evidence of a widespread early syndepositional lithification. Towards the top of Julian Substage (Carnian, at the base of the Heiligkreutz/Dürrenstein Formation (i.e. Alpe di Specie, small calcareous bioconstructions, interpreted as patch-reefs, show a much more “modern” faunal association. For the first time in the Triassic, a primary skeletal framework developed, largely formed by calcified demosponges and scleractinians. Corals were still subordinated to sponges. Taxonomic diversity increases greatly and the skeletal component exceeds the 50% of the rock volume

  1. Large sized fast and optimizing drilling in Culebra Block%大尺寸复合钻井优快技术

    Institute of Scientific and Technical Information of China (English)

    谢福龙; 高思洋

    2015-01-01

    Culebra block is located in Amazon basin,where long open hole directional wells dominate featuring low stability,poor cutting transportation and slow drilling speed. A large sized fast and optimizing drilling is developed in this paper in terms of these issues to improve the mechanical drilling rate in this block.%Culebra区块位于亚马逊盆地,该地区多为长裸眼大尺寸定向井,普遍存在井壁稳定性差、岩屑携带不及时、机械钻速低等技术难题.本文对culebra区块大尺寸钻井难点进行分析,提出一套大尺寸优快钻井技术,从而达到提高机械钻速的目的.

  2. Kinetic and Thermodynamic Studies on the Phosphate Adsorption Removal by Dolomite Mineral

    Directory of Open Access Journals (Sweden)

    Xiaoli Yuan

    2015-01-01

    Full Text Available The efficiency of dolomite to remove phosphate from aqueous solutions was investigated. The experimental results showed that the removal of phosphate by dolomite was rapid (the removal rate over 95% in 60 min when the initial phosphate concentration is at the range of 10–50 mg/L. Several kinetic models including intraparticle diffusion model, pseudo-first-order model, Elovich model, and pseudo-second-order model were employed to evaluate the kinetics data of phosphate adsorption onto dolomite and pseudo-second-order model was recommended to describe the adsorption kinetics characteristics. Further analysis of the adsorption kinetics indicated that the phosphate removal process was mainly controlled by chemical bonding or chemisorption. Moreover, both Freundlich and Langmuir adsorption isotherms were used to evaluate the experimental data. The results indicated that Langmuir isotherm was more suitable to describe the adsorption characteristics of dolomite. Maximum adsorption capacity of phosphate by dolomite was found to be 4.76 mg phosphorous/g dolomite. Thermodynamic studies showed that phosphate adsorption was exothermic. The study implies that dolomite is an excellent low cost material for phosphate removal in wastewater treatment process.

  3. Precipitation of low-temperature dolomite from an anaerobic microbial consortium: the role of methanogenic Archaea.

    Science.gov (United States)

    Kenward, P A; Goldstein, R H; González, L A; Roberts, J A

    2009-12-01

    Here we report precipitation of dolomite at low temperature (30 degrees C) mediated by a mixed anaerobic microbial consortium composed of dissimilatory iron-reducing bacteria (DIRB), fermenters, and methanogens. Initial solution geochemistry is controlled by DIRB, but after 90 days shifts to a system dominated by methanogens. In live experiments conditions are initially saturated with respect to dolomite (Omega(dol) = 19.40) and increase by two orders of magnitude (Omega(dol) = 2 330.77) only after the onset of methanogenesis, as judged by the increasing [CH(4)] and the detection of methanogenic micro-organisms. We identify ordered dolomite in live microcosms after 90 days via powder X-ray diffraction, while sterile controls precipitate only calcite. Scanning electron microscopy and transmitted electron microscopy demonstrate that the precipitated dolomite is closely associated with cell walls and putative extra-cellular polysaccharides. Headspace gas measurements and denaturing gradient gel electrophoresis confirm the presence of both autotrophic and acetoclastic methanogens and exclude the presence of DIRB and sulfate-reducing bacteria after dolomite begins forming. Furthermore, the absence of dolomite in the controls and prior to methanogenesis confirm that methanogenic Archaea are necessary for the low-temperature precipitation of dolomite under the experimental conditions tested.

  4. Molecular characterization of endolithic cyanobacteria inhabiting exposed dolomite in central Switzerland.

    Science.gov (United States)

    Sigler, William V; Bachofen, Reinhard; Zeyer, Josef

    2003-07-01

    The phototrophic microbial community inhabiting exposed dolomite in the alpine Piora Valley (Switzerland) forms a distinct endolithic bilayer that features adjacent red dolomite (exterior) and green dolomite (interior) layers that are c. 0.5-1 mm below the rock surface. Characterization of the community, with an emphasis on cyanobacteria, was conducted with culture-dependent and -independent approaches. Direct microscopy of green dolomite revealed four distinct morphotypes consistent with Chlorophyta genera Chlorella and Stichococcus and the Cyanobacterial genera Nostoc and Calothrix, whereas only Stichococcus and Nostoc were observed in the red dolomite. Enrichment in BG-11 media resulted in the growth of Chlorella and Stichococcus. Denaturing gradient gel electrophoresis (DGGE) analysis of DNA extracted from the enrichment revealed two dominant phylotypes with sequence similarity to Chlorella osrokiniana chloroplast and the cyanobacteria genus Leptolyngbya. 16S rRNA gene-based DGGE analysis of DNA extracted directly from both layers indicated that although both layers harboured phylotypes most similar to the Cyanobacterial genera Nostoc, Chroococcidiopsis, and Microcoleus, and the Chlorophyte Stichococcus bacillaris, the two layers also harboured unique genera such as Scytonema, and Symploca (red, external layer of dolomite) and Chlorella (green, internal layer of dolomite). The unique community structure of each layer suggests a selection process directed by the pressures of the endolithic environment. We conclude that the overall composition of the phototrophic community closely resembles that of endolithic communities located in extreme habitats, suggesting that a cosmopolitan community inhabits this defined niche.

  5. Adsorption of Cu2+ and Pb2+ ion on dolomite powder.

    Science.gov (United States)

    Pehlivan, Erol; Ozkan, Ali Müjdat; Dinç, Salih; Parlayici, Serife

    2009-08-15

    Natural Turkish dolomite was shown to be effective for removing Cu(2+) and Pb(2+) from aqueous solution. Selected information on pH, dose required, initial metal concentration, adsorption capacity of the raw dolomite powder was evaluated for its efficiency in adsorbing metal ions. Dolomite exhibited good Cu(2+) and Pb(2+) removal levels at all initial metal amount tested (0.04-0.32 mmol, 20 mL). It is important to note that the adsorption capacities of the materials in equilibrium vary, depending on the characteristics of the individual adsorbent, the initial concentration of the adsorbate and pH of the solution. One hour was enough for the removal of metal ions from (0.2 mmol in 20 mL) aqueous solution. Effective removal of metal ions was demonstrated at pH values of 5.0. The adsorptive behavior of dolomite was described by fitting data generated from the study of the Langmuir and Freundlich isotherm models. The adsorption capacity of dolomite was found as 8.26 mg for Cu(2+) and 21.74 mg for Pb(2+), respectively, from the calculation of adsorption isotherm equation. More than 85% of studied cations were removed by dolomite from aqueous solution in single step. The mechanism for cations removal by dolomite includes surface complexation and ion exchange.

  6. Dolomite-magnesian calcite relations at elevated temperatures and CO2 pressures

    Science.gov (United States)

    Graf, D.L.; Goldsmith, J.R.

    1955-01-01

    The equilibrium thermal decomposition curve of dolomite has been determined up to a CO2 pressure of 20,000 lb/in.2, at which pressure dolomite decomposes at 857??C. Equilibrium was approached from both directions, by the breakdown and by the solid-state synthesis of dolomite. At elevated temperatures and pressures, calcites in equilibrium with periclase as well as those in equilibrium with dolomite contain Mg in solid solution. In the former, the Mg content increases with increasing CO2 pressure, and decreases with increasing temperature. In the latter, it is a function of temperature only. The exsolution curve of dolomite and magnesian calcite has been determined between 500?? and 800??C; at 500?? dolomite is in equilibrium with a magnesian calcite containing ~6 mol per cent MgCO2; at 800??, ~22 mol per cent. There appears to be a small but real deviation from the ideal 1 : 1 Ca : Mg ratio of dolomite, in the direction of excess Ca, for material in equilibrium with magnesian calcite at high temperature. The experimental findings indicate that very little Mg is stable in the calcites of sedimentary environments, but that an appreciable amount is stable under higher-temperature metamorphic conditions, if sufficient CO2 pressure is maintained. ?? 1955.

  7. Optimasi Dosis Pupuk Dolomit pada Tanaman Kelapa Sawit (Elaeis Guineensis Jacq. Belum Menghasilkan Umur Satu Tahun

    Directory of Open Access Journals (Sweden)

    - Sudradjat

    2015-09-01

    Full Text Available Kelapa sawit merupakan komoditi perkebunan utama karena sebagai sumber devisa negara dan menyediakan lapangan kerja. Indonesia adalah negara produsen terbesar kelapa sawit di dunia dengan luas areal mencapai 10.1 juta hektar. Peningkatan produktivitas dicapai dengan intensifikasi antara lain dengan melakukan rasionalisasi pemupkan. Penelitian ini bertujuan untuk menentukan dosis optimum pupuk dolomit pada tanaman kelapa sawit belum menghasilkan umur satu tahun. Penelitian ini dilaksanakan di Kebun Pendidikan dan Penelitian Kelapa Sawit IPB-Cargill, Jonggol, Bogor dari bulan Maret 2013 sampai Maret 2014. Rancangan yang digunakan adalah Faktorial Tunggal,  dosis pupuk dolomit,  yang disusun dalam lingkungan Acak Kelompok dengan tiga ulangan. Dosis pupuk dolomit yang diuji  terdiri atas 0, 200, 400, dan 600 g tanaman-1 tahun-1. Hasil penelitian menunjukkan bahwa pupuk dolomit meningkatkan secara nyata terhadap peubah tinggi tanaman, diameter batang, jumlah daun, dan kandungan khlorofil daun, namun tidak berpengaruh terhadap kandungan Mg dalam jaringan daun. Berdasarkan tanggap peubah tinggi tanaman, dosis optimum pupuk dolomit untuk tanaman kelapa sawit pada umur satu tahun adalah 306.4 g dolomit tanaman-1tahun -1. Kata kunci: dolomit, dosis optimum, kelapa sawit, respons fisiologi, respons morfologi.

  8. Hydrothermal dolomitization of basinal deposits controlled by a synsedimentary fault system in Triassic extensional setting, Hungary

    Science.gov (United States)

    Hips, Kinga; Haas, János; Győri, Orsolya

    2016-06-01

    Dolomitization of relatively thick carbonate successions occurs via an effective fluid circulation mechanism, since the replacement process requires a large amount of Mg-rich fluid interacting with the CaCO3 precursor. In the western end of the Neotethys, fault-controlled extensional basins developed during the Late Triassic spreading stage. In the Buda Hills and Danube-East blocks, distinct parts of silica and organic matter-rich slope and basinal deposits are dolomitized. Petrographic, geochemical, and fluid inclusion data distinguished two dolomite types: (1) finely to medium crystalline and (2) medium to coarsely crystalline. They commonly co-occur and show a gradual transition. Both exhibit breccia fabric under microscope. Dolomite texture reveals that the breccia fabric is not inherited from the precursor carbonates but was formed during the dolomitization process and under the influence of repeated seismic shocks. Dolomitization within the slope and basinal succession as well as within the breccia zones of the underlying basement block is interpreted as being related to fluid originated from the detachment zone and channelled along synsedimentary normal faults. The proposed conceptual model of dolomitization suggests that pervasive dolomitization occurred not only within and near the fault zones. Permeable beds have channelled the fluid towards the basin centre where the fluid was capable of partial dolomitization. The fluid inclusion data, compared with vitrinite reflectance and maturation data of organic matter, suggest that the ascending fluid was likely hydrothermal which cooled down via mixing with marine-derived pore fluid. Thermal gradient is considered as a potential driving force for fluid flow.

  9. New insights to the formation of modern dolomite in a terrestrial low-temperature environment

    Science.gov (United States)

    Zünterl, Andrea; Baldermann, Andre; Boch, Ronny; Dietzel, Martin

    2017-04-01

    Although dolomite [CaMg(CO3)2] is a rock-forming mineral in ancient carbonate platforms, its occurrence in modern-marine carbonate-depositing settings and in particular in terrestrial, low-temperature environments is scarce - an enigma that is referred to as the "dolomite problem". At present, it is generally accepted that microbial activity, bacterially-mediated sulfate reduction, high aqueous Mg/Ca ratios and anoxic conditions favour the nucleation and crystal growth of dolomite; albeit the precise reaction paths causing the formation of dolomite at low temperatures remain questionable. Here, we present a novel study about the environmental controls and reaction mechanisms leading to the formation of authigenic Mg-Ca carbonates in (active) fault zones of the Erzberg (Styria, Austria) - Europe's largest iron ore opencast mine. Our petrographic and mineralogical results revealed the presence of ˜2-20 cm thick laminated successions of embedded needle-shaped, radiating aragonite and blocky low-Mg calcite (a repetitive sequence also-called "erzbergite") and subsequently deposited (Ca-rich) non-stoichiometric dolomite, which is clogging former voids and unconsolidated sediment in the heavily deteriorated fault zone. First U-Th age determinations of the respective aragonite layers indicate its formation at ˜19,000-13,000 years BP, also suggesting a "young" age of the sedimentary dolomite. Based on the combination of X-ray diffraction and electron microprobe analyses we identified two types of matrix-replacing dolomite: type 1 dolomite is nearly stoichiometric (˜51 mol% CaCO3) and shows a high degree of cation ordering (0.4-0.6), whereas type 2 dolomite is characterized by Ca-excess (˜55 mol% CaCO3) and a low degree of ordering (<0.3). Both types of dolomite grow on the extent of matrix minerals, such as detrital low-Mg calcite, ankerite, siderite, quartz, goethite, chlorite and illitic clay minerals, implying a low-temperature origin of the Ca-excess dolomite and

  10. Effect of CeO2 on Sintering and Hydration Resistance of Natural Dolomite

    Institute of Scientific and Technical Information of China (English)

    XUYan-qing; CHENZhao-you

    1996-01-01

    The sinteribility and hydration resistance of high pure natural dolomite doped with CeO2 addition were studied.It is found that the addition of CeO2 to dolomite can significantly improve the sintering and the resistane to hydration of dolomite.Doping 0.25% CeO2,followed by firing at 1600℃ for 4 hours,a dense doloma clinker with bulk density>3.25 g/cm3, apparent porosity<1.0% and excellent hydration resistance has been obtained.

  11. Kinetic and Thermodynamic Studies on the Phosphate Adsorption Removal by Dolomite Mineral

    OpenAIRE

    Xiaoli Yuan; Wentang Xia; Juan An; Jianguo Yin; Xuejiao Zhou; Wenqiang Yang

    2015-01-01

    The efficiency of dolomite to remove phosphate from aqueous solutions was investigated. The experimental results showed that the removal of phosphate by dolomite was rapid (the removal rate over 95% in 60 min) when the initial phosphate concentration is at the range of 10–50 mg/L. Several kinetic models including intraparticle diffusion model, pseudo-first-order model, Elovich model, and pseudo-second-order model were employed to evaluate the kinetics data of phosphate adsorption onto dolomit...

  12. Bacterially Induced Dolomite Formation in the Presence of Sulfate Ions under Aerobic Conditions

    Science.gov (United States)

    Sanchez-Roman, M.; McKenzie, J. A.; Vasconcelos, C.; Rivadeneyra, M.

    2005-12-01

    The origin of dolomite remains a long-standing enigma in sedimentary geology because, although thermodynamically favorable, precipitation of dolomite from modern seawater does not occur. Experiments conducted at elevated temperatures (200 oC) indicated that the presence of small concentrations of sulfate ions inhibits the transformation of calcite to dolomite [1]. Indeed, sulfate ions appeared to inhibit dolomite formation above 2 mM concentration (versus 28 mM in modern seawater). Recently, culture experiments have demonstrated that sulfate-reducing bacteria mediate the precipitation of dolomite at Earth surface conditions in the presence of sustained sulfate ion concentrations [2,3]. Additionally, in a number of modern hypersaline environments, dolomite forms from solutions with high sulfate ion concentrations (2 to 70 times seawater). These observations suggest that the experimentally observed sulfate-ion inhibition [1] may not apply to all ancient dolomite formation. Here, we report aerobic culture experiments conducted at low temperatures (25 and 35 oC) and variable sulfate ion concentrations (0, 0.5, 1 and 2 x seawater values) using moderately halophilic bacteria, Halomonas meridiana. After an incubation period of 15 days, experiments at 35 oC with variable sulfate ion concentrations (0, 0.5 x and seawater values) contained crystals of Ca-dolomite and stochiometric dolomite. The experiment at 35 oC with 2 x seawater sulfate ion concentration produced dolomite crystals after 20 days of incubation. In a parallel set of experiments at 25 oC, precipitation of dolomite was observed after 25 days of incubation in cultures with variable sulfate ion concentrations (0, 0.5 x and seawater values). In the culture with 2 x seawater sulfate ion concentration, dolomite crystals were observed after 30 days. Our study demonstrates that halophilic bacteria (or heterotrophic microorganisms), which do not require sulfate ions for metabolism, can mediate dolomite precipitation

  13. Reaction Sintering of Mexican Dolomite – Zircon Mixtures

    Directory of Open Access Journals (Sweden)

    Rodríguez-Galicia, J. L.

    2005-08-01

    Full Text Available The present work has been conducted aiming to develop additional phase [Ca3SiO5, Ca2SiO4 and/or Ca3Mg(SiO42]-bonded magnesia refractory materials via reaction sintering of dolomite-zircon mixtures, employing a Mexican dolomite containing an excess of 3 wt% of CaCO3. The study was based on phase equilibrium data extracted from the quaternary system CaO – MgO – SiO2 – ZrO2, to put it more precisely, base on the projection from the MgO-apex of the liquidus surface of the primary crystallization volume of MgO onto the opposite face of the above mentioned quaternary system. The refractory materials designed within this system were obtained by attrition milling, followed by cold isostatic pressing and high temperature reaction sintering. All initial and produced materials were characterized by ICP-AES, XRF, XRD, SEM-EDX, DTA and TG analyses. The results obtained indicated that reaction sintering of dolomite-zircon mixtures is an interesting route to produce MgO-CaZrO3-additional phase refractory materials.

    El propósito de este trabajo ha sido obtener materiales refractarios de magnesia, aglomerados con una fase adicional [Ca3SiO5, Ca2SiO4 y/o Ca3Mg(SiO42], mediante la sinterización reactiva de mezclas de dolomita-circón, empleando para ello una dolomita mexicana que contiene un exceso de 3% en peso de CaCO3. El estudio se basa en la información relativa al equilibrio de fases del sistema CaO – MgO – SiO2 – ZrO2. En concreto se usa la proyección, desde el vértice del MgO, de la superficie de liquidus del volumen de cristalización primaria de este, hacia la cara opuesta de sistema cuaternario. Los materiales refractarios diseñados se han obtenido por molienda de atrición, seguida de un prensado isostático en frío y sinterización reactiva a alta temperatura. Todos los materiales, iniciales y finales, han sido caracterizados mediante ICPAES, FRX, DRX, MEB-EDX, ATD y TG. Los resultados obtenidos indican que la sinterizaci

  14. Characterization of adsorption of aqueous arsenite and arsenate onto charred dolomite in microcolumn systems.

    Science.gov (United States)

    Salameh, Yousef; Al-Muhtaseb, Ala'a H; Mousa, Hasan; Walker, Gavin M; Ahmad, Mohammad N M

    2014-01-01

    In this work, the removal of arsenite, As(III), and arsenate, As(V), from aqueous solutions onto thermally processed dolomite (charred dolomite) via microcolumn was evaluated. The effects of mass of adsorbent (0.5-2 g), initial arsenic concentration (50-2000 ppb) and particle size (dolomite in a microcolumn were investigated. It was found that the adsorption of As(V) and As(III) onto charred dolomite exhibited a characteristic 'S' shape. The adsorption capacity increased as the initial arsenic concentration increased. A slow decrease in the column adsorption capacity was noted as the particle size increased from>0.335 to 0.710-2.00 mm. For the binary system, the experimental data show that the adsorption of As(V) and As(III) was independent of both ions in solution. The experimental data obtained from the adsorption process were successfully correlated with the Thomas Model and Bed Depth Service Time Model.

  15. An investigation on the catalytic capacity of dolomite in transesterification and the calculation of kinetic parameters.

    Science.gov (United States)

    Niu, Sheng-Li; Huo, Meng-Jia; Lu, Chun-Mei; Liu, Meng-Qi; Li, Hui

    2014-04-01

    The catalytic capacity of dolomite in transesterification was investigated and the kinetic parameters were calculated. The activated dolomites as transesterification catalyst were characterized by X-ray diffraction, nitrogen adsorption and desorption and Hammett indicator method, where the original dolomite was analyzed by thermogravimetric and X-ray fluorescence in advance. Its potential catalytic capacity was validated from aspects of the activated temperature and the reused property, where the reliability of the experimental system was also examined. Then, influences of the catalyst added amount, the mole ratio of methanol to oil, the transesterification temperature and the transesterification time on the catalytic capacity were investigated. Finally, kinetic parameters of the transesterification catalyzed by the activated dolomite were calculated.

  16. Secondary ferroan dolomite rhombs in oil reservoirs, Chadra Sands, Gialo field, Libya

    Energy Technology Data Exchange (ETDEWEB)

    Al-Shaieb, Z.; Shelton, J.W.

    1978-03-01

    Oil-productive, Oligocene Chadra sands in Gialo field, Libya, at depths of 600 to 750 m contain small dolomite rhombs. The rhombs are present as single crystals on detrital grains and as nonmosaic aggregates in pore space. The dolomite is calcium-rich and contains up to 10% iron but not measurable sodium or strontium. Total dissolved solids of produced interstitial water from the Chadra sand range from about 4,500 to 10,000 ppM. Introduction of fresh (meteoric) water into the Chadra sands, which were deposited in shallow-marine (shelf) environment, was responsible for formation of the dolomite rhombs. Iron in the dolomite rhombs was derived from alteration of galuconite.

  17. Dolomitization in a mixing zone of near-seawater composition, Late Pleistocene, northeastern Yucatan Peninsula

    Science.gov (United States)

    Ward, W. C.; Halley, Robert B.

    1985-01-01

    Patches of dolomite occur in cores of reefal limestone from the shallow subsurface on the northeastern coast of the Yucatan Peninsula. This limestone accumulated during an interglacial high stand of sea level about 200,000 years ago. Dolomitization was preceded by freshwater diagenesis, including precipitation of sparry calcite cement, stabilization of Mg-calcitic skeletal fragments, and partial dissolution of aragonitic components. This suggests a predolomitization lowering of sea level with the consequent freshening of pore water. The subsequent precipitation of dolomite indicates a return to high sea level with the consequent increase in Mg/Ca ratio of pore water. Dolomitization took place during a brief high stand of sea level, either shortly after deposition about 200,000 yr BP, r, more likely, about 125,000 yr BP.

  18. Thermal decomposition of dolomite under CO2: insights from TGA and in situ XRD analysis.

    Science.gov (United States)

    Valverde, Jose Manuel; Perejon, Antonio; Medina, Santiago; Perez-Maqueda, Luis A

    2015-11-28

    Thermal decomposition of dolomite in the presence of CO2 in a calcination environment is investigated by means of in situ X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The in situ XRD results suggest that dolomite decomposes directly at a temperature around 700 °C into MgO and CaO. Immediate carbonation of nascent CaO crystals leads to the formation of calcite as an intermediate product of decomposition. Subsequently, decarbonation of this poorly crystalline calcite occurs when the reaction is thermodynamically favorable and sufficiently fast at a temperature depending on the CO2 partial pressure in the calcination atmosphere. Decarbonation of this dolomitic calcite occurs at a lower temperature than limestone decarbonation due to the relatively low crystallinity of the former. Full decomposition of dolomite leads also to a relatively low crystalline CaO, which exhibits a high reactivity as compared to limestone derived CaO. Under CO2 capture conditions in the Calcium-Looping (CaL) process, MgO grains remain inert yet favor the carbonation reactivity of dolomitic CaO especially in the solid-state diffusion controlled phase. The fundamental mechanism that drives the crystallographic transformation of dolomite in the presence of CO2 is thus responsible for its fast calcination kinetics and the high carbonation reactivity of dolomitic CaO, which makes natural dolomite a potentially advantageous alternative to limestone for CO2 capture in the CaL technology as well as SO2in situ removal in oxy-combustion fluidized bed reactors.

  19. Can Mn–S redox cycling drive sedimentary dolomite formation? A hypothesis

    Energy Technology Data Exchange (ETDEWEB)

    Petrash, Daniel A.; Lalonde, Stefan V.; González-Arismendi, Gabriela; Gordon, Robert A.; Méndez, José A.; Gingras, Murray K.; Konhauser, Kurt O. (CLS); (UCV-Venezuela); (CNRS-UMR); (Alberta)

    2016-06-10

    The formation of dolomite in modern peritidal environments is linked to the degradation of buried microbial mats, with complexation of Ca and Mg by extracellular polymeric substances (EPSs) and alkalinity generation through organic carbon respiration facilitating the nucleation of dolomite precursors. In the past two decades, microbial sulfate reduction, methanogenesis, and methanotrophy have all been considered as potential drivers of the nucleation process, but it remains unclear why dolomite formation could not also occur in suboxic sediments where abundant alkalinity is produced by processes linked to Mn(IV) and/or Fe(III) reduction coupled with the diffusion and reoxidation of reduced sulfur species. Here we report the interstitial occurrence of spheroidal aggregates of nanometer-scale Ca-rich dolomite rhombohedra within suboxic sediments associated with remnant microbial mats that developed in the peritidal zone of the Archipelago Los Roques, Venezuela. Multiple analytical tools, including EPMA, ICP-MS, synchrotron-based XRF and XRD, and spatially resolved XANES microanalyses, show that the dolomite-cemented interval exhibits depleted bulk iron concentrations, but is interstitially enriched in Mn and elemental sulfur (S⁰). Manganese occurs in several oxidation states, indicating that the dolomite-cemented interval was the locus of complex biological redox transformations characterized by coupled Mn and S cycling. The tight correspondence between sedimentary Mn and MgCO₃ concentrations further hints at a direct role for Mn during dolomitization. While additional studies are required to confirm its relevance in natural settings, we propose a model by which coupled Mn–S redox cycling may promote alkalinity generation and thus dolomite formation in manner similar to, or even more efficiently, than bacterial sulfate reduction alone.

  20. Evaluating formation fluid models and calibrations using clumped isotope paleothermometry on Bahamian dolomites

    Science.gov (United States)

    Murray, Sean T.; Swart, Peter K.

    2017-06-01

    The use of stable oxygen isotopes to understand the mechanisms of dolomite formation has been hampered by the inability to precipitate well-ordered dolomite under normal Earth surface conditions. Several studies have attempted to address this problem, either by precipitating high-temperature ordered dolomites and extrapolating the data to low temperatures or by using more disordered very-high Mg-calcites as a proxy for low temperature dolomites. The result is eight equations that disagree significantly from each other (by as much as ∼3.6‰ in the δ18O value of the precipitating fluid at 25 °C), and produce differences which can greatly affect the interpretation of the formation mechanisms for low temperature dolomites. However, by combining the recently developed clumped-isotope paleothermometer, an independent isotopic measurement (∆47) that directly relates to the temperature of formation, to Late Miocene to Pleistocene aged dolomites from the Bahamas with a well-constrained thermal and fluid history, we have attempted to narrow down the viable equations used to interpret the δ18O values of dolomites. The clumped-isotope temperatures measured on the Bahamian dolomites (16-37 °C) agrees with the range of temperatures expected in the Bahamas. Pairing these temperatures with geological and mineralogical arguments, we favor the equation suggested by Matthews and Katz (1977), as it is the only one that produces realistic δ18O fluid values across the range of clumped-isotope temperatures. Both the clumped-isotope temperatures and δ18O values of the precipitating fluid show a strong positive covariance that we have interpreted as reflecting the mixing of surface brines that have undergone varying amounts of evaporation and normal seawater. The different mechanisms driving these fluids included formation by normal marine seawater driven by the compensatory flow of the mixing zone, bank wide Kohout convection, and evaporative brine reflux.

  1. Numerical modelling of geothermal and reflux circulation in Enewetak Atoll: Implications for dolomitization

    Science.gov (United States)

    Jones, G.; Whitaker, F.; Smart, P.; Sanford, W.

    2000-01-01

    Two types of regional-scale seawater circulation have been proposed to explain the formation of Enewetak Atoll dolomites: geothermal and reflux circulation. We have used a finite element groundwater flow model to examine the pattern, magnitude and dynamic interaction of these two different circulation mechanisms in Enewetak Atoll. Geothermal circulation is concentrated around the atoll-margin whereas refluxing mesosaline brines flow from the atoll interior towards the margin to restrict and eventually shut off geothermal circulation. Refluxing brines of 36-80??? can account for the salinity signature recorded in dolomite fluid inclusions. Distributions of fluid flux and Mg mass-balance calculations suggest that both geothermal and reflux circulation mechanisms could account for the observed distribution of dolomite in Enewetak Atoll. Furthermore, the atoll interior may be extensively dolomitized as observed in other atolls. (C) 2000 Elsevier Science B.V. All rights reserved.Two types of regional-scale seawater circulation have been proposed to explain the formation of Enewetak Atoll dolomites: geothermal and reflux circulation. We have used a finite element groundwater flow model to examine the pattern, magnitude and dynamic interaction of these two different circulation mechanisms in Enewetak Atoll. Geothermal circulation is concentrated around the atoll-margin whereas refluxing mesosaline brines flow from the atoll interior towards the margin to restrict and eventually shut off geothermal circulation. Refluxing brines of 36-80 per mil can account for the salinity signature recorded in dolomite fluid inclusions. Distributions of fluid flux and Mg mass-balance calculations suggest that both geothermal and reflux circulation mechanisms could account for the observed distribution of dolomite in Enewetak Atoll. Furthermore, the atoll interior may be extensively dolomitized as observed in other atolls.

  2. The relationship between dolomitization and organic matter occurrence in Lower Paleozoic carbonate in the Ordos Basin

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Based on observations on the core and surface sections of Lower Paleozoic carbonate in the Ordos Basin, petrography research and measurements of TOC, TOS , Ro, XRD, and comparative study with dolomite in modern Coorong Lake, it has been revealed that: (i)dolomitization may occur in micrite limestone, gypsum-halite and argillaceous sandstone, and it can be divided into three types: sedimentary penecontemporaneous-early diagenesis, late diagenesis of deep burial and catagenesis of uplift period. However, the crystal cell of the second type less than 35 μ m in size is most closely associated with gas pool; (ii) the highest content of organic matter (OM) is produced in samples from the argillic dolomite which may be formed by argillaceous fluid through gypsum-halite; (iii) in the evolution process from penecontemporaneous dolomite into stoichiometric dolomite, the crystal order of dolomite and the porosity of its host rock tend to increase, which is favorable to the formation of an available migration network. When the power of the fluid is high enough, the network is mainly favorable to the migration and transport of heat, but when the power of the fluid goes down, the network system is favorable, due to its large space, to OM deposition in it.

  3. Quantitative lateral force microscopy study of the dolomite (104)-water interface.

    Science.gov (United States)

    Higgins, Steven R; Hu, Xiaoming; Fenter, Paul

    2007-08-14

    The friction and lateral stiffness of the contact between an atomic force microscopy (AFM) probe tip and an atomically flat dolomite (104) surface were investigated in contact with two aqueous solutions that were in equilibrium and supersaturated with respect to dolomite, respectively. The two aqueous solutions yielded negligible differences in friction at the native dolomite-water interface. However, the growth of a Ca-rich film from the supersaturated solution, revealed by X-ray reflectivity measurements, altered the probe-dolomite contact region sufficiently to observe distinct friction forces on the native dolomite and the film-covered surface regions. Quantitative friction-load relationships demonstrated three physically distinct load regimes for applied loads up to 200 nN. Similar friction forces were observed on both surfaces below 50 nN load and above 100 nN load. The friction forces on the two surfaces diverged at intermediate loads. Quantitative measurements of dynamic friction forces at low load were consistent with the estimated energy necessary to dehydrate the surface ions, whereas differences in mechanical properties of the Ca-rich film and dolomite surfaces were evidently important above 50 nN load. Attempts to fit the quantitative stiffness-load data using a Hertzian contact mechanical model based on bulk material properties yielded physically unrealistic fitting coefficients, suggesting that the interfacial contact region must be explicitly considered in describing the static and dynamic contact mechanics of this and similar systems.

  4. Performance of thermally activated dolomite for the treatment of Ni and Zn in contaminated neutral drainage.

    Science.gov (United States)

    Calugaru, Iuliana Laura; Neculita, Carmen Mihaela; Genty, Thomas; Bussière, Bruno; Potvin, Robin

    2016-06-05

    Intensive research is ongoing for developing low-cost and highly efficient materials in metal removal from contaminated effluents. The present study evaluated dolomite [CaMg(CO3)2], both raw and modified by thermal activation (charring), for Ni and Zn treatment in contaminated neutral drainage (CND). Batch adsorption testing (equilibrium and kinetics) were conducted at pH 6, to evaluate the performance of initial vs. modified dolomite, and to assess potential mechanisms of metal removal. Charring of dolomite led to a rigid and porous material, mainly consisting of CaCO3 and MgO, which showed a sorption capacity increased sevenfold for Zn and doubled for Ni, relative to the raw material. In addition, Freundlich model best described the sorption of the both metals by dolomite, whereas the Langmuir model best described their sorption on charred dolomite. Plausible mechanisms of metal removal include cation exchange, surface precipitation and sorption processes, with carbonate ions and magnesium oxides acting as active centers. Based on these results, charred dolomite seems a promising option for the efficient treatment of Ni and Zn in CND.

  5. Adsorptive removal of phosphate from aqueous solutions using raw and calcinated dolomite.

    Science.gov (United States)

    Karaca, S; Gürses, A; Ejder, M; Açikyildiz, M

    2006-02-06

    This study explored the feasibility of utilizing raw and calcinated dolomite under CO2 atmosphere for phosphate removal in laboratory experiments. The experimental work emphasized the evaluation of phosphate adsorption characteristics of this adsorbent material. Studies were conducted to delineate the effect of contact time, initial phosphate concentration, temperature, pH, stirring speed, adsorbent dose and calcination temperature. Phosphate removal decreased with increasing temperature and slightly increased with increasing of pH. The observed decrease in the adsorption capacity with increase of the temperature from 20 to 40 and to 60 degrees C indicates that the low temperatures favor the phosphate removal by adsorption onto dolomite. Phosphate removal was seen to decrease with increasing calcination temperature due to the structural changes occurring in the structure and pore size distribution of dolomite samples during calcination. The experimental data obtained were applied to the Freundlich, Langmuir, BET, Halsey, Harkins-Jura, Smith and Henderson isotherm equations to test the fit of these equations to raw and calcinated dolomite samples. By considering the experimental results and adsorption models applied in this study, it can be concluded that adsorption of phosphate occurs predominantly through physical interactions, and the dolomite sample has a heteroporous structure. The large values of the constants for Henderson equation and the high value of y(m) obtained from BET equation indicate the microporous structure is more stable in raw and calcinated dolomite samples.

  6. PHOSPHORUS REMOVAL IN A VERTICAL FLOW CONSTRUCTED WETLAND USING DOLOMITE POWDER AND CHIPPINGS AS FILTER MEDIA

    Directory of Open Access Journals (Sweden)

    Gražina Žibienė

    2015-12-01

    Full Text Available Different kinds of natural and artificial filter media are able to retain phosphorus in the constructed wetlands. Due to the fact that the constructed wetland needs huge amounts of the filter media, it is very important to find locally available material which distinguishes itself by its ability to retain phosphorus. The materials found in Lithuania were considered and dolomite was chosen. Two dolomite fractions, dolomite powder (1–2 mm and dolomite chippings (2–5 mm, and sand media were used in the laboratory- scale installed for the comparative experiments. The laboratory-scale with dolomite as the filter media was on average by 21% more efficient in total phosphorus removal in comparison with the sand media. Based on the laboratory research pilot–scale vertical flow constructed wetland of 160 m2 was installed and planted with reed Phragmites australis. The dolomite chippings as filter media were chosen in order to avoid the danger of the clogging of constructed wetland. Efficiency of total phosphorus removal in the pilot-scale vertical flow constructed wetland was on average 95.7%, phosphates removal – 94.8% within one year.

  7. DOLOMITE THERMAL-DECOMPOSITION MACROKINETIC MODELS FOR EVALUATION OF THE GASGENERATORS SORBENT SYSTEMS

    Directory of Open Access Journals (Sweden)

    K. V. Dobrego

    2015-01-01

    Full Text Available Employing dolomite in the capacity of a sorbent for generator gas purification is of considerable interest nowadays, as it is the impurity of generator gas that causes the major problem for creating cheep and effective co-generator plants. Designing gas purification systems employs simple but physically adequate macrokinetic models of dolomite thermal decomposition.  The  paper  analyzes  peculiarities  of  several  contemporaneous  models  of  dolomite and calcite thermal decomposition and infers on reasonable practicality for creating compact engineering dolomite-decomposition macrokinetic models and universal techniques of these models parameter reconstruction for specific dolomite samples. Such technics can be founded on thermogravimetric data and standard approximation error minimizing algorithms.The author assumes that CO2  evacuation from the reaction zone within the particle may proceed by diffusion mechanism and/or by the Darcy filtration and indicates that functional dependence of the thermal-decomposition rate from the particle sizes and the temperature differs for the specified mechanisms. The paper formulates four macrokinetic models whose correspondence verification is grounded on the experimental data. The author concludes that further work in this direction should proceed with the dolomite samples investigation and selecting the best approximation model describing experimental data in wide range of temperatures, warming up rates and the particle sizes.

  8. Influence Parameters on Properties of Dolomite Bricks Containing Different Bonding Systems

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Pitch and tar bonded dolomite bricks are extensively used in ladles and converters for long time because of their superior properties such as: steel melt refining, easy production as well as low production cost. Recently,resin bonded dolomite bricks are presented for using in steel plants. Generally, quality and final cost of steels are affected by properties of refractories especially dolomite bricks. Therefore, recognition of influence parameters on dolomite refractory properties is very important.In this study, the effects of tar and resin as bonding systems, and addition of graphite ( 2wt% ) on the properties of dolomite refractory bricks have been investigated.Properties such as: density and porosity, cold crushing strength, hydration time and depth of slag penetration have been studied. Results show that the bonding systems and graphite have a great effect on the mentioned properties especially cold crushing strength and hydration time. In addition to their low rate of pollution, resin bonded dolomite bricks show higher performance with proper technical specifications.

  9. The influence of solution composition and grain boundaries on the replacement of calcite by dolomite

    Science.gov (United States)

    Moraila Martinez, Teresita de Jesus; Putnis, Christine V.; Putnis, Andrew

    2016-04-01

    Dolomite formation is a mineral replacement reaction that affects extensive rock volumes and comprises a large fraction of oil and gas reservoirs [1,2]. The most accepted hypothesis is the 'dolomitization' of limestone by Mg-rich fluids [3]. The objective of this research is to study the replacement mechanism of calcite by dolomite, the role of grain boundaries, highlighted by Etschmann et al. (2014), and the possible influence of solutions in dolomite formation under the presence of ions that are normally in crustal aqueous fluids. To accomplish this purpose, we performed hydrothermal experiments using Carrara marble cubes of ~1.5 mm size and 7-9 mg weight as starting material, reacted with 1M (Mg,Ca)Cl2 aqueous solutions, with Mg/Ca ratios of 3 and 5 at 200°C, for different reaction times. Additional experiments were performed adding 1mM of Na2SO4, NaCl or NaF to the previous solutions. After the reaction, the product phases were identified using Raman spectroscopy, X-Ray powder diffraction (XRD), electron microprobe analysis (EMPA), and the textural evolution was studied by scanning electron microscopy (SEM). Samples reacted with aqueous solutions resulted in the replacements of the calcite rock into magnesite and dolomite. The amount and type of reaction strongly depends on the Mg/Ca ratio. Samples reacted with a Mg/Ca ratio of 5 resulted in an almost complete replacement reaction and more favorable for magnesite formation than for dolomite. When the Mg/Ca ratio was 3 dolomite formed but the replacement was located in the core of the sample. We show that grain boundaries are very important for the infiltration of solution and the progress of a replacement reaction, acting as fluid pathways. Solution composition controls the nature of the replacement product. Acknowledgment: This work is funded within a Marie Curie EU Initial Training Network- CO2-React. 1. Etschmann B., Brugger J., Pearce M.A., Ta C., Brautigan D., Jung M., Pring A. (2014). Grain boundaries as

  10. Dolomite application to acidic soils: a promising option for mitigating N2O emissions.

    Science.gov (United States)

    Shaaban, Muhammad; Peng, Qi-An; Hu, Ronggui; Wu, Yupeng; Lin, Shan; Zhao, Jinsong

    2015-12-01

    Soil acidification is one of the main problems to crop productivity as well as a potent source of atmospheric nitrous oxide (N2O). Liming practice is usually performed for the amelioration of acidic soils, but the effects of dolomite application on N2O emissions from acidic soils are still not well understood. Therefore, a laboratory study was conducted to examine N2O emissions from an acidic soil following application of dolomite. Dolomite was applied to acidic soil in a factorial design under different levels of moisture and nitrogen (N) fertilizer. Treatments were as follows: dolomite was applied as 0, 1, and 2 g kg(-1) soil (named as CK, L, and H, respectively) under two levels of moisture [i.e., 55 and 90 % water-filled pore space (WFPS)]. All treatments of dolomite and moisture were further amended with 0 and 200 mg N kg(-1) soil as (NH4)2SO4. Soil properties such as soil pH, mineral N (NH4 (+)-N and NO3 (-)-N), microbial biomass carbon (MBC), dissolved organic carbon (DOC), and soil N2O emissions were analyzed throughout the study period. Application of N fertilizer rapidly increased soil N2O emissions and peaked at 0.59 μg N2O-N kg(-1) h(-1) under 90 % WFPS without dolomite application. The highest cumulative N2O flux was 246.32 μg N2O-N kg(-1) under 90 % WFPS without dolomite addition in fertilized soil. Addition of dolomite significantly (p ≤ 0.01) mitigated N2O emissions as soil pH increased, and H treatment was more effective for mitigating N2O emissions as compared to L treatment. The H treatment decreased the cumulative N2O emissions by up to 73 and 67 % under 55 and 90 % WFPS, respectively, in fertilized soil, and 60 and 68 % under 55 and 90 % WFPS, respectively, in unfertilized soil when compared to those without dolomite addition. Results demonstrated that application of dolomite to acidic soils is a promising option for mitigating N2O emissions.

  11. Basic Data Report for Drillhole SNL-9 (C-2950)

    Energy Technology Data Exchange (ETDEWEB)

    Dennis W. Powers; Washington Regulatory and Environmental Services

    2005-01-19

    SNL-9 (permitted by the State Engineer as C-2950) was drilled to provide geological data and hydrological testing of the Culebra Dolomite Member of the Permian Rustler Formation within a proposed re-entrant of the margin of halite dissolved from the upper part of the Salado near Livingston Ridge. SNL-9 is located in the southeast quarter of section 23, T22S, R30E, in eastern Eddy County, New Mexico. SNL-9 was drilled to a total depth of 845 ft below the ground surface. Below surface dune sand and the Berino soil, SNL-9 encountered, in order, the Mescalero caliche, Gatuna, Dewey Lake, Rustler, and uppermost Salado Formations. Two intervals were cored: 1) from the lower Forty-niner Member through the Magenta Dolomite and into the upper Tamarisk Member; and 2) from the lower Tamarisk Member through the Culebra Dolomite and Los Meda?os Members and into the uppermost Salado Formation. Geophysical logs were acquired from the open hole to total depth, and the drillhole was successfully completed with a screened interval open across the Culebra.

  12. Basic Data Report for Drillhole SNL-5 (C-3002)

    Energy Technology Data Exchange (ETDEWEB)

    Dennis W. Powers; Washington Regulatory and Environmental Services

    2005-01-18

    SNL-5 (permitted by the New Mexico State Engineer as C-3002) was drilled to provide geological data and hydrological testing of the Culebra Dolomite Member of the Permian Rustler Formation in an area north of the Waste Isolation Pilot Plant (WIPP) site where data are sparse and where a pumping or monitoring well for the northern pumping test is needed. SNL-5 is located in the southeast quarter of section 6, T22S, R31E, in eastern Eddy County, New Mexico. SNL-5 was drilled to a total depth of 687 ft below ground level (bgl), based on driller's measurements. Below the caliche pad, SNL-5 encountered the Mescalero caliche, Gatu?a, Dewey Lake, and Rustler Formations. Two intervals of the Rustler were cored: (1) from the lower Forty-niner Member through the Magenta Dolomite and into the upper Tamarisk Member; and (2) from the lower Tamarisk Member through the Culebra Dolomite and into the upper Los Meda?os Members. Geophysical logs were acquired from the open hole to a depth of ~672 ft. No water was observed to flow into the open drillhole until the Culebra was penetrated. includes horizontal beds and laminae near the base, and the uppermost part shows some inclined bedding. The mudstone unit shows mostly reddish brown claystone and siltstone with some gray mottling. Clasts or intraclasts are also included in the unit. The upper Tamarisk sulfate is somewhat brecciated near the base.

  13. Basic Data Report for Drillhole SNL-12 (C-2954)

    Energy Technology Data Exchange (ETDEWEB)

    Powers, Dennis W. [Washington Regulatory and Environmental Services (United States)

    2005-01-20

    SNL-12 (permitted by the New Mexico State Engineer as C-2954) was drilled to provide geological data and hydrological testing of the Culebra Dolomite Member of the Permian Rustler Formation near the margin of dissolution of halite in the upper part of the Salado south of the Waste Isolation Pilot Plant (WIPP). SNL-12 is located in the southeast quarter of section 20, T23S, R31E, in eastern Eddy County, New Mexico. SNL-12 was drilled to a total depth of 905 ft below the ground level. Below surface dune sand and the Berino soil, SNL-12 encountered, in order, the Mescalero caliche, Gatu?a, Dewey Lake, Rustler, and uppermost Salado Formations. Two intervals were cored: (1) from the lower Forty-niner Member through the Magenta Dolomite and into the upper Tamarisk Member; and (2) from the lower Tamarisk Member through the Culebra Dolomite and Los Meda?os Members and into the uppermost Salado Formation. Geophysical logs were acquired from the open hole to total depth, and the drillhole was successfully completed with a screened interval open across the Culebra. At SNL-12, the uppermost Salado cores display displacive halite crystals in clastic-rich units below an amalgamated sulfate at the top of the formation. There is no indication of thinning of the upper Salado due to postdepositional dissolution, and this is consistent with predrilling expectations.

  14. Hydrogeochemistry Of A Modern Dolomite-Forming Lagoon System, Cabo Frio-RJ, Brazil

    Science.gov (United States)

    Moreira, N. F.; Walter, L. M.

    2004-12-01

    Two hypersaline, dolomite-forming lagoons near Cabo Frio, Brazil, and associated ground- and surface waters were sampled in a comparative sediment and fluid geochemical (solutes, stable isotopes) investigation. Although microbial mediation via sulfate reducers has been invoked to explain dolomite formation in these lagoons, we showed that dolomites are associated with sulfide oxidation (Moreira et al., 2004). Sulfide oxidation is thought to promote dolomite formation by causing undersaturation for competing carbonate phases such as Mg-calcite. Herein, we consider the larger hydrogeologic and temporal setting to further elucidate hydrogeochemical and geochemical constraints on rates and mechanisms of dolomite formation in the two lagoons. The lagoons, Brejo do Espinho (BE) and Lagoa Vermelha (LV), are shallow marginal marine systems flanked by quartz sand dunes separating them from Atlantic open seawater to the south and from Araruama lagoon, a large, hypersaline water body, to the north. In both lagoons, about 1 m of high Mg-calcite and dolomite mud has accumulated over the last 5,000 years on an underlying aquifer composed of highly permeable, quartz-rich coquinas. BE has a proximal relation to recharge from Araruama lagoon, while LV is more closely associated with meteoric recharge from lacustrine and riverine systems. BE is shallower, at 0.5 m water depth, than LV (2 m), permitting BE waters to remain oxic. Oxygen isotope values and chloride mass balances of pore waters and of fluids sampled from shallow ground water wells identify the different water and solute sources the lagoons. BE overlying brines and pore waters appear to be produced by evapoconcentration of Araruama source brines and meteoric precipitation. In contrast, LV derives from evapoconcentrated seawater mixed with regional lake and ground water sources. We envision a scenario in which dense, Mg-SO4-rich brines from Araruama migrate along a permeable flowpath in limited contact with the atmosphere

  15. Effect of dolomite on the repair of bone defects in rats: histological study.

    Science.gov (United States)

    Moreschi, Eduardo; Hernandes, Luzmarina; Dantas, Jailson Araujo; da Silva, Maria Angélica Raffaini Covas Pereira; Casaroto, Ana Regina; Bersani-Amado, Ciomar Aparecida

    2010-12-01

    The aim of the present study was to evaluate histologically and radiographically the tissue response to dolomite [CaMg(CO3)2] and its osteogenic potential in the repair of bone cavities in the calvaria of rats. A bone defect 10 mm in diameter and 1 mm deep was made in the calvaria of male Wistar rats. The defects were filled with dolomite, inorganic bovine bone (positive control), or coagulum (negative control). The animals were euthanized 7, 15, 30, and 60 days after surgery, and specimens were collected for radiographic and microscopic analyses. The bone defects were processed for paraffin embedding and H&E staining. The histological study revealed that dolomite stimulated a moderate inflammatory response, with programmed cell death in the first 15 days, compared to bovine bone which showed a moderate to intense acute response. In the chronic phase, the inflammatory response was characterized by the occurrence of macrophages organized as epithelioid cells in the dolomite group, and giant cells in the bovine-bone group. Fibrosis developed in all three groups; however, encapsulation of the fragments, reabsorption, and osteoconductive activity occurred only in the defects filled with bovine bone. The radiographic analysis showed that the bovine bone was most efficient in the repair of the defects, followed by the dolomite and the coagulum. This study demonstrated that the dolomite stimulated a moderate acute inflammatory response with programmed cell death, and a chronic inflammatory response by means of the phagocytic mononuclear system. Although osteo-conductive activity was not shown, the dolomite favored the repair process, compared to the coagulum group.

  16. Effects of dicyandiamide and dolomite application on N2O emission from an acidic soil.

    Science.gov (United States)

    Shaaban, Muhammad; Wu, Yupeng; Peng, Qi-an; Lin, Shan; Mo, Yongliang; Wu, Lei; Hu, Ronggui; Zhou, Wei

    2016-04-01

    Soil acidification is a major problem for sustainable agriculture since it limits productivity of several crops. Liming is usually adopted to ameliorate soil acidity that can trigger soil processes such as nitrification, denitrification, and loss of nitrogen (N) as nitrous oxide (N2O) emissions. The loss of N following liming of acidic soils can be controlled by nitrification inhibitors (such as dicyandiamide). However, effects of nitrification inhibitors following liming of acidic soils are not well understood so far. Here, we conducted a laboratory study using an acidic soil to examine the effects of dolomite and dicyandiamide (DCD) application on N2O emissions. Three levels of DCD (0, 10, and 20 mg kg(-1); DCD0, DCD10, and DCD20, respectively) were applied to the acidic soil under two levels of dolomite (0 and 1 g kg(-1)) which were further treated with two levels of N fertilizer (0 and 200 mg N kg(-1)). Results showed that N2O emissions were highest at low soil pH levels in fertilizer-treated soil without application of DCD and dolomite. Application of DCD and dolomite significantly (P ≤ 0.001) reduced N2O emissions through decreasing rates of NH4 (+)-N oxidation and increasing soil pH, respectively. Total N2O emissions were reduced by 44 and 13% in DCD20 and dolomite alone treatments, respectively, while DCD20 + dolomite reduced N2O emissions by 54% when compared with DCD0 treatment. The present study suggests that application of DCD and dolomite to acidic soils can mitigate N2O emissions.

  17. Dolomite Problem”and Experimental Studies of Dolomite Formation%“白云石问题”及其实验研究

    Institute of Scientific and Technical Information of China (English)

    张亦凡; 马怡飞; 姚奇志; 钱飞进; 王雨晗; 李涵; 周根陶

    2015-01-01

    Dolomite problem is undoubtedly one of the most interesting and confusing problems in geology. As a common carbonate mineral, dolomite is abundant in geological history but rarely occurs in modern ocean sediments. It is nearly impossible to precipitate dolomite below 100℃. Dolomite, [CaMg(CO3)2], has a cation ordering structure and its space group is R-3. Additionally, it is thermodynamically stable under the condition of earth's surface. Although researchers tried to mimic physical and chemical conditions of natural environments which can form dolomite, these experiments still can not successfully precipitate ordered dolomite. Fully ordered dolomite can only form in hydrothermal experiments upper 200℃. It seems that the formation of dolomite is a dynamically controlling process. Recently, microbial dolomite model has been widely accepted. In this model, microbial activity is considered as the key of dolomite formation at low temperature. Many microbial mineralization experiments have confirmed that the existence of microorganisms can indeed promote the formation of high-magnesium calcite. Solving“dolomite problem”can not only help understanding the genesis of dolomite, but also promote the development of mineralogy theory. This review summarized current progresses of dolomite synthetic experiments, including experiments at high and low temperatures and microbially induced experiments. We also clarified the limitations of current understanding to“dolomite problem”. Future perspectives were proposed to better understand and finally solve dolomite problem.%“白云石问题”无疑是地质学上最有趣最长久的难题之一。作为一种常见的碳酸盐矿物,白云石在地质历史时期大量发育,却在现代海洋沉积环境中鲜少沉积,并且在实验室模拟海水条件下也几乎无法低温合成。白云石[CaMg(CO3)2]不同于Ca2+、Mg2+无序的高镁方解石,具有阳离子有序超结构,空间群为R-3,在地

  18. Comparative cytotoxicity of dolomite nanoparticles in human larynx HEp2 and liver HepG2 cells.

    Science.gov (United States)

    Ahamed, Maqusood; Alhadlaq, Hisham A; Ahmad, Javed; Siddiqui, Maqsood A; Khan, Shams T; Musarrat, Javed; Al-Khedhairy, Abdulaziz A

    2015-06-01

    Dolomite is a natural mineral of great industrial and commercial importance. With the advent of nanotechnology, natural minerals including dolomite in the form of nanoparticles (NPs) are being utilized in various applications to improve the quality of products. However, safety or toxicity information of dolomite NPs is largely lacking. This study evaluated the cytotoxicity of dolomite NPs in two widely used in vitro cell culture models: human airway epithelial (HEp2) and human liver (HepG2) cells. Concentration-dependent decreased cell viability and damaged cell membrane integrity revealed the cytotoxicity of dolomite NPs. We further observed that dolomite NPs induce oxidative stress in a concentration-dependent manner, as indicated by depletion of glutathione and induction of reactive oxygen species (ROS) and lipid peroxidation. Quantitative real-time PCR data demonstrated that the mRNA level of tumor suppressor gene p53 and apoptotic genes (bax, CASP3 and CASP9) were up-regulated whereas the anti-apoptotic gene bcl-2 was down-regulated in HEp2 and HepG2 cells exposed to dolomite NPs. Moreover, the activity of apoptotic enzymes (caspase-3 and caspase-9) was also higher in both kinds of cells treated with dolomite NPs. It is also worth mentioning that HEp2 cells seem to be marginally more susceptible to dolomite NPs exposure than HepG2 cells. Cytotoxicity induced by dolomite NPs was efficiently prevented by N-acetyl cysteine treatment, which suggests that oxidative stress is primarily responsible for the cytotoxicity of dolomite NPs in both HEp2 and HepG2 cells. Toxicity mechanisms of dolomite NPs warrant further investigations at the in vivo level.

  19. Critical deep drill holes and indicated Paleozoic paleotectonic features north of the Snake River downwarp in southern Beaverhead County, Montana, and adjacent Idaho

    Science.gov (United States)

    Perry, W.J.

