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Sample records for uranium-rich paleozoic epithermal

  1. Uranium rich granite and uranium productive granite in south China

    Energy Technology Data Exchange (ETDEWEB)

    Mingyue, Feng; Debao, He [CNNC Key Laboratory of Uranium Resource Exploration and Evaluation Technology, Beijing Research Institute of Uranium Geology (China)

    2012-07-15

    The paper briefly introduces the differences between uranium rich granite and uranium productive granite in the 5 provinces of South China, and discusses their main characteristics in 4 aspects, the uranium productive granite is highly developed in fracture, very strong in alteration, often occurred as two-mica granite and regularly developed with intermediate-basic and acid dikes. The above characteristics distinguish the uranium productive granite from the uranium rich granite. (authors)

  2. Uranium rich granite and uranium productive granite in south China

    International Nuclear Information System (INIS)

    Feng Mingyue; He Debao

    2012-01-01

    The paper briefly introduces the differences between uranium rich granite and uranium productive granite in the 5 provinces of South China, and discusses their main characteristics in 4 aspects, the uranium productive granite is highly developed in fracture, very strong in alteration, often occurred as two-mica granite and regularly developed with intermediate-basic and acid dikes. The above characteristics distinguish the uranium productive granite from the uranium rich granite. (authors)

  3. Growth and alteration of uranium-rich microlite

    International Nuclear Information System (INIS)

    Giere, R.; Swope, R. J.; Buck, E. C.; Guggenheim, R.; Mathys, D.; Reusser, E.

    2000-01-01

    Uranium-rich microlite, a pyrochlore-group mineral, occurs in 440 Ma old lithium pegmatites of the Mozambique Belt in East Africa. Microlite exhibits a pronounced growth zoning, with a U-free core surrounded by a U-rich rim (UO 2 up to 17 wt.%). The core exhibits conjugate sets of straight cracks (cleavage planes) which provided pathways for a late-stage U-enriched pegmatitic fluid which interacted with the U-free microlite to produce a distinct U enrichment along the cracks and led to the formation of the U-rich rim. Following the stage of U incorporation into microlite, a second generation of hydrothermal fluids deposited mica along the cleavage planes. Subsequent to these two hydrothermal stages, the host rock was uplifted and subjected to intense low-temperature alteration during which Na, Ca and F were leached from the microlite crystals. This alteration also led to a hydration of microlite, but there is no evidence of U loss. These low-temperature alteration effects were only observed in the U-rich rim which is characterized by a large number of irregular cracks which are most probably the result of metamictization, as indicated by electron diffraction images and powder X-ray patterns. The pyrochlore-group minerals provide excellent natural analogues for pyrochlore-based nuclear waste forms, because samples of variable age and with high actinide contents are available

  4. The geological characteristics and forming conditions of granite type uranium-rich ore deposits

    International Nuclear Information System (INIS)

    Li Tiangang; Tong Hangshou; Feng Mingyue; Li Yuexiang; Xu Zhan

    1993-03-01

    The forming conditions and concentration mechanism of rich ore, criteria of ore prospecting and selection of uranium-rich ore target area are introduced in the article that is based on the studying of geological characteristics and conditions of granite type uranium-rich ore deposits of No 201 and 361 and on the comparisons of rich and poor ore deposits in geological conditions. Some new view points are also presented as the separate deposition of uranium minerals and gangue minerals is the main mechanism to form rich ore, for rich ore formation the ore enrichment by superimposition is not a universal regularity and most uranium-rich ore deposits are formed within one mineralization stage or mainly in one mineralization stage

  5. The geological characteristics and forming conditions of granite type uranium-rich ore deposits

    Energy Technology Data Exchange (ETDEWEB)

    Tiangang, Li; Hangshou, Tong; Mingyue, Feng; Yuexiang, Li; Zhan, Xu [Beijing Research Inst. of Uranium Geology (China)

    1993-03-01

    The forming conditions and concentration mechanism of rich ore, criteria of ore prospecting and selection of uranium-rich ore target area are introduced in the article that is based on the studying of geological characteristics and conditions of granite type uranium-rich ore deposits of No 201 and 361 and on the comparisons of rich and poor ore deposits in geological conditions. Some new view points are also presented as the separate deposition of uranium minerals and gangue minerals is the main mechanism to form rich ore, for rich ore formation the ore enrichment by superimposition is not a universal regularity and most uranium-rich ore deposits are formed within one mineralization stage or mainly in one mineralization stage.

  6. Directional epithermal neutron detector

    International Nuclear Information System (INIS)

    Givens, W.W.; Mills, W.R. Jr.

    1986-01-01

    A borehole tool for epithermal neutron die-away logging of subterranean formations surrounding a borehole is described which consists of: (a) a pulsed source of fast neutrons for irradiating the formations surrounding a borehole, (b) at least one neutron counter for counting epithermal neutrons returning to the borehole from the irradiated formations, (c) a neutron moderating material, (d) an outer thermal neutron shield providing a housing for the counter and the moderating material, (e) an inner thermal neutron shield dividing the housing so as to provide a first compartment bounded by the inner thermal neutron shield and a first portion of the outer thermal neutron shield and a second compartment bounded by the inner thermal neutron shield and a second portion of the outer thermal neutron shield, the counter being positioned within the first compartment and the moderating material being positioned within the second compartment, and (f) means for positioning the borehole tool against one side of the borehole wall and azimuthally orienting the borehole tool such that the first chamber is in juxtaposition with the borehole wall, the formation epithermal neutrons penetrating into the first chamber through the first portion of the outer thermal neutron shield are detected by the neutron counter for die-away measurement, thereby maximizing the directional sensitivty of the neutron counter to formation epithermal neutrons, the borehole fluid epithermal neutrons penetrating into the second chamber through the second chamber through the second portion of the outer thermal neutron shield are largely slowed down and lowered in energy by the moderating material and absorbed by the inner thermal neutron shield before penetrating into the first chamber, thereby minimizing the directional sensitivity of the neutron counter to borehole fluid epithermal neutrons

  7. Microstructural investigation of as-cast uranium rich U–Zr alloys

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Yuting, E-mail: zhangyuting@caep.cn [Science and Technology on Surface Physics and Chemistry Laboratory, Jiangyou 621908, Sichuan (China); School of Nuclear Science and Technology, National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029, Anhui (China); Wang, Xin [Science and Technology on Surface Physics and Chemistry Laboratory, Jiangyou 621908, Sichuan (China); Zeng, Gang [Institute of Materials, China Academy of Engineering Physics, Jiangyou 621908, Sichuan (China); Wang, Hui [Science and Technology on Surface Physics and Chemistry Laboratory, Jiangyou 621908, Sichuan (China); Jia, Jianping [Institute of Materials, China Academy of Engineering Physics, Jiangyou 621908, Sichuan (China); Sheng, Liusi [School of Nuclear Science and Technology, National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029, Anhui (China); Zhang, Pengcheng, E-mail: zpc113@sohu.com [Science and Technology on Surface Physics and Chemistry Laboratory, Jiangyou 621908, Sichuan (China)

    2016-04-01

    The present study evaluates the microstructure in as-cast uranium rich U–Zr alloys, an important subsystem of U–Pu–Zr ternary metallic nuclear reactor fuel, as a function of the Zr content, from 2wt.% to 15wt.%Zr. It has been previously suggested that the unique intermetallic compound δ phase in U–Zr alloys is only present in as-cast U–Zr alloys with a Zr content exceeding 10wt.%Zr. However, our analysis of transmission electron microscopy (TEM) data shows that the δ phase is common to all as-cast alloys studied in this work. Furthermore, specific coherent orientation relationship is found between the α and δ phases, consistent with previous findings, and a third variant is discovered in this paper. - Highlights: • Initially, lattice parameter of as-cast U–Zr alloys decrease with the increasing Zr content, and then increase. • XRD data show the presence of δ-UZr{sub 2} phase in as-cast U–Zr alloys with a Zr content of more than 8wt.% Zr. • Finding δ-UZr{sub 2} phase exists in all as-cast uranium rich U–Zr alloys, even for alloys with a lean Zr content. • Three kinds of preferential orientations of the δ phase grow.

  8. Epithermal neutron instrumentation at ISIS

    International Nuclear Information System (INIS)

    Gorini, G; Festa, G; Andreani, C

    2014-01-01

    The advent of pulsed neutron sources makes available high epithermal neutron fluxes (in the energy range between 500 meV and 100 eV). New dedicated instrumentation, such as Resonance Detectors, was developed at ISIS spallation neutron source in the last years to apply the specific properties of this kind of neutron beam to the study of condensed matter. New detection strategies like Filter Difference method and Foil Cycling Technique were also developed in parallel to the detector improvement at the VESUVIO beamline. Recently, epithermal neutron beams were also used at the INES beamline to study elemental and isotopic composition of materials, with special application to cultural heritage studies. In this paper we review a series of epithermal neutron instrumentation developed at ISIS, their evolution over time and main results obtained

  9. A paleozoic pangaea.

    Science.gov (United States)

    Boucot, A J; Gray, J

    1983-11-11

    Paleozoic paleogeographies should be consistent with all available, reliable data. However, comparison of three different Devonian paleogeographies that are based largely or wholly on the data of remanent magnetism show them to be inconsistent in many regards. When these three paleogeographies are provided with possible ocean surface current circulation patterns, and have added to them lithofacies and biogeographic data, they also are shown to be inconsistent with such data. A pangaeic reconstruction positioned in the Southern Hemisphere permits the lithofacies and biogeographical data to be reconciled in a plausible manner.

  10. Influence of Uranium on Bacterial Communities: A Comparison of Natural Uranium-Rich Soils with Controls

    Science.gov (United States)

    Mondani, Laure; Benzerara, Karim; Carrière, Marie; Christen, Richard; Mamindy-Pajany, Yannick; Février, Laureline; Marmier, Nicolas; Achouak, Wafa; Nardoux, Pascal; Berthomieu, Catherine; Chapon, Virginie

    2011-01-01

    This study investigated the influence of uranium on the indigenous bacterial community structure in natural soils with high uranium content. Radioactive soil samples exhibiting 0.26% - 25.5% U in mass were analyzed and compared with nearby control soils containing trace uranium. EXAFS and XRD analyses of soils revealed the presence of U(VI) and uranium-phosphate mineral phases, identified as sabugalite and meta-autunite. A comparative analysis of bacterial community fingerprints using denaturing gradient gel electrophoresis (DGGE) revealed the presence of a complex population in both control and uranium-rich samples. However, bacterial communities inhabiting uraniferous soils exhibited specific fingerprints that were remarkably stable over time, in contrast to populations from nearby control samples. Representatives of Acidobacteria, Proteobacteria, and seven others phyla were detected in DGGE bands specific to uraniferous samples. In particular, sequences related to iron-reducing bacteria such as Geobacter and Geothrix were identified concomitantly with iron-oxidizing species such as Gallionella and Sideroxydans. All together, our results demonstrate that uranium exerts a permanent high pressure on soil bacterial communities and suggest the existence of a uranium redox cycle mediated by bacteria in the soil. PMID:21998695

  11. Mineral transformations and magnetic properties: example of an uranium rich front of oxido-reduction

    International Nuclear Information System (INIS)

    Mergaux, O.; Samama, J.C.

    1987-01-01

    In sedimentary environments, the mineral associations and the associated magnetic properties may be ascribed to superimposed processes of sedimentation, diagenesis and epigenesis. In the case of uranium sandstone deposits, the epigenetic processes of oxido-reduction are responsible for both concentration in uranium and specific mineral transformations which are related to variations in the magnetic properties of the rocks. These variations are illustrated by the Treville deposit (Southwestern France), where uranium rich bodies have developed within the Tertiary sandstones. The unaltered sandstones are characterized by a low magnetic susceptibility (scarcity of ferrimagnetic species but abundance of paramagnetic species). The siderite rich facies forming part of the front does not display any significant change in the mean magnetic susceptibility whilst the uranium-pyrite facies which belongs to the same front indicates a much lower susceptibility. The mean susceptibility facies resulting from pyrite and siderite oxidation remains unchanged. The facies of alteration of the iron rich silicates is responsible for higher susceptibility. The comparison between measured susceptibility and computed susceptibility helps in interpreting the role of the various species in the overall susceptibility of the rocks. It may also help in restituting the mineral associations from magnetic and chemical logging

  12. Titanate ceramics for immobilisation of uranium-rich radioactive wastes arising from {sup 99}Mo production

    Energy Technology Data Exchange (ETDEWEB)

    Carter, M.L.; Li, H. [Institute of Materials Engineering, Australian Nuclear Science and Technology Organisation, PMB 1, Menai, Sydney, NSW 2232 (Australia); Zhang, Y. [Institute of Materials Engineering, Australian Nuclear Science and Technology Organisation, PMB 1, Menai, Sydney, NSW 2232 (Australia)], E-mail: yzx@ansto.gov.au; Vance, E.R.; Mitchell, D.R.G. [Institute of Materials Engineering, Australian Nuclear Science and Technology Organisation, PMB 1, Menai, Sydney, NSW 2232 (Australia)

    2009-02-28

    Uranium-rich liquid wastes arising from UO{sub 2} targets which have been neutron-irradiated to generate medical radioisotopes such as {sup 99m}Tc require immobilisation. A pyrochlore-rich hot isostatically pressed titanate ceramic can accommodate at least 40 wt% of such waste expressed on an oxide basis. In this paper, the baseline waste form composition (containing 40 wt% UO{sub 2}) was adjusted in two ways: (a) varying the UO{sub 2} loading with constant precursor oxide materials, (b) varying the precursor composition with constant waste loading of UO{sub 2}. This resulted in the samples having a similar phase assemblage but the amounts of each phase varied. The oxidation states of U in selected samples were determined using diffuse reflection spectroscopy (DRS) and electron energy loss spectroscopy (EELS). Leaching studies showed that there was no significant difference in the normalised elemental release rates and the normalised release rates are comparable with those from synroc-C. This demonstrates that waste forms based on titanate ceramics are robust and flexible for the immobilisation of U-rich waste streams from radioisotope processing.

  13. Temperature imaging using epithermal neutrons

    International Nuclear Information System (INIS)

    Fowler, P.H.; Taylor, A.D.

    1987-08-01

    The paper concerns the temperature measurement of suitable targets, both remotely and non-invasively, using epithermal neutrons. The text was presented at the Neutron Resonance Radiography Workshop, Los Alamos, U.S.A., 1987. The technique is demonstrated for tantalum foils at different temperatures, using a pulsed beam of epithermal neutrons, at both Los Alamos and ISIS (United Kingdom). Results on the measured time-of-flight spectra and the tantalum resonances are presented. Beam properties and fluxes at ISIS are discussed. Features of the proposed detectors suitable for the temperature technique are outlined, along with the data analysis, the moving targets, the cyclic temperature variations and transients, and the usefulness of the technique. (U.K.)

  14. Epithermal interrogation of fissile waste

    International Nuclear Information System (INIS)

    Coop, K.L.; Hollas, C.L.

    1996-01-01

    Self-shielding of interrogating thermal neutrons in lumps of fissile material can be a major source of error in transuranic waste assay using the widely employed differential dieaway technique. We are developing a new instrument, the combined thermal/epithermal neutron (CTEN) interrogation instrument to detect the occurrence of self- shielding and mitigate its effects. Neutrons are moderated in the graphite walls of the CTEN instrument to provide an interrogating flux of epithermal and thermal neutrons. The induced prompt fission neutrons are detected in proportional counters. We report the results of measurements made with the CTEN instrument, using minimal and highly self-shielding plutonium and uranium sources in 55 gallon drums containing a variety of mock waste matrices. Fissile isotopes and waste forms for which the method is most applicable, and limitations associated with the hydrogen content of the waste package/matrix are described

  15. Polarized epithermal neutron spectrometer at KENS

    International Nuclear Information System (INIS)

    Kohgi, M.

    1983-01-01

    A spectrometer employing a white, epithermal, polarized neutron beam is under construction at KENS. The neutron polarization is achieved by passage through a dynamically polarized proton filter (DPPF). The results of the test experiments show that the DPPF method is promising in obtaining polarized epithermal neutron beam. The basic design of the spectrometer is described

  16. Analysis and exploitation of bacterial population from natural uranium-rich soils: selection of a model specie

    International Nuclear Information System (INIS)

    Mondani, L.

    2010-01-01

    It is well known that soils play a key role in controlling the mobility of toxic metals and this property is greatly influenced by indigenous bacterial communities. This study has been conducted on radioactive and controls soils, collected in natural uraniferous areas (Limousin). A physico-chemical and mineralogical analysis of soils samples was carried out.The structure of bacterial communities was estimated by Denaturing Gradient Gel Electrophoresis (DGGE). The community structure is remarkably more stable in the uranium-rich soils than in the control ones, indicating that uranium exerts a high selection from the soils was constructed and screened for uranium resistance in order to study bacteria-uranium interactions. Scanning electron microscopy revealed that a phylo-genetically diverse set of uranium-resistant species ware able to chelate uranium at the cell surface. (author) [fr

  17. Epithermal neutron beam interference with cardiac pacemakers

    International Nuclear Information System (INIS)

    Koivunoro, H.; Serén, T.; Hyvönen, H.; Kotiluoto, P.; Iivonen, P.; Auterinen, I.; Seppälä, T.; Kankaanranta, L.; Pakarinen, S.; Tenhunen, M.; Savolainen, S.

    2011-01-01

    In this paper, a phantom study was performed to evaluate the effect of an epithermal neutron beam irradiation on the cardiac pacemaker function. Severe malfunction occurred in the pacemakers after substantially lower dose from epithermal neutron irradiation than reported in the fast neutron or photon beams at the same dose rate level. In addition the pacemakers got activated, resulting in nuclides with half-lives from 25 min to 115 d. We suggest that BNCT should be administrated only after removal of the pacemaker from the vicinity of the tumor.

  18. Epithermal neutron beam interference with cardiac pacemakers

    Energy Technology Data Exchange (ETDEWEB)

    Koivunoro, H., E-mail: hanna.koivunoro@helsinki.fi [Department of Physics, P.O.B. 64, FI-00014 University of Helsinki (Finland)] [Department of Oncology, Helsinki University Central Hospital, P.O.B. 180, FIN-00029 HUS (Finland)] [Boneca Corporation, Finland, Filnland (Finland); Seren, T. [VTT Technical Research Centre of Finland (Finland); Hyvoenen, H. [Boneca Corporation, Finland, Filnland (Finland); Kotiluoto, P. [VTT Technical Research Centre of Finland (Finland); Iivonen, P. [St. Jude Medical (Finland); Auterinen, I. [VTT Technical Research Centre of Finland (Finland); Seppaelae, T.; Kankaanranta, L. [Department of Oncology, Helsinki University Central Hospital, P.O.B. 180, FIN-00029 HUS (Finland); Pakarinen, S. [Department of Cardiology, Helsinki University Central Hospital (Finland); Tenhunen, M. [Department of Oncology, Helsinki University Central Hospital, P.O.B. 180, FIN-00029 HUS (Finland); Savolainen, S. [HUS Helsinki Medical Imaging Center, Helsinki University Central Hospital (Finland)

    2011-12-15

    In this paper, a phantom study was performed to evaluate the effect of an epithermal neutron beam irradiation on the cardiac pacemaker function. Severe malfunction occurred in the pacemakers after substantially lower dose from epithermal neutron irradiation than reported in the fast neutron or photon beams at the same dose rate level. In addition the pacemakers got activated, resulting in nuclides with half-lives from 25 min to 115 d. We suggest that BNCT should be administrated only after removal of the pacemaker from the vicinity of the tumor.

  19. Characterisation of the TAPIRO BNCT epithermal facility

    Energy Technology Data Exchange (ETDEWEB)

    Burn, K. W. [FIS-NUC, ENEA, Via Martiri di Montesole 4, Bologna (Italy); Colli, V. [Dept. of Physics of Univ., INFN, Via Celoria 16, I-20133 Milano (Italy); Curzio, G.; D' Errico, F. [DIMNP, Univ. of Pisa, Via Diotisalvi 2, I-56126 Pisa (Italy); Gambarini, G. [Dept. of Physics of Univ., INFN, Via Celoria 16, I-20133 Milano (Italy); Rosi, G. [FIS-ION, ENEA, Casaccia, Via Anguillarese 301, I-00060 Santa Maria di Galeria, Roma (Italy); Scolari, L. [Dept. of Physics of Univ., INFN, Via Celoria 16, I-20133 Milano (Italy)

    2004-07-01

    A collimated epithermal beam for boron neutron capture therapy (BNCT) research has been designed and built at the TAPIRO fast research reactor. A complete experimental characterisation of the radiation field in the irradiation chamber has been performed, to verify agreement with IAEA requirements. Slow neutron fluxes have been measured by means of an activation technique and with thermoluminescent detectors (TLDs). The fast neutron dose has been determined with gel dosemeters, while the fast neutron spectrum has been acquired by means of a neutron spectrometer based on superheated drop detectors. The gamma-dose has been measured with gel dosemeters and TLDs. For an independent verification of the experimental results, fluxes, doses and neutron spectra have been calculated with Monte Carlo simulations using the codes MCNP4B and MCNPX 2.1.5 with the direct statistical approach (DSA). The results obtained confirm that the epithermal beams achievable at TAPIRO are of suitable quality for BNCT purposes. (authors)

  20. Polarized Epithermal Neutron Studies of Magnetic Domains

    International Nuclear Information System (INIS)

    Alfimenkov, V.P.; Chernikov, A.N.; Lason, L.; Mareev, Yu. D.; Novitsky, V.V.; Pikelner, L.B.; Skoy, V.R.; Tsulaya, M.I.; Gould, C.R.; Haase, D.G.; Roberson, N.R.

    1997-01-01

    The average size and shape of magnetic domains in a material can be determined from the precession of polarized neutrons traversing the material. Epithermal neutrons (0.5eV< En<100eV), which process more slowly than thermals, effectively probe the internal structure of samples that are thick or have large domains or large internal fields. Such epithermal neutron measurements require a neutron polarizer and analyzer based on cryogenically polarized spin filters. We discuss the measurements at JINR, Dubna, of magnetic domains in a 2.0 cm. diam. crystal of holmium using 1.7 to 59eV neutrons polarized by a dynamically polarized proton target and analyzed with a statically polarized dysprosium target

  1. Polarized epithermal neutron studies of magnetic domains

    International Nuclear Information System (INIS)

    Alfimenkov, V.P.; Chernikov, A.N.; Lason, L.; Mareev, Y.D.; Novitsky, V.V.; Pikelner, L.B.; Skoy, V.R.; Tsulaya, M.I.; Gould, C.R.; Haase, D.G.; the Triangle Universities Nuclear Laboratory, Durham, North Carolina; Roberson, N.R.; the Triangle Universities Nuclear Laboratory, Durham, North Carolina

    1997-01-01

    The average size and shape of magnetic domains in a material can be determined from the precession of polarized neutrons traversing the material. Epithermal neutrons (0.5eV n <100eV), which precess more slowly than thermals, effectively probe the internal structure of samples that are thick or have large domains or large internal fields. Such epithermal neutron measurements require a neutron polarizer and analyzer based on cryogenically polarized spin filters. We discuss the measurement at JINR, Dubna, of magnetic domains in a 2.0 cm. diam. crystal of holmium using 1.7 to 59 eV neutrons polarized by a dynamically polarized proton target and analyzed with a statically polarized dysprosium target. copyright 1997 American Institute of Physics

  2. Central Paleozoic prehistory of Vilyuyskiy syneclise

    Energy Technology Data Exchange (ETDEWEB)

    Ul' mesvay, F S

    1981-01-01

    Based on a study of lithological features of the central Paleozoic deposits of the Ygyattinskiy and Kempendyayskiy Basins, a comparison plan is developed. The main features of the middle Paleozoic history of the region are clarified. Their affiliation to a single structure of the avlakogen type is established. Based on the proximity of rock associations and time for development, a similarity of the studied region and the Pripyatskiy-Donets avlakogen has been established. A conclusion is drawn about the possible productivity of the middle Paleozoic deposits.

  3. Pulsed neutron sources for epithermal neutrons

    International Nuclear Information System (INIS)

    Windsor, C.G.

    1978-01-01

    It is shown how accelerator based neutron sources, giving a fast neutron pulse of short duration compared to the neutron moderation time, promise to open up a new field of epithermal neutron scattering. The three principal methods of fast neutron production: electrons, protons and fission boosters will be compared. Pulsed reactors are less suitable for epithermal neutrons and will only be briefly mentioned. The design principle of the target producing fast neutrons, the moderator and reflector to slow them down to epithermal energies, and the cell with its beam tubes and shielding will all be described with examples taken from the new Harwell electron linac to be commissioned in 1978. A general comparison of pulsed neutron performance with reactors is fraught with difficulties but has been attempted. Calculation of the new pulsed source fluxes and pulse widths is now being performed but we have taken the practical course of basing all comparisons on extrapolations from measurements on the old 1958 Harwell electron linac. Comparisons for time-of-flight and crystal monochromator experiments show reactors to be at their best at long wavelengths, at coarse resolution, and for experiments needing a specific incident wavelength. Even existing pulsed sources are shown to compete with the high flux reactors in experiments where the hot neutron flux and the time-of-flight methods can be best exploited. The sources under construction can open a new field of inelastic neutron scattering based on energy transfer up to an electron volt and beyond

  4. Epithermal neutron activation analysis of food

    International Nuclear Information System (INIS)

    Zikovsky, L.; Soliman, K.

    1999-01-01

    Food samples were irradiated with thermal and epithermal neutrons. The average ratios of thermal to epithermal activity were determined for 80 Br, 49 Ca, 38 Cl, 60m Co, 42 K, 27 Mg, 56 Mn, 24 Na, and 86m Rb. They were equal to 2.1, 26, 24, 6.6, 19, 16, 11, 23 and 1.9, respectively. Then, 57 food samples were analyzed by epithermal neutron activation analysis for Br and Rb. The concentrations (in ppm) of Br and Rb were in asparagus (2) 2.3, 11.5; beets (3) 0.5, 0.8; beef (3) 1.7, 3.6; cabbage (5) 0.5, 10.8; carrot (3) 0.2, 3.7; chicken (3) 0.6, 4.4; chocolate (7) 11.1, 18.7; egg (3) 0.9, 1.9; french bean (3) 0.3, 1.0; goose (2) 1.3, 9.3; lettuce (2) 0.9, 1.7; pork (1) 1.5, 4.4; potato (7) 1.0, 1.2; sausage (3) 4.8, 3.5; spinach (3) 3.6, 4.0; strawberry jam (3) 0.4, 1.4; tomato (1) 13.5, 14.6; turkey (3) 1.2, 4.9. respectively. The number of samples and analyzed is indicated in parentheses. (author)

  5. Design considerations for epithermal pulse reactors

    International Nuclear Information System (INIS)

    Ostensen, R.W.

    1978-01-01

    Simplified design criteria were developed for scoping analyses of epithermal pulse reactors for use in LMFBR safety testing. By using these criteria, materials and designs were investigated to determine performance limits of moderately sized reactor cores. Several designs are suggested for further study. These are a gas-cooled core fueled with a heterogeneous mixture of Fe-UO 2 cermet and BeO-UO 2 ceramic fuels, and a heavy-water-cooled core fueled with an Fe-UO 2 cermet

  6. From hot atom chemistry to epithermal chemistry

    International Nuclear Information System (INIS)

    Roessler, K.

    2004-01-01

    The rise and fall of hot atom chemistry (HAC) over the years from 1934 to 2004 is reviewed. Several applications are discussed, in particular to astrophysics and the interaction of energetic ions and atoms in space. Epithermal chemistry (ETC) is proposed to substitute the old name, since it better fits the energy range as well as the non-thermal and non-equilibrium character of the reactions. ETC also avoids the strong connexion of HAC to nuclear chemistry and stands for the opening of the field to physical chemistry and astrophysics. (orig.)

  7. Characteristic analysis on moderating material for obtaining epithermal neutron beam

    International Nuclear Information System (INIS)

    Jiang Xinbiao; Chen Da; Zhang Ying

    2000-01-01

    The one dimension discrete coordinates transport code ANISN was used to calculate three-group constants of 11 elements which could be used to consist moderating epithermal neutron material of beam. Moderating character of simple substances, compounds and mixtures consisted of the optimized elements analyzed three kinds of moderating materials were optimized for epithermal neutron beam

  8. Physics of epi-thermal boron neutron capture therapy (epi-thermal BNCT).

    Science.gov (United States)

    Seki, Ryoichi; Wakisaka, Yushi; Morimoto, Nami; Takashina, Masaaki; Koizumi, Masahiko; Toki, Hiroshi; Fukuda, Mitsuhiro

    2017-12-01

    The physics of epi-thermal neutrons in the human body is discussed in the effort to clarify the nature of the unique radiologic properties of boron neutron capture therapy (BNCT). This discussion leads to the computational method of Monte Carlo simulation in BNCT. The method is discussed through two examples based on model phantoms. The physics is kept at an introductory level in the discussion in this tutorial review.

  9. Paleozoic in situ spores and pollen. Lycopsida

    Czech Academy of Sciences Publication Activity Database

    Bek, Jiří

    2017-01-01

    Roč. 296, 1/6 (2017), s. 1-111 ISSN 0375-0299 R&D Projects: GA ČR GAP210/12/2053 Institutional support: RVO:67985831 Keywords : in situ spores * reproductive organs * Lycopsida * Paleozoic Sub ject RIV: DB - Geology ; Mineralogy OBOR OECD: Paleontology Impact factor: 1.333, year: 2016

  10. Epithermal gold occurrences in the lakes district of the Main ...

    African Journals Online (AJOL)

    MER). Epithermal gold occurrences related to Quaternary volcanics are at present being closely studied for their precious metal potential. Low sulphidation (Adularia-sericite-type) occurrences have been found. Analyses of 579 core and cutting ...

  11. Epithermal neutron activation analysis in applied microbiology

    International Nuclear Information System (INIS)

    Marina Frontasyeva

    2012-01-01

    Some results from applying epithermal neutron activation analysis at FLNP JINR, Dubna, Russia, in medical biotechnology, environmental biotechnology and industrial biotechnology are reviewed. In the biomedical experiments biomass from the blue-green alga Spirulina platensis (S. platensis) has been used as a matrix for the development of pharmaceutical substances containing such essential trace elements as selenium, chromium and iodine. The feasibility of target-oriented introduction of these elements into S. platensis biocomplexes retaining its protein composition and natural beneficial properties was shown. The absorption of mercury on growth dynamics of S. platensis and other bacterial strains was observed. Detoxification of Cr and Hg by Arthrobacter globiformis 151B was demonstrated. Microbial synthesis of technologically important silver nanoparticles by the novel actinomycete strain Streptomyces glaucus 71 MD and blue-green alga S. platensis were characterized by a combined use of transmission electron microscopy, scanning electron microscopy and energy-dispersive analysis of X-rays. It was established that the tested actinomycete S. glaucus 71 MD produces silver nanoparticles extracellularly when acted upon by the silver nitrate solution, which offers a great advantage over an intracellular process of synthesis from the point of view of applications. The synthesis of silver nanoparticles by S. platensis proceeded differently under the short-term and long-term silver action. (author)

  12. Boron thermal/epithermal neutron capture therapy

    International Nuclear Information System (INIS)

    Fairchild, R.G.

    1982-01-01

    The development of various particle beams for radiotherapy represents an attempt to improve dose distribution, and to provide high LET radiations which are less sensitive to ambient physical and radiobiological factors such as oxygen tension, cell cycle, and dose rate. In general, a compromise is necessary as effective RBE is reduced in order to spread the dose distribution over the anticipated tumor volume. The approach of delivering stable non-toxic isotopes to tumor, and then activating these atoms subsequently via an external radiation beam has mator advantages; problems associated with high uptake of these isotopes in competing cell pools are obviated, and the general tumor volume can be included in the treatment field of the activating beam. As long as the normal tissues supporting tumor show a low uptake of the isotope to be activated, and as long as the range of the reaction products is short, dose will be restricted to tumor, with a consequent high therapeutic ratio. Neutron Capture Therapy (NCT) is generally carried out by activating boron-10 with low energy neutrons. The range of the high LET, low OER particles from the 10 B(n, α) 7 Li reaction is approx. 10μ, or one cell diameter, a situation that is optimal for cell killing. Significant advantages may be gained by using the NCT procedure in conjunction with improved tissue penetration provided with epithermal or filtered beams, and new compounds showing physiological binding to tumor

  13. Method and apparatus for epithermal neutron porosity well logging

    International Nuclear Information System (INIS)

    Hertzog, R.C.; Loomis, W.A.; Wraight, P.

    1991-01-01

    This patent describes a method for investigating the porosity of a subsurface earth formation surrounding a borehole. It comprises repetitively irradiating the borehole and earth formation with discrete bursts of high energy neutrons from a neutron source, which neutrons interact with nuclei of the materials in the borehole and the formation to produce therein populations of epithermal neutrons; detecting the populations of epithermal neutrons at near and far locations in the borehole spaced apart longitudinally by different distances from the neutron source; generating count signals indicative of the magnitudes of the detected epithermal neutron populations at the respective near and far locations; detecting the decay of the epithermal neutron populations following the neutron bursts at least at one location in the borehole and generating signals representative thereof; deriving from the decay signals a signal indicative of the slowing down time of epithermal neutrons in the formation of the at least one location; and deriving from the near and far count signals and the slowing down time signal a measurement signal representative of the porosity of the formation surrounding the borehole inherently compensated for the effects of tool standoff on the responses of the logging tool

  14. Epithermal neutron activation analysis using a boron carbide irradiation filter

    International Nuclear Information System (INIS)

    Ehmann, W.D.; Brueckner, J.

    1980-01-01

    The use of boron carbide as a thermal neutron filter in epithermal neutron activation (ENAA) analysis has been investigated. As compared to the use of a cadmium filter, boron provides a greater reduction of activities from elements relatively abundant in terrestrial rocks and fossil fuels, such as Na, La, Sc and Fe. These elements have excitation functions which follow the 1/v law in the 1 to 10 eV lower epithermal region. This enhances the sensitivity of ENAA for elements such as U, Th, Ba and etc. which have strong resonances in the higher epithermal region above 10 eV. In addition, a boron carbide filter has the advantages over cadmium of acquiring a relatively low level of induced activity which poses minimal radiation safety problems, when used for ENAA. (author)

  15. Determination of silver using cyclic epithermal neutron activation analysis

    International Nuclear Information System (INIS)

    Pun, T.H.; Landsberger, S.

    2012-01-01

    A fast pneumatic transfer facility was installed in Nuclear Engineering Teaching Laboratory (NETL) of the University of Texas at Austin for the purpose of cyclic thermal and epithermal neutron activation analysis. In this study efforts were focused on the evaluation of cyclic epithermal neutron activation analysis (CENAA). Various NIST and CANMET certified materials were analyzed by the system. Experiment results showed 110 Ag with its 25 s half-life as one of the isotopes favored by the system. Thus, the system was put into practical application in identifying silver in metallic ores. Comparison of sliver concentrations as determined by CENAA in CANMET certified reference materials gave very good results. (author)

  16. Design of filtered epithermal neutron beams for BNC

    International Nuclear Information System (INIS)

    Greenwood, R.C.

    1986-01-01

    The design principles of filters (installed in nuclear reactors) to provide epithermal neutron beams suitable for use in 10 B Neutron Capture Therapy (BNCT) are reviewed. The goal of such filters is to provide epithermal neutron beams within an energy range of 1 keV to 30 keV with fluxes in excess of 5 x 10 8 neutrons/cm 2 .s, and having acceptably low contaminant fast neutron (> 30 keV) and gamma components. Filters considered for this application include 238 U, Sc, Fe/Al and Al/S. It is shown that in order to achieve a goal epithermal neutron flux of > 5 x 10 8 neutrons/cm 2 .s, such filters must be located in radial beam channels which view essentially the complete reactor core. Based on considerations of estimated epithermal fluxes, cost and availability of materials, and transmitted neutron energy spectrum, it is suggested that a filter consisting of elements of Al, S, Ti and V might prove to be an optimum design for BNCT applications. 13 references, 3 figures, 8 tables

  17. Collimator optimization studies for the new MIT epithermal neutron beam

    International Nuclear Information System (INIS)

    Riley, K.J.; Ali, S.J.; Harling, O.K.

    2000-01-01

    A patient collimator has been designed for the epithermal neutron facility now being commissioned at MIT. Collimator performance both in and out of field was evaluated using the Monte Carlo code MCNP. A two piece design that can accommodate different circular field sizes will be manufactured using a composite lead, epoxy, boron and lithium mixture. (author)

  18. Mechanical design of epithermal neutron diagnostic for TFTR

    International Nuclear Information System (INIS)

    Groo, R.C.

    1981-01-01

    The mechanical design of the Epithermal Neutron Diagnostic for TFTR is described. This fission detector system measures the time resolution of the neutron flux for folding into the Neutron Activation system and also provides continuous, wide range coverage of all expected fusion reaction rates

  19. Measurement of epithermal neutrons by a coherent demodulation technique

    CERN Document Server

    Horiuchi, N; Takahashi, H; Kobayashi, H; Harasawa, S

    2000-01-01

    Epithermal neutrons have been measured using a neutron dosimeter via a coherent demodulation technique. This dosimeter consists of CsI(Tl)-photodiode scintillation detectors, four of which are coupled to neutron-gamma converting foils of various sizes. Neutron-gamma converting foils of In, Au and Co materials were used, each of which has a large capture cross section which peaks in the epithermal neutron energy region. The type of foil was selected according to the material properties that best correspond to the energy of the epithermal neutrons to be measured. In addition, the proposed technique was applied using Au-foils in order to measure the Cd ratio. The validity of the proposed technique was examined using an sup 2 sup 4 sup 1 Am-Be source placed in a testing stack of polyethylene blocks, and the results were compared with the theoretical values calculated by the Monte Carlo calculation. Finally, the dosimeter was applied for measuring epithermal neutrons and the Cd ratio in an experimental beam-tube o...

  20. Plate tectonics in the late Paleozoic

    Directory of Open Access Journals (Sweden)

    Mathew Domeier

    2014-05-01

    Full Text Available As the chronicle of plate motions through time, paleogeography is fundamental to our understanding of plate tectonics and its role in shaping the geology of the present-day. To properly appreciate the history of tectonics—and its influence on the deep Earth and climate—it is imperative to seek an accurate and global model of paleogeography. However, owing to the incessant loss of oceanic lithosphere through subduction, the paleogeographic reconstruction of ‘full-plates’ (including oceanic lithosphere becomes increasingly challenging with age. Prior to 150 Ma ∼60% of the lithosphere is missing and reconstructions are developed without explicit regard for oceanic lithosphere or plate tectonic principles; in effect, reflecting the earlier mobilistic paradigm of continental drift. Although these ‘continental’ reconstructions have been immensely useful, the next-generation of mantle models requires global plate kinematic descriptions with full-plate reconstructions. Moreover, in disregarding (or only loosely applying plate tectonic rules, continental reconstructions fail to take advantage of a wealth of additional information in the form of practical constraints. Following a series of new developments, both in geodynamic theory and analytical tools, it is now feasible to construct full-plate models that lend themselves to testing by the wider Earth-science community. Such a model is presented here for the late Paleozoic (410–250 Ma together with a review of the underlying data. Although we expect this model to be particularly useful for numerical mantle modeling, we hope that it will also serve as a general framework for understanding late Paleozoic tectonics, one on which future improvements can be built and further tested.

  1. Age and tectonomagmatic setting of the Eocene Çöpler-Kabataş magmatic complex and porphyry-epithermal Au deposit, East Central Anatolia, Turkey

    Science.gov (United States)

    İmer, Ali; Richards, Jeremy P.; Creaser, Robert A.

    2013-06-01

    The Çöpler epithermal Au deposit and related subeconomic porphyry Cu-Au deposit is hosted by the middle Eocene Çöpler-Kabataş magmatic complex in central eastern Anatolia. The intrusive rocks of the complex were emplaced into Late Paleozoic-Mesozoic metamorphosed sedimentary basement rocks near the northeastern margin of the Tauride-Anatolide Block. Igneous biotite from two samples of the magmatic complex yielded 40Ar/39Ar plateau ages of 43.75 ± 0.26 Ma and 44.19 ± 0.23, whereas igneous hornblende from a third sample yielded a plateau age of 44.13 ± 0.38. These ages closely overlap with 40Ar/39Ar ages of hydrothermal sericite (44.44 ± 0.28 Ma) and biotite (43.84 ± 0.26 Ma), and Re-Os ages from two molybdenite samples (44.6 ± 0.2 and 43.9 ± 0.2 Ma) suggesting a short-lived (history at Çöpler. No suitable minerals were found that could be used to date the epithermal system, but it is inferred to be close in age to the precursor porphyry system. The Çöpler-Kabataş intrusive rocks show I-type calc-alkaline affinities. Their normalized trace element patterns show enrichments in large ion lithophile and light rare earth elements and relative depletions in middle and heavy rare earth elements, resembling magmas generated in convergent margins. However, given its distance from the coeval Eocene Maden-Helete volcanic arc, the complex is interpreted to be formed in a back-arc setting, in response to Paleocene slab roll-back and upper-plate extension. The tectonomagmatic environment of porphyry-epithermal mineralization at Çöpler is comparable to some other isolated back-arc porphyry systems such as Bajo de la Alumbrera (Argentina) or Bingham Canyon (USA).

  2. Fundamental symmetry studies at Los Alamos using epithermal neutrons

    International Nuclear Information System (INIS)

    Bowman, C.D.; Bowman, J.D.; Yuan, V.W.

    1988-01-01

    Fundamental symmetry studies using intense polarized beams of epithermal neutrons are underway at the LANSCE facility of the Los Alamos National Laboratory. Three classes of symmetry experiments can be explored: parity violation, and time reversal invariance violation for both parity-violating and parity-conserved observables. The experimental apparatus is described and performance illustrated with examples of recent measurements. Possible improvements in the facilities and prospective experiments are discussed. 15 refs., 10 figs

  3. VLAD for epithermal neutron scattering experiments at large energy transfers

    International Nuclear Information System (INIS)

    Tardocchi, M; Gorini, G; Perelli-Cippo, E; Andreani, C; Imberti, S; Pietropaolo, A; Senesi, R; Rhodes, N R; Schooneveld, E M

    2006-01-01

    The Very Low Angle Detector (VLAD) bank will extend the kinematical region covered by today's epithermal neutron scattering experiments to low momentum transfer ( -1 ) together with large energy transfer 0 -4 0 . In this paper the design of VLAD is presented together with Montecarlo simulations of the detector performances. The results of tests made with prototype VLAD detectors are also presented, confirming the usefulness of the Resonance Detector for measurements at very low scattering angles

  4. Determination of epithermal flux correction factor (α) for irradiation ...

    African Journals Online (AJOL)

    Due to resonance that occur in the epithermal energy region of a reactor, the flux spectra in that region deviates strongly from the ideal I/E law to a I/E1+α with alpha as the correction factor. The factor has to be determined if zirconium as monitor pairs to determine the correction factor for inner irradiation channel 5 and outer ...

  5. New data on the Paleozoic of the Semipalatinsk test site

    International Nuclear Information System (INIS)

    Ergaliev, G.Kh.; Myasnikov, A.K.; Nikitin, I.F.; Polyanskij, N.V.; Sergeeva, L.V.; Sergieva, M.N.; Sal'menova, L.T.; Utegulov, M.T.; Tsaj, D.T.; Shuzhanov, V.M.

    1998-01-01

    The latest data on Paleozoic of the Semipalatinsk test site acquired as result of the stratigraphic and pale ontological investigation which have been conducted for the first time after 46-year interval in geological studies are presented. (author)

  6. Critical elements in Carlin, epithermal, and orogenic gold deposits

    Science.gov (United States)

    Goldfarb, Richard J.; Hofstra, Albert H.; Simmons, Stuart F.

    2016-01-01

    Carlin, epithermal, and orogenic gold deposits, today mined almost exclusively for their gold content, have similar suites of anomalous trace elements that reflect similar low-salinity ore fluids and thermal conditions of metal transport and deposition. Many of these trace elements are commonly referred to as critical or near-critical elements or metals and have been locally recovered, although typically in small amounts, by historic mining activities. These elements include As, Bi, Hg, In, Sb, Se, Te, Tl, and W. Most of these elements are now solely recovered as by-products from the milling of large-tonnage, base metal-rich ore deposits, such as porphyry and volcanogenic massive sulfide deposits.A combination of dominance of the world market by a single country for a single commodity and a growing demand for many of the critical to near-critical elements could lead to future recovery of such elements from select epithermal, orogenic, or Carlin-type gold deposits. Antimony continues to be recovered from some orogenic gold deposits and tellurium could potentially be a primary commodity from some such deposits. Tellurium and indium in sphalerite-rich ores have been recovered in the past and could be future commodities recovered from epithermal ores. Carlin-type gold deposits in Nevada are enriched in and may be a future source for As, Hg, Sb, and/or Tl. Some of the Devonian carbonaceous host rocks in the Carlin districts are sufficiently enriched in many trace elements, including Hg, Se, and V, such that they also could become resources. Thallium may be locally enriched to economic levels in Carlin-type deposits and it has been produced from Carlin-like deposits elsewhere in the world (e.g., Alsar, southern Macedonia; Lanmuchang, Guizhou province, China). Mercury continues to be recovered from shallow-level epithermal deposits, as well as a by-product of many Carlin-type deposits where refractory ore is roasted to oxidize carbon and pyrite, and mercury is then

  7. Upgrade for the epithermal neutron beam at NRI Rez

    International Nuclear Information System (INIS)

    Marek, M.; Flibor, S.; Viererbl, L.; Burian, J.; Rejchrt, J.; Klupak, V.; Gambarini, G.; Vanossi, E.