    1986-01-01

    Hydrologic testing was conducted in 1980 and 1981 at wells at hydrologic test pads H-7, H-8, H-9, and H-10 near the proposed Waste Isolation Pilot Plant site in southeastern New Mexico. Tests were conducted in three zones above the horizon of the proposed underground storage facility. The zones are the Magenta Dolomite Member of the Rustler Formation, the Culebra Dolomite Member of the Rustler Formation, and the Rustler Formation-Salado Formation contact zone. Data presented are from bailing tests, density profiles, shut-in tests, slug tests, flow tests, pressure-pulse tests, and pumping tests. (USGS)

  20. STRUCTURAL AND GEOCHEMICAL CHARACTERISTICS OF SECONDARY DOLOMITIC BODIES OF CRETACEOUS COLIMA-JALISCO BASIN, WESTERN MEXICO

    Science.gov (United States)

    Zarate, P. F.

    2009-12-01

    The cretaceous Colima-Jalisco basin, at western Mexico, is characterized by the development of volcano sedimentary sequences belonging to the Late Jurassic-Early Cretaceous Alisitos-Teloloapan arc-island and the formation of volcanogenic massive sulphide deposits ("El Cuale", "La Minita", "Talpa de Allende"). Some bodies of dolomite have been described and have been classified into two groups in accordance with its secondary origin: sabkha (diagenetic) and hydrothermal. In both cases the primary dolomitized limestone belongs to the reef facies of the Tepalcatepec Formation (TF) of Albian-Cenomanian characterized by the next geochemical content: MgO (0.42%), CaO (53.7%), SiO2 (0.15%), Pb (140 ppm) and Zn (50 ppm). Diagenetical dolomite is characterized by an stratiform body and its contacts are consistent with the structural attitude of TF to which it belongs. In the dolomites formed by hydrothermal replacement process is limited by faults and fractures, thus its morphology is irregular and their contacts are discordant, adopting domic or columnar forms. Occasionally hydrothermal dolomite can be associated with concentrations of lead, zinc, silver and barite. The dolomitic body called "Cerro El Puro", (19° 3.7' N; 103° 36.7' W), located at 20 km SE 30° from Colima City, consists in a carbonate horizon of 300 m thick and over 5 km in length and is consistent with the structural attitude (N30°W; NE50°) of the southwestern flank of the syncline Tepames-Amarradero, in which southeast extreme an evaporitic stratiform deposits. The dolomite of this body is of ankeritic type, hence its typical light reddish brown. The geochemical content is shown on Table 1. After the structural and geochemical features of this dolomite, it is classified as sabkha with a diagenetic origin. The other dolomitic outcrop studied is called “Cerro Bola” (18°54'N; 103°47.5'W) which is located 40 km S10°W from Colima City, and consists of a single dolomitic outcrop, black in color

  1. Secondary Magnetization of ZEBRA Dolomites in the Basin and Range Province of Eastern Nevada

    Science.gov (United States)

    Elmore, R. D.; Dulin, S. A.

    2013-12-01

    Zebra dolomites within the Devonian Guilmette Formation of the southern Basin and Range Province, Nevada, are the focus of a paleomagnetic study to determine if a characteristic magnetization exists that will yield insight into the timing of zebra dolomite formation. Zebra dolomites consist of alternating bands of light and dark dolomite, and are found throughout Nevada, often associated with mineralized ore deposits. Although a variety of mechanisms have been suggested for formation, the zebra dolomite throughout Nevada is likely associated with hydrothermal fluid migration. The current study focuses on zebra dolomites that have formed in close stratigraphic proximity and within the Alamo Breccia in the Delamar Range in southeastern Nevada. The Alamo Breccia is an impact generated mega-breccia zone within the Devonian Guilmette Formation. The zebra dolomites, including those in the Alamo Breccia, and host Guilmette in the Delamar Range have a characteristic remanent magnetization (ChRM) with maximum laboratory unblocking temperatures of 480°C that is interpreted to reside in magnetite. The rocks were structurally rotated to remove Cenozoic extension, and the stratigraphic mean direction of the ChRM has a declination of 164.4°, with an inclination of -3°. The calculated pole is at 51.6°N, 90.7°E (dp = 2.2, dm = 4.3) which lies near the late Triassic portion of the apparent polar wander path (APWP) for North America. Based on low burial temperatures, this ChRM is interpreted as a chemical remanent magnetization (CRM) that was acquired due to the mobilization of brines possibly associated with the Triassic Sonoma orogeny. Geochemical data are consistent with alteration by externally derived fluids. The presence of a late Triassic magnetization indicates that the zebra dolomite can be no younger than Late Triassic. Preliminary results from zebra dolomites in other areas in southeastern Nevada indicate a more complex magnetization; some locations contain both

  2. Suboxic dolomite formation linked to the sedimentary Mn cycle, Archipelago Los Roques, Venezuela

    Science.gov (United States)

    Petrash, D.; Lalonde, S.; Gonzalez, G.; Gingras, M.; Konhauser, K.

    2013-12-01

    The preferential formation of Ca-rich dolomite precursors in modern peritidal environments has been associated with the degradation of buried microbial mats, with complexation of Ca and Mg cations by extracellular polysaccharides, and alkalinity generation, mostly through bacterial sulfate reduction. However, it remains unclear why Ca-dolomite would not occur in suboxic sediments where bacterial Mn(IV) and/or Fe(III) reduction are important sources of alkalinity, and the role, if any, of Fe- and Mn-recycling in its diagenetic stabilization to more stoichiometric dolomite is unknown. In a shoaling-upward parasequence in the Archipelago Los Roques, Venezuela, an abundance of Ca-dolomite coincides with a relative decrease in bulk-sediment iron concentrations. These sediments were analyzed with multiple analytical tools, including EPMA, ICP-MS, synchrotron-based XRF, XRD, and spatially resolved XANES. Results demonstrate that the distribution of spheroidal aggregates of nanometer-scale Ca-rich dolomite rhombohedra is linked with interstitial elemental sulfur and manganese accumulations, with Mn occurring in several oxidation states (Fig. 1). Based on our observations at this novel dolomite-forming site, we suggest that in peritidal settings the burial of metal-reactive microbial mats act as a barrier capable of concentrating dissolved reactive species that promote greater sediment residence times in suboxic (manganic) zones, where the recycling of Mn not only plays an important role in the remineralization of organic matter, but also sustains elevated alkalinity and dissolved pore water sulfide concentrations. The last two effects have been previously suggested to promote Mg dehydration, the major kinetic barrier to dolomite nucleation. Figure 1. Normalized Mn K-edge merged spectra of a 5 x 5 μm analytical area bearing dolomite cements. A: The K-edge exhibits two main features at about 6554 and 6558 eV. B: Intermediate Mn (III) is identified by the positive slope of

  3. Nuevas adiciones a la fauna de crustáceos decápodos de Bahía Culebra, Guanacaste, Costa Rica

    Directory of Open Access Journals (Sweden)

    Rita Vargas-Castillo

    2012-04-01

    Full Text Available La fauna de crustáceos de Bahía Culebra, Guanacaste, Pacífico norte de Costa Rica, fue estudiada antes de la década de 1940. Basado en recolectas, principalmente de las últimas dos décadas y depositadas en el Museo de Zoología, Universidad de Costa Rica, se presentan aquí 15 nuevos registros de crustáceos decápodos pertenecientes a 11 familias. Estos registros se suman a las 94 especies conocidas previamente para la bahía, para un total de 109 especies de crustáceos decápodos y 130 de crustáceos. Probablemente hay más especies ya que algunos ambientes no han sido estudiados, como tampoco los microcrustáceos bénticos. Este tipo de estudio de línea base es importante especialmente en regiones donde se están dando alteraciones ambientales muy rápidas.

  4. Kinetic modeling of liquid-phase adsorption of phosphate on dolomite.

    Science.gov (United States)

    Karaca, S; Gürses, A; Ejder, M; Açikyildiz, M

    2004-09-15

    The adsorption of phosphate from aqueous solution on dolomite was investigated at 20 and 40 degrees C in terms of pseudo-second-order mechanism for chemical adsorption as well as an intraparticle diffusion mechanism process. Adsorption was changed with increased contact time, initial phosphate concentration, temperature, solution pH. A pseudo-second-order model and intraparticle diffusion model have been developed to predict the rate constants of adsorption and equilibrium capacities. The activation energy of adsorption can be evaluated using the pseudo-second-order rate constants. The adsorption of phosphate onto dolomite are an exothermically activated process. A relatively low activation energy and a model highly fitting to intraparticle diffusion suggest that the adsorption of phosphate by dolomite may involve not only physical but also chemisorption. This was likely due to its combined control of chemisorption and intraparticle diffusion. However, for phosphate/dolomite system chemical reaction is important and significant in the rate-controlling step, and for the adsorption of phosphate onto dolomite the pseudo-second-order chemical reaction kinetics provides the best correlation of the experimental data.

  5. Structures of dolomite at ultrahigh pressure and their influence on the deep carbon cycle.

    Science.gov (United States)

    Merlini, Marco; Crichton, Wilson A; Hanfland, Michael; Gemmi, Mauro; Müller, Harald; Kupenko, Ilya; Dubrovinsky, Leonid

    2012-08-21

    Carbon-bearing solids, fluids, and melts in the Earth's deep interior may play an important role in the long-term carbon cycle. Here we apply synchrotron X-ray single crystal micro-diffraction techniques to identify and characterize the high-pressure polymorphs of dolomite. Dolomite-II, observed above 17 GPa, is triclinic, and its structure is topologically related to CaCO(3)-II. It transforms above 35 GPa to dolomite-III, also triclinic, which features carbon in [3 + 1] coordination at the highest pressures investigated (60 GPa). The structure is therefore representative of an intermediate between the low-pressure carbonates and the predicted ultra-high pressure carbonates, with carbon in tetrahedral coordination. Dolomite-III does not decompose up to the melting point (2,600 K at 43 GPa) and its thermodynamic stability demonstrates that this complex phase can transport carbon to depths of at least up to 1,700 km. Dolomite-III, therefore, is a likely occurring phase in areas containing recycled crustal slabs, which are more oxidized and Ca-enriched than the primitive lower mantle. Indeed, these phases may play an important role as carbon carriers in the whole mantle carbon cycling. As such, they are expected to participate in the fundamental petrological processes which, through carbon-bearing fluids and carbonate melts, will return carbon back to the Earth's surface.

  6. Dolomite-rich coralline algae in reefs resist dissolution in acidified conditions

    Science.gov (United States)

    Nash, M. C.; Opdyke, B. N.; Troitzsch, U.; Russell, B. D.; Adey, W. H.; Kato, A.; Diaz-Pulido, G.; Brent, C.; Gardner, M.; Prichard, J.; Kline, D. I.

    2013-03-01

    Coral reef ecosystems develop best in high-flow environments but their fragile frameworks are also vulnerable to high wave energy. Wave-resistant algal rims, predominantly made up of the crustose coralline algae (CCA) Porolithon onkodes and P. pachydermum, are therefore critical structural elements for the survival of many shallow coral reefs. Concerns are growing about the susceptibility of CCA to ocean acidification because CCA Mg-calcite skeletons are more susceptible to dissolution under low pH conditions than coral aragonite skeletons. However, the recent discovery of dolomite (Mg0.5Ca0.5(CO3)), a stable carbonate, in P. onkodes cells necessitates a reappraisal of the impacts of ocean acidification on these CCA. Here we show, using a dissolution experiment, that dried dolomite-rich CCA have 6-10 times lower rates of dissolution than predominantly Mg-calcite CCA in both high-CO2 (~ 700ppm) and control (~ 380ppm) environments, respectively. We reveal this stabilizing mechanism to be a combination of reduced porosity due to dolomite infilling and selective dissolution of other carbonate minerals. Physical break-up proceeds by dissolution of Mg-calcite walls until the dolomitized cell eventually drops out intact. Dolomite-rich CCA frameworks are common in shallow coral reefs globally and our results suggest that it is likely that they will continue to provide protection and stability for coral reef frameworks as CO2 rises.

  7. Structures of dolomite at ultrahigh pressure and their influence on the deep carbon cycle

    Science.gov (United States)

    Merlini, Marco; Crichton, Wilson A.; Hanfland, Michael; Gemmi, Mauro; Müller, Harald; Kupenko, Ilya; Dubrovinsky, Leonid

    2012-01-01

    Carbon-bearing solids, fluids, and melts in the Earth's deep interior may play an important role in the long-term carbon cycle. Here we apply synchrotron X-ray single crystal micro-diffraction techniques to identify and characterize the high-pressure polymorphs of dolomite. Dolomite-II, observed above 17 GPa, is triclinic, and its structure is topologically related to CaCO3-II. It transforms above 35 GPa to dolomite-III, also triclinic, which features carbon in [3 + 1] coordination at the highest pressures investigated (60 GPa). The structure is therefore representative of an intermediate between the low-pressure carbonates and the predicted ultra-high pressure carbonates, with carbon in tetrahedral coordination. Dolomite-III does not decompose up to the melting point (2,600 K at 43 GPa) and its thermodynamic stability demonstrates that this complex phase can transport carbon to depths of at least up to 1,700 km. Dolomite-III, therefore, is a likely occurring phase in areas containing recycled crustal slabs, which are more oxidized and Ca-enriched than the primitive lower mantle. Indeed, these phases may play an important role as carbon carriers in the whole mantle carbon cycling. As such, they are expected to participate in the fundamental petrological processes which, through carbon-bearing fluids and carbonate melts, will return carbon back to the Earth’s surface. PMID:22869705

  8. A role for calcium hydroxide and dolomite in water: acceleration of the reaction under ultraviolet light.

    Science.gov (United States)

    Nagase, Hiroyasu; Tsujino, Hidekazu; Kurihara, Daisuke; Saito, Hiroshi; Kawase, Masaya

    2014-04-01

    Organic environmental pollutants are now being detected with remarkably high frequency in the aquatic environment. Photodegradation by ultraviolet light is sometimes used as a method for removing organic chemicals from water; however, this method is relatively inefficient because of the low degradation rates involved, and more efficient methods are under development. Here we show that the removal of various organic pollutants can be assisted by calcined dolomite in aqueous solution under irradiation with ultraviolet light. It was possible to achieve substantial removal of bisphenol A, chlorophenols, alkylphenols, 1-naphthol and 17β-estradiol. The major component of dolomite responsible for the removal was calcium hydroxide. Our results demonstrate that the use of calcium hydroxide with ultraviolet light irradiation can be a very effective method of rapidly removing organic environmental pollutants from water. This is a new role for calcium hydroxide and dolomite in water treatment.

  9. Optimization Study in Biodiesel Production via Response Surface Methodology Using Dolomite as a Heterogeneous Catalyst

    Directory of Open Access Journals (Sweden)

    Regina C. R. Santos

    2014-01-01

    Full Text Available A carbonate mineral, dolomite, was used as a heterogeneous catalyst to produce methyl-esters from soybean oil. The samples were analyzed by XRF, TGA, XRD, TPD-CO2, and SEM. The calcination of dolomite at 800°C/1 h resulted in a highly active mixed metal oxides. In addition, the influence of the reaction variables such as the temperature, catalyst amount, and methanol/soybean oil molar ratio in methyl-ester production was optimized by the application of a central composite design in conjunction with the response surface methodology (RSM. The XRF analysis is carried out after the reuses procedure which shows that the deactivation process is mainly due to the selective calcium leaching. Overall, the calcined dolomite exhibited high catalytic activity at moderate operating conditions for biodiesel production.

  10. Effect of dolomite on reduction swelling property of iron ore pellets

    Institute of Scientific and Technical Information of China (English)

    许斌; 侯通; 陈许玲; 李骞; 姜涛; 李鹏

    2013-01-01

    The effect of various dosages of dolomites on the reduction swelling property of iron ore pellets was studied. Experimental results show that the reduction swelling index(RSI) decreases from 13.35% to 4.0%, while the porosity of roasted pellets increases from 35% to 40% with increasing the dolomite dosage from 0 to 10.5%. Meanwhile, the content of magnesium ferrite with high melting temperature, as well as the stability of magnetite(Fe3 O4) in the roasted pellets, increases with increasing the magnesium oxide(MgO) content from dolomite. The reasons for the decrease of RSI rely on the absence of crystal transformation from Fe2 O3 to Fe3 O4, the increased porosity of roasted pellet, and the suppression of phase transition of 2CaO·SiO2 resulted from the incorporation of magnesium into calcium silicate.

  11. Onset of Crack Initiation in Uniaxial and Triaxial Compression Tests of Dolomite Samples

    Directory of Open Access Journals (Sweden)

    Cieślik Jerzy

    2014-03-01

    Full Text Available The paper presents results of laboratory investigation and analysis of crack initiation threshold identification of dolomite samples. First, selected methods for determining crack initiation thresholds are briefly described with special attention paid to four methods: crack volume strain method [14], change in Poisson’s ratio [8], lateral strain response method [16], and dilatancy method [4]. The investigation performed on dolomite samples shows that for the uniaxial and conventional triaxial compression tests, the above mentioned methods give quite similar values, except for the crack volume strain method. Crack initiation threshold determined by this method has a distinctively lower value than that obtained by the other methods. The aim of the present paper was to review and assess these methods for identifying crack initiation threshold based on laboratory tests of dolomite samples.

  12. 四川盆地南江栖霞组白云岩岩石学、地球化学特征及成因%Petrologic and geochemical characteristics and the origin of dolomites in the Qixia Formation in Nanjiang county of the Sichuan Basin

    Institute of Scientific and Technical Information of China (English)

    李小宁; 黄思静; 黄树光; 黄可可; 袁桃; 罗文

    2016-01-01

    四川盆地南江桥亭剖面中二叠统栖霞组二段灰岩局部白云岩化,基质白云岩主要由非平直晶面他形晶白云石构成,孔洞缝中充填鞍形白云石和结晶方解石,溶解作用主要发生在白云石中。在岩石学研究基础上,综合运用碳氧同位素、元素、包裹体均一化温度、阴极发光测试手段,结合埋藏史、热史以及峨眉山玄武岩喷发非正常地热增温事件,研究了基质白云石和鞍形白云石的特征和成因。研究表明:基质白云石、鞍形白云石和结晶方解石的包裹体均一化温度分别为100~110,130~230,130~230℃;富含基质白云石、鞍形白云石和结晶方解石样品的δ18 OPDB值分别为-4.27‰~-6.28‰,-4.87‰~-5.80‰,-5.16‰~-6.50‰,δ13 CPDB值分别为3.97‰~5.22‰,4.88‰~5.35‰,2.73‰~4.29‰;与基质白云岩相比较,鞍形白云石和结晶方解石的δ18 O值略负,并显示三者碳源为同时期海水。反演的基质白云岩形成流体的δ18 OSMOW值分布在3‰~6‰之间,鞍形白云石δ18 OSMOW主要分布在7‰~14‰之间,盐度均显著高于同期海水,因而两者都是在高温和高盐度的流体中形成的。三者都受到了峨眉山玄武岩喷发活动所引起的热事件影响,高温和高盐度克服了白云石沉淀的动力学屏障,形成交代灰岩的基质白云岩和孔洞缝中充填的鞍形白云石,流体的持续高温和Mg2+的消耗,导致了高温方解石的沉淀,显示热液对碳酸盐岩的改造作用。%Limestones are locally dolomitized in the 2nd member of the Middle Permian Qixia Formation of Qiaoting section, located in Nanjiang county of the Sichuan Basin. Matrix dolomites primarily consist of non⁃planar xenotopic dolomite crystals, and vugs and fractures are filled with saddle dolomites and crystalline calcites. Dissolution occurs mainly in dolomites

  13. {sup 226} Ra committed effective dose assessment for osteoporosis treatment with `Gran-White` dolomite

    Energy Technology Data Exchange (ETDEWEB)

    Pecequilo, Brigitte R.S.; Campos, Marcia P. de [Instituto de Pesquisas Energeticas e Nucleares (IPEN), Sao Paulo, SP (Brazil)

    1997-12-01

    A total of 6 dolomite samples were prepared for activity concentration measurement by using high resolution gamma-ray spectrometry. The calculated average specific activity of {sup 226} Ra was 4.34 Bq/kg. The committed effective dose due to the Ra-226 specific activity in dolomite was performed following the ICRP 30 and ICRP 61 procedures and dose conversion factors. Values of 1.95 x 10{sup -6} Sv were obtained for committed effective dose and 5.93 x 10{sup -5} Sv for committed dose equivalent in the bone surface. (author). 9 refs., 2 tabs.

  14. Ferroan dolomite cement in Cambrian sandstones: burial history and hydrocarbon generation of the Baltic sedimentary basin

    DEFF Research Database (Denmark)

    Sliaupa, S.; Cyziene, J.; Molenaar, Nicolaas

    2008-01-01

    . The burial history modelling points to development of most of the dolomite cement during rapid Silurian-Devonian subsidence and Carboniferous-early Permian uplift. A wide range of precipitation temperatures indicate that temperature was not a major factor in triggering the carbonate cementation. Dolomite...... precipitation is related to early stages of organic matter maturation and thus to the oil generation history in the basin. delta C-13 values vary from +0.03% to -6.2%( PDB), suggesting limited addition of carbon from an organic source, with the major part derived from marine bicarbonate. The sourcing of carbon...

  15. Assessing dolomite surface reactivity at temperatures from 40 to 120 °C by hydrothermal atomic force microscopy

    Science.gov (United States)

    Berninger, Ulf-Niklas; Saldi, Giuseppe D.; Jordan, Guntram; Schott, Jacques; Oelkers, Eric H.

    2017-02-01

    This study investigated the reactivity of the (1 0 4) dolomite surface in the system MgCO3-CaCO3-NaCl-H2O via a suite of aqueous solution-dolomite hydrothermal atomic force microscopy interaction experiments at temperatures from 40 to 120 °C, pH ranging from 4 to 8, pressures up to 5 bars, and over a wide range of aqueous fluid saturation state. Dolomite dissolution was observed in the presence of undersaturated aqueous fluids. Dissolution produced crystallographically well defined etch pits, consistent with the stoichiometric release of ordered lattice cations. In low to moderately saturated fluids, dolomite growth began by the growth of one or two layers of carbonate (layer height dolomite surfaces at moderate rates, but these did not exhibit the characteristic dolomite crystallographic orientation after the growth of several layers. Taken together these observations suggest that the direct precipitation of dolomite from aqueous solution is disfavored at temperatures to at least 120 °C due to the poisoning of the dolomite surface for further growth by the precipitation of one to four Ca-Mg carbonate layers on these surfaces.

  16. STEM investigation of exsolution lamellae and "c" reflections in Ca-rich dolomite from the Platteville Formation, western Wisconsin

    CERN Document Server

    Shen, Zhizhang; Brown, Philip E; Xu, Huifang

    2016-01-01

    Dolomite crystals in partially dolomitized limestone from the Platteville Formation are both compositionally and microstructurally heterogeneous. A single dolomite crystal usually contains three phases: the host Ca-rich dolomite [Ca1.14Mg0.86(CO3)2], an Fe-bearing dolomite [Ca1.06Mg0.80Fe0.14(CO3)2], and calcite inclusions. These three phases show similar orientations. The Ca-rich dolomite exhibits modulated microstructures with wavelength ranging from 7 to 30 nm. The modulated microstructures are not evident in Fe-bearing dolomite. Modulations in the Ca-rich dolomite have three predominant orientation ranges in the studied sample: from (205) to (104), from (001) to (-101), and ~(110), which are consistent with previous studies. Bright-field (BF) and high-angle annular dark-field (HAADF) images confirm that these modulations are due to chemical variation rather than strain or diffraction contrast. The Ca-rich lamellae are Mg-rich calcite with compositions ranging from Ca0.85Mg0.15CO3 to Ca0.70Mg0.30CO3. The o...

  17. Test holes drilled in support of ground-water investigations, Project Gnome, Eddy County, New Mexico

    Science.gov (United States)

    Cooper, J.B.

    1962-01-01

    Project Gnome is a proposed underground nuclear shot to be detonated within a massive salt bed in Eddy County, N. Mex. Potable and neat potable ground water is present in rocks above the salt and is being studied in relation to this nuclear event. This report presents details of two test holes which were drilled to determine ground-water conditions in the near vicinity of the shot point. A well-defined aquifer is present at the site of USGS test hole 1, about 1,000 feet south of the access shaft to the underground shot point. Water with 75 feet of artesian pressure head is contained in the Culebra dolomite member of the Rustler formation. The dolomite aquifer is 32 feet thick and its top lies at a depth of 517 feet below land surface. The aquifer yielded 100 gpm (gallons per minute) with a drawdown of 40 feet during a pumping period of 24 hours. Water was not found in rocks above or below the Culebra dolomite. At the site of USGS test hole 2, about 2 miles southwest of the access shaft no distinctive aquifer exists. About one-half gpm was yielded to the well from the rocks between the Culebra dolomite and the top of the salt. Water could not be detected in the Culebra dolomite or overlying rocks. The report contains drawdown and recovery curves of yield tests, drilling-time charts, and electric logs. The data are given in tables; they include summaries of hole construction, sample description logs, water measurements, drilling-time logs, and water analyses.

  18. Spatial variations in the stoichiometry and geochemistry of Miocene dolomite from Grand Cayman: Implications for the origin of island dolostone

    Science.gov (United States)

    Ren, Min; Jones, Brian

    2017-03-01

    The Cayman Formation (Miocene), 140 m thick on Grand Cayman, is incompletely dolomitized with the most of the dolomite restricted to the peripheral part of the island. These calcium-rich dolomites, with 50-60 mol%CaCO3 (%Ca), are divided into low-calcium dolomite (LCD, %Ca 55%). Despite the small size of the island (6.8 km wide), the percentages of LCD and HCD, the %Ca, and the geochemical properties of the dolomites show geographic variations relative to the surrounding shelf edge. Accordingly, the Cayman Formation on the east end of the island is divided into the peripheral dolostone (shelf edge-1.5 km inland), transitional dolostone (1.5-2.7 km inland), and the interior limestone and dolostone (2.7 km to island center). From the peripheral dolostone to the interior limestone and dolostone, there is an increase in the percentage of HCD and %Ca in the dolomite, and decreases in the δ18O and δ13C values of the dolomite. Interpretations based on the oxygen and carbon isotopic compositions indicate that seawater is the source of Mg for dolomitization. The concentric pattern of dolomitization on the island reflects the fact that seawater flowed into the island from all directions during dolomitization. The lateral inland variations in the dolomite stoichiometric and isotopic properties reflect the gradual modification of seawater by water-rock interaction along the flow path from the shelf edge to the island center. 87Sr/86Sr ratios indicate that two phases of dolomitization (late Miocene-early Pliocene and late Pliocene-early Pleistocene) were responsible for dolomitization of the Cayman Formation. It is very likely that during both phases, the carbonate platform was subaerially exposed and that the pump for circulating the seawater through the island was related to the seawater/freshwater mixing zone. The dolomitization model developed from Grand Cayman may be applicable to many other island dolostones affected by long-term sea-level changes. Given that the

  19. La cervatina bendita y la serpiente maldita: la lucha mítica del ciervo y la serpiente y un conjuro asturiano contra la culebra (narrativa e iconografía)

    OpenAIRE

    Suárez López, Jesús

    2007-01-01

    Análisis de unos conjuros mágicos asturianos, tradicionales entre los vaqueiros de alzada, para curar la picadura de la culebra. Tienen como motivo central el de la lucha del ciervo y la serpiente. Se estudian los antecedentes literarios e iconográficos del tópico, desde la antigüedad hasta hoy, en muchas culturas, y su relación con leyendas como la de San Huberto o con antiguos mitos del México prehispánico. This paper studies a magical Asturian spell, traditional among the vaquiros de al...

  20. Composición y distribución del mesozooplancton en una zona de afloramiento costero (Bahía Culebra, Costa Rica durante La Niña 1999 y el 2000

    Directory of Open Access Journals (Sweden)

    Karina Rodríguez-Sáenz

    2012-04-01

    Full Text Available Se estudian los patrones anuales de la composición, abundancia y distribución espacial-temporal de mesozooplancton en la zona de afloramiento de Bahía Culebra, en la costa norte del Pacífico de Costa Rica. Bahía Culebra presenta una alta variabilidad en las condiciones físico-químicas y se encontraron 26 grupos de mesozooplancton (meroplanctónicas y holoplanctónicos. Los copépodos (2 358.53 ± 2 290.90ind./m³, ostrácodos (1 084.46 ± 1 850.20ind./m³ y huevos de invertebrados (844.26 ±7069.27ind./m³ fueron los grupos dominantes. Hubo mayores abundancias en 1999 que en el 2000, con la excepción de apendicularias y larvas de crustáceos. El zooplancton fue más abundante en la época seca de ambos años. Las estaciones de la boca muestran un flujo oceánico de formas holoplanctónicos, mientras que el interior de la bahía meroplanctónicas fueron importantes las formas. La abundancia y distribución del mesozooplancton parecen reflejar los pulsos de surgencia costera.We studied the annual patterns of composition, abundance and spacial-temporal distribution of mesozooplankton in the upwelling zone of Culebra Bay, north Pacific coast of Costa Rica, during the 1999 La Niña event and in 2000. The Bay showed a high variability in physical-chemical conditions during the study period in which 26 mesozooplankton groups (both meroplanktonic and holoplanktonic forms were found. The copepods (2 358.53 ± 2 290.90ind/m³, ostracods (1 084.46 ± 1 850.20ind/m³ and invertebrate eggs (844.26 ± 7069.27ind/ m³ were the most abundant groups in Bahía Culebra. All mesozooplankton (0.2-2 mm data showed high spatial-temporal variability although differences were not significant. Higher abundances were found during 1999, with the exception of appendicularians and crustacean larvae. Higher zooplankton abundances were observed during the dry season of both years. Stations close to the mouth show an oceanic influx of holoplanktonic forms, while inside

  1. Effect and mechanism of dolomite with different size fractions on hematite flotation using sodium oleate as collector

    Institute of Scientific and Technical Information of China (English)

    LUO Xi-mei; YIN Wan-zhong; WANG Yun-fan; SUN Chuan-yao; MA Ying-qiang; LIU Jian

    2016-01-01

    The effect of dolomite with different particle size fractions on hematite flotation was studied using sodium oleate as collector at pH of about 9. The effect mechanism of dolomite on hematite flotation was investigated by means of solution chemistry, ultraviolet spectrophotometry (UV), inductively coupled plasma atomic emission spectrometry (ICP-AES) and X-ray photoelectron spectroscopy (XPS). It is observed that dolomite with different size fractions has depressing effect on hematite flotation using sodium oleate as collector, and dolomite could be the "mineral depressant" of hematite using sodium oleate as collector. The reasons for that are concerned with sodium oleate consumption and the adsorption onto hematite of dissolved species of dolomite.

  2. Impact of upwelling events on the sea water carbonate chemistry and dissolved oxygen concentration in the Gulf of Papagayo (Culebra Bay, Costa Rica: Implications for coral reefs

    Directory of Open Access Journals (Sweden)

    Tim Rixen

    2012-04-01

    Full Text Available The Gulf of Papagayo, Pacific coast of Costa Rica, is one of the three seasonal upwelling areas of Mesoamerica. In April 2009, a 29-hour experiment was carried out at the pier of the Marina Papagayo, Culebra Bay. We determined sea surface temperature (SST, dissolved oxygen concentration, salinity, pH, and the partial pressure of CO2 (pCO2. The aragonite saturation state (Ωa as well as the other parameters of the marine carbonate system such as the total dissolved inorganic carbon (DIC and the total alkalinity (TA were calculated based on the measured pH and the pCO2. The entrainment of subsurface waters raised the pCO2 up to 645 µatm. SSTs, dissolved oxygen concentrations decreased form 26.4 to 23.7°C and from 228 to 144 µmol l-1. Ωa dropped down to values of 2.1. Although these changes are assumed to reduce the coral growth, the main reef building coral species within the region (Pocillopora spp. and Pavona clavus reveal growth rates exceeding those measured at other sites in the eastern tropical Pacific. This implies that the negative impact of upwelling on coral growth might be overcompensated by an enhanced energy supply caused by the high density of food and nutrients and more favorable condition for coral growth during the non-upwelling season.El Golfo de Papagayo, costa Pacífica de Costa Rica, es una de las tres regiones de afloramiento estacional de Mesoamérica. Las características físicas y químicas del agua que aflora no habían sido estudiadas. Durante 29 horas en Abril 2009, se estudiaron la temperatura superficial del mar (TSM, la concentración de oxígeno disuelto, salinidad, pH y la presión parcial de CO2 (pCO2, en la Marina Papagayo, Bahía Culebra. Con base en las mediciones de pH y pCO2 se calculó el estado de saturación de la aragonita (Ω y otros parámetros del sistema de carbonatos como lo es el carbono orgánico disuelto (COD y la alcalinidad total (AT. Los resultados indican que el arrastre por convecci

  3. Simply Understanding of Lacustrine Dolomite%对白云岩形成机理的再认识

    Institute of Scientific and Technical Information of China (English)

    蔡雪峰; 闫志为; 夏源

    2016-01-01

    Dolomite usually can form one of the best oil and gas accumulation in carbonate. Multiresolution is directly de-termined by the understanding of genetic evolution and reservoir spatial distribution of dolomite. However the origin of dolomite is quite complex and difficult to solve in long term in the domain of carbonate petrology. According to the different mechanism, all the current main dolomite can be classified into two styles:primary dolomites and secondary dolomites. Whether they be-long to the real primary dolomites still needs further research,large numbers of primary dolomites have been found. It is par-ticularly important for the understanding of dolomite and carbonate reservoirs for oil and gas exploration to clarify the origin of dolomite.%在碳酸盐岩体系中,白云岩通常能形成最好的储层.对白云岩成因演化和储层展布的认识直接决定勘探部署.而白云岩成因是碳酸盐岩岩石学中最复杂、争论时间最久、最难解决的问题之一.根据机理的不同,当前各种主要的白云岩成因模式可划分为两大类:原生白云石模式和次生白云石化模式.虽然原生白云石的例子已被大量发现,但它们是否属真正的原生白云石仍需后续研究;理清白云岩成因问题,对认识白云岩及其相关的碳酸盐岩储层的油气勘探工作尤为重要.

  4. Influence of ameliorating soil acidity with dolomite on the priming of soil C content and CO2 emission.

    Science.gov (United States)

    Shaaban, Muhammad; Wu, Lei; Peng, Qi-An; van Zwieten, Lukas; Chhajro, Muhammad Afzal; Wu, Yupeng; Lin, Shan; Ahmed, Muhammad Mahmood; Khalid, Muhammad Salman; Abid, Muhammad; Hu, Ronggui

    2017-02-21

    Lime or dolomite is commonly implemented to ameliorate soil acidity. However, the impact of dolomite on CO2 emissions from acidic soils is largely unknown. A 53-day laboratory study was carried out to investigate CO2 emissions by applying dolomite to an acidic Acrisol (rice-rapeseed rotation [RR soil]) and a Ferralsol (rice-fallow/flooded rotation [RF soil]). Dolomite was dosed at 0, 0.5, and 1.5 g 100 g(-1) soil, herein referred to as CK, L, and H, respectively. The soil pH(H2O) increased from 5.25 to 7.03 and 7.62 in L and H treatments of the RR soil and from 5.52 to 7.27 and 7.77 in L and H treatments of the RF soil, respectively. Dolomite application significantly (p ≤ 0.001) increased CO2 emissions in both RR and RF soils, with higher emissions in H as compared to L dose of dolomite. The cumulative CO2 emissions with H dose of dolomite were greater 136% in the RR soil and 149% in the RF soil as compared to CK, respectively. Dissolved organic carbon (DOC) and microbial biomass carbon (MBC) increased and reached at 193 and 431 mg kg(-1) in the RR soil and 244 and 481 mg kg(-1) in the RF soil by H treatments. The NH4(-)-N and NO3(-)-N were also increased by dolomite application. The increase in C and N contents stimulated microbial activities and therefore higher respiration in dolomite-treated soil as compared to untreated. The results suggest that CO2 release in dolomite-treated soils was due to the priming of soil C content rather than chemical reactions.

  5. Third Jesús Culebras Lecture: Molecular Biology and Clinical Nutrition; ¿where do we stand and where do we go?

    Directory of Open Access Journals (Sweden)

    Ángel Gil

    2013-04-01

    Full Text Available Nutrition plays a fundamental role in the maintenance of health and the treatment of disease, and serves as the crossroads for many disciplines. Biochemistry and Molecular Biology represents a key brand of science to ascertain the mechanism of action of nutrients and other food bioactive compounds in health and disease. The aim of the present Jesús M. Culebras lecture is to consider the future of the relationships between Molecular Biology and Clinical Nutrition and to discuss the use of molecular and genetic tools to study molecular responses to dietary factors and the metabolic consequences of food and to consider major challenges on human nutrition sciences in the 21st century. Particular emphasis is given to the identification and use of novel biomarkers in inflammatory diseases. Likewise, the importance of the human microbiome and how microorganisms can be safely utilized in the prevention and management of infectious and chronic diseases are discussed. Moreover, the key role of nutrigenetics, nutrigenomics and epigenetics in the new era of nutrition is considered. Nutrigenetics refers to the role of DNA sequence variation in the responses to nutrients, whereas nutrigenomics is the study of the role of nutrients in gene expression. Epigenetics is the study of mitotically heritable alterations in gene expression potential that are not caused by DNA sequence alterations. In the past decade, it has increasingly been recognized that dysregulation of epigenetic mechanisms may play an important role in human disease. Indeed, there is increasing interest in epigenetic mechanisms underlying phenotype modification modulated by nutrients. Further research in those areas should contribute to evaluate functionality of specific nutrients and bioactive compounds in Clinical Nutrition and allow personalized nutritional advice.

  6. Experimental Simulation of Dolomite Dissolution Under Burial Diagenesis Conditions and Thermodynamic Interpretation

    Institute of Scientific and Technical Information of China (English)

    黄思静; 肖林萍; 等

    2000-01-01

    Simulating experiments on dolomite dissolution by acetic acid were made under burial diagenesis conditions,at temperatures ranging from 75℃to 130℃ and pressures from 20 MPA to 30MPa,The results show that the dissolution rate of dolomite increased rapidly with increasing temperature and prssure,From 75℃/Mpa to 130℃/30 MPa,the total amount of released ca and Mg increased from 32.98mg/L to 337.9mg/L,over one order of magnitude in difference,Thermodynamic calculation indicates that the increment of Gibbs free energy (ΔG) of the chemical reaction decreases with increasing temperature and pressure.This thermodynamic result is consistent with the experimental result.Based on the Experimental results.it is suggested that secondary prosities formed by dolomite dissolution under conditions of deep burial diagenesis should be more common than those under epigenesis and shallow burial conditions,and therefore dolomite reservoires in the formations that have been deeply buried should be more abundant than in the formations that have only been shallowly buried.

  7. Greenhouse conditions induce mineralogical changes and dolomite accumulation in coralline algae on tropical reefs.

    Science.gov (United States)

    Diaz-Pulido, Guillermo; Nash, Merinda C; Anthony, Kenneth R N; Bender, Dorothea; Opdyke, Bradley N; Reyes-Nivia, Catalina; Troitzsch, Ulrike

    2014-01-01

    Human-induced ocean acidification and warming alter seawater carbonate chemistry reducing the calcification of reef-building crustose coralline algae (CCA), which has implications for reef stability. However, due to the presence of multiple carbonate minerals with different solubilities in seawater, the algal mineralogical responses to changes in carbonate chemistry are poorly understood. Here we demonstrate a 200% increase in dolomite concentration in living CCA under greenhouse conditions of high pCO2 (1,225 μatm) and warming (30 °C). Aragonite, in contrast, increases with lower pCO2 (296 μatm) and low temperature (28 °C). Mineral changes in the surface pigmented skeleton are minor and dolomite and aragonite formation largely occurs in the white crust beneath. Dissolution of high-Mg-calcite and particularly the erosive activities of endolithic algae living inside skeletons play key roles in concentrating dolomite in greenhouse treatments. As oceans acidify and warm in the future, the relative abundance of dolomite in CCA will increase.

  8. Colloid transport in dolomite rock fractures: effects of fracture characteristics, specific discharge, and ionic strength.

    Science.gov (United States)

    Mondal, Pulin K; Sleep, Brent E

    2012-09-18

    The effects of fracture characteristics, specific discharge, and ionic strength on microsphere transport in variable-aperture dolomite rock fractures were studied in a laboratory-scale system. Fractures with different aperture distributions and mineral compositions were artificially created in two dolomite rock blocks. Transport tests were conducted with bromide and carboxylate-modified latex microspheres (20, 200, and 500 nm diameter). Under overall unfavorable attachment conditions, there was significant retention of the 20 nm microsphere and minimal retention of the 500 nm microsphere for all conditions examined. Aperture variability produced significant spatial variation in colloid transport. Flushing with low ionic strength solution (1 mM) following microsphere transport at 12 mM ionic strength solution produced a spike in effluent microsphere concentrations, consistent with retention of colloids in secondary energy minima. Surface roughness and charge heterogeneity effects may have also contributed to the effect of microsphere size on retention. Matrix diffusion influenced bromide transport but was not a dominant factor in transport for any microsphere size. Calibrated one-dimensional, two-site kinetic model parameters for colloid transport in fractured dolomite were sensitive to the physical and chemical properties of both the fractured dolomite and the colloids, indicating the need for mechanistic modeling for accurate prediction.

  9. Greenhouse conditions induce mineralogical changes and dolomite accumulation in coralline algae on tropical reefs

    Science.gov (United States)

    Diaz-Pulido, Guillermo; Nash, Merinda C.; Anthony, Kenneth R. N.; Bender, Dorothea; Opdyke, Bradley N.; Reyes-Nivia, Catalina; Troitzsch, Ulrike

    2014-02-01

    Human-induced ocean acidification and warming alter seawater carbonate chemistry reducing the calcification of reef-building crustose coralline algae (CCA), which has implications for reef stability. However, due to the presence of multiple carbonate minerals with different solubilities in seawater, the algal mineralogical responses to changes in carbonate chemistry are poorly understood. Here we demonstrate a 200% increase in dolomite concentration in living CCA under greenhouse conditions of high pCO2 (1,225 μatm) and warming (30 °C). Aragonite, in contrast, increases with lower pCO2 (296 μatm) and low temperature (28 °C). Mineral changes in the surface pigmented skeleton are minor and dolomite and aragonite formation largely occurs in the white crust beneath. Dissolution of high-Mg-calcite and particularly the erosive activities of endolithic algae living inside skeletons play key roles in concentrating dolomite in greenhouse treatments. As oceans acidify and warm in the future, the relative abundance of dolomite in CCA will increase.

  10. Model study of initial adsorption of SO{sub 2} on calcite and dolomite

    Energy Technology Data Exchange (ETDEWEB)

    Malaga-Starzec, Katarina; Panas, Itai; Lindqvist, Oliver

    2004-01-30

    The rate of calcareous stone degradation is to a significant extent controlled by their surface chemistry with SO{sub 2}. Initial surface sulphite is converted to a harmful gypsum upon, e.g. NO{sub 2} catalysed oxidation. However, it has been observed by scanning electron microscopy that the lateral distributions of gypsum crystals differ between calcitic and dolomitic marbles. The first-principles density functional theory is employed to understand the origin of these fundamentally different morphologies. Here, the stability differences of surface sulphite at calcite CaCO{sub 3} (s) and dolomite Ca{sub x}Mg{sub 1-x}CO{sub 3} (s) are determined. A qualitative difference in surface sulphite stability, favouring the former, is reported. This is taken to imply that calcitic micro-crystals embedded in a dolomitic matrix act as sinks in the surface sulphation process, controlled by SO{sub 2} diffusion. The subsequent formation of gypsum under such conditions will not require SO{sub 4}{sup 2-} (aq) ion transport. This explains the homogeneous distribution of gypsum observed on the calcitic micro-crystals in dolomite. In contrast, sulphation on purely calcitic marbles never reaches such high SO{sub 2} coverage. Rather, upon oxidation, SO{sub 4}{sup 2-} (aq) transport to nucleation centres, such as grain boundaries, is required for the growth of gypsum crystals.

  11. Deep karstified dolomite aquifer as a source of drinking water - isotopic measurements

    Science.gov (United States)

    Bracic Zeleznik, Branka; Cencur Curk, Barbara; Zvab Rozic, Petra; Torkar, Anja; Vreca, Polona; Brencic, Mihael

    2017-04-01

    The Ljubljana Moor extends from the southern part of Ljubljana, the capital of Slovenia, to Krim-Mokrc karstic mountains. The sedimentation basin of Ljubljana Moor is filled up in the central part with lacustrine and marshy sediments and on the borders of the basin are the gravel fans. In the base of sedimentation basin is prequaternary karstified upper triasic dolomite. Ljubljana Moor aquifer is one of the biggest and very important drinking water sources in the central part of Slovenia. The water field Brest with 13 wells is situated in southern part of Moor, on I\\vska fan. The wells of different depth, from 28 m to 200 m, pump groundwater from various geological units, quaternary sediments and karstified dolomite. The land use on recharge area is agriculture and urbanization and in the last decade we monitor the deterioration of groundwater quality in quaternary sediments. In 2011 the 200 m deep well (VD Brest-3a) was drilled to catch the groundwater better quality in triasic dolomite that is in hydraulic connection with the karstic area in hinterland. To determine the recharge dynamic, origin and age of groundwater in dolomite, we provide several isotopic samplings on different depths. We measured oxygen (δ18O), deuterium (δ2H) and inorganic carbon (δ13CDIC). .

  12. Removal of low-concentration phosphorus using a fluidized raw dolomite bed.

    Science.gov (United States)

    Ayoub, George M; Kalinian, Houri

    2006-04-01

    Raw dolomite powder, obtained from dolomitic rocks, was evaluated for its efficiency in removing low concentrations of phosphate present in various water and wastewater matrices. A variety of experimental setups and process variables were tested, in an attempt to determine the optimal scheme (fluidized bed) that will be used to accomplish the objectives of the study. Test influents, including distilled water (DW), synthetic groundwater (SGW), tap water (TW), and sodium-hydroxide (NaOH)-alkalized wastewater treated with liquid bittern (STSE-B) and wastewater treated with lime (STSE-L) were used to assess the effect of influent parameters on the quality of the effluent generated. The adsorptive behavior of dolomite was described by fitting data generated from the study into the Freundlich and Langmuir isotherm models. Regeneration of the dolomite was attempted by the use of an acid (hydrochloric acid), DW, and an alkaline (NaOH). Test results indicate remarkable phosphate removal levels for DW and SGW. Removal levels of 100% were attained, for an average of 307 and 314 bed volumes at inflow concentration levels of 0.28 and 0.34 mg phosphate (PO4)/ L, respectively. Relative adsorption capacities were calculated to be 0.06 and 0.072 mg PO4/g of dolomite, respectively. For TW, STSE-L, and STSE-B, 100% removal before the start of the breakthrough was sustained for averages of 205, 94, and 28 bed volumes at phosphate dosages of 0.34, 0.56, and 0.6 mg PO4/L, respectively. The calculated adsorptive capacities were 0.05, 0.051, and 0.025, respectively. Zeta potential measurement resulted in values of -16.0 mV before treatment and +3.0 mV after complete exhaustion of the bed with PO4-jacked SGW influent, indicating an ionic adsorption of ions of opposite charge to that of the particle surface. Although both the Freundlich and Langmuir isotherms were found to fit the sorption curves, the Langmuir seems to better describe the sorption process in dolomite. Among the three

  13. U-Pb dating of speleogenetic dolomite: A new sulfuric acid speleogenesis chronometer

    Directory of Open Access Journals (Sweden)

    Victor Polyak

    2016-05-01

    Full Text Available The 1100-meter Big Room elevation level of Carlsbad Cavern, New Mexico USA, formed 4 Ma by hypogenic sulfuric acid speleogenesis (SAS. The age of the Big Room level of 4.0 ± 0.2 Ma was previously determined by dating alunite, a byproduct of speleogenesis, using the 40Ar/39Ar method. Duplication of these results is possible by radiometric dating of other byproducts interpreted to be speleogenetic (a byproduct of speleogenesis such as calcite and dolomite in certain settings. XRD and TEM analyses of sample 94044, a piece of crust collected within the Big Room level of SAS just below Left Hand Tunnel indicate that this dolomite sample we interpret to be speleogenetic is as well-ordered crystallographically as the Permian bedrock dolomite, possibly reflecting its SAS origin. Three U-Pb analyses were performed on subsamples A1, A2, and A3 of sample 94044, and two, A1 & A2, produced out-of-secular equilibrium results due to the presence of authigenic quartz and/or later re-distribution of uranium in the dolomite crust, which prevented the calculation of an isochron age. Because subsample 94044-A3 exhibited δ234U and 230Th/238U values consistent with secular equilibrium, we were able to generate a 238U/204Pb-206Pb/204Pb model age of 4.1 ± 1.3 Ma on the dolomite crust (94044 that we interpret to be reliable. The 4.1 Ma age of the speleogenetic dolomite crust agrees with the 4 Ma 40Ar/39Ar age for the timing of speleogenesis of the Big Room level. While 40Ar/39Ar-dating of speleogenetic alunite- and jarosite-group minerals remains the primary way to determine absolute timing of hypogenic SAS, here we demonstrate that U-Pb dating of speleogenetic dolomite can be used to compliment or independently measure the timing of SAS. This method of dating SAS could be applicable in caves where the more soluble SAS-indicator minerals such as gypsum, alunite, and jarosite have been removed.

  14. The formation of lacustrine dolomites: an example from the Tortonian-Messinian sequence at the East Mediterranean margins (northern Israel)

    Science.gov (United States)

    Shaked Gelband, Dotan; Starinsky, Abraham; Stein, Mordechai

    2017-04-01

    Lacustrine water bodies that filled the tectonic depressions in the Lower Galilee area of Israel during the Tortonian-Messinian periods deposited Bira and Gesher Formations, which comprise marly limestones and dolomites, basalts, and varying amounts of mollusc fossils. Most fossils are gastropods of fresh to brackish water origin, while marine representation is minor and comprise monospecific assemblages of euryhaline bivalves. During the deposition of the Tortonian Bira formation the lakes were mostly influenced by meteoric waters while during the deposition of the Messinian Gesher Formation they became more swampy. Here, we set to establish the deposition conditions of the dolomites in the lacustrine formations. The following petrographic characteristics indicate dolomitization of precursor carbonate sediment during early diagenesis stage: (1) Dolomitized fossils with similar texture as the surrounding dolomite matrix; (2) Common euhedral inner zone crystals, representing original growth in solution or plastic environment; (3) Subhedral outer shape derived from neighboring crystals collisions. More information is given by the δ18O and δ13C values of the dolomites. The δ18O of the inter-layered limestones and dolomites fluctuates between -3‰ to -4‰ (VPDB) in the limestones and +5‰ to -1.5‰ (VPDB) in the adjacent dolomites. These fluctuations are prominent in the Bira formation and become smaller along the sequence with the decrease in the dolomite values. δ13C values of both limestones and dolomites gradually decrease along the stratigraphic section, from -3.5‰ to -10‰ (VPDB) in the limestones, and from 0‰ to -8‰ (VPDB) in the dolomites. The data suggest a dolomitization process controlled by the following events: 1. Evaporation of fresh lake waters originated from the surrounding environment as runoff. It should be emphasized that significant evaporation could take place only in terminal lakes, during periods of relatively dry climate with low

  15. The effect of electrolytes on dolomite dissolution: nanoscale observations using in situ Atomic Force Microscopy

    Science.gov (United States)

    Urosevic, Maja; Ruiz-Agudo, Encarnacion; Putnis, Christine V.; Cardell, Carolina; Rodriguez-Navarro, Carlos; Putnis, Andrew

    2010-05-01

    Dissolution of carbonate minerals is one of the main chemical reactions occurring at shallow levels in the crust of the Earth and has a paramount importance for a wide range of geological and biological processes. Calcite (CaCO3), and to a lesser extent dolomite (CaMg(CO3)2), are the major carbonate minerals in sedimentary rocks and building stone materials. The dissolution of calcite has been thoroughly investigated over a range of conditions and solution compositions. In contrast, dolomite dissolution studies have been traditionally hampered by its low reaction rates compared to calcite and its poorly constrained relationship between cation ordering and reactivity (Morse and Arvidson, 2002). Yet important questions like the so-called 'dolomite problem' (e.g. Higgins and Hu, 2005) remain unresolved and more experimental work is needed in order to understand the role of other dissolved species, such as soluble salts, on the kinetics and mechanism of dolomite dissolution and precipitation. We have explored the effect of different electrolytes on the dissolution rate of dolomite by using in situ Atomic Force Microcopy (AFM). Experiments were carried out by passing alkali halide, nitrate and sulfate salt solutions (NaCl, KCl, LiCl, NaI, NaNO3 and Na2SO4) with different ionic strengths (IS = 10-3, 10-2 and 10-1) over dolomite {1014} cleavage surfaces. We show that all electrolytes tested enhance dolomite dissolution. Moreover, the morphology and density of etch pits are controlled by the presence of different ions in solution. The etch pit spreading rate and dolomite dissolution rate depend on both (1) the nature of the electrolyte and (2) the ionic strength. This is in agreement with recent experimental studies on calcite dissolution (Ruiz-Agudo et al., 2010). This study highlights the role of electrolytes in dolomite dissolution and points to a common behavior for carbonate minerals. Our results suggest that soluble salts may play a critical role in the weathering of

  16. Comparison of Amberlite IR 120 and dolomite's performances for removal of heavy metals.

    Science.gov (United States)

    Kocaoba, Sevgi

    2007-08-17

    The presence of heavy metals in the environment is major concern due to their toxicity. Contamination of heavy metals in water supplies has steadily increased over the last years as a result of over population and expansion of industrial activities. A strong cation-exchange resin, Amberlite IR 120 and a natural zeolite, dolomite were used for the removal of lead(II) and cadmium(II). The optimum conditions were determined in a batch system as concentration range was between 5 and 100 mg/L, pH range between 1 and 8, contact time between 5 and 90 min, and the amount of adsorbent was from 0.1 to 1g. A constant stirring speed, 2000 rpm, was chosen during all of the experiments. The optimum conditions were found to be a concentration of 20 mg/L, pH of 5, contact time of 60 min and 0.5 g of adsorbent. Also, for investigation of exchange equilibria different amounts of ion exchange resin and dolomite were contacted with a fixed volume and concentration of a heavy metal bearing solutions. Sorption data have been interpreted in terms of Langmuir and Freundlich equations. The effect of adsorption temperature on the heavy metals adsorption onto dolomite was investigated at three different temperatures (20, 40 and 60 degrees C). Thermodynamic parameters were calculated. The results obtained show that the Amberlite IR 120 strong cation-exchange resin and dolomite performed well for the removal of these heavy metals. As a low cost adsorbent, dolomite can preferable for removal of heavy metals from wastewaters.

  17. Important geosites and parks in the UNESCO World Heritage Site of the Dolomites

    Energy Technology Data Exchange (ETDEWEB)

    Nossing, L.; Forti, S.