    2006-01-01

    The epithermal neutron beam facility designed for pre-clinical neutron capture therapy research has been operated at LVR-15 reactor for more than ten years. The construction of the beam filter has been recently modified especially for the shielding quality of the beam shutter to be improved. The parameters of the upgraded beam were calculated with the MCNP code and a new source term for the NCTPLAN treatment planning software was evaluated. The calculated source term was consequently scaled according to the results of measurements in the free beam and in the 50x50x25 cm 3 water phantom. (author)

  8. Conversion ratio in epithermal PWR, in thorium and uranium cycle

    International Nuclear Information System (INIS)

    Barroso, D.E.G.

    1982-01-01

    Results obtained for the conversion ratio in PWR reactors with close lattices, operating in thorium and uranium cycles, are presented. The study of those reactors is done in an unitary fuel cell of the lattices with several ratios V sub(M)/V sub(F), considering only the equilibrium cycles and adopting a non-spatial depletion calculation model, aiming to simulate mass flux of reactor heavy elements in the reactor. The neutronic analysis and the cross sections generation are done with Hammer computer code, with one critical apreciation about the application of this code in epithermal systems and with modifications introduced in the library of basic data. (E.G.) [pt

  9. Magmatism and petroleum exploration in the Brazilian Paleozoic basins

    Energy Technology Data Exchange (ETDEWEB)

    Thomaz Filho, Antonio; Antonioli, Luzia [Universidade do Estado do Rio de Janeiro, Faculdade de Geologia, Rua Sao Francisco Xavier, no 524/2030, CEP 20550-900, Rio de Janeiro, RJ (Brazil); Mizusaki, Ana Maria Pimentel [Universidade Federal do Rio Grande do Sul, Instituto de Geociencias, Avenida Bento Goncalves, no 9500, Campus do Vale, CEP 91509-900, Porto Alegre, RS (Brazil)

    2008-02-15

    Petroleum exploration in the Paleozoic sedimentary basins of Brazil has proven very challenging for explorationists. Except for the Solimoes Basin, in which transcurrent tectonism formed prospective structural highs, Brazilian Paleozoic basins lack intense structural deformation, and hence the detection and prospecting of place is often difficult. Magmatic intrusive and associated rocks in all these basins have traditionally been considered heat sources and hydrocarbon traps. The role of tholeiitic basic dikes in the generation, migration and accumulation of petroleum in the Anhembi oil occurrence (Sao Paulo State) is discussed herein. It follows that similar geological settings in other Paleozoic basins can be regarded as promising sites for oil accumulation that warrant investigation via modern geological and geophysical methods. (author)

  10. Fast and epithermal neutron radiography using neutron irradiator

    International Nuclear Information System (INIS)

    Oliveira, Karol A.M. de; Crispim, Verginia R.; Ferreira, Francisco J.O.

    2013-01-01

    The neutron radiography technique (NR) with neutrons in the energy range fast to epithermal is a powerful tool used in no-destructive inspection of bulky objects of diverse materials, including those rich in hydrogen, oxygen, nitrogen ad carbon. Thus, it can be used to identify, inclusions, voids and thickness differences in materials such as explosive artifacts and narcotics. Aiming at using NR with fast and epithermal neutrons, an Irradiator was constructed by: a 241 Am-Be source, with 5 Ci activity, a collimator with adjustable collimation rate, L/D; and a shield device composed by plates of borated paraffin and iron. The test specimens chosen were a Beam Purity Indicator (BPI) and an Indicator of Visual Resolution (IVR). The neutron radiography images obtained had a resolution of 444.4 μm and 363.6 μm respectively when registered in: 1) the sheet of the nuclear track solid detector, CR-39 type, through X (n,p) Y nuclear reaction; and 2) Kodak Industrex M radiographic film plate in close contact with a boron converter screen, both stored in a Kodak radiographic cassette. (author)

  11. Determination of the thermal and epithermal neutron sensitivities of an LBO chamber

    Energy Technology Data Exchange (ETDEWEB)

    Endo, Satoru; Kotani, Kei; Kajimoto, Tsuyoshi; Tanaka, Kenichi [Hiroshima University, Quantum Energy Applications, Graduate School of Engineering, Higashi-Hiroshima (Japan); Sato, Hitoshi; Nakajima, Erika [Ibaraki Prefectural University of Health Science, Radiological Sciences, Ibaraki (Japan); Shimazaki, Takuto [Hiroshima University, Quantum Energy Applications, Graduate School of Engineering, Higashi-Hiroshima (Japan); Delta Kogyo Co., Ltd., Hiroshima (Japan); Suda, Mitsuru; Hamano, Tsuyoshi [National Institute of Radiological Sciences, Chiba-Shi, Chiba (Japan); Hoshi, Masaharu [Hiroshima University, Institute for Peace Science, Hiroshima (Japan)

    2017-08-15

    An LBO (Li{sub 2}B{sub 4}O{sub 7}) walled ionization chamber was designed to monitor the epithermal neutron fluence in boron neutron capture therapy clinical irradiation. The thermal and epithermal neutron sensitivities of the device were evaluated using accelerator neutrons from the {sup 9}Be(d, n) reaction at a deuteron energy of 4 MeV (4 MeV d-Be neutrons). The response of the chamber in terms of the electric charge induced in the LBO chamber was compared with the thermal and epithermal neutron fluences measured using the gold-foil activation method. The thermal and epithermal neutron sensitivities obtained were expressed in units of pC cm{sup 2}, i.e., from the chamber response divided by neutron fluence (cm{sup -2}). The measured LBO chamber sensitivities were 2.23 x 10{sup -7} ± 0.34 x 10{sup -7} (pC cm{sup 2}) for thermal neutrons and 2.00 x 10{sup -5} ± 0.12 x 10{sup -5} (pC cm{sup 2}) for epithermal neutrons. This shows that the LBO chamber is sufficiently sensitive to epithermal neutrons to be useful for epithermal neutron monitoring in BNCT irradiation. (orig.)

  12. Tracking the multi-stage exhumation history of the western Chinese Tianshan by Apatite Fission Track (AFT) dating - Implications for the preservation of epithermal deposits in ancient orogenic belt

    Science.gov (United States)

    Wang, Yannan; Cai, Keda

    2017-04-01

    The western Chinese Tianshan, located in the southern domain of the Central Asian Orogenic Belt (CAOB), was originally constructed by multiple accretion-collision processes in the Paleozoic, and was superimposed by complex intracontinental tectonic evolution in the Mesozoic-Cenozoic. Understanding the timing and mechanism of the latter geological processes is critical to unravel the preservation conditions of the epithermal deposits in the western Chinese Tianshan. This work presents new apatite fission track (AFT) data for three mountain ranges of the western Chinese Tianshan to track their exhumation history. Our AFT data gave a wide range of ages from 76.8 ± 5.5 Ma to 182.3 ± 9.9 Ma, and the mean confined fission track lengths are between 9.8 ± 0.5 μm and 12.3 ± 0.2 μm. The new data, in combination with the thermal history modeling,enable us to attribute the exhumation history to three primary stages, including Early Permian (300-280 Ma), Late Triassic-Early Cretaceous (230-130 Ma), and Late Oligocene-Early Miocene (30-20 Ma). The first stage may be caused by the terrane accretion-collision in the late Paleozoic. The second stage was likely related to the closure of the Mongol-Okhotsk Ocean during the Mesozoic. The last one is regarded as the result of the collision between the Indian Plate and the Eurasia Plate in the Cenozoic. The extraordinary exhumation processes of these three major mountain ranges might have been responsible for sediment supply to the corresponding intra-mountain basins in the western Chinese Tianshan, and the particularly mountain-basin coupling evolution is ascribed to an essential condition for the preservation of epithermal deposits in ancient orogenic belt.

  13. Spherical Harmonics Treatment of Epithermal Neutron Spectra in Reactor lattices

    International Nuclear Information System (INIS)

    Matausek, M.V.

    1972-04-01

    A procedure has been developed to solve the slowing down transport equation for neutrons in a cylindrized reactor lattice cell. Treating the anisotropy of the epithermal neutron flux by the spherical harmonics formalism, which reduces the space-angle-lethargy-dependent transport equation to the matrix integrodifferential equation in space and lethargy, and replacing the lethargy transfer integrals by finite-difference forms, a set of matrix ordinary differential equations, with lethargy and space dependent coefficients, is obtained. In the resonance region this set takes a lower block triangular form and can be directly solved by forward block substitution; in the lethargy range, where the fast fission effects have to be considered, the iterative procedure is introduced. A simple and efficient approximation is then proposed, making possible the analytical solution for the spatial dependence of the spherical harmonics flux moments. The proposed procedure has been numerically examined and approved. Some typical results are presented and discussed. (author)

  14. Final design and construction issues of the TAPIRO epithermal column

    International Nuclear Information System (INIS)

    Burn, K.W.; Casalini, L.; Nava, E.; Tinti, R.; Martini, S.; Mondini, D.; Rosi, G.

    2006-01-01

    The construction of the epithermal column for clinical trials at the 5 kW fast reactor TAPIRO (ENEA, Casaccia, Italy) has been completed, the experimental bunker in the reactor hall has been designed and the beam characterisation will shortly be underway. As has been reviewed at the last two ICNCT conferences, the low power of the neuron source and the relatively distant patient position outside the reactor shield led to a column design with certain characteristics. One consequence is the employment of a collimator containing lead of high purity with the resultant problems of mechanical construction. Another is the substantial neutron leakage from the column outside the aperture into the experimental bunker. Furthermore the absence of a gamma shield has led to an electron dose to the skin. This is resolved with an electron shield of aluminium. Here the construction and final design issues are discussed and the state of the project is presented. (author)

  15. The epithermal neutron-flux distribution in the reactor RA - Vinca

    International Nuclear Information System (INIS)

    Marinkov, V.; Bikit, I.; Martinc, R.; Veskovic, M.; Slivka, J.; Vaderna, S.

    1987-01-01

    The distribution of the epithermal neutron flux in the reactor RA - Vinca has been measured by means of Zr - activation detectors. In the channel VK-8 non-homogeneous flux distribution was observed (author) [sr

  16. MCNP study for epithermal neutron irradiation of an isolated liver at the Finnish BNCT facility.

    Science.gov (United States)

    Kotiluoto, P; Auterinen, I

    2004-11-01

    A successful boron neutron capture treatment (BNCT) of a patient with multiple liver metastases has been first given in Italy, by placing the removed organ into the thermal neutron column of the Triga research reactor of the University of Pavia. In Finland, FiR 1 Triga reactor with an epithermal neutron beam well suited for BNCT has been extensively used to irradiate patients with brain tumors such as glioblastoma and recently also head and neck tumors. In this work we have studied by MCNP Monte Carlo simulations, whether it would be beneficial to treat an isolated liver with epithermal neutrons instead of thermal ones. The results show, that the epithermal field penetrates deeper into the liver and creates a build-up distribution of the boron dose. Our results strongly encourage further studying of irradiation arrangement of an isolated liver with epithermal neutron fields.

  17. Upgrades of the epithermal neutron beam at the Brookhaven Medical Research Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Hungyuan B.; Brugger, R.M.; Rorer, D.C.

    1994-12-31

    The first epithermal neutron beam at the Brookhaven Medical Research Reactor (BMRR) was installed in 1988 and produced a neutron beam that was satisfactory for the development of NCT with epithermal neutrons. This beam was used routinely until 1992 when the beam was upgraded by rearranging fuel elements in the reactor core to achieve a 50% increase in usable flux. Next, after computer modeling studies, it was proposed that the Al and Al{sub 2}O{sub 3} moderator material in the shutter that produced the epithermal neutrons could be rearranged to enhance the beam further. However, this modification was not started because a better option appeared, namely to use fission plates to move the source of fission neutrons closer to the moderator and the patient irradiation position to achieve more efficient moderation and production of epithermal neutrons. A fission plate converter (FPC) source has been designed recently and, to test the concept, implementation of this upgrade has started. The predicted beam parameters will be 12 x 10{sup 9} n{sub epi}/cm{sup 2}sec accompanying with doses from fast neutrons and gamma rays per epithermal neutron of 2.8 x 10{sup -11} and < 1 x 10{sup -11} cGycm{sup 2}/n, respectively, and a current-to-flux ratio of epithermal neutrons of 0.78. This conversion could be completed by late 1996.

  18. Tectonic model for the Late Paleozoic of southeastern New England

    Energy Technology Data Exchange (ETDEWEB)

    Wintsch, R.P.; Sutter, J.F.

    1986-07-01

    Hornblende and biotite /sup 40/Ar//sup 39/Ar age spectra from rocks in south-central Connecticut help define a Permian-Triassic cooling curve for the area. Together with petrologic and structural information, a time-temperature-pressure-strain path is established. Similar data for the Narragansett basin in Rhode Island and Massachusetts allow correlation of the late Paleozoic histories of the two areas. Together, these data suggest that in the late Paleozoic, south-central New England was part of a fold-thrust belt, and the Narragansett basin was a retroarc foreland basin. NW-SE compression during the final assembly of Pangaea resulted in SE directed thrusting, causing the development of clastic wedges in adjacent Rhode Island and Massachusetts in the Late Carboniferous-Early Permian. A clockwise rotation of this deformation from NW to NNE led to northward underthrusting and concomitant uplift of both eastern Connecticut and Rhode Island in the Permian and Triassic.

  19. Isotopic tracers of gold deposition in Paleozoic limestones, Southern Nevada

    International Nuclear Information System (INIS)

    Peterman, Z.E.; Widmann, B.L.; Marshall, B.D.; Aleinikoff, J.N.; Futa, K.; Mahan, S.A.

    1994-01-01

    Strontium isotopic analyses of barren and mineralized Paleozoic carbonate rocks show that hydrothermal fluids added radiogenic strontium ( 87 Sr) to the mineralized zones. At Bare Mountain, samples collected from mineralized areas have δ 87 Sr t values ranging from +3.0 to +23.0, whereas unmineralized carbonate rocks have δ 87 Sr, values of -0.6 to +2.9. In other ranges, δ 87 Sr, values of the unmineralized carbonate rocks are even lower and virtually indistinguishable from primary marine values. This correlation of elevated δ 87 Sr t values with mineralized zones provides a useful technique for assessing the mineral potential of the Paleozoic basement beneath Yucca Mountain, and may find broader use in mineral exploration in the Basin and Range province as a whole

  20. Paleozoic stratigraphy of two areas in southwestern Indiana

    International Nuclear Information System (INIS)

    Droste, J.B.

    1976-09-01

    Two areas recommended for evaluation as solid waste disposal sites lie along the strike of Paleozoic rocks in southwestern Indiana. Thin Pennsylvanian rocks and rocks of the upper Mississippian are at the bedrock surface in maturely dissected uplands in both areas. The gross subsurface stratigraphy beneath both areas is the same, but facies and thickness variation in some of the subsurface Paleozoic units provide for some minor differences between the areas. Thick middle Mississippi carbonates grade downward into clastics of lower Mississippian (Borden Group) and upper Devonian (New Albany Shale) rocks. Middle Devonian and Silurian rocks are dominated by carbonate lithologies. Upper Ordovician (Maquoketa Group) overly carbonates of middle Ordovician age. Thick siltstone and shale of the Borden Group-New Albany Shale zone and Maquoketa Group rocks should be suitable for repository development

  1. Ontogenetic evidence for the Paleozoic ancestry of salamanders.

    Science.gov (United States)

    Schoch, Rainer R; Carroll, Robert L

    2003-01-01

    The phylogenetic positions of frogs, salamanders, and caecilians have been difficult to establish. Data matrices based primarily on Paleozoic taxa support a monophyletic origin of all Lissamphibia but have resulted in widely divergent hypotheses of the nature of their common ancestor. Analysis that concentrates on the character states of the stem taxa of the extant orders, in contrast, suggests a polyphyletic origin from divergent Paleozoic clades. Comparison of patterns of larval development in Paleozoic and modern amphibians provides a means to test previous phylogenies based primarily on adult characteristics. This proves to be highly informative in the case of the origin of salamanders. Putative ancestors of salamanders are recognized from the Permo-Carboniferous boundary of Germany on the basis of ontogenetic changes observed in fossil remains of larval growth series. The entire developmental sequence from hatching to metamorphosis is revealed in an assemblage of over 600 specimens from a single locality, all belonging to the genus Apateon. Apateon forms the most speciose genus of the neotenic temnospondyl family Branchiosauridae. The sequence of ossification of individual bones and the changing configuration of the skull closely parallel those observed in the development of primitive living salamanders. These fossils provide a model of how derived features of the salamander skull may have evolved in the context of feeding specializations that appeared in early larval stages of members of the Branchiosauridae. Larvae of Apateon share many unique derived characters with salamanders of the families Hynobiidae, Salamandridae, and Ambystomatidae, which have not been recognized in any other group of Paleozoic amphibians.

  2. The impact of fire on the Late Paleozoic Earth System

    Directory of Open Access Journals (Sweden)

    Ian J. Glasspool

    2015-09-01

    Full Text Available Analyses of bulk petrographic data indicate that during the Late Paleozoic wildfires were more prevalent than at present. We propose that the development of fire systems through this interval was controlled predominantly by the elevated atmospheric oxygen concentration (p(O2 that mass balance models predict prevailed. At higher levels of p(O2, increased fire activity would have rendered vegetation with high moisture contents more susceptible to ignition and would have facilitated continued combustion. We argue that coal petrographic data indicate that p(O2 rather than global temperatures or climate, resulted in the increased levels of wildfire activity observed during the Late Paleozoic and can therefore be used to predict it. These findings are based upon analyses of charcoal volumes in multiple coals distributed across the globe and deposited during this time period, and that were then compared with similarly diverse modern peats and Cenozoic lignites and coals. Herein, we examine the environmental and ecological factors that would have impacted fire activity and we conclude that of these factors p(O2 played the largest role in promoting fires in Late Paleozoic peat-forming environments and, by inference, ecosystems generally, when compared with their prevalence in the modern world.

  3. The impact of fire on the Late Paleozoic Earth system.

    Science.gov (United States)

    Glasspool, Ian J; Scott, Andrew C; Waltham, David; Pronina, Natalia; Shao, Longyi

    2015-01-01

    Analyses of bulk petrographic data indicate that during the Late Paleozoic wildfires were more prevalent than at present. We propose that the development of fire systems through this interval was controlled predominantly by the elevated atmospheric oxygen concentration (p(O2)) that mass balance models predict prevailed. At higher levels of p(O2), increased fire activity would have rendered vegetation with high-moisture contents more susceptible to ignition and would have facilitated continued combustion. We argue that coal petrographic data indicate that p(O2) rather than global temperatures or climate, resulted in the increased levels of wildfire activity observed during the Late Paleozoic and can, therefore, be used to predict it. These findings are based upon analyses of charcoal volumes in multiple coals distributed across the globe and deposited during this time period, and that were then compared with similarly diverse modern peats and Cenozoic lignites and coals. Herein, we examine the environmental and ecological factors that would have impacted fire activity and we conclude that of these factors p(O2) played the largest role in promoting fires in Late Paleozoic peat-forming environments and, by inference, ecosystems generally, when compared with their prevalence in the modern world.

  4. Paleozoic and Mesozoic deformations in the central Sierra Nevada, California

    Science.gov (United States)

    Nokleberg, Warren J.; Kistler, Ronald Wayne

    1980-01-01

    Analysis of structural and stratigraphic data indicates that several periods of regional deformation, consisting of combined folding, faulting, cataclasis, and regional metamorphism, occurred throughout the central Sierra Nevada during Paleozoic and Mesozoic time. The oldest regional deformation occurred alono northward trends during the Devonian and Mississippian periods in most roof pendants containing lower Paleozoic metasedimentary rocks at the center and along the crest of the range. This deformation is expressed in some roof pendants by an angular unconformity separating older thrice-deformed from younger twice-deformed Paleozoic metasedimentary rocks. The first Mesozoic deformation, which consisted of uplift and erosion and was accompanied by the onset of Andean-type volcanism during the Permian and Triassic, is expressed by an angular unconformity in several roof pendants from the Saddlebag Lake to the Mount Morrison areas. This unconformity is defined by Permian and Triassic andesitic to rhyolitic metavolcanic rocks unconformably overlying more intensely deformed Pennsylvanian, Permian(?), and older metasedimentary rocks. A later regional deformation occurred during the Triassic along N. 20?_30? W. trends in Permian and Triassic metavolcanic rocks of the Saddlebag Lake and Mount Dana roof pendants, in upper Paleozoic rocks of the Pine Creek roof pendant, and in the Calaveras Formation of the western metamorphic belt; the roof pendants are crosscut by Upper Triassic granitic rocks of the Lee Vining intrusive epoch. A still later period of Early and Middle Jurassic regional deformation occurred along N. 30?-60? E. trends in upper Paleozoic rocks of the Calaveras Formation of the western metamorphic belt. A further period of deformation was the Late Jurassic Nevadan orogeny, which occurred along N. 20?_40? W. trends in Upper Jurassic rocks of the western metamorphic belt that are crosscut by Upper Jurassic granitic rocks of the Yosemite intrusive epoch

  5. Geochronological framework of the early Paleozoic Bainaimiao Cu-Mo-Au deposit, NE China, and its tectonic implications

    Science.gov (United States)

    Zhou, Zhen-Hua; Mao, Jing-Wen; Ma, Xing-Hua; Che, He-Wei; Ou'yang, He-Gen; Gao, Xu

    2017-08-01

    The Bainaimiao Cu-Mo-Au deposit of NE China is an important ore deposit in the middle section of the northern margin of the North China Craton. The early Paleozoic Bainaimiao Group is the main ore-hosting rock. The mineralization at the deposit shows features of porphyry alteration and late-stage orogenesis and transformation. Zircon LA-ICP-MS U-Pb age data indicate that the ages of the Third and Fifth formations of the Bainaimiao Group are 492.7 ± 2.9 Ma (MSWD = 0.53) and 488.9 ± 3.1 Ma (MSWD = 0.92), respectively. The age of quartz diorite that intrudes the Bainaimiao Group is 459.3 ± 6.4 Ma (MSWD = 2.20). Molybdenite samples from massive Cu-Mo-bearing ores and quartz veins in the southern ore belt yield a Re-Os isochron age of 438.2 ± 2.7 Ma (MSWD = 0.16), which is consistent with the Re-Os isochron age of molybdenite in the northern ore belt, implying that the two ore belts belong to the same mineralization system. Muscovite from a post-magmatic Cu-Mo-bearing quartz-calcite vein yields an Ar-Ar isochron age of 422.5 ± 3.9 Ma (MSWD = 0.64) with an initial 40Ar/36Ar ratio of 286 ± 21. The well-defined plateau age of the muscovite is 422.4 ± 2.6 Ma (MSWD = 0.05), which represents the time of the post-magmatic orogenic transformation event. Based on our new age data and previous findings, we propose that the Bainaimiao Cu-Mo-Au deposit formed in an active continental margin setting and experienced four stages of ore mineralization: (1) a Late Cambrian-Middle Ordovician volcanic-sedimentary stage; (2) a Late Ordovician porphyry mineralization stage; (3) a Late Silurian regional metamorphism stage; and (4) an orogenic transformation stage. Subhedral and euhedral Paleoproterozoic (2402-1810 Ma) inherited zircons indicate that the Bainaimiao Group has a tectonic affinity with the North China Craton. The Central Asian Orogenic Belt, which is closely related to the complex closure of the Paleo-Asian Ocean, is favorable for prospecting for Paleozoic porphyry Cu

  6. Epithermal neutron activation analysis for studying the environment

    International Nuclear Information System (INIS)

    Frontas'eva, M.V.; Steinnes, E.