    2016-10-01

    In the geological complexity of the south Tyrol, the Dolomites play a fundamental role, as they are now included in the UNESCO World Heritage (2009) because of their exceptional beauty and unique landscape, together with numerous scientific discoveries. The name of Dolomite comes from the famous mineral dolomite (double calcium magnesium carbonate) discovered by Déodat De Dolomieu in 1789. The dolomitic rocks constitute a large area of the Triassic mountains and many studies have contributed to the discovery of the fundamental stratotypes for the signature of the Permian/Triassic boundary. The steep walls of the Permian volcanic formations and the Sciliar Mountain have always been a great attraction for scientists from all over the world to study the open book of nature in the Dolomites. We will illustrate three sites: 1. The Bula Geotrail. A geological trail through one of the best-preserved sedimentary series in which we can observe one of the most important stratotypes to touch the Permian/Triassic boundary. 2. The Siusi-Alpe di Siusi Geological Trail. This trail starts just above the Permian/Triassic boundary and is characterized by some unique basaltic columnar formations and other significant outcrops of Lower and Medium Triassic. 3. The Bletterbach Geopark. In this sequence the stratotype, which represents the boundary, is a dark coloured continuous layer (organic matter) 5cm thick, and contains some paleobotanical evidence which is unique in the world. The preservation and added value of the natural and geological patrimony of a region through guided and documented trails are at the origin of a new kind of tourism: geotourism. The modern tourist is more and more interested and stimulated by getting to knowing nature in depth. The trails are the best instruments for scientific divulgation and education, allowing a better understanding of the landscape and stimulating new discoveries. (Author)

  18. Comparison of Amberlite IR 120 and dolomite's performances for removal of heavy metals

    Energy Technology Data Exchange (ETDEWEB)

    Kocaoba, Sevgi [Yildiz Technical University, Faculty of Art and Science, Department of Chemistry, Davutpasa Cad. No: 127, 34210 Davutpasa, Istanbul (Turkey)]. E-mail: kocaoba@yildiz.edu.tr

    2007-08-17

    The presence of heavy metals in the environment is major concern due to their toxicity. Contamination of heavy metals in water supplies has steadily increased over the last years as a result of over population and expansion of industrial activities. A strong cation-exchange resin, Amberlite IR 120 and a natural zeolite, dolomite were used for the removal of lead(II) and cadmium(II). The optimum conditions were determined in a batch system as concentration range was between 5 and 100 mg/L, pH range between 1 and 8, contact time between 5 and 90 min, and the amount of adsorbent was from 0.1 to 1 g. A constant stirring speed, 2000 rpm, was chosen during all of the experiments. The optimum conditions were found to be a concentration of 20 mg/L, pH of 5, contact time of 60 min and 0.5 g of adsorbent. Also, for investigation of exchange equilibria different amounts of ion exchange resin and dolomite were contacted with a fixed volume and concentration of a heavy metal bearing solutions. Sorption data have been interpreted in terms of Langmuir and Freundlich equations. The effect of adsorption temperature on the heavy metals adsorption onto dolomite was investigated at three different temperatures (20, 40 and 60 deg. C). Thermodynamic parameters were calculated. The results obtained show that the Amberlite IR 120 strong cation-exchange resin and dolomite performed well for the removal of these heavy metals. As a low cost adsorbent, dolomite can preferable for removal of heavy metals from wastewaters.

  19. Multistage dolomitization in the Acungui Group metacarbonate rocks, Proterozoic of Parana state, Brazil; Dolomitizacao multifasica em reochas metacarbonaticas do Grupo Acungui, Proterozoico do estado do Parana, Brasil

    Energy Technology Data Exchange (ETDEWEB)

    Pinto-Coelho, Cristina Valle; Reis Neto, Jose Manoel dos [Universidade Federal do Parana (UFPR), Curitiba, PR (Brazil). Dept. de Geologia], e-mail: cristinavpc@ufpr.br, e-mail: jmreis@ufpr.br, e-mail: salla82@gmail.com; Eeva, Salla Talvikki [PETROBRAS (Brazil). E e P. Gerencia de Estratigrafia e Sedimentologia

    2007-11-15

    The carbonate rocks of Rio Bonito Quarry, at the state of Parana, are represented by metamarls, mylonized rocks, calcite and dolomite marbles and dolomite breccias, which were formed in several burial stages. The first dolomitization process which affected the marbles had its origin in a burial environment. The process occurred during Mesoproterozoic, where a precedent calcitic rock had its matrix replaced by fine to medium sized dolomite crystals with cloudy aspect, and where styolites and fractures formed the principal conduits for the circulation of Mg-rich solutions. The dolomite breccia were formed during the Brazilian Cycle (Neoproterozoic), in conditions of hydraulic fracturing, originated by devolatilization which occurred during the metamorphism of green schist facies. The second dolomitization process, caused the formation of Fe-rich microcrystalline dolomite (Dp1), originated through a fluid at chemical disequilibrium with the fluid responsible for the former dolomitization. In the Paleozoic occurred a new phase of dolomitization, developing the Dp2-type dolomite, as the consequence of reactivation of deep crustal faults or igneous intrusions (dykes of microgabbro). This dolomite is constituted by saddle dolomite, with nonplanar and coarse crystals, strong undulate extinction, which fills fractures in breccias as well as in dolomitic marbles. Superficial processes at the Paleogene, related to the topographic evolution, promoted the percolation of low-temperature fluids, occasioning the process of dedolomitization via dissolution and posterior filling of cavities. The process of dedolomitization occurred in dolomitic breccia with precipitation of late calcite, which filled the cavities, associated to dolomite of generation Dp2. Quartz completes the final phase of the void-filling process.(author)

  20. Origin of dolomitic rocks in the lower Permian Fengcheng formation, Junggar Basin, China: evidence from petrology and geochemistry

    Science.gov (United States)

    Zhu, Shifa; Qin, Yi; Liu, Xin; Wei, Chengjie; Zhu, Xiaomin; Zhang, Wei

    2016-09-01

    Although dolomitization of calcite minerals and carbonatization of volcanic rocks have been studied widely, the extensive dolomitic rocks that originated from altered volcanic and volcaniclastic rocks have not been reported. The dolomitic rocks of the Fengcheng Formation in the Junggar Basin of China appear to be formed under unusual geologic conditions. The petrological and geochemical characteristics indicate that the dolomitizing host rock is devitrified volcanic tuff. After low-temperature alteration and calcitization, these tuffaceous rocks are replaced by Mg-rich brine to form massive dolomitic tuffs. We propose that the briny (with -2 ‰ ~ 6 ‰ of δ13CPDB and -5 ‰ ~ 4 ‰ of δ18OPDB) and Mg-rich marine formation water (with 0.7060 ~ 0.7087 of 87Sr/86Sr ratio), the thick and intermediate-mafic volcanic ashes, and the tectonically compressional movement may have favored the formation of the unusual dolomitic rocks. We conclude that the proposed origin of the dolomitic rocks can be extrapolated to other similar terranes with volcaniclastic rocks, seabed tuffaceous sediment, and fracture filling of sill.

  1. Dolomitization in Late Jurassic-Early Cretaceous Platform Carbonates (Berdiga Formation), Ayralaksa Yayla (Trabzon), NE Turkey

    Science.gov (United States)

    Yıldız, Merve; Ziya Kırmacı, Mehmet; Kandemir, Raif

    2017-04-01

    ABSTRACT Pontides constitute an E-W trending orogenic mountain belt that extends about 1100 km along the northern side of Turkey from the immediate east of Istanbul to the Georgian border at the east. Tectono-stratigraphically, the Pontides are divided into three different parts: Eastern, Central, and Western Pontides. The Eastern Pontides, including the studied area, comprise an area of 500 km in length and 100 km in width, extending along the southeast coast of the Black Sea from the Kizilirmak and Yesilirmak Rivers in the vicinity of Samsun to the Little Caucasus. This area is bordered by the Eastern Black Sea basin to the north and the Ankara-Erzincan Neotethyan suture zone to the south. The Late Jurassic-Early Cretaceous platform carbonates are widely exposed in E-W direction in the Eastern Pontides (NE Turkey). The Platform carbonates shows varying lithofacies changing from supratidal to platform margin reef laterally and vertically, and was buried until the end of Late Cretaceous. The studied Ayralaksa Yayla (Trabzon, NE Turkey) area comprises one of the best typical exposures of formation in northern zone of Eastern Pontides. In this area, the lower parts of the formation are pervasively dolomitized by fabric-destructive and fabric-preserving replacement dolomite which are Ca-rich and nonstoichiometric (Ca56-66Mg34-44). Replacement dolomites (Rd) are represented by D18O values of -19.0 to -4.2 (VPDB), D13C values of 4.4 to 2.1 \\permil (VPDB) and 87Sr/86Sr ratios of 0.70889 to 0.70636. Petrographic and geochemical data indicate that Rd dolomites are formed prior to compaction at shallow-moderate burial depths from Late Jurassic-Early Cretaceous seawater and/or partly modified seawater as a result of water/rock interaction and they were recrystallized at elevated temperatures during subsequent burial. In the subsequent diagenetic process during the Late Cretaceous when the region became a magmatic arc, as a result of interaction with Early Jurassic volcanic

  2. Clumped isotope thermometry of calcite and dolomite in a contact metamorphic environment

    Science.gov (United States)

    Lloyd, Max K.; Eiler, John M.; Nabelek, Peter I.

    2017-01-01

    Clumped isotope compositions of slowly-cooled calcite and dolomite marbles record apparent equilibrium temperatures of roughly 150-200 °C and 300-350 °C, respectively. Because clumped isotope compositions are sensitive to the details of T-t path within these intervals, measurements of the Δ47 values of coexisting calcite and dolomite can place new constraints on thermal history of low-grade metamorphic rocks over a large portion of the upper crust (from ∼5 to ∼15 km depth). We studied the clumped isotope geochemistry of coexisting calcite and dolomite in marbles from the Notch Peak contact metamorphic aureole, Utah. Here, flat-lying limestones were intruded by a pluton, producing a regular, zoned metamorphic aureole. Calcite Δ47 temperatures are uniform, 156 ± 12 °C (2σ s.e.), across rocks varying from high-grade marbles that exceeded 500 °C to nominally unmetamorphosed limestones >5 km from the intrusion. This result appears to require that the temperature far from the pluton was close to this value; an ambient temperature just 20 °C lower would not have permitted substantial re-equilibration, and should have preserved depositional or early diagenetic Δ47 values several km from the pluton. Combining this result with depth constraints from overlying strata suggests the country rock here had an average regional geotherm of 22.3-27.4 °C/km from the late Jurassic Period until at least the middle Paleogene Period. Dolomite Δ47 in all samples above the talc + tremolite-in isograd record apparent equilibrium temperatures of 328-12+13 °C (1σ s.e.), consistent with the apparent equilibrium blocking temperature we expect for cooling from peak metamorphic conditions. At greater distances, dolomite Δ47 records temperatures of peak (anchi)metamorphism or pre-metamorphic diagenetic conditions. The interface between these domains is the location of the 330 °C isotherm associated with intrusion. Multiple-phase clumped isotope measurements are complemented by

  3. Reconstruction of the pre-compactional thickness of the Zechstein Main Dolomite in northwest Poland

    Directory of Open Access Journals (Sweden)

    Semyrka Grażyna

    2015-12-01

    Full Text Available Our reconstruction of the pre-compactional thickness of the Main Dolomite strata from the so-called Grotów Peninsula (northwest Poland was based on macroscopic observations of drill cores from three wells: Mokrzec-1, Sieraków-4 and Międzychód-5. These wells are located in various palaeogeographical zones of the Main Dolomite and cored rocks represent a range of microfacies. The amount of compactional reduction in thickness of the Main Dolomite was estimated by summing the total heights (Wst of all stylolites encountered in logs of these wells. For calculations, a generalised model of a drill core was developed, which embraced all types of stylolite seams present in the Main Dolomite succession studied. Also the method of stylolite dimensioning was demonstrated. The number of stylolites in the drill cores studied varied from 511 in the Sieraków-4 well to 1,534 in the Międzychód-5 well. In all cores studied low-amplitude macrostylolites predominated, but the reduction of thickness was controlled mostly by the low- and medium-amplitude macrostylolites. The largest number of stylolites was found in the grainstone/packstone microfacies. The turnout of stylolites depends of microfacies. The highest density of stylolites was documented in mudstones/wackestones (24 stylolites per metre of rock thickness and the lowest in boundstones (14 stylolites per metre of rock thickness. The low-amplitude stylolites appear most frequently in the mudstone/wackestone microfacies (15 stylolites per metre of rock thickness; in grainstones/packstones, rudstones/floatstones and boundstones middle-amplitude stylolites are rare (3 stylolites per metre of rock thickness. The degree of compaction of the Main Dolomite succession studied varied from 6 to 10%; hence, its calculated initial thickness also varied in the wells studied: from 41.3 m in the Sieraków-4 well to 56.9 m in the Mokrzec-1 well and to 97.1 m in the Międzychód-5 well. The volumes of reservoir

  4. Dolomitization of Carbonate Periplatform Deposit,Machari Formation (Middle to Late Cambrian),Korea

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    @@The petrography, the geochemistry and the burial history all constrain the origin and modification history of dolomites in an ancient periplatform carbonate slope deposit,the Machari Formation (late Miclclle to early Late Cambrian),Korea. The formation is mainly composed of rhythmic bedding. laminated to bedded lime mudstone alternating with argillaceous lime mudstone. The rhythmic bedding is a product of the deposition of offshore periplatform ooze and hemipelagic clay on a periplatform slope. This formation also shows minor and intermittent influx of other lithofacies including the bioclastic-peloidal packstone, peloidal wackestone, and intraclasts deposited as turbidites. Five types of dolomite occur in the Machari Formation, whose occurrence.texture and geochemistry provide an insight into origin and modification history.

  5. Early Carbonation Behavior of High-volume Dolomite Powder-cement Based Materials

    Institute of Scientific and Technical Information of China (English)

    YANG Huamei; HE zhen; SHAO Yixin

    2015-01-01

    Combined with DTG analysis, X-Ray diffraction analysis (XRD) andfi eld emission scanning electron microscopy analysis (FSEM) affi liated with energy dispersive spectrometer analysis (EDS), the early hydration and carbonation behavior of cement paste compacts incorporated with 30% of dolomite powder at low water to cement ratio (0.15) was investigated. The results showed that early carbonation curing was capable of developing rapid early strength. It is noted that the carbonation duration should be strictly controlled otherwise subsequent hydration might be hindered. Dolomite powder acted as nuclei of crystallization, resulting in acceleration of products formation and refi nement of products crystal size. Therefore, as for cement-based material, it was found that early carbonation could reduce cement dosages to a large extent and promote rapid strength gain resulting from rapid formation of products, supplemental enhancement due to water release in the reaction of carbonation, and formation of nanometer CaCO3 skeleton network at early age.

  6. Uranium immobilization by sulfate-reducing biofilms grown on hematite, dolomite, and calcite.

    Science.gov (United States)

    Marsili, Enrico; Beyenal, Haluk; Di Palma, Luca; Merli, Carlo; Dohnalkova, Alice; Amonette, James E; Lewandowski, Zbigniew

    2007-12-15

    Biofilms of sulfate-reducing bacteria Desulfovibrio desulfuricans G20 were used to reduce dissolved U(VI) and subsequently immobilize U(IV) in the presence of uranium-complexing carbonates. The biofilms were grown in three identically operated fixed bed reactors, filled with three types of minerals: one noncarbonate-bearing mineral (hematite) and two carbonate-bearing minerals (calcite and dolomite). The source of carbonates in the reactors filled with calcite and dolomite were the minerals, while in the reactor filled with hematite it was a 10 mM carbonate buffer, pH 7.2, which we added to the growth medium. Our five-month study demonstrated that the sulfate-reducing biofilms grown in all reactors were able to immobilize/reduce uranium efficiently, despite the presence of uranium-complexing carbonates.

  7. EPR, UV-Visible, and Near-Infrared Spectroscopic Characterization of Dolomite

    Directory of Open Access Journals (Sweden)

    S. Lakshmi Reddy

    2008-01-01

    Full Text Available Dolomite mineral samples having white and light green colors of Indian origin have been characterized by EPR, optical, and NIR spectroscopy. The optical spectrum exhibits a number of electronic bands due to presence of Fe(III ions in the mineral. From EPR studies, the parameters of g for Fe(III and g,A, and D for Mn(II are evaluated and the data confirm that the ions are in distorted octahedron. Optical absorption studies reveal that Fe(III is in distorted octahedron. The bands in NIR spectra are due to the overtones and combinations of water molecules. Thus EPR and optical absorption spectral studies have proven useful for the study of the solid state chemistry of dolomite.

  8. Promotion of Coconut Shell Gasification by Steam Reforming on Nickel-Dolomite

    Directory of Open Access Journals (Sweden)

    Pattaraporn Chaiprasert

    2009-01-01

    Full Text Available Biomass gasification by the use of metallic nickel as active metal on dolomite support has been chosen as catalyst because of its activity in biomass steam gasification and tar reduction. The purpose of this study is to study the effects of critical parameters on product gas compositions such as temperature, steam to carbon ratio (S/C and oxygen input. The results showed the increasing carbon conversion to gas from 44.13-78.43% whereas tar was decreased from 19.55-1.4% at temperature of 800°C and S/C 0.95. It is found that Nickel-dolomite is effective for tar reduction and for improving the quality of syngas derived from biomass which is a renewable energy source.

  9. Olivine, dolomite and ceramic filters in one vessel to produce clean gas from biomass.

    Science.gov (United States)

    Rapagnà, Sergio; Gallucci, Katia; Foscolo, Pier Ugo

    2017-07-27

    Heavy organic compounds produced during almond shells gasification in a steam and/or air atmosphere, usually called tar, are drastically reduced in the product gas by using simultaneously in one vessel a ceramic filter placed in the freeboard and a mixture of olivine and dolomite particles in the fluidized bed of the gasifier. The content of tar in the product gas during a reference gasification test with air, in presence of fresh olivine particles only, was 8600mg/Nm(3) of dry gas. By gasifying biomass with steam at the same temperature level of 820°C in a bed of olivine and dolomite (20% by weight), and in the presence of a catalytic ceramic filter inserted in the freeboard of the fluidized bed gasifier, the level of tar was brought down to 57mg/Nm(3) of dry producct gas, with a decrease of more than two orders of magnitude. Copyright © 2017. Published by Elsevier Ltd.

  10. Dissolution Kinetics of Magnesitic-Dolomite and Magnesite-Chrome Refractories in Secondary Steelmaking Slags

    Institute of Scientific and Technical Information of China (English)

    CHEN Zhaoyou; WU Xuezhen; YE Fangbao

    2007-01-01

    Dissolution kinetics of magnesitic-dolomite and magnesite-chrome refractories in secondary steelmaking slags was studied by means of the rotating cylinder method under forced convection. Materials investigated include four magnesitic-dolomite samples (MgO content 40% to 93% ) and two magnesite-chrome samples ( co-clinkered and semi-rebonded ). Synthetic slags simulative of VOD and AOD slags with varying basicity (0. 6-2. 68) are used. The experiments are carried out in Ar atmosphere at different temperatures (1 600 ℃-1 750 ℃ ) and revolumicrostructure of specimens (before and after slag tests)are studied by optical microscopy, SEM and EPMA.Based on our experimental results the mechanism and kinetics of the dissolution process are discussed.

  11. THE EFFECT OF FISSURES IN DOLOMITE ROCK MASS ON BLASTING PROJECTS

    Directory of Open Access Journals (Sweden)

    Branko Božić

    1989-12-01

    Full Text Available Rock fractures in the form of fissures are one of more important geological features of a tectonic system. They have an effect on mechanical behaviour of rook masses exposed to the actions of surface forces. For exploitation in dolomite quarries carried out by blasting of deep shot holes it is important to know the system of fissures within a rock mass for the rock brakes along already weakened planes (the paper is published in Croatian.

  12. Distribution of uranium and thorium in dolomitic gravel fill and shale saprolite.

    Science.gov (United States)

    Phillips, D H; Watson, D B

    2015-03-21

    The objectives of this study were to examine (1) the distribution of U and Th in dolomitic gravel fill and shale saprolite, and (2) the removal of uranium from acidic groundwater by dolomitic gravel through precipitation with amorphous basaluminite at the U.S. DOE Oak Ridge Integrated Field Research Challenge (ORIFRC) field site west of the Oak Ridge Y-12 National Security Complex in East Tennessee. Media reactivity and sustainability are a technical concern with the deployment of any subsurface reactive media. Because the gravel was placed in the subsurface and exposed to contaminated groundwater for over 20 years, it provided a unique opportunity to study the solid and water phase geochemical conditions within the media after this length of exposure. This study illustrates that dolomite gravel can remove U from acidic contaminated groundwater with high levels of Al(3+), Ca(2+), NO(3-), and SO4(2-) over the long term. As the groundwater flows through high pH carbonate gravel, U containing amorphous basaluminite precipitates as the pH increases. This is due to an increase in groundwater pH from 3.2 to ∼6.5 as it comes in contact with the gravel. Therefore, carbonate gravel could be considered as a possible treatment medium for removal and sequestration of U and other pH sensitive metals from acidic contaminated groundwater. Thorium concentrations are also high in the carbonate gravel. Thorium generally shows an inverse relationship with U from the surface down into the deeper saprolite. Barite precipitated in the shallow saprolite directly below the dolomitic gravel from barium present in the acidic contaminated groundwater.

  13. Strata-bound Dolomitization in the Eocene Laki Formation, Matyaro Jabal Area Lakhi Range, Sindh, Pakistan

    Directory of Open Access Journals (Sweden)

    Muhammad Waseem Khan

    2015-12-01

    Full Text Available The limestone of Eocene age Laki Formation of Matyaro Jabal area, Lakhi Range SindhPakistan has been studied to see different sedimentary features and diagenetic overprinting. The most diagnostic diagenetic feature of the Laki Formation is the formation of strata bound dolostone over extensive area. The dolostone beds which are separated by non-dolomitic limestone have developed at three different stratigraphic levels whose thickness vary from few centimeters to about 5 meters. Interbedded non dolomitic limestone is characterized by highly fossiliferous to less fossiliferous white chalky limestone with significant secondary porosity. The dolostone beds make lower erosional contact with chalky limestone while upper contact is sharp as well as transitional. The dolostone beds are very hard to soft with well developed dissolution cavities and karstification horizons. As a result of dolostone formation, the primary sedimentary features of rock fabrics and bioclasts are poorly preserved. However, few bioclastic grains show partial preservation with enhanced dissolution and biomoldic porosity. Dolomitization and different porosity types such as; intragranular, vuggy, molidic, intercrystalline, fracture and fenestral have made the limestone of Laki Formation as potential hydrocarbon reservoir rock. The mechanism of stratabound dolostone formation within Laki Formation is due to the mixing of seawater and fresh water with optimum Mg:Ca ratio. The Mg rich sea-water circulated through highly porous and permeable strata which was responsible for stratabound dolostone formation in the Laki Formation. The extrinsic factors such as sea level fluctuations and tectonics also played a vital role for dissolution along with porosity and permeability enhancement followed by dolomitization.

  14. Effect of fertilizer and dolomite applications on growth and yield of tapping rubber trees

    Directory of Open Access Journals (Sweden)

    Issariyaporn Damrongrak

    2015-12-01

    Full Text Available Tropical acid soil used for rubber planting has usually low fertility due to continuous loss of plant nutrient elements by crop removal and leaching. Thus, proper soil improvement in tapping rubber is very essential. This study aimed to measure the growth and yield of 17-year-old rubber trees, chemical properties of soil, and plant nutrient status in the leaf and latex after two years of soil improvement. A randomized complete block of seven treatments: No fertilizer (Control treatment, Chemical fertilizer based on soil analysis according to the recommendation of the Rubber Research Institute (Ch.F, Ch.F+ Dolomite to raise pH up to 6.0 (D, 3 kg per plant of compost (C, Ch.F+C, ½ Ch.F+C and ½ Ch.F+C+D, with three replicates was designed. After two years of giving treatments, it was found that adding full rate of chemical fertilizer based on soil test together with compost or dolomite increased the tree girth increment from the first year to the second year. Rubber yield after soil improvements tended to increase from the beginning to the end of the year, especially with compost application. Increasing of soil fertility was found after soil improvement treatments. However, total N, available P and available K were still lower than optimum levels as well as leaf N and K. Nitrogen in rubber latex after soil improvement treatments was higher than those in the control treatment, which contrasted to those of Ca and Mg. However, fertilizer and dolomite effect on micronutrient elements in rubber leaf and latex were not clear. Thus, fertilizer should be continuously applied at least with the full rate of chemical fertilizer based on soil analysis, and organic fertilizer should be applied to gain some trace elements. Dolomite could also be applied in a very strong acid soil.

  15. Heteroepitaxial growth of cadmium carbonate at dolomite and calcite surfaces: Mechanisms and rates

    Science.gov (United States)

    Callagon, Erika Blanca R.; Lee, Sang Soo; Eng, Peter J.; Laanait, Nouamane; Sturchio, Neil C.; Nagy, Kathryn L.; Fenter, Paul

    2017-05-01

    The systematic variation of rates and the mechanism of cadmium uptake on the (1 0 4) surface of dolomite (CaMg(CO3)2) were investigated using in situ and ex situ atomic force microscopy (AFM), ex situ specular X-ray reflectivity (XR), and ex situ X-ray fluorescence (XRF). Selected experiments were performed on the calcite (CaCO3) (1 0 4) surface for comparison. Aqueous solutions of CdCl2, CaCl2, and NaHCO3, undersaturated with respect to calcite and supersaturated with respect to otavite (CdCO3) and the (CdxCa1-x)CO3 solid solution, were reacted with dolomite surfaces for minutes to days. Calcite substrates were reacted with solutions containing 1-50 μM CdCl2, and with no added Ca or CO3. Thin carbonate films following the Stranski-Krastanov growth mode were observed on both substrates. Specular XR and XRF revealed the formation of nm-thick Cd-rich carbonate films that were structurally ordered with respect to the dolomite (1 0 4) plane. Epitaxial films adopted the calcite crystal structure with a d104-spacing (3.00 Å) larger than those of pure dolomite (2.88 Å) and otavite (2.95 Å) indicating either a solid solution with x ≈ 0.5, or a strained Cd-rich carbonate with a composition near that of otavite. The growth rate r of this phase increases with the initial supersaturation of the solution with respect to the solid solution, βmax , and follows the empirical relationship, as determined from XRF measurements, given by:

  16. Microcracking in calcite and dolomite marble: microstructural influences and effects on properties

    OpenAIRE

    Shushakova, Victoria; Fuller, Edwin; Siegesmund, Siegfried

    2012-01-01

    Microstructure‐based finite-element analysis with a microcracking algorithm was used to simulate an actual degradation phenomenon of marble structures, i.e., microcracking. Both microcrack initiation and crack propagation were characterized, as were their dependence on lattice preferred orientation (LPO), grain shape preferred orientation (SPO), grain size, marble composition (calcite and dolomite) and grain‐boundary fracture toughness. Two LPOs were analyzed: a random orientation distributio...

  17. Criteria for selection of dolomites and catalysts for tar elimination from biomass gasification gas. Kinetic constants

    Energy Technology Data Exchange (ETDEWEB)

    Corella, J.; Narvaez, I.; Orio, A. [Madrid Univ. (Spain). Dept. of Chem. Eng.

    1996-12-31

    Calcined dolomites and commercial steam reforming catalysts are used downstream biomass gasifiers for hot catalytic raw gas cleaning. To further compare these solids under a rigorous basis, a reaction network and a kinetic model are presented. The apparent kinetic constant for the tar reduction is here proposed as a basis of comparison. Tar sampling and analysis, and the units used for the space-time in the catalytic reactor affect the kinetic constants observed. (author) (2 refs.)

  18. Analysis of limestones and dolomites by x-ray fluorescence spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Wheeler, B.D.

    1999-07-01

    Sources of calcium are generally widespread and quite extensive. These sources are limestone, dolomite, marl, chalk, and oyster shell. Cement plants account for nearly half of the demand, while two hundred lime plants in the US and Puerto Rico consume about twenty five percent. Since the chemical composition of the limestone and other sources of calcium is critical in the cement and lime industry, particularly for the deleterious compounds such as sodium oxide, Na{sub 2}O, magnesium oxide, MgO, phosphorus pentoxide, P{sub 2}O{sub 5}, and potassium oxide, K{sub 2}O, accurate determinations are critical. Due to the tonnage per hour, these determinations must be made rapidly and accurately. X-ray fluorescence can thereby satisfy this need for accuracy and also precision. Production of lime is performed by calcining limestone or dolomite in which the industry is generally located and concentrated in the States of Michigan and Pennsylvania. The resulting product is quicklime, CaO, and hydrated lime, Ca(OH){sub 2}. Substantial amounts of quicklime is further processed into calcium carbide in order to produce acetylene gas. In this case, the determination of P{sub 2}O{sub 5} is critical since minor quantities of phosphorus in acetylene gas can cause premature explosions. Other uses for lime are well known in the treatment of water, the paper and pulp industry, and in the steel industry for the production of slag to remove impurities. Dolomitic lime is heavily utilized in the manufacture of magnesite refractories by reacting dolomitic lime with brines from the Michigan Basin to produce magnesium oxide, MgO, and calcium chloride, CaCl{sub 2}. Sample preparation for these materials usually is performed by grinding and pelletizing or fusion with lithium-tetra-borate, Li{sub 2}B{sub 4}O{sub 7}.

  19. Research on the wastewater treatment efficiency in the vertical flow constructed wetland with the dolomite used as the filter media

    OpenAIRE

    Kazakevičienė, Jurgita

    2013-01-01

    Aim of the research The aim of this research was to evaluate the efficiency of the constructed wetlands of vertical filtration with various fractions of dolomite used as the filter media to remove pollutants from the wastewater under the laboratory and industrial conditions and using experimental methods and after the research to prepare the calculation methodology for the filters with dolomite chippings used as the filter media. Objectives of the research In order to ...

  20. Highly efficient CO2 sorbents: development of synthetic, calcium-rich dolomites.

    Science.gov (United States)

    Filitz, Rainer; Kierzkowska, Agnieszka M; Broda, Marcin; Müller, Christoph R

    2012-01-03

    The reaction of CaO with CO(2) is a promising approach for separating CO(2) from hot flue gases. The main issue associated with the use of naturally occurring CaCO(3), that is, limestone, is the rapid decay of its CO(2) capture capacity over repeated cycles of carbonation and calcination. Interestingly, dolomite, a naturally occurring equimolar mixture of CaCO(3) and MgCO(3), possesses a CO(2) uptake that remains almost constant with cycle number. However, owing to the large quantity of MgCO(3) in dolomite, the total CO(2) uptake is comparatively small. Here, we report the development of a synthetic Ca-rich dolomite using a coprecipitation technique, which shows both a very high and a stable CO(2) uptake over repeated cycles of calcination and carbonation. To obtain such an excellent CO(2) uptake characteristic it was found to be crucial to mix the Ca(2+) and Mg(2+) on a molecular level, that is, within the crystalline lattice. For sorbents which were composed of mixtures of microscopic crystals of CaCO(3) and MgCO(3), a decay behavior similar to natural limestone was observed. After 15 cycles, the CO(2) uptake of the best sorbent was 0.51 g CO(2)/g sorbent exceeding the CO(2) uptake of limestone by almost 100%.

  1. Magnesium Production by Silicothermic Reduction of Dolime in Pre-prepared Dolomite Pellets

    Science.gov (United States)

    Fu, Da-Xue; Zhang, Ting-An; Guan, Lu-Kui; Dou, Zhi-He; Wen, Ming

    2016-12-01

    A novel process has been proposed for magnesium production, in which powder materials including dolomite, ferrosilicon, fluorite and binder are mixed to produce pellets. Kinetics of the silicothermic reduction using the pre-prepared dolomite pellets was investigated by a non-isothermal, flowing argon-protected gravimetric technique at a temperature range from 1323 K to 1673 K. The results suggest that the process is controlled by a chemical reaction, with the second-order chemical reaction model providing the best representation of the process. The apparent activation energy was determined to be 280 kJ/mol. Calcium silicide (was found in the pellet after calcinations. The silicothermic process in the pre-prepared dolomite pellets is possibly a solid-liquid reaction since calcium silicide transformed into liquid alloy, which reduced diffusion resistance of silicon during the reduction process. The gas-film mass transfer may have some effect on the reduction kinetics but is not the major rate-limiting step.

  2. Dissolution kinetics and mechanisms at dolomite-water interfaces: effects of electrolyte specific ionic strength.

    Science.gov (United States)

    Xu, Man; Sullivan, Katie; Vanness, Garrett; Knauss, Kevin G; Higgins, Steven R

    2013-01-02

    Elucidating dissolution kinetics and mechanisms at carbonate mineral-water interfaces is essential to many environmental and geochemical processes, including geologic CO(2) sequestration in deep aquifers. In the present work, effects of background electrolytes on dolomite (CaMg(CO(3))(2)) reactivity were investigated by measuring step dissolution rates using in situ hydrothermal atomic force microscopy (HAFM) at 90 °C. Cleaved surfaces of dolomite were exposed to sodium chloride and tetramethylammonium chloride (TMACl) aqueous solutions with ionic strengths (I) ranging from 0 to 0.77 m at pH 4 and pH 9. HAFM results demonstrated that dolomite step retreat rates increased with increasing solution ionic strength and decreasing pH. Comparison of [481] and [441] steps revealed that the anisotropy of [481] and [441] step speeds became significant as solution ionic strength increased, with NaCl exerting more pronounced effects than TMACl for the same I. To interpret the different trends observed for NaCl and TMACl, a dissolution mechanism involving orientation-dependent ion adsorption and consequent edge free energy changes is proposed.

  3. Intermediate-scale tests of sodium interactions with calcite and dolomite aggregate concretes. [LMFBR

    Energy Technology Data Exchange (ETDEWEB)

    Randich, E.; Acton, R.U.

    1983-09-01

    Two intermediate-scale tests were performed to compare the behavior of calcite and dolomite aggregate concretes when attacked by molten sodium. The tests were performed as part of an interlaboratory comparison between Sandia National Laboratories and Hanford Engineering Development Laboratories. Results of the tests at Sandia National Laboratories are reported here. The results show that both concretes exhibit similar exothermic reactions with molten sodium. The large difference in reaction vigor suggested by thermodynamic considerations of CO/sub 2/ release from calcite and dolomite was not realized. Penetration rates of 1.4 to 1.7 mm/min were observed for short periods of time with reaction zone temperatures in excess of 800/sup 0/C during the energetic attack. The penetration was not uniform over the entire sodium-concrete contact area. Rapid attack may be localized due to inhomogeneities in the concrete. The chemical reaction zone is less then one cm thick for the calcite concrete but is about seven cm thick for the dolomite concrete.

  4. Z-contrast imaging and ab initio study on "d" superstructure in sedimentary dolomite

    CERN Document Server

    Shen, Zhizhang; Szlufarska, Izabela; Brown, Philip E; Xu, Huifang

    2016-01-01

    Nano-precipitates with tripled periodicity along the c-axis are observed in a Ca-rich dolomite sample from Proterozoic carbonate rocks with "molar tooth" structure. This observation is consistent with previous description of d reflections. High-angle annular dark-field STEM imaging (or Z-contrast imaging) that avoids dynamic diffraction as seen in electron diffraction and high-resolution TEM imaging modes, confirms that d reflections correspond to nanoscale precipitates aligned parallel to (001) of the host dolomite. The lamellae precipitates have a cation ordering sequence of Ca-Ca-Mg-Ca-Ca- Mg along the c direction resulting in a chemical composition of Ca0.67Mg0.33CO3. This superstructure is attributed to the extra or d reflections, thus is referred to as the d superstructure in this study. The structure can be simply described as interstratified calcite/dolomite. The crystal structure of the d superstructure calculated from density functional theory (DFT) has a space group of P31c and has a and c unit-cel...

  5. Experimental observation of permeability changes in dolomite at CO2 sequestration conditions.

    Science.gov (United States)

    Tutolo, Benjamin M; Luhmann, Andrew J; Kong, Xiang-Zhao; Saar, Martin O; Seyfried, William E

    2014-02-18

    Injection of cool CO2 into geothermally warm carbonate reservoirs for storage or geothermal energy production may lower near-well temperature and lead to mass transfer along flow paths leading away from the well. To investigate this process, a dolomite core was subjected to a 650 h, high pressure, CO2 saturated, flow-through experiment. Permeability increased from 10(-15.9) to 10(-15.2) m(2) over the initial 216 h at 21 °C, decreased to 10(-16.2) m(2) over 289 h at 50 °C, largely due to thermally driven CO2 exsolution, and reached a final value of 10(-16.4) m(2) after 145 h at 100 °C due to continued exsolution and the onset of dolomite precipitation. Theoretical calculations show that CO2 exsolution results in a maximum pore space CO2 saturation of 0.5, and steady state relative permeabilities of CO2 and water on the order of 0.0065 and 0.1, respectively. Post-experiment imagery reveals matrix dissolution at low temperatures, and subsequent filling-in of flow passages at elevated temperature. Geochemical calculations indicate that reservoir fluids subjected to a thermal gradient may exsolve and precipitate up to 200 cm(3) CO2 and 1.5 cm(3) dolomite per kg of water, respectively, resulting in substantial porosity and permeability redistribution.

  6. Removal of Phosphate from Synthetic Aqueous Solution by Adsorption with Dolomite from Padalarang

    Directory of Open Access Journals (Sweden)

    Fadjari Lucia Nugroho

    2014-12-01

    Full Text Available The presence of phosphate in wastewaters can cause eutrophication of surface water bodies leading to algal-blooming in the aquatic environment and degradation of water quality. Phosphate removal from wastewaters by conventional biological treatment removes only 10-30% of the phosphate, whilst chemical treatment using precipitants such as calcium or iron salts, although effective, is expensive and produces water-rich sludge which must be further treated. Hence, phosphate removal by adsorption in the form of Ca -phosphate has been proposed as an alternative to the more traditional methods. This study investigated the feasibility of using dolomite–a common sedimentary rock–from Padalarang, West Java, Indonesia as the adsorbent for the removal of phosphate from synthetic aqueous solution. Chemical analysis revealed that the Padalarang dolomite contains 33.6-36.2% CaO. Batch experiments at room temperature indicated that optimum removal of phosphate was achieved at pH 9. At 25°C , where increasing concentrations of phosphate (10–100 mg/L increased phosphate adsorption (2.15-31.3 mg/g by the dolomite. The adsorption of phosphate could be described by the Langmuir isotherm model, with constants Qm= 476.19 mg/g, K L= 0,00106 L/mg and equilibrium parameter (R L: 0.904 – 0.989. Phosphate adsorption by dolomite not only permits its removal but also its potential recovery for reuse.

  7. Drilling the Messinian Salinity Crisis as a Model Analogue for Dolomite Deposition at the End of Massive Salt Deposition Events

    Science.gov (United States)

    McKenzie, Judith A.; Aloisi, Giovanni; Anjos, Sylvia; Latgé, Ricardo; Matsuda, Nilo; Bontognali, Tomaso; Vasconcelos, Crisogono

    2015-04-01

    Sedimentologic and stratigraphic studies of the Lower Cretaceous sequence, deposited in the economically important Campos Basin, southeast Brazil, document the occurrence of ~20-m-thick dolomite intervals overlying the "massive salt" megasequences of the Lagoa Feia Formation. This stratigaphic succession marks the Aptian/Albian transition from extreme evaporitic conditions of the Lagoa Feia Formation to shallow marine conditions of the Macaé Formation, related to the early opening of the South Atlantic. The facies change from evaporites to dolomite is interpreted as a product of dolomitization resulting from the refuxing of hypersaline fluids from shallow embayments with intense evaporation (Latgé, 2001). Although the reflux model provides a mechanism to produce fluids with geochemical composition favorable for dolomite precipitation, it cannot account for all of the factors required to promote dolomite precipitation. In this study, we propose a different model to explain the post-evaporite deposition of massive dolomite based on the study of sequences deposited at the end Messinian Salinity Crisis, which were recovered from the deep basins of the Mediterranean Sea during DSDP/ODP drilling campaigns. At most of these deep-water sites, the cored interval contained unusual dolomite deposits overlying the uppermost evaporite sections. For example, the upper Messinian sedimentary sequence at DSDP Site 374 comprises non-fossiliferous dolomitic mudstone overlying dolomitic mudstone/gypsum cycles, which in turn overlie anhydrite and halite (Hsü, Montadert et al., 1978). We postulate that the end Messinian dolomite is a product of microbial activity under extreme hypersaline conditions. In the last 20 years, research into the factors controlling dolomite precipitation under Earth surface conditions has led to the development of new models involving the metabolism of microorganisms and associated biofilms to overcome the kinetic inhibitions associated with primary

  8. Stable isotope record of coexisting apatite and dolomite in Early Cambrian phosphorites, Meishucun section, South China

    Science.gov (United States)

    Wegwerth, Antje; Struck, Ulrich; Segl, Monika; Vennemann, Torsten W.; Gehlken, Peer-L.; Heubeck, Christoph; Böttcher, Michael E.

    2010-05-01

    The Precambrian-Cambrian transition forms one of the most dramatic time periods in Earth's history, as global changes in tectonics, climate and chemistry in the atmosphere and oceans favoured the worldwide Cambrian Radiation and a concomitant ecosphere revolution. This time interval is paralleled by the first appearance of the widespread giant phosphorites. The well-known Meishucun section (South China), a former candidate section for the Pc-C boundary, documents phosphorite genesis amongst a rapid biodiversification, immediately following the end of the Precambrian in a low-latitude, shallow-water carbonate shelf. This contribution aims to elucidate the relation between simultaneous phosphorite deposition and global environmental conditions at the Pc-C boundary by using stable carbon and oxygen isotope analyses. Accurate determinations of d13C and d18O values may allow conclusions about ancient ocean circulation, paleo-productivity, paleo-temperatures, and most prominently diagenetic processes. The investigated samples from the Meishucun section basically consist of apatite, dolomite, and quartz that may be further devided into a lower and upper phosphorite as well as an overlying dolostone intervall. Additionally, calcite and siderite occur as minor compounds in some samples. Bulk d13C values of the carbonate fraction correlate with dolomite abundance throughout the section ranging from -4 to 1 per mil. Furthermore, several horizons suggest a relation between d13C values and apatite content, implying lower d13C values in apatites compared to coexisting dolomite. A slight negative d13C excursion at the top of the lower phosphorite coincides with the first appearance of small shelly fossils. Corresponding bulk d18O values generally show a stratigraphic-upward trend towards lower values throughout the record with slightly higher values in dolomite-rich sections. This may either indicate a warming trend during deposition, an isotopic shift in sea water composition

  9. Patrones espaciales de la riqueza específica de las culebras Thamnophis en México Spatial patterns of species richness of garter snakes Thamnophis in Mexico

    Directory of Open Access Journals (Sweden)

    Crystian Sadiel Venegas-Barrera

    2011-03-01

    Full Text Available Se identificaron tanto las áreas de mayor riqueza específica de las culebras del género Thamnophis y su presencia en las provincias biogeográficas y las Regiones Terrestres Prioritarias (RTP, como los factores antropogénicos que pueden influir en su distribución. Con la combinación de mapas de distribución potencial de las especies se creó un mapa de riqueza específica para calcular el porcentaje de celdas ocupadas por el género dentro de cada provincia biogeográfica, de cada RTP y conocer el tipo de uso de suelo. Además, se obtuvo la complementariedad de especies y la ordenación de las RTP a partir de su composición específica. El género se distribuyó en el 80.5% de México, en todas sus provincias biogeográficas. Los estados de Durango, Michoacán, Puebla, Veracruz y Oaxaca presentaron la mayor riqueza específica. Potencialmente, el género puede encontrarse en el 96% de las RTP de México con un patrón altitudinal y climático. De 6 grupos de las RTP, el grupo oriental presentó la mayor riqueza específica. El 25.8% de la distribución potencial del género se encontró en áreas modificadas por el hombre. Se discuten los patrones de distribución bajo una perspectiva ecológica, biogeográfica y de conservación y se sugiere comprobar la riqueza específica potencial con estudios de campo.We identified areas of high species richness of snakes of the genus Thamnophis, their presence within biogeographic provinces and Terrestrial Priority Regions (TPR. We also identified anthropogenic factors that may influence their distribution. We created a map of species richness from the combination of potential distribution maps of species to calculate the percentage of cells occupied by the genus within each biogeographic province, TPR and type of land use. In addition, we obtained the complementarity of species and the ordination of TPR from its species composition. The genus is distributed in 80.5% of Mexico, in all biogeographic

  10. Primary Evaporites for the Messinian Salinity Crisis: the shallow gypsum vs. deep dolomite formation paradox solved

    Science.gov (United States)

    De Lange, Gert J.; Krijgsman, Wout

    2014-05-01

    The Messinian Salinity Crisis (MSC) is a dramatic event that took place ~ 5.9 Ma ago, and resulted in the deposition of 0.3-3 km thick evaporites at the Mediterranean seafloor. A considerable and long-lasting controversy existed on the modes of their formation. During the CIESM Almeria Workshop a consensus was reached on several aspects. In addition, remaining issues to be solved were identified, such as for the observed shallow gypsum versus deep dolostone deposits for the early phase of MSC. The onset of MSC is marked by deposition of gypsum/sapropel-like alternations, thought to relate to arid/humid climate conditions. Gypsum precipitation only occurred at marginal settings, while dolomite containing rocks have been reported from deeper settings. A range of potential explanations have been reported, most of which cannot satisfactorily explain all observations. Biogeochemical processes during MSC are poorly understood and commonly neglected. These may, however, explain that different deposits formed in shallow versus deep environments without needing exceptional physical boundary conditions for each. We present here a unifying mechanism in which gypsum formation occurs at all shallow water depths but its preservation is mostly limited to shallow sedimentary settings. In contrast, ongoing anoxic organic matter (OM) degradation processes in the deep basin result in the formation of dolomite. Gypsum precipitation in evaporating seawater takes place at 3-7 times concentrated seawater; seawater is always largely oversaturated relative to dolomite but its formation is thought to be inhibited by the presence of dissolved sulphate. Thus the conditions for formation of gypsum exclude those for the formation of dolomite and vice versa. Another process that links the saturation states of gypsum and dolomite is that of OM degradation by sulphate reduction. In stagnant deep water, oxygen is rapidly depleted through OM degradation, then sulphate becomes the main oxidant for OM

  11. A multi-scale assessment of Pb(II) sorption on dolomite.

    Science.gov (United States)

    Lee, Shinwoo; Dyer, James A; Sparks, Donald L; Scrivner, Noel C; Elzinga, Evert J

    2006-06-01

    Macroscopic sorption studies indicated that Pb sorption capacity was independent of pH over the pH range 5-7, while sorption as a function of reaction time up to two weeks for systems with no bulk precipitate phases showed continuous Pb uptake on dolomite. This could be due to diffusion of Pb into the micropores of dolomite as well as an increase in surface sites caused by particle size reduction during suspension mixing. Normalized XANES spectra for systems undersaturated with respect to Pb carbonate precipitates resembled the spectrum of Pb4(OH)4(4+), suggesting that Pb is mainly coordinated to dolomite as an inner-sphere surface complex. On the other hand, the XANES spectrum for 10(-3) M Pb at 1 atm CO2(g) in a 2 M Mg(NO3)2 background electrolyte solution resembled that of cerussite, while a sample at 5 x 10(-4) M Pb in equilibrium with air and 2 M Mg(NO3)2 resembled that of hydrocerussite. EXAFS analyses of sorption samples in chloride solutions showed that there were only first-shell contributions under 1 atm CO2(g), while higher shell contributions from Ca/Mg were seen at 10(-3.42) atm CO2(g). On the other hand, EXAFS samples prepared in nitrate solutions showed noticeable differences in speciation under different reaction conditions-from outer-sphere surface complexes at low Pb concentrations and pH, to inner-sphere surface complexes at moderate Pb concentrations and neutral pH, to the formation of Pb carbonate precipitates at the highest Pb loadings.

  12. Pore Structure Characterization of Indiana Limestone and Pink Dolomite from Pore Network Reconstructions

    Directory of Open Access Journals (Sweden)

    Freire-Gormaly Marina

    2016-05-01

    Full Text Available Carbon sequestration in deep underground saline aquifers holds significant promise for reducing atmospheric carbon dioxide emissions (CO2. However, challenges remain in predicting the long term migration of injected CO2. Addressing these challenges requires an understanding of pore-scale transport of CO2 within existing brine-filled geological reservoirs. Studies on the transport of fluids through geological porous media have predominantly focused on oil-bearing formations such as sandstone. However, few studies have considered pore-scale transport within limestone and other carbonate formations, which are found in potential storage sites. In this work, high-resolution micro-Computed Tomography (microCT was used to obtain pore-scale structural information of two model carbonates: Indiana Limestone and Pink Dolomite. A modified watershed algorithm was applied to extract pore network from the reconstructed microCT volumetric images of rock samples and compile a list of pore-scale characteristics from the extracted networks. These include statistical distributions of pore size and radius, pore-pore separation, throat radius, and network coordination. Finally, invasion percolation algorithms were applied to determine saturation-pressure curves for the rock samples. The statistical distributions were comparable to literature values for the Indiana Limestone. This served as validation for the network extraction approach for Pink Dolomite, which has not been considered previously. Based on the connectivity and the pore-pore separation, formations such as Pink Dolomite may present suitable storage sites for carbon storage. The pore structural distributions and saturation curves obtained in this study can be used to inform core- and reservoir-scale modeling and experimental studies of sequestration feasibility.

  13. Epigenetic dolomitization of the Přaídolí formation (Upper Silurian), the Barrandian basin, Czech Republic: implications for burial history of Lower Paleozoic strata

    Science.gov (United States)

    Suchý, V.; Rozkošný, I.; Žák, K.; Franců, J.

    1996-06-01

    Stratabound epigenetic dolomite occurs in carbonate facies of the Barrandian basin (Silurian and Devonian), Czech Republic. The most intense dolomitization is developed in bioclastic calcarenites within the transition between micritic limestone and shaledominated Přídolí and Lochkov formations deposited on a carbonate slope. Medium-crystalline (100-400 µm), inclusion-rich, xenotopic matrix dolomite ( δ 18O=-4.64 to -3.40‰ PDB; δ 13C=+1.05 to +1.85‰ PDB) which selectively replaced most of the bioclastic precursor is volumetrically the most important dolomite type. Coarse crystalline saddle dolomite ( δ 18O=-8.04 to -5.14‰ PDB; δ 18C=+0.49 to +1.49 PDB) which precipitated in fractures and vugs within the matrix dolomite represents a later diagenetic dolomitization event. In some vugs, saddle dolomite coprecipitated with petroleum inclusion-rich authigenic quartz crystals and minor sulfides which, in turn, were post-dated by semisolid asphaltic bitumen. The interpretation of the dolomitization remains equivocal. Massive xenotopic dolomite, although generally characteristic of a deeper burial setting, may have been formed by a recrystallization of an earlier, possibly shallow burial dolomite. Deeper burial recrystallization by reactive basinal pore fluids that presumably migrated through the more permeable upper portion of the Přídolí sequence appears as a viable explanation for this dolomitization overprint. Saddle dolomite cement of the matrix dolomite is interpreted as the last dolomitization event that occurred during deep burial at the depth of the oil window zone. The presence of saddle dolomite, the fluid inclusion composition of associated quartz crystals, and vitrinite paleogeothermometry of adjacent sediments imply diagenetic burial temperatures as high as 160°C. Although high geothermal gradients in the past or the involvement of hydrothermally influenced basinal fluids can account for these elevated temperatures, burial heating beneath

  14. Epigenetic dolomitization of the Přídolí formation (Upper Silurian), the Barrandian basin, Czech Republic: implications for burial history of Lower Paleozoic strata

    Science.gov (United States)

    Suchý, V.; Rozkošný, I.; Žák, K.; Franců, J.

    Stratabound epigenetic dolomite occurs in carbonate facies of the Barrandian basin (Silurian and Devonian), Czech Republic. The most intense dolomitization is developed in bioclastic calcarenites within the transition between micritic limestone and shale-dominated Přídolí and Lochkov formations deposited on a carbonate slope. Medium-crystalline (100-400μm), inclusion-rich, xenotopic matrix dolomite (δ18O=-4.64 to -3.40ö PDBδ13C=+1.05 to +1.85ö PDB) which selectively replaced most of the bioclastic precursor is volumetrically the most important dolomite type. Coarse crystalline saddle dolomite (δ18O=-8.04 to -5.14ö PDBδ18C=+0.49 to +1.49 PDB) which precipitated in fractures and vugs within the matrix dolomite represents a later diagenetic dolomitization event. In some vugs, saddle dolomite coprecipitated with petroleum inclusion-rich authigenic quartz crystals and minor sulfides which, in turn, were postdated by semisolid asphaltic bitumen. The interpretation of the dolomitization remains equivocal. Massive xenotopic dolomite, although generally characteristic of a deeper burial setting, may have been formed by a recrystallization of an earlier, possibly shallow burial dolomite. Deeper burial recrystallization by reactive basinal pore fluids that presumably migrated through the more permeable upper portion of the Přídolí sequence appears as a viable explanation for this dolomitization overprint. Saddle dolomite cement of the matrix dolomite is interpreted as the last dolomitization event that occurred during deep burial at the depth of the oil window zone. The presence of saddle dolomite, the fluid inclusion composition of associated quartz crystals, and vitrinite paleogeothermometry of adjacent sediments imply diagenetic burial temperatures as high as 160 °C. Although high geothermal gradients in the past or the involvement of hydrothermally influenced basinal fluids can account for these elevated temperatures, burial heating beneath approximately 3

  15. Basic Data Report for Drillholes on the H-19 Hydropad (Waste Isolation Pilot Plant--WIPP)

    Energy Technology Data Exchange (ETDEWEB)

    Mercer, J.W.; Cole, D.L.; Holt, R.M.

    1998-10-09

    Seven holes were drilled and wells (H-19b0, H-19b2, H-19b3, H-19b4, H-19b5, H-19b6, and H-19b7) were constructed on the H-19 hydropad to conduct field activities in support of the Culebra Transport Program. These wells were drilled and completed on the Waste Isolation Pilot Plant (WIPP) site during February to September 1995. An eighth hole, H-19b1, was drilled but had to be abandoned before the target depth was reached because of adverse hole conditions. The geologic units penetrated at the H-19 location include surficial deposits of Holocene age, rocks from the Dockum Group of Upper Triassic age, the Dewey Lake Redbeds, and Rustler Formation of the Permian age. The Rustler Formation has been further divided into five informal members which include the Forty-niner Member, Magenta Member, Tamarisk Member, Culebra Dolomite Member, and an unnamed lower member. The Rustler Formation, particularly the Culebra Dolomite Member, is considered critical for hydrologic site characterization. The Culebra is the most transmissive saturated unit above the WIPP repository and, as such, is considered to be the most likely pathway for radionuclide transport to the accessible environment in the unlikely event the repository is breached. Seven cores from the Culebra were recovered during drilling activities at the H-19 hydropad and detailed descriptions of these cores were made. On the basis of geologic descriptions, four hydrostratigraphic units were identified in the Culebra cores and were correlated with the mapping units from the WFP air intake shaft. The entire length of H-19b1 was cored and was described in detail. During coring of H-19b1, moisture was encountered in the upper part of the Dewey Lake Redbeds. A 41-ft-thick section of this core was selected for detailed description to qualify the geologic conditions related to perched water in the upper Dewey Lake. In addition to cuttings and core, a suite of geophysical logs run on the drillholes was used to identify and

  16. EPR, UV-Visible, and Near-Infrared Spectroscopic Characterization of Dolomite

    OpenAIRE

    S. Lakshmi Reddy; Frost, R. L.; G. Sowjanya; Reddy, N. C. G.; G. Siva Reddy; Reddy, B. J.

    2008-01-01

    Dolomite mineral samples having white and light green colors of Indian origin have been characterized by EPR, optical, and NIR spectroscopy. The optical spectrum exhibits a number of electronic bands due to presence of Fe(III) ions in the mineral. From EPR studies, the parameters of g for Fe(III) and g,A, and D for Mn(II) are evaluated and the data confirm that the ions are in distorted octahedron. Optical absorption studies reveal that Fe(III) is in distorted octahedron. The bands in NIR spe...

  17. Interferometric study of the dolomite dissolution: a new conceptual model for mineral dissolution

    Science.gov (United States)

    Lttge, A.; Winkler, U.; Lasaga, A. C.

    2003-03-01

    The dissolution rate and mechanism of three different cleavage faces of a dolomite crystal from Navarra (near Pamplona), Spain, were studied in detail by vertical scanning interferometry techniques. A total of 37 different regions (each about 124 × 156 μm in size) on the three sample surfaces were monitored as a function of time during dissolution at 25°C and pH 3. Dissolution produced shallow etch pits with widths reaching 20 μm during 8 h of dissolution. Depth development as a function of time was remarkably similar for all etch pits on a given dolomite surface. On the basis of etch pit distribution and volume as a function of time, the calculated dissolution rate increases from near zero to 4 × 10 -11 mol cm -2 s -1 over 5 h. The time variation is different for each of the three cleavage surfaces studied. In addition, the absolute dissolution rates of different parts of the dolomite crystal surface can be computed by using a reference surface. The different surfaces yield an "average" rate of 1.08 × 10 -11 mol cm -2 s -1 with a standard deviation of 0.3 × 10 -11 mol cm -2 s -1 based on about 60 analyses. The mean absolute rate of the dolomite surface is about 10 times slower than the rate calculated from etch pit dissolution alone. On the other hand, earlier batch rate data that used BET surface areas yield rates that are at least 30 to 60 times faster than our directly measured mean dissolution rate for the same pH and temperature. A conceptual model for mineral dissolution has been inferred from the surface topography obtained by the interferometry investigations. In this model, mineral dissolution is not dominated by etch pit formation itself but rather by extensive dissolution stepwaves that originate at the outskirts of the etch pits. These stepwaves control the overall dissolution as well as the dependence on temperature and saturation state.