    1997-01-01

    Epithermal neutron activation analysis (ENAA) has certain advantages over the conventional instrumental analysis (INAA) in terms of improvement in precision and lowering of detection limits, reduction of high matrix activity and fission interferences if any. The current status and the applications of ENAA to environmental samples are reviewed. Experience in the use of ENAA in the monitoring of atmospheric depositions by means of moss-biomonitors at pulsed fast reactor IBR-2 in Dubna is summarized. INAA has shown to be useful for a number of sample types of interest in environmental studies, and should find more extensive use in this area. Analysis of airborne particulate matter is a case where ENAA should be particularly useful. A similar case where ENAA has shown strong performance is in the analysis of mosses used as biomonitors of atmospheric deposition, where 45 elements were determined. In this and other cases, however, induction-coupled plasma mass spectrometry is a very strong competitor, offering data for even more elements. A comparison of ENAA and ICP-MS for moss analysis is presented, and cases where ENAA is unique are discussed

  7. Uranium in coral skeletons determined by epithermal neutron activation analysis

    International Nuclear Information System (INIS)

    Ohde, S.; Hossain, M.M.M.; Ozaki, H.; Masuzawa, T.

    2003-01-01

    A simple and non-destructive method has been proposed for the routine determination of uranium by epithermal neutron activation analysis in coral skeletons. Using a cadmium capsule, about 0.1-0.2 g samples were irradiated for 6 hours in the Triga Mark II Reactor. Measurements of γ-ray ( 239 Np via 239 U) were performed with each sample and standard after cooling for about three days. Compared with a non-destructive thermal NAA, the present method was found to improve the sensitivity because it reduced the intense Compton background induced by 24 Na. Uranium in coral standards was determined within 2% of analytical precision. The data obtained for the carbonate standards are mostly consistent with reported values. The present method could be usefully applied to determine uranium contents in fossil corals from the Funafuti Atoll in the Pacific. The distribution of uranium between seawater and coral skeletons is also discussed in order to understand the environmental media in which the coral grew. (author)

  8. The resonant detector and its application to epithermal neutron spectroscopy

    International Nuclear Information System (INIS)

    Gorini, G.; Perelli-Cippo, E.; Tardocchi, M.; Andreani, C.; D'Angelo, A.; Pietropaolo, A.; Senesi, R.; Imberti, S.; Bracco, A.; Previtali, E.; Pessina, G.; Rhodes, N.J.; Schooneveld, E.M.

    2004-01-01

    New perspectives for epithermal neutron spectroscopy are being opened by the development of the resonant detector (RD) and its use on inverse geometry time of flight spectrometers at spallation sources. The RD was first proposed in the 1980s and was recently brought to a performance level exceeding conventional neutron-sensitive Li-glass scintillator detectors. It features a photon counter coupled to a neutron analyzer foil. Resonant neutron absorption in the foil results in the emission of prompt gamma rays that are detected in the photon counter. The dimensions of the RD set the spatial resolution that can be achieved, ranging from a fraction of a cm to several cm. It can thus be tailored to the construction of detector arrays of different geometry. The main results of the research on this kind of detector are reported leading to the present optimized RD design based on a combination of YAP scintillation photon counter and uranium or gold analyzer foils. This detector has already been selected for application in the upgrade of the VESUVIO spectrometer on ISIS. A special application is the Very Low Angle Detector (VLAD) bank, which will extend the kinematical region for neutron scattering to low momentum transfer ( -1 ) whilst still keeping energy transfer >1 eV, thus allowing new experimental studies in condensed matter systems. The first results of tests made with prototype VLAD detectors are presented, confirming the usefulness of the RD for measurements at scattering angles as low as 2-5 deg

  9. Method and apparatus for epithermal neutron decay logging

    International Nuclear Information System (INIS)

    Nelligan, W.B.

    1998-01-01

    The nature of hydrogenous fluids filling the pore spaces in formations surrounding a well bore are determined by irradiating the formations with bursts of high energy neutrons and using the ratio of time-dependent parameters related to the decay of epithermal neutron populations above two different energy levels to provide values indicative of the kind of fluid present, independent of porosity. The measurement above the higher of these energy levels, appr. 0.4eV, indicates the existence of hydrogenous fluid, water and hydrocarbons in the formations. The lower threshold measurement, above appr. 0.15eV, is indicative of the structure of the molecule in which the hydrogen molecule is bound and of the porosity. A pulsed neutron generator in a sonde irradiates the formations with 14meV neutrons and a pair of detectors, one shielded by cadmium, to establish the 0.4eV threshold energy level and the other, shielded by gadolinium, to establish the 0.15eV threshold energy level. Time related parameters of the count rate information, e.g. the decay constants, provided by each detector are derived. The ratio of the respective parameters is used to identify the type of fluid in the information, independent of porosity. The method and apparatus can determine water saturation, i.e. percentage of water in the formation fluid and can identify specific types of hydrocarbons under 100% hydrocarbon saturation conditions. 8 figs

  10. Epithermal Neutron Activation Analysis of the Asian Herbal Plants

    International Nuclear Information System (INIS)

    Baljinnyam, N.; Frontasyeva, M. V.; Ostrovnaya, T. M.; Pavlov, S. S.; Jugder, B.; Norov, N.

    2011-01-01

    Asian medicinal herbs Chrysanthemum (Spiraea aquilegifolia Pall.) and Red Sandalwood (Pterocarpus Santalinus) are widely used in folk and Ayurvedic medicine for healing and preventing some diseases. The modern medical science has proved that the Chrysanthemum (Spiraea aquilegifolia Pall.) possesses the following functions: reducing blood press, dispelling cancer cell, coronary artery's expanding and bacteriostating and Red Sandalwood (Pterocarpus Santalinus) is recommended against headache, toothache, skin diseases, vomiting and sometimes it is taken for treatment of diabetes. Species of Chrysanthemums were collected in the north-eastern and central Mongolia, and the Red Sandalwood powder was imported from India. Samples of Chrysanthemums (branches, flowers and leaves)(0.5 g) and red sandalwood powder (0.5 g) were subjected to the multi-element instrumental neutron activation analysis using epithermal neutrons (ENAA) at the IBR-2 reactor, Frank Laboratory of Neutron Physics (FLNP) JINR, Dubna. A total of 41 elements (Na, Mg, Al, Cl, K, Ca, Sc, V, Cr, Mn, Fe, Co, Ni, Zn, As, Se, Br, Rb, Sr, Zr, Mo, Cd, Cs, Ba, La, Hf, Ta, W, Sb, Au, Hg, Ce, Nd, Sm, Eu, Tb, Dy, Yb, Th, U, Lu) were determined. For the first time such a large group of elements was determined in the herbal plants used in Mongolia. The quality control of the analytical results was provided by using certified reference material Bowen Cabbage. The results obtained are compared to the ''Reference plant? data (B. Markert, 1992) and interpreted in terms of excess of such elements as Se, Cr, Ca, Fe, Ni, Mo, and rare earth elements.

  11. Experiences of reconstruction of the epithermal neutron beam at THOR

    International Nuclear Information System (INIS)

    Liu Hongming; Hsu Pinchieh; Liu Chaochin; Jiang Shianghuei; Liu Yenwan Hsueh; Kai Jijung

    2006-01-01

    Tsing Hua Open-pool Reactor (THOR) had completed the renovation for an epithermal neutron beam in August 2004. The major tasks for this renovation were moderator/filter design and assembling, and concrete cutting for a better beam quality and larger irradiation room. Besides moderator/filter design, the associated works involved radiation monitoring, structure analysis, and shielding design. The radiation monitoring was performed to predict the probable accumulated dose for the workers involved in this reconstruction project. Special shielding design and construction processes were adopted to lower the radiation level and the probable accumulated dose for the workers. Before concrete cutting, structure analysis based on SAP-2000 code was performed to assure the structure is safe from the earthquake in Taiwan. A wall saw was then used for concrete cutting to enlarge the space of the irradiation room. Moderator/filter components were assembled on a trolley outside the beam exit prior to installation, which can effectively reduce the duration of a worker staying inside the reconstruction area and thereby reduce the accumulated dose. The shielding for the irradiation room was designed based on MCNP simulation using a pre-calculated source plane at the beam exit. The thickness of the concrete (density=3 g/cm 3 ) of the walls and ceiling of the irradiation room were designed to be 100cm. On-going tasks include beam parameters measurement and in vitro/ in vivo study and calibration of treatment planning system, with the hope that the team can be ready for clinical trials in 2-3 years. (author)

  12. Epithermal neutron beam adoption for lung and pancreatic cancer treatment by boron neutron capture therapy

    International Nuclear Information System (INIS)

    Matsumoto, Tetsuo; Fukushima, Yuji

    2001-01-01

    The depth-dose distributions were evaluated for possible treatment of both lung and pancreatic cancers using an epithermal neutron beam. The Monte Carlo Neutron Photon (MCNP) calculations showed that physical dose in tumors were 6 and 7 Gy/h, respectively, for lung and pancreas, attaining an epithermal neutron flux of 5 x 10 8 ncm -2 s -1 . The boron concentrations were assumed at 100 ppm and 30 ppm, respectively, for lung and pancreas tumors and normal tissues contains 1/10 tumor concentrations. The dose ratios of tumor to normal tissue were 2.5 and 2.4, respectively, for lung and pancreas. The dose evaluation suggests that BNCT using an epithermal neutron beam could be applied for both lung and pancreatic cancer treatment. (author)

  13. Earth formation pulsed neutron porosity logging system utilizing epithermal neutron and inelastic scattering gamma ray detectors

    International Nuclear Information System (INIS)

    Smith, H.D. Jr.; Smith, M.P.; Schultz, W.E.

    1978-01-01

    An improved pulsed neutron porosity logging system is provided in the present invention. A logging tool provided with a 14 MeV pulsed neutron source, an epithermal neutron detector and an inelastic scattering gamma ray detector is moved through a borehole. The detection of inelastic gamma rays provides a measure of the fast neutron population in the vicinity of the detector. repetitive bursts of neutrons irradiate the earth formation and, during the busts, inelastic gamma rays representative of the fast neutron population is sampled. During the interval between bursts the epithermal neutron population is sampled along with background gamma radiation due to lingering thermal neutrons. the fast and epithermal neutron population measurements are combined to provide a measurement of formation porosity

  14. TRANSHEX, 2-D Thermal Neutron Flux Distribution from Epithermal Flux in Hexagonal Geometry

    International Nuclear Information System (INIS)

    Patrakka, E.

    1994-01-01

    1 - Description of program or function: TRANSHEX is a multigroup integral transport program that determines the thermal scalar flux distribution arising from a known epithermal flux in two- dimensional hexagonal geometry. 2 - Method of solution: The program solves the isotropic collision probability equations for a region-averaged scalar flux by an iterative method. Either a successive over-relaxation or an inner-outer iteration technique is applied. Flat flux collision probabilities between trigonal space regions with white boundary condition are utilized. The effect of epithermal flux is taken into consideration as a slowing-down source that is calculated for a given spatial distribution and 1/E energy dependence of the epithermal flux

  15. Experimental demonstration of a compact epithermal neutron source based on a high power laser

    Science.gov (United States)

    Mirfayzi, S. R.; Alejo, A.; Ahmed, H.; Raspino, D.; Ansell, S.; Wilson, L. A.; Armstrong, C.; Butler, N. M. H.; Clarke, R. J.; Higginson, A.; Kelleher, J.; Murphy, C. D.; Notley, M.; Rusby, D. R.; Schooneveld, E.; Borghesi, M.; McKenna, P.; Rhodes, N. J.; Neely, D.; Brenner, C. M.; Kar, S.

    2017-07-01

    Epithermal neutrons from pulsed-spallation sources have revolutionised neutron science allowing scientists to acquire new insight into the structure and properties of matter. Here, we demonstrate that laser driven fast (˜MeV) neutrons can be efficiently moderated to epithermal energies with intrinsically short burst durations. In a proof-of-principle experiment using a 100 TW laser, a significant epithermal neutron flux of the order of 105 n/sr/pulse in the energy range of 0.5-300 eV was measured, produced by a compact moderator deployed downstream of the laser-driven fast neutron source. The moderator used in the campaign was specifically designed, by the help of MCNPX simulations, for an efficient and directional moderation of the fast neutron spectrum produced by a laser driven source.

  16. Geochemical and modal data for igneous rocks associated with epithermal mineral deposits

    Science.gov (United States)

    du Bray, Edward A.

    2014-01-01

    The purposes of this report are to (1) present available geochemical and modal data for igneous rocks associated with epithermal mineral deposits and (2) to make those data widely and readily available for subsequent, more in-depth consideration and interpretation. Epithermal precious and base-metal deposits are commonly associated with subduction-related calc-alkaline to alkaline arc magmatism as well as back-arc continental rift magmatism. These deposits form in association with compositionally diverse extrusive and intrusive igneous rocks. Temperature and depth regimes prevailing during deposit formation are highly variable. The deposits form from hydrothermal fluids that range from acidic to near-neutral pH, and they occur in a variety of structural settings. The disparate temperature, pressure, fluid chemistry, and structural controls have resulted in deposits with wide ranging characteristics. Economic geologists have employed these characteristics to develop classification schemes for epithermal deposits and to constrain the important genetic processes responsible for their formation.

  17. A preliminary investigation on the epithermal flux depression effect due to cadmium box in a multiplying medium

    International Nuclear Information System (INIS)

    Ahmad, A.

    1983-01-01

    Cadmium boxes are widely used as filter in Reactor Neutron Activation Analysis (RNAA) for the irradiation of samples in epithermal neutrons. By virtue of being an absorber the cadmium boxes produce epithermal flux depression in the medium surrounding them. A preliminary study of this effect was carried out (author)

  18. Epithermal beam development at the BMRR [Brookhaven Medical Research Reactor]: Dosimetric evaluation

    International Nuclear Information System (INIS)

    Saraf, S.K.; Fairchild, R.G.; Kalef-Ezra, J.; Laster, B.H.; Fiarman, S.; Ramsey, E.; Ioannina Univ.; Brookhaven National Lab., Upton, NY; State Univ. of New York, Stony Brook, NY

    1989-01-01

    The utilization of an epithermal neutron beam for neutron capture therapy (NCT) is desirable because of the increased tissue penetration relative to a thermal neutron beam. Over the past few years, modifications have been and continue to be made at the Brookhaven Medical Research Reactor (BMRR) by changing its filter components to produce an optimal epithermal beam. An optimal epithermal beam should contain a low fast neutron contamination and no thermal neutrons in the incident beam. Recently a new moderator for the epithermal beam has been installed at the epithermal port of the BMRR and has accomplished this task. This new moderator is a combination of alumina (Al 2 O 3 ) bricks and aluminum (Al) plates. A 0.51 mm thick cadmium (Cd) sheet has reduced the thermal neutron intensity drastically. Furthermore, an 11.5 cm thick bismuth (Bi) plate installed at the port surface has reduced the gamma dose component to negligible levels. Foil activation techniques have been employed by using bare gold and cadmium-covered gold foil to determine thermal as well as epithermal neutron fluence. Fast neutron fluence has been determined by indium foil counting. Fast neutron and gamma dose in soft tissue, free in air, is being determined by the paired ionization chamber technique, using tissue equivalent (TE) and graphite chambers. Thermoluminescent dosimeters (TLD-700) have also been used to determine the gamma dose independently. This paper describes the methods involved in the measurements of the above mentioned parameters. Formulations have been developed and the various corrections involved have been detailed. 12 refs

  19. Isotopic tracers of gold deposition in paleozoic limestones, southern Nevada

    International Nuclear Information System (INIS)

    Peterman, Z.E.; Widmann, B.L.; Marshall, B.D.; Aleinikoff, J.N.; Futa, K.; Mahan, S.A.

    1994-01-01

    Strontium isotopic analyses of barren and mineralized Paleozoic carbonate rocks show that hydrothermal fluids added radiogenic strontium ( 87 Sr) to the mineralized zones. At Bare Mountain, samples collected from mineralized areas have δ 87 Sr t values (per mil deviation from primary marine values) ranging from +3.0 to +23.0 (mean of this log-normal distribution is +7.0), whereas unmineralized carbonate rocks have δ 87 Sr t values of -0.6 to +2.9 (mean of +1.07±1.03). In other ranges (Striped Hills, Spring Mountains, and ranges in the vicinity of Indian Springs Valley), δ 87 Sr t values of the unmineralized carbonate rocks are even lower and virtually indistinguishable from primary marine values. This correlation of elevated δ 87 Sr t values with mineralized zones provides a useful technique for assessing the mineral potential of the Paleozoic basement beneath Yucca Mountain, and may find broader use in mineral exploration in the Basin and Range province as a whole

  20. Late paleozoic fusulinoidean gigantism driven by atmospheric hyperoxia.

    Science.gov (United States)

    Payne, Jonathan L; Groves, John R; Jost, Adam B; Nguyen, Thienan; Moffitt, Sarah E; Hill, Tessa M; Skotheim, Jan M

    2012-09-01

    Atmospheric hyperoxia, with pO(2) in excess of 30%, has long been hypothesized to account for late Paleozoic (360-250 million years ago) gigantism in numerous higher taxa. However, this hypothesis has not been evaluated statistically because comprehensive size data have not been compiled previously at sufficient temporal resolution to permit quantitative analysis. In this study, we test the hyperoxia-gigantism hypothesis by examining the fossil record of fusulinoidean foraminifers, a dramatic example of protistan gigantism with some individuals exceeding 10 cm in length and exceeding their relatives by six orders of magnitude in biovolume. We assembled and examined comprehensive regional and global, species-level datasets containing 270 and 1823 species, respectively. A statistical model of size evolution forced by atmospheric pO(2) is conclusively favored over alternative models based on random walks or a constant tendency toward size increase. Moreover, the ratios of volume to surface area in the largest fusulinoideans are consistent in magnitude and trend with a mathematical model based on oxygen transport limitation. We further validate the hyperoxia-gigantism model through an examination of modern foraminiferal species living along a measured gradient in oxygen concentration. These findings provide the first quantitative confirmation of a direct connection between Paleozoic gigantism and atmospheric hyperoxia. © 2012 The Author(s). Evolution© 2012 The Society for the Study of Evolution.

  1. A new position-sensitive transmission detector for epithermal neutron imaging

    International Nuclear Information System (INIS)

    Schooneveld, E M; Kockelmann, W; Rhodes, N; Tardocchi, M; Gorini, G; Perelli Cippo, E; Nakamura, T; Postma, H; Schillebeeckx, P

    2009-01-01

    A new neutron resonant transmission (NRT) detector for epithermal neutron imaging has been designed and built for the ANCIENT CHARM project, which is developing a set of complementary neutron imaging methods for analysis of cultural heritage objects. One of the techniques being exploited is NRT with the aim of performing bulk elemental analysis. The 16-pixel prototype NRT detector consists of independent crystals of 2 x 2 mm pixel size, which allow for 2D position-sensitive transmission measurements with epithermal neutrons. First results obtained at the ISIS pulsed spallation neutron source are presented. (fast track communication)

  2. Determination of silicon in biological and botanical reference materials by epithermal INAA and Compton suppression

    International Nuclear Information System (INIS)

    Landsberger, S.; Peshev, S.; Becker, D.A.

    1994-01-01

    Silicon determination in sixteen botanical and biological standard reference materials is described using the 29 Si(n, p) 29 Al reaction through instrumental epithermal neutron activation analysis and Compton suppression gamma-ray spectroscopy. By simultaneous utilization of both cadmium and boron epithermal filters along with anticoincidence gamma-counting, detection limits as low as 12 ppm were obtained for certain matrices, much lower than previously reported values for this type of analysis. The method is applicable to many botanical and biological matrices and is attractive with its interference free, purely instrumental nature, compared with methods using the 28 Si(n, p) 28 Al reaction or chemical separation techniques. ((orig.))

  3. Hydrologic models of modern and fossil geothermal systems in the Great Basin: Genetic implications for epithermal Au-Ag and Carlin-type gold deposits

    Science.gov (United States)

    Person, M.; Banerjee, A.; Hofstra, A.; Sweetkind, D.; Gao, Y.

    2008-01-01

    The Great Basin region in the western United States contains active geothermal systems, large epithermal Au-Ag deposits, and world-class Carlin-type gold deposits. Temperature profiles, fluid inclusion studies, and isotopic evidence suggest that modern and fossil hydrothermal systems associated with gold mineralization share many common features, including the absence of a clear magmatic fluid source, discharge areas restricted to fault zones, and remarkably high temperatures (>200 ??C) at shallow depths (200-1500 m). While the plumbing of these systems varies, geochemical and isotopic data collected at the Dixie Valley and Beowawe geothermal systems suggest that fluid circulation along fault zones was relatively deep (>5 km) and comprised of relatively unexchanged Pleistocene meteoric water with small (horizons. Those with minimal fluid ?? 18O shifts are restricted to high-permeability fault zones and relatively small-scale (???5 km), single-pass flow systems (e.g., Beowawe). Those with intermediate to large isotopic shifts (e.g., epithermal and Carlin-type Au) had larger-scale (???15 km) loop convection cells with a greater component of flow through marine sedimentary rocks at lower water/rock ratios and greater endowments of gold. Enthalpy calculations constrain the duration of Carlin-type gold systems to probably account for the amount of silica in the sinter deposits. In the Carlin trend, fluid circulation extended down into Paleozoic siliciclastic rocks, which afforded more mixing with isotopically enriched higher enthalpy fluids. Computed fission track ages along the Carlin trend included the convective effects, and ranged between 91.6 and 35.3 Ma. Older fission track ages occurred in zones of groundwater recharge, and the younger ages occurred in discharge areas. This is largely consistent with fission track ages reported in recent studies. We found that either an amagmatic system with more permeable faults (10-11 m2) or a magmatic system with less

  4. Paleozoic subduction complex and Paleozoic-Mesozoic island-arc volcano-plutonic assemblages in the northern Sierra terrane

    Science.gov (United States)

    Hanson, Richard E.; Girty, Gary H.; Harwood, David S.; Schweickert, Richard A.

    2000-01-01

    This field trip provides an overview of the stratigraphic and structural evolution of the northern Sierra terrane, which forms a significant part of the wall rocks on the western side of the later Mesozoic Sierra Nevada batholith in California. The terrane consists of a pre-Late Devonian subduction complex (Shoo Fly Complex) overlain by submarine arc-related deposits that record the evolution of three separate island-arc systems in the Late Sevonian-Early Mississippian, Permian, and Late Triassic-Jurassic. The two Paleozoic are packages and the underlying Shoo Fly Complex have an important bearing on plate-tectonic processes affecting the convergent margin outboard of the Paleozoic Cordilleran miogeocline, although their original paleogeographic relations to North America are controversial. The third arc package represents an overlap assemblage that ties the terrane to North America by the Late Triassic and helps constrain the nature and timing of Mesozoic orogenesis. Several of the field-trip stops examine the record of pre-Late Devonian subduction contained in the Shoo Fly Complex, as well as the paleovolcanology of the overlying Devonian to Jurassic arc rocks. Excellent glaciated exposures provide the opportunity to study a cross section through a tilted Devonian volcano-plutonic association. Additional stops focus on plutonic rocks emplaced during the Middle Jurassic arc magmatism in the terrane, and during the main pulse of Cretaceous magmatism in the Sierra Nevada batholith to the east.

  5. Procedure and code for calculating black control rods taking into account epithermal absorption, code CAS-1

    International Nuclear Information System (INIS)

    Martinc, R.; Trivunac, N.; Zivkovic, Z.

    1964-12-01

    This report describes the computer code CAS-1, calculation method and procedure applied for calculating the black control rods taking into account the epithermal neutron absorption. Results obtained for supercell method applied for regular lattice reflected in the multiplication medium is part of this report in addition to the computer code manual

  6. Global plate boundary evolution and kinematics since the late Paleozoic

    Science.gov (United States)

    Matthews, Kara J.; Maloney, Kayla T.; Zahirovic, Sabin; Williams, Simon E.; Seton, Maria; Müller, R. Dietmar

    2016-11-01

    Many aspects of deep-time Earth System models, including mantle convection, paleoclimatology, paleobiogeography and the deep Earth carbon cycle, require high-resolution plate motion models that include the evolution of the mosaic of plate boundaries through time. We present the first continuous late Paleozoic to present-day global plate model with evolving plate boundaries, building on and extending two previously published models for the late Paleozoic (410-250 Ma) and Mesozoic-Cenozoic (230-0 Ma). We ensure continuity during the 250-230 Ma transition period between the two models, update the absolute reference frame of the Mesozoic-Cenozoic model and add a new Paleozoic reconstruction for the Baltica-derived Alexander Terrane, now accreted to western North America. This 410-0 Ma open access model provides a framework for deep-time whole Earth modelling and acts as a base for future extensions and refinement. We analyse the model in terms of the number of plates, predicted plate size distribution, plate and continental root mean square (RMS) speeds, plate velocities and trench migration through time. Overall model trends share many similarities to those for recent times, which we use as a first order benchmark against which to compare the model and identify targets for future model refinement. Except for during the period 260-160 Ma, the number of plates (16-46) and ratio of "large" plates (≥ 107.5 km2) to smaller plates ( 2.7-6.6) are fairly similar to present-day values (46 and 6.6, respectively), with lower values occurring during late Paleozoic assembly and growth of Pangea. This temporal pattern may also reflect difficulties in reconstructing small, now subducted oceanic plates further back in time, as well as whether a supercontinent is assembling or breaking up. During the 260-160 Ma timeframe the model reaches a minima in the number of plates, in contrast to what we would expect during initial Pangea breakup and thus highlighting the need for refinement

  7. Characteristics of core sampling from crumbing Paleozoic rock

    Energy Technology Data Exchange (ETDEWEB)

    Barabashkin, I I; Edelman, Y A; Filippov, V N; Lychev, V N

    1981-01-01

    The results of analysis of core sampling using standard core sampling tools with small and medium inside diameter are cited. It is demonstrated that when using these tools loss of core in Paleozoic deposits promising with regard to oil and gas content does not exceed 25 - 30%. The use of a new core sampling tool with a large inside diameter which includes drill bits of different types and a core lifter ''Krembriy'' SKU-172/100 made it possible to increase core removal approximately 52%. A representative core from a highly crumbling and vesicular rock belinging to groups III - IV in terms of difficulty of core sampling was obtained first. A description of a new core sampling tool is given. The characteristics of the technology of its use which promote preservation of the core are cited. Means of continued improvement of this tool are noted.

  8. Pacing of Paleozoic macroevolutionary rates by Milankovitch grand cycles.

    Science.gov (United States)

    Crampton, James S; Meyers, Stephen R; Cooper, Roger A; Sadler, Peter M; Foote, Michael; Harte, David

    2018-05-29

    Periodic fluctuations in past biodiversity, speciation, and extinction have been proposed, with extremely long periods ranging from 26 to 62 million years, although forcing mechanisms remain speculative. In contrast, well-understood periodic Milankovitch climate forcing represents a viable driver for macroevolutionary fluctuations, although little evidence for such fluctuation exists except during the Late Cenozoic. The reality, magnitude, and drivers of periodic fluctuations in macroevolutionary rates are of interest given long-standing debate surrounding the relative roles of intrinsic biotic interactions vs. extrinsic environmental factors as drivers of biodiversity change. Here, we show that, over a time span of 60 million years, between 9 and 16% of the variance in biological turnover (i.e., speciation probability plus species extinction probability) in a major Early Paleozoic zooplankton group, the graptoloids, can be explained by long-period astronomical cycles (Milankovitch "grand cycles") associated with Earth's orbital eccentricity (2.6 million years) and obliquity (1.3 million years). These grand cycles modulate climate variability, alternating times of relative stability in the environment with times of maximum volatility. We infer that these cycles influenced graptolite speciation and extinction through climate-driven changes to oceanic circulation and structure. Our results confirm the existence of Milankovitch grand cycles in the Early Paleozoic Era and show that known processes related to the mechanics of the Solar System were shaping marine macroevolutionary rates comparatively early in the history of complex life. We present an application of hidden Markov models to macroevolutionary time series and protocols for the evaluation of statistical significance in spectral analysis.

  9. Measurement of thermal, epithermal and fast neutrons fluxes by the activation foil method at IEA-R1 reactor

    International Nuclear Information System (INIS)

    Dias, M.S.; Koskinas, M.F.; Berretta, J.R.; Fratin, L.; Botelho, S.

    1990-01-01

    The thermal, epithermal and fast neutron fluxes have been determined experimentally by the activation foil method at position GI, located near the IEA-R1 reactor core. The reactions used were 197 Au (n,gamma) 198 Au, for thermal and epithermal neutrons and 27 Na (n,alpha) 24 Na, for fast neutrons. The activities were measured by the 4π(PC)β-γ coincidence method. (author)

  10. Paleozoic unconformities favorable for uranium concentration in northern Appalachian basin

    International Nuclear Information System (INIS)

    Dennison, J.M.

    1986-01-01

    Unconformities can redistribute uranium from protore rock as ground water moves through poorly consolidated strata beneath the erosion surface, or later moves along the unconformity. Groundwater could migrate farther than in present-day lithified Paleozoic strata in the Appalachian basin, now locally deformed by the Taconic and Allegheny orogenies. Several paleoaquifer systems could have developed uranium geochemical cells. Sandstone mineralogy, occurrences of fluvial strata, and reduzate facies are important factors. Other possibilities include silcrete developed during desert exposure, and uranium concentrated in paleokarst. Thirteen unconformities are evaluated to determine favorable areas for uranium concentration. Cambrian Potsdam sandstone (New York) contains arkoses and possible silcretes just above crystalline basement. Unconformities involving beveled sandstones and possible fluvial strata include Cambrian Hardyston sandstone (New Jersey), Cambrian Potsdam Sandstone (New York), Ordovician Oswego and Juniata formations (Pennsylvania and New York), Silurian Medina Group (New York), and Silurian Vernon, High Falls, and Longwood formations (New York and New Jersey). Devonian Catskill Formation is beveled by Pennsylvanian strata (New York and Pennsylvania). The pre-Pennsylvanian unconformity also bevels Lower Mississippian Pocono, Knapp, and Waverly strata (Pennsylvania, New York, and Ohio), truncates Upper Mississippian Mauch Chunk Formation (Pennsylvania), and forms paleokarst on Mississippian Loyalhanna Limestone (Pennsylvania) and Maxville Limestone (Ohio). Strata associated with these unconformities contain several reports of uranium. Unconformities unfavorable for uranium concentration occur beneath the Middle Ordovician (New York), Middle Devonian (Ohio and New York), and Upper Devonian (Ohio and New York); these involve marine strata overlying marine strata and probably much submarine erosion

  11. Testing the impact of miniaturization on phylogeny: Paleozoic dissorophoid amphibians.

    Science.gov (United States)

    Fröbisch, Nadia B; Schoch, Rainer R

    2009-06-01

    Among the diverse clade of Paleozoic dissorophoid amphibians, the small, terrestrial amphibamids and the neotenic branchiosaurids have frequently been suggested as possible antecedents of either all or some of the modern amphibian clades. Classically, amphibamids and branchiosaurids have been considered to represent distinct, but closely related clades within dissorophoids, but despite their importance for the controversial lissamphibian origins, a comprehensive phylogenetic analysis of small dissorophoids has thus far not been attempted. On the basis of an integrated data set, the relationships of amphibamids and branchiosaurids were analyzed using parsimony and Bayesian approaches. Both groups represent miniaturized forms and it was tested whether similar developmental pathways, associated with miniaturization, lead to an artificial close relationship of branchiosaurids and amphibamids. Moreover, the fit of the resulting tree topologies to the distribution of fossil taxa in the stratigraphic rock record was assessed as an additional source of information. The results show that characters associated with a miniaturized morphology are not responsible for the close clustering of branchiosaurids and amphibamids. Instead, all analyses invariably demonstrate a monophyletic clade of branchiosaurids highly nested within derived amphibamids, indicating that branchiosaurids represent a group of secondarily neotenic amphibamid dissorophoids. This understanding of the phylogenetic relationships of small dissorophoid amphibians provides a new framework for the discussion of their evolutionary history and the evolution of characters shared by branchiosaurids and/or amphibamids with modern amphibian taxa.

  12. Thermal, epithermal and thermalized neutron attenuation properties of ilmenite-serpentine heat resistant concrete shield

    International Nuclear Information System (INIS)

    Kany, A.M.I.; El-Gohary, M.I.; Kamal, S.M.

    1994-01-01

    Experimental measurements were carried out to study the attenuation properties of low-energy neutrons transmitted through unheated and preheated barriers of heavy-weight, highly hydrated and heat-resistant concrete shields. The concrete shields under investigation have been prepared from naturally occurring ilmenite and serpentine Egyptian ores. A collimated beam obtained from an Am-Be source was used as a source of neutrons, while the measurements of total thermal, epithermal, and thermalized neutron fluxes were performed using a BF-3 detector, multichannel analyzer and Cd filter. Results show that the ilmenite-serpentine concrete proved to be a better thermal, epithermal and thermalized neutron attenuator than the ordinary concrete especially at a high temperature of concrete exposure. (Author)

  13. Development of resonant detectors for epithermal neutron spectroscopy at pulsed neutron sources

    International Nuclear Information System (INIS)

    Tardocchi, M.; Pietropaolo, A.; Senesi, R.; Andreani, C.; Gorini, G.

    2004-01-01

    New perspectives for epithermal neutron spectroscopy are opened by the development of new detectors for inverse geometry time of flight spectrometers at pulsed neutron sources. One example is the Very Low Angle Detector (VLAD) bank planned to be delivered, within the next 4 years, within the eVERDI project, on the neutron spectrometer VESUVIO, at the ISIS pulsed neutron source (UK). VLAD will extend the (q,ω) kinematical region for neutron scattering to low wavefactor transfer (q -1 ) still keeping energy transfer >1 eV, thus allowing the investigations of new experimental studies in condensed matter systems. The technique being developed for detection of epithermal neutrons, within this low q and high-energy transfer region, is the Resonance Detection Technique. In this work, the state of the detector development will be presented with special focus on the results obtained with some prototype detectors, namely YAP scintillators and cadmium-zinc-telluride semiconductors

  14. Theoretical and experimental study of collectrons for epithermal neutron flux in reactors

    International Nuclear Information System (INIS)

    Agu, M.N.

    1986-01-01

    A theoretical study of nuclear reactions and electric charge displacements arising in sensitivity to thermal and epithermal neutrons in collectrons allowed a computer code conception. Collectrons in Rhodium, Silver, Cobalt, Hafnium, Erbium, Gadolinium and Holmium have been tested in different radiation fields given by neutron or gamma filters irradiated in different places of Melusine and Siloe reactors. Some emitters were covered with different steel, nickel or zircaloy thicknesses. Theoretical and experimental results are consistent; that validate the computer code and show possibilities and necessity of covering collectron emitters to reduce or cancel the gamma sensitivity and to improve response instantaneity. A selective measurement of epithermal neutron flux can by this way, made by associating two types of collectrons [fr

  15. Detector for imaging and dosimetry of laser-driven epithermal neutrons by alpha conversion

    Science.gov (United States)

    Mirfayzi, S. R.; Alejo, A.; Ahmed, H.; Wilson, L. A.; Ansell, S.; Armstrong, C.; Butler, N. M. H.; Clarke, R. J.; Higginson, A.; Notley, M.; Raspino, D.; Rusby, D. R.; Borghesi, M.; Rhodes, N. J.; McKenna, P.; Neely, D.; Brenner, C. M.; Kar, S.

    2016-10-01

    An epithermal neutron imager based on detecting alpha particles created via boron neutron capture mechanism is discussed. The diagnostic mainly consists of a mm thick Boron Nitride (BN) sheet (as an alpha converter) in contact with a non-borated cellulose nitride film (LR115 type-II) detector. While the BN absorbs the neutrons in the thermal and epithermal ranges, the fast neutrons register insignificantly on the detector due to their low neutron capture and recoil cross-sections. The use of solid-state nuclear track detectors (SSNTD), unlike image plates, micro-channel plates and scintillators, provide safeguard from the x-rays, gamma-rays and electrons. The diagnostic was tested on a proof-of-principle basis, in front of a laser driven source of moderated neutrons, which suggests the potential of using this diagnostic (BN+SSNTD) for dosimetry and imaging applications.

  16. A new position-sensitive detector for thermal and epithermal neutrons

    International Nuclear Information System (INIS)

    Jeavons, A.P.; Ford, N.L.; Lindberg, B.; Sachot, R.

    1977-01-01

    A new two-dimensional position-sensitive neutron detector is described. It is based on (n,γ) neutron resonance capture in a foil with subsequent detection of internal conversion electrons with a high-density proportional chamber. Large-area detectors with a 1 mm spatial resolution are feasible. A detection efficiency of 50% is possible for thermal neutrons using gadolinium-157 foil and for epithermal neutrons using hafnium-177. (Auth.)

  17. Optimization in Activation Analysis by Means of Epithermal Neutrons. Determination of Molybdenum in Steel

    Energy Technology Data Exchange (ETDEWEB)

    Brune, D; Jirlow, J

    1963-12-15

    Optimization in activation analysis by means of selective activation with epithermal neutrons is discussed. This method was applied to the determination of molybdenum in a steel alloy without recourse to radiochemical separations. The sensitivity for this determination is estimated to be 10 ppm. With the common form of activation by means of thermal neutrons, the sensitivity would be about one-tenth of this. The sensitivity estimations are based on evaluation of the photo peak ratios of Mo-99/Fe-59.

  18. Advances on detectors for low-angle scattering of epithermal neutrons

    International Nuclear Information System (INIS)

    Perelli Cippo, E; Gorini, G; Tardocchi, M; Andreani, C; Pietropaolo, A; Senesi, R; Rhodes, N J; Schoonveld, E M

    2008-01-01

    The Very Low Angle Detector (VLAD) installed at the ISIS spallation neutron source is a novel instrument for epithermal neutron scattering with a range of applications in solid state physics. VLAD extends the kinematical space of the VESUVIO spectrometer to low momentum transfers at neutron energies above 1 eV. Measurements at scattering angles as low as 1° have been made with limitations due to the achievable signal/background ratio. (technical design note)

  19. Installation and testing of an optimized epithermal neutron beam at the Brookhaven Medical Research Reactor (BMRR)

    Energy Technology Data Exchange (ETDEWEB)

    Fairchild, R.G.; Kalef-Ezra, J.; Saraf, S.K.; Fiarman, S.; Ramsey, E.; Wielopolski, L.; Laster, B.; Wheeler, F. (Brookhaven National Lab., Upton, NY (USA); Ioannina Univ. (Greece); Brookhaven National Lab., Upton, NY (USA); State Univ. of New York, Stony Brook, NY (USA). Health Science Center; Brookhaven National Lab., Upton, NY (USA); EG and G Idaho, Inc., Idaho Falls, ID (USA))

    1989-01-01

    Various calculations indicate that an optimized epithermal neutron beam can be produced by moderating fission neutrons either with a combination of Al and D{sub 2}O, or with Al{sub 2}O{sub 3}. We have designed, installed and tested an Al{sub 2}O{sub 3} moderated epithermal neutron beam at the Brookhaven Medical Research Reactor (BMRR). The epithermal neutron fluence rate of 1.8 {times} 10{sup 9} n/cm{sup 2}-sec produces a peak thermal neutron fluence rate of 1.9 to 2.8 {times} 10{sup 9} n/cm{sup 2}-sec in a tissue equivalent (TE) phantom head, depending on the configuration. Thus a single therapy treatment of 5 {times} 10{sup 12} n/cm{sup 2} can be delivered in 30--45 minutes. All irradiation times are given for a BMRR power of 3 MW, which is the highest power which can be delivered continuously. 18 refs., 8 figs., 4 tabs.

  20. Utilization of epithermal neutrons for the determination of molybdenum in the presence of uranium

    International Nuclear Information System (INIS)

    Oliveira Melo, M.A.M. de.

    1984-05-01

    Activation analysis by means of selective activation with epithermal neutrons is proposed for the determination of molybdenum in samples when uranium is present. Instrumental activation analysis with epithermal neutrons is advantageous for the determination of elements with large resonance integral, as compared to its thermal neutron activation cross section. The main reason for using this method is the serious interference caused by 99 Mo produced by fission of 235 U. This effect is strongly reduced by using the epicadmium irradiation technique. The filter efficiency has been investigated by irradiation experiments with bare and cadmium-covered samples. A solvent extraction process for uranium, before irradiation, is proposed to reduce sample background. The determination of Mo in leach samples is proposed in order to support the analytical needs of Figueira and Pocos de Caldas Mineral Prospection Programme of Departamento de Tecnologia Mineral from CDTN/NUCLEBRAS (MG,Brazil). The introduction of activation analysis with epithermal neutrons as a routine analytical tool in CDTN is our main goal. This method represents one more opportunity for exploring the analytical facilities available at TRIGA MARK I IPR-R1 nuclear reactor. (Author) [pt

  1. An accelerator-based epithermal photoneutron source for boron neutron capture therapy

    Energy Technology Data Exchange (ETDEWEB)

    Mitchell, Hannah E. [Georgia Inst. of Technology, Atlanta, GA (United States)

    1996-04-01

    Boron neutron capture therapy is an experimental binary cancer radiotherapy modality in which a boronated pharmaceutical that preferentially accumulates in malignant tissue is first administered, followed by exposing the tissue in the treatment volume to a thermal neutron field. Current usable beams are reactor-based but a viable alternative is the production of an epithermal neutron beam from an accelerator. Current literature cites various proposed accelerator-based designs, most of which are based on proton beams with beryllium or lithium targets. This dissertation examines the efficacy of a novel approach to BNCT treatments that incorporates an electron linear accelerator in the production of a photoneutron source. This source may help to resolve some of the present concerns associated with accelerator sources, including that of target cooling. The photoneutron production process is discussed as a possible alternate source of neutrons for eventual BNCT treatments for cancer. A conceptual design to produce epithermal photoneutrons by high photons (due to bremsstrahlung) impinging on deuterium targets is presented along with computational and experimental neutron production data. A clinically acceptable filtered epithermal neutron flux on the order of 107 neutrons per second per milliampere of electron current is shown to be obtainable. Additionally, the neutron beam is modified and characterized for BNCT applications by employing two unique moderating materials (an Al/AlF3 composite and a stacked Al/Teflon design) at various incident electron energies.

  2. Geology of epithermal silver-gold bulk-mining targets, bodie district, Mono County, California

    Science.gov (United States)

    Hollister, V.F.; Silberman, M.L.

    1995-01-01

    The Bodie mining district in Mono County, California, is zoned with a core polymetallic-quartz vein system and silver- and gold-bearing quartz-adularia veins north and south of the core. The veins formed as a result of repeated normal faulting during doming shortly after extrusion of felsic flows and tuffs, and the magmatic-hydrothermal event seems to span at least 2 Ma. Epithermal mineralization accompanied repeated movement of the normal faults, resulting in vein development in the planes of the faults. The veins occur in a very large area of argillic alteration. Individual mineralized structures commonly formed new fracture planes during separate fault movements, with resulting broad zones of veinlets growing in the walls of the major vein-faults. The veinlet swarms have been found to constitute a target estimated at 75,000,000 tons, averaging 0.037 ounce gold per ton. The target is amenable to bulkmining exploitation. The epithermal mineralogy is simple, with electrum being the most important precious metal mineral. The host veins are typical low-sulfide banded epithermal quartz and adularia structures that filled voids created by the faulting. Historical data show that beneficiation of the simple vein mineralogy is very efficient. ?? 1995 Oxford University Press.

  3. Magnetic, radiometric and gravity signatures of localities of epithermal gold deposits in Fiji

    International Nuclear Information System (INIS)

    Gunn, Peter J.; Mackey, Tim; Meixner, Tony J.

    1998-01-01

    Fiji contains several epithermal gold deposits and by studying the geophysical responses in the vicinity of these deposits it is possible to identify a set of geophysical characteristics which indicate localities where such deposits may be located. Epithermal gold deposits are formed above intrusive stocks resulting from subduction processes. The source intrusions for the deposits are normally covered by lavas and pyroclastic rocks and the irregular magnetic effects of these units obscure the magnetic effects of the intrusions. In Fiji however the source intrusions can be recognized as causing gravity highs and magnetic highs in upward continued magnetic data in which the magnetic effects of volcanic rocks are suppressed. Vents associated with the intrusions can be recognized as magnetic lows which sometimes contain a central high. Some vents and calderas can be recognized in digital elevation data. Increased potassium concentrations ca be interpreted to indicate potassium alteration associated with mineralizing processes. Fractures that may localize epithermal deposits can be recognized in the magnetic data and enhancements of the data such as produced by derivative operations. (author)

  4. An accelerator-based epithermal photoneutron source for boron neutron capture therapy

    International Nuclear Information System (INIS)

    Mitchell, H.E.