  18. Equation of state of dolomite from shock Hugoniot and static compression studies

    Science.gov (United States)

    Grady, D. E.

    2017-01-01

    Comparisons are made between shock Hugoniot data and recent high-pressure static DAC (diamond anvil cell) data on dolomite mineral. Stark disparities are noted. DAC measurements reveal first order phase transformation within the pressure range of approximately 17-37 GPa. The preponderance of shock data failed to reveal phase transformation on the Hugoniot. Early time-resolved pressure reveal a possible transformation in the neighborhood of 20-25 GPa impeded by transformation kinetics. Static and dynamic data are contrasted and the underlying mechanisms assessed.

  19. Mass balance and fluid flow constraints on regional-scale dolomitization, Late Devonian, Western Canada Sedimentary Basin

    Energy Technology Data Exchange (ETDEWEB)

    Machel, H.G. [Alberta Univ., Edmonton, AB (Canada); Mountjoy, E.M. [McGill Univ., Montreal, PQ (Canada). Dept. of Earth and Planetary Sciences; Amthor, J.E. [Shell Internationale Research Maatschappij NV, The Hague (Netherlands)

    1996-09-01

    Flow mechanisms that resulted in regionally pervasive, replacive dolomitization of the Upper Devonian carbonates in the Western Canada Sedimentary Basin (WCSB), were discussed. In critiquing the hydrogeological model proposed by Shields and Brady (1995), these interveners noted three major problems: (1) brine recharge area not isotropic or homogeneous, (2) hydrogeologic model does not match the conceptual geological model, (3) the aspect ratio of the hydrogeologic model is inconsistent with other explanations of brine reflux flushing. While these authors agree that seepage reflux of evaporite brines account for some of the dolomites in the basin, they believe that available geological, petrographic, paragenetic, and geochemical evidence invalidate regional brine reflux as the mechanism of basin-wide pervasive dolomitization, as proposed by Shields and Brady. (A response to this critique from Shields and Brady is presented on pages 572-573 of this issue of the Bulletin). 27 refs., 1 fig.

  20. Thermal and catalytic cracking of ethylene in presence of CaO, MgO, zeolite and calcined dolomite

    Energy Technology Data Exchange (ETDEWEB)

    Taralas, G.; Sjoestroem, K.; Jaeraas, S.; Bjoernbom, E. [Royal Inst. of Tech., Stockholm (Sweden). Dept. of Chemical Technology

    1993-12-31

    The subject of the present work is to study the effect of catalysts such as calcined dolomite (CaO.MgO), CaO (quicklime), MgO and Zeolite (EKZ-4) on the cracking of ethylene in the presence and absence of steam. N-heptane, toluene, naphthalene, thiophene have been some suitable model compounds for studies of the thermal and catalytic decomposition of tar. Previous results showed that the reaction scheme of the thermal decomposition of n-heptane was consistent with the high yield of ethylene observed in thermal decomposition of n-heptane. The effect of the reactor wall and the ferric impurities in the dolomite are also subjects of the research in this study. The results may also throw some additional light on the nature of the gas-phase thermal and catalytic reactions occurring in the use of dolomite as tar cracking catalysts. 28 refs

  1. Insights into the dolomitization process and porosity modification in sucrosic dolostones, Avon Park Formation (Middle Eocene), East-Central Florida, U.S.A.

    KAUST Repository

    Maliva,, Robert G.

    2011-03-01

    The Avon Park Formation (middle Eocene) in central Florida, U.S.A., contains shallow-water carbonates that have been replaced by dolomite to varying degrees, ranging from partially replaced limestones, to highly porous sucrosic dolostones, to, less commonly, low-porosity dense dolostones. The relationships between dolomitization and porosity and permeability were studied focusing on three 305-m-long cores taken in the City of Daytona Beach. Stable-isotope data from pure dolostones (mean δ 18O = +3.91% V-PDB) indicate dolomite precipitation in Eocene penesaline pore waters, which would be expected to have been at or above saturation with respect to calcite. Nuclear magnetic log-derived porosity and permeability data indicate that dolomitization did not materially change total porosity values at the bed and formation scale, but did result in a general increase in pore size and an associated substantial increase in permeability compared to limestone precursors. Dolomitization differentially affects the porosity and permeability of carbonate strata on the scale of individual crystals, beds, and formations. At the crystal scale, dolomitization occurs in a volume-for-volume manner in which the space occupied by the former porous calcium carbonate is replaced by a solid dolomite crystal with an associated reduction in porosity. Dolomite crystal precipitation was principally responsible for calcite dissolution both at the actual site of dolomite crystal growth and in the adjoining rock mass. Carbonate is passively scavenged from the formation, which results in no significant porosity change at the formation scale. Moldic pores after allochems formed mainly in beds that experienced high degrees of dolomitization, which demonstrates the intimate association of the dolomitization process with carbonate dissolution. The model of force of crystallization-controlled replacement provides a plausible explanation for key observations concerning the dolomitization process in the

  2. Tube structures of probable microbial origin in the Neoarchean Carawine Dolomite, Hamersley Basin, Western Australia.

    Science.gov (United States)

    Murphy, M A; Sumner, D Y

    2008-01-01

    The approximately 2.63 Ga Carawine Dolomite, Hamersley Basin, Western Australia, preserves tube structures of probable microbial origin that formed in a low energy environment. The tubes are 0.4-1.8 cm in diameter and at least 10-16 cm long in outcrop. The tubes are defined by dark, 45-microm-thick dolomicritic walls, whereas the tube fill and host rock are composed of 30 microm, cloudy dolomite crystals and rare 170- to 425-microm-wide, dark well-sorted clasts. Closely spaced, rarely discontinuous laminae coat the insides of tubes; less closely spaced, peaked, discontinuous laminae coat the outsides of tubes. The laminae on the outsides of tubes are often intercalated with mammilate structures. The presence of probable microbial coatings on both the insides and the outsides of the tube walls requires that the tubes formed above the sediment-water interface. These tube structures probably formed during gas-charged fluid escape, similar to tubes observed in ancient and modern hydrocarbon seeps and cylindrical water transfer structures in sandstones. The laminae that coat the tubes have very similar geometries to modern biofilms that form in both turbulent and laminar flow, and their geometries probably reflect flow conditions during the fluid escape. The identification of these structures suggests that the preserved interaction between fluid escape and microbial growth in carbonates may be more common than previously thought.

  3. Direct nanoscale observations of the coupled dissolution of calcite and dolomite and the precipitation of gypsum.

    Science.gov (United States)

    Offeddu, Francesco Giancarlo; Cama, Jordi; Soler, Josep Maria; Putnis, Christine V

    2014-01-01

    In-situ atomic force microscopy (AFM) experiments were performed to study the overall process of dissolution of common carbonate minerals (calcite and dolomite) and precipitation of gypsum in Na2SO4 and CaSO4 solutions with pH values ranging from 2 to 6 at room temperature (23 ± 1 °C). The dissolution of the carbonate minerals took place at the (104) cleavage surfaces in sulfate-rich solutions undersaturated with respect to gypsum, by the formation of characteristic rhombohedral-shaped etch pits. Rounding of the etch pit corners was observed as solutions approached close-to-equilibrium conditions with respect to calcite. The calculated dissolution rates of calcite at pH 4.8 and 5.6 agreed with the values reported in the literature. When using solutions previously equilibrated with respect to gypsum, gypsum precipitation coupled with calcite dissolution showed short gypsum nucleation induction times. The gypsum precipitate quickly coated the calcite surface, forming arrow-like forms parallel to the crystallographic orientations of the calcite etch pits. Gypsum precipitation coupled with dolomite dissolution was slower than that of calcite, indicating the dissolution rate to be the rate-controlling step. The resulting gypsum coating partially covered the surface during the experimental duration of a few hours.

  4. Molecular resolution friction microscopy of Cu phthalocyanine thin films on dolomite (104) in water.

    Science.gov (United States)

    Nita, Paweł; Pimentel, Carlos; Luo, Feng; Milián-Medina, Begoña; Gierschner, Johannes; Pina, Carlos M; Gnecco, Enrico

    2014-07-21

    The reliability of ultrathin organic layers as active components for molecular electronic devices depends ultimately on an accurate characterization of the layer morphology and ability to withstand mechanical stresses on the nanoscale. To this end, since the molecular layers need to be electrically decoupled using thick insulating substrates, the use of AFM becomes mandatory. Here, we show how friction force microscopy (FFM) in water allows us to identify the orientation of copper(ii)phthalocyanine (CuPc) molecules previously self-assembled on a dolomite (104) mineral surface in ultra-high vacuum. The molecular features observed in the friction images show that the CuPc molecules are stacked in parallel rows with no preferential orientation with respect to the dolomite lattice, while the stacking features resemble well the single CuPc crystal structure. This proves that the substrate induction is low and makes friction force microscopy in water a suitable alternative to more demanding dynamic AFM techniques in ultra-high vacuum.

  5. Crystal structure study of a cobaltoan dolomite from Kolwezi, Democratic Republic of Congo.

    Science.gov (United States)

    Perchiazzi, Natale

    2015-03-01

    A structural study has been undertaken on a cobaltoan dolomite, with chemical formula CaMg0.83Co0.17(CO3)2 (cal-cium magnesium cobalt dicarbonate), from Kolwezi, Democratic Republic of Congo. Pale-pink euhedral cobaltoan dolomite was associated with kolwezite [(Cu1.33Co0.67)(CO3)(OH)2] and cobaltoan malachite [(Cu,Co)2(CO3)(OH)2]. A crystal with a Co:Mg ratio of 1:5.6 (SEM/EDAX measurement), twinned on (11 -2 0) was used for crystal structural refinement. The refinement of the structural model of Reeder & Wenk [Am. Mineral. (1983 ▶), 68, 769-776; Ca at site 3a with site symmetry -3; Mg site at site 3b with site symmetry -3; C at site 6c with site symmetry 3; O at site 18f with site symmetry 1] showed that Co is totally incorporated in the Mg site, with refined occupancy Mg0.83Co0.17, which compares with Mg0.85Co0.15 from chemical data. The Co substitution reflects in the expansion of the cell volume, with a pronounced increasing of the c cell parameter.

  6. Modeling the Effect of Dissolved Hydrogen Sulfide on Mg2+-water Complex on Dolomite {104} Surfaces

    CERN Document Server

    Shen, Zhizhang; Brown, Philip E; Szlufarska, Izabela; Xu, Huifang

    2016-01-01

    The key kinetic barrier to dolomite formation is related to the surface Mg2+-H2O complex, which hinders binding of surface Mg2+ ions to the CO3 2- ions in solution. It has been proposed that this reaction can be catalyzed by dissolved hydrogen sulfide. To characterize the role of dissolved hydrogen sulfide in the dehydration of surface Mg 2+ ions, ab initio simulations based on density functional theory (DFT) were carried out to study the thermodynamics of competitive adsorption of hydrogen sulfide and water on dolomite (104) surfaces from solution. We find that water is thermodynamically more stable on the surface with the difference in adsorption energy of -13.6 kJ/mol (in vacuum) and -12.8 kJ/mol (in aqueous solution). However, aqueous hydrogen sulfide adsorbed on the surface increases the Mg2+-H2O distances on surrounding surface sites. Two possible mechanisms were proposed for the catalytic effects of adsorbed hydrogen sulfide on the anhydrous Ca-Mg-carbonate crystallization at low temperature.

  7. The formation mechanism of high-quality dolomite reservoir in the deep of Puguang Gas Field

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The discovery of Puguang Gas Field provides the exploration of China deep marine carbonate rock with important references.In Puguang Gas Field,the dolomite reservoirs discovered in the deep are the best in the present of China,which present big thickness and wide-range distribution,and develop abundant secondary porosity.The researches show that Puguang Gas Field bears the characteristics of early gas-filling time,deep burial,high matured organic matter and long-term interaction of hydrocarbon(oil and gas)-water-rock(carbonate reservoir).The developments of secondary pores in this area are affected by multiple diagenesis and their formation mechanisms are complicated.Through the research on depositional environment,sedimentary facies and reservoir porosity characters of Changxing and Feixianguan Formations,it is thought that high-quality dolomite reservoirs of Puguang Gas Field form on the favorable sedimentary facies belts,which are the integrate result affected by several factors including superficial corrosion,burial corrosion,overpressure and tectonic movement,among which burial corrosion of TSR to reservoir and overpressure formed by thermal evolution of organic matter have great effect on the formation of secondary porosity of Changxing and Feixianguan Formations.

  8. 高硅白云石皮江法炼镁实验%High Silica Dolomite Pidgeon Smelt Magnesium Experiment

    Institute of Scientific and Technical Information of China (English)

    李波; 褚丙武

    2015-01-01

    Magnesium smelting by Pidgeon process requirements SiO2 should be less than 0 .5% in dolomite . Previous studies that SiO2 with MgO style in the high temperature generated 2MgO.SiO2 , It's a kind of low melting point compound . It can make the dolomite sintering . It lets the calcined dolomite could not reach the requirements of smelting magnesium , a certain extent , reduce the yield .This paper studies the reason of low yield in magnesium smelting by Pidgeon process used high silica ( SiO 2 4 .51% ) dolomite . And proposed and verified by the experimental it can achieve high magnesium yield high by Pidgeon process used high silica ( SiO2 4 .51% ) dolomite . It is possible of magnesium smelting by Pidgeon process used high silica dolomite .%皮江法炼镁要求白云石中SiO2应小于0.5%。前人研究认为SiO2在高温时与MgO生成2M gO · SiO2,这是一种低熔点化合物,它会使白云石烧结,使煅烧后的白云石达不到炼镁的要求,在一定程度上降低收得率。本文研究了高硅(SiO2为4.51%)白云石皮江法炼镁镁收率低的原因,提出并通过实验验证了高硅白云石采用皮江法炼镁,也可以达到高的镁收率。使高硅白云石采用皮江法炼镁成为可能。

  9. Common Ion Effects In Zeoponic Substrates: Dissolution And Cation Exchange Variations Due to Additions of Calcite, Dolomite and Wollastonite

    Science.gov (United States)

    Beiersdorfer, R. E.; Ming, D. W.; Galindo, C., Jr.

    2003-01-01

    c1inoptilolite-rich tuff-hydroxyapatite mixture (zeoponic substrate) has the potential to serve as a synthetic soil-additive for plant growth. Essential plant macro-nutrients such as calcium, phosphorous, magnesium, ammonium and potassium are released into solution via dissolution of the hydroxyapatite and cation exchange on zeolite charged sites. Plant growth experiments resulting in low yield for wheat have been attributed to a Ca deficiency caused by a high degree of cation exchange by the zeolite. Batch-equilibration experiments were performed in order to determine if the Ca deficiency can be remedied by the addition of a second Ca-bearing, soluble, mineral such as calcite, dolomite or wollastonite. Variations in the amount of calcite, dolomite or wollastonite resulted in systematic changes in the concentrations of Ca and P. The addition of calcite, dolomite or wollastonite to the zeoponic substrate resulted in an exponential decrease in the phosphorous concentration in solution. The exponential rate of decay was greatest for calcite (5.60 wt. % -I), intermediate for wollastonite (2.85 wt.% -I) and least for dolomite (1.58 wt.% -I). Additions of the three minerals resulted in linear increases in the calcium concentration in solution. The rate of increase was greatest for calcite (3.64), intermediate for wollastonite (2.41) and least for dolomite (0.61). The observed changes in P and Ca concentration are consistent with the solubilities of calcite, dolomite and wollastonite and with changes expected from a common ion effect with Ca. Keywords: zeolite, zeoponics, common-ion effect, clinoptilolite, hydroxyapatite

  10. Calcite and dolomite in intrusive carbonatites. II. Trace-element variations

    Science.gov (United States)

    Chakhmouradian, Anton R.; Reguir, Ekaterina P.; Couëslan, Christopher; Yang, Panseok

    2016-04-01

    The composition of calcite and dolomite from several carbonatite complexes (including a large set of petrographically diverse samples from the Aley complex in Canada) was studied by electron-microprobe analysis and laser-ablation inductively-coupled-plasma mass-spectrometry to identify the extent of substitution of rare-earth and other trace elements in these minerals and the effects of different igneous and postmagmatic processes on their composition. Analysis of the newly acquired and published data shows that the contents of rare-earth elements (REE) and certain REE ratios in magmatic calcite and dolomite are controlled by crystal fractionation of fluorapatite, monazite and, possibly, other minerals. Enrichment in REE observed in some samples (up to ~2000 ppm in calcite) cannot be accounted for by coupled substitutions involving Na, P or As. At Aley, the REE abundances and chondrite-normalized (La/Yb)cn ratios in carbonates decrease with progressive fractionation. Sequestration of heavy REE from carbonatitic magma by calcic garnet may be responsible for a steeply sloping "exponential" pattern and lowered Ce/Ce* ratios of calcite from Magnet Cove (USA) and other localities. Alternatively, the low levels of Ce and Mn in these samples could result from preferential removal of these elements by Ce4+- and Mn3+-bearing minerals (such as cerianite and spinels) at increasing f(O2) in the magma. The distribution of large-ion lithophile elements (LILE = Sr, Ba and Pb) in rock-forming carbonates also shows trends indicative of crystal fractionation effects (e.g., concomitant depletion in Ba + Pb at Aley, or Sr + Ba at Kerimasi), although the phases responsible for these variations cannot be identified unambiguously at present. Overall, element ratios sensitive to the redox state of the magma and its complexing characteristics (Eu/Eu*, Ce/Ce* and Y/Ho) are least variable and in both primary calcite and dolomite, approach the average chondritic values. In consanguineous

  11. Reconstructing conditions during dolomite formation on a Carnian coastal sabkha/alluvial plain using 87Sr/86Sr isotopes - Travenanzes Formation, northern Italy

    Science.gov (United States)

    Rieder, Maximilian; Wegner, Wencke; Horschinegg, Monika; Preto, Nereo; Breda, Anna; Klötzli, Urs; Peckmann, Jörn; Meister, Patrick

    2016-04-01

    The study of large amounts of dolomite that formed in the Triassic Tethyan realm is hampered by late diagenetic or hydrothermal overprint. These dolomites are difficult to link to past environmental and early diagenetic conditions, and their correlation to models for dolomite formation in modern environments is problematic. Preto et al. (2015) suggested, based on evidence from nano-scale structure analysis by transmission electron microscopy and petrographic observations, that dolomites in the Carnian Travenanzes Formation of the Southern Alps (Dolomites area) represent a preserved primary phase. The Travenanzes Formation was deposited in an extended alluvial plain or coastal sabkha environment subject to a semi-arid climate. Beds and nodules of nearly stoichiometric dolomite are embedded in large amounts of clay, which shielded early formed dolomite from diagenetic fluids. This finding of penecontemporaneous dolomite provides an ideal model case for reconstructing past environmental conditions at the time of dolomite precipitation. While Preto et al. (2015) argued that dolomite formation was mediated by extracellular polymeric substances produced by sulphate-reducing bacteria, it remains unclear whether precipitation occurred from evaporating seawater or mainly from brine derived from evaporating continental groundwater. Both cases exist in modern environments of dolomite formation. In the coastal sabkhas of Abu Dhabi and Qatar, dolomite precipitates from concentrated brine derived from seawater, either through seepage and reflux or through evaporative pumping (the sabkha model). In the coastal ephemeral lakes of the Coorong Lagoon system (South Australia) dolomite precipitation occurs from evaporating groundwater. The goal of this study is to distinguish marine from continental influence during formation of Carnian dolomite using 87Sr/86Sr isotope ratios. Sr isotopes could reveal different origins of ionic solutions for dolomite precipitation, which is not

  12. Reactive transport modeling of ferroan dolomitization by seawater interaction with mafic igneous dikes and carbonate host rock at the Latemar platform, Italy

    Science.gov (United States)

    Blomme, Katreine; Fowler, Sarah Jane; Bachaud, Pierre

    2017-04-01

    The Middle Triassic Latemar carbonate platform, northern Italy, has featured prominently in the longstanding debate regarding dolomite petrogenesis [1-4]. Recent studies agree that ferroan and non-ferroan dolomite replaced calcite in limestone during reactive fluid flow at altered mafic igneous dikes that densely intrude the platform. A critical observation is that ferroan dolomite abundances increase towards the dikes. We hypothesize that seawater interacted with mafic minerals in the dikes, leading to Fe enrichment in the fluid that subsequently participated in dolomitization. This requires that dolomite formation was preceded by dike alteration reactions that liberated Fe and did not consume Mg. Another requirement is that ferroan and non-ferroan dolomite (instead of other Fe- and Mg-bearing minerals) formed during fluid circulation within limestone host rock. We present reactive transport numerical simulations (Coores-Arxim, [5]) that predict equilibrium mineral assemblages and the evolution of fluid dolomitizing potential from dike crystallization, through dike alteration by seawater, to replacement dolomitization in carbonate host rock. The simulations are constrained by observations. A major advantage of the simulations is that stable mineral assemblages are identified based on a forward modeling approach. In addition, the dominant igneous minerals (plagioclase, clinopyroxene olivine and their alteration products) are solid solutions. Most reactive transport simulations of carbonate petrogenesis do not share these benefits (e.g. [6]). Predicted alteration mineral assemblages are consistent with observations on dikes and with ferroan and non-ferroan dolomite genesis. The simulation results also show that fluid dolomitizing potential (Mg/Ca and Fe/Mg) increases during dissolution of igneous solid solution minerals. Enrichment in fluid Fe concentration is sufficient to stabilize ferroan replacement dolomite. Consistent with field observations, ferroan dolomite

  13. The equilibrium between diagenetic calcites and dolomites and its impact on reservoir quality in the sandstone reservoir of Kela 2 gas field

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Based on the equilibrium theory of chemical reactions between water and rocks, this paper establishes a thermodynamic phase relationship diagram among calcites, dolomites and water solution under the condition of diagenesis based on the thermodynamic database of related minerals and fluids and dolomite's degree of order parameters. It has been discovered that the equilibrium between calcites and dolomites in the diagenetic environment is strongly impacted by temperature and the Ca/Mg ratios in groundwater, and that the dolomite's degree of order in the diagenetic environment is a function of crystallization temperature and time, not controlled by water solution. Hereby, the authors make a further analysis of the close relationship of chemical reaction between carbonate cements and pore water in the sandstone reservoirs of Kala 2 gas field in Kuche sag. It can be seen that there are different impacts on sandstone reservoir quality among the equilibrium system of calcites, dolomites and pore water at different depths of reservoirs.

  14. Converter smelting practice on dolomites partly replace light-burned dolomites%生白云石部分替代轻烧白云石转炉冶炼实践

    Institute of Scientific and Technical Information of China (English)

    张思维

    2014-01-01

    This paper analyzed the feasibility of the technology by substituting dolomites for some light-burned dolomites in converter,and on this basis,furtherly elaborated the slagging mechanism of the substitution process and the effect on the process slag and phosphorous.The practice showed that ,substituting dolomites for some light-burned dolomites,can satisfy the need of steel-making production and reduce cost of the flux.%分析了转炉用生白云石替代部分轻烧工艺方案的可行性,在此基础上进一步阐述了生白云石替代工艺的造渣机理、对过程炉渣和去磷效果的影响及其应用效果。实践证明,使用生白云石替代部分轻烧,能满足转炉生产需要,可降低熔剂成本。

  15. [Hydrochemistry and Dissolved Inorganic Carbon Stable Isotope of Shibing Dolomite Karst Area in Guizhou Province].

    Science.gov (United States)

    Xiao, Shi-zhen; Lan, Jia-cheng; Yuan, Dao-xian; Wang, Yun; Yang, Long; Ao, Xiang-hong

    2015-06-01

    Totally 49 water samples were collected in Shibing Dolomite Karst World Natural Heritage Site in Guizhou Province to analyze the characteristics and controlling factors of both the surface and underground waters, as well as the features and their origins of the dissolved inorganic carbon isotope. It was found that the pH of the study area was neutral to alkaline with low concentrations of total dissolved solids. The cations were dominated by Ca2+, Mg2 and anions by HCO3-, featured by HCO3-Ca x Mg type water. The ratios of Cl-, NO3- and SO4(2-) in the allogenic water from the shale area in the northern catchment were higher than those in autogenic water from the dolomite karst area, so did the concentration of Si. The SIc and SId of the allogenic waters in the shale area were negative. After the waters entered into and flew by the dolomite karst area, both the SIc and SId increased to over 0. It could be told by the water chemistry that the hydrochemistry was little impacted by the rainfall and human activities. The Gibbs plot revealed that the chemical composition of the waters was mainly controlled by rock weathering. The δ(13)C(DIC) of the surface waters ranged from -8.27% to -11.55% per hundred, averaging -9.45% per hundredo, while that of the underground waters ranged from -10.57% per hundred to -15.59% per hundred, averaging -12.04% per hundred, which was lighter than that of surface water. For the distribution features, it was found the δ(13)C(DIC), of the upper reaches of branches of Shangmuhe River was lighter than that of the lower reach, while that of the main river Shangmuhe River was relatively complex. Based on the mass balance of stable isotopes and the δ(13)C(DIC), the ratio of the origin of DIC of the ground water was calculated. It was found that 51.2% was from soil CO2, and 48.8% was from the rock itself.

  16. Basic data report for drillholes at the H-11 complex (Waste Isolation Pilot Plant-WIPP)

    Energy Technology Data Exchange (ETDEWEB)

    Mercer, J.W. (Sandia National Labs., Albuquerque, NM (USA)); Snyder, R.P. (Geological Survey, Denver, CO (USA))

    1990-05-01

    Drillholes H-11b1, H-11b2, and H-11b3 were drilled from August to December 1983 for site characterization and hydrologic studies of the Culebra Dolomite Member of the Upper Permian Rustler Formation at the Waste Isolation Pilot Plant (WIPP) site in southeastern New Mexico. In October 1984, the three wells were subjected to a series of pumping tests designed to develop the wells, provide information on hydraulic communication between the wells, provide hydraulic properties information, and to obtain water samples for quality of water measurements. Based on these tests, it was determined that this location would provide an excellent pad to conduct a convergent-flow non-sorbing tracer test in the Culebra dolomite. In 1988, a fourth hole (H-11b4) was drilled at this complex to provide a tracer-injection hole for the H-11 convergent-flow tracer test and to provide an additional point at which the hydraulic response of the Culebra H-11 multipad pumping test could be monitored. A suite of geophysical logs was run on the drillholes and was used to identify different lithologies and aided in interpretation of the hydraulic tests. 4 refs., 6 figs., 6 tabs.

  17. Study of the Reed Dolomite Aided by Remotely Sensed Imagery, Central White-Inyo Range, Easternmost California

    Science.gov (United States)

    Ernst, W. G.; Paylor, Earnest D., II

    1996-01-01

    Remote-sensing methods are of great value in assessing the stratigraphy and geologic structure of inaccessible terrains, especially where lithologic contrasts are marked. In this report, we show that such techniques can be successfully applied to a massive carbonate unit, the Reed Dolomite, exposed in the Wacuoba Mountain, Blanco Mountain, and Mount Barcroft quadrangles of east-central California.

  18. Dolomitic lime amendment affects pine bark substrate pH, nutrient availability, and plant growth: A review

    Science.gov (United States)

    Dolomitic lime (DL) is one of the most commonly used fertilizer amendments in nursery container substrates. It is used to adjust pH of pine bark substrates from their native pH, 4.1 to 5.1, up to about pH 6. Additions of DL have been shown to be beneficial, inconsequential, or detrimental dependin...

  19. Carbon Isotope Evolution of Early Proterozoic Dolomites of Wutai Mountain Area,North China

    Institute of Scientific and Technical Information of China (English)

    钟华; 马永生; 霍卫国; 姚御元

    1994-01-01

    Carbon isotope of the early Proterozoic carbonates from the Hutuo Group of the type sec-tion in Wutai Mountain area,Shanxi Province,North China,is reported.Isotopic analyses have been madefor 484 samples of dolomites.The carbon isotope results show:(i)δ13C values distinctly change with the ge-ological time,but are relatively stable in certain horizon;(ii)like that at the Cretaceous/Tertiary and Permi-an/Triassic boundaries,δ13C values also show abrupt variation across the boundaries between the JianancunFormation and the Daguandong Formation and between the Daguandong Formation and the Huaiyincun For-mation.

  20. Assessment of the dose from radon and its decay products in the Bozkov dolomite cave.

    Science.gov (United States)

    Rovenská, K; Thinová, L; Zdímal, V

    2008-01-01

    The dose from radon and its progeny remains a frequently discussed problem. ICRP 65 provides a commonly used methodology to calculate the dose from radon. Our work focuses on a cave environment and on assessing the doses in public open caves. The differences in conditions (aerosol size distribution, humidity, radon and its progeny ratio, etc.) are described by the so-called cave factor j. The cave factor is used to correct the dose for workers which is calculated using the ICRP 65 recommendation. In this work, the authors have brought together measured data of aerosol size distribution, unattached and attached fraction activity, and have calculated the so-called cave factor for the Bozkov dolomite cave environment. The dose conversion factors based on measured data and used for evaluating the cave factor were calculated by LUDEP software, which implements HRTM ICRP66.

  1. Characterizations of strontium(II) and barium(II) adsorption from aqueous solutions using dolomite powder.

    Science.gov (United States)

    Ghaemi, Ahad; Torab-Mostaedi, Meisam; Ghannadi-Maragheh, Mohammad

    2011-06-15

    In this research, adsorption technique was applied for strontium and barium removal from aqueous solution using dolomite powder. The process has been investigated as a function of pH, contact time, temperature and adsorbate concentration. The experimental data was analyzed using equilibrium isotherm, kinetic and thermodynamic models. The isotherm data was well described by Langmuir isotherm model. The maximum adsorption capacity was found to be 1.172 and 3.958 mg/g for Sr(II) and Ba(II) from the Langmuir isotherm model at 293 K, respectively. The kinetic data was tested using first and pseudo-second order models. The results indicated that adsorption fitted well with the pseudo-second order kinetic model. The thermodynamic parameters (ΔG°, ΔH°, and ΔS°) were also determined using the equilibrium constant value obtained at different temperatures. The results showed that the adsorption for both ions was feasible and exothermic.

  2. Molecular characterization of an endolithic microbial community in dolomite rock in the central Alps (Switzerland).

    Science.gov (United States)

    Horath, Thomas; Bachofen, Reinhard

    2009-08-01

    Endolithic microorganisms colonize the pores in exposed dolomite rocks in the Piora Valley in the Swiss Alps. They appear as distinct grayish-green bands about 1-8 mm below the rock surface. Based on environmental small subunit ribosomal RNA gene sequences, a diverse community driven by photosynthesis has been found. Cyanobacteria (57 clones), especially the genus Leptolyngbya, form the functional basis for an endolithic community which contains a wide spectrum of so far not characterized species of chemotrophic Bacteria (64 clones) with mainly Actinobacteria, Alpha-Proteobacteria, Bacteroidetes, and Acidobacteria, as well as a cluster within the Chloroflexaceae. Furthermore, a cluster within the Crenarchaeotes (40 clones) has been detected. Although the eukaryotic diversity was outside the scope of the study, an amoeba (39 clones), and several green algae (51 clones) have been observed. We conclude that the bacterial diversity in this endolithic habitat, especially of chemotrophic, nonpigmented organisms, is considerable and that Archaea are present as well.

  3. Enhancement of CO2 capture in limestone and dolomite granular beds by high intensity sound waves

    Science.gov (United States)

    Valverde, Jose Manuel; Perez-Ebri, Jose Manuel; Sanchez-Quintanilla, Miguel Angel

    2017-06-01

    The calcium looping (CaL) process, based on the calcination/carbonation of CaCO3 at high temperatures, has emerged in the last years as a potentially low cost technology for CO2 capture. In this work, we show that the application of high intensity sound waves to granular beds of limestone and dolomite in a CaL reactor enhances significantly their multicycle CO2 capture capacity. Sound waves are applied either during the calcination stage of each CaL cycle or in the carbonation stage. The effect of sound is to intensify the transfer of heat, mass and momentum and is more marked when sound is applied during calcination by promoting CaO regeneration. The application of sound would allow reducing the calcination temperature thereby mitigating the decay of capture capacity with the number of cycles and reducing the energy penalty of the technology.

  4. UPPER TRIASSIC AMBER FROM THE DOLOMITES (NORTHERN ITALY.A PALEOCLIMATIC INDICATOR?

    Directory of Open Access Journals (Sweden)

    PIERO GIANOLLA

    1998-11-01

    Full Text Available Amber in Triassic deposits in the Dolomites is demonstrated for the first time. The amber-bearing deposits belong to the middle part of the Dürrenstein Formation, referred to uppermost Julian (Lower Carnian, about 225 My. Chemico-physical features of amber, which occurs as small yellow to reddish droplets, have been determined. Infrared (IR spectroscopy shows typical bands of fossil resins; the "fingerprint" region of the spectrum presents a unique pattern that cannot be referred to any other known fossil resin. Palynological investigation of amber-bearing layers shows a large prevalence of bisaccates and circumpolles. Particularly, the taeniate bisaccates are frequent (41% and suggest a correlation with the amber-producing species. Amber production and preservation is possibly related to a humid climatic event. 

  5. Recent slope failures in the Dolomites (Northeastern Italian Alps) in a context of climate change

    Science.gov (United States)

    Chiarle, Marta; Paranunzio, Roberta; Laio, Francesco; Nigrelli, Guido; Guzzetti, Fausto

    2014-05-01

    Climate change in the Greater Alpine Region is seriously affecting permafrost distribution, with relevant consequences on slope stability. In the Italian Alps, the number of failures from rockwalls at high elevation markedly increased in the last 20-30 years: the consistent temperature increase, which warmed twice than the global average, may have seriously influenced slope stability, in terms of glaciers retreat and permafrost degradation. Moreover, the growing number of tourists and activities in alpine regions (in particular in the Dolomites) made these areas particularly critical in relation to natural hazards. In this light, an integrated short-term geomorphological and climatic analysis was performed, in order to better comprehend the impact of main climate elements (especially temperature and precipitation) on slope failures in high mountain areas. In this contribution, we focus on three recent slope failures occurred at high elevation sites in the Dolomites (Northeastern Italian Alps), declared a UNESCO World Heritage Site in August 2009. We describe here three important rock falls occurred in the autumn 2013: 1) the Sorapiss rock fall, on 30 September 2013; 2) the Monte Civetta rock fall, on 16 November 2013; 3) the Monte Antelao rock fall, on 22 November 2013. The Monte Civetta rock fall damaged some climbing routes, while the other two landslides did not cause any damage or injury. Despite the limited volume involved, these three events represent an important warning sign in the context of ongoing climate change. Geomorphological information about the rock fall sites were combined with the climatic data acquired from the meteorological stations surrounding the slope failure areas. A short-term climatic analysis was performed, with the aim of understanding the role of the main climatic elements in the triggering of natural instability events in this area and in the Alps in general.

  6. The Main Origins of High Quality Reservoir in Feixianguan Formation in Northeast Sichuan Basin: Atmospheric Water Eluviation and Seepage-reflux Dolomitization%川东北地区孤立台地飞仙关组优质储层形成主控因素——大气淡水淋滤及渗透回流白云石化

    Institute of Scientific and Technical Information of China (English)

    张建勇; 周进高; 潘立银; 王小芳; 王芳; 郝毅; 谷明峰; 张润合; 陈薇

    2013-01-01

    The depositional environment was isolated restricted platform and a lot of depositional cycles of shallow upward oolite shoal existed at the stage from Member 1 to 2 of Feixianguan Formation of Lower Triassic in the northeast Sichuan basin,especially gypsum lagoon at the Member 2 of Feixianguan Formation in the isolated restricted platform. On the isolated restricted platform geologic setting,the main lithol-ogy of reservoir includes remnant oolitic dolomite and finely crystalline dolomite. On the shallow upward o-olite shoal geologic setting,the atmospheric water eluviation results in the lithology sequence from top to bottom is tight micrite dolomite,intragranular pore or moldic pore residual oolith micritic or powder crystalline dolomite,intragranular pore residual oolith powder or finely crystalline dolomite,and intercrystalline pore dolomite. Petrology and geochemistry of reservoir show that the reservoir dolomite underwent two stages of dolomitization. The first stage is seepage-reflux dolomitization and the second is burial dolomitiza-tion. The seepage-reflux dolomitization make an important role in preservation of early pores and increase rock strength, inhibit pressure solution and cementation, but the buried dolomitization partially fill pore space. It can be recognized two types of buried dissolution. The first stage happened after seepage reflux dolomitization and before crude oil filling and it is correlated with dissolution by organic acid. The second occurred in the deep buried environment,it is correlated with acid generated by TSR. The buried dissolution can not generate reservoir porosity,but increases permeability. Based on comprehensive studies of geologic settings,reservoir petrology and geochemistry,it is concluded that the atmospheric water eluviation is prerequisite condition for reservoir porosity generation and the seepage-reflux dolomitization is necessary condition for reservoir porosity preservation.%川东北地区在三叠系飞仙

  7. The main texture of dolomite of Middle Permian, western Sichuan basin: Concurrently on the differences with Upper Permian-Triassic, Northeast Sichuan basin%四川盆地西部中二叠统白云岩/石的主要结构类型——兼论其与川东北上二叠统一三叠系白云岩/石的差异

    Institute of Scientific and Technical Information of China (English)

    黄思静; 吕杰; 兰叶芳; 黄可可; 王春梅

    2011-01-01

    Qixia Formation in western Sichuan basin could be regard as a non-classical one, because the transitional rock type of 40% to 60% dolomite content is dominant; whereas the model of Changxing Formation of Upper Permian-Triassic dolomite in northeastern Sichuan basin could be seen as a classical one that has two dominant end-member rock types of more than 90% or less than 10% dolomite content respectively. The different dolomite textures could reflect the Qixia dolomite experienced the higher crystallization temperature, the lower Mg/Ca ratio of fluids and the shorter duration and incomplete halfway back dolomitization. In contrast, the Upper Permian-Triassic dolomite in northeastern Sichuan basin underwent the complete dolomitization with lower temperatures and marine-derived fluids of high Mg/Ca ratio.

  8. Hydrothermal dolomitization of the Bekhme formation (Upper Cretaceous), Zagros Basin, Kurdistan Region of Iraq: Record of oil migration and degradation

    Science.gov (United States)

    Mansurbeg, Howri; Morad, Daniel; Othman, Rushdy; Morad, Sadoon; Ceriani, Andrea; Al-Aasm, Ihsan; Kolo, Kamal; Spirov, Pavel; Proust, Jean Noel; Preat, Alain; Koyi, Hemin

    2016-07-01

    The common presence of oil seepages in dolostones is widespread in Cretaceous carbonate successions of the Kurdistan Region of Iraq. This integrated field, petrographic, chemical, stable C, O and Sr isotopes, and fluid inclusion study aims to link dolomitization to the origin and geochemical evolution of fluids and oil migration in the Upper Cretaceous Bekhme carbonates. Flux of hot basinal (hydrothermal) brines, which is suggested to have occurred during the Zagros Orogeny, resulted in dolomitization and cementation of vugs and fractures by coarse-crystalline saddle dolomite, equant calcite and anhydrite. The saddle dolomite and host dolostones have similar stable isotopic composition and formed prior to oil migration from hot (81-115 °C) basinal NaCl-MgCl2-H2O brines with salinities of 18-22 wt.% NaCl eq. The equant calcite cement, which surrounds and hence postdates saddle dolomite, has precipitated during oil migration from cooler (60-110 °C) NaCl-CaCl2-H2O brines (14-18 wt.% NaCl eq). The yellowish fluorescence color of oil inclusions in the equant calcite indicates that the oil had API gravity of 15-25° composition, which is lighter than present-day oil in the reservoirs (API of 10-17°). This difference in oil composition is attributed to oil degradation by the flux of meteoric water, which is evidenced by the low δ13C values (- 8.5‰ to - 3.9‰ VPDB) as well as by nil salinity and low temperature in fluid inclusions of late columnar calcite cement. This study demonstrates that linking fluid flux history and related diagenesis to the tectonic evolution of the basin provides important clues to the timing of oil migration, degradation and reservoir evolution.

  9. Effect of dolomite decomposition under CO2 on its multicycle CO2 capture behaviour under calcium looping conditions.

    Science.gov (United States)

    de la Calle Martos, Antonio; Valverde, Jose Manuel; Sanchez-Jimenez, Pedro E; Perejón, Antonio; García-Garrido, Cristina; Perez-Maqueda, Luis A

    2016-06-28

    One of the major drawbacks that hinder the industrial competitiveness of the calcium looping (CaL) process for CO2 capture is the high temperature (∼930-950 °C) needed in practice to attain full calcination of limestone in a high CO2 partial pressure environment for short residence times as required. In this work, the multicycle CO2 capture performance of dolomite and limestone is analysed under realistic CaL conditions and using a reduced calcination temperature of 900 °C, which would serve to mitigate the energy penalty caused by integration of the CaL process into fossil fuel fired power plants. The results show that the fundamental mechanism of dolomite decomposition under CO2 has a major influence on its superior performance compared to limestone. The inert MgO grains resulting from dolomite decomposition help preserve a nanocrystalline CaO structure wherein carbonation in the solid-state diffusion controlled phase is promoted. The major role played by the dolomite decomposition mechanism under CO2 is clearly demonstrated by the multicycle CaO conversion behaviour observed for samples decomposed at different preheating rates. Limestone decomposition at slow heating rates yields a highly crystalline and poorly reactive CaCO3 structure that requires long periods to fully decarbonate and shows a severely reduced capture capacity in subsequent cycles. On the other hand, the nascent CaCO3 produced after dolomite half-decomposition consists of nanosized crystals with a fast decarbonation kinetics regardless of the preheating rate, thus fully decomposing from the very first cycle at a reduced calcination temperature into a CaO skeleton with enhanced reactivity as compared to limestone derived CaO.

  10. The characteristics and genetic mechanism of middle-upper Cambrian dolomite on the southeast margin of Sichuan Basin%四川盆地东南缘中上寒武统白云岩地球化学特征及成因机制

    Institute of Scientific and Technical Information of China (English)

    刘建清; 赵瞻; 林家善; 冯伟明; 黄学平; 魏洪刚

    2014-01-01

    提以系统的岩石学及中上寒武统3条剖面地球化学特征对比分析为基础,认为中上寒武统白云岩主要形成于埋藏早期高盐度卤水的渗透回流交代作用,次为混合水交代成因,其主要依据体现在:①中上寒武统白云岩及灰岩Sr/Ba总体较高,仅少量数据点Sr/Ba小于1;②灰岩Na、K含量较高,灰岩Na含量高于淡水成因的美国Wisconsin中奥陶统Mifflm Member灰岩以及美国Tennessee东部Tongling地区上奥陶统灰岩,白云岩Na含量与开宁盆地巴洼阶地潮上萨布哈白云岩中Na含量相近;③m值反映出灰岩为海水沉积环境,白云岩为与潟湖相关的沉积环境;④B校值反映出该区白云岩及灰岩主要形成于咸水-半咸水沉积环境,局部受淡水作用影响。该区白云岩化过程中Sr有明显带出现象,Na、K可能也有带出现象。%Based on petrological and geochemical analysis of middle-upper Cambrian dolomite in three different profiles, the authors hold that the dolomite was mainly formed by brine reflux dolomitization in the early bury period, together with mixing water replacement. The evidence obtained is as follows:①the ratios of Sr/Ba in dolomite and calcite are high, with only a few data being lower than 1;②the values of Na and K are high in calcite, the content of Na in calcite is higher than that of middle Ordovician Mifflm Member calcite in Wisconsin and that of upper-Ordovician calcite in Tongling of eastern Tennessee characterized by fresh water origin, and the content of Na in dolomite is equal to that of Sabkha dolomite in Barbwire terrace of Canning basin; ③ the values of m suggest that the calcite was in a seawater sedimentary environment, and the dolomite was in a lagoon sedimentary environment;④the values of revised B show that the calcite and dolomite were formed in salt and semi-salt water, partly affected by fresh water. The Sr values were impoverished during the dolomitization

  11. REE Compositions of Lower Ordovician Dolomites in Central and North Tarim Basin, NW China: A Potential REE Proxy for Ancient Seawater

    Institute of Scientific and Technical Information of China (English)

    ZHANG Xuefeng; HU Wenxuan; JIN Zhijun; ZHANG Juntao; QIAN Yixiong; ZHU Jingquan; ZHU Dongya; WANG Xiaolin; XIE Xiaomin

    2008-01-01

    Rare earth dement compositions of Lower Ordovician dolomites in the Central and Northern Tarim Basin are studied. Most dolomite samples are more or less contaminated by clay minerals. Their rare earth element compositions have been consequently changed, showing both seawater-like and non-seawater-like features. The clay contamination should be disposed before the REE data are used. Through ICP-MS and ICP-AES analyses, the REE features are well documented. The clay contamination is quantitatively determined by microscopic investigation, trace elements and REE contents. The dolomites, at least in the Tarim Basin, are thought to be pure when their total LREE contents are less than 3x10-6. Through comparison, the pure dolomites show similarities in REE patterns but differences in REE contents with co-existing pure limestone, which indicates that dolomitization may slightly change the REE compositions. Nevertheless, whatever the change is, the pure dolomites may act as a potential REE proxy for Ordovician seawater, which would be significant for ancient massive dolomite strata that lack limestone.

  12. Effects of surface orientation, fluid chemistry and mechanical polishing on the variability of dolomite dissolution rates

    Science.gov (United States)

    Saldi, Giuseppe D.; Voltolini, Marco; Knauss, Kevin G.

    2017-06-01

    Recent studies of carbonate surface reactivity have underscored the fundamental variability of dissolution rates and the heterogeneous distribution of the reaction over the mineral surface due to the inhomogeneous distribution of surface energy. Dolomite dissolution rates relative to different cleavage planes (r-planes) and surfaces cut approximately perpendicular to the c-axis (c-planes) were studied at 50 °C as a function of pH (3.4 ≤ pH ≤ 9.0) and solution composition by vertical scanning interferometry (VSI) and atomic force microscopy (AFM), with the aim of providing an estimate of the intrinsic rate variation of dolomite single crystals and describing the surface reaction distribution and the rate controlling mechanisms. Surface normal retreat rates measured under acidic conditions increased linearly with time and were not visibly affected by the parallel increase of surface roughness. Mean total dissolution rates of r-planes decreased by over 200 times from pH 3.4 to pH 9.0 and CO32--rich solutions, whereas corresponding rate variations spanned over 3 orders of magnitude when also c-plane rate distributions were included in the analysis. At acid to near neutral pH, c-planes dissolved ∼ three times faster than the adjoining r-planes but slower at basic pH and high total carbon concentration, displaying a distinctive morphologic evolution in these two regimes. The comparison of polished and unpolished crystals showed that polished cleavage planes dissolved about three times faster than the unpolished counterpart at near neutral to basic conditions, whereas no significant difference in reactivity was observed at pH topography over the course of the reaction, the evolution of the entire crystal morphology depends also on the reactivity of edge and corner regions, whose contribution to measured rates is not generally taken into account by laboratory experiments. The study of time-dependent mineral morphology and reactivity requires an integrated approach

  13. Capture and recycling of ammonium by dolomite-aided struvite precipitation and thermolysis.

    Science.gov (United States)

    Chen, Liang; Zhou, Chun Hui; Zhang, Hao; Tong, Dong Shen; Yu, Wei Hua; Yang, Hui Min; Chu, Mao Quan

    2017-11-01

    The capture and reuse of NH4(+) is an ideal solution to treat NH4(+)-containing wastewater. The capture and reuse process needs to be clean and cost-effective. Currently, however, there are many obstacles, particularly in the availability, cost, and recovery of the chemical sources required. Here, we demonstrate a clean and efficient method to capture and recycle NH4(+) by a dolomite-aided struvite precipitation process. Dolomite calcined carefully in CO2 atmosphere was used as a Mg source to react with PO4(3-) (KH2PO4) and NH4(+) in model wastewater (2000 mg L(-1) NH4(+)). The precipitation was performed at nMg(2+):nNH4(+):nPO4(3-) = 1:1:1.2 and pH = 8.0 for 2 h; 89.7% of NH4(+) was recovered in the form of struvite precipitate. The competition between K(+) and NH4(+) in the model wastewater led to the formation of K-struvite (MgKPO4·6H2O) and struvite (MgNH4PO4·6H2O). The formation of K-struvite resulted in a decrease in the NH4(+) removal rate. When struvite was heated at 110 °C for 4 h, the NH4(+) release rate from the thermolysis reached 75.7%. Thermolysis readily occurred as an unstable Ca(2+)-CO3(2-)-NH4(+) system formed in the mixture of MgNH4PO4·6H2O and CaCO3. The elements Mg and P that were obtained during the struvite precipitation-thermolysis-reprecipitation process can be repeatedly used. After 6 cycles, under the conditions pH = 9.0, nMg(2+):nNH4(+):nPO4(3-) = 1:1:1 and reaction time of 2 h, up to 78.3% of NH4(+) was removed from the model wastewater. Copyright © 2017 Elsevier Ltd. All rights reserved.

  14. On the origin and early diagenesis of early Triassic carbonate mud (Dolomites, Italy)

    Science.gov (United States)

    Preto, Nereo; Westphal, Hildegard; Birgel, Daniel; Carampin, Raul; Dal Corso, Jacopo; Gattolin, Giovanni; Montinaro, Alice; Peckmann, Jörn

    2015-04-01

    The earliest Triassic (early Induan) deposits of the Italian Southern Alps are shallow water oolites, and lime-mudstone formed in an open shelf (mid to outer carbonate ramp) sedimentary environment, deposited after the end-Permian extinction that killed all carbonate producers. The origin of these lime-mudstones is thus enigmatic. We used a multidisciplinary petrographic and geochemical approach to identify the origin and early diagenesis of early Triassic lime-mudstones of the Dolomites (Northern Italy). This fine carbonate is made of pitted crystals of microsparite, ~ 25 μm in diameter, exhibiting zonation both in fluorescence and cathodoluminescence. Field and standard petrographic observations exclude an origin from fragmentation or abrasion of carbonate grains. Strontium content, measured in-situ with electron microprobe, has a bimodal distribution with values locally as high as > 4000 ppm. Lipid biomarker analysis revealed molecular fossils of bacteria (terminally-branched alkanes, hopanes, and scarce methylhopanes) along with compounds of low source specificity (n-alkanes), whereas biomarkers of algae (steranes) were not detected. This suggests that, differently from modern Caribbean shelfs, this fine carbonate did not originate from the disgregation of green algae. A Pristane to Phytane ratio < 1 also suggests deposition under anoxic conditions, in agreement with the known status of "superanoxia" of earliest Triassic oceans. Overall, our observations suggest an aragonitic mineralogy of the carbonate mud, followed by calcite replacement and cementation in the marine burial early diagenetic environment. Our data strongly suggest that the early Triassic carbonate mud of the Dolomites was precipitated in the water column, similarly to the modern whitings of the Bahamas, and then settled on a shelf bottom below wave base. Our study shows that these lime-mudstones contain aragonite replaced by calcite and calcite cement, in variable proportions. The δ13C of

  15. A multi-year monitoring project of the high-altitude Cenote ice cave, Dolomites, Italy

    Science.gov (United States)

    Sauro, Francesco; Santagata, Tommaso; Spötl, Christoph; Festi, Daniela; Oeggl, Klaus; Dal Molin, Luca; De Waele, Jo

    2016-04-01

    The Cenote ice cave hosts one of the most voluminous cave glaciers of the Dolomites. This 280 m-deep abyss was discovered in 1994 after the entrance had opened as a result of the abrupt emptying of a small lake at 2940 m a.s.l. in the Regional Park of Fanes, Sennes and Braies. The cave consists of a massive, 130 m-thick layered ice deposit carved by meltwater tunnels and chimneys excavated from below by ascending air. At the lower limit of the cave glacier a shaft opens - ice-free and 165 m deep - leading into a dome occupied by a cave rock glacier with typical terminal tongue embankments. A research project was launched to monitor long-term movements and volume changes of this ice deposit as well as to understand the cave microclimate and the potential for future palaeoclimate studies. During October 2015 a first expedition performed a complete survey of the final chamber using a Leica HDS7000, a phase difference laser scanner equipped with a dual axis compensator, on-board control, a wavelenght of 1.5 microns, a laser "CLASS 1" with a flow rate of 187 m and a resolution of 0.1 mm. A scan station was performed also at 110 m above the bottom of the shaft to map in detail the lower side of the hanging ice glacier. This survey has provided the detailed volume of the chamber (420,000 m3) as well as a first record of the position of the ice masses hanging on the ceiling and of the rock glacier at the bottom. Barometric, temperature and humidity dataloggers have been installed in the cave to record the microclimate. In addition pollen traps have been installed to study the present flux of pollen at the surface and inside the cave, while preliminary analyses on pollen grains preserved in the ice are being carried out. The Cenote ice cave research project aims to shed light on the climate evolution of the Dolomites during the last hundreds or possibly thousands of years, as well as on the more recent environmental changes that lead to the upward melting of the cave

  16. Geology and ground water in Door County, Wisconsin, with emphasis on contamination potential in the Silurian Dolomite

    Science.gov (United States)

    Sherrill, Marvin G.

    1978-01-01

    Door County is in northeastern Wisconsin and is an area of 491 square miles. The county forms the main body of the peninsula between Green Bay and Lake Michigan. The land surface is an upland ridge controlled by the underlying bedrock. The west edge of the ridge forms an escarpment facing Green Bay. Silurian dolomite is the upper bedrock unit throughout most of the county and is the most important aquifer. This bedrock is exposed in much of the county, particularly north of Sturgeon Bay; elsewhere, it is covered by a generally thin mantle of soil or drift. The bedrock units are divided into two major aquifer systems in Door County; the Silurian dolomite aquifer system and the sandstone aquifer system, consisting of Ordovician and Cambrian bedrock units. These two major systems are separated by the Maquoketa Shale of Ordovician age, a nearly impermeable, generally nonproductive unit. The Silurian dolomite aquifer system is itself divided into the Niagaran aquifer and the underlying Alexandrian aquifer. Water occurs in the Silurian dolomite aquifer system in two types of openings-nearly vertical joints (fractures) and horizontal to slightly dipping bedding-plane joints. Vertical joints are more common in the upper part of the Niagaran aquifer. These yield small amounts of water to wells. Bedding-plane joints transmit most of the water in the lower part of the Niagaran aquifer and in the Alexandrian aquifer. The bedding-plane joints, because they are poorly interconnected, act as semiartesian conduits separated by impermeable rock. Eight water-bearing zones in generally continuous bedding-plane joints have been mapped. The dolomite is recharged from direct precipitation and snowmelt. It discharges water to pumping wells and by natural springs discharge to Lake Michigan and Green Bay and to interior lakes and streams. Wells in the Silurian dolomite aquifer system have adequate yields to meet most needs, except in the southwest corner of the county, where the dolomite

  17. Investigation of the role of polysaccharide in the dolomite growth at low temperature by using atomistic simulations

    CERN Document Server

    Shen, Zhizhang; Szlufarska, Izabela; Xu, Huifang

    2016-01-01

    Dehydration of water from surface Mg2+ is most likely the rate-limiting step in the dolomite growth at low temperature. Here, we investigate the role of polysaccharide in this step using classical molecular dynamics (MD) calculations. Free energy (potential of mean force, PMF) calculations have been performed for water molecules leaving the first two hydration layers above the dolomite (104) surface under the following three conditions: without catalyst, with monosaccharide (mannose) and with oligosaccharide (three units of mannose). MD simulations reveal that there is no obvious effect of monosaccharide in lowering the dehydration barrier for surface Mg2+. However, we found that there are metastable configurations of oligosaccharide, which can decrease the dehydration barrier of surface Mg2+ by about 0.7-1.1 kcal/mol. In these configurations, the molecule lies relatively flat on the surface and forms a bridge shape. The hydrophobic space near the surface created by the non-polar -CH groups of the oligosaccha...

  18. Team Member Training Manual.

    Science.gov (United States)

    1998-07-01

    minutes a "facilitator" obtains one idea from each member in turn and writes that idea on a flip chart . No discussion takes place during this step. 4...Step three is repeated until all ideas are listed on the flip chart . 5. Each idea is discussed. Participants seek clarification and express support

  19. Combined high-pressure and high-temperature vibrational studies of dolomite: phase diagram and evidence of a new distorted modification

    Science.gov (United States)

    Efthimiopoulos, I.; Jahn, S.; Kuras, A.; Schade, U.; Koch-Müller, M.

    2017-02-01

    A combined high-pressure mid-infrared absorption and Raman spectroscopy study on a natural CaMg0.98Fe0.02(CO3)2 dolomite sample was performed both at ambient and high temperatures. A pressure-temperature phase diagram was constructed for all the reported dolomite ambient- and high-pressure polymorphs. In addition, a local distortion of the ambient-pressure dolomite structure was identified close to 11 GPa, just before the transition toward the first known high-pressure phase. All the Clausius-Clapeyron slopes are found to be positive with similar magnitudes. Complementary first-principles calculations suggest a metastable nature of the high-pressure dolomite polymorphs. Finally, theoretical spectroscopy is used to interpret and discuss the observed changes in the measured vibrational spectra.

  20. Anthropogenic influences on groundwater in the vicinity of a long-lived radioactive waste repository

    Science.gov (United States)

    Thomas, Matthew A.; Kuhlman, Kristopher L.; Ward, Anderson L.

    2017-07-01

    The groundwater flow system in the Culebra Dolomite Member (Culebra) of the Permian Rustler Formation is a potential radionuclide release pathway from the Waste Isolation Pilot Plant (WIPP), the only deep geological repository for transuranic waste in the United States. In early conceptual models of the Culebra, groundwater levels were not expected to fluctuate markedly, except in response to long-term climatic changes, with response times on the order of hundreds to thousands of years. Recent groundwater pressures measured in monitoring wells record more than 25 m of drawdown. The fluctuations are attributed to pumping activities at a privately-owned well that may be associated with the demand of the Permian Basin hydrocarbon industry for water. The unprecedented magnitude of drawdown provides an opportunity to quantitatively assess the influence of unplanned anthropogenic forcings near the WIPP. Spatially variable realizations of Culebra saturated hydraulic conductivity and storativity were used to develop groundwater flow models to estimate a pumping rate for the private well and investigate its effect on advective transport. Simulated drawdown shows reasonable agreement with observations (average Model Efficiency coefficient = 0.7). Steepened hydraulic gradients associated with the pumping reduce estimates of conservative particle travel times across the domain by one-half and shift the intersection of the average particle track with the compliance boundary by more than two kilometers. The value of the transient simulations conducted for this study lie in their ability to (i) improve understanding of the Culebra groundwater flow system and (ii) challenge the notion of time-invariant land use in the vicinity of the WIPP.

  1. Intake of {sup 226} Ra in osteoporosis prevention and therapy with gran-white dolomite as calcium supplement

    Energy Technology Data Exchange (ETDEWEB)

    Pecequilo, B.R.S.; Campos, M.P. [Instituto de Pesquisas Energeticas e Nucleares (IPEN), Sao Paulo, SP (Brazil)]. E-mails: brigitte@net.ipen.br; mpcampos@net.ipen.br

    2002-04-01

    A {sup 226} Ra average specific activity of 4.3 Bq.kg{sup -1} was determined by passive high resolution gamma-ray spectrometry in six samples of 'Gran White' dolomite. The committed effective dose and committed equivalent dose at bone surface were calculated through the Ana Comp code, using {sup 226} Ra intake and radium metabolic model from ICRP 67. The doses were calculated for patients submitted to osteoporosis prevention and osteoporosis therapy. (author)

  2. Chabazite and dolomite formation in a dolocrete profile: An example of a complex alkaline paragenesis in Lanzarote, Canary Islands

    Science.gov (United States)

    Alonso-Zarza, Ana M.; Bustamante, Leticia; Huerta, Pedro; Rodríguez-Berriguete, Álvaro; Huertas, María José

    2016-05-01

    This paper studies the weathering and soil formation processes operating on detrital sediments containing alkaline volcanic rock fragments of the Mirador del Río dolocrete profile. The profile consists of a lower horizon of removilised weathered basalts, an intermediate red sandy mudstones horizon with irregular carbonate layers and a topmost horizon of amalgamated carbonate layers with root traces. Formation occurred in arid to semiarid climates, giving place to a complex mineralogical association, including Mg-carbonates and chabazite, rarely described in cal/dolocretes profiles. Initial vadose weathering processes occurred in the basalts and in directly overlying detrital sediments, producing (Stage 1) red-smectites and dolomicrite. Dominant phreatic (Stage 2) conditions allowed precipitation of coarse-zoned dolomite and chabazite filling porosities. In Stages 3 and 4, mostly pedogenic, biogenic processes played an important role in dolomite and calcite accumulation in the profile. Overall evolution of the profile and its mineralogical association involved initial processes dominated by alteration of host rock, to provide silica and Mg-rich alkaline waters, suitable for chabazite and dolomite formation, without a previous carbonate phase. Dolomite formed both abiogenically and biogenically, but without a previous carbonate precursor and in the absence of evaporites. Dominance of calcite towards the profile top is the result of Mg/Ca decrease in the interstitial meteoric waters due to decreased supply of Mg from weathering, and increased supply of Ca in aeolian dust. Meteoric origin of the water is confirmed by C and O isotope values, which also indicate lack of deep sourced CO2. The dolocrete studied and its complex mineral association reveal the complex interactions that occur at surface during weathering and pedogenesis of basalt-sourced rocks.

  3. Fault-related dolomitization in the Orpesa Ranges (Iberian Chain, E Spain): reactive transport simulations and field data constraints

    Science.gov (United States)

    Gomez-Rivas, E.; Martin-Martin, J. D.; Corbella, M.; Teixell, A.

    2009-04-01

    The relationships between hydrothermal fluid circulation and fracturing that lead to mineral dissolution and/or precipitation in carbonate rocks have direct impacts on the evolution and final distribution of hydrocarbon reservoir permeability. Understanding the coupling between these processes is important for predicting permeability and improving hydrocarbon recovery. We present a case study of dolomitization processes in Cretaceous limestone from the Orpesa Ranges (Iberian Chain, E Spain). Extending over part of the Maestrat Cretaceous Basin, the Orpesa area is deformed by extensional faults. These faults accommodated thick sequences of shallow marine limestone, mainly during Aptian times. The syn-rift carbonates are partially dolomitized due to the circulation and mixing of hydrothermal fluids along normal faults and bedding. Both Aptian and later Neogene extensional faults must have served as conduits for the circulation of fluids. MVT deposits of Paleocene age are well documented in the Maestrat basin and may also be related to dolomitization. Samples of host rocks and vein fillings have been collected along strike and analyzed in different fault sections to characterize fluid and rock composition, track flow pathways and map the relationships of fluid flow with respect to the main normal faults in the area. Using field and geochemical data from the Orpesa Ranges carbonates, we have developed reactive-transport models to study the influence of different parameters in the dolomitization of carbonates related to the circulation and mixing of hydrothermal fluids at the outcrop scale. We present results from models that were run with constant and non-constant permeability. The main parameters analyzed include: initial porosity and permeability of layers and fractures, composition of fluids, groundwater and brines flux, composition of layers, reactive surface of minerals, differences in vertical and horizontal permeability, and presence or absence of stratigraphic

  4. Dolomitized bryozoan bioherms from the Lower Silurian Manitoulin Formation, Bruce Peninsula, Ontario

    Energy Technology Data Exchange (ETDEWEB)

    Anastas, A.S.; Coniglo, M. (Waterloo Univ., ON (Canada))

    1992-06-01

    Several small, previously undescribed bioherms are present in the shallow shelf dolostones of the Manitoulin Formation at the Cabot Head and Wingfield Basin localities in the northernmost portion of the Bruce Peninsula region of southern Ontario. The bioherms, commonly associated with carbonate tempestites, range from 0.3 to 1.0 m in height and 0.9 to 2.5 m in width and are composed of bafflestones-floatstones and minor bindstones. The chief components of the bioherms are dolomitized lime mud and branching bryozoans. Bioherm building by bryozoans, although common in the ancient record, represents a great divergence from the mostly accessory frame encrusting role of bryozoans in modern environments. Minor skeletal components of the bioherms include echinoderms, rugose and tabulate corals and brachiopods. Laminar encrusting bryozoans exist in the top 10 cm of one of the bioherms. Some of the bioherms show evidence of water agitation that may be the result of current action induced by storm or tidal processes. The occurrence of the bioherms stretches the already known Llandoverian reef complex on Manitoulin Island further to the south. The reason why these bioherms did not reach sizes comparable to large Llandoverian or Wenlockian reefs and did not make the shift to coral-stromaporoid community is probably related to a complex interaction of factors such as community development, bathymetry, clasticity and salinity. 41 refs., 4 figs.

  5. Distribution and diagenesis of microfossils from the lower Proterozoic Duck Creek Dolomite, Western Australia

    Science.gov (United States)

    Knoll, A. H.; Strother, P. K.; Rossi, S.

    1988-01-01

    Two distinct generations of microfossils occur in silicified carbonates from a previously undescribed locality of the Lower Proterozoic Duck Creek Dolomite, Western Australia. The earlier generation occurs in discrete organic-rich clasts and clots characterized by microquartz anhedra; it contains a variety of filamentous and coccoidal fossils in varying states of preservation. Second generation microfossils consist almost exclusively of well-preserved Gunflintia minuta filaments that drape clasts or appear to float in clear chalcedony. These filaments appear to represent an ecologically distinct assemblage that colonized a substrate containing the partially degraded remains of the first generation community. The two assemblages differ significantly in taxonomic frequency distribution from previously described Duck Creek florules. Taken together, Duck Creek microfossils exhibit a range of assemblage variability comparable to that found in other Lower Proterozoic iron formations and ferruginous carbonates. With increasing severity of post-mortem alteration, Duck Creek microfossils appear to converge morphologically on assemblages of simple microstructures described from early Archean cherts. Two new species are described: Oscillatoriopsis majuscula and O. cuboides; the former is among the largest septate filamentous fossils described from any Proterozoic formation.

  6. Use of dolomite phosphate rock (DPR) fertilizers to reduce phosphorus leaching from sandy soil.

    Science.gov (United States)

    Chen, G C; He, Z L; Stoffella, P J; Yang, X E; Yu, S; Calvert, D

    2006-01-01

    There is increasing concern over P leaching from sandy soils applied with water-soluble P fertilizers. Laboratory column leaching experiments were conducted to evaluate P leaching from a typical acidic sandy soil in Florida amended with DPR fertilizers developed from dolomite phosphate rock (DPR) and N-Viro soil. Ten leaching events were carried out at an interval of 7 days, with a total leaching volume of 1,183 mm equivalent to the mean annual rainfall of this region during the period of 2001-2003. Leachates were collected and analyzed for total P and inorganic P. Phosphorus in the leachate was dominantly reactive, accounting for 67.7-99.9% of total P leached. Phosphorus leaching loss mainly occurred in the first three leaching events, accounting for 62.0-98.8% of the total P leached over the whole period. The percentage of P leached (in the total P added) from the soil amended with water-soluble P fertilizer was higher than those receiving the DPR fertilizers. The former was up to 96.6%, whereas the latter ranged from 0.3% to 3.8%. These results indicate that the use of N-Viro-based DPR fertilizers can reduce P leaching from sandy soils.

  7. Infrared and ultraviolet laser removal of crustose lichens on dolomite heritage stone

    Energy Technology Data Exchange (ETDEWEB)

    Sanz, Mikel; Oujja, Mohamed [Instituto de Química Física Rocasolano (IQFR), CSIC, Serrano 119, 28006 Madrid (Spain); Ascaso, Carmen; Ríos, Asunción de los; Pérez-Ortega, Sergio [Museo Nacional de Ciencia Naturales (MNCN), CSIC, Serrano 115 bis, 28006 Madrid (Spain); Souza-Egipsy, Virginia [Instituto de Ciencias Agrarias (ICA), CSIC, Serrano 115 bis, 28006 Madrid (Spain); Wierzchos, Jacek; Speranza, Mariela [Museo Nacional de Ciencia Naturales (MNCN), CSIC, Serrano 115 bis, 28006 Madrid (Spain); Cañamares, Maria Vega [Instituto de Estructura de la Materia (ICEM), CSIC, Serrano 121, 28006 Madrid (Spain); Castillejo, Marta, E-mail: marta.castillejo@iqfr.csic.es [Instituto de Química Física Rocasolano (IQFR), CSIC, Serrano 119, 28006 Madrid (Spain)

    2015-08-15

    Graphical abstract: - Highlights: • Laser irradiation at 1064 nm (IR) or 355 nm (UV) partially removes epilithic lichens on dolostone. • Irradiation in a sequential, dual IR–UV mode efficiently eliminates lichen thalli. • Dual IR–UV irradiation mode induces severe damage on endolithic colonizers of dolostone. - Abstract: Laser removal of biodeteriogen layers warrants detailed studies due to the advantages it brings with respect to mechanical elimination or the use of biocides. We have investigated elimination of biological crusts on dolomite stones from heritage sites in central Spain. The samples were colonized by epilithic crustose lichens of different species, such as Caloplaca sp. and Verrucaria nigrescens. A comparative study was carried out by applying infrared (1064 nm) and ultraviolet (355 nm) nanosecond laser pulses and sequences pulses of the two wavelengths using a Q-switched Nd:YAG system. To detect anatomical and ultrastructural damage to the lichens, and to assess possible morphological and chemical changes on the underlying stone induced by laser irradiation, we used stereomicroscopy, scanning electron microscopy with backscattered electron imaging and Fourier transform Raman spectroscopy. The optimal conditions for removal of the colonization crust, while ensuring preservation of the lithic substrate, were obtained for dual infrared-ultraviolet sequential irradiation.

  8. LITHOSTRATIGRAPHY AND FACIES ARCHITECTURE OF THE OLIGOCENE CONGLOMERATES AT MONTE PAREI (FANES. DOLOMITES, ITALY

    Directory of Open Access Journals (Sweden)

    LORENZ KEIM

    2000-03-01

    Full Text Available The only occurrence of Tertiary (Oligocene sediments in the Dolomites at Monte Parei results from a complex tectonic and sedimentary history. The Tertiary marine clastic succession is sealing the Dinaric (Late Cretaceous to Paleogene deformed basement. The basin-fill can be differentiated into four lithofacies which show extensive lateral interfingering: ,local scarp breccias with giant blocks (facies A, chaotic breccias of debris flow origin (facies B, balanid and shell coquina beds (facies C and conglomeratic grain and debris flows with sandstone intercalations (facies D. Transport directions (imbricate clasts and cross bedding and petrographic composition indicate two different source areas. Sediments of facies B were shed from a structural high in the SW, while carbonate-siliciclastic debris of facies C and D originated from a pebbly or rocky shore in the N. Lithofacies and facies interrelationships clearly indicate the control by synsedimentary tectonic activity. Neoalpine closure of the basin by overthrusting lead to the preservation of the sediments. 

  9. Oxygen isotope geochemistry of phosphorite and dolomite and palaeo-ocean temperature estimation:A case study from the Neoproterozoic Doushantuo Formation,Guizhou Province,South China

    Institute of Scientific and Technical Information of China (English)

    LING Hongfei; JIANG Shaoyong; FENG Hongzhen; CHEN Yongquan; CHEN Jianhua; YANG Jinghong

    2004-01-01

    The Neoproterozoic Doushantuo Formation at Weng'an in Guizhou Province of South China consists of phosphorites and dolomites.Three types of samples are recongnized for the phosphate-bearing rocks.In Type I samples, interstitial phosphates occur within the dolomite rocks, whereas in Type III samples, interstitial dolomites occur within the phosphorites; both of them may have diagenetic origin.The Type II samples are interbedded phosphorites and dolomites.Oxygen isotopic compositions of phosphate and coeval carbonate were analyzed.Phosphates of Type I and II samples show similar low δ18Ophos (SMOW) values of 10.9‰~12.1‰ and 10.7‰~12.8‰, respectively, whereas Type III phosphates show higher δ18Ophos (SMOW) values of 13.2‰~15.0‰.Dolomites from Type I and II samples have δ18Ocarb (PDB) and δ13Ccarb (PDB) values of -6.2‰~-3.4‰ and -2.2‰~-0.7‰, respectively, whereas interstitial dolomites from Type III samples show lower δ18Ocarb (PDB) and δ13Ccarb (PDB) values of -12.9‰~-8.6‰ and -4.4‰~-2.6‰.Petrology and oxygen isotope data suggest that diagenetic alteration may have partially affected the studied rocks, but the dolomites from Type I and phosphates from Type III samples represent the most pristine isotopic compositions of primary carbonates and phosphates precipitated from seawater.Calculations of palaeocean temperatures from the most 18O enriched dolomite and phosphate indicate a temperature range of 32.2 ℃ to 34.0 ℃ for the seawater of the Doushantuo Formation period.Ce anomaly also suggests more oxic conditions and possibly shallower water depth in the upper strata of the Doushantuo Formation at Weng'an, Guizhou Province.

  10. Diagenesis and application of LiDAR in reservoir analogue studies: karstification in the Cretaceous Apulia carbonate platform dolomitization in the Triassic Latemar carbonate buildup

    OpenAIRE

    Jacquemyn, Carl

    2013-01-01

    The ever-increasing demand for energy and hydrocarbons coincides with gradual depletion of currently producing conventional oil and gas reservoirs. Therefore new exploration plays are extended to more complex oil and gas plays, such as karstified limestones and hydrothermal dolomites. Furthermore production from currently producing reservoirs is optimized by revisiting or improving the geological knowledge of these reservoirs. These two perspectives are covered in this study on dolomitization...

  11. Whole-catchment application of dolomite to mitigate episodic acidification of streams induced by sea-salt deposition.

    Science.gov (United States)

    Hindar, Atle

    2005-05-01

    To counteract mobilisation of potentially toxic aluminium (Al) ions to tributaries of salmon rivers, two paired-catchment experiments with terrestrial liming at two sites on the Norwegian west coast were performed. Streams at both sites experienced episodically elevated and potentially toxic Al levels induced by high deposition of sea salts. After application of 2 metric tons ha-1 of 0.2-2 mm dolomite powder at the Brommeland area, stream pH increased above critical levels at about pH=6.0 and remained stable throughout the monitoring period of 3.5 years. Inorganic aluminium decreased to below 20 microg Al L-1, a water quality supposed to be nontoxic for salmon. This was evident also during extreme weather conditions with large relative increases in chloride (Cl) concentrations and negative calculated nonmarine sodium (Na*) concentrations in the streams, indicating potentially toxic sea-salt effects. Cl changed from being closely related to increases in inorganic Al, especially at the Brommeland stream (R2=0.75), to being not important (R2=0.12), but still significant for its variation. At the Hovland area, receiving 1 ton ha-1 of 0-2 mm dolomite powder, stream pH and Al effects were less clear-cut, probably due to the lower dolomite dose. Stream concentrations of both NO3- and SO4(2-) increased significantly due to liming.

  12. THE ANISIAN MACROFLORA FROM THE NORTHERN DOLOMITES (KÜHWIESENKOPF/ MONTE PRÀ DELLA VACCA, BRAIES: A FIRST REPORT

    Directory of Open Access Journals (Sweden)

    CARMEN BROGLIO LORIGA

    2002-11-01

    Full Text Available The knowledge of Triassic macroflora from the Dolomites mostly concerns the Ladinian, while literature data on Anisian plants are scarce. This gap is filled by the discovery, reported here, of a rich plant deposit from Kühwiesenkopf / Monte Prà della Vacca (Prags/Braies Dolomites. The fossils occur in a horizon, about 1 m thick, from the lower part of the Dont Formation, a basinal unit mostly constituted by hemipelagic, terrigenous-carbonatic sediments of Pelsonian - Illyrian age. The stratigrafic interval with the plant horizon is Pelsonian in age. A preliminary systematic analysis of the numerous and well preserved specimens has allowed the identification of at least 17 genera. The taxa belong primarily to the Pteridophyta (Anomopteris, Neuropteridium, Cladophlebis, Crematopteris, ?Marattiopsis, subordinately to the Cycadophyta (Bjuvia, Taeniopteris, Dioonitocarpidium, Pterophyllum / Nilssonia. Coniferophyta are represented by Voltzia, ?Voltzia and Albertia; the latter genus is recorded herein for the first time in the Middle Triassic of the Dolomites. Besides, two Lycophyta genera (?Isoetites, Lycophyta new taxon, three Pteridospermae genera (?Sagenopteris, Scytophyllum and Peltaspermum, and one Sphenophyta genus (Equisetites have also been recognized.   

  13. Modified dolomite in biomass gasification with simultaneous tar reformation and CO2 capture: effect of metal loading

    Science.gov (United States)

    Di Felice, L.; Courson, C.; Foscolo, P. U.; Kiennemann, A.

    2011-03-01

    The CO2 absorption capacity of calcined dolomite [a (CaMg)O solid solution] doped with iron and nickel transition metals has been investigated in a fixed bed reactor operating at temperature conditions (650°C) at which the sorption process is thermodynamically favoured at ambient pressure. The presence of metals (catalytic sites) between CaO grains (CO2 absorption sites) may improve the potential of dolomite for the simultaneous process of catalytic tar reforming and CO2 capture in biomass gasification, with the aim of developing an effective combined catalyst and sorbent particle. It was found that iron and nickel may be optimised in the substrate reducing critical limitations on CO2 capture capacity. A Sorption Enhanced Reforming test is proposed, at 650°C, for both iron and nickel doped calcined dolomite, using toluene as model tar compound: iron has been found to be not active in such conditions, whereas the 4% Ni/(CaMg)O has been indicated as the most suitable combined catalyst and sorbent particle.

  14. Basic Data Report for Drillhole SNL-2 (C-2948)

    Energy Technology Data Exchange (ETDEWEB)

    Powers, Dennis W. [Washington Regulatory and Environmental Services (United States)

    2005-01-19

    SNL-2 was drilled in the northwest quarter of Section 12, T22S, R30E, in eastern Eddy County, New Mexico (Figure 2-1). It is located 574 ft from the north line (fnl) and 859 ft from the west line (fwl) of the section (Figure 2-2). This location places the drillhole east of the Livingston Ridge escarpment among oil wells of the Cabin Lake field. SNL-2 will be used to test hydraulic properties and to monitor ground water levels of the Culebra Dolomite Member of the Permian Rustler Formation. SNL-2 was permitted by the New Mexico State Engineer as C-2948. [Official correspondence regarding permitting and regulatory information must reference this permit number.] In the plan describing the integrated groundwater hydrology program (Sandia National Laboratories, 2003), SNL-2 is also codesignated WTS-1 because the location also satisfies needs for long-term monitoring of water quality and movement in the Culebra Dolomite for RCRA permitting; this program is under the management of Washington TRU Solutions LLC (WTS). In the event that additional wells are established on the SNL-2 drillpad to monitor other hydrological units (e.g., the Magenta Dolomite Member of the Permian Rustler Formation), the current drillhole will likely be referred to as SNL-2C because it is completed in the Culebra. Most drillholes at WIPP have been described after completion to provide an account of the geology, hydrology, or other basic data acquired during drilling and immediate completion of the drillhole. In addition, the basic data report provides an account of the drilling procedures and activities that may be helpful to later interpretations of data or for further work in the drillhole, including test activities and eventual plugging and abandoning activities. The basic data report also provides a convenient means of reporting information about administrative activities necessary to drill the hole.

  15. 塔里木盆地塔中地区下奥陶统白云岩成因%Genesis of Lower Ordovician Dolomite in Central Tarim Basin

    Institute of Scientific and Technical Information of China (English)

    李鹏春; 陈广浩; 曾乔松; 易金; 胡罡

    2011-01-01

    塔里木盆地塔中地区下奥陶统白云岩广泛发育,岩石类型复杂多样,主要包括结晶白云岩、残余颗粒白云岩、残余灰质白云岩、藻云岩、亮边雾心白云岩、环带白云岩及少量膏云岩等结构类型。白云岩交代现象明显,δ18O普遍为中—高负值(-3.2‰~-8.7‰);δ13C值基本为低中负值(-3‰~-0.77‰),Z值大多集中在118~123之间,成岩温度大部分集中于36~51℃范围,属于低温白云岩。白云岩具有低Mg/Ca比值,而Fe/Mn比值变化较大;白云石成分显示高铁白云石和低铁白云石之分;Sr同位素组成(0.708 8~0.709 7)普遍与海水锶同位素组成相当,但也存在个别具有较高的87Sr/86Sr比值(0.710 1~0.710 9)。结合塔中地区奥陶系古地理演变特征,白云岩化类型可划分为准同生期白云石化作用和埋藏白云石化作用。准同生期白云石化作用发生于海底(主要是潮间)成岩环境,主要是在潮坪环境或滩相环境中,其白云岩形成温度较低,具低87Sr/86Sr比值,白云石单矿物具低Fe含量;而埋藏白云岩化存在两种模式,一种为早期浅埋藏过程中的卤水回流模式,其白云岩形成温度亦较低,具高87Sr/86Sr比值,白云石单矿物具高Fe含量;另一类发生于还原性较强晚期埋藏较深的成岩环境,在埋藏阶段白云岩化程度得到进一步加强和调整,其白云岩形成温度较高,白云石捕获的包裹体均一温度较高,盐度较低。%Lower Ordovician dolomites in the central Tarim basin are of various types and extensively distributed.Seven dolostone types could be documented based on fabrics and structures,which are crystalline dolomite,residual-grain dolomite,residual calcite dolomite,algal dolomite,cloudy centers and clear rims dolomite,clitellum dolomite and gypes dolomite.It’s characterised by middle-high δ18O negative value(-3.2%~-8.7‰),low-middle δ13C negative value(-3%~-0.77

  16. Comparison of clumped isotope signatures of dolomite cements to fluid inclusion thermometry in the temperature range of 73-176 °C

    Science.gov (United States)

    Came, Rosemarie E.; Azmy, Karem; Tripati, Aradhna; Olanipekun, Babatunde-John

    2017-02-01

    Widespread application of the novel clumped isotope paleothermometer (Δ47) using dolomite samples from shallow crustal settings has been hindered by a lack of adequate constraints on clumped isotope systematics in dolomites that formed at temperatures greater than 50 °C. Consequently, many high-temperature applications involving diagenetic dolomites have required an assumption that the relationship between temperature and Δ47 in diagenetic dolomite resembles the theoretical temperature dependence for calcite. Here we present Δ47 results from dolomite cements for which precipitation temperatures were determined independently using fluid inclusion microthermometry. We compare a rock-based ;calibration; for samples from the temperature range of ∼73 to 176 °C to previously published laboratory-derived calibrations for synthetic calcites. This novel combination of approaches yields results that are broadly consistent with results reported from controlled laboratory experiments, providing an important confirmation of the utility of clumped isotopes in real-world systems. Our results suggest that the Δ47 of dolomite cements may provide key information in the reconstruction of burial and thermal histories and also in the recognition of potential petroleum reservoirs.

  17. Offers for our members

    CERN Multimedia

    Staff Association

    2017-01-01

    Summer is coming, enjoy our offers for the aquatic parcs! Walibi : Tickets "Zone terrestre": 24 € instead of 30 €. Access to Aqualibi: 5 € instead of 6 € on presentation of your SA member ticket. Free for children under 100 cm. Car park free. * * * * * Aquaparc : Day ticket: – Children: 33 CHF instead of 39 CHF – Adults : 33 CHF instead of 49 CHF Bonus! Free for children under 5.

  18. Offers for our members

    CERN Multimedia

    Staff Association

    2017-01-01

    Summer is here, enjoy our offers for the aquatic parcs! Walibi : Tickets "Zone terrestre": 24 € instead of 30 €. Access to Aqualibi: 5 € instead of 6 € on presentation of your SA member ticket. Free for children under 100 cm. Car park free. * * * * * Aquaparc : Day ticket: – Children: 33 CHF instead of 39 CHF – Adults : 33 CHF instead of 49 CHF Bonus! Free for children under 5.

  19. [Comment on] BOSP members

    Science.gov (United States)

    Richman, Barbara T.

    The new Board on Ocean Science and Policy (BOSP) (Eos, June 7, 1983, p. 402) met for the first time on May 4. John B. Slaughter, former director of the National Science Foundation and now chancellor of the University of Maryland in College Park, is the board's chairman. Other board members are D. James Baker, Jr. (University of Washington, Seattle); Kirk Bryan (Geophysical Fluid Dynamics Laboratory, Princeton University); John P. Craven (University of Hawaii); Charles L. Drake (Dartmouth College); Paul M. Fye (Woods Hole Oceanographic Institution); Edward D. Goldberg (Scripps Institution of Oceanography); G. Ross Heath (Oregon State University); Judith T. Kildow (Massachusetts Institute of Technology); John A. Knauss (University of Rhode Island); James J. McCarthy (Museum of Comparative Zoology, Harvard University); H. William Menard (Scripps Institution of Oceanography); C. Barry Raleigh (Lamont-Doherty Geological Observatory); Roger Revelle (University of California, San Diego); David A. Ross (Woods Hole Oceanographic Institution); Brian J. Rothschild (University of Maryland); William M. Sackett (University of South Florida); John H. Steele (Woods Hole Oceanographic Institution); and Carl Wunsch (MIT). Wallace Broecker (Lamont-Doherty Geological Observatory), an original board member, resigned after the first meeting. Broecker told Eos that combining the science and policy boards resulted in a new board whose mission is too broad. A new board member will be appointed in Broecker's place

  20. Basic data report for drilling and hydrologic testing of drillhole DOE-2 at the Waste Isolation Pilot Plant (WIIP) site

    Energy Technology Data Exchange (ETDEWEB)

    Mercer, J.W.; Beauheim, R.L.; Snyder, R.P.; Fairer, G.M.

    1987-04-01

    Drillhole DOE-2 was drilled to investigate a structural depression marked by the downward displacement of stratigraphic markers in the Salado Formation. Contrary to several hypotheses, halite layers were thicker in the lower part of the Salado, not thinner as a result of any removal of halite. The upper Castile anhydrite in Drillhole DOE-2 is anomalously thick and is strongly deformed relative to the anhydrite in adjacent drillholes. In contrast, the halite was <8 ft thick and significantly thinner than usually encountered. The lower Castile anhydrite appears to be normal. The depression within the correlated marker beds in the Salado Formation in Drillhole DOE-2 is interpreted as a result of gravity-driven deformation of the underlying Castile Formation. Several stratigraphic units were hydrologically tested in Drillhole DOE-2. Testing of the unsaturated lower portion of the Dewey Lake Red Beds was unsuccessful because of exceptionally small rates of fluid intake. Drill-stem tests were conducted in five intervals in the Rustler Formation, over the Marker Bed 138-139 interval in the Salado formation, and over three sandstone members of the Bell Canyon Formation. A pumping test was conducted in the Culebra Dolomite Member of the Rustler Formation. Pressure-pulse tests were conducted over the entire Salado Formation. Fluid samples were collected from the Culebra Dolomite Member and from the Hays Member of the Bell Canyon Formation. 31 refs., 31 figs., 5 tabs.

  1. 3D modelling of a dolomitized syn-sedimentary structure: an exhumed potential analogue of hydrocarbon reservoir.

    Science.gov (United States)

    Martinelli, Mattia; Franceschi, Marco; Massironi, Matteo; Bistacchi, Andrea; Di Cuia, Raffaele; Rizzi, Alessandro

    2016-04-01

    The decrease in discoveries of new hydrocarbon reservoirs has twofold implications: i) the need to improve our knowledge of classic reservoirs, such as traps within extensional syn-sedimentary structures, and ii) enhanced efforts aimed at better understanding complex type of reservoirs. In particular, in the last few years, fault related dolomitized bodies, often associated to extensional faults, received worldwide attention thanks to the capability of dolomitizing fluids to improve the pore network. However, the shape and geometries of the dolomitized bodies within complex fault network as well as the related porosity distribution and evolution is difficult to predict. The study of outcrop analogues can help to solve these issues. In this work, we focused our attention on the Early Jurassic carbonate sediments of the Calcari Grigi Group deposited on the Trento Platform (Italian Southern Alps). The stratigraphic succession encompasses (from bottom to top): the peritidal limestones of the Monte Zugna Formation, the initially highly porous Loppio Oolitic Limestone and the nearly tight marls and marly limestones of the lower Rotzo Formation. During Early Jurassic, after the deposition of the Loppio Oolitic Limestone, the Trento Platform underwent syn-sedimentary extensional tectonics, which caused the formation of numerous tilted blocks. Differential subsidence of these blocks is testified by abrupt thickness changes in Rotzo Formation. This created a structural framework favourable to the formation of syn-sedimentary extensional traps (with the Loppio Oolitic Limestone as reservoir and Rotzo Formation as seal). In the Tertiary, Alpine compressional tectonics caused the reactivation of the Jurassic faults with a strike slip kinematics and was associated with the circulation of dolomitizing fluids. The combination of these events led to the formation of secondary fault-related dolomitized bodies. The enhanced pore network in correspondence of the dolomitized dykes

  2. Muddy and dolomitic rip-up clasts in Triassic fluvial sandstones: Origin and impact on potential reservoir properties (Argana Basin, Morocco)

    Science.gov (United States)

    Henares, Saturnina; Arribas, Jose; Cultrone, Giuseppe; Viseras, Cesar

    2016-06-01

    The significance of rip-up clasts as sandstone framework grains is frequently neglected in the literature being considered as accessory components in bulk sandstone composition. However, this study highlights the great value of muddy and dolomitic rip-up clast occurrence as: (a) information source about low preservation potential from floodplain deposits and (b) key element controlling host sandstone diagenetic evolution and thus ultimate reservoir quality. High-resolution petrographic analysis on Triassic fluvial sandstones from Argana Basin (T6 and T7/T8 units) highlights the significance of different types of rip-up clasts as intrabasinal framework components of continental sediments from arid climates. On the basis of their composition and ductility, three main types are distinguished: (a) muddy rip-up clasts, (b) dolomitic muddy rip-up clasts and (c) dolomite crystalline rip-up clasts. Spatial distribution of different types is strongly facies-related according to grain size. Origin of rip-up clasts is related to erosion of coeval phreatic dolocretes, in different development stages, and associated muddy floodplain sediments. Cloudy cores with abundant inclusions and clear outer rims of dolomite crystals suggest a first replacive and a subsequent displacive growth, respectively. Dolomite crystals are almost stoichiometric. This composition is very similar to that of early sandstone dolomite cement, supporting phreatic dolocretes as dolomite origin in both situations. Sandstone diagenesis is dominated by mechanical compaction and dolomite cementation. A direct correlation exists between: (1) muddy rip-up clast abundance and early reduction of primary porosity by compaction with irreversible loss of intergranular volume (IGV); and (2) occurrence of dolomitic rip-up clasts and dolomite cement nucleation in host sandstone, occluding adjacent pores but preserving IGV. Both processes affect reservoir quality by generation of vertical and 3D fluid flow baffles and

  3. Wood ash or dolomite treatment of catchment areas - effects of mercury in runoff water

    Energy Technology Data Exchange (ETDEWEB)

    Parkman, H.; Munthe, J. [Swedish Environmental Research Inst., Stockholm (Sweden)

    1996-11-01

    A future increased use of biomass as a source of energy, and the planned restoration of mineral nutrient balance in the forest soils by returning the wood ashes, has led to concern for new environmental disturbances. The objectives of the present study were to investigate if the outflow of total mercury (TotHg) and methyl mercury (MeHg) from catchment areas treated with granulated wood ash (1988, 2.2 tons/ha, `ashed area`) or dolomite (1985, 5 tons/ha, `limed area`) differed from the outflow from an untreated (reference) area, and if variations in Hg outflow were correlated with changes in the outflow of organic substances or pH. The study areas are situated in Vaermland, Sweden. Samples of run-off water were taken weekly or monthly (depending on water-flow) during on year (1993-94). The outflow of MeHg, TotHg as well as H+ and dissolved organic material (DOC) was lower from the limed area compared to the other two areas, which did not differ significantly. There was a strong covariation between concentrations of DOC and MeHg and a weaker relation between DOC and TotHg in the run-off waters. MeHg also covaried with temperature while TotHg covaried with pH and water-supply. No difference was found when comparing Hg-data from the limed area before, directly after and eight years after the liming event. 13 refs, 12 figs, 1 tab

  4. Norovirus outbreak caused by a new septic system in a dolomite aquifer.

    Science.gov (United States)

    Borchardt, Mark A; Bradbury, Kenneth R; Alexander, E Calvin; Kolberg, Rhonda J; Alexander, Scott C; Archer, John R; Braatz, Laurel A; Forest, Brian M; Green, Jeffrey A; Spencer, Susan K

    2011-01-01

    Septic systems that are built in compliance with regulations are generally not expected to be the cause of groundwater borne disease outbreaks, especially in areas with thick vadose zones. However, this case study demonstrates that a disease outbreak can occur in such a setting and outlines the combination of epidemiological, microbiological, and hydrogeological methods used to confirm the source of the outbreak. In early June 2007, 229 patrons and employees of a new restaurant in northeastern Wisconsin were affected by acute gastroenteritis; 6 people were hospitalized. Epidemiological case-control analysis indicated that drinking the restaurant's well water was associated with illness (odds ratio = 3.2, 95% confidence interval = 0.9 to 11.4, P = 0.06). Microbiological analysis (quantitative reverse transcription-polymerase chain reaction) measured 50 genomic copies per liter of norovirus genogroup I in the well water. Nucleotide sequencing determined the genotype as GI.2 and further showed the identical virus was present in patrons' stool specimens and in the septic tank. Tracer tests using dyes injected at two points in the septic system showed that effluent was traveling from the tanks (through a leaking fitting) and infiltration field to the well in 6 and 15 d, respectively. The restaurant septic system and well (85-m deep, in a fractured dolomite aquifer) both conformed to state building codes. The early arrival of dye in the well, which was 188 m from the septic field and located beneath a 35-m thick vadose zone, demonstrates that in highly vulnerable hydrogeological settings, compliance with regulations may not provide adequate protection from fecal pathogens.

  5. Effects of Dolomitic Limestone Application on Zinc Speciation in Boreal Forest Smelter-Contaminated Soils.

    Science.gov (United States)

    Hamilton, Jordan G; Farrell, Richard E; Chen, Ning; Reid, Joel; Feng, Renfei; Peak, Derek

    2016-11-01

    Anthropogenic activities at the HudBay Minerals, Inc., Flin Flon (Manitoba, Canada) mining and processing facility have severely affected the surrounding boreal forest ecosystem. Soil contamination occurred via a combination of metal and sulfuric acid deposition and has resulted in forest dieback and ineffective natural recovery. A community-led effort to revegetate areas of the landscape through the application of a dolomitic limestone has been met with varied success. Zinc (Zn) speciation has shown to be closely linked to the presence or absence of an invasive metal-tolerant grass species, with soils being broadly classed into two revegetation response groups. Group I, characterized by the absence of metal-tolerant grasses, and group II, characterized by the presence of metal-tolerant grasses. The systematic approach used to lime areas of the landscape produced a liming chronosequence for each group. This study used a combination of X-ray absorption spectroscopy, X-ray fluorescence mapping, and X-ray diffraction techniques to determine the effect of liming on Zn speciation in these chronosequences. Liming group I soils resulted in the formation of a neo-phase Zn-Al-hydroxy interlayer coprecipitate and subsequent rapid boreal forest revegetation. The effect of liming on Zn speciation on the group II soils resulted in a gradual transition of increasingly stable adsorption species, culminating with a stable Zn-Al-layered double hydroxide precipitate. Boreal forest vegetation has failed to recolonize group II soils during the study. However, the formation of the layered double hydroxide species resulted in a significant reduction in CaCl-extractable Zn. Further research is required to determine how to promote the revegetation of these soils. Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.

  6. Debris flow monitoring in the Acquabona watershed on the Dolomites (Italian Alps)

    Science.gov (United States)

    Berti, M.; Genevois, R.; LaHusen, R.; Simoni, A.; Tecca, P.R.

    2000-01-01

    In 1997 a field monitoring system was installed in Acquabona Creek in the Dolomites (Eastern Italian Alps) to observe the hydrologic conditions for debris flow occurrence and some dynamic properties of debris flow. The monitoring system consists of three remote stations: an upper one located at the head of a deeply-incised channel and two others located downstream. The system is equipped with sensors for measuring rainfall, pore pressures in the mobile channel bottom, ground vibrations, debris flow depth, total normal stress and fluid pore-pressure at the base of the flow. Two video cameras record events at the upper channel station and one video is installed at the lowermost station. During summer 1998, three debris flows (volumes from less than 1000 m3 up to 9000 m3) occurred at Acquabona. The following results were obtained from a preliminary analysis of the data: 1) All of the flows were triggered by rainfalls of less than 1 hour duration, with peak rainfall intensities ranging from 4.8 to 14.7 mm / 10 minute. 2) Debris flows initiated in several reaches of the channel, including the head of the talus slope. 3) The initial surges of the mature flows had a higher solid concentration and a lower velocity (up to 4 m/s) than succeeding, more dilute surges (more than 7 m/s). 4) Total normal stress and pore fluid pressures measured at the base of the flow (mean depth about 1.1 m) were similar (about 15 kPa), indicating a completely liquefied flow. 5) Peak flows entrained debris at a rate of about 6 m3/m of channel length and channel bed scouring was proportional to the local slope gradient and was still evident in the lower channel where the slope was 7??. ?? 2000 Elsevier Science Ltd. All rights reserved.

  7. Modeling four occurred debris flow events in the Dolomites area (North-Eastern Italian Alps)

    Science.gov (United States)

    Boreggio, Mauro; Gregoretti, Carlo; Degetto, Massimo; Bernard, Martino

    2016-04-01

    Four occurred debris flows in the Dolomites area (North-Eastern Italian Alps) are modeled by back-analysis. The four debris flows events are those occurred at Rio Lazer (Trento) on the 4th of November 1966, at Fiames (Belluno) on the 5th of July 2006, at Rovina di Cancia (Belluno) on the 18th of July 2009 and at Rio Val Molinara (Trento) on the 15th of August 2010. In all the events, runoff entrained sediments present on natural channels and formed a solid-liquid wave that routed downstream. The first event concerns the routing of debris flow on an inhabited fan. The second event the deviation of debris flow from the usual path due to an obstruction with the excavation of a channel in the scree and the downstream spreading in a wood. The third event concerns the routing of debris flow in a channel with an ending the reservoir, its overtopping and final spreading in the inhabited area. The fourth event concerns the routing of debris flow along the main channel downstream the initiation area until spreading just upstream a village. All the four occurred debris flows are simulated by modeling runoff that entrained debris flow for determining the solid-liquid hydrograph. The routing of the solid-liquid hydrograph is simulated by a bi-phase cell model based on the kinematic approach. The comparison between simulated and measured erosion and deposition depths is satisfactory. Nearly the same parameters for computing erosion and deposition were used for all the four occurred events. The maps of erosion and deposition depths are obtained by comparing the results of post-event surveys with the pre-event DEM. The post-event surveys were conducted by using different instruments (LiDAR and GPS) or the combination photos-single points depth measurements (in this last case it is possible obtaining the deposition/erosion depths by means of stereoscopy techniques).

  8. Relations between rainfall and triggering of debris-flow: case study of Cancia (Dolomites, Northeastern Italy

    Directory of Open Access Journals (Sweden)

    M. Bacchini

    2003-01-01

    Full Text Available Debris-flows occurring in the area of Cancia (Dolomites, Northeastern Italy in recent years have exposed the population to serious risk. In response to the recurring hazard, an alarm and monitoring system was installed to provide a sufficient level of safeguard for inhabitants and infrastructures. The data recorded at three rain gauges during debris-flow events has been analysed, taking into consideration the different elevation of the gauges to delineate the storm rainfall distributions. Rainfall data is compared with the occurrence of debris-flows to examine relations between debris-flow initiation and rainfall. In addition, the data is compared with that recorded during debris-flows which occurred under similar or different geological settings in the Eastern Italian Alps, in order to define triggering thresholds. A threshold for debris-flow activity in terms of mean intensity, duration and mean annual precipitation (M.A.P. is defined for the study area The normalised rainfall and the normalised intensity are expressed as a per cent with respect to M.A.P. This threshold is compared with thresholds proposed by other authors, and the comparison shows that a lower value is obtained, indicating the debris-flow susceptibility of the area. The threshold equations are:  R/M.A.P. = - 1.36 · ln(I + 3.93  where I > 2 mm/h  I /M.A.P. = 0.74 · D-0.56.  The determination of a debris-flow threshold is linked to the necessity of a fast decisional phase in a warning system for debris-flow protection. This threshold cannot be used as a predictive tool, but rather as a warning signal for technicians who manage the monitoring/warning system.

  9. Geodermatophilus poikilotrophi sp. nov.: A Multitolerant Actinomycete Isolated from Dolomitic Marble

    Directory of Open Access Journals (Sweden)

    Maria del Carmen Montero-Calasanz

    2014-01-01

    Full Text Available A novel Gram-reaction-positive, aerobic actinobacterium, tolerant to mitomycin C, heavy metals, metalloids, hydrogen peroxide, desiccation, and ionizing- and UV-radiation, designated G18T, was isolated from dolomitic marble collected from outcrops in Samara (Namibia. The growth range was 15–35°C, at pH 5.5–9.5 and in presence of 1% NaCl, forming greenish-black coloured colonies on GYM Streptomyces agar. Chemotaxonomic and molecular characteristics of the isolate matched those described for other representatives of the genus Geodermatophilus. The peptidoglycan contained meso-diaminopimelic acid as diagnostic diaminoacid. The main phospholipids were phosphatidylethanolamine, phosphatidylcholine, phosphatidylinositol, and small amount of diphosphatidylglycerol. MK-9(H4 was the dominant menaquinone and galactose was detected as diagnostic sugar. The major cellular fatty acids were branched-chain saturated acids iso-C16:0 and iso-C15:0 and the unsaturated C17:1ω8c and C16:1ω7c. The 16S rRNA gene showed 97.4–99.1% sequence identity with the other representatives of genus Geodermatophilus. Based on phenotypic results and 16S rRNA gene sequence analysis, strain G18T is proposed to represent a novel species, Geodermatophilus poikilotrophi. Type strain is G18T (= DSM 44209T = CCUG 63018T. The INSDC accession number is HF970583. The novel R software package lethal was used to compute the lethal doses with confidence intervals resulting from tolerance experiments.

  10. Offers for our members

    CERN Multimedia

    Staff Association

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    Summer is here, enjoy our offers for the aquatic parcs! Walibi : Tickets "Zone terrestre": 23 € instead of 29 €. Access to Aqualibi: 5 € instead of 6 € on presentation of your SA member ticket. Free for children (3-11 years old) before 12:00 p.m. Free for children under 3, with limited access to the attractions. Car park free. * * * * * Aquaparc : Day ticket: – Children: 33 CHF instead of 39 CHF – Adults : 33 CHF instead of 49 CHF Bonus! Free for children under 5.

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    Summer is here, enjoy our offers for the aquatic parcs! Walibi : Tickets "Zone terrestre": 23 € instead of 29 €. Access to Aqualibi: 5 € instead of 6 € on presentation of your SA member ticket. Free for children (3-11 years old) before 12:00 p.m. Free for children under 3, with limited access to the attractions. Car park free. * * * * * Aquaparc : Day ticket: – Children: 33 CHF instead of 39 CHF – Adults : 33 CHF instead of 49 CHF Bonus! Free for children under 5.

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    CERN Multimedia

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    Summer is here, enjoy our offers for the aquatic parcs! Walibi : Tickets "Zone terrestre": 21,50 € instead of 27 €. Access to Aqualibi: 5 € instead of 6 € on presentation of your SA member ticket. Free for children (3-11 years old) before 12:00 p.m. Free for children under 3, with limited access to the attractions. Car park free. * * * * * Aquaparc : Day ticket: – Children: 33 CHF instead of 39 CHF – Adults : 33 CHF instead of 49 CHF Bonus! Free for children under 5.

  13. Offers for our members

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    Summer is here, enjoy our offers for the aquatic parcs! Walibi : Tickets "Zone terrestre": 21 € instead of 26 €. Access to Aqualibi: 5 € instead of 8 € on presentation of your SA member ticket. Free for children (3-11 years old) before 12 h 00. Free for children under 3, with limited access to the attractions. Car park free. * * * * * Aquaparc : Day ticket: – Children: 30 CHF instead of 39 CHF – Adults : 36 CHF instead of 49 CHF Bonus! Free for children under 5.

  14. Physical Properties and Hydration Resistance of CeO2—and CeO2/Fe2O3—Bearing Dolomite Refractory Products

    Institute of Scientific and Technical Information of China (English)

    XUYanqing; CHENKaixian

    1998-01-01

    Dolomite refractory products with excellent hydration resistance have been produced by using CeO2-and CeO2/Fe2O3-bearing dolomite clinkers,Their physical properties as well as hydration resistance have been investigated,The addition of CeO2 has little harmful effect on the high temperature properties of dolomite refractory products such as hot MOR and slag resistance,And the shelf lives of the dolomite refractory products containing CeO2 and CeO2/Fe2O3 additions at the same condition are two times that of the common dolomite refractory produt.The dolomite refractory product containing CeO2/Fe2O3 combination possesses the best hydration resistance,but gives poor slag resistance.

  15. Complete-member Ethnography

    Directory of Open Access Journals (Sweden)

    Hsun-Yu Sharon Chuang

    2015-11-01

    Full Text Available Within the vast array of ethnographic research methodology, complete-member ethnography (CME is one ethnographic inquiry whose methodological development is still in infantile in intercultural communication research. Specifically in this article, the author includes four major sections to understand and to advance CME. First, the author reviews the historical development of CME, and realizes epistemological intimacy as the core of CME and as how researchers’ complete-memberships may be established. Second, the author explains the concept and practice of epistemological intimacy in extant literature. Third, the author advances the concept of epistemological intimacy to identify and explain five contextual factors that influence a complete-member ethnographer’s complete-membership to his or her research community. The five factors include historicity of identity, institutional memory, situational (intersubjectivity, consensual membership, and symbolic codes. In order to elucidate that said factors are essentially interrelated, the author supplements the five factors with her conceptualizations of selfhood/identity. In the end, the author discusses three potential contributions of how CME can advance critical communication research, which pertain to (a praxis and reflexivity, (b challenging struggles and inequalities in power and privilege, and (c promote hopeful social justice from within.

  16. Effect of dolomite, magnesium oxide (MgO) and chalk (CaCO3) on in vitro fermentation of amorphous and crystalline cellulose and meadow hay using inoculum from sheep.

    Science.gov (United States)

    Váradyová, Zora; Baran, Miroslav; Zawadzki, Wojciech; Siroka, Peter

    2003-01-01

    Some minerals can influence some biochemical parameters of rumen fermentation. The objective of this experiment was to determine the effect of different amounts (0.1, 0.25 and 0.5 g) of dolomite and to compare the effect of dolomite, magnesium oxide (MgO) and chalk (CaCO3) upon the end products of rumen fermentation in vitro. Amorphous and crystalline cellulose as well as meadow hay were used as substrates and incubated with buffered rumen fluid in sealed fermentation bottles. In dependence on the amount of dolomite and the kind of substrate an inhibitory effect of dolomite on methane production was evident. Significant differences of methane production were found between the controls, crystalline cellulose and meadow hay with 0.5 g of dolomite. An increase of total gas production was observed for cellulose with both 0.25 and 0.5 g of dolomite and also for meadow hay with 0.5 g of dolomite. It can be concluded that there was a remarkable effect of dolomite on methane production and also a slight effect of magnesium oxide and chalk as compared to the effect of dolomite on the fermentation parameters of incubated substrates.

  17. Offers for our members

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    The warm weather arrives, it's time to take advantage of our offers Walibi and Aquapark! Walibi : Tickets "Zone terrestre": 21 € instead of 26 € Access to Aqualibi: 5 € instead of 8 € on presentation of your SA member ticket. Free for children (3-11 years old) before 12 h 00. Free for children under 3, with limited access to the attractions. Car park free. * * * * * Aquaparc : Half-day ticket (5 hours): – Children: 26 CHF instead of 35 CHF – Adults : 32 CHF instead of 43 CHF Day ticket: – Children: 30 CHF instead of 39 CHF – Adults : 36 CHF instead of 49 CHF Free for children under 5.

  18. Offers for our members

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    The Courir shops propose the following offer: 15% discount on all articles (not on sales) in the Courir shops (Val Thoiry, Annemasse and Neydens) and 5% discount on sales upon presentation of your Staff Association membership card and an identity card before payment. Summer is here, enjoy our offers for the aquatic parcs! Walibi : Tickets "Zone terrestre": 21 € instead of 26 €. Access to Aqualibi: 5 € instead of 8 € on presentation of your SA member ticket. Free for children (3-11 years old) before 12 h 00. Free for children under 3, with limited access to the attractions. Car park free. * * * * * Aquaparc : Day ticket: – Children: 30 CHF instead of 39 CHF – Adults : 36 CHF instead of 49 CHF Bonus! Free for children under 5.

  19. Offers for our members

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    La banque LCL propose aux membres de l’Association du personnel les avantages suivants : – Un barème Privilège sur le Prêt immobilier – Des avantages tarifaires sur l’épargne, notamment l’assurance-vie. – Un taux préférentiel de prêt à la consommation. En outre, jusqu’au 30 septembre 2013, elle offre 50€ à tous les nouveaux clients, membres de l'Association du personnel. Summer is here, enjoy our offers for the aquatic parcs! Tickets "Zone terrestre" : 21 € instead of de 26 €. Access to Aqualibi : 5 euros instead of 8 euros on presentation of your SA member ticket. Free for children (3-11 years old) before 12 h 00. Free for children under 3, with limited access to the attractions. Free car park. * * * * * * * Full day ticket: – Children : 30 CHF instead of 39 CHF &...

  20. ORDERED INDEX AND DEDOLOMITIZATION OF DOLOMITE CRYSTALS%白云石晶体的有序度与去白云石化反应

    Institute of Scientific and Technical Information of China (English)

    邓敏; 唐明述; 钱光人

    2001-01-01

    评价了不同结构组分类别岩石中白云石晶体的有序度,并通过研究在悬浮分散体系中具有不同有序度的白云石晶体去白云石化反应的动力学行为,建立了白云石有序度与白云石去白云石化反应活性之间的关系。结果表明,泥晶白云岩中白云石晶体的有序度最低;白云质泥晶灰岩、泥质条带白云质泥晶灰岩、白云质粉屑砂屑泥晶灰岩及白云质亮晶鲕粒灰岩中的白云石晶体的有序度次之;豹斑白云质泥晶灰岩、粉晶以上晶粒白云岩中的白云石为近完全有序或完全有序。有序度低的白云石晶体去白云石化反应的扩散活化能、界面化学反应活化能和晶体成核与生长活化能也低,低有序度的白云石具有高的反应性。随着体系温度的升高,白云石晶体有序度对去白云石化反应的影响趋于减小,不同有序度白云石的去白云石化程度趋于相同。%The ordered index of dolomite crystals in dolomitic rocks with differe nt textures and compositions has been evaluated. The influence of the ordered in dex on dynamic of dedolomitization reaction were carried out by determining of r eaction degree of dolomite in suspended powdered dolomite-H2O system. It was est ablished that the ordered index of dolomite crystals is the smallest in dolomicr ites, moderate in dolomitic micrite limestones, stripped dolomitic micrite limes tones, dolomitic silt micrite limestones and dolomitic oosparites, and the large st in leopard dolomitic micrite limestones and crystalline dolostone. The dedolo mitization reaction of dolomite crystals with low ordered index occupies low act ive energy of diffusion, interfacial chemical reaction as well as nucleation and growth. Therefore, lowly ordered dolomite crystals show high reactivity in alka li solutions. Temperature tends to diminish the influence of ordered index on de dolomitization reaction of dolomite crystals.