    1996-04-01

    Boron neutron capture therapy is an experimental binary cancer radiotherapy modality in which a boronated pharmaceutical that preferentially accumulates in malignant tissue is first administered, followed by exposing the tissue in the treatment volume to a thermal neutron field. Current usable beams are reactor-based but a viable alternative is the production of an epithermal neutron beam from an accelerator. Current literature cites various proposed accelerator-based designs, most of which are based on proton beams with beryllium or lithium targets. This dissertation examines the efficacy of a novel approach to BNCT treatments that incorporates an electron linear accelerator in the production of a photoneutron source. This source may help to resolve some of the present concerns associated with accelerator sources, including that of target cooling. The photoneutron production process is discussed as a possible alternate source of neutrons for eventual BNCT treatments for cancer. A conceptual design to produce epithermal photoneutrons by high photons (due to bremsstrahlung) impinging on deuterium targets is presented along with computational and experimental neutron production data. A clinically acceptable filtered epithermal neutron flux on the order of 10 7 neutrons per second per milliampere of electron current is shown to be obtainable. Additionally, the neutron beam is modified and characterized for BNCT applications by employing two unique moderating materials (an Al/AlF 3 composite and a stacked Al/Teflon design) at various incident electron energies

  5. Petrophysics and hydrocarbon potential of Paleozoic rocks in Kuwait

    Science.gov (United States)

    Abdullah, Fowzia; Shaaban, Fouad; Khalaf, Fikry; Bahaman, Fatma; Akbar, Bibi; Al-Khamiss, Awatif

    2017-10-01

    Well logs from nine deep exploratory and development wells in Kuwaiti oil fields have been used to study petrophysical characteristics and their effect on the reservoir quality of the subsurface Paleozoic Khuff and Unayzah formations. Petrophysical log data have been calibrated with core analysis available at some intervals. The study indicates a complex lithological facies of the Khuff Formation that is composed mainly of dolomite and anhydrite interbeds with dispersed argillaceous materials and few limestone intercalations. This facies greatly lowered the formation matrix porosity and permeability index. The porosity is fully saturated with water, which is reflected by the low resistivity logs responses, except at some intervals where few hydrocarbon shows are recorded. The impermeable anhydrites, massive (low-permeability) carbonate rock and shale at the lower part of the formation combine to form intraformational seals for the clastic reservoirs of the underlying Unayzah Formation. By contrast, the log interpretation revealed clastic lithological nature of the Unayzah Formation with cycles of conglomerate, sandstone, siltstone, mudstone and shales. The recorded argillaceous materials are mainly of disseminated habit, which control, for some extent, the matrix porosity, that ranges from 2% to 15% with water saturation ranges from 65% to 100%. Cementation, dissolution, compaction and clay mineral authigenesis are the most significant diagenetic processes affecting the reservoir quality. Calibration with the available core analysis at some intervals of the formation indicates that the siliciclastic sequence is a fluvial with more than one climatic cycle changes from humid, semi-arid to arid condition and displays the impact of both physical and chemical diagenesis. In general, the study revealed that the Unyazah Formation has a better reservoir quality than the Khuff Formation and possible gas bearing zones.

  6. Lower Paleozoic carbonate rocks of Baird Mountains Quadrangle, Alaska

    Energy Technology Data Exchange (ETDEWEB)

    Dumoulin, J.A.; Harris, A.G.

    1985-04-01

    Lower Paleozoic carbonate rocks in the Baird Mountains quadrangle form a relatively thin (about 550 m), chiefly shallow-water succession that has been imbricately thrust and metamorphosed to lower greenschist facies. Middle and Upper Cambrian rocks - the first reported from the western Brooks Range - occur in the northeastern quarter of the quadrangle, south of Angayukaqsraq (formerly Hub) Mountain. They consist of marble grading upward into thin-bedded marble/dolostone couplets and contain pelagiellid mollusks, acetretid brachiopods, and agnostid trilobites. Sedimentologic features and the Pelagiellas indicate a shallow-water depositional environment. Overlying these rocks are Lower and Middle Ordovician marble and phyllite containing graptolites and conodonts of midshelf to basinal aspect. Upper Ordovician rocks in this area are bioturbated to laminated dolostone containing warm, shallow-water conodonts. In the Omar and Squirrel Rivers areas to the west, the Lower Ordovician carbonate rocks show striking differences in lithofacies, biofacies, and thickness. Here they are mainly dolostone with locally well-developed fenestral fabric and evaporite molds, and bioturbated to laminated orange- and gray-weathering dolomitic marble. Upper Silurian dolostone, found near Angayukaqsraq Mountain and on the central Squirrel River, contains locally abundant corals and stronmatoporoids. Devonian carbonate rocks are widely distributed in the Baird Mountains quadrangle; at least two distinct sequences have been identified. In the Omar area, Lower and Middle Devonian dolostone and marble are locally cherty and rich in megafossils. In the north-central (Nakolik River) area, Middle and Upper Devonian marble is interlayered with planar to cross-laminated quartz-carbonate metasandstone and phyllite.

  7. Geologic setting and genesis of the Mule Canyon low-sulfidation epithermal gold-silver deposit, north-central Nevada

    Science.gov (United States)

    John, D.A.; Hofstra, A.H.; Fleck, R.J.; Brummer, J.E.; Saderholm, E.C.

    2003-01-01

    The Mule Canyon mine exploited shallow, low-sulfidation, epithermal Au-Ag deposits that lie near the west side of the Northern Nevada rift in northern Lander County, Nevada. Mule Canyon consists of six small deposits that contained premining reserves of about 8.2 Mt at an average grade of 3.81 g Au/tonne. It is an uncommon mafic end member of low-sulfidation Au-Ag deposits associated with tholeiitic bimodal basalt-rhyolite magmatism. The ore is hosted by a basalt-andesite eruptive center that formed between about 16.4 to 15.8 Ma during early mafic eruptions related to regionally extensive bimodal magmatism. Hydrothermal alteration and Au-Ag ores formed at about 15.6 Ma and were tightly controlled by north-northwest- to north-striking high-angle fault and breccia zones developed during rifting, emplacement of mafic dikes, and eruption of mafic lava flows. Hydrothermal alteration assemblages are zoned outward from fluid conduits in the sequence silica-adularia, adularia-smectite, smectite (intermediate argillic), and smectite-carbonate (propylitic). All alteration types contain abundant pyrite and/or marcasite ?? arsenopyrite. Field relations indicate that silica-adularia alteration is superimposed on argillic and propylitic alteration. Little or no steam-heated acid-sulfate alteration is present, probably the result of a near-surface water table during hydrothermal alteration and ore deposition. Two distinct ore types are present at Mule Canyon: early replacement and later open-space filling. Replacement ores consist of disseminated and vesicle-filling pyrite, marcasite, and arsenopyrite in argillically altered or weakly silicified rocks. Ore minerals consist of Au-bearing arsenopyrite and arsenian pyrite overgrowths on earlier-formed pyrite and marcasite. Open-space filling ores include narrow stockwork quartz-adularia veins, banded and crustiform opaline and chalcedonic silica-adularia veins, silica-adularia cemented breccias, and sparse carbonate-pyrite and

  8. Optimization study for an epithermal neutron beam for boron neutron capture therapy at the University of Virginia Research Reactor

    International Nuclear Information System (INIS)

    Burns, T.D. Jr.

    1995-05-01

    The non-surgical brain cancer treatment modality, Boron Neutron Capture Therapy (BNCT), requires the use of an epithermal neutron beam. This purpose of this thesis was to design an epithermal neutron beam at the University of Virginia Research Reactor (UVAR) suitable for BNCT applications. A suitable epithermal neutron beam for BNCT must have minimal fast neutron and gamma radiation contamination, and yet retain an appreciable intensity. The low power of the UVAR core makes reaching a balance between beam quality and intensity a very challenging design endeavor. The MCNP monte carlo neutron transport code was used to develop an equivalent core radiation source, and to perform the subsequent neutron transport calculations necessary for beam model analysis and development. The code accuracy was validated by benchmarking output against experimental criticality measurements. An epithermal beam was designed for the UVAR, with performance characteristics comparable to beams at facilities with cores of higher power. The epithermal neutron intensity of this beam is 2.2 x 10 8 n/cm 2 · s. The fast neutron and gamma radiation KERMA factors are 10 x 10 -11 cGy·cm 2 /n epi and 20 x 10 -11 cGy·cm 2 /n epi , respectively, and the current-to-flux ratio is 0.85. This thesis has shown that the UVAR has the capability to provide BNCT treatments, however the performance characteristics of the final beam of this study were limited by the low core power

  9. End Late Paleozoic tectonic stress field in the southern edge of Junggar Basin

    Directory of Open Access Journals (Sweden)

    Wei Ju

    2012-09-01

    Full Text Available This paper presents the end Late Paleozoic tectonic stress field in the southern edge of Junggar Basin by interpreting stress-response structures (dykes, folds, faults with slickenside and conjugate joints. The direction of the maximum principal stress axes is interpreted to be NW–SE (about 325°, and the accommodated motion among plates is assigned as the driving force of this tectonic stress field. The average value of the stress index R′ is about 2.09, which indicates a variation from strike-slip to compressive tectonic stress regime in the study area during the end Late Paleozoic period. The reconstruction of the tectonic field in the southern edge of Junggar Basin provides insights into the tectonic deformation processes around the southern Junggar Basin and contributes to the further understanding of basin evolution and tectonic settings during the culmination of the Paleozoic.

  10. Conceptual design of 30 MeV magnet system used for BNCT epithermal neutron source

    International Nuclear Information System (INIS)

    Slamet Santosa; Taufik

    2015-01-01

    Conceptual design of 30 MeV Magnet System Used for BNCT Epithermal Neutron Source has been done based on methods of empirical model of basic equation, experiences of 13 MeV cyclotron magnet design and personal communications. In the field of health, cyclotron can be used as an epithermal neutron source for Boron Neutron Capture Therapy (BNCT). The development of cyclotron producing epithermal neutrons for BNCT has been performed at Kyoto University, of which it produces a proton beam current of 1.1 mA with energy of 30 MeV. With some experiences on 13 MeV cyclotron magnet design, to support BNCT research and development we performed the design studies of 30 MeV cyclotron magnet system, which is one of the main components of the cyclotron for deflecting proton beam into circular trajectory and serves as beam focusing. Results of this study are expected to define the parameters of particular cyclotron magnet. The scope of this study includes the study of the parameters component of the 30 MeV cyclotron and magnet initial parameters. The empirical method of basic equation model is then corroborated by a simulation using Superfish software. Based on the results, a 30 MeV cyclotron magnet for BNCT neutron source enables to be realized with the parameters of B 0 = 1.06 T, frequency RF = 64.733938 ≈ 65 MHz, the external radius of 0.73 m, the radius of the polar = 0.85 m, BH = 1.95 T and a gap hill of 4 cm. Because proton beam current that be needed for BNCT application is very large, then in the calculation it is chosen a great focusing axial νz = 0.630361 which can generate B V = 0.44 T. (author)

  11. Dose planning with comparison to in vivo dosimetry for epithermal neutron irradiation of the dog brain

    International Nuclear Information System (INIS)

    Seppaelae, Tiina; Auterinen, Iiro; Aschan, Carita; Seren, Tom; Benczik, Judit; Snellman, Marjatta; Huiskamp, Rene; Ramadan, Usama Abo; Kankaanranta, Leena; Joensuu, Heikki; Savolainen, Sauli

    2002-01-01

    Boron neutron capture therapy (BNCT) is an experimental type of radiotherapy, presently being used to treat glioblastoma and melanoma. To improve patient safety and to determine the radiobiological characteristics of the epithermal neutron beam of Finnish BNCT facility (FiR 1) dose-response studies were carried on the brain of dogs before starting the clinical trials. A dose planning procedure was developed and uncertainties of the epithermal neutron-induced doses were estimated. The accuracy of the method of computing physical doses was assessed by comparing with in vivo dosimetry. Individual radiation dose plans were computed using magnetic resonance images of the heads of 15 Beagle dogs and the computational model of the FiR 1 epithermal neutron beam. For in vivo dosimetry, the thermal neutron fluences were measured using Mn activation foils and the gamma-ray doses with MCP-7s type thermoluminescent detectors placed both on the skin surface of the head and in the oral cavity. The degree of uncertainty of the reference doses at the thermal neutron maximum was estimated using a dose-planning program. The estimated uncertainty (±1 standard deviation) in the total physical reference dose was ±8.9%. The calculated and the measured dose values agreed within the uncertainties at the point of beam entry. The conclusion is that the dose delivery to the tissue can be verified in a practical and reliable fashion by placing an activation dosimeter and a TL detector at the beam entry point on the skin surface with homogeneous tissues below. However, the point doses cannot be calculated correctly in the inhomogeneous area near air cavities of the head model with this type of dose-planning program. This calls for attention in dose planning in human clinical trials in the corresponding areas

  12. Neutron kinetics in moderators and SNM detection through epithermal-neutron-induced fissions

    Energy Technology Data Exchange (ETDEWEB)

    Gozani, Tsahi, E-mail: tgmaven@gmail.com [1050 Harriet St., Palo Alto, CA 94301 (United States); King, Michael J. [Rapiscan Laboratories Inc., 520 Almanor Ave., Sunnyvale, CA 94085 (United States)

    2016-01-01

    Extension of the well-established Differential Die Away Analysis (DDAA) into a faster time domain, where more penetrating epithermal neutrons induce fissions, is proposed and demonstrated via simulations and experiments. In the proposed method the fissions stimulated by thermal, epithermal and even higher-energy neutrons are measured after injection of a narrow pulse of high-energy 14 MeV (d,T) or 2.5 MeV (d,D) source neutrons, appropriately moderated. The ability to measure these fissions stems from the inherent correlation of neutron energy and time (“E–T” correlation) during the process of slowing down of high-energy source neutrons in common moderating materials such as hydrogenous compounds (e.g., polyethylene), heavy water, beryllium and graphite. The kinetic behavior following injection of a delta-function-shaped pulse (in time) of 14 MeV neutrons into such moderators is studied employing MCNPX simulations and, when applicable, some simple “one-group” models. These calculations served as a guide for the design of a source moderator which was used in experiments. Qualitative relationships between slowing-down time after the pulse and the prevailing neutron energy are discussed. A laboratory system consisting of a 14 MeV neutron generator, a polyethylene-reflected Be moderator, a liquid scintillator with pulse-shape discrimination (PSD) and a two-parameter E–T data acquisition system was set up to measure prompt neutron and delayed gamma-ray fission signatures in a 19.5% enriched LEU sample. The measured time behavior of thermal and epithermal neutron fission signals agreed well with the detailed simulations. The laboratory system can readily be redesigned and deployed as a mobile inspection system for SNM in, e.g., cars and vans. A strong pulsed neutron generator with narrow pulse (<75 ns) at a reasonably high pulse frequency could make the high-energy neutron induced fission modality a realizable SNM detection technique.

  13. Epithermal neutron beam for BNCT research at the Washington State University TRIGA research reactor

    International Nuclear Information System (INIS)

    Nigg, D.W.; Venhuizen, J.R.; Wheeler, F.J.; Wemple, C.A.; Tripard, G.E.; Gavin, P.R.

    2000-01-01

    A new epithermal-neutron beam facility for BNCT (Boron Neutron Capture Therapy) research and boronated agent screening in animal models is in the final stages of construction at Washington State University (WSU). A key distinguishing feature of the design is the incorporation of a new, high-efficiency, neutron moderating and filtering material, Fluental, developed by the Technical Research Centre of Finland. An additional key feature is the provision for adjustable filter-moderator thickness to systematically explore the radiobiological consequences of increasing the fast-neutron contamination above the nominal value associated with the baseline system. (author)

  14. The determination of self-powered neutron detector sensitivity on thermal and epithermal neutron flux densities

    International Nuclear Information System (INIS)

    Erben, O.

    1980-01-01

    The coefficients of thermal and epithermal neutron flux density depression and self-shielding for the SPN detectors with vanadium, rhodium, silver and cobalt emitters are presented, (for cobalt SPN detectors the functions describing the absorbtion of neutrons along the emitter cross-section are also shown). Using these coefficients and previously published beta particle escape efficiencies, sensitivities are determined for the principal types of detectors produced by Les Cables de Lyon and SODERN companies. The experiments and their results verifying the validity of the theoretical work are described. (author)

  15. Characterization of the γ background in epithermal neutron scattering measurements at pulsed neutron sources

    International Nuclear Information System (INIS)

    Pietropaolo, A.; Tardocchi, M.; Schooneveld, E.M.; Senesi, R.

    2006-01-01

    This paper reports the characterization of the different components of the γ background in epithermal neutron scattering experiments at pulsed neutron sources. The measurements were performed on the VESUVIO spectrometer at ISIS spallation neutron source. These measurements, carried out with a high purity germanium detector, aim to provide detailed information for the investigation of the effect of the γ energy discrimination on the signal-to-background ratio. It is shown that the γ background is produced by different sources that can be identified with their relative time structure and relative weight

  16. Evidence for rapid epithermal mineralization and coeval bimodal volcanism, Bruner Au-Ag property, NV USA

    Science.gov (United States)

    Baldwin, Dylan

    The character of Au-Ag mineralization and volcanic/hydrothermal relationships at the underexplored Miocene-age Bruner low-sulfidation epithermal Au-Ag deposit are elucidated using field and laboratory studies. Bruner is located in central Nevada within the Great Basin extensional province, near several major volcanic trends (Western Andesite, Northern Nevada Rift) associated with world-class Miocene-age epithermal Au-Ag provinces. Despite its proximity to several >1 Moz Au deposits, and newly discovered high-grade drill intercepts (to 117 ppm Au/1.5m), there is no published research on the deposit, the style of mineralization has not been systematically characterized, and vectors to mineralization remain elusive. By investigating the nature of mineralization and time-space relationships between volcanic/hydrothermal activity, the deposit has been integrated into a regional framework, and exploration targeting improved. Mineralization occurs within narrow quartz + adularia +/- pyrite veins that manifest as sheeted/stockwork zones, vein swarms, and rare 0.3-2 m wide veins hosted by two generations of Miocene high-K, high-silica rhyolite flow dome complexes overlying an andesite flow unit. The most prominent structural controls on veining are N­striking faults and syn-mineral basalt/rhyolite dikes. Productive veins have robust boiling indicators (high adularia content, bladed quartz after calcite, recrystallized colloform quartz bands), lack rhythmic banding, and contain only 1-2 stages; these veins overprint, or occur separately from another population of barren to weakly mineralized rhythmically banded quartz-only veins. Ore minerals consist of coarse Au0.5Ag 0.5 electrum, fine Au0.7Ag0.3 electrum, acanthite, uytenbogaardtite (Ag3AuS2) and minor embolite Ag(Br,Cl). Now deeply oxidized, veins typically contain Bruner appears to belong to a small subset of mid-Miocene epithermal deposits in Nevada with low base metal contents and low to no Se, related to calc

  17. Metrology and quality of radiation therapy dosimetry of electron, photon and epithermal neutron beams

    Energy Technology Data Exchange (ETDEWEB)

    Kosunen, A

    1999-08-01

    In radiation therapy using electron and photon beams the dosimetry chain consists of several sequential phases starting by the realisation of the dose quantity in the Primary Standard Dosimetry Laboratory and ending to the calculation of the dose to a patient. A similar procedure can be described for the dosimetry of epithermal neutron beams in boron neutron capture therapy (BNCT). To achieve the required accuracy of the dose delivered to a patient the quality of all steps in the dosimetry procedure has to be considered. This work is focused on two items in the dosimetry chains: the determination of the dose in the reference conditions and the evaluation of the accuracy of dose calculation methods. The issues investigated and discussed in detail are: a)the calibration methods of plane parallel ionisation chambers used in electron beam dosimetry, (b) the specification of the critical dosimetric parameter i.e. the ratio of stopping powers for water to air, (S I ?){sup water} {sub air}, in photon beams, (c) the feasibility of the twin ionization chamber technique for dosimetry in epithermal neutron beams applied to BNCT and (d) the determination accuracy of the calculated dose distributions in phantoms in electron, photon, and epithermal neutron beams. The results demonstrate that up to a 3% improvement in the consistency of dose determinations in electron beams is achieved by the calibration of plane parallel ionisation chambers in high energy electron beams instead of calibrations in {sup 60}Co gamma beams. In photon beam dosimetry (S I ?){sup water} {sub air} can be determined with an accuracy of 0.2% using the percentage dose at the 10 cm depth, %dd(10), as a beam specifier. The use of %odd(10) requires the elimination of the electron contamination in the photon beam. By a twin ionisation chamber technique the gamma dose can be determined with uncertainty of 6% (1 standard deviation) and the total neutron dose with an uncertainty of 15 to 20% (1 standard deviation

  18. Metrology and quality of radiation therapy dosimetry of electron, photon and epithermal neutron beams

    International Nuclear Information System (INIS)

    Kosunen, A.

    1999-08-01

    In radiation therapy using electron and photon beams the dosimetry chain consists of several sequential phases starting by the realisation of the dose quantity in the Primary Standard Dosimetry Laboratory and ending to the calculation of the dose to a patient. A similar procedure can be described for the dosimetry of epithermal neutron beams in boron neutron capture therapy (BNCT). To achieve the required accuracy of the dose delivered to a patient the quality of all steps in the dosimetry procedure has to be considered. This work is focused on two items in the dosimetry chains: the determination of the dose in the reference conditions and the evaluation of the accuracy of dose calculation methods. The issues investigated and discussed in detail are: a)the calibration methods of plane parallel ionisation chambers used in electron beam dosimetry, (b) the specification of the critical dosimetric parameter i.e. the ratio of stopping powers for water to air, (S I ?) water air , in photon beams, (c) the feasibility of the twin ionization chamber technique for dosimetry in epithermal neutron beams applied to BNCT and (d) the determination accuracy of the calculated dose distributions in phantoms in electron, photon, and epithermal neutron beams. The results demonstrate that up to a 3% improvement in the consistency of dose determinations in electron beams is achieved by the calibration of plane parallel ionisation chambers in high energy electron beams instead of calibrations in 60 Co gamma beams. In photon beam dosimetry (S I ?) water air can be determined with an accuracy of 0.2% using the percentage dose at the 10 cm depth, %dd(10), as a beam specifier. The use of %odd(10) requires the elimination of the electron contamination in the photon beam. By a twin ionisation chamber technique the gamma dose can be determined with uncertainty of 6% (1 standard deviation) and the total neutron dose with an uncertainty of 15 to 20% (1 standard deviation). To improve the accuracy

  19. Epithermal neutron flux distribution and its impact on (n, γ) activation analysis result

    International Nuclear Information System (INIS)

    Jovanovich, S.; Pukotich, P.; Zejnilovich, R.; Corte, F. de; Moens, L.; Hoste, J.; Simonitis, A.

    1985-01-01

    The differences are discussed between the simplified model, introduced to derive the generally accepted ideal 1/E - law, and the conditions existing in an actual reactor. For absolute and comparator types of (n, γ) activation analysis (NAA), the semiempirical 1/Esup(1+α) form is a better approximation - necessary to introduce, but sufficient for practical purposes. Parameter α, being a measure of the epithermal nonideality, is a characteristics of the reactor site. The impact of this nonideality on NAA result is outlined, together with the method for appropriate correction

  20. Determination of selenium in Ni + Co concentrates applying epithermal neutron activation analysis

    International Nuclear Information System (INIS)

    Capote Rodriguez, G.; Perez Sayaz, G.; Hernandez Rivero, A.; Moreno Bermudez, J.; Ribeiro Guevara, S.; Arribere, M.A.; Molina Insfran, J.