  1. 白云石(岩)有机成因研究现状及进展%Progress of the Research on Organic Originated Dolomite

    Institute of Scientific and Technical Information of China (English)

    卓鱼周; 赵红格; 李蒙; 高少华

    2015-01-01

    Dolomite is commonly found in the ancient carbonate but rarely in the holocene sediments,which forms the fa-mous “dolomite problem”.In recent years,researches had shown that organic matters are inevitable in the formation of dolomite.On the basis of the investigation of a large number of domestic and foreign literature,this paper explored influ-ence factors of dolomite formation from the perspective of the microscopic mechanism of dolomite dynamic obstacles.The results showed that microbial metabolism regulating played a key factor in dolomite formation,for example,sulfide pro-duced by sulfate-reducing bacteria can reduce the energy of magnesium ion dehydration,which accelerates the dissociation of magnesium ion and promotes the precipitation of dolomite.Studies had also shown that organic macromolecules such as polysaccharides,carboxymethyl cellulose,carboxyl-group,can promote the formation of dolomite in the same way of the sulfate reducing bacteria.This provided a new thought for the research of dolomite genetic mechanism.%白云岩是地质历史中常见的一种碳酸盐岩,但在现代近地表环境下却很难见其踪迹,因此其成因问题成为研究热点。近年来的研究表明,白云石的形成与有机物密不可分。本文在调研大量文献的基础上,从形成白云石动力学障碍这一微观机制出发,探究了其成因。结果表明,微生物的新陈代谢所起的调节作用是白云石形成过程中的关键因素。另外,有机大分子如多糖、羧甲基纤维素、羧基等也能以与硫酸盐还原菌类似的方式促进白云石的形成,这为研究白云石的成因机制提供了新的思路。

  2. Properties of Ca-rich and Mg-rich carbonate films on dolomite: implications for compositional surface mapping with scanning force microscopy.

    Science.gov (United States)

    Hu, Xiaoming; Cubillas, Pablo; Higgins, Steven R

    2010-04-06

    A self-limited monolayer grown on dolomite (CaMg(CO(3))(2)), showing distinct friction contrast with the substrate as reported earlier using lateral force microscopy, was investigated with in situ atomic force microscopy (AFM) adhesion mapping and force-modulation techniques. Force-modulation microscopy revealed lower stiffness on a Ca-rich film in comparison to that on the dolomite surface. The friction contrast therefore results from a larger tip-surface contact area when the AFM probe is in contact with the Ca-rich film as opposed to the contact area with dolomite. The Ca-rich film also exhibited a slightly higher adhesion than did the dolomite substrate; however, the critical shear stresses for the two tip-surface contacts were indistinguishable. A comparative study with a Mg-rich film did not yield noticeable force modulation contrast, indicating similar surface stiffness of the film and the dolomite surface. The similarity in these stiffness quantities was further corroborated by friction-load data that demonstrated similar friction forces on the two surfaces. The previously reported film strain in the Ca-rich system is likely linked to the lower stiffness observed, with both of these properties related to the Ca/Mg composition of the film.

  3. Evaluation of cytotoxic, oxidative stress, proinflammatory and genotoxic responses of micro- and nano-particles of dolomite on human lung epithelial cells A(549).

    Science.gov (United States)

    Patil, Govil; Khan, Mohd Imran; Patel, Devendra Kumar; Sultana, Sarwat; Prasad, Rajendra; Ahmad, Iqbal

    2012-09-01

    Dolomite is a natural mineral of great industrial importance and used worldwide, thus millions of workers are at risk of occupational exposure. Its toxicity is however, meagerly documented. In the present investigation, a dolomite powder obtained from its milling unit was analyzed by some standard methods namely, optical microscopy, transmission electron microscopy and dynamic light scattering. Results showed that dolomite powder contained particles of different shapes and size both microparticles (MPs) and nanoparticles (NPs), suggesting potential occupational exposure of these particles. An attempt was therefore, made to investigate dolomite toxicity in a particle size-dependent manner in human lung epithelial cells A(549). The comparative toxicity evaluation of MPs and NPs was carried out by assessing their effects on cell viability, membrane damage, glutathione, reactive oxygen species (ROS), lipid peroxidation (LPO), micronucleus (MN) and proinflammatory cytokines, namely tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and interleukin-6 (IL-6). These markers of cytotoxicity, genotoxicity and inflammation were assayed in cells exposed to MPs and NPs in a dose-and time-dependent manner. Invariably, their toxic effects were dose-and time-dependent while NPs in general were significantly more toxic. Notably, NPs caused oxidative stress, genotoxicity and inflammatory responses, as seen by significant induction of ROS, LPO, MN, TNF-α, IL-1β and IL-6. Thus, the study tends to suggest that separate health safety standards would be required for micrometer and nanometer scale particles of dolomite.

  4. Preliminary magnetostratigraphy and environmental magnetism of the Lower Cretaceous from the Italian Dolomites

    Science.gov (United States)

    Savian, J. F.; Jovane, L.; Florindo, F.; Lukeneder, A.

    2011-12-01

    The Lower Cretaceous (~146 to 100 Ma) represents an enigmatic time interval for paleoclimatic, paleogeography and paleomagnetic evolution of the Earth's history. The climatic changes include global oceanic anoxic events (OAEs), biotic changes, global excursions of carbon and strontium isotopes, rises in eustatic sea level and paleotemperature. Paleoceanography was marked by a rapid rate of ocean spreading in the Atlantic. The opening of the Atlantic Ocean was wide enough to allow significant circulation of masses of waters across the equator. This period is furthermore important for the oceanographic events occurring at the base of the Aptian (Selli Level). This period also present one of the most intriguing geomagnetic events: the long normal Cretaceous superchron, lasted for almost 40 million years. We study here the lower Cretaceous deposits of the Puez section in the Dolomites (northern Italy) which represents a continuous section during this period. The samples collected represent marine sedimentary materials of the Biancone and Puez formations. The Puez section consists essentially of green-grey to red limestones and calcareous marls. We present preliminary results of integrated magnetostratigraphic analysis, including a detailed lithostratigraphy and environmental magnetism. We recognize magnetic behavior that are relative to normal polarity (the normal Cretaceous superchron), with a short reverse interval that might represent the M-1r event. We also recognize a series of normal and reverse polarities (below the normal Cretaceous superchron) which can be referred to the magnetozones M1/M5. The environmental magnetic data consists of magnetic susceptibility (χ), natural remanent magnetization (NRM), anhysteretic remanent magnetization (ARM), isothermal remanent magnetization (IRM) at 900 mT and backfield isothermal remanent magnetization (BIRM) at 100 mT and 300 mT. Derived parameters, such as S-ratio (S300=BIRM300/IRM900) and hard isothermal remanent

  5. Technique for cleaning Tarragona miocene age dolomitized silty limestone, altered by urban pollution

    Directory of Open Access Journals (Sweden)

    Guasch, Nuria

    2008-06-01

    Full Text Available This paper reports the results of studies conducted to evaluate the most suitable cleaning technique for highly dolomitized, middle Miocene (Serravallian calcisiltite from Tarragona, Spain, used to build Les Saleses Convent Church in Barcelona. This stone material was widely used in the decorative and sculptural details on Catalonian modernist buildings.On the church, as on most of the modernist buildings made of this material, the limestone was found to be greatly decayed, with highly reactive black crusts, soluble salts and disaggregation. The cause of these pathologies lay in both the surrounding environment and the original crystalline water-repellent coating applied to the stone surface. Based on the results of an analysis of the stone, the coating and the alterations, water-based procedures and chemical poultices were ruled out as cleaning methods. In subsequent testing, low pressure abrasive blasting and the localized use of laser techniques were found to yield good results. These two techniques were checked for effectiveness and their parameters were determined.En este trabajo se exponen los estudios realizados para valorar la técnica de limpieza más apropiada de la calcisiltita muy dolomitizada del Mioceno medio (Serravalliense de Tarragona empleada en la Iglesia del Convento de Les Saleses (Barcelona, material pétreo muy empleado en el modernismo catalán para la talla de elementos decorativos y escultóricos.El material, al igual que en la mayoría de los edificios modernistas donde se ha utilizado, presentaba degradación importante con costras negras muy reactivas, sales solubles y arenizaciones. Además del origen ambiental de las patologías, éstas también estaban relacionadas con la pátina original de tratamiento, cristalina e hidrófuga, aplicada en toda su superficie. Tras el análisis del material pétreo, de la pátina, y de las alteraciones, que hicieron descartar los métodos de limpieza basados en agua y los qu

  6. Family members' experiences of autopsy

    NARCIS (Netherlands)

    Oppewal, F; Meyboom-de Jong, B

    2001-01-01

    Background. The experiences of family members will teach us how to handle an autopsy, the ultimate quality assessment tool. Objective. The aim of this study was to determine surviving family members' experience of autopsy. Method. Seven GPs were asked to approach surviving family members of autopsie

  7. Family members' experiences of autopsy

    NARCIS (Netherlands)

    Oppewal, F; Meyboom-de Jong, B

    Background. The experiences of family members will teach us how to handle an autopsy, the ultimate quality assessment tool. Objective. The aim of this study was to determine surviving family members' experience of autopsy. Method. Seven GPs were asked to approach surviving family members of

  8. EFFECT OF DOLOMITE AND LIMESTONE ON WASTE TYRE PYROLYSIS%白云石和石灰石对废轮胎热解产物的影响

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    This paper introduces the effect of dolomite and limestone on waste tyre pyrolysis. When waste tyre was pyrolyzed in 700?℃, the derived gases was passed through the catalyst zone in which the temperature was controlled at 700?℃, 800?℃and 900 ℃, respectively. It is found that both dolomite and limestone affect the product distribution of tyre pyrolysis with erhancing gas yield and effective absorption of H2S. The effect of these catalysts on tar cracking is obvious at 900 ℃, however, the life of catalyst is short. The product yields are about 40% for gas, 30% for liquid and 30% for char in the presence of dolomite and limestone. The result indicates that multi-use of the pyrolysed product is highly recommended.

  9. POTENTIALLY UNSTABLE SLOPE ABOVE ORE PROCESSING PLANT IN THE "OČURA" DOLOMITE QUARRY (LEPOGLAVA, NORTH CROATIA

    Directory of Open Access Journals (Sweden)

    Karlo Braun

    1993-12-01

    Full Text Available The complex engineering investigation, in the nearest surroun-dig of the conditionally stable high slope, close to ore processing facilities in the dolomite quarry »Očura« near Lepoglava (North Croatia, was carried out. Studying the tectonic features of the rock mass, discontinuities referent to the slope stability, was found out. Rock fragment size was measured and data processed using statistical design. According to rock fragment mean values, velocity of the longitudinal seismic waves was predicted. This values was compared with velocities of the longitudinal seismic waves, determined using gcophisical refraction seismic method. Physical and mechanical properties of the dolomite rock mass, considering longitudinal and transversal seismic wave velocities, and »RMR«-classification was assesed. All the results indicate, that the slope above the ore processing facilities should be consider as conditionally stable, with real probability to get unstable under the vibrations caused by blasting, during the exploitation in the field, close behind the investigated slope (the paper is published in Croatian.

  10. Investigation of the Role of Polysaccharide in the Dolomite Growth at Low Temperature by Using Atomistic Simulations.

    Science.gov (United States)

    Shen, Zhizhang; Szlufarska, Izabela; Brown, Philip E; Xu, Huifang

    2015-09-29

    Dehydration of water from surface Mg(2+) is most likely the rate-limiting step in the dolomite growth at low temperature. Here, we investigate the role of polysaccharide in this step using classical molecular dynamics (MD) calculations. Free energy (potential of mean force, PMF) calculations have been performed for water molecules leaving the first two hydration layers above the dolomite (104) surface under the following three conditions: without catalyst, with monosaccharide (mannose), and with oligosaccharide (three units of mannose). MD simulations reveal that there is no obvious effect of monosaccharide in lowering the dehydration barrier for surface Mg(2+). However, we found that there are metastable configurations of oligosaccharide, which can decrease the dehydration barrier of surface Mg(2+) by about 0.7-1.1 kcal/mol. In these configurations, the molecule lies relatively flat on the surface and forms a bridge shape. The hydrophobic space near the surface created by the nonpolar -CH groups of the oligosaccharide in the bridge conformation is the reason for the observed reduction of dehydration barrier.

  11. Diversity of endolithic fungal communities in dolomite and limestone rocks from Nanjiang Canyon in Guizhou karst area, China.

    Science.gov (United States)

    Tang, Yuan; Lian, Bin

    2012-06-01

    The endolithic environment, the tiny pores and cracks in rocks, buffer microbial communities from a number of physical stresses, such as desiccation, rapid temperature variations, and UV radiation. Considerable knowledge has been acquired about the diversity of microorganisms in these ecosystems, but few culture-independent studies have been carried out on the diversity of fungi to date. Scanning electron microscopy of carbonate rock fragments has revealed that the rock samples contain certain kinds of filamentous fungi. We evaluated endolithic fungal communities from bare dolomite and limestone rocks collected from Nanjiang Canyon (a typical karst canyon in China) using culture-independent methods. Results showed that Ascomycota was absolutely dominant both in the dolomite and limestone fungal clone libraries. Basidiomycota and other eukaryotic groups (Bryophyta and Chlorophyta) were only detected occasionally or at low frequencies. The most common genus in the investigated carbonate rocks was Verrucaria. Some other lichen-forming fungi (e.g., Caloplaca, Exophiala, and Botryolepraria), Aspergillus, and Penicillium were also identified from the rock samples. The results provide a cross-section of the endolithic fungal communities in carbonate rocks and help us understand more about the role of microbes (fungi and other rock-inhabiting microorganisms) in rock weathering and pedogenesis.

  12. In Developping a Bench-Scale Circulating Fluidized Bed Combustor to Burn High Ash Brazilian Coal-Dolomites Mixtures

    Science.gov (United States)

    Ramírez Behainne, Jhon Jairo; Hory, Rogério Ishikawa; Goldstein, Leonardo; Bernárdez Pécora, Araí Augusta

    This work considers some of the questions in burning high ash Brazilian coal-dolomite mixtures in a bench-scale circulating fluidized bed combustor (CFBC). Experimental tests were performed with the CE4500 coal from Santa Catarina State, in southern Brazil, with a Sauter mean diameter d p =43 μm. The coal particles were mixed with dolomite particles of d p = 111 μm and this fuel mixture was fed into the circulating fluidized reactor, previously loaded with quartz sand particles of d p =353 μm. This inert material was previously heated by the combustion of liquefied petroleum gas up to the ignition temperature of the fuel mixture. The CFBC unit has a 100mm internal diameter riser, 4.0m high, as well as a 62.8mm internal diameter downcomer. The loop has a cyclone, a sampling valve to collect particles and a 62.8mm internal diameter L-valve to recirculate the particles in the loop. A screw feeder with a rotation control system was used to feed the fuel mixture to the reactor. The operational conditions were monitored by pressure taps and thermocouples installed along the loop. A data acquisition system showed the main operational conditions to control. Experimental tests performed put in evidence the problems found during bed operation, with special attention to the solids feed device, to the L-valve operation, to particle size, solids inventory, fluidized gas velocity, fuel mixture and recirculated solids feeding positions.

  13. Hydrogeochemical studies of the Rustler Formation and related rocks in the Waste Isolation Pilot Plant Area, Southeastern New Mexico

    Energy Technology Data Exchange (ETDEWEB)

    Siegel, M.D.; Lambert, S.J.; Robinson, K.L. (eds.)

    1991-08-01

    Chemical, mineralogical, isotopic, and hydrological studies of the Culebra dolomite member of the Rustler Formation and related rocks are used to delineate hydrochemical facies and form the basis for a conceptual model for post-Pleistocene groundwater flow and chemical evolution. Modern flow within the Culebra in the Waste Isolation Pilot Plant (WIPP) area appears to be largely north-to-south; however, these flow directions under confined conditions are not consistent with the salinity distribution in the region surrounding the WIPP Site. Isotopic, mineralogical, and hydrological data suggest that vertical recharge to the Culebra in the WIPP area and to the immediate east and south has not occurred for several thousand years. Eastward increasing {sup 234}U/{sup 238}U activity ratios suggest recharge from a near-surface Pleistocene infiltration zone flowing from the west-northwest and imply a change in flow direction in the last 30,000 to 12,000 years. 49 refs., 34 figs., 4 tabs.

  14. Preliminary performance assessment for the Waste Isolation Pilot Plant, December 1992. Volume 4: Uncertainty and sensitivity analyses for 40 CFR 191, Subpart B

    Energy Technology Data Exchange (ETDEWEB)

    1993-08-01

    Before disposing of transuranic radioactive waste in the Waste Isolation Pilot Plant (WIPP), the United States Department of Energy (DOE) must evaluate compliance with applicable long-term regulations of the United States Environmental Protection Agency (EPA). Sandia National Laboratories is conducting iterative performance assessments (PAs) of the WIPP for the DOE to provide interim guidance while preparing for a final compliance evaluation. This volume of the 1992 PA contains results of uncertainty and sensitivity analyses with respect to the EPA`s Environmental Protection Standards for Management and Disposal of Spent Nuclear Fuel, High-Level and Transuranic Radioactive Wastes (40 CFR 191, Subpart B). Additional information about the 1992 PA is provided in other volumes. Results of the 1992 uncertainty and sensitivity analyses indicate that, conditional on the modeling assumptions, the choice of parameters selected for sampling, and the assigned parameter-value distributions, the most important parameters for which uncertainty has the potential to affect compliance with 40 CFR 191B are: drilling intensity, intrusion borehole permeability, halite and anhydrite permeabilities, radionuclide solubilities and distribution coefficients, fracture spacing in the Culebra Dolomite Member of the Rustler Formation, porosity of the Culebra, and spatial variability of Culebra transmissivity. Performance with respect to 40 CFR 191B is insensitive to uncertainty in other parameters; however, additional data are needed to confirm that reality lies within the assigned distributions.

  15. Ocean acidification does not affect magnesium composition or dolomite formation in living crustose coralline algae, Porolithon onkodes in an experimental system

    Science.gov (United States)

    Nash, M. C.; Uthicke, S.; Negri, A. P.; Cantin, N. E.

    2015-09-01

    There are concerns that Mg-calcite crustose coralline algae (CCA), which are key reef builders on coral reefs, will be most susceptible to increased rates of dissolution under higher pCO2 and ocean acidification. Due to the higher solubility of Mg-calcite, it has been hypothesised that magnesium concentrations in CCA Mg-calcite will decrease as the ocean acidifies, and that this decrease will make their skeletons more chemically stable. In addition to Mg-calcite, CCA Porolithon onkodes, the predominant encrusting species on tropical reefs, can have dolomite (Ca0.5Mg0.5CO3) infilling cell spaces which increases their stability. However, nothing is known about how bio-mineralised dolomite formation responds to higher pCO2. Using P. onkodes grown for 3 and 6 months in tank experiments, we aimed to determine (1) if mol % MgCO3 in new crust and new settlement was affected by increasing CO2 levels (365, 444, 676 and 904 μatm), (2) whether bio-mineralised dolomite formed within these time frames, and (3) if so, whether this was effected by CO2. Our results show that there was no significant effect of CO2 on mol % MgCO3 in any sample set, indicating an absence of a plastic response under a wide range of experimental conditions. Dolomite within the CCA cells formed within 3 months and dolomite abundance did not vary significantly with CO2 treatment. While evidence mounts that climate change will impact many sensitive coral and CCA species, the results from this study indicate that reef-building P. onkodes will continue to form stabilising dolomite infill under near-future acidification conditions, thereby retaining its higher resistance to dissolution.

  16. Ocean acidification does not affect magnesium composition or dolomite formation in living crustose coralline algae, Porolithon onkodes in an experimental system

    Directory of Open Access Journals (Sweden)

    M. C. Nash

    2015-01-01

    Full Text Available There are concerns that Mg-calcite crustose coralline algae (CCA, which are key reef builders on coral reefs, will be most susceptible to increased rates of dissolution under higher pCO2 and ocean acidification. Due to the higher solubility of Mg-calcite, it has been hypothesized that magnesium concentrations in CCA Mg-calcite will decrease as the ocean acidifies, and that this decrease will make their skeletons more chemically stable. In addition to Mg-calcite, CCA Porolithon onkodes the predominant encrusting species on tropical reefs, can have dolomite (Ca0.5Mg0.5CO3 infilling cell spaces which increases their stability. However, nothing is known about how bio-mineralised dolomite formation responds to higher pCO2. Using P. onkodes grown for 3 and 6 months in tank experiments, we aimed to determine (1 if mol % MgCO3 in new crust and new settlement affected by increasing pCO2 levels (365, 444, 676 and 904 ppm, (2 whether bio-mineralised dolomite formed within these time frames, and (3 if so, whether this was effected by pCO2. Our results show there was no significant effect of pCO2 on mol % MgCO3 in any sample set, indicating an absence of a plastic response under a wide range of experimental conditions. Dolomite within the CCA cells formed within 3 months and dolomite abundance did not vary significantly with pCO2 treatment. While evidence mounts that climate change will impact many sensitive coral and CCA species, the results from this study indicate that reef-building P. onkodes will continue to form stabilising dolomite infill under near-future acidification conditions, thereby retaining its higher resistance to dissolution.

  17. First-principles calculations of high-pressure iron-bearing monoclinic dolomite and single-cation carbonates with internally consistent Hubbard U

    Science.gov (United States)

    Solomatova, Natalia V.; Asimow, Paul D.

    2017-08-01

    It has been proposed that iron has a significant effect on the relative stability of carbonate phases at high pressures, possibly even stabilizing double-cation carbonates (e.g., dolomite) with respect to single-cation carbonates (e.g., magnesite, aragonite and siderite). X-ray diffraction experiments have shown that dolomite transforms at 35 GPa to a high-pressure polymorph that is stable to decomposition; however, there has been disagreement on the structure of the high-pressure phase (Mao et al. in Geophys Res Lett 38, 2011. doi: 10.1029/2011GL049519; Merlini et al. in Proc Natl Acad Sci 109:13509-13514, 2012. doi: 10.1073/pnas.1201336109). Ab initio calculations interfaced with an evolutionary structure prediction algorithm demonstrated that a C2/c polymorph of pure CaMg(CO3)2 dolomite is more stable than previously reported structures (Solomatova and Asimow in Am Mineral 102:210-215, 2017, doi: 10.2138/am-2017-5830). In this study, we calculate the relative enthalpies up to 80 GPa for a set of carbonate phases including Fe-bearing solutions and endmembers, using the generalized gradient approximation and a Hubbard U parameter calculated through linear response theory to accurately characterize the electronic structure of Fe. When calculated with a constant U of 4 eV, the spin transition pressure of (Mg,Fe)CO3 agrees well with experiments, whereas an internally consistent U overestimates the spin transition pressure by 50 GPa. However, whether we use constant or internally consistent U values, a higher iron concentration increases the stability field of dolomite C2/c with respect to single-cation carbonate assemblages, but iron-free dolomite is not stable with respect to single-cation carbonates at any pressure. Thus, high-pressure polymorphs of Fe-bearing dolomite could in fact represent an important reservoir for carbon storage within oxidized sections of Earth's mantle.

  18. Research on Dolomite as Coarse Aggregate in Asphalt Mixture%白云岩作为粗集料用于沥青混合料的研究

    Institute of Scientific and Technical Information of China (English)

    高宏t虹l-91同/厶

    2012-01-01

    Through the laboratory test research on dolomite as coarse aggregate of asphalt mixture in Fushun area, the feasibility of dolomite as coarse aggregate in Fushun area is tested and verified.%通过对抚顺地区白云岩作为沥青混合料粗集料的室内试验研究,验证了抚顺地区的白云岩作为沥青混合料粗集料的可行性。

  19. The advances in the study of microbial dolomite%微生物成因白云石研究进展

    Institute of Scientific and Technical Information of China (English)

    王宁

    2011-01-01

    "Dolomite problem" has long been one of the focuses and difficulties in the study of sedimentary geology. Dolomite serves as an important reservoir of oil and gas both in China and abroad. Therefore, the understanding of the formation process of dolomite is significant for the exploration of oil and gas in carbonate rocks. There are many models to explain the origin of dolomite, such as the Sabhka evaporation model, the seepage-reflux model, the burial adjustment model, the mixing zone model, and the tidal pumping model. During the past decades, with the further research on the dolomite formation at low temperature, the microbial dolomite model, as a new dolomite origin model, was proposed and well developed. This paper reviews the progress of research on microbial dolomite. Three kinetic barriers of dolomite precipitation under earth surface conditions were listed, which are strong hydration energy of magnesium ion, the existence of sulfate ion and the low concentration and low activity of carbonate ion. The background for putting forward the microbial dolomite model and the growth process and morphological characteristics of microbial dolomite were briefly described. The mediation of microbeduring the formation process of dolomite was explained in detail. It is pointed out that the existence of microbes (e. G., sulfate-reducing bacteria and ancient methane bacteria) could change the ion balance of solution and help dolomite to overcome the kinetic barriers during the precipitation process. The application of oxygen isotope of microbial dolomite to the reconstruction of palaeo-temperature and ancient climate change was discussed. The future orientations for research on microbial dolomite (e. G., multidisciplinary analysis, application of high technology etc.) were predicated. The further investigation into the microbial dolomite model will provide researchers with a new approach to understanding the "dolomite problem" and is also helpful to the study of dolomite

  20. A novel method for simultaneous determination of selected elements in dolomite and magnesia by Inductively Coupled Plasma Atomic Emission Spectroscopy with slurry sample introduction

    Science.gov (United States)

    Bok-Badura, Joanna; Jakóbik-Kolon, Agata; Turek, Marian; Szczerba, Jacek; Lemanowicz, Marcin; Karoń, Krzysztof

    2015-11-01

    The slurry nebulization ICP-AES method for simultaneous determination of selected elements in dolomite and magnesia was proposed. Based on the investigation results the optimal conditions for this analysis were as follows: particle size CRM 782-1 and High Purity Magnesia BCS-CRM 389/1 were analyzed. Student's t-test proved that there were no statistically significant differences between determined values and the certified ones. This proves that the slurry sample introduction into plasma in ICP-AES technique can be applied for simultaneous determination of elements in dolomite and magnesia.

  1. Characterization of foams obtained from cassava starch, cellulose fibres and dolomitic limestone by a thermopressing process

    Directory of Open Access Journals (Sweden)

    Vivian Consuelo Reolon Schmidt

    2010-02-01

    Full Text Available Cassava starch, dolomitic limestone and eucalypt cellulose fibres were used to prepare foam trays that could be used to pack foodstuffs. The influence of the cellulose fibre concentration in the composite formulation was investigated using 5, 10, 15, 20, 30 and 40% of fibres. The results indicated that an increase in cellulose fibre concentration promoted a decrease in density and tensile strength of the foam samples. The tensile strength at break for foam trays containing 5% of cellulose fibres was 3.03MPa, whilst the commercial trays of expanded polystyrene used to pack foods in supermarkets presented a tensile strength of 1.49 MPa. The elongation at break of the foam trays obtained in this work varied slightly with increase in cellulose fibre concentration, the values being about 20% lower than the elongation at break observed for commercial foam trays of expanded polystyrene. Thus, the materials developed in this work represented a possible alternative to the use of EPS foam trays for packing dry foods. The trays' properties need to be improved for their use with moist foods.Amido de mandioca, calcário dolomítico e fibras celulósicas de eucalipto foram usados para preparar bandejas biodegradáveis que podem ser usadas como embalagens para alimentos. A influência da concentração de fibras na formulação dos compostos foi investigada, usando 5, 10, 15, 20, 30 e 40% de fibras. Os resultados indicaram que o aumento na concentração de fibras celulósicas promove uma diminuição na densidade e na resistência a tração das amostras. A tensão na ruptura para as bandejas contendo 5% de fibras celulósicas foi de 3,03 MPa, enquanto as bandejas comerciais de poliestireno expandido (EPS usadas para embalagens alimentícias em supermercados apresentaram uma tensão de 1.49 MPa. A elongação na ruptura das bandejas obtidas neste trabalho variou ligeiramente com o aumento da concentração de fibra celulósica, os valores são aproximadamente

  2. Diffusion-controlled garnet growth in siliceous dolomites of the Adamello contact aureole, N-Italy

    Science.gov (United States)

    Muller, T.; Fiebich, E.; Foster, C. T.

    2012-12-01

    Texture forming processes are controlled by many factors, such as material transport through polycrystalline materials, surface kinetics, fluid flow, and many others. In metamorphic rocks, texture forming processes typically involve local reactions linked to net mass transfer which allows constraining the actual reaction path in more detail. In this study, we present geochemical data combined with textural modeling to constrain the conditions and reaction mechanism during contact metamorphic garnet growth in siliceous dolomites in the southern Adamello Massif, Italy. The metamorphic garnet porphyroblasts are poikiloblastic and idiomorphic in shape with a typical grain size ranging between 0.6-1 cm in diameter sitting in a matrix of calcite+diopside+anorthite+wollastonite. Inclusions in the grossular-rich garnets are almost uniquely diopside. On the hand specimen, garnets are surrounded by visible rims of about 0.6 mm indicating a diffusion-limited reaction mechanism to be responsible for the garnet formation. In the course of this study samples have been characterized by polarization microscopy, element x-ray maps using EMPA, cathodulominescence images and stable isotope analyses of carbon and oxygen of matrix carbonates. In addition, pseudosections have been calculated using the software package PerpleX (Connolly, 2005) based on the bulk chemistry of collected samples. Results indicate that the visible margin consists of a small rim (< 1 mm) purely consisting of recrystallized calcite adjacent to the garnet edge. The major part of the observed halo, however, is characterized by the absence of anorthite and wollastonite. The observed texture of garnet porphyroblasts growing and simultaneously forming an anorthite and wollastonite free margin can successfully be reproduced using the SEG program (Foster, 1993), which assumes diffusive mass transport. Therefore the model constrains the diffusive fluxes of Ca, Mg, Al and Si by mass balance and the local Gibbs

  3. Debris flow monitoring experience in the Cancia basin (Dolomites, Northeast Italian Alps).

    Science.gov (United States)

    Stancanelli, Laura; Bernard, Martino; Gregoretti, Carlo; Berti, Matteo; Simoni, Alessandro; Lanzoni, Stefano

    2016-04-01

    The monitoring campaign presented here aims to understand the dynamics of sediment transport processes in small head-water catchments of the Italian Alps and to evaluate the rainfall thresholds for debris flow triggering. The monitored basin of Cancia is located on the Eastern Italian Dolomites, in the Belluno Province. In particular, it is situated on the left side on the Boite river valley, next to the Borca di Cadore village, and is delimited by the western slope of the Mt. Antelao. The drainage area is 1.8 km2 while the elevation ranges from 2451 m a.s.l. to 880 m a.s.l., with a slope varying from 30-40° in the upper part to 10-15° in the lower part (fan area). The basin is characterized by a lithology very common in the Italian Alps, which consist of high permeability, poorly sorted rock debris, containing boulders up to 3-4 m in diameter, and include heterogeneous scree, alluvium and old debris flow deposits. The spatial distribution of sediment is characterized by: an upper part where prevails the presence of rocks, a medium part characterized by poorly sorted rock debris and fine sediment material, and a downstream part plenty of sediment material The Cancia basin is prone to stony debris flows, owing to the plenty availability of loose and coarse sediments and frequent convective events. In particular, the smaller grain sized material is provided by the erosion of lateral slope, while gravel, pebbles and cobbles are provided by the upper part of the basin, characterized by rocky material. The precipitation regime is marked by rainfalls of short duration and high intensity, usually occurring in the summer period. The debris flow channel has began to be surveyed in August 2009 to identify the debris flow generation area. At the beginning of July 2013 topographical surveys of the channel downstream the triggering area began in order to investigate the morphological evolution of the debris flow channel from 2013 until 2015. Moreover, at the beginning of

  4. Coupling autotrophic sulfide mineral weathering with dolomite dissolution in a subglacial ecosystem

    Science.gov (United States)

    Boyd, E. S.; Hamilton, T. L.; Havig, J. R.; Lange, R.; Murter, E.; Skidmore, M. L.; Peters, J.; Shock, E.

    2013-12-01

    and abundant autotrophic community in the RG subglacial environment with the dominant population exhibiting close affiliation with the sulfide mineral oxidizing autotroph Sideroxydans lithoautotrophicus. Analysis of dissolved solutes in late season glacial meltwaters indicate that the production of sulfate through sulfide mineral oxidation is closely coupled with increases in the concentration of calcium, magnesium, and carbonate ions, suggesting that the oxidation of pyrite is closely coupled with the dissolution of dolomite, a dominant carbonate mineral in the local bedrock. Thus, microbially mediated sulfide mineral weathering in subglacial systems provides a conduit for transport of nutrients to downstream freshwater and marine systems. Collectively, these results underscore the contribution of cold and dark subglacial environments to global biogeochemical cycles, both today and in Earth's past, and demonstrate the potential role of autotrophic microorganisms in sustaining subglacial microbial communities over geologic time periods.

  5. Petrology and diagenetic history of the upper shale member of the Late Devonian–Early Mississippian Bakken Formation, Williston Basin, North Dakota

    Science.gov (United States)

    Neil S. Fishman,; Sven O. Egenhoff,; Boehlke, Adam; Lowers, Heather

    2015-01-01

    The organic-rich upper shale member of the upper Devonian–lower Mississippian Bakken Formation (Williston Basin, North Dakota, USA) has undergone significant diagenetic alteration, irrespective of catagenesis related to hydrocarbon generation. Alteration includes precipitation of numerous cements, replacement of both detrital and authigenic minerals, multiple episodes of fracturing, and compaction. Quartz authigenesis occurred throughout much of the member, and is represented by multiple generations of microcrystalline quartz. Chalcedonic quartz fills radiolarian microfossils and is present in the matrix. Sulfide minerals include pyrite and sphalerite. Carbonate diagenesis is volumetrically minor and includes thin dolomite overgrowths and calcite cement. At least two generations of fractures are observed. Based on the authigenic minerals and their relative timing of formation, the evolution of pore waters can be postulated. Dolomite and calcite resulted from early postdepositional aerobic oxidation of some of the abundant organic material in the formation. Following aerobic oxidation, conditions became anoxic and sulfide minerals precipitated. Transformation of the originally opaline tests of radiolaria resulted in precipitation of quartz, and quartz authigenesis is most common in more distal parts of the depositional basin where radiolaria were abundant. Because quartz authigenesis is related to the distribution of radiolaria, there is a link between diagenesis and depositional environment. Furthermore, much of the diagenesis in the upper shale member preceded hydrocarbon generation, so early postdepositional processes were responsible for occlusion of significant original porosity in the member. Thus, diagenetic mineral precipitation was at least partly responsible for the limited ability of these mudstones to provide porosity for storage of hydrocarbons.

  6. Petrology and diagenetic history of the upper shale member of the Late Devonian-Early Mississippian Bakken Formation, Williston Basin, North Dakota

    Science.gov (United States)

    Neil S. Fishman,; Sven O. Egenhoff,; Boehlke, Adam; Lowers, Heather A.

    2015-01-01

    The organic-rich upper shale member of the upper Devonian–lower Mississippian Bakken Formation (Williston Basin, North Dakota, USA) has undergone significant diagenetic alteration, irrespective of catagenesis related to hydrocarbon generation. Alteration includes precipitation of numerous cements, replacement of both detrital and authigenic minerals, multiple episodes of fracturing, and compaction. Quartz authigenesis occurred throughout much of the member, and is represented by multiple generations of microcrystalline quartz. Chalcedonic quartz fills radiolarian microfossils and is present in the matrix. Sulfide minerals include pyrite and sphalerite. Carbonate diagenesis is volumetrically minor and includes thin dolomite overgrowths and calcite cement. At least two generations of fractures are observed. Based on the authigenic minerals and their relative timing of formation, the evolution of pore waters can be postulated. Dolomite and calcite resulted from early postdepositional aerobic oxidation of some of the abundant organic material in the formation. Following aerobic oxidation, conditions became anoxic and sulfide minerals precipitated. Transformation of the originally opaline tests of radiolaria resulted in precipitation of quartz, and quartz authigenesis is most common in more distal parts of the depositional basin where radiolaria were abundant. Because quartz authigenesis is related to the distribution of radiolaria, there is a link between diagenesis and depositional environment. Furthermore, much of the diagenesis in the upper shale member preceded hydrocarbon generation, so early postdepositional processes were responsible for occlusion of significant original porosity in the member. Thus, diagenetic mineral precipitation was at least partly responsible for the limited ability of these mudstones to provide porosity for storage of hydrocarbons.

  7. Practice of raising shaft kiln dolomitic lime content of Xingsteel%邢钢提高竖窑白云灰含量的实践

    Institute of Scientific and Technical Information of China (English)

    霍志军; 王君朝

    2011-01-01

    随着邢钢精品钢战略的纵深实施,精品钢比例日益增加,炼钢对白云灰质量的要求也越来越高,所以提高白云灰质量势在必行。通过对3^#竖窑白云灰的质量分析,制定相应对策,保证白云石化学成分稳定,取得了显著的经济效益。%With the deep implementation of perfect quality steel strategy of Xingsteel, the proportion of perfect quality steel is increased day by day, the requirement of the quality of dolomitic lime for steelmaking of Xingsteel is becoming higher and higher. Therefore the improvement of dolomitic lime quality is imperative under the situation. Through the analysis of dolomitic lime quality of No.3 shaft kiln, the corresponding countermeasures are made to ensure the stability of chemical composition of dolomite, the remarkable economic benefit is achieved

  8. Systematic study of the dolomite (104) surface by bimodal dynamic force microscopy in ultra-high vacuum.

    Science.gov (United States)

    Kawai, Shigeki; Pina, Carlos M; Bubendorf, Alexander; Fessler, Gregor; Glatzel, Thilo; Gnecco, Enrico; Meyer, Ernst

    2013-02-08

    We have investigated the morphology and structure of dolomite MgCa(CO(3))(2)(104) surfaces by bimodal dynamic force microscopy with flexural and torsional resonance modes in ultra-high vacuum at room temperature. We found that the surface slowly decomposes by degassing CO(2) in a vacuum and becomes covered by amorphous clusters, presumably MgO and CaO. By choosing an optimal sample preparation procedure (i.e. cleaving in a vacuum and mild annealing for stabilizing clusters for a short time), atomically clean surfaces were obtained. The complex tip-sample interaction, arising from carbonate groups and Mg and Ca atoms of the surface, induces a large variety of atomic-scale imaging features.

  9. Effectiveness factors for a commercial steam reforming (Ni) catalyst and for a calcined dolomite used downstream biomass gasifiers

    Energy Technology Data Exchange (ETDEWEB)

    Corella, J.; Narvaez, I.; Orio, A. [Madrid Univ. (Spain). Dept. of Chem. Eng.

    1996-12-31

    A commercial steam reforming catalyst from BASF, the G1-25 S one, and a calcined dolomite, Norte-1, from Cantabria-Spain, have been used, once crushed and sieved to different particle fractions between 1.0 and 4.0 mm. The materials have been tested downstream small pilot biomass gasifiers, bubbling fluidized bed type, gasifying with air and with steam. The Thiele modulus and the effectiveness factor have been calculated at temperatures of 750-850 deg C. It is experimentally shown that diffusion control plays an important part when particle size is larger than ca. 0.5 mm. This has to be taken into account when comparing the quality of the solids for tar elimination. (author) (5 refs.)

  10. Hydrothermal zebra dolomite in the Great Basin, Nevada--attributes and relation to Paleozoic stratigraphy, tectonics, and ore deposits

    Science.gov (United States)

    Diehl, S.F.; Hofstra, A.H.; Koenig, A.E.; Emsbo, P.; Christiansen, W.; Johnson, Chad

    2010-01-01

    In other parts of the world, previous workers have shown that sparry dolomite in carbonate rocks may be produced by the generation and movement of hot basinal brines in response to arid paleoclimates and tectonism, and that some of these brines served as the transport medium for metals fixed in Mississippi Valley-type (MVT) and sedimentary exhalative (Sedex) deposits of Zn, Pb, Ag, Au, or barite. Numerous occurrences of hydrothermal zebra dolomite (HZD), comprised of alternating layers of dark replacement and light void-filling sparry or saddle dolomite, are present in Paleozoic platform and slope carbonate rocks on the eastern side of the Great Basin physiographic province. Locally, it is associated with mineral deposits of barite, Ag-Pb-Zn, and Au. In this paper the spatial distribution of HZD occurrences, their stratigraphic position, morphological characteristics, textures and zoning, and chemical and stable isotopic compositions were determined to improve understanding of their age, origin, and relation to dolostone, ore deposits, and the tectonic evolution of the Great Basin. In northern and central Nevada, HZD is coeval and cogenetic with Late Devonian and Early Mississippian Sedex Au, Zn, and barite deposits and may be related to Late Ordovician Sedex barite deposits. In southern Nevada and southwest California, it is cogenetic with small MVT Ag-Pb-Zn deposits in rocks as young as Early Mississippian. Over Paleozoic time, the Great Basin was at equatorial paleolatitudes with episodes of arid paleoclimates. Several occurrences of HZD are crosscut by Mesozoic or Cenozoic intrusions, and some host younger pluton-related polymetallic replacement and Carlin-type gold deposits. The distribution of HZD in space (carbonate platform, margin, and slope) and stratigraphy (Late Neoproterozoic Ediacaran-Mississippian) roughly parallels that of dolostone and both are prevalent in Devonian strata. Stratabound HZD is best developed in Ediacaran and Cambrian units, whereas

  11. Evidence for metasomatic mantle carbonatitic magma extrusion in Mesoproterozoic ore-hosting dolomite rocks in the middle Kunyang rift, central Yunnan, China

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The Kunyang rift lying on the western margin of the Yangtze platform is a rare Precambrian Fe-Cu mineralization zone. Wuding- Lufeng basin that is an important part of the zone is located on the west edge in the middle of the rift. The most important ore-hosting rocks are Mesoproterozoic dolomite rocks in the basin controlled by a ring fracture system, which is a fundamental structure of the basin. Plenty of silicate minerals and acicular apatite, feldspar phenocrysts and small vesicular, flown line and flown plane structures, melt inclusion and high temperature fluid inclusion found in most ore-hosting dolomites suggest that this kind of rocks could not be sedimentary dolomite, marble or hydrothermal carbonate rocks. The Zr/Hf and Nb/Ta values of the rocks are identical with those of associated mantle-derived rocks, and vary widely. For the monomineral dolomite, δ18OSMOW‰=+5.99 to +18.4 and δ13CPDB‰=-3.01to+0.94, which fall within the range for all carbonatitic volcanic rocks of the world. As for the accessory minerals, the values of δ18OSMOW‰ of magnetite (=+3.47 to +5.99%0) are close to that of the mantle (<5.7%), and the δ34S‰ values of sulfides (-5.09 to+5.78, averaging+1.50) are close to that of meteorite. For all the ore-bearing dolomite rocks, εNd = +0.19 to +2.27, and the calculated Isr = 0.699143, while for the associated mantle-derived rocks, εNd = +3.18 to +3.72. All the data suggest that the mineral assemblage is not only igneous but also of metasomatic mantle origin. And the presence of acicular apatite indicates that the rocks were formed by magma rapidly cooling. And the phenocryst texture and vesicular, flown and ropy and pyroclastic structures suggest that the igneous rocks were extrusive. Therefore, the ore-bearing dolomite rocks are carbonatitic volcanic rocks. This conclusion implies that most iron and copper ore deposits hosted in the dolomite rocks should be of the carbonatitc type.

  12. Life Expectancy of Kibbutz Members.

    Science.gov (United States)

    Leviatan, Uri; And Others

    1986-01-01

    Data are presented demonstrating that the life expectancy of kibbutz members--both men and women--is higher than that of the overall Jewish population in Israel. These data add to and support other research findings illustrating the more positive mental health and well-being found among kibbutz members than among other comparative populations.…

  13. Profile Report: ASHA Member Survey.

    Science.gov (United States)

    Weinberg, Armin D.; And Others

    1981-01-01

    The American School Health Association (ASHA) surveyed its members who were nurses to identify their needs for improved member programs and services. Recommendations include that the needs of both school-based nurses and those with administrative roles be considered independently for annual meeting programs. (JN)

  14. Life Expectancy of Kibbutz Members.

    Science.gov (United States)

    Leviatan, Uri; And Others

    1986-01-01

    Data are presented demonstrating that the life expectancy of kibbutz members--both men and women--is higher than that of the overall Jewish population in Israel. These data add to and support other research findings illustrating the more positive mental health and well-being found among kibbutz members than among other comparative populations.…

  15. 川东北盘龙洞长兴组-飞仙关组白云岩化特征及成因%Characteristics and genesis of dolomitization in Changxing and Feixianguan Formations in Panlongdong, northeastern Sichuan Basin

    Institute of Scientific and Technical Information of China (English)

    陈琪; 胡文碹; 李庆; 朱井泉

    2012-01-01

    Systematic field investigation and thin section observation as well as electron microprobe determination reveal that dolomitization is common in the Changing and Feixianguan formations in Panlongdong, northeastern Sichuan Basin. Various types of dolomites are developed and distributed vertically in obvious zonation. From bottom to top, they are biological clasitic dolomite, reef dolomite, crystalline dolomite, oolitic dolomite and micrite dolomite respectively. Our study showed that three genetic models could account for the formation process of the dolomites, including mixed-water dolomitization, infiltration and circumfluence dolomitization as well as penecon-temporaneous dolomitization. The biological clasitic and reef dolomites were mainly formed through the mixed-water dolomitization,which occurred in relatively open diagenesis environment with meteoric water input. These dolomites had different δ13C values and more negative δ18O values and remained original sedimentary structure of rocks which restricted dolomitization. The infiltration and circumfluence dolomitization resulted in the formation of the crystalline and oolitic dolomites which have same δ13C values,less negative δ18O valuse,Fe and Mn contents. The penecontemporaneous dolomitization created the micrite dolomite with tight lithology and less negative δ13C and δ18O values.%通过系统的野外调查和薄片鉴定,结合电子探针分析,认为四川盆地东北部盘龙洞长兴组-飞仙关组地层普遍发生白云岩化作用.不同类型的白云岩较发育,在纵向分布上具明显的分带性,由下至上依次为:生屑(含砂砾屑)白云岩、礁白云岩、结晶白云岩、鲕粒白云岩和泥-微晶白云岩.进一步研究表明,上述白云岩的成因模式主要有三种,即混合水白云岩化、渗透回流白云岩化和准同生白云岩化.混合水白云岩化为生屑(含砂砾屑)白云岩和礁白云岩的主要形成模式,这两类白云岩保持了岩石

  16. Nano-scale zero valent iron transport in a variable aperture dolomite fracture and a glass fracture

    Science.gov (United States)

    Mondal, P.; Sleep, B. E.; Cui, Z.; Zhou, Z.

    2014-12-01

    Experiments and numerical simulations are being performed to understand the transport behavior of carboxymethyl cellulose polymer stabilized nano-scale zero valent iron (nZVI) in a variable aperture dolomite rock fracture and a variable aperture glass replica of a fractured slate. The rock fracture was prepared by artificially inducing a fracture in a dolomite block along a stylolite, and the glass fracture was prepared by creating molds with melted glass on two opposing sides of a fractured slate rock block. Both of the fractures were 0.28 m in length and 0.21 m in width. Equivalent hydraulic apertures are about 110 microns for the rock fracture and 250 microns for the glass replica fracture. Sodium bromide and lissamine green B (LGB) serve as conservative tracers in the rock fracture and glass replica fracture, respectively. A dark box set-up with a light source and digital camera is being used to visualize the LGB and CMC-nZVI movement in the glass fracture. Experiments are being performed to determine the effects of water specific discharge and CMC concentration on nZVI transport in the fractures. Transmission electron microscopy, dynamic light scattering, and UV-visual spectrophotometry were performed to determine the stability and characteristics of the CMC-nZVI mixture. The transport of bromide, LGB, CMC, and CMC-nZVI in both fractures is being evaluated through analysis of the effluent concentrations. Time-lapse images are also being captured for the glass fracture. Bromide, LGB, and CMC recoveries have exceeded 95% in both fractures. Significant channeling has been observed in the fractures for CMC transport due to viscous effects.

  17. Modeling Solute Diffusion in the Presence of Pore-Scale Heterogeneity

    Energy Technology Data Exchange (ETDEWEB)

    FLEMING,SEAN W.; HAGGERTY,ROY

    1999-10-21

    A range of pore diffusivities, D{sub p}, is implied by the high degree of pore-scale heterogeneity observed in core samples of the Culebra (dolomite) Member of the Rustler formation, NM. Earlier tracer tests in the culebra at the field-scale have confirmed significant heterogeneity in diffusion rate coefficients (the combination of D{sub p} and matrix block size). In this study, expressions for solute diffusion in the presence of multiple simultaneous matrix diffusivities are presented and used to model data from eight laboratory-scale diffusion experiments performed on five Culebra samples. A lognormal distribution of D{sub p} is assumed within each of the lab samples. The estimated standard deviation ({sigma}{sub d}) of In(D{sub p}) within each sample ranges from 0 to 1, with most values lying between 0.5 and 1. The variability over all samples leads to a combined {sigma}{sub d} in the range of 1.0 to 1.2, which appears to be consistent with a best-fit statistical distribution of formation factor measurements for similar Culebra samples. A comparison of the estimation results to other rock properties suggests that, at the lab-scale, the geometric mean of D{sub p} increases with bulk porosity and the quantity of macroscopic features such as vugs and fractures. However, {sigma}{sub d} appears to be determined by variability within such macroscopic features and/or by micropore-scale heterogeneity. In addition, comparison of these experiments to those at larger spatial scales suggests that increasing sample volume results in an increase in {sigma}{sub d}.

  18. The Summary on Exploration of the Dolomite Oilfields in the World%世界白云岩油气田勘探综述

    Institute of Scientific and Technical Information of China (English)

    马锋; 杨柳明; 顾家裕; 陈曦; 赵喆; 金银楠; 高力

    2011-01-01

    利用C&C数据库的"数字化类比知识系统",对世界上137个白云岩油气藏勘探数据进行统计研究,分析全球白云岩油气田分布规律、形成的构造背景、发育的盆地类型、赋存的沉积环境及主要产层的时代,并进而分析全球已发现白云岩油气田的油气产量与它们的关系;白云岩油气田以陆上为主,主要分布在北美洲,构造背景以缝合带边缘的前陆盆地为主,其产层主要分布在古生代和中生代,在萨布哈潮坪环境下,更容易发现白云岩气田,而在前缘斜坡和深水盆地环境下,以白云岩油田为主,高能碳酸盐砂和生物建造环境下以凝析气田为主。通过对这些油气田白云岩储集层储集空间的分析及孔、渗数据的研究,揭示白云岩优质储层主要受白云石化作用、溶蚀作用和裂缝化作用控制,沉积环境控制了白云石化作用和溶蚀作用的发生,而构造背景则与裂缝的发育相关;其盖层受白云石化环境的控制,主要以海相页岩和蒸发岩为主。%By analyzing the data of the 137 dolomite reservoirs in the world with the C&C digital analogs knowledge system,the location of the oilfields,the structural setting,the type of basin,the depositional environment and the age of the dolomite strata were all investigated researched.The target is to find the relation between the production and these elements mentioned above.The geographical distribution of the dolomite fields are not evenly.Most of the dolomite fields were onshore oilfield,mainly distribute on the North America,Asia and Europe.The plate tectonics controlled these distribution: most of them have been discovered in compressional basins,especially in the suture belt,such as foreland basin and so on,but few dolomite fields can be found in the rift basin or the passive continental margin.The oil and gas accumulated in the Mesozoic and Paleozoic,mainly from the Cretaceous and Triassic.The next major

  19. Empirical Calibration for Dolomite Stoichiometry Calculation: Application on Triassic Muschelkalk- Lettenkohle Carbonates (French Jura Calibration empirique pour le calcul de la stoechiométrie de la dolomite : application aux carbonates triasiques du Muschelkalk-Lettenkohle (Jura français

    Directory of Open Access Journals (Sweden)

    Turpin M.

    2012-02-01

    Full Text Available This study concerns an approach for dolomite quantification and stoichiometry calculation by using X-ray diffractometry coupled with cell and Rietveld refinements and equipped with a newly substantial database of dolomite composition. A greater accuracy and precision are obtained for quantifying dolomite as well as other mineral phases and calculating dolomite stoichiometry compared to the classical “Lumsden line” and previous methods. The applicability of this approach is verified on dolomite reference material (Eugui and on Triassic (Upper Muschelkalk-Lettenkohle carbonates from the French Jura. The approach shown here is applicable to bulk dolostones as well as to specific dolomite cements and was combined with petrographical and isotopic analyses. Upper Muschelkalk dolomites were formed during burial dolomitization under fluids characterized by increased temperature and variable isotopic composition through burial. This is clear from their Ca content in dolomites which gradually approaches an ideal stoichiometry (from 53.16% to 51.19% through increasing dolomitization. Lettenkohle dolostones consist of near-ideal stoichiometric (51.06%Ca and well-ordered dolomites associated with anhydrite relicts. They originated through both sabkha and burial dolomitization. This contribution gives an improved method for the characterization of different dolomite types and their distinct traits in sedimentary rocks, which allows a better evaluation of their reservoir potential. Cette étude propose une approche pour la quantification de la dolomite et le calcul de sa stoechiométrie grâce à l’utilisation de la diffraction des rayons X couplée aux affinements de maille et de Rietveld et complétée par de nombreuses données issues de la littérature. Elle permet d’obtenir une meilleure justesse et précision pour la quantification de la dolomite (et des autres phases minérales ainsi que pour le calcul de sa stoechiométrie par rapport à l

  20. Establishing the Relationship between Fracture-Related Dolomite and Primary Rock Fabric on the Distribution of Reservoirs in the Michigan Basin

    Energy Technology Data Exchange (ETDEWEB)

    G. Michael Grammer

    2006-09-30

    This topical report covers the year 2 of the subject 3-year grant, evaluating the relationship between fracture-related dolomite and dolomite constrained by primary rock fabric in the 3 most prolific reservoir intervals in the Michigan Basin (Ordovician Trenton-Black River Formations; Silurian Niagara Group; and the Devonian Dundee Formation). The characterization of select dolomite reservoirs has been the major focus of our efforts in Phase II/Year 2. Fields have been prioritized based upon the availability of rock data for interpretation of depositional environments, fracture density and distribution as well as thin section, geochemical, and petrophysical analyses. Structural mapping and log analysis in the Dundee (Devonian) and Trenton/Black River (Ordovician) suggest a close spatial relationship among gross dolomite distribution and regional-scale, wrench fault related NW-SE and NE-SW structural trends. A high temperature origin for much of the dolomite in the 3 studied intervals (based upon initial fluid inclusion homogenization temperatures and stable isotopic analyses,) coupled with persistent association of this dolomite in reservoirs coincident with wrench fault-related features, is strong evidence for these reservoirs being influenced by hydrothermal dolomitization. For the Niagaran (Silurian), a comprehensive high resolution sequence stratigraphic framework has been developed for a pinnacle reef in the northern reef trend where we had 100% core coverage throughout the reef section. Major findings to date are that facies types, when analyzed at a detailed level, have direct links to reservoir porosity and permeability in these dolomites. This pattern is consistent with our original hypothesis of primary facies control on dolomitization and resulting reservoir quality at some level. The identification of distinct and predictable vertical stacking patterns within a hierarchical sequence and cycle framework provides a high degree of confidence at this point

  1. Genesis and Distribution of the Cambro-Ordovician Dolomite in Tarim Basin%塔里木盆地寒武-奥陶系白云岩成因及分布规律

    Institute of Scientific and Technical Information of China (English)

    郑剑锋; 沈安江; 刘永福; 陈永权

    2011-01-01

    塔里木盆地寒武-奥陶系发育的白云岩主要有4种成因,分别对应萨布哈、渗透回流、埋藏、热液等4种白云石化模式,根据岩石学和地球化学特征可以较好地识别出这4种白云岩。综合分析古地理、古气候等背景资料,总结了塔里木盆地不同成因白云岩在垂向及平面上的分布规律:萨布哈白云岩和渗透回流白云岩的发育受沉积相控制,主要发育于中下寒武统;埋藏白云岩的发育受成岩相控制,物性好的台缘、台内礁滩体及有裂缝沟通构成的开放体系最容易先发生埋藏白云石化作用;热液白云岩主要发育在具有上覆隔挡层的不整合面之下地层及大断裂发育带附近。%The dolomites of Cambro-Ordovician in Tarim basin are of four geneses,corresponding with four kinds of dolomitization ones such as sabakha dolomite,seepage reflux dolomite,buried dolomite and hydrothermal dolomite,which can be properly identified from the lithologic characteristics and geochemical characteristics.This paper comprehensively analyzes the paleogeographic and paleoclimate data,concludes the vertical and lateral distributions of dolomites with different geneses in Tarim basin: the development of sabakha dolomite and seepage reflux dolomite are controlled by sedimentary facies and mainly developed in Lower-Middle Cambrian;the development of burial dolomite are controlled by diagenetic facies,but the reef and shoal with high porosity as well as open system connected with fracture passage are easy to dolomitize;hydrothermal dolomite mainly develops below unconformity and near the discordogenic fault.

  2. Characteristics and Formation Mechanism for Dolomite Reservoir of Permian Fengcheng Formation in Junggar Basin%准噶尔盆地二叠系风城组白云岩储层特征及成因机理分析

    Institute of Scientific and Technical Information of China (English)

    薛晶晶; 孙靖; 朱筱敏; 刘巍; 朱世发

    2012-01-01

    Recently, dolomitic-rock exploration of Junggar Basin has made a sustained breakthrough and opened a completely new exploration field. Definition of dolomitic-rock is concluded, and the effective reservoir type, characteristics of occurrence and formation mechanism of dolomite are determined based on previous research conclusions, core observation, thin section, and so on. The dolomitic-rock with special lithology and limited distribution mainly develops in Permian Fengcheng Formation of Wuxia district of the northwest margin. The dolomite has seven types of occurrence, including lameltate, uniform distribution, snow shape, irregular layered shape, crumb shape, fracture filling shape and exotic dolomite elastics. Corresponding, dolomite has five types of formation mechanism, including para-syngenetic dolomitization, mixed dolomitization, buried dolo-mitization, diagenetic dolomitization and weathering-transportation of external dolostone. The effective dolomitic-rock reservoirs whose space is microfissure, include dolomitic-siltstone, dolomitic-mudstone, muddy dolomite, and so on. Development degree and dispositional relationship of fissure and karst cave have an important impact on the level of capacity. Overall, the micro-and macro-distribution characteristics of different types of dolomite are different, and their superimposed effect controls the whole features of the present dolomite.%准噶尔盆地云质岩勘探近年来持续获得重大突破,打开了全新的勘探领域.通过岩心观察、薄片观察和分析等方法,结合前人研究成果,初步归纳了盆地云质岩的定义,明确有效储集岩类型及其产出特征和成因机理.云质岩具有岩性独特和分布局限的特点,主要产出于西北缘乌夏地区二叠系风城组.研究表明,盆地白云岩有纹层状、均匀分布状和雪花状等7种产出类型,共有准同生白云化作用、混合白云化作用和埋藏白云化作用等5种成因机理.风城组有效云

  3. 全氟物改性煅白的防吸湿机理%Anti-moisture mechanism of calcined dolomite modified by perfluoroalkylethyl acrylate

    Institute of Scientific and Technical Information of China (English)

    梁晓波; 李明照; 王国卫; 梁一然; 张耀斌; 毛嘉; 任川兮

    2015-01-01

    对煅白表面锚固偶氮二氰基戊酸引发全氟烷基乙基丙烯酸酯(FM)聚合而制备的防吸湿煅白进行研究,利用 XPS、IR、DSC、TG、SEM 物理吸收和接触角测量等方法对改性前后煅白的结构、比表面积、形貌和疏水接触角等进行表征,并分析改性后煅白吸湿性降低的原因和机理。结果表明:煅白表面发生了偶联、锚固及聚合反应。锚固引发剂的煅白引发FM原位分散聚合而制得防吸湿煅白,其吸湿率随FM质量分数的增加而降低,当FM质量分数达到7%时,吸湿率不再下降,改性后煅白1 h的吸湿率由1.39%下降到0.017%;聚全氟烷基乙基丙烯酸酯(PFM)的接枝率为0.5%、接枝效率为26.6%,煅白表面出现一层连续而完整的全氟聚合物膜,其厚度约为8 nm。%4,4'-Azobis(4-cyanovaleric acid) (ACPA) was anchored onto the surface of calcined dolomite and radical graft polymerization of perfluoroalkylethyl acrylate (FM) from the modified calcined dolomite through dispersion polymerization were investigated. The structure, specific surface area, morphology and hydrophobic contact angle of calcined dolomite surface were characterised by XPS, IR, DSC, TG, SEM, physical absorption and contact angle measurement, and the reason and mechanism on the decreasing the moisture absorption rate of calcined dolomite after the modification were studied. The results show that the coupling, anchoring and polymerization reactions happen on the surface of calcined dolomite. Poly (Perfluoroalkylethyl acrylate) (PFM) is effectively grafted onto calcined dolomite through the initiation of anchored ACPA during in-situ dispersion polymerization. It shows that the moisture absorption rate of calcined dolomite decreases with increasing of the mass fraction of FM. When the mass fraction of FM is 7%, The moisture absorption rate decreases from 1.39% to 0.017% after modification for 1 h. The grafting rate and efficiency of PFA are 0.5% and

  4. Effect of H{sub 2}S on the catalytic decomposition of tar and ammonia with dolomite and sintered iron ore in synthetic gasification gas

    Energy Technology Data Exchange (ETDEWEB)

    Hepola, J. [VTT Energy, Espoo (Finland)

    1996-12-31

    The toluene-decomposing activity of calcined dolomite was not affected by the H{sub 2}S content of synthetic gasification gas. Iron was active with respect to toluene and ammonia at metallic state. The increase of the H{sub 2}S content of synthetic gasification gas (0 - 500 ppmv) decreased the tar-decomposing activity but not the ammonia- decomposing activity of sintered iron ore. (author) (12 refs.)

  5. Atmospheric circulation patterns, cloud-to-ground lightning, and locally intense convective rainfall associated with debris flow initiation in the Dolomite Alps of northeastern Italy

    OpenAIRE

    Underwood, S. Jeffrey; Schultz, Michael D.; Berti, Metteo; Gregoretti, Carlo; Simoni, Alessandro; Mote, Thomas L.; Saylor, Anthony M.

    2016-01-01

    The Dolomite Alps of northeastern Italy experience debris flows with great frequency during the summer months. An ample supply of unconsolidated material on steep slopes and a summer season climate regime characterized by recurrent thunderstorms combine to produce an abundance of these destructive hydro-geologic events. In the past, debris flow events have been studied primarily in the context of their geologic and geomorphic characteristics. The atmospheric contribution to ...

  6. Atmospheric circulation patterns, cloud-to-ground lightning, and locally intense convective rainfall associated with debris flow initiation in the Dolomite Alps of northeastern Italy

    OpenAIRE

    S. J. Underwood; Schultz, M D; Berti, M; C. Gregoretti; Simoni, A.; T. L. Mote; A. M. Saylor

    2015-01-01

    The Dolomite Alps of northeastern Italy experience debris flows with great frequency during the summer months. An ample supply of unconsolidated material on steep slopes and a summer season climate regime characterized by recurrent thunderstorms combine to produce an abundance of these destructive hydrogeologic events. In the past debris flow events have been studied primarily in the context of their geologic and geomorphic characteristics. The atmospheric contribution to th...

  7. Abiotically-formed, primary dolomite in the mid-Eocene lacustrine succession at Gebel El-Goza El-Hamra, NE Egypt: An approach to the role of smectitic clays

    Science.gov (United States)

    Wanas, H. A.; Sallam, E.

    2016-08-01

    This study discusses the role of smectitic clays in the formation of an abiotic (physio-chemical) primary dolomite within an evaporative alkaline-saline marginal lake system, in the absence of carbonate precursor and microbes. The present work has been achieved in terms of textural, mineralogical, and geochemical characteristics of dolostones in the Mid-Eocene (Bartonian) lacustrine succession cropping out at Gebel El-Goza El-Hamra (Shabrawet area, NE Egypt). This lacustrine succession is 15-16 m thick, and made up of alternating horizontal beds of dolostone, marlstone and mudrock that show some pedogenic and subaerial exposure features. The dolostones are composed mainly of dolomite (60-90%), smectite (20-30%) and quartz grains (5-10%). The dolomite comprises fine-crystalline rhombs to micro-spherical crystals with no obvious relics of microbial activity and/or carbonate precursor. It is, ordered, nearly stoichiometric (with 46-50% mole of MgCO3) and has δ18O and δ13C values ranging from + 0.44 to + 2.96 VPDB ‰, and 0.93 to - 8.95 VPDB ‰, respectively. The smectite occurs as thin mats that are commonly intergrown and associated with dolomite. Mineralogical, textural and stable isotopic results of the dolomite indicated that the dolomite was formed as an abiotic primary precipitate in alkaline saline lacustrine systems. In this respect, the gel-like highly viscous smectitic medium plus progressive CO2 degassing, elevated evaporation, low sedimentation rate, low sulphates level and alkaline soil solution lowered the kinetic barriers of dolomite precipitation from solution and promoted the incorporation of Mg2 + in the structure of dolomite. Consequently, the presence of smectitic clays in evaporative saline lakes is significant for dolomite formation because they can generate a gel-like highly viscous medium and provide Mg2 + that can facilitate the physcio-chemical precipitation of primary dolomite from solution at ambient temperatures. However, more work is

  8. Removal of SO2 with particles of dolomite limestone powder in a binary fluidized bed reactor with bubbling fluidization

    Directory of Open Access Journals (Sweden)

    R. Pisani Jr.

    2003-06-01

    Full Text Available In this work, SO2 was treated by reaction with dolomite limestone (24 µm in a fluidized bed reactor composed of 500-590 µm sand particles. The influence of operating temperature (500, 600, 700 and 800ºC, superficial gas velocity (0.8, 1.0 and 1.2 m/s and Ca/S molar ratio (1, 2 and 3 on SO2 removal efficiency for an inlet concentration of 1000 ppm was examined. Removal of the pollutant was found to be dependent on temperature and Ca/S molar ratio, particularly at 700 and 800ºC. A maximum removal of 76% was achieved at a velocity of 0.8 m/s, a temperature of 800°C and a Ca/S of 3. The main residence time of the powder particles was determined by integrating normalized gas concentration curves as a function of time; the values found ranged from 4.1 to 14.4 min. It was concluded that the reactor operated in bubbling fluidization under every operational condition.

  9. Dynamics and structure of natural regeneration in three high elevation LTER area in the Dolomites (North-Eastern Alps, Italy

    Directory of Open Access Journals (Sweden)

    Soraruf L

    2007-01-01

    Full Text Available Regeneration structures and spatial patterns of European larch (Larix decidua Miller, Swiss stone pine (Pinus cembra L. and Norway spruce (Picea abies (L. Karst., were analyzed in three high elevation LTER area in the Dolomites (North-Eastern Alps. Larch and spruce regeneration is mainly affected by dense forest cover and grasses competition whereas stone pine is mostly sensitive to late snow melting, fungal diseases and wild ungulate damages. The current stand and regeneration structure suggests that larch has been highly fostered in the past due to silvo-pastoral management practices. All species show a clear tendency to spatial intraspecific aggregation especially at short-distances. The spatial patterns of larch regeneration are more complex than the other two species, more heavily affected by a main factor such as the nutcracker (Nucifraga caryocatactes L. seed dispersal for stone pine or presence of canopy gaps for spruce. However, spatial patterns of all species depend on the number of the available microsites, that often match at small distance driving the formation of small mixed and unevenaged patches. Combining the age structure and spatial pattern information we were able to better understand the small-scale patterns and processes and the role of the past disturbances on the regeneration dynamics in space and time.

  10. Tracer Tests in a Fractured Dolomite: 3. Analysis of Mass Transfer in Single-Well Injection-Withdrawal Tests

    Energy Technology Data Exchange (ETDEWEB)

    Haggerty, R.; Fleming, S.W.; Meigs, L.C.; McKenna, S.A.

    1999-03-04

    We investigated multiple-rate diffusion as a possible explanation for observed behavior in a suite of single-well injection-withdrawal (SWIW) tests conducted in a fractured dolomite. We first investigated the ability of a conventional double-porosity model and a multirate diffusion model to explain the data. This revealed that the multirate diffusion hypothesis/model is most consistent with all available data, and is the only model to date that is capable of matching each of the recovery curves entirely. Second, we studied the sensitivity of the SWIW recovery curves to the distribution of diffusion rate coefficients and other parameters. We concluded that the SWIW test is very sensitive to the distribution of rate coefficients, but is relatively insensitive to other flow and transport parameters such as advective porosity and dispersivity. Third, we examined the significance of the constant double-log late-time slopes ({minus}2. 1 to {minus}2.8), which are present in several data sets. The observed late-time slopes are significantly different than would be predicted by either conventional double-porosity or single-porosity media, and are found to be a distinctive feature of multirate diffusion under SWIW test conditions. Fourth, we found that the estimated distributions of diffusion rate coefficients are very broad, with the distributions spanning a range of at least 3.6 to 5.7 orders of magnitude.

  11. Organic carbon isotope values from the Late Permian Seis/Siusi succession (Dolomites, Italy: Implications for palaeoenvironmental changes

    Directory of Open Access Journals (Sweden)

    S. Siegert

    2011-08-01

    Full Text Available The Permian-Triassic boundary is marked by a globally prominent negative carbon isotope excursion traceable in marine carbonates and organic matter. In the shallow marine carbonate succession at Seis/Siusi (Dolomites, Italy, the δ13Ccarb and δ13Corg signatures follow the general Permian-Triassic boundary carbon isotope trend, but the δ13Corg values are slightly less depleted in 13C in two episodes representing restricted lagoonal environments and in the period around the Tesero Oolite Horizon. This isotopically less depleted organic matter in the lagoons is interpreted to be most likely caused by poor oxygen ventilation and/or slightly modified salinity which may have led to restricted bioproductivity and increased hence the relative amounts of continental-sourced organic matter. In addition, elevated riverine influx and supply of terrestrial organic matter, perhaps triggered by a wet period, might be the cause for the relatively less depleted 13C in the organic matter around the Tesero Oolite Horizon and in overlying sediments. doi:10.1002/mmng.201100008

  12. Infiltration and hydraulic connections from the Niagara River to a fractured-dolomite aquifer in Niagara Falls, New York

    Science.gov (United States)

    Yager, Richard M.; Kappel, William M.

    1998-04-01

    The spatial distribution of hydrogen and oxygen stable-isotope values in groundwater can be used to distinguish different sources of recharge and to trace groundwater flow directions from recharge boundaries. This method can be particularly useful in fractured-rock settings where multiple lines of evidence are required to delineate preferential flow paths that result from heterogeneity within fracture zones. Flow paths delineated with stable isotopes can be combined with hydraulic data to form a more complete picture of the groundwater flow system. In this study values of δD and δ 18O were used to delineate paths of river-water infiltration into the Lockport Group, a fractured dolomite aquifer, and to compute the percentage of river water in groundwater samples from shallow bedrock wells. Flow paths were correlated with areas of high hydraulic diffusivity in the shallow bedrock that were delineated from water-level fluctuations induced by diurnal stage fluctuations in man-made hydraulic structures. Flow paths delineated with the stable-isotope and hydraulic data suggest that river infiltration reaches an unlined storm sewer in the bedrock through a drainage system that surrounds carrying river water to hydroelectric power plants. This findings is significant because the storm sewer is the discharge point for contaminated groundwater from several chemical waste-disposal sites and the cost of treating the storm sewer's discharge could be reduced if the volume of infiltration from the river were decreased.

  13. Dolomitization of carbonated reservoirs of platforms. From geologic data to modeling. Example of the great Bahama bank; La dolomitisation des reservoirs carbonates de plate-forme. Des donnees geologiques a la modelisation. Exemple du Grand Banc des Bahamas

    Energy Technology Data Exchange (ETDEWEB)

    Caspard, E.

    2002-09-01

    Dolomitization has long been one of the most studied geological processes because of its economic interest (dolomitic rocks form a significant share of hydrocarbon reservoirs) as well as its academic interest, based on the fact that dolomite scarcely forms in current and recent marine environments whereas seawater is highly over-saturated; and that it is still not possible to synthesize it in laboratory under the same conditions. We used data collected by the University of Miami (Bahamas Drilling Project, ODP Leg 166) to understand the geological context of complete dolomitization of a Messinian 60 m thick reef unit. Classical methods of petrographic analysis of thin sections (optical microscopy, cathodoluminescence, scanning electron microscopy, in situ isotopic analyze using ionic microprobe) showed that the intensity of dolomitization is not controlled by the initial texture of the sediment, that the key parameter for dolomitization is the conservation of the initial mineralogy of magnesian bio-clasts, and that redox conditions, salinity and/or temperature of the precipitation fluid varied significantly during the process. Hydrodynamic modelling showed that during periods of high sea-level, Kohout thermal convection is a viable mechanism for driving marine fluids through the sediments. The key parameter for fluid circulations is the permeability anisotropy on the platform scale. Geochemical modelling showed that seawater is able to induce a complete dolomitization over durations of around one million years. Sensitivity tests showed that the critical parameter (as well as one of the less well-known) to describe diagenetic processes in carbonates is the water/rock reactions kinetics and in particular the precipitation kinetics of carbonate minerals. We finally propose that the dolomitization of the reef unit of the Unda well took place during the high sea-level period which extended over 1,1 My in the early Pliocene, according to the Kohout thermal convection

  14. 17 CFR 190.09 - Member property.

    Science.gov (United States)

    2010-04-01

    ... 17 Commodity and Securities Exchanges 1 2010-04-01 2010-04-01 false Member property. 190.09... Member property. (a) Member property. “Member property” means, in connection with a clearing organization bankruptcy, the property which may be used to pay that portion of the net equity claim of a member which...

  15. The relative merits of dolomitic and calcitic limestone in detoxifying and revegetating acidic, nickel- and copper-contaminated soils in the Sudbury mining and smelting region of Canada

    Energy Technology Data Exchange (ETDEWEB)

    McHale, D.; Winterhalder, K. [Laurentian Univ., Sudbury, Ontario (Canada)

    1996-12-31

    Soils in the Sudbury mining and smelting region have been rendered phytotoxic and barren by acidification and Particulate metal contamination, but can be detoxified revegetated by the surface application of an growth is better on soil treated ground limestone. On certain barren sites, plant growth is better on soil treated with dolomitic limestone than with calcitic limestone and greenhouse experiments using mung beans (Vigna radiata) have shown superior root and shoot growth on certain contaminated soils when the limestone is dolomitic rather than calcitic. Results of experiments with species used in revegetation (Agrostis gigantea and Lotus corniculatus) suggest that leguminous species are more sensitive to Ca:Mg ratio than grasses, that the plant response to this ratio is greater at lowering liming levels, and that the response is more marked on more toxic soils. The effects of calcium:magnesium ratio of the limestone used in revegetating acidic, metal-contaminated soils are clearly complex, interactive and difficult to interpret. Further studies are needed, but meanwhile it is recommended that the practice of using dolomitic limestone to detoxify barren Sudbury soils be continued, since there is a risk of induced magnesium deficiency at certain sites when calcitic limestone is used.

  16. The pedological heritage of the Dolomites (Northern Italy): Features, distribution and evolution of the soils, with some implications for land management

    Science.gov (United States)

    Zilioli, Diana Maria; Bini, Claudio; Wahsha, Mohammad; Ciotoli, Giancarlo

    2011-12-01

    Since 1997, the Department of Environmental Sciences of Ca' Foscari University of Venice has undertaken numerous research projects aimed at deepening understanding of pedogenic processes in the Dolomites, and at highlighting the fundamental contribution that soil science can give to the conservation of natural resources and achieve sustainable management of mountain ecosystems. A total of several hundred profiles have been described, analyzed and mapped. This paper reports the results from the analysis of pedo-environmental characters of profiles developed from different parent materials, at altitudes between 1300 m and 2900 m and in different conditions of slope, exposure and vegetation cover. Soil forming factors, landforms and land surfaces have been interpreted to understand the soil-landscape in the mapped areas and to develop a qualitative model of soil geography into the Dolomites scenery. The application of land evaluation methods in some of the investigated territories that are subjected to intensive tourist fluxes revealed some criticisms. Collected results also highlighted the high environmental heterogeneity of soils of the Dolomites.

  17. Description of Cretaceous Sedimentary Sequence of the Second and Third Member of the Qingshankou Formation Recovered by CCSD-SK-Is Borehole in Songliao Basin: Lithostratigraphy, Sedimentary Facies and Cyclic Stratigraphy

    Science.gov (United States)

    Wang, Pujun; Gao, Youfeng; Cheng, Rihui; Wang, Guodong; Wu, Heyong; Wan, Xiaoqiao; Yang, Gansheng; Wang, Zhongxing

    The second and third member of the Qingshankou Formation recovered by CCSD-SK-Is borehole (China Cretaceous Continental Scientific Drilling-SongkeI-the south borehole) is 415.61 m long and 100% of cores recovery. The age of the member corresponds approximately to the Coniacian. The sequence and process of lithology-lithofacies and cyclic stratigraphy were revealed by a detailed core description. 12 rock types and 2 kinds of sedimentary subfacies including semi-deep lake and shallow lake were recognized from the drilling core of the second and third member of the Qingshankou Formation. 10 sedimentary microfacies are present, including dolomite, marl, limestone, oil shale, semi-deep lake turbidite, volcanic ash, seismite, semi-deep lake mudstone, shallow lake mudstone, and shallow lake turbidite microfacies. The second and third member of the Qingshankou Formation represents 422 meter-scale cycles (sixth-order cycle), 130 fifth-order cycles, 21 fourth-order cycles, and one third-order cycles. The special lithologies, such as mudstone, seismite, dolomite, volcanic ash, and so on are important to researches on source rocks and lacustrine event sediments.

  18. Energy-Absorbing Beam Member

    Science.gov (United States)

    Littell, Justin D. (Inventor)

    2017-01-01

    An energy-absorbing (EA) beam member and having a cell core structure is positioned in an aircraft fuselage proximate to the floor of the aircraft. The cell core structure has a length oriented along a width of the fuselage, a width oriented along a length of the fuselage, and a depth extending away from the floor. The cell core structure also includes cell walls that collectively define a repeating conusoidal pattern of alternating respective larger and smaller first and second radii along the length of the cell core structure. The cell walls slope away from a direction of flight of the aircraft at a calibrated lean angle. An EA beam member may include the cell core structure and first and second plates along the length of the cell core structure on opposite edges of the cell material.

  19. Re-membering Eastern Europe

    DEFF Research Database (Denmark)

    Wilken, Lisanne

    2016-01-01

    Since the break-down of the Soviet Union and the inclusion of a growing number of Post-Soviet countries into the Eurovision Song Contest, the contest has become an occurring occasion for remembering and discussing the nature and limits of “Europe”. This paper explores how the inclusion of Post-So......, Ukraine and Russia in order to explore how they are re-membered in relation to various perceptions of Europe....

  20. Towards mobile staff members management

    Science.gov (United States)

    Encheva, Sylvia

    2017-07-01

    Todays project management requires a number of abilities which involve finding quick solutions to shortage of staff members with possession of specific qualities. When persons with team responsibilities are under pressure or due to various circumstances are unable to perform exhaustive search in databases, an interactive visualization tool can come in quite handy in finding good solutions unforeseen occurrences. In particular we propose application of selected graphs for facilitating mobile human resource management.

  1. ASCLS members perceptions regarding research.

    Science.gov (United States)

    Mundt, Lillian; Shanahan, Kristy

    2009-01-01

    One of the benchmarks of a profession is performing, publishing, and presenting research. However, in the Clinical Laboratory Science (CLS) profession, few manuscripts are submitted to the American Society for Clinical Laboratory Science (ASCLS) journal, Clinical Laboratory Science, on a regular basis. The problem is that perceptions regarding research, and the role of laboratory professional as researchers, held by ASCLS members may be contributing to the low number of manuscript submissions. To assess these perceptions, an anonymous Likert-scale survey was developed and delivered online using Survey Monkey. Members of ASCLS, with email addresses, were chosen to participate in this survey because they may be most likely to contribute manuscripts for a journal by their own society. About 10% of the 7,000 members who were invited by email chose to participate in this study. Most participants agreed that 1) there is important information to be gathered from research on clinical laboratory specimen results (99.6%), 2) research contributes valuable information to the body of CLS knowledge (99.2%), and 3) conducting research is one of the benchmarks of a profession (92.4%). The majority of participants felt that there are inadequate resources (68.8%) and not enough time (83%) available to conduct research in the clinical laboratory setting. Most participants recognize that many laboratory activities constitute research (86.2%), but only a few are willing to publish research findings on their own (29.2%). Those who are the most likely to publish research findings include men, university faculty, and members who are over 60 years old. University faculty are the most likely to assist others in the writing process. These results show an opportunity exists for ASCLS to foster collaborations between bench technologists and educators willing to assist with the publication process.

  2. 准噶尔盆地西北缘风城组白云岩成因及油气富集因素%Dolomites genesis and hydrocarbon enrichment of the Fengcheng Formation in the northwestern margin of Junggar Basin

    Institute of Scientific and Technical Information of China (English)

    冯有良; 张义杰; 王瑞菊; 张光亚; 吴卫安

    2011-01-01

    Using the data of cores, well logging interpretations, seismic sections and experimental geochemistry, this paper analyzes the sedimentary environment, genesis, and distribution of dolomites, as well as the hydrocarbon enrichment factors of dolomite reservoirs in the Permian Fengcheng Formation. According to attitude and structure, the dolomites of the Fengcheng Formation are divided into lamina dolomites, thin-bed dolomites, and spotted dolomites. They are mainly the penecontemporaneous and epigenetic dolomites, the former was deposited in a saline semi-deep lake, while the latter results from the dolomitization of lime mud that was deposited in a saline semi-deep lake during the diagenetic stage. The dolomites are distributed at the palaeoslopes formed by volcano eruption and movement of thrust faults and the main dolomite reservoir spaces are dissolved pores and fractures. The factors controlling hydrocarbon enrichment are fractures and structural background.%利用钻井、岩心、地震、测井及地球化学资料,分析准噶尔盆地西北缘二叠系风城组白云岩沉积环境、成因、分布规律及白云岩储集层油气富集高产因素.风城组白云岩按产状和沉积构造可分为纹层状泥质白云岩、薄层状白云岩和斑状白云岩,主要为准同生白云岩和后生白云石化白云岩.准同生白云岩形成于半深湖咸水环境;后生白云石化白云岩是发育在半深湖咸水环境下的碳酸盐岩灰泥在成岩期经后生白云石化作用形成.白云岩主要分布在火山喷发或逆冲断裂活动形成的古地貌斜坡上.白云岩储集层的储集空间主要为溶蚀孔隙和裂隙.白云岩储集层富集高产的控制因素是裂缝及构造背景.

  3. Summary of Research through Phase II/Year 2 of Initially Approved 3 Phase/3 Year Project - Establishing the Relationship between Fracture-Related Dolomite and Primary Rock Fabric on the Distribution of Reservoirs in the Michigan Basin

    Energy Technology Data Exchange (ETDEWEB)

    G. Grammer

    2007-09-30

    This final scientific/technical report covers the first 2 years (Phases I and II of an originally planned 3 Year/3 Phase program). The project was focused on evaluating the relationship between fracture-related dolomite and dolomite constrained by primary rock fabric in the 3 most prolific reservoir intervals in the Michigan Basin. The characterization of select dolomite reservoirs was the major focus of our efforts in Phases I and II of the project. Structural mapping and log analysis in the Dundee (Devonian) and Trenton/Black River (Ordovician) suggest a close spatial relationship among gross dolomite distribution and regional-scale, wrench fault-related NW-SE and NE-SW structural trends. A high temperature origin for much of the dolomite in these 2 studied intervals (based upon fluid inclusion homogenization temperatures and stable isotopic analyses,) coupled with persistent association of this dolomite in reservoirs coincident with wrench fault-related features, is strong evidence for these reservoirs being influenced by hydrothermal dolomitization. In the Niagaran (Silurian), there is a general trend of increasing dolomitization shelfward, with limestone predominant in more basinward positions. A major finding is that facies types, when analyzed at a detailed level, are directly related to reservoir porosity and permeability in these dolomites which increases the predictability of reservoir quality in these units. This pattern is consistent with our original hypothesis of primary facies control on dolomitization and resulting reservoir quality at some level. The identification of distinct and predictable vertical stacking patterns within a hierarchical sequence and cycle framework provides a high degree of confidence at this point that the results should be exportable throughout the basin. Much of the data synthesis and modeling for the project was scheduled to be part of Year 3/Phase III, but the discontinuation of funding after Year 2 precluded those efforts

  4. Toothbrush contamination in family members

    Directory of Open Access Journals (Sweden)

    Adolfo Contreras

    2010-04-01

    Full Text Available Objective: The purpose of this study was to determine the bacterial contamination of toothbrushes in family members. Materials and Methods: One hundred and two healthy subjects were included in this descriptive study. Every individual was examined clinically and microbiologically using the CPITN index and collecting subgingival plaque samples. Each participant received a toothbrush for home use and after one month they returned it to the investigators. All toothbrushes were cultured to determine the presence of periodontopathic bacteria and enteric rods. Wilkoxon signed rank test and t student test (P d"0.05 were used to compare differences in the subgingival microbiota and toothbrush contamination and CPITN index among family members. Results: A high proportion of toothbrushes resulted highly contaminated with enteric rods (P d"0.001 compared to the subgingival environment where periodontopathic bacteria were more prevalent. The most frequent microorganisms found in toothbrushes used by parents and children for one month were Enterobacteriaceae, Pseudomonadaceae species (>50% and Fusobacterium spp (30%. Conclusions: High levels of enteric rods were commonly detected in toothbrushes used for 1 month among members of the families. These opportunistic organisms may have an important role in oral infections including gingivitis and periodontitis. Monthly replacement or disinfection of the toothbrush can reduce the risk of bacterial transmission/translocation and thus diminish the incidence of biofilm associated oral diseases.

  5. Facies development and paleoenvironment of the Hajajah Limestone Member, Aruma Formation, central Saudi Arabia

    Science.gov (United States)

    El-Sorogy, Abdelbaset S.; Ismail, Abdelmoneim; Youssef, Mohamed; Nour, Hamdy

    2016-12-01

    The Campanian Hajajah Limestone Member of the Aruma Formation was formed during two regressive episodes. Each of them formed of three depositional facies, from base to top: 1) intra-shelf basin facies, made up of fossiliferous green shale and mudstone with ostracods and badly preserved foraminifers. 2) fore-reef facies, consists of hard, massive, marly coralline limestone. The upper part is rich with low divers, badly to moderate preserved, solitary and colonial corals, and, 3) back reef and near-shore facies, consists of fossiliferous sandy dolomitized, bioturbated limestone with abundant reworked corals, bivalves, gastropods, and aggregate grains. On the basis of field observations, micro-and macrofossils and microfacies analysis, the Hajajah Limestone Member was deposited in distal marine settings below storm wave base in a low-energy environment changed upward to fore-reef framework in an open marine environment with moderate to high energy conditions and terminated with shallow marine facies with accumulation of skeletal grains by storms during regression.

  6. 7 CFR 983.42 - Initial members and nomination of successor members.

    Science.gov (United States)

    2010-01-01

    ... members and nomination of successor members. Nomination of committee members and alternates shall follow...) Successor members. Subsequent to the first nomination of committee members under this part, persons to be nominated to serve on the committee as producer or handler members shall be selected pursuant to...

  7. 7 CFR 930.28 - Alternate members.

    Science.gov (United States)

    2010-01-01

    ... Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements... alternate member may not act in the place and stead of such member. In the event a member and his or her... group (grower or handler) as the member. In the event of the death, removal, resignation...

  8. 7 CFR 929.27 - Alternate members.

    Science.gov (United States)

    2010-01-01

    ... Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements... absence of such member and may perform such other duties as assigned. In the event of the death, removal... member is selected and has qualified. In the event both a member and alternate member from the...

  9. Geohydrology of the proposed Waste Isolation Pilot Plant site, Los Medanos area, southeastern New Mexico

    Science.gov (United States)

    Mercer, Jerry W.

    1983-01-01

    Geohydrologic data have been collected in the Los Medanos area at the U.S. Department of Energy 's proposed Waste Isolation Pilot Plant (WIPP) site in southeastern New Mexico since 1975 as part of an intensive study evaluating the feasibility of storing defense-associated nuclear wastes within the bedded salt of the Salado Formation of Permian age. Drilling and hydrologic testing have identified three principal water-producing zones above the salt, including the Rustler-Salado Formational contact and the Culebra and Magenta Dolomite Members of the Permian Rustler Formation. Below the bedded salt there is another water-bearing zone, the channel sandstones of the Bell Canyon formation of the Permian Delaware Mountain Group. Most data collected from 33 hydrologic test holes indicate that the water-bearing zones are characterized by low transmissivities and contain slightly saline to briny water. Data collected from drill-stem tests in the Bell Canyon Formation indicate the channel sandstones have hydraulic conductivities ranging from 0.02 to 0.36 feet per day grade vertically and laterally into siltstones and shales of very low permeability. The Rustler Formation contains the principal water-producing zones identified at the WIPP site. The Rustler-Salado formational contact has the least transmissivity, ranging from 0.00003 to 0.003 feet squared per day. The Culebra Dolomite is the most productive unit at the WIPP site with transmissivities ranging from 0.001 to 73 feet squared per day; the greater values result from fracturing in the dolomite created by dissolution of underlying halite. Minute vertical permeabilities prevent movement of water between hydrologic units. (USGS)

  10. Atmospheric circulation patterns, cloud-to-ground lightning, and locally intense convective rainfall associated with debris flow initiation in the Dolomite Alps of northeastern Italy

    Science.gov (United States)

    Underwood, S. Jeffrey; Schultz, Michael D.; Berti, Metteo; Gregoretti, Carlo; Simoni, Alessandro; Mote, Thomas L.; Saylor, Anthony M.

    2016-02-01

    The Dolomite Alps of northeastern Italy experience debris flows with great frequency during the summer months. An ample supply of unconsolidated material on steep slopes and a summer season climate regime characterized by recurrent thunderstorms combine to produce an abundance of these destructive hydro-geologic events. In the past, debris flow events have been studied primarily in the context of their geologic and geomorphic characteristics. The atmospheric contribution to these mass-wasting events has been limited to recording rainfall and developing intensity thresholds for debris mobilization. This study aims to expand the examination of atmospheric processes that preceded both locally intense convective rainfall (LICR) and debris flows in the Dolomite region. 500 hPa pressure level plots of geopotential heights were constructed for a period of 3 days prior to debris flow events to gain insight into the synoptic-scale processes which provide an environment conducive to LICR in the Dolomites. Cloud-to-ground (CG) lightning flash data recorded at the meso-scale were incorporated to assess the convective environment proximal to debris flow source regions. Twelve events were analyzed and from this analysis three common synoptic-scale circulation patterns were identified. Evaluation of CG flashes at smaller spatial and temporal scales illustrated that convective processes vary in their production of CF flashes (total number) and the spatial distribution of flashes can also be quite different between events over longer periods. During the 60 min interval immediately preceding debris flow a majority of cases exhibited spatial and temporal colocation of LICR and CG flashes. Also a number of CG flash parameters were found to be significantly correlated to rainfall intensity prior to debris flow initiation.

  11. Diagenetic analysis of the Lower Paleozoic dolomite reservoirs on the western side of the Xuefeng Mountain%雪峰山西侧地区下古生界海相白云岩储层的成岩作用

    Institute of Scientific and Technical Information of China (English)

    张娣; 李嵘; 杨平; 汪正江

    2012-01-01

    分析雪峰山西侧震旦系灯影组、寒武系武陵统—芙蓉统海相白云岩的区域分布特征和储层岩石学特征,并结合普通薄片、铸体薄片、碳氧同位素、常量元素、电子探针等资料,定量化研究对储层发育起建设性作用的成岩类型,探讨其纵横向差异.结果表明,研究区白云岩的分布特征明显受相带变化的影响和控制;震旦系灯影组主要为晶粒白云岩、残余颗粒白云岩和藻白云岩,武陵统—芙蓉统则以灰质白云岩、晶粒白云岩和残余颗粒白云岩为主.灯影组与武陵统—芙蓉统白云岩成岩期主要经历了压实压溶、胶结和矿物充填、重结晶、白云岩化、硅化、溶蚀、破裂等作用,其中对形成有利储集空间起积极作用的主要有白云岩化、溶蚀、破裂等.区域对比表明,武陵统—芙蓉统和灯影组白云岩储层在纵向上和平面上存在差异,在区域展布上存在不均一性.研究结果为下一步区块优选提供了一定的依据.%Based on an analysis and discussion on the diagenesis of Lower Paleozoic marine dolomite reservoirs in the study area, the authors acquired a better understanding of the characteristics of these reservoirs. On the basis of oil and gas geological data obtained through the analysis of the Sinian Dengying Formation and the regional distribution characteristics of the Cambrian Wuling - Furon-gian marine dolomite reservoirs, in combination with ordinary thin section, casting thin sections, carbon and oxygen isotopes, major elements, electron microprobe analyses and other data, the authors conducted comprehensive quantitative researches on the types of diage-netic types that played a constructive role in reservoir development, and explored their differences in vertical and horizontal directions. The results show that the distribution characteristics of the dolomite in the study area are significantly affected and controlled by facies change; Sinian

  12. Study on the hydration activity of ground dolomite in cementing material%白云石粉在水泥基材料中的水化活性研究

    Institute of Scientific and Technical Information of China (English)

    肖佳; 吴婷; 郭明磊

    2016-01-01

    研究了白云石粉在水泥基材料中的水化活性,分析了白云石粉掺量和细度的影响。研究表明,白云石粉掺量为0~30%时,白云石粉在水泥基材料中的强度贡献率大于零,提高了水泥基材料的比强度;随白云石粉掺量增加,水泥-白云石粉胶凝体系的强度及白云石粉在水泥基材料中的活性指数先增大后减小,白云石粉掺量为5%时均达到峰值。随白云石粉细度增大,水泥-白云石粉胶凝体系强度和比强度及白云石粉在水泥基材料中强度贡献率及活性指数均先增大后减小。白云石粉在水泥基材料中发生了去白云石化反应,阻止钙矾石向单硫型水化硫铝酸钙转化,并反应生成了水化碳铝酸钙(C3A·CaCO3·11H2O)。%The hydration activity of ground dolomite in cement based materials was studied,and the influence of the content and fine-ness of ground dolomite were analyzed.The results show that,when the ground dolomite content is 0~30%, the strength contribution rate of ground dolomite was greater than zero and the ground dolomite improved the specific strength of the cementing materials.The compressive strength of the cement-ground dolomite cementitious system and activity index of ground dolomite in the cementing material increased at first then decreased with the ground dolomite content increasing,which reached the maximum with 5% ground dolomite.The strength and specific strength of the cement-ground dolomite cementitious system increased at first then decreased with the ground dolomite fineness in-creasing,where the activity index and strength contribution rate of ground dolomite in the cementing material showed the same discipline. The calcite formation through a reaction of dedolomitization of the ground dolomite in the cementing material and inhibited the transfor-mation of ettringite to AFm,caused the formation of C3A·CaCO3·11H2O.

  13. Multi-parameter comprehensive identification of the genesis of Lower Paleozoic dolomite in Tarim Basin, China%多参数综合识别塔里木盆地下古生界白云岩成因

    Institute of Scientific and Technical Information of China (English)

    郑剑锋; 沈安江; 刘永福; 陈永权

    2012-01-01

    Massive dolomites are widely distributed in Lower Palaeozoic of Tarim Basin, northwest China. The genesis of these dolomites can be attributed to four dolomitization models, I. E. , sabkha model, seepage-reflux model, burial model and hydrothermaf model. The sabkha dolomites occurred in an evaporitic intertidal-supertidal environment and featured the deposits of gypsum-bearing dolomicrites. The seepage-reflux dolomites occurred in an evaporite platform ( lagoon) environment and featured crystal powder dolomites with the original rock structure. The burial dolomites were developed in multi-stage burial environment, characterized by the fine-medium crystalline dolomites. The hydrothermal dolomites featured medium-coarse crystalline dolomites, which were associated with hydrothermal minerals. The dolomites that differed in the genesis were developed in various diagenetic environments and stages, showing different characteristics in terms of petrography, geochemistry and geophysical response. This study summarized the multi-parameter identification of four genesis models of Lower Palaeozoic dolomite in Tarim Basin based on the detailed study of massive cores, thin sections and geochemical data of major elements, carbon and oxygen isotopes, strontium I-sotopes and rare earth elements, in combination with comprehensive analysis of well logging, seismic response characteristics, paleogeography, paleoclimate and tectonic setting, etc. This methodology overcomes the multiple solutions of dolomite genesis by comprehensive analysis.%塔里木盆地下古生界广泛发育白云岩,其成因主要可以用萨布哈白云石化、渗透回流白云石化、埋藏白云石化和热液白云石化4种模式来解释.萨布哈白云岩发育于潮间—潮上坪蒸发环境,以含膏泥晶白云岩为特征;渗透回流白云岩发育于蒸发台地(或潟湖)环境,以保留原岩结构的粉晶白云岩为特征;埋藏白云岩发育于埋藏环境的各个阶段,以细—

  14. INFLUENCE OF THE TECTONIC FABRIC ON THE OPEN PIT DESING IN THE ¨ZAPREŠIČKI IVANEC¨ NEAR ZAGREB DOLOMITE QUARRY

    Directory of Open Access Journals (Sweden)

    Karlo Braun

    1989-12-01

    Full Text Available In the »Zaprešički Ivanec« dolomite open pit near Zagreb, exploitation is carried out according to data obtained by analysis of the tectonic fabric of the rock massif, by measurement of the longitudinal seismic waves velocity, and effects of the seismic waves provoked blasting. In this article the fundamental data obtained by structural analysis and measurements with their influence on the pit design and the optimization of blasting conditions, are reviewed. Results of the longtime exploitation verify such complex aproach to deposit work-out (the paper is published in Croatian.

  15. Crushing behavior of lightmass structural member

    Institute of Scientific and Technical Information of China (English)

    Kil-Sung LEE; Yong-June YANG; Woo-Chae HWANG; In-Young YANG

    2009-01-01

    Carbon fiber reinforced plastic (CFRP) of the advanced composite materials is widely used in lightmass structural materials of air planes, ship and automobiles because of high strength and stiffness. In this study, experimental investigation was performed for each specimen. The square section members consist of aluminum, CFRP and hybrid (aluminum/CFRP) member, and hat-shaped section members consist of CFRP and hybrid (aluminum/CFRP) members specimen. Based on the collapse characteristics of aluminum square section member, the collapse characteristics and energy absorption capability of hat-shaped section members were analyzed. The axial static collapse tests were carried out for each section member. The collapse modes and the energy absorption capability of the members were analyzed. In the lightmass design aspect, the collapse characteristics and energy absorption capability of the members were compared.

  16. Members of Parliament on Facebook

    DEFF Research Database (Denmark)

    Sørensen, Mads P.

    at political party meetings and at public meetings and hearings. However, the upcoming of new social media like Facebook provides new, interesting platforms for this conversation. And many opinion makers and scholars have high expectations for the democratic potential of these platforms. The paper examines...... what happens when traditional democratic conversations between citizens and politicians are moved away from the old face-to-face meetings and into Facebook. Through interviews with Danish Members of Parliament (MPs) the paper examines the advantages and disadvantages of online democratic conversations...... on Facebook as experienced by the MPs. The paper builds on a former quantitative mapping of the political conversation activities between Danish MPs and their followers on Facebook (Sørensen, 2015)....

  17. 7 CFR 985.25 - Alternate members.

    Science.gov (United States)

    2010-01-01

    ... Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements and Orders; Fruits, Vegetables, Nuts), DEPARTMENT OF AGRICULTURE MARKETING ORDER REGULATING THE... member's absence, (b) in the event of the member's death, removal, resignation, or...

  18. 白云石制备矿物掺和料及对混凝土性能的影响%Preparation of Concrete Admixtures with Dolomite Rock Debris and Its Influence on Concrete Properties

    Institute of Scientific and Technical Information of China (English)

    贾丽莉; 高育欣; 赵日煦; 彭园; 杨龙; 霍亮

    2015-01-01

    试验将白云石岩屑磨细为粉体,用作混凝土掺和料,研究其易磨性、活性、碱⁃白云石活性及对混凝土力学性能和工作性能的影响。结果表明:白云石岩屑较水渣易粉磨,水渣粉磨4min时,平均粒径为18�01μm,白云石屑粉磨2min平均粒径即为4�28μm,而继续粉磨细度增长缓慢,且易结团黏聚;单独磨细白云石粉的活性低于62%,低于II级粉煤灰,而采用水渣与白云石共磨,使共磨复合掺和料的28d活性达到75%以上,较单独的白云石粉活性提高18%;在NaOH溶液中养护14d的基准试件及掺白云石粉试件膨胀率均低于0�1%,依据标准白云石粉作为掺和料不具有ACR活性危害;单掺白云石粉使混凝土早期和后期强度均降低,而白云石⁃水渣复合掺和料使混凝土早期强度略有增长。%The fine grinding of dolomite rock debris was used as concrete admixture. This paper studies on its grindability, active effects, alkali⁃dolomite reaction effects, and its impact on the mechanical properties and working performance of concrete. The results showed that the dolomite rock debris was easy to grind than slag, the average particle size of slag grinding for 4min is 18�01μm, whereas, the average particle size is 4�28μm for dolomite rock debris grinding only 2min, and the prolonged grinding make little growth in fineness and prone to particle aggregation. The activity of ground dolomite powder is less than 62%, lower than FA II. By grinding the dolomite with slag together, the activity of dolomite composite admixture is more than 75%, increased by 18% compared to separate dolomite activity. The expansion of both reference samples and dolomite admixture samples is less than 0�1%, curing for 14 days in NaOH solution, thus the grinding dolomite powder as mineral admixture has no active harm of ACR according to the standard. Single added with dolomite power reduced early and later

  19. 川东北飞仙关组白云岩成因及其次生孔隙%Genesis and secondary pores of dolomite from Triassic Feixianguan Formation in the northeast of Sichuan Province

    Institute of Scientific and Technical Information of China (English)

    黄勇; 魏志红; 邓金花; 刘若冰; 陈再学

    2011-01-01

    白云岩以其次生晶间孔隙发育、易于形成高孔高渗优质油气储层为特征,长期以来受到地质学界的高度重视.早期白云石晶体自形程度及晶间孔隙的发育程度除受白云石化成岩流体的影响外,还受原岩储渗性能的控制.川东北宣汉-达县地区飞仙关组白云岩主要存在渗透回流白云石化、混合水白云石化和埋藏白云石化3种成因模式和至少3期次云化.白云岩化并未直接改善储层物性,不是形成优质储层的主要原因,只是形成优质储层的前提;多期次强烈的溶蚀作用及构造碎裂化作用才是形成优质储层的主控因素.大量次生孔隙主要发育在白云岩化之后.台缘暴露浅滩有利于混合水白云石化和大套层状优质白云岩储层的发育.%The dolomites are characterized by the developed secondary intercrystalline pores and easily form qualified reservoirs with high permeability and porosity, and thus are emphasized by geological academic circles for a long time. The idiomorphic degrees of dolomite crystals and the developing degrees of intercyrstalline pores are controlled by accumulating and permeable properties of the original rocks in addition to fluids leading to dolomitization. There exist three genetic models of dolomitization, such as the permeating-flowing-back dolomitization, mixed water dolomitization and burying Dolomitization and at least three times secondary dolomitization for dolomiltes of the Triassic Feixianguan Formation in Xuanhan-Daxuan County in the northeast of Sichuan Province. The dolomitization of dolomites of the-Triassic Feixianguan Formation in the northeast of Sichuan Province does not play the role of improving the geophysical properties of reservoirs and it is not the main reason to form qualified reservoirs but just a premise. Intense dissolution and structural fragmentation of many times are the main controlling factors to form qualified reservoirs and lots of secondary pores

  20. Performance of Ni/dolomite pellet catalyst on gas distribution from cassava rhizome gasification with a modular fixed-bed gasifier.

    Science.gov (United States)

    Sricharoenchaikul, V; Atong, D; Sornkade, P; Nisamaneenate, J

    2016-08-19

    Thermal conversion of cassava rhizome was performed using a modular downdraft gasifier with the addition of Ni-based catalysts as promising tar eliminating and produced gas upgrading techniques. The activities of a synthesized 5% Ni/dolomite pellet catalyst prepared by impregnation method were investigated in a secondary reactor downstream of the gasifier. High reforming activity of the Ni/dolomite pellet catalyst on tar reduction was achieved. The conversion to H2 and CO was improved via steam reforming of methane and char reaction with CO2. Moreover, the formation of CH4 and CxHy was diminished through the tar or condensable hydrocarbon reformed on the catalyst surface. The carbon and hydrogen conversions of cassava rhizome with prepared catalyst were 83.79% and 61.78%, respectively, at an air flow rate of 1.98 m(3)/hr. At this condition, tar formation was low, while the lower heating value was 4.39 MJ/m(3) and H2 to CO molar ratio was 1.22. Generally, the addition of a catalyst not only enhanced gas production, but also reduced tar and particulate matter generation; thus, its implementation should help lessen the pollution control requirement and cost of operation, while allowing higher quality fuel gas production.

  1. Assessing the effects of soil liming with dolomitic limestone and sugar foam on soil acidity, leaf nutrient contents, grape yield and must quality in a Mediterranean vineyard

    Energy Technology Data Exchange (ETDEWEB)

    Olego, M.A.; Visconti, F.; Quiroga, M.J.; Paz, J.M. De; Garzón-Jimeno, E.

    2016-11-01

    Aluminium toxicity has been recognized as one of the most common causes of reduced grape yields in vineyard acid soils. The main aim of this study was to evaluate the effect of two liming materials, i.e. dolomitic lime and sugar foam, on a vineyard cultivated in an acid soil. The effects were studied in two soil layers (0-30 and 30-60 cm), as well as on leaf nutrient contents, must quality properties and grape yield, in an agricultural soil dedicated to Vitis vinifera L. cv. ‘Mencía’ cultivation. Data management and analysis were performed using analysis of variance (ANOVA). As liming material, sugar foam was more efficient than dolomitic limestone because sugar foam promoted the highest decrease in soil acidity properties at the same calcium carbonate equivalent dose. However, potassium contents in vines organs, including leaves and berries, seemed to decrease as a consequence of liming, with a concomitant increase in must total acidity. Soil available phosphorus also decreased as a consequence of liming, especially with sugar foam, though no effects were observed in plants. For these reasons fertilization of this soil with K and P is recommended along with liming. Grape yields in limed soils increased, although non-significantly, by 30%. This research has therefore provided an important opportunity to advance in our understanding of the effects of liming on grape quality and production in acid soils. (Author)

  2. 7 CFR 1425.19 - Member cooperatives.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 10 2010-01-01 2010-01-01 false Member cooperatives. 1425.19 Section 1425.19... OF AGRICULTURE LOANS, PURCHASES, AND OTHER OPERATIONS COOPERATIVE MARKETING ASSOCIATIONS § 1425.19 Member cooperatives. A CMA may obtain loans or LDP's on behalf of a member cooperative when the...

  3. 7 CFR 795.4 - Family members.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 7 2010-01-01 2010-01-01 false Family members. 795.4 Section 795.4 Agriculture... PROVISIONS COMMON TO MORE THAN ONE PROGRAM PAYMENT LIMITATION General § 795.4 Family members. Effective for... was a “person” solely on the basis that: (a) A family member cosigns for, or makes a loan to, such...

  4. 7 CFR 946.23 - Alternate members.

    Science.gov (United States)

    2010-01-01

    ... Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements... such member's absence. In the event of the death, removal, resignation, or disqualification of a member... the event that both a member and his or her alternate are unable to attend a Committee meeting,...

  5. 7 CFR 959.31 - Alternate members.

    Science.gov (United States)

    2010-01-01

    ... Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements... designated to do so by the member for whom he is an alternate. In the event both a member of the committee... or grower) to serve in such member's place and stead. In the event of the death, removal,...

  6. 7 CFR 923.27 - Alternate members.

    Science.gov (United States)

    2010-01-01

    ... Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements... event of the death, removal, resignation, or disqualification of a member, his alternate shall act for him until a successor for such member is selected and has qualified. In the event both a member of...

  7. 7 CFR 922.27 - Alternate members.

    Science.gov (United States)

    2010-01-01

    ... Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements..., shall act in the place and stead of such member and perform such other duties as assigned. In the event... until a successor for such member is selected and has qualified. In the event both a member of...

  8. International Focus: Highlighting APPA Members Worldwide

    Science.gov (United States)

    Glazner, Steve, Comp.

    2011-01-01

    While most APPA member institutions are located in the United States and Canada, there are also 45 of member institutions located internationally--from Australia and New Zealand to Southeast Asia to the Middle East to Europe. This article focuses on four of its international members: (1) American University of Kuwait (AUK); (2) American University…

  9. Calibration of the dolomite clumped isotope thermometer from 25 to 350 °C, and implications for a universal calibration for all (Ca, Mg, Fe)CO3 carbonates

    Science.gov (United States)

    Bonifacie, Magali; Calmels, Damien; Eiler, John M.; Horita, Juske; Chaduteau, Carine; Vasconcelos, Crisogono; Agrinier, Pierre; Katz, Amandine; Passey, Benjamin H.; Ferry, John M.; Bourrand, Jean-Jacques

    2017-03-01

    Carbonate clumped isotope thermometry is based on the temperature-dependent formation of 13C18O16O22- ion groups within the lattice of solid carbonate minerals. At low temperatures the bonds between rare, heavy 13C and 18O isotopes are thermodynamically favored, and thus at equilibrium they are present in higher than random abundances. Here we calibrate the use of this temperature proxy in a previously uncalibrated carbonate phase - dolomite [CaMg(CO3)2] - over a temperature range that extends to conditions typical of shallow crustal environments, by determining the Δ47 values of CO2 extracted from synthetic or natural (proto)dolomites grown at known temperatures from 25 to 350 °C and analyzed in two different laboratories using different procedures for sample analysis, purification and post-measurement data treatment. We found that the Δ47-1/T2 dependence for (proto)dolomite is linear between 25 and 350 °C, independent of their Mg/Ca compositions or cation order (or the laboratory in which they were analyzed), and offset from, but parallel to, the theoretical predictions of the Δ63 dependence to temperature of the abundance of the 13C18O16O2 isotopologue inside the dolomite and calcite mineral lattices as expected from ab-initio calculations (Schauble et al., 2006). This suggests that neither the equilibrium constant for 13C-18O clumping in (proto)dolomite lattice, nor the experimental fractionation associated with acid digestion to produce CO2, depend on their formation mechanism, degree of cation order and/or stoichiometry (i.e., Mg/Ca ratio) and/or δ18O and δ13C compositions (at least over the range we explored). Thus, we suggest the following single Δ47-1/T2 linear regression for describing all dolomite minerals:

  10. Reservoir diagenesis of 3rd member of Feixianguan Formation, Jiannan Gas Field%建南气田飞三段储层成岩作用研究

    Institute of Scientific and Technical Information of China (English)

    鲍云杰; 王恕一; 蒋小琼; 管宏林; 杨振恒

    2011-01-01

    以建43井为例,研究了建南气田三叠系飞三段储层的成岩作用及特点,其中白云岩化作用、溶蚀作用和构造破裂作用对储层贡献较大.其成岩序列为藻粘结、泥晶化→一世代胶结→大气淡水溶蚀→二世代粒状胶结→新生变形→压实压溶→白云岩化→早期张裂缝及充填→构造挤压作用→埋藏溶蚀Ⅰ→进油→白云石、萤石充填、石英充填交代→油演化为沥青→埋藏溶蚀Ⅱ→晚期张裂缝→进气;主要经历了海底(潮间)环境、大气淡水环境、浅埋藏和深埋藏环境.白云石晶体、二世代粒状胶结物、萤石被溶蚀、压性裂缝发育以及孔隙无明显变形是埋藏溶蚀的主要识别标志.%Diagenesis and features of the 3rd member of Feixianguan Formation in the Jiannan Gas Field were studied taking well Jian43 as an example. Dolomitization, karstification and tectonic disruption were contributive to reservoir. Diagenesis sequence was illustrated as follows: algae agglutinate and micritization-"first consolidation-*" atmospheric water erosion-*-secondary granular consolidation-" neo-morphism-" compaction and pressolution-" dolomitization-?■ early tension fissure and filling-"tectonic compression-" buried erosion I -"petroleum entering-"dolomite and fluorite filling as well as quartz filling and metasomatisnr~"oil evolving to bitumen-"buried erosion E~"late tension fissure-"gas entering. There were 4 kinds of diagenesis environment including seabed (intertidal), atmospheric water, shallow bury and deep bury. Dolomite crystals, secondary granular consolidations, eroded fluorites, tensional fissures and pores without obvious deformation were the main identifications for buried erosions.