    1996-01-01

    Concentration of Se in Ni + Co concentrates obtained in nickel industry has to be determined as that is a quality control requirement for its commercialization. At present, analysis of Se, specially at a minor and trace levels is relatively complicated and destructive procedures are frequently required. In this work determination of Se by epithermal neutron activation analysis (ENAA) in 17 samples of nickel industry was investigated. Application of ENAA allowed nondestructive determination of Se concentration down to ppm level in spite of presence of high Co, Fe, Ni, and Cr contents in the samples

  1. Fission reactor based epithermal neutron irradiation facilities for routine clinical application in BNCT-Hatanaka memorial lecture

    International Nuclear Information System (INIS)

    Harling, Otto K.

    2009-01-01

    Based on experience gained in the recent clinical studies at MIT/Harvard, the desirable characteristics of epithermal neutron irradiation facilities for eventual routine clinical BNCT are suggested. A discussion of two approaches to using fission reactors for epithermal neutron BNCT is provided. This is followed by specific suggestions for the performance and features needed for high throughput clinical BNCT. An example of a current state-of-the-art, reactor based facility, suited for routine clinical use is discussed. Some comments are provided on the current status of reactor versus accelerator based epithermal neutron sources for BNCT. This paper concludes with a summary and a few personal observations on BNCT by the author.

  2. Determination of 30 elements in coal and fly ash by thermal and epithermal neutron-activation analysis

    International Nuclear Information System (INIS)

    Rowe, J.J.; Steinnes, E.

    1977-01-01

    Thirty elements are determined in coal and fly ash by instrumental neutron-activation analysis using both thermal and epithermal irradiation. Gamma-ray spectra were recorded 7 and 20 days after the irradiations. The procedure is applicable to the routine analysis of coals and fly ash. Epithermal irradiation was found preferable for the determination of Ni, Zn, As, Se, Br, Rb, Sr, Mo, Sb, Cs, Ba, Sm, Tb, Hf, Ta, W, Th and U, whereas thermal irradiation was best for Sc, Cr, Fe, Co, La, Ce, Nd, Eu, Yb and Lu. Results for SRM 1632 (coal) and SRM 1633 (fly ash) agree with those of other investigators. (author)

  3. Qualitative dose response of the normal canine head to epithermal neutron irradiation with and without boron capture

    International Nuclear Information System (INIS)

    DeHaan, C.E.; Gavin, P.R.; Kraft, S.L.; Wheeler, F.J.; Atkinson, C.A.

    1992-01-01

    Boron Neutron Capture Therapy is being re-evaluated for the treatment of intracranial tumors. Prior to human clinical trials, determination of normal tissue tolerance is critical. Dogs were chosen as a large animal model for the following reasons. Dogs can be evaluated with advanced imaging, diagnostic and therapeutic modalities. Dogs are amenable to detailed neurologic examination and subtle behavioral changes are easily detected. Specifically, Labrador retrievers were chosen for their large body and head size. The dogs received varying doses of epithermal neutron irradiation and boron neutron capture irradiation using an epithermal neutron source. The dogs were closely monitored for up to one year post irradiation

  4. Epithermal neutron flux characterization of the TRIGA Mark III reactor, Salazar, Mexico, for use in Internal Neutron Activation Analysis

    International Nuclear Information System (INIS)

    Diaz Rizo, O.; Herrera Peraza, E.

    1996-01-01

    The non ideality of the epithermal neutron flux distribution at a reactor site parameter (made, using Chloramine-T method. Radiochemical purity and stability of the labelled product were determined by radiochromatography. The labelled Melagenine-II showed two radioactive fractions thermal-to-epithermal neutron ratio (f) were determined in the 3 typical irradiations positions of the TRIGA Mark III reactor of the National Nuclear Research Institute, Salazar, Mexico, using the Cd-ratio for multi monitor and bare bi-isotopic monitor methods respectively. This characterization is of use in the K o - method of neutron activation analysis, recently introduced at the Institute

  5. Radiobiology studies for the evaluation of epithermal neutron beams used for BNCT

    International Nuclear Information System (INIS)

    Green, S.; Jones, B.; Mill, A.J.

    2006-01-01

    This paper outlines our plans for a study to establish the radiobiological effectiveness of the various mixes of radiation components present in an epithermal neutron beam designed for BNCT and to incorporate these data into clinical protocols for the treatment of malignant glioma. This is a description of work which is funded and just now beginning in Birmingham so no results can be presented. Our project will involve a combination of experimental measurements carried out in Birmingham and in Boston and mathematical modelling carried out in Birmingham. Despite all the extant in-vitro and in-vivo work, there is no widely accepted method to determine biological effect by accounting for variations in beam component mix, dose rate and treatment fractionation for disparate from the various BNCT centres. The objectives of this study are: To develop a cell-based radiobiology protocol to provide essential data on safety and efficacy of beams for Boron Neutron Capture Therapy (BNCT) in advance of clinical trials. To exploit the facilities at Massachusetts Institute of Technology for variable dose-rate epithermal irradiations to validate the above protocol. To develop mathematical models of this radiobiological system that can be used to inform decisions on dose selection, fractionation schedules, BNCT use as supplementary boosts or for re-treatment of recurrent cancers. To provide fundamental data relevant to the understanding of the radiobiology of simultaneous mixed high-and low-LET radiations over a clinically relevant dose-range. (author)

  6. Method and apparatus for dual-spaced fast/epithermal neutron porosity measurements

    International Nuclear Information System (INIS)

    Smith, H.D. Jr.

    1986-01-01

    A method is described for determining the porosity of earth formations in the vicinity of a well borehole, comprising: (a) irradiating the earth formations in the vicinity of the well borehole with a continuous chemical type source of fast neutrons, (b) detecting the fast neutron population at a first shorter spaced distance from the neutron source in the borehole and generating signals representative thereof, (c) detecting the epithermal neutron population at a second space distance from the neutron source in the borehole and generating signals representative thereof, the second spaced distance being greater than the first spaced distance from the neutron source, (d) forming a ratio of the signals representing the fast and epithermal neutron populations to derive a measurement signal functionally related to the porosity of the earth formations in the vicinity of the borehole, and (e) calibrating the measurement signal according to a predetermined functional relationship to derive a porosity signal quantitatively representative of the porosity of the earth formations in the vicinity of the borehole

  7. Observation of distorted Maxwell-Boltzmann distribution of epithermal ions in LHD

    Science.gov (United States)

    Ida, K.; Kobayashi, T.; Yoshinuma, M.; Akiyama, T.; Tokuzawa, T.; Tsuchiya, H.; Itoh, K.; LHD Experiment Group

    2017-12-01

    A distorted Maxwell-Boltzmann distribution of epithermal ions is observed associated with the collapse of energetic ions triggered by the tongue shaped deformation. The tongue shaped deformation is characterized by the plasma displacement localized in the toroidal, poloidal, and radial directions at the non-rational magnetic flux surface in toroidal plasma. Moment analysis of the ion velocity distribution measured with charge exchange spectroscopy is studied in order to investigate the impact of tongue event on ion distribution. A clear non-zero skewness (3rd moment) and kurtosis (4th moment -3) of ion velocity distribution in the epithermal region (within three times of thermal velocity) is observed after the tongue event. This observation indicates the clear evidence of the distortion of ion velocity distribution from Maxwell-Boltzmann distribution. This distortion from Maxwell-Boltzmann distribution is observed in one-third of plasma minor radius region near the plasma edge and disappears in the ion-ion collision time scale.

  8. Reactor beam calculations to determine optimum delivery of epithermal neutrons for treatment of brain tumors

    International Nuclear Information System (INIS)

    Wheeler, F.J.; Nigg, D.W.; Capala, J.

    1997-01-01

    Studies were performed to assess theoretical tumor control probability (TCP) for brain-tumor treatment with boron neutron capture therapy (BNCT) using epithermal neutron sources from reactors. The existing epithermal-neutron beams at the Brookhaven Medical Research Reactor Facility (BMRR), the Petten High Flux Reactor Facility (HWR) and the Finnish Research Reactor 1 (FIR1) have been analyzed and characterized using common analytical and measurement methods allowing for this inter-comparison. Each of these three facilities is unique and each offers an advantage in some aspect of BNCT, but none of these existing facilities excel in all neutron-beam attributes as related to BNCT. A comparison is therefore also shown for a near-optimum reactor beam which does not currently exist but which would be feasible with existing technology. This hypothetical beam is designated BNCT-1 and has a spectrum similar to the FIR-1, the mono-directionality of the HFR and the intensity of the BMRR. A beam very similar to the BNCT-1 could perhaps be achieved with modification of the BMRR, HFR, or FIR, and could certainly be realized in a new facility with today's technology

  9. An in-situ check of the epithermal neutron log calibration

    International Nuclear Information System (INIS)

    Burkhard, N.R.

    1993-01-01

    The epithermal neutron log is used to measure the water content of the formation. The large hole epithermal neutron sonde (ENS) utilized at the Nevada Test Site (NTS) has been calibrated in the Hydrogen Content Test Facility (HCTF). These calibrations are used to correct the measured neutron count rate for the effects of tool stand-off and density. For some time, the suspicion has existed that the water contents that are calculated from the ENS data are too large. Hole U2gj represented a unique opportunity to check the validity of the ENS calibration under realistic logging conditions; a portion of the hole had been cemented and redrilled and then logged. The cements have a known water content and can be used as an in-situ calibration check. The author found that the water contents from the log data after processing with the existing calibrations are consistent with these known cement water contents. In addition, the study indicates that the raw neutron data might be more appropriately smoothed by using a median smoother rather than the currently utilized mean smoother

  10. An in-situ check of the epithermal neutron log calibration

    International Nuclear Information System (INIS)

    Burkhard, N.R.

    1993-09-01

    The epithermal neutron log is used to measure the water content of the formation. The large hole epithermal neutron sonde (ENS) that we utilize at the Nevada Test Site (NTS) has been calibrated in the Hydrogen Content Test Facility (HCTF). These calibrations are used to correct the measured neutron count rate for the effects of tool stand-off and density. For sometime, the suspicion has existed that the water contents that are calculated from the ENS data are too large. Hole U2gj represented a unique opportunity to check the validity of the ENS calibration under realistic logging conditions; a portion of the hole had been cemented and re drilled and then logged. The cements have a known water content and can be used as an in situ calibration check. I found that the water contents from the log data after processing with the existing calibrations are consistent with these known cement water contents. In addition, the study indicates that the raw neutron data might be more appropriately smoothed by using a median smoother rather than the currently utilized mean smoother

  11. The Chahnaly low sulfidation epithermal gold deposit, western Makran volcanic arc, southeastern Iran

    Science.gov (United States)

    Sholeh, Ali; Rastad, Ebrahim; Huston, David L.; Gemmell, J. Bruce; Taylor, Ryan D.

    2016-01-01

    The Chahnaly low-sulfidation epithermal Au deposit and nearby Au prospects are located northwest of the intermittently active Bazman stratovolcano on the western end of the Makran volcanic arc, which formed as the result of subduction of the remnant Neo-Tethyan oceanic crust beneath the Lut block. The arc hosts the Siah Jangal epithermal and Kharestan porphyry prospects, near Taftan volcano, as well as the Saindak Cu-Au porphyry deposit and world-class Reko Diq Cu-Au porphyry deposit, near Koh-i-Sultan volcano to the east-northeast in Pakistan. The host rocks for the Chahnaly deposit include early Miocene andesite and andesitic volcaniclastic rocks that are intruded by younger dacitic domes. Unaltered late Miocene dacitic ignimbrites overlie these rocks. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) U-Pb zircon geochronology data yield ages between 21.8 and 9.9 Ma for the acidic-intermediate regional volcanism. The most recent volcanic activity of the Bazman stratovolcano involved extrusion of an olivine basalt during Pliocene to Quaternary times. Interpretation of geochemical data indicate that the volcanic rocks are synsubduction and calc-alkaline to subalkaline. The lack of a significant negative Eu anomaly, a listric-shaped rare earth element pattern, and moderate La/Yb ratios of host suites indicate a high water content of the source magma.

  12. Power Burst Reactor Facility as an epithermal neutron source for brain cancer therapy

    International Nuclear Information System (INIS)

    Wheeler, F.J.

    1986-01-01

    The Power Burst Facility (PBF) reactor is considered for modification to provide an intense, clean source of intermediate-energy (epithermal) neutrons desirable for clinical studies of neutron capture therapy (NCT) for malignant tumors. The modifications include partial replacement of the reflector, installation of a neutron-moderating, shifting region, additional shielding, and penetration of the present concrete shield with a collimating (and optionally) filtering region. The studies have indicated that the reactor, after these modifications, will be safely operable at full power (28 MW) within the acceptable limits of the plant protection systems. The neutron beam exiting from the collimator port is predicted to be of sufficient intensity (approx.10 10 neutrons/cm 2 -s) to provide therapeutic doses in very short irradiation times. The beam would be relatively free of undesirable fast neutrons, thermal neutrons and gamma rays. The calculated neutron energy spectrum and associated gamma rays in the beam were provided as input in simulation studies that used a computer model of a patient with a brain tumor to determine predicted dose rates to the tumor and healthy tissue. The results of this conceptual study indicate an intense, clean beam of epithermal neutrons for NCT clinical trials is attainable in the PBF facility with properly engineered design modifications. 9 refs., 11 figs., 3 tabs

  13. Oxygen isotope zonation at the Golden Cross low-sulfidation epithermal gold deposit, New Zealand

    International Nuclear Information System (INIS)

    Mauk, J.L.; Simpson, M.P.

    2001-01-01

    Forty-one whole rock samples from the Gold Cross low-sulfidation epithermal Au-Ag deposit have δ 18 O values that range from 4.4 to 9.3 per mil, with an average value of 7.0 per mil. Unaltered and weakly altered rocks have δ 18 O values greater than 8 per mil, and the orebody is surrounded by samples that are depleted in 18 O. A strongly silicified sample adjacent to the Empire Vein System has a δ 18 O value of 9.0 per mil, similar to previously reported analyses of vein quartz (7.0 to 11.7 per mil, average 9.4 per mil). This suggests that, in detail, Golden Cross may have a zone of 18 O-enriched wall rocks in the core of the deposit, adjacent to the main underground veins. Although some workers have suggested that stable isotope geochemistry may provide useful information for epithermal mineral deposit exploration, at Golden Cross this is not the case. Alteration minerals, major elements and trace elements all define larger, less ambiguous halos than the zone of 18 O-depleted wall rocks. (author). 21 refs., 3 figs., 1 tab

  14. Upper Paleozoic Marine Shale Characteristics and Exploration Prospects in the Northwestern Guizhong Depression, South China

    Science.gov (United States)

    Zhu, Zhenhong; Yao, Genshun; Lou, Zhanghua; Jin, Aimin; Zhu, Rong; Jin, Chong; Chen, Chao

    2018-05-01

    Multiple sets of organic-rich shales developed in the Upper Paleozoic of the northwestern Guizhong Depression in South China. However, the exploration of these shales is presently at a relatively immature stage. The Upper Paleozoic shales in the northwestern Guizhong Depression, including the Middle Devonian Luofu shale, the Nabiao shale, and the Lower Carboniferous Yanguan shale, were investigated in this study. Mineral composition analysis, organic matter analysis (including total organic carbon (TOC) content, maceral of kerogen and the vitrinite reflection (Ro)), pore characteristic analysis (including porosity and permeability, pore type identification by SEM, and pore size distribution by nitrogen sorption), methane isothermal sorption test were conducted, and the distribution and thickness of the shales were determined, Then the characteristics of the two target shales were illustrated and compared. The results show that the Upper Paleozoic shales have favorable organic matter conditions (mainly moderate to high TOC content, type I and II1 kerogen and high to over maturity), good fracability potential (brittleness index (BI) > 40%), multiple pore types, stable distribution and effective thickness, and good methane sorption capacity. Therefore, the Upper Paleozoic shales in the northern Guizhong Depression have good shale gas potential and exploration prospects. Moreover, the average TOC content, average BI, thickness of the organic-rich shale (TOC > 2.0 wt%) and the shale gas resources of the Middle Devonian shales are better than those of the Lower Carboniferous shale. The Middle Devonian shales have better shale gas potential and exploration prospects than the Lower Carboniferous shales.

  15. Late Paleozoic volcanic rocks of the Intra-Sudetic Basin, Bohemian Massif: Petrological and geochemical characteristics

    Czech Academy of Sciences Publication Activity Database

    Ulrych, Jaromír; Fediuk, F.; Lang, Miloš; Martinec, Petr

    2004-01-01

    Roč. 64, č. 2 (2004), s. 127-153 ISSN 0009-2819 R&D Projects: GA AV ČR(CZ) IAA3013903 Keywords : Late Paleozoic * volcanic rocks * Bohemian Massif Subject RIV: DB - Geology ; Mineralogy Impact factor: 0.643, year: 2004

  16. The late Paleozoic ecological-evolutionary laboratory, a land-plant fossil record perspective

    NARCIS (Netherlands)

    Looy, Cindy; Kerp, Hans; Duijnstee, Ivo; DiMichele, Bill

    2014-01-01

    In this essay we examine the fossil record of land plants, focusing on the late Paleozoic. We explore the nature of this record in terms of what is preserved, where, why and with what biases. And as a consequence, how it can be used to answer questions posed at various spatial and temporal scales,

  17. Pore characteristics of shale gas reservoirs from the Lower Paleozoic in the southern Sichuan Basin, China

    Directory of Open Access Journals (Sweden)

    Xianqing Li

    2016-06-01

    Full Text Available Data was acquired from both the drillings and core samples of the Lower Paleozoic Qiongzhusi and Longmaxi Formations' marine shale gas reservoirs in the southern Sichuan Basin by means of numerous specific experimental methods such as organic geochemistry, organic petrology, and pore analyses. Findings helped determine the characteristics of organic matter, total porosity, microscopic pore, and pore structure. The results show that the Lower Paleozoic marine shale in the south of the Sichuan Basin are characterized by high total organic carbon content (most TOC>2.0%, high thermal maturity level (RO = 2.3%–3.8%, and low total porosity (1.16%–6.87%. The total organic carbon content and thermal maturity level of the Qiongzhusi Formation shale are higher than those of the Longmaxi Formation shale, while the total porosity of the Qiongzhusi Formation shale is lower than that of the Longmaxi Formation shale. There exists intergranular pore, dissolved pore, crystal particle pore, particle edge pore, and organic matter pore in the Lower Paleozoic Qiongzhusi Formation and Longmaxi Formation shale. There are more micro-nano pores developed in the Longmaxi Formation shales than those in the Qiongzhusi Formation shales. Intergranular pores, dissolved pores, as well as organic matter pores, are the most abundant, these are primary storage spaces for shale gas. The microscopic pores in the Lower Paleozoic shales are mainly composed of micropores, mesopores, and a small amount of macropores. The micropore and mesopore in the Qiongzhusi Formation shale account for 83.92% of the total pore volume. The micropore and mesopore in the Longmaxi Formation shale accounts for 78.17% of the total pore volume. Thus, the micropores and mesopores are the chief components of microscopic pores in the Lower Paleozoic shale gas reservoirs in the southern Sichuan Basin.

  18. Epithermal neutron beam design for neutron capture therapy at the Power Burst Facility and the Brookhaven Medical Research Reactor

    International Nuclear Information System (INIS)

    Wheeler, F.J.; Parsons, D.K.; Rushton, B.L.; Nigg, D.W.

    1990-01-01

    Nuclear design studies have been performed for two reactor-based epithermal neutron beams for cancer treatment by neutron capture therapy (NCT). An intermediate-intensity epithermal beam has been designed and implemented at the Brookhaven Medical Research Reactor (BMRR). Measurements show that the BMRR design predictions for the principal characteristics of this beam are accurate. A canine program for research into the biological effects of NCT is now under way at BMRR. The design for a high-intensity epithermal beam with minimal contamination from undesirable radiation components has been finalized for the Power Burst Facility (PBF) at the Idaho National Engineering Laboratory. This design will be implemented when it is determined that human NCT trials are advisable. The PBF beam will exhibit approximately an order of magnitude improvement in absolute epithermal flux intensity over that available in the BMRR, and its angular distribution and spectral characteristics will be more advantageous for NCT. The combined effects of beam intensity, angular distribution, spectrum, and contaminant level allow the desired tumor radiation dose to be delivered in much shorter times than are possible with the currently available BMRR beam, with a significant reduction (factor of 3 to 5) in collateral dose due to beam contaminants

  19. 8-group relative delayed neutron yields for epithermal neutron induced fission of 235U and 239Pu

    International Nuclear Information System (INIS)

    Piksaikin, V.M.; Kazakov, L.E.; Isaev, S.G.; Korolev, G.G.; Roshchenko, V.A.; Tertychnyj, R.G

    2002-01-01

    An 8-group representation of relative delayed neutron yields was obtained for epithermal neutron induced fission of 235 U and 239 Pu. These data were compared with ENDF/B-VI data in terms of the average half- life of the delayed neutron precursors and on the basis of the dependence of reactivity on the asymptotic period. (author)

  20. Telescoped porphyry-style and epithermal veins and alteration at the central Maratoto valley prospect, Hauraki Goldfield, New Zealand

    International Nuclear Information System (INIS)

    Simpson, M.P.; Mauk, J.L.; Kendrick, R.G.

    2004-01-01

    At the central Maratoto valley prospect, southern Coromandel Peninsula, New Zealand, andesite flows and dacite breccias host rare porphyry-style quartz veins that are telescoped by widespread epithermal veins and alteration. Early porphyry-style quartz veins, which lack selvages of porphyry-style alteration, host hypersaline fluid inclusions that contain several translucent daughter crystals, including halite and sylvite. Overprinting epithermal veins and alteration are divided into two stages. Main-stage epithermal alteration and veins are characterised by the successive deposition of pyrite, quartz, and ankerite-dolomite veinlets coupled with intense alteration of the wall rock to quartz, illite, interlayer illite-smectite (≤ 10% smectite), chlorite, pyrite, ankerite, and dolomite. Late-stage epithermal veins and alteration are characterised by the formation of calcite and siderite veinlets, coupled with overprinting of the wall rocks by both these minerals. Multiphase fluid inclusions in a porphyry-style quartz vein formed at temperatures >400 degrees C and trapped hypersaline magmatic fluid. Lower temperature secondary liquid-rich inclusions in the porphyry-style quartz vein homogenise between 283 and 329 degrees C and trapped a dilute fluid with 18 O (VSMOW) values of 13.5-18.1 permille, whereas late-stage epithermal calcite has δ 18 O (VSMOW) values of 3.1-5.1 permille. Calculated isotopic compositions for the fluid in equilibrium with ankerite-dolomite and calcite at 260 degrees C, averages 6 and -3 permille, respectively. The enriched value for main-stage ankerite-dolomite suggests formation from waters that underwent significant water-rock exchange, whereas isotopically lighter water that formed late-stage calcite underwent little water-rock interaction. We propose a three-stage model to explain telescoped veins and alteration styles at the central Maratoto valley prospect area. Porphyry-style quartz veins were the first to form from hot hypersaline

  1. A spin-transport system for a longitudinally polarized epithermal neutron beam

    International Nuclear Information System (INIS)

    Crawford, B.E.; Bowman, J.D.; Penttilae, S.I.; Roberson, N.R.