  11. The kinetics of dissolution of dolomite in CO2-H2O systems at 1.5 to 65oC and 0 to 1 atm PCO2.

    Science.gov (United States)

    Busenberg, E.; Plummer, L.N.

    1982-01-01

    Weight loss measurements at different T and PCO2 during experimental investigations of the dissolution kinetics of eight samples of dolomite permitted recognition of a two-stage process. During the first stage, which is brief, the surface composition of the dolomite becomes enriched with the MgCO3 component and the CaCO3 component dissolves faster. In the second and more important stage both components of the solid are released stoichiometrically, described quantitatively by three parallel consecutive forward reactions and one significant backward reaction. Dissolution rates are apparently more dependent on crystallographic order than on compositional variations. -M.S.

  12. Polyphase tertiary fold-and-thrust tectonics in the Belluno Dolomites: new mapping, kinematic analysis, and 3D modelling

    Science.gov (United States)

    Chistolini, Filippo; Bistacchi, Andrea; Massironi, Matteo; Consonni, Davide; Cortinovis, Silvia

    2014-05-01

    The Belluno Dolomites are comprised in the eastern sector of the Southern Alps, which corresponds to the fold-and-thrust belt at the retro-wedge of the Alpine collisional orogen. They are characterized by a complex and polyphase fold-and-thrust tectonics, highlighted by multiple thrust sheets and thrust-related folding. We have studied this tectonics in the Vajont area where a sequence of Jurassic, Cretaceous and Tertiary units have been involved in multiple deformations. The onset of contractional tectonics in this part of the Alps is constrained to be Tertiary (likely Post-Eocene) by structural relationships with the Erto Flysch, whilst in the Mesozoic tectonics was extensional. We have recognized two contractional deformation phases (D1 and D2 in the following), of which only the second was mentioned in previous studies of the area and attributed to the Miocene Neoalpine event. D1 and D2 are characterized by roughly top-to-WSW (possibly Dinaric) and top-to-S (Alpine) transport directions respectively, implying a 90° rotation of the regional-scale shortening axis, and resulting in complex thrust and fold interference and reactivation patterns. Geological mapping and detailed outcrop-scale kinematic analysis allowed us to characterize the kinematics and chronology of deformations. Particularly, relative chronology was unravelled thanks to (1) diagnostic fold interference patterns and (2) crosscutting relationships between thrust faults and thrust-related folds. A km-scale D1 syncline, filled with the Eocene Erto Flysch and "decapitated" by a D2 thrust fault, provides the best map-scale example of crosscutting relationships allowing to reconstruct the faulting history. Due to the strong competence contrast between Jurassic carbonates and Tertiary flysch, in this syncline spectacular duplexes were also developed during D2. In order to quantitatively characterize the complex interference pattern resulting from two orthogonal thrusting and folding events, we

  13. Simulated transport and biodegradation of chlorinated ethenes in a fractured dolomite aquifer near Niagara Falls, New York

    Science.gov (United States)

    Yager, Richard M.

    2000-01-01

    Leakage of trichloroethene (TCE) from a neutralization pond at a former manufacturing facility near Niagara Falls, N.Y. during 1950-87 into the Guelph Formation of the Lockport Group, a fractured dolomite aquifer, created a plume of TCE and its metabolites that, by 1990, extended about 4,300 feet south of the facility. A smaller plume of dense, nonaqueous-phase liquids (DNAPL) probably serves as a continuing source of TCE. The presence of the TCE metabolites cis-1,2-dichloroethene (DCE), vinyl chloride (VC), and ethene in the plume, and the results of previous laboratory microcosm studies, indicate that the TCE is being degraded by naturally occurring microorganisms. Biodegradation rates of TCE and its metabolites were estimated through simulation with BIOMOC, a solute-transport model that represents multispecies reactions through Monod kinetics. A fracture zone in the Guelph Formation was represented as a porous medium containing an extensive, 3-foot thick layer with several interconnected fractures; this layer is bounded above and below by subhorizontal stratigraphic contacts. The Monod reaction constants were estimated through nonlinear regression to minimize the difference between computed concentrations of TCE and its metabolites, and the concentrations measured before and during 5 years of pump-and-treat remediation. Transport simulations indicated that, by April 1998, the chlorinated ethene plume had reached a dynamic equilibrium between the rate of TCE dissolution and the rate of removal through pumping and biodegradation. Biodegradation of chlorinated ethenes at the site can be simulated as first-order reactions because the concentrations are generally less than the half-saturation constants estimated for Monod kinetics (320 mg/L for TCE, 10 mg/L for DCE, and 1 mg/L for VC). Computed degradation rates are proportional to the estimated ground-water velocity, which could vary by more than an order magnitude at the site, as indicated by the estimated range of

  14. Basic Data Report for Drillhole SNL-1 (C-2953)

    Energy Technology Data Exchange (ETDEWEB)

    Dennis W. Powers; Washington Regulatory and Environmental Services

    2005-01-19

    SNL-1 (permitted by the New Mexico State Engineer as C-2953) was drilled to provide geological data and hydrological testing of the Culebra Dolomite Member of the Permian Rustler Formation near the margin of dissolution of halite in the upper Permian Salado Formation in the northeast arm of Nash Draw. SNL-1 is located in the northwest quarter of section 16, T21S, R31E, in eastern Eddy County, New Mexico, and it is adjacent to the tailings pile of Mississippi Potash Incorporated (now Intrepid) East mine to test for the presence of shallow zones that might include brine infiltrated from the tailings pile. SNL-1 was drilled to a total depth of 644 ft below ground level (bgl). Below surface wash, SNL-1 encountered, in order, the Mescalero caliche, Dewey Lake, and Rustler Formations.

  15. Members of the LHC Resources Review Boards

    CERN Multimedia

    Maximilien Brice

    2002-01-01

    Photo 01: Members of the LHCRRB visiting Point 2, hosting the ALICE experiment From l. to r. : W. Korda, Head of the VIP Office; P. Rimmer, CERN public relations, J. Seed, Member of the LHCRRB, J.-P. Revol, ALICE CERN Team Leader; J. Bartke, Member of the LHCRRB; F. Suransky, Member of the LHCRRB; J. Schukraft, Spokesperson, ALICE experiment and S. Molinari, VIP Office. Photo 02: Members of the LHC Resources Review Boards visiting the ALICE magnet at Point 2. L. to. r.: O. Dines-Hansen, H. Boggild, S. Irgens-Jensens, H.A. Gustafsson Photo 03: Members of the LHCRRB visiting Point 2, hosting the ALICE experiment From l. t to r.: J.Richter, Member of the LHCRRB; H. Gutbrod, Deputy Spokesperson, ALICE experiment; G. Paic, ALICE experiment; D. Muller, Member of the LHCRRB; P. Brau-Munzinger, ALICE experiment; R. Santo, Member of the LHCRRB, A. Van Rijn, Member of the LHCRRB; J. Engelen, Member of the LHCRRB.

  16. Member end releases in framed structures

    Science.gov (United States)

    Stallings, J. M.

    1993-02-01

    Discontinuities such as internal hinges are commonly encountered in framed structures. A general method of including discontinuities in stiffness method analyses of planar frames by the release of member end forces is developed. Modifications are made to the member stiffness matrix and equivalent joint load vector to account for the released end forces. A FORTRAN algorithm is given that makes the necessary modifications to the member stiffness matrix and equivalent joint load vector for the standard planar frame member. The algorithm allows combinations of up to three member end forces to be released (specified at zero or nonzero values). An algorithm is also given that calculates the unknown member end displacements at the released member end forces. Numerical examples are given to illustrate the uses and capabilities of the algorithms.

  17. 鄂尔多斯盆地苏里格地区奥陶系马家沟组白云石化%Dolomitization of Ordovician Majiagou Formation in Sulige region, Ordos Basin

    Institute of Scientific and Technical Information of China (English)

    付金华; 王宝清; 孙六一; 包洪平; 徐波

    2011-01-01

    The Ordovician Majiagou Formation in Sulige region of the Ordos Basin was deposited in hypersaline restricted epicontinental environment. It is mainly composed of carbonate rocks with thin evaporate interbeds. The dolomites are classified into 3 kinds; micrite, fine-medium crystal dolomite, and dolomite filled in pores and fractures. The Na concentrations range from 0 to 2 099 X 10-6, the Sr concentrations range from 0 to 70 X 10-6,the Mn concentrations range from 0 to 112 X 10-6, and the Fe concentrations range from 39 to 86 746 X 10-6 in dolomites. The dolomites are characterized with varied Na, low Sr and Mn, and high Fe concentrations. The 18O values for dolomites range from -16. 00%0 to -5. 73%o, and the 13C values range from -11. 46%0 to 1. 90%. (PDB). It indicates that carbonate rocks have experienced leaching and burial diagenesis. Most filled dolomites have lower 18O and 13C values than surrounding components, indicating that the former was formed later. The dolomites are characterized with low degrees of order and less stoichiometry. The 87Sr/86 Sr values of dolomites range from 0. 707 977±0. 000 070 to 0. 711 791±0. 000 064, most of which are higher than that corresponding to global boundary between middle and upper Ordovician. Microbial dolomitization is the reason for dolomite genesis.%苏里格地区马家沟组为一套碳酸盐岩为主,夹蒸发岩的地层,沉积于超盐度的局限陆表海环境.白云石分为以泥晶结构为主的,以细—中晶结构为主和充填于孔、缝中3类.白云石Na含量(0~2 099)×10-6,Sr含量(0~70)×10-5,Mn含量(0~112)×10-6,Fe含量(39~86 746)×10-6,以变化较大的Na含量、低的Sr和Mn含量,高的Fe含量为特征.白云石δ18()值在-16.00‰~-5.73‰之间,δ13C值在-11.46‰~1.90‰之间,说明碳酸盐岩经历了淋滤作用和埋藏作用.大多数孔、缝充填白云石较围岩组分有较低的δ18O和δ13C值,说明孔缝充填的白云石形成较晚.白云石以低

  18. Dolomitization mechanism of Cambrian carbonates in the Bachu area,Tarim Basin, NW China%巴楚地区寒武系碳酸盐岩白云石化机制

    Institute of Scientific and Technical Information of China (English)

    周波; 李明; 段书府; 朱长见; 邬光辉; 曾昌民; 高力

    2012-01-01

    Geochemical characteristics of the Cambrian carbonates are studied through systematic sampling in the Bachu area of the Tarim Basin. The dolomitization mechanisms are compared and analyzed of the dolomites above and below salt beds and limestone between the salt beds. The δ 18O values of dolomites in the limestone between salt beds are larger than -6%o, the δ 13C values are normally larger than -l%o, the 87 Sr/86 Sr values are smaller than ancient sea water plus Mn and Na element enrichment. All these features suggest that the dolomites are developed due to early sabakha dolomitization. For the dominantly medium- and coarse-grained dolomites above the uppper salt bed, the δ 13C values of samples are lower than zero, the δ 13 O values are normally -9%o-0, the 87Sr/86Sr values are close to ancient sea water. These features show that the dolomites are developed in a shallow burial environment. For the dominantly powdered and fine dolomites below the lower salt bed, the δ 13C values of samples are larger than zero, the δ 18O values are normally lower than zero, the 87 Sr/86Sr values are larger than the above mentioned dolomites, plus Fe and Sr element enrichment. These features indicate that the dolomites are developed within an evaporate environment on a restricted platform, and they are of penetration reflux dolomitization and affected by the deep burial hyperthermal environment later.%通过系统取样进行地球化学分析,研究塔里木盆地巴楚地区寒武系碳酸盐岩地球化学特征,在此基础上对盐上白云岩、盐间灰岩及盐下白云岩的白云石化成因进行对比研究.盐间灰岩中的白云石δ18O值大于-6‰,δ13C值一般大于-1‰,87Sr/86Sr值略低于古海水,Mn和Na元素富集,表明白云石化作用发生在沉积早期,系萨布哈成因;盐上白云岩以中—粗晶白云岩为主,δ13C值偏负,δ18O值偏负但均大于-9‰,87Sr/86Sr值趋同于古海水,反映形成于浅埋藏环境;盐下白云岩

  19. Discovery of oil-bearing dolomite in Dazhuoma area of Qiangtang Basin and its ;significance%西藏羌塘盆地达卓玛地区含油白云岩的发现及其意义

    Institute of Scientific and Technical Information of China (English)

    许明; 钱信禹; 李亚林; 韩中鹏; 戴敬华

    2016-01-01

    The dolomite serves as the most important reservoir which has always been the key to the evaluation and exploration of oil and gas. The oil-bearing dolomite was found recently near the Dazhuoma area, Amdo. The oil-bearing dolomite develops in the Buqu Formation of Middle Jurassic with the thickness over 30m and the length over 80m. The rocks are the medium-coarse-grain dolomite. The porosity of the samples is in the range of 5%~17%and the permeability is from 2.84×10-3μm2 to 236×10-3μm2. The dolomite belongs to the low-porosity and low-permeability to medium-porosity and low-permeability reservoir which is similar to the high quality dolomite of Longeni. The new oil-bearing dolomite found in Amdo lies in the same layer as the dolomite in the Bi⁃luo Co-Angdaer Co zone, from which the authors infer that the oil-bearing dolomite has an east-west distribution for about 180km and is the most important reservoir in the basin. The discovery of oil-bearing dolomite in Dazhuoma area expands the distribution and extent of dolomite reservoir, which can provide new basis for the oil exploration and disposition in Qiangtang Basin.%白云岩作为含油气盆地最重要的储层,长期以来一直是盆地油气评价和勘探的重点。报道近期在南羌塘安多地区达卓玛地区发现的含油白云岩地质特征。白云岩出露于中侏罗世布曲组,厚度大于30m,横向延伸大于80m,岩石类型为中-粗晶白云岩,其孔隙度在5.0%~17.0%之间,渗透率在2.84×10-3~236×10-3μm2之间,属于低孔低渗至中孔低渗储层,与已发现的隆鄂尼优质白云岩相似,是盆地良好的储集层。空间上,达卓玛白云岩位于隆鄂尼-昂达尔错白云岩东部,且处于同一层位,表明白云岩在南羌塘盆地东西展布约180km。达卓玛含油白云岩的发现扩大了羌塘盆地白云岩储层和古油藏带的范围和规模,为羌塘盆地油气地质评价和勘探部署提供了新的依据。

  20. Characteristics and development mechanism of dolomite and dolomitic quartzite reservoirs of the Middle Permian Maokou Formation in eastern Sichuan Basin%四川盆地东部中二叠统茅口组白云岩及云质硅岩储层特征与发育规律

    Institute of Scientific and Technical Information of China (English)

    唐雪松; 谭秀成; 刘宏; 马腾; 苏成鹏; 程雪莹; 陈虹宇; 曹剑

    2016-01-01

    Unique dolomite and dolomitic quartzite reservoirs occur in the Middle Permian Maokou Formation in eastern Sichuan Basin.They are commonly believed to be of “fault-controlled hydrothermal”origin.However,most of the ex-plorary wells targeting at these reservoirs are unsuccessful ,thus further study needs to be performed .The characteristics and development mechanism of these reservoirs are studied by means of comparative analysis of the outcrops on the pe -riphery of the basin and cores inside the basin .The results indicate the main reservoir rocks in the Maokou Formation are crystalline dolomite,siliceous dolomite and dolomitic quartzite ,whose distributions are mainly related to the karst sys-tems,thus are uneven both laterally and vertically .Most of the crystalline dolomite occurs on the periphery of the karst systems,and their reservoir properties are poor .On the contrary,the siliceous dolomite and dolomitic quartzite are mostly distributed within the karst systems and have favorable reservoir properties .The development of reservoirs obeys the law of“facies-controlled karst”.Specifically , grain-beach facies provided the material basis for the reservoirs , and facies-con-trolled eogenetic karst was the key for the formation of high-quality reservoirs .The following hydrothermal dolomitzation made it possible for the preservation of reservoir pores .The siliceous hydrothermal activities and later calcite cementation resulted in the filling of some pores .The unique siliceous dolomite and dolomitic quartzite finally came into being .Ac-cording to these results , it is proposed to further strength study on “facies-controlled karst” reservoirs in addition to “fault-controlled hydrotherm”reservoirs,so as to improve the accuracy of reservoior prediction .%四川盆地东部中二叠统茅口组发育了独具特色的白云岩及云质硅岩类储层,主流观点是“断控热液”成因,但勘探多有落空,说明需要重新认识。通

  1. Hydrothermal Dolomites in the Early Albian (Cretaceous Platform Carbonates (NW Spain: Nature and Origin of Dolomites and Dolomitising Fluids Dolomies hydrothermales présentes dans les carbonates de la plate-forme albienne précoce (Crétacé; NO de l’Espagne : nature et origine des dolomies et des fluides dolomitisants

    Directory of Open Access Journals (Sweden)

    Shah M.M.

    2012-02-01

    Full Text Available This study documents the temporal and lateral variation in petrographic and geochemical signatures of fault-related dolomite bodies in the Ranero and El-Moro areas (Karrantza valley, Cantabrian mountains; NW Spain. These dolomite bodies are hosted in Albian carbonates, which were deposited in the Basque-Cantabrian Basin as a result of an intense rift-related subsidence with associated faulting along various orientations. Fluid circulations generated replacive and cement dolomites, paragenetically followed by various calcite cements. Petrography, mineralogical and geochemical investigations (XRD, ICP, XRF, stable and Sr isotopes helped in distinguishing hydrothermal stages. Two major dolomite facies were observed according to their Fe-content. Early dolomites are ferroan and replace limestone more significantly than the later, non ferroan dolomites. Dolomites are generally stoichiometric (49.76 to 51.59 M% CaCO3 and exhibit a broad range of depleted δ18O values (–18.7 to –10.5‰ V-PDB, which may indicate multiphase dolomitisation and/or different degrees of recrystallisation. Decreasing δ18O values correlate with decreasing Fe content in dolomites. In the Ranero area, dolomites show less slightly depleted δ13C values (–0.15 to +2.13‰ V-PDB relative to the host limestone δ13C signature, while these values are substantially more depleted in El-Moro area (down to –2.18‰ V-PDB. Hydrothermal calcites predating dolomitisation show less depleted δ18O values (–14.15 to –12.1‰ V-PDB than postdolomitisation calcite (–18.1‰ V-PDB. Sr isotope data suggest that the fluids interacted with siliciclastic lithologies (sandstone, shale. The dolomite fabric is variably altered through dedolomitisation and cataclastic deformation. Dolomitisation occurred in at least two main episodes. A first episode of pervasive ferroan dolomitisation probably resulted from compactional dewatering of basinal fluids from the nearby Basque trough and

  2. 塔里木盆地古城低凸起中下奥陶统白云岩稀土元素地球化学特征及其成因%REE Geochemical Characteristics and Genesis of the Middle-Lower Ordovician Dolomite in the Gucheng Low Uplift of the Tarim Basin

    Institute of Scientific and Technical Information of China (English)

    张振伟

    2016-01-01

    The Middle-Lower Ordovician dolomite in the Gucheng Low Uplift of the Tarim Basin is the main reservoir of natural gas in the area.Based on characteristics of texture and structures,six kinds of dolomite have been classified in this paper.They include fine to micritic dolomite,fine to crystalline anhedral dirty dolomite,fine to medium sized euhedral dolomite,medium to coarse grained dirty dolomite,medium to coarse grained clean dolomite,and saddle dolomite.Their REE contents have been measured.Results show that the total contents of REE are relatively low,with positive correlations between the REE and LaN/YbN or LREE/HREE ratios,but poor correlations between the REE and δEu orδCe values. The REE distribution patterns of various types of dolomite are generally flat,slightly right declined,and LREE slightly en-riched,with very limited differences among them.The genetic types of various kinds of dolomite are slightly different.They include penecontemporaneous evaporative pumping dolomitization,penecontemporaneous seepage reflux dolomitization, shallow burial dolomitization,and hydrothermal dolomitization.%中下奥陶统白云岩是塔里木盆地古城低凸起主要的天然气储集层,按结构特征将其分为粉-微晶白云石、粉-细晶级他形脏白云石、粉-中晶级自形白云石、中-粗晶脏白云石、中-粗晶干净白云石和鞍形白云石等6种类型,对不同类型白云岩的稀土元素分析结果表明,研究区样品的REE总体含量偏低,与LaN/YbN、LREE/HREE大致呈正相关,与 δEu、δCe的相关性较差.不同类型白云石稀土元素配分曲线差别不大,均为总体平缓、略向右倾,显示轻稀土略微富集.不同类型白云石成因类型略有不同,主要为同生期蒸发泵成因、同生期渗透回流成因、浅埋藏成因和热液成因等4种成因类型.

  3. 7 CFR 989.29 - Initial members and nomination of successor members.

    Science.gov (United States)

    2010-01-01

    ... Committee § 989.29 Initial members and nomination of successor members. (a) Initial members. Members and... in nomination shall be given the opportunity to provide the committee a short statement outlining... during the preceding crop year on the Committee. Nominations shall be made by and from handlers,...

  4. 7 CFR 932.130 - Public member and alternate public member eligibility requirements and nomination procedures.

    Science.gov (United States)

    2010-01-01

    ... requirements. (1) The public member and alternate public member shall not be a producer, handler, or family... processing of olives; nor shall they be either an officer, director, or employee, or family member of an officer, director, or employee of any firm engaged in such activities. (2) The public member and...

  5. Variable-density ground-water flow and paleohydrology in the Waste Isolation Pilot Plant (WIPP) region, southeastern New Mexico

    Science.gov (United States)

    Davies, P.B.

    1989-01-01

    Variable-density groundwater flow was studied near the Waste Isolation Pilot Plant in southeastern New Mexico. An analysis of the relative magnitude of pressure-related and density-related flow-driving forces indicates that density-related gravity effects are not significant at the plant and to the west but are significant in areas to the north, northeast, and south. A regional-scale model of variable-density groundwater flow in the Culebra Dolomite member of the Rustler Formation indicates that the flow velocities are relatively rapid (10 to the minus 7th power m/sec) west of the site and extremely slow (10 to the minus 11th power m/sec) east and northeast of the site. In the transition zone between those two extremes, which includes the plant, velocities are highly variable. Sensitivity simulations indicate that the central and western parts of the region, including the plant, are fairly well isolated from the eastern and northeastern boundaries. Vertical-flux simulations indicate that as much as 25% of total inflow to the Culebra could be entering as vertical flow, with most of this flow occurring west of the plant. A simple cross-sectional model was developed to examine the flow system as it drains through time following recharge during a past glacial pluvial. This model indicates that the system as a whole drains very slowly and that it apparently could have sustained flow from purely transient drainage following recharge of the system during the Pleistocene. (USGS)

  6. Differences in the rheological properties of calcitic and dolomitic lime slurries: influence of particle characteristics and practical implications in lime-based mortar manufacturing

    Directory of Open Access Journals (Sweden)

    Arizzi, A.

    2012-06-01

    Full Text Available The study of the rheological properties of lime suspensions is a useful means to evaluate the workability of lime mortars. In this work, we studied the flow behaviour of two industrial hydrated limes, one of calcitic and the other of dolomitic composition, by means of two types of rheometer with different geometry and setup mode. The obtained results were interpreted taking into account the differences in microstructure and surface properties of the suspended particles. Calcitic lime dry particles are formed by angular and polydisperse clusters and, once dispersed in water, they behave like thixotropic materials. On the other hand, the dolomitic lime is formed by nanoparticles and small round cluster and it shows a pronounced plastic behaviour in suspension. This fundamental difference between the two materials explains the traditional preference for dolomitic lime mortars for plastering and rendering applications.

    El estudio de las propiedades reológicas de suspensiones de cal es una herramienta muy útil para evaluar la trabajabilidad de morteros de cal. En este trabajo se ha estudiado el comportamiento en suspensión de dos cales hidratadas, de composición calcítica y dolomítica, mediante dos tipos de reómetros con geometría y modalidades distintas de medida. Los resultados obtenidos se han interpretado teniendo en cuenta las diferencias en la microestructura y las propiedades de superficie de las partículas en suspensión. Las partículas de cal calcítica están formadas por aglomerados angulares y polidispersos y, una vez dispersadas en agua, presentan un comportamiento tixotrópico. Por su parte, la cal dolomítica está formada por nanopartículas y pequeños agregados redondeados y muestra en suspensión un pronunciado comportamiento plástico. Esta importante diferencia entre las dos cales explica la preferencia tradicional de morteros de cal dolomítica para aplicaciones en revocos.

  7. Effect of Niagara power project on ground-water flow in the upper part of the Lockport Dolomite, Niagara Falls area, New York

    Science.gov (United States)

    Miller, Todd S.; Kappel, W.M.

    1987-01-01

    The Niagara River Power Project near Niagara Falls, N.Y., has created recharge and discharge areas that have modified the direction of groundwater flow east and northeast of the falls. Before construction of the power project in 1962, the configuration of the potentiometric surface in the upper part of the Silurian Lockport Dolomite generally paralleled the buried upper surface of the bedrock. Ground water in the central and east parts of the city of Niagara Falls flowed south and southwestward toward the upper Niagara River (above the falls), and ground water in the western part flowed westward into Niagara River gorge. The power project consists of two hydroelectric powerplants separated by a forebay canal that receives water from the upper Niagara River through two 4-mi-long, parallel, buried conduits. During periods of nonpeak power demand, some water in the forebay canal is pumped to a storage reservoir for later release to generate electricity during peak-demand periods. Since the power project began operation in 1962, groundwater within 0.5 mi of the buried conduits has seeped into the drain system that surrounds the conduits, then flows both south from the forebay canal and north from the Niagara River toward the Falls Street tunnel--a former sewer that crosses the conduits 0.65 mi north of the upper Niagara River. Approximately 6 million gallons of ground water a day leaks into the Falls Street tunnel, which carries it 2.3 mi westward to the Niagara River gorge below the falls. Daily water-level fluctuations in the forebay canal affect water levels in the drain system that surrounds the conduits, and this , in turn, affects the potentiometric surface in the Lockport Dolomite within 0.5 mi of the conduits. The drains transmit changes in pressure head near the forebay canal southward at least as far as the Falls Street tunnel area and possibly to the upper Niagara River. Some water in the pumped-storage reservoir recharges ground water in the Lockport

  8. 安徽含山县汤山白云石矿产地质特征及综合利用%Geological features and comprehensive utilization of the Tangshan dolomite resources in Hanshan County, Anhui Province

    Institute of Scientific and Technical Information of China (English)

    姜丹

    2012-01-01

      With the development of socialist economic construction, the applications of dolomite keep expanding, espe-cially in building material, metallurgy and chemical industries. Dolomite exploration has become an important part of economic construction. The discovery of the Tangshan dolomite deposit, study of its stratigraphy, structure, fault and other ore geology features provide us with a shortcut for dolomite exploration.%  随着社会主义经济建设的发展,白云石应用领域不断扩展,广泛用于建材、冶金、化工等行业;寻找白云石矿已成为经济建设不可或缺的一部分。汤山白云石矿的发现,对它的地层、构造、断层等矿床地质特征等的研究,为我们找寻类似白云石矿产指明了一条捷径。

  9. Secoiridoids and other chemotaxonomically relevant compounds in Pedicularis: phytochemical analysis and comparison of Pedicularis rostratocapitata Crantz and Pedicularis verticillata L. from Dolomites.

    Science.gov (United States)

    Venditti, Alessandro; Frezza, Claudio; Sciubba, Fabio; Foddai, Sebastiano; Serafini, Mauro; Nicoletti, Marcello; Bianco, Armandodoriano

    2016-08-01

    We compared the respective metabolite patterns of two Pedicularis species from Dolomites. Seven phenylethanoid glycosides, i.e., verbascoside (1), echinacoside (2), angoroside A (3), cistantubuloside B1 (4), wiedemannioside C (5), campneoside II (11) and cistantubuloside C1 (12), together with several iridoid glucosides as aucubin (6), euphroside (7), monomelittoside (8), mussaenosidic acid (9) and 8-epiloganic acid (13) were identified. Pedicularis verticillata showed also the presence of greatly unexpected secoiridoids, ligustroside (14) and excelside B (15), very rare compounds in Lamiales. Both PhGs and iridoids are considered of taxonomical relevance in the Asteridae and their occurrence in Pedicularis was discussed. In particular, the exclusive presence of several compounds such as 8-epiloganic acid (13), campneoside II (11), cistantubuloside C1 (12), ligustroside (14) and excelside B (15) in Pedicularis rostratocapitata, and angoroside A (3), cistantubuloside B1 (4) and wiedemannioside C (5) in P. verticillata could be considered specific markers for the two botanical entities.

  10. On the way of Friuli "yellow villages": the use of a calcareous-dolomitic sandstone in the surroundings of the quarrying area through the centuries.

    Science.gov (United States)

    Frangipane, Anna

    2017-04-01

    The role of local stone building material in cultural and technological heritage is based on the definition of the area of use, as related to ancient transportation networks, allowing the movement of heavy blocks from the quarries to the building sites. It is the case of the result of several surveys carried out for the detection of the architectural elements, dating from Middle Age to 20th century, made of a yellowish calcareous-dolomitic sandstone, which have been found, hidden among renovated buildings and new construction, in Friuli region (NE Italy). on the way between the quarrying piedmont western area and the towns of Udine and Spilimbergo. Starting from the definition of the quarrying area, the contribution give notice of such architectural elements (frames, columns, …), both in vernacular architecture and in relevant buildings, putting in evidence the period of their realisation and their technological features.

  11. Dolomite-Derived Ni-Based Catalysts with Fe Modification for Hydrogen Production via Auto-Thermal Reforming of Acetic Acid

    Directory of Open Access Journals (Sweden)

    Xinyan Zhong

    2016-06-01

    Full Text Available Bio-oil can be obtained via fast pyrolysis of biomass, and typically contains acetic acid (~30 mass %. The acetic acid has often been tested as a model compound for hydrogen production via reforming bio-oil, in which catalysts are a key factor for stable hydrogen production. However, deactivation of catalysts by coking and oxidation hinders the application of the reforming process. Dolomite-derived Ni-based catalysts with Fe additive, MgNi0.2Ca0.8−xFexO2±δ (x = 0–0.8, were successfully synthesized by the hydrothermal synthesis method, and then tested in auto-thermal reforming (ATR of acetic acid (AC. The MgNi0.2Ca0.5Fe0.3O2±δ catalyst performed a stable reactivity in ATR: the conversion of AC reached 100%, and the H2 yield remained stable around 2.6 mol-H2/mol-AC. The catalysts were characterized by X-ray diffraction (XRD, N2 physisorption, X-ray photoelectron spectra (XPS, H2-temperature-programmed reduction (TPR, inductively coupled plasma- atomic emission spectroscopy (ICP-AES and Thermogravimetry (TG; the results show that a periclase-like solid solution of Mg(Ni,FeO and lime were formed via the precursors of dolomite and hydrotalcite, and then transformed into Fe-rich Ni-Fe alloy with basic support of MgO-CaO after reduction. The stable Ni0 spices with basic support can explain the stability and resistance to coking during ATR of AC.

  12. Diagenetic differences of the Zhenzhuchong Member of Ziliujing Formation in the Jiulongshan–Jiange area, Sichuan Basin

    Directory of Open Access Journals (Sweden)

    Mingcai Hou

    2015-03-01

    Full Text Available The rocks of the Zhenzhuchong Member of the Ziliujing Formation, Jiulongshan–Jiange area in the Sichuan Basin, were analyzed by petrography, XRD, and SEM techniques to investigate their diagenetic history and properties, such as authigenic mineral types, evolution of mixed-layer illite–smectite minerals, the clay assembly, and the fraction of mixed-layer clay minerals. The results revealed that the Zhenzhuchong Member has experienced several important episodes of diagenetic alteration since the deposition, including compaction (pressure-solution, cementation, metasomatism, dissolution, fracturing, and infilling of caves and cracks. It was also observed that diagenetic properties of the Jiulongshan area were significantly different from those of the Jiange area. The rock samples from the Jiulongshan area were characterized by the composition of siliceous and calcareous cements, varying amounts of detrital grains, clay matrix and kaolinite replaced by calcites, a certain amount of rarely dissolved early-stage kaolinite, dickite, and infillings by late-stage calcite. On the other hand, for the rock samples from the Jiange area, the dissolution is a common phenomenon with features of abundant aluminosilicates-dissolution pores or components, but the replacement phenomenon has rarely been seen. These rock samples were characterized by the presence of clay mineral cements, quartz, and dolomite infillings. It indicated that there was a great difference of diagenesis between the two areas in the types, phase, and temperature of diagenetic fluids. Revealing the difference would provide theoretical and practical implications for the exploration of high quality oil and gas reservoirs.

  13. Sedimentary characteristics and genesis of lacustrine dolomite in the fourth member of Shahejie Formation in Dongying Sag%东营凹陷沙四段湖相白云岩沉积特征及成因

    Institute of Scientific and Technical Information of China (English)

    李得立; 谭先锋; 夏敏全; 赵宇超; 邱桂强; 张守鹏

    2010-01-01

    以岩石学特征为基础,结合沉积特征和沉积地球化学资料,对东营凹陷沙四段湖相白云岩成因进行了研究.结果表明:不同成因的白云岩,其岩石结构、发育环境和地球化学特征有所不同;该地区白云岩类型多样,普遍具有泥-微晶结构;白云岩主要位于滨浅湖、深湖-半深湖及盐湖环境中,岩性组合上与泥页岩、粉砂岩、膏岩及玄武岩伴生;受层序发育的控制,该时期白云岩多发育在晚期高位体系域之中,白云石化作用不彻底,白云岩含友质成分较高.地球化学数据表明:白云石有序度普遍较低,Sr质量分数普遍较高,平均值接近海水中的Sr质量分数,说明沙四时期受到了海侵作用和构造热液-深部流体的影响;高Mn、低Fe、高Na的特征反映了该时期主要的沉积环境为干旱-半干旱的蒸发环境.综合构造条件、沉积环境及地球化学分析等因素,建立了沙四段准同生白云岩化和构造热液白云岩化模式.

  14. 51 CAS Members Elected in 2005

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    @@ Atotal of 51 prominent Chinese scientists were elected CAS members in 2005. The announce ment was made at a press conference held on Dec. 16 in Beijing. CAS President LU Yongxiang was present at the conference to give a briefing on the election and the new members.

  15. 7 CFR 1425.14 - Member business.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 10 2010-01-01 2010-01-01 false Member business. 1425.14 Section 1425.14 Agriculture... business. (a) At least 50 percent of a crop of an authorized commodity acquired by, or delivered to, a CMA... not be considered in determining the volume of member or nonmember business. ...

  16. School Board Member Recruitment in Ontario.

    Science.gov (United States)

    Cistone, Peter J.

    Employing a process model of political recruitment, this study investigated the relative impact of a school district's social, economic, and political structure on school board member recruitment. The process data were collected by means of structured interviews with neophyte school board members in a stratified sample of school boards in the…

  17. 7 CFR 916.27 - Alternate members.

    Science.gov (United States)

    2010-01-01

    ... Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements... member and perform such other duties as assigned. In the event of the death, removal, resignation, or... qualified. In the event both a member of the committee and his alternate are unable to attend a...

  18. 7 CFR 915.27 - Alternate members.

    Science.gov (United States)

    2010-01-01

    ... Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements... and stead of such member. In the event of the death, removal, resignation, or disqualification of a.... In the event both a member and his alternate are unable to attend a committee meeting, the...

  19. 7 CFR 925.27 - Alternate members.

    Science.gov (United States)

    2010-01-01

    ... Regulations of the Department of Agriculture (Continued) AGRICULTURAL MARKETING SERVICE (Marketing Agreements... program duties by the chairman or the committee. In the event of the death, removal, resignation, or... and has qualified. In the event that both a member and that member's alternate are unable to attend...

  20. Educational Faculty Members' Perceptions on Multicultural Teacher

    Science.gov (United States)

    Günay, Rafet; Aslan, Dolgun

    2016-01-01

    This purpose of this study is to determine how the perceptions of teaching personnel members were conceptualized through use of metaphorical images with regard to the multicultural teacher. In this study, a phenomenological design, a type of qualitative research design was used. A total of 323 teaching personnel members employed at 71 educational…

  1. CERN Member States signatures at LEP inauguration

    CERN Multimedia

    1989-01-01

    The signatures of the dignitaries who represented CERN's Member States on the occasion of the Inauguration of LEP on 13 November 1989. The Large Electron-Positron (LEP) collider was inaugurated in the presence of some 1500 guests, including Heads of State and Ministers from all of CERN's 14 Member States.

  2. Faculty Members on Boards of Trustees

    Science.gov (United States)

    Ehrenberg, Ronald G.; Patterson, Richard W.; Key, Andrew V.

    2013-01-01

    During the 2011-12 academic year, a group of faculty and student researchers at the Cornell Higher Education Research Institute (CHERI) gathered information on which public and private institutions had faculty members on boards of trustees and obtained the names of the faculty members serving in these roles. In April and May 2012, the authors…

  3. Methods of Assessment for Affected Family Members

    Science.gov (United States)

    Orford, Jim; Templeton, Lorna; Velleman, Richard; Copello, Alex

    2010-01-01

    The article begins by making the point that a good assessment of the needs and circumstances of family members is important if previous neglect of affected family members is to be reversed. The methods we have used in research studies are then described. They include a lengthy semi-structured interview covering seven topic areas and standard…

  4. Pore size distribution, catalytic activity and fluidizing properties of porous dolomite pellets%多孔白云石颗粒的孔径分布、催化能力和流化特性

    Institute of Scientific and Technical Information of China (English)

    缪冶炼; 阴秀丽; 时晓剑; 吴创之

    2012-01-01

    Porous dolomite pellets are potential catalysts for the tar decomposition in biomass gasification process. In order to develop the fluidized bed reactor with porous dolomite particles,porous dolomite pellets of a radius in the range of (0.9 -2.5) mm and a length in the range of (4.1 -8.6) mm were prepared,and their pore size distribution .catalytic effect and fluidization properties were investigated. The results showed that the porous dolomite pellets had much larger porosity in the pore size range of (0.1 -10) 祄 in comparison with natural dolomite particles. Under the condition of a catalyst loading at 117 g, a temperature at 800 ℃. And a flow rate of carrier gas at 2 L ·min-1 ,99.3% of acetic acid was decomposed by the porous dolomite pellets, while acetic acid decomposition rate over natural dolomite particles was only 36.5%. Furthermore, the drag coefficient was determined and an empirical equation of incipient fluidizing velocity for the porous dolomite pellets was established.The incipient fluidizing velocity enhanced from 1.3 m ·s11 to 2.4 m ·s-1 when the equivalent diameter of porous dolomite pellets increased from 2. 7 mm to 6. 8 mm. The calculated values of incipient fluidizing velocity was consistent with the experimental values.%多孔白云石颗粒是一种适用于生物质气化焦油裂解的催化剂.为了开发多孔白云石颗粒流化床焦油裂解反应器,制备出半径(0.9~2.5) mm和长度(4.1 ~8.6) mm的圆柱形多孔白云石颗粒,测定了多孔白云石颗粒的内部孔径分布、催化能力和流化特性.结果表明,与天然白云石颗粒相比,多孔白云石颗粒孔径(0.1~10)μm的空隙率大幅增加.在催化剂用量117 g、温度800℃和载气流量2L·min -的条件下,乙酸在多孔白云石颗粒上的裂解率达99.3%,而天然白云石颗粒上裂解率仅为36.5%.求出了多孔白云石颗粒的曳力系数,建立了多孔白云石颗粒初始流化速率的经验公

  5. A discussion on the formation mechanism of dolomite associated with hydrothermal solution in Tazhong area%塔中地区与热液有关白云岩的形成机理探讨

    Institute of Scientific and Technical Information of China (English)

    赵闯; 于炳松; 张聪; 沈越峰; 戚秀丽

    2012-01-01

    与热液有关白云岩以晶体粗大为特征,较易形成物性良好的油气储集体.塔中地区寒武系-下奥陶统发育大量深层白云岩,以粉-细晶白云岩为主,局部可见中-粗晶白云岩.该中-粗晶白云岩流体包裹体均一温度经压力校正主要集中在173~199℃,比该层位最大埋藏温度(约160℃)高10~40℃,故认为其形成与热液活动有关.镜下观察两种类型的白云岩存在渐变过渡现象和碳氧同位素值的部分重叠,说明中-粗晶白云岩可能由粉-细晶白云岩在热液作用下重结晶而来.进一步结合其流体包裹体盐度(为正常海水盐度的3~5倍)和富87Sr、贫13C的特征认为,其成岩流体可能为岩浆热液经过下寒武统富87Sr、贫13C泥页岩质烃源岩的改造,并向上运移与中寒武统膏岩层孔隙间浓缩海水混合而形成的混合性流体.前者为其提供热量,后者可增加其盐度,遍布区内的深大断裂体系为其提供了运移通道.%The dolomite associated with hydrothermal solution is characterized by coarse crystallization and can form reservoirs with high porosity and permeability. There are a lot of deep buried dolomites in Cambrian and Lower Ordovician strata of Tazhong area, which mainly consist of powder-fine crystalline dolomite, and medium-coarse crystalline dolomite can be found in some parts of this area. A study of fluid inclusions shows that the medium-coarse crystalline dolomite has a fluid inclusion homogenization temperature of 173 ~199℃ corrected by pressure, which is 10~40℃ higher than its maximum burial temperature (about 160℃), so its formation should be related to hydrothermal activity. The powder-fine crystalline dolomite has a δ13Cpdb of - 2.45%o~ -1.08%o, -1.54%o on average; its 8 18 Orb is -6.90‰~-3.54‰~-5.35%o on average; the medium-coarse crystalline dolomite has a S 13Cpdb of - 2.76‰~-1.12‰~-1.73%o on average, which mostly overlap~-those from the powder

  6. Petrologic,geochemical characteristics and origin of the Lower Ordovician dolomite in Yubei area%玉北地区下奥陶统白云岩岩石学、地球化学特征及成因

    Institute of Scientific and Technical Information of China (English)

    黄擎宇; 张哨楠; 叶宁; 李映涛

    2014-01-01

    The petrologic ,geochemical characteristics and origin of the Lower Ordovician dolomite in Yubei area were inves -tigated through the analysis of the cores ,thin-sections,SEM,cathode luminescence ,trace element ,C-O isotope and micro-thermometry of fluid inclusions .The following results were obtained .Matrix dolomites are of two types:fine crystalline ,euhe-dral-subhedral dolomite and fine to coarse crystalline ,anhedral dolomite with saddle fillings .The origin of dolomite is close-ly related to crystal texture ( nonplanar anhedral ,planar euhedral/subhedral ) instead of crystal size .The fine crystalline ,eu-hedral-subhedral dolomite has high Sr and low Fe-Mn content ,and C and O isotope composition similar to that of seawater in Early Ordovician .So this type of dolomite was overall the product of low-temperature dolomitization associated with the Ordovician seawater during the early stage of shallow burial .In contrast ,the fine to coarse crystalline ,anhedral dolomite has low Sr,relatively high Fe and Mn content and more negative O isotope value .And its fluid inclusion microthermometry re-sult suggests that it has high homogenization temperature and salinity .Combined with the regional tectonic background ,it is believed that this type of dolomite was primarily the product of high -temperature dolomitization during late stage of shallow burial to moderate burial ,and was locally transformed by hydrothermal fluids from marine-sourced saline water in formation . Moreover ,there are two stages of saddle dolomite fillings:one is coeval with the matrix dolomite of hydrothermal dolomitiza-tion origin and the other may be associated with the thermal fluid post -magmatic activity during the Permian .%通过岩心、薄片、扫描电镜、阴极发光、微量元素、同位素和包裹体测温等分析手段,对玉北地区下奥陶统白云岩岩石学特征、地球化学特征及成因进行研究。结果表明,该区白云岩主要由细晶、自形-半

  7. Spouses/Family Members of Service Members at Risk for PTSD or Suicide

    Science.gov (United States)

    2016-09-01

    promotion causing excessive stress . 7 4. Service members sacrificing their own personal health to try to meet demands of military and family (e.g...1 AWARD NUMBER: W81XWH-10-2-0113 TITLE: Spouses/ Family Members of Service Members at Risk for PTSD or Suicide PRINCIPAL INVESTIGATOR: Keith D...SUBTITLE Spouses/ Family Members of Service Members at Risk for PTSD or Suicide 5a. CONTRACT NUMBER 5b. GRANT NUMBER W81XWH-10-2-0113 5c. PROGRAM

  8. 煅烧工艺制度对轻烧白云石活性度的影响%Effect of calcining process and system on reactivity of soft-burnt dolomite

    Institute of Scientific and Technical Information of China (English)

    高华

    2012-01-01

    The effect of calcining processes on the reactivity three kinds of soft-burnt dolomites is studied through calcining test and observation of microstructure. It is concluded as follows : ( 1 ) soaking time is 90 minutes,, there is a trend in which the reactivity of soft-burnt dolomite is increased first with the calcining temperature uprising and then decreased. At 1 050℃ the reactivity of soft-burnt dolomite reaches the highest value; (2) for some calcining temperature, there is a period of calcining time to make soft-burnt lime have a highest reactivity value ; (3) the grain size of the dolomite tobe calcined has influence on the reactivity of the calcined product; (4) the microstructure of the raw dolomite has great influence on the reactivity of the calcined product, generally the raw dolomite with coarse and big crystals is easy to obtain the calcined product with higher reactivity.%通过煅烧实验和显微结构观察,研究了煅烧工艺对三种自云石轻烧后活性度的影响,得出如下结论:(1)保温时间为90min,随煅烧温度提高轻烧白云石的活性呈现先升高、后降低的趋势,在1050℃活性度达到最高点。(2)对应某煅烧温度存在一个煅烧时间使轻烧白云石活性最高。(3)白云石的煅烧颗粒尺寸影响煅烧产物活性度。(4)白云石原矿的显微结构对煅烧产物活性度有很大影响,一般晶粒粗大的原矿易得到活性较高的煅烧产物。

  9. Study on Technological Characteristic of Process of Calcining and Decomposing Dolomite Ore%白云石煅烧离解过程的工艺特性研究

    Institute of Scientific and Technical Information of China (English)

    蒋述兴

    2011-01-01

    对不同温度下煅烧成的苛性白云石进行了X射线粉晶分析,结合热分析结果,得出在750~800℃温度下煅烧成的苛性白云石镁质胶凝材料,其中的Mgo水化活性较大.在煅烧白云石的过程中,是结晶--化学反应为限制步骤,因此,要尽可能创设条件,加速化学反应的进行,并要尽可能控制好煅烧时间,以便抑制氧化镁的完全结晶.另外,分析计算了在利用临桂县白云石生产苛性白云石镁质胶凝材料时,不同粒度(5~250mm的多种粒度)的块状白云石在不同温度下完全离解所需要的煅烧时间.%The work of the XRD of the caustic dolomite prepared by different calcining temperatures had been done.According to the results of the XRD and DTA of the dolomite in the atmosphere of the CO2, we reached a conclusion that the MgO of the magnesia cementitious material of the caustic dolomite calcined at the temperature condition from 750℃ to 800℃ possessed larger hydration activity. In the process of calcining and decomposing the dolomite ore, the restrictive step was the crystallization and chemical reaction. The condition to quicken the chemical reaction should be consequently created as far as possible, and the calcining time should be controlled as far as possible to restrain the complete crystallization of the MgO in the caustic dolomite. In addition,the required calcining times to fully decompose the MgCOj in the big lump dolomites which were the paticles from 5mm to 250 mm had been obtained by the methods of the experiments,analysis and computations.

  10. Phase I (Year 1) Summary of Research--Establishing the Relationship between Fracture-Related Dolomite and Primary Rock Fabric on the Distribution of Reservoirs in the Michigan Basin

    Energy Technology Data Exchange (ETDEWEB)

    G. Michael Grammer

    2005-11-09

    This topical report covers the first 12 months of the subject 3-year grant, evaluating the relationship between fracture-related dolomite and dolomite constrained by primary rock fabric in the 3 most prolific reservoir intervals in the Michigan Basin (Ordovician Trenton-Black River Formations; Silurian Niagara Group; and the Devonian Dundee Formation). Phase I tasks, including Developing a Reservoir Catalog for selected dolomite reservoirs in the Michigan Basin, Characterization of Dolomite Reservoirs in Representative Fields and Technology Transfer have all been initiated and progress is consistent with our original scheduling. The development of a reservoir catalog for the 3 subject formations in the Michigan Basin has been a primary focus of our efforts during Phase I. As part of this effort, we currently have scanned some 13,000 wireline logs, and compiled in excess of 940 key references and 275 reprints that cover reservoir aspects of the 3 intervals in the Michigan Basin. A summary evaluation of the data in these publications is currently ongoing, with the Silurian Niagara Group being handled as a first priority. In addition, full production and reservoir parameter data bases obtained from available data sources have been developed for the 3 intervals in Excel and Microsoft Access data bases. We currently have an excess of 25 million cells of data for wells in the Basin. All Task 2 objectives are on time and on target for Phase I per our original proposal. Our mapping efforts to date, which have focused in large part on the Devonian Dundee Formation, have important implications for both new exploration plays and improved enhanced recovery methods in the Dundee ''play'' in Michigan--i.e. the interpreted fracture-related dolomitization control on the distribution of hydrocarbon reservoirs. In an exploration context, high-resolution structure mapping using quality-controlled well data should provide leads to convergence zones of fault

  11. Israel, CERN’s new Member State

    CERN Multimedia

    Brice, Maximilien

    2014-01-01

    On Wednesday, 15 January 2014, the official Israeli Flag-raising Ceremony took place to mark the accession of Israel to Membership of CERN, bringing the Organization’s number of Member States to 21.

  12. STRUCTURAL PERFORMANCE OF DEGRADED REINFORCED CONCRETE MEMBERS.

    Energy Technology Data Exchange (ETDEWEB)

    Braverman, J.I.; Miller, C.A.; Ellingwood, B.R.; Naus, D.J.; Hofmayer, C.H.; Bezler, P.; Chang, T.Y.

    2001-03-22

    This paper describes the results of a study to evaluate, in probabilistic terms, the effects of age-related degradation on the structural performance of reinforced concrete members at nuclear power plants. The paper focuses on degradation of reinforced concrete flexural members and shear walls due to the loss of steel reinforcing area and loss of concrete area (cracking/spalling). Loss of steel area is typically caused by corrosion while cracking and spalling can be caused by corrosion of reinforcing steel, freeze-thaw, or aggressive chemical attack. Structural performance in the presence of uncertainties is depicted by a fragility (or conditional probability of failure). The effects of degradation on the fragility of reinforced concrete members are calculated to assess the potential significance of various levels of degradation. The fragility modeling procedures applied to degraded concrete members can be used to assess the effects of degradation on plant risk and can lead to the development of probability-based degradation acceptance limits.

  13. Member states buoy up beleagured EMBL

    CERN Multimedia

    Balter, M

    1999-01-01

    EMBL's governing council, made up of delegates from the lab's 16 member countries, agreed in principle to meet the costs of a multimillion-dollar pay claim, the result of a recent ruling by the ILO in Geneva (1 page).

  14. Employability Development Teams: Team Member Roles

    Science.gov (United States)

    Otto, Mary L.; Lewis, Meharry H.

    1972-01-01

    The authors point out that team roles are designed to be complementary, but much of the frustration that develops among team members is due to lack of role definition and too much overlapping of responsibility. (Author)

  15. New data on the FWF project P20018-N10: The Puez key-section in the Dolomites (Southern Alps; N-Italy)

    Science.gov (United States)

    Lukeneder, A.; Mayrhofer, S.

    2009-04-01

    Early Cretaceous ammonoids (n = 424) were collected at the Puez locality in the Dolomites of Southern Tyrol (Lukeneder and Aspmair 2006). The cephalopod fauna from the marly limestones to marls here indicates Late Valanginian to Early Aptian age. The underlying Biancone Formation (Maiolica Formation) is Early Valanginian. The deposition of the marly limestones and marls in this interval occurred during unstable conditions. Ammonoids. The ammonoid fauna comprises 27 different genera, each apparently represented by 1-2 species. The complete occurrence at the Puez section is dominated by the Phylloceratina (30%) and the Ammonitina (34%). Phyllopachyceras (17%) and Phylloceras (13%) from the Phylloceratina are the most frequent components, followed by Lytoceras (12%) from the Lytoceratina, and Barremites (10%) and Melchiorites (8%) from the Ammonitina. Phylloceatidae and Desmoceratidae are dominating the cephalopod-fauna. Some ammonoid zones defined by Hoedemaeker et al. (2003) can be recognized. The following index fossils were examined within the collections of the NHMW (Austria) and the NMB (Italy): for the latest Valanginian Criosarasinella furcillata (C. furcillate Zone and Subzone), for the middle Early Hauterivian Olcostephanus (Jeannoticeras) jeannoti (O.(J.) jeannoti Subzone), and Heinzia sayni for the lowermost Upper Barremian (H. sayni Subzone; Reboulet and Hoedemaeker (reporters) et al., submitted). The ammonoid fauna contains only descendants of the Mediterranean Province (Tethyan Realm). Most affinities of the cephalopod fauna are observed with faunas from the adjacent areas of Italy (Lessini Mountains, Belluno, southern Trento Plateau), the Northern Calcareous Alps and the Bakony, Geresce and Mecsek Mountains of Hungary. This is explained by the neighbouring position of the latter areas during the Early Cretaceous on the Apulian/Adria block and the Alpine-Carpathian microplate. The frequency of the ammonoids and the richness of the fauna make this

  16. Results of the recent TDA member survey.

    Science.gov (United States)

    1999-10-01

    This article fully outlines active TDA members' responses to the various questions posed by the recent membership survey. Every effort was made to ensure the accuracy of the results. To this end, a professional research firm was employed to cross tabulate answers and analyze the data. A thorough reading will provide you with the TDA members' perspective on a wide range of important dental issues.

  17. Migration processes in SCO member states

    Directory of Open Access Journals (Sweden)

    Valentina Sergeevna Antonyuk

    2012-12-01

    Full Text Available The article concerns modern state and development of migration processes in SCO member states. As a main method of research statistical analysis was applied. The article shows that migration streams between SCO member states are rather intensive, and the problem of labor migration becomes more and more urgent. The countries of consuming and supplying of labour force are clearly differentiated in the region. For some countries, labor export is the key sector of economy. At the same time, interstate relations between SCO member states sometimes are rather disputed. The most urgent factors causing the development of migration processes in the region were determined. Among them, thefactor of growing outflows from China isespecially noted. It is noted that migration processes are discussed by SCO member states nowadays in terms of illegal migration and international criminality connected with it. It means that the question of labor migration is a real problem. It is indicated that the creation of a specific joint commission on migration policy affiliated with the Council of Foreign Ministers of SCO member states is the necessary condition of effective interaction in migration questions within the framework of Shanghai Cooperation Organization.

  18. An endolithic microbial community in dolomite rock in central Switzerland: characterization by reflection spectroscopy, pigment analyses, scanning electron microscopy, and laser scanning microscopy.

    Science.gov (United States)

    Horath, T; Neu, T R; Bachofen, R

    2006-04-01

    A community of endolithic microorganisms dominated by phototrophs was found as a distinct band a few millimeters below the surface of bare exposed dolomite rocks in the Piora Valley in the Alps. Using in situ reflectance spectroscopy, we detected chlorophyll a (Chl a), phycobilins, carotenoids, and an unknown type of bacteriochlorophyll-like pigment absorbing in vivo at about 720 nm. In cross sections, the data indicated a defined distribution of different groups of organisms perpendicular to the rock surface. High-performance liquid chromatography analyses of pigments extracted with organic solvents confirmed the presence of two types of bacteriochlorophylls besides chlorophylls and various carotenoids. Spherical organisms of varying sizes and small filaments were observed in situ with scanning electron microscopy and confocal laser scanning microscopy (one- and two-photon technique). The latter allowed visualization of the distribution of phototrophic microorganisms by the autofluorescence of their pigments within the rock. Coccoid cyanobacteria of various sizes predominated over filamentous ones. Application of fluorescence-labeled lectins demonstrated that most cyanobacteria were embedded in an exopolymeric matrix. Nucleic acid stains revealed a wide distribution of small heterotrophs. Some biological structures emitting a green autofluorescence remain to be identified.