    2001-01-01

    The TRIPLE (Time Reversal and Parity at Low Energies) collaboration uses a polarized epithermal neutron beam and a capture γ-ray detector to study parity violation in neutron-nucleus reactions. In order to preserve the spin polarization of the neutrons as they travel the 60-m path to the target, the beam pipes are wrapped with wire to produce a solenoidal magnetic field of about 10 G along the beam direction. The flanges and bellows between sections of the beam pipe cause gaps in the windings which in turn produce radial fields that can depolarize the neutron spins. A computer code has been developed that numerically evaluates the effect of these gaps on the polarization. A measurement of the neutron depolarization for neutrons in the actual spin-transport system agrees with a calculation of the neutron depolarization for the TRIPLE system. Features that will aid in designing similar spin-transport systems are discussed

  2. Distribution of 35 Elements in Peat Cores from Ombrotrophic Bogs Studied by Epithermal Neutron Activation Analysis

    CERN Document Server

    Frontasyeva, M V

    2004-01-01

    In ombrotrophic bogs the surface peat layer is supplied with chemical substances only from the atmosphere. Peat cores from these bogs therefore can be used to study temporal trends in atmospheric deposition of pollutants. In this work epithermal neutron activation analysis was applied for the first time to study the distribution of 35 elements in peat profiles from ombrotrophic bogs. The selected examples were from Finnmark county in northern Norway: one pristine site far from any local pollution source, and another strongly affected by long-term operation of Russian copper-nickel smelters located close to the border. The elements are classified with respect to their behavior in the uppermost 40 cm of the peat, and similarities and differences between the two profiles are discussed. As compared with other more commonly used analytical techniques based on acid decomposition of the sample ENAA has the advantage of providing the total concentrations of the elements.

  3. Measurement of the epithermal neutron flux of the Argonauta reactor by the Sandwich method

    International Nuclear Information System (INIS)

    Nascimento, H.M.

    1973-01-01

    A common method of obtaining information about the neutron spectrum in the energy range of 1 eV to a few keV is by using resonance sandwich detectors. A sandwich detector is usually made up of three foils placed one on top of the other, each having the same thickness and being made of the same material which has a pronounced absorption resonance. To make an adequate evaluation, the sandwich method was compared with one using an isolated detector. The results obtained from approximate theoretical calculations were checked experimentally, using In, Au and Mn foils, in an isotropic 1/E flux in the Argonaut Reactor at I.E.N. As practical application of this method, the deviation from a 1/E spectrum of the epithermal neutron flux in the core and external graphite reflector of the Argonaut Reactor has been measured with the sandwich foils previously calibrated in a 1/E spectrum. (author)

  4. Combination of epithermal and inelastic neutron scattering methods to locate coal and oil-shale zones

    International Nuclear Information System (INIS)

    Schultz, W.E.

    1976-01-01

    A pulsed neutron generator of the deuterium-tritium reaction type irradiates earth formations in the vicinity of a borehole with 14 MeV neutrons. Gamma rays produced by the inelastic scattering of the fast neutrons are observed in four energy regions of the gamma ray energy spectrum corresponding to the inelastic scattering of neutrons by carbon, oxygen, silicon, and calcium. The carbon/oxygen, calcium/silicon, and carbon plus oxygen gamma rays are found and combined with a separately derived hydrogen index log to determine the quality of coal-bearing formations or oil-shale regions. The hydrogen index curve is found preferably by a dual-spaced detector epithermal neutron porosity logging technique or from a conventional thermal neutron gamma ray log

  5. Filtered epithermal quasi-monoenergetic neutron beams at research reactor facilities

    International Nuclear Information System (INIS)

    Mansy, M.S.; Bashter, I.I.; El-Mesiry, M.S.; Habib, N.; Adib, M.

    2015-01-01

    Filtered neutron techniques were applied to produce quasi-monoenergetic neutron beams in the energy range of 1.5–133 keV at research reactors. A simulation study was performed to characterize the filter components and transmitted beam lines. The filtered beams were characterized in terms of the optimal thickness of the main and additive components. The filtered neutron beams had high purity and intensity, with low contamination from the accompanying thermal emission, fast neutrons and γ-rays. A computer code named “QMNB” was developed in the “MATLAB” programming language to perform the required calculations. - Highlights: • Quasi-monoenergetic neutron beams in energy range from (1.5–133) keV. • Interference between the resonance and potential scattering amplitudes. • Epithermal neutron beams used in BNCT

  6. Study on iodine levels in thyroids of iodine-supplemented rats by epithermal neutron activation analysis

    International Nuclear Information System (INIS)

    Wang Xuefei; Zhang Fang; Xu Qing; Liu Nianqing; Chai Zhifang; Zhao Xueqin; Zuo Aijun

    2003-01-01

    The second generation female Wistar rats that have been treated with iodine-deficient food, after their delivery, are divided into three groups i.e. excessive-iodine (EI), adequate-iodine (AI) and iodine-deficient (ID) according to the KIO 3 concentration in the drinking water (3.0, 0.4, 0 mg/L). In addition, the normal rats with low iodine food and 0.4 mg/L KIO 3 water are used as the control group (C). The iodine content in thyroid and the serum thyroid hormone levels of the third generation rats are measured by means of epithermal neutron activation analysis (ENAA), and the method of enzyme-linked immunosorbent assay (ELISA), respectively. The results indicate that the total thyroxine (TT 4 ) and the free thyroxine (FT 4 ) of the EI, compared with those of the controls, are significantly decreased (p 3 ) evidently increased (p 4 , FT 4 and goiter

  7. Bromine and iodine in Chinese medical herbs determined via epithermal neutron activation analysis

    International Nuclear Information System (INIS)

    Chien-Yi Chen; Yuan-Yaw Wei; Sheng-Pin ChangLai; Lung-Kwang Pan

    2003-01-01

    Nineteen natural herbs and two prescriptions prepared from mixed herbs were analyzed via epithermal neutron activation analysis (ENAA) to evaluate their bromine and iodine concentration. Traditional medical doctors prescribed the samples presented in this work to most Taiwanese children for strengthening their immune systems. Empirical results indicated a wide diversity of bromine in the samples. Yet, the iodine concentration was only around one to tenth or twentieth of the bromine. The maximum daily intake (MDI) for various medical herbs was also widely diversified from one to tenfold on the basis of various criteria. The minimum detectable concentration (MDC) of bromine and iodine found was 0.42±0.14 ppm and 0.067±0.016 ppm, respectively. Compared to that from conventional thermal neutron activation analysis (NAA) for a similar evaluation, the extremely low MDC obtained here was attributed to the large amount of thermal neutron absorption during sample irradiation. (author)

  8. Study on the determination of uranium by activation analysis with epithermal neutrons

    International Nuclear Information System (INIS)

    Atalla, L.T.

    1977-01-01

    A method is described that is applied to the determination of uranium in different types of materials, either by an entirely instrumental method or with the chemical separation of uranium-239, when the presence of interferences does not allow the instrumental analysis. The advantages and disadvantages in the use of epithermal neutrons in the activation of samples for a more selective activation of uranium-238 also presented. The instrumental method is tested through standart materials, accepted internationally. The possibility of uranium extraction with di-etil-hexilphosphoric acid is also presented and the choice of the former technique is justified. The sensitibility of the method is discussed as well as precision and accuracy through results obtained in the analysis of the standards and the calibration curve of uranium [pt

  9. Elimination of eight interfering radioisotopes in the determination of uranium by activation analysis with epithermic neutrons

    International Nuclear Information System (INIS)

    Requejo, C.S.

    1977-01-01

    The total or parcial elimination interfering radioisotopes in activation analysis of uranium by epithermic neutrons, has been made. It was possible to determine uranium, after chemical separation, from samples of organic and mineral matrixes, which had mercury, selenium, bromine, antimony, gold, barium, molybden and tungsten. Mineral samples were analysed giving results between 0.2 to 5.0 ppm of uranium. The same mineral were ground in agate mortar and in tungsten carbide mill. In the first sample is has been found 0.2277 +- -+ 0.0474 ppm U. The second which had tungsten, at level of 150 ppm, after radiochemical separation, it has been found 0.2465+- -+0.0326 ppm U. These results are considered statistically the same [pt

  10. Characterisation of the epithermal neutron irradiation facility at the Portuguese research reactor using MCNP.

    Science.gov (United States)

    Beasley, D G; Fernandes, A C; Santos, J P; Ramos, A R; Marques, J G; King, A

    2015-05-01

    The radiation field at the epithermal beamline and irradiation chamber installed at the Portuguese Research Reactor (RPI) at the Campus Tecnológico e Nuclear of Instituto Superior Técnico was characterised in the context of Prompt Gamma Neutron Activation Analysis (PGNAA) applications. Radiographic films, activation foils and thermoluminescence dosimeters were used to measure the neutron fluence and photon dose rates in the irradiation chamber. A fixed-source MCNPX model of the beamline and chamber was developed and compared to measurements in the first step towards planning a new irradiation chamber. The high photon background from the reactor results in the saturation of the detector and the current facility configuration yields an intrinsic insensitivity to various elements of interest for PGNAA. These will be addressed in future developments. Copyright © 2015 Elsevier Ltd. All rights reserved.

  11. Physical parameters and biological effects of the LVR-15 epithermal neutron beam

    International Nuclear Information System (INIS)

    Burian, J.; Marek, M.; Rejchrt, J.; Viererbl, L.; Gambarini, G.; Mares, V.; Vanossi, E.; Judas, L.

    2006-01-01

    Monitoring of the physical and biological properties of the epithermal neutron beam constructed at the multipurpose LVR-15 nuclear reactor for NCT therapy of brain tumors showed that its physical and biological properties are stable in time and independent on an ad hoc reconfiguration of the reactor core before its therapeutic use. Physical parameters were monitored by measurement of the neutron spectrum, neutron profile, fast neutron kerma rate in tissue and photon absorbed dose, the gel dosimetry was used with the group of standard measurement methods. The RBE of the beam, as evaluated by 3 different biological models, including mouse intestine crypt regeneration assay, germinative zones of the immature rat brain and C6 glioma cells in culture, ranged from 1.70 to 1.99. (author)

  12. Manual for the Epithermal Neutron Multiplicity Detector (ENMC) for Measurement of Impure MOX and Plutonium Samples

    International Nuclear Information System (INIS)

    Menlove, H. O.; Rael, C. D.; Kroncke, K. E.; DeAguero, K. J.

    2004-01-01

    We have designed a high-efficiency neutron detector for passive neutron coincidence and multiplicity counting of dirty scrap and bulk samples of plutonium. The counter will be used for the measurement of impure plutonium samples at the JNC MOX fabrication facility in Japan. The counter can also be used to create working standards from bulk process MOX. The detector uses advanced design "3He tubes to increase the efficiency and to shorten the neutron die-away time. The efficiency is 64% and the die-away time is 19.1 ?s. The Epithermal Neutron Multiplicity Counter (ENMC) is designed for high-precision measurements of bulk plutonium samples with diameters of less than 200 mm. The average neutron energy from the sample can be measured using the ratio of the inner ring of He-3 tubes to the outer ring. This report describes the hardware, performance, and calibration for the ENMC.

  13. Photon detectors for epithermal neutron scattering at high-ω and low-q

    International Nuclear Information System (INIS)

    Pietropaolo, A.; Senesi, R.; Tardocchi, M.; Andreani, C.; Gorini, G.

    2004-01-01

    Inelastic epithermal neutron scattering at high energy (ℎω≥1 eV) and low wave vector (q≤10 A -1 ) transfers is the unique technique for the investigation of high-energy excitations in a variety of systems, ranging from magnetic materials to semiconductors. The key issue in order to make these measurements feasible on inverse geometry spectrometers, is to develop suitable detection systems for neutrons in the energy range 1-100 eV. The Resonance Detector Spectrometer configuration has to be considered as the most promising approach for electron Volt neutron spectroscopy. This configuration will be employed in the new low angle detector bank, VLAD, planned for VESUVIO spectrometer operating at ISIS source

  14. Examination of Greek neolithic ceramic shards by epithermal neutron activation analysis

    International Nuclear Information System (INIS)

    Ochsenkuehn, K.M.; Zouridakis, N.; Inst. of Physical Chemistry, Athens; Ochsenkuehn-Petropulu, M.

    1999-01-01

    At the reactor of the NCSR 'Demokritos' epithermal irradiation was used in connection with a loss-free counting technique to investigate rare Neolithic ceramic shards, about 4000 years old, from the Alepotrypa Cave of Diros, Greece. The application of an irradiation time of 30 minutes, the measurements of the samples after less then 24 hours and a counting time of 20 minutes in connection with a loss-free counting unit allowed the determination of 12 elements per sample. The comparison of these rare fine ceramic shards with those of primitive shape showed that both were produced from the same raw materials. Small differences could be explained by a raw material pretreatment. The Neolithic potters were obviously aware of separation techniques in order to obtain fine clay fractions to produce those rare ceramics. (author)

  15. Effective dose evaluation for BNCT treatment in the epithermal neutron beam at THOR

    Energy Technology Data Exchange (ETDEWEB)

    Wang, J.N. [Department of Engineering and System Science, National Tsing Hua University, No. 101, Section 2, Kuang-Fu Rd., Hsinchu 30013, Taiwan (China)] [Division of Health Physics, Institute of Nuclear Energy Research, No. 1000, Wenhua Rd., Jiaan Village, Longtan Township, Taoyuan County 32546, Taiwan (China); Huang, C.K. [Institute of Nuclear Engineering and Science, National Tsing Hua University, No. 101, Section 2, Kuang-Fu Rd., Hsinchu 30013, Taiwan (China); Tsai, W.C. [Department of Engineering and System Science, National Tsing Hua University, No. 101, Section 2, Kuang-Fu Rd., Hsinchu 30013, Taiwan (China); Liu, Y.H. [Nuclear Science and Technol. Develop. Center, National Tsing Hua University, No. 101, Section 2, Kuang-Fu Rd., Hsinchu 30013, Taiwan (China); Jiang, S.H., E-mail: shjiang@mx.nthu.edu.tw [Department of Engineering and System Science, National Tsing Hua University, No. 101, Section 2, Kuang-Fu Rd., Hsinchu 30013, Taiwan (China)] [Institute of Nuclear Engineering and Science, National Tsing Hua University, No. 101, Section 2, Kuang-Fu Rd., Hsinchu 30013, Taiwan (China)

    2011-12-15

    This paper aims to evaluate the effective dose as well as equivalent doses of several organs of an adult hermaphrodite mathematical phantom according to the definition of ICRP Publication 60 for BNCT treatments of brain tumors in the epithermal neutron beam at THOR. The MCNP5 Monte Carlo code was used for the calculation of the average absorbed dose of each organ. The effective doses for a typical brain tumor treatment with a tumor treatment dose of 20 Gy-eq were evaluated to be 0.59 and 0.35 Sv for the LLAT and TOP irradiation geometries, respectively. In addition to the stochastic effect, it was found that it is also likely to produce deterministic effects, such as cataracts and depression of haematopoiesis.

  16. Determination of trace cadmium and other elements in bone by epithermal neutron activation analysis

    International Nuclear Information System (INIS)

    Dowlati, R.; Jervis, R.E.

    1991-01-01

    Epithermal neutron activation analysis (ENAA) was applied to measure quantitatively Cd and other elements in bone samples from control and Cd-fed rats. This method was found to be non-destructive to the bone samples, with no sign of 'radiolytic charring' and was sensitive enough to detect and quantify Cd in bone samples at normal levels for mammals (viz. 0.5-1.0μg/g) and higher. Two different thermal neutron shield materials were utilized, namely cadmium and boron. The boron shield resulted in a 27% improvement in the detection limit of Cd in bone. The accuracy of ENAA for Cd was assessed by intercomparison with electrothermal atomic absorption spectrophotometry (ETAAS), and the results were in fair agreement (±23%) with those from ENAA. (author) 24 refs.; 5 tabs

  17. Measurement of trace cadmium and elements in bone by epithermal neutron activation analysis

    International Nuclear Information System (INIS)

    Dowlati, R.; Jervis, R.E.

    1991-01-01

    Epithermal neutron activation analysis (ENAA) was applied to measure quantitatively Cd and other elements in bone samples from control and Cd-fed rats. This method was found to be non-destructive to the bone samples, with no sign of 'radiolytic charring' and was sensitive enough to detect and quantify Cd in bone samples at normal levels for mammals (viz. 0.5-1.0 μg/g) and higher. Two different thermal neutron shield materials were utilized, namely cadmium and boron. The boron shield resulted in a 27% improvement in the detection limit of Cd in bone. The accuracy of ENAA for Cd was assessed by intercomparison with electrothermal atomic absorption spectrophotometry (ETAAS), and the results in fair agreement (±23%) with those from ENAA

  18. Treatment planning figures of merit in thermal and epithermal boron capture therapy of brain tumours

    Energy Technology Data Exchange (ETDEWEB)

    Wallace, S.A.; Mathur, J.N. (Wollongong Univ., NSW (Australia)); Allen, B.J. (Ansto PMB 1 Menai, NSW (Australia). Biomedicine and Health)

    1994-05-01

    The boron neutron capture therapy (BNCT) figures of merit of advantage depth, therapeutic depth, modified advantage depth and maximum therapeutic depth have been studied as functions of [sup 10]B tumour to blood ratios and absolute levels. These relationships were examined using the Monte Carlo neutron photon transport code, MCNP, with an ideal 18.4 cm diameter neutron beam incident laterally upon an ellipsoidal neutron photon brain-equivalent model. Mono-energetic beams of 0.025 eV (thermal) and 35 eV (epithermal) were simulated. Increasing the tumour to blood [sup 10]B ratio predictably increases all figures of merit. [sup 10]B concentration was also shown to have a strong bearing on the figures of merit when low levels were present in the system. This is the result of a non-[sup 10]B dependent background dose. At higher levels however, the concentration of [sup 10]B has a diminishing influence. For boron sulphydryl (BSH), little advantage is gained by extending the blood [sup 10]B level beyond 30 ppm, whilst for D, L,-p-boronophenylalanine (BPA) this limit is 10 ppm. Applying the epithermal beam under identical conditions, the therapeutic depth reaches the brain mid-line with a tumour to blood [sup 10]B ratio of only 5.7 for BPA. For BSH, the maximum therapeutic depth reaches the brain mid-line with a tumour to blood ratio of only 1.9 with 30 ppm in the blood. Human data for these compounds are very close to these requirements. (author).

  19. Geochemistry and statistical analyses of porphyry system and epithermal veins at Hizehjan in northwestern Iran

    Directory of Open Access Journals (Sweden)

    Radmard Kaikhosrov

    2017-12-01

    Full Text Available Situated about 130 km northeast of Tabriz (northwest Iran, the Mazra’eh Shadi deposit is in the Arasbaran metallogenic belt (AAB. Intrusion of subvolcanic rocks, such as quartz monzodiorite-diorite porphyry, into Eocene volcanic and volcano-sedimentary units led to mineralisation and alteration. Mineralisation can be subdivided into a porphyry system and Au-bearing quartz veins within andesite and trachyandesite which is controlled by fault distribution. Rock samples from quartz veins show maximum values of Au (17100 ppb, Pb (21100 ppm, Ag (9.43ppm, Cu (611ppm and Zn (333 ppm. Au is strongly correlated with Ag, Zn and Pb. In the Au-bearing quartz veins, factor group 1 indicates a strong correlation between Au, Pb, Ag, Zn and W. Factor group 2 indicates a correlation between Cu, Te, Sb and Zn, while factor group 3 comprises Mo and As. Based on Spearman correlation coefficients, Sb and Te can be very good indicator minerals for Au, Ag and Pb epithermal mineralisation in the study area. The zoning pattern shows clearly that base metals, such as Cu, Pb, Zn and Mo, occur at the deepest levels, whereas Au and Ag are found at higher elevations than base metals in boreholes in northern Mazra’eh Shadi. This observation contrasts with the typical zoning pattern caused by boiling in epithermal veins. At Mazra’eh Shadi, quartz veins containing co-existing liquid-rich and vapour-rich inclusions, as strong evidence of boiling during hydrothermal evolution, have relatively high Au grades (up to 813 ppb. In the quartz veins, Au is strongly correlated with Ag, and these elements are in the same group with Fe and S. Mineralisation of Au and Ag is a result of pyrite precipitation, boiling of hydrothermal fluids and a pH decrease.

  20. Structural Characteristics of Paleozoic and Geological Significance of Oil and Gas of Dongpu Depression

    Institute of Scientific and Technical Information of China (English)

    杨世刚

    2003-01-01

    The Dongpu depression has experienced a complicated evolution of structure since Mesozoic. The Paleozoic carbonate rock has been strongly reformed and the buried hills with different characteristics of structure are developed in the depression. There exist lots of groups of fault structures with strikes of NNE(or NE),NW, near NS and EW etc., of which the faults with strikes of NNE and NW play an important controlling role on present-day structural framework of the depression. The faults with near NS-striking and EW-striking deeply affect the establishment of structural framework of basement of the depression. Although most of the fractures are filled by calcite and other minerals, under the action of later structural stress, the earlier fractures could change their features into tensional ones. Therefore, much attention should be paid to the exploration and exploitation of Paleozoic oil and gas in Dongpu depression.

  1. Late Paleozoic paleofjord in the southernmost Parana Basin (Brazil): Geomorphology and sedimentary fill

    Science.gov (United States)

    Tedesco, Julia; Cagliari, Joice; Coitinho, Julia dos Reis; da Cunha Lopes, Ricardo; Lavina, Ernesto Luiz Correa

    2016-09-01

    In the southernmost part of the Parana Basin, records of the late Paleozoic glaciation occur in a discontinuous form preserved in paleovalley systems excavated in the crystalline basement. This paper addresses one of these paleovalleys, the Mariana Pimentel, which extends over 60 km with NW-SE valley direction and a constant width of 2.5 km. With the objective of demonstrating that the paleovalley worked as a fjord during the glaciation period, its origin as well as sedimentary fill and morphology were analyzed. The paleovalley morphology was obtained through electrical resistivity (electrical sounding and lateral mapping) and mathematical modeling in four transverse sections. The morphology of the paleovalley documented by the U-shape, steady width, and high depth reaching up to 400 m are typical features of modern glacial valleys. The sedimentary facies that fill the base of the paleovalley, such as rhythmites and dropstones with thickness up to 70 m and diamictites with faceted pebbles (up to 5 m thick) are signs of its glacial origin. During the glaciation period, the paleovalley had a connection to the epicontinental sea located to the northwest, extended toward Namibia, and was excavated by glaciers from the highlands of this region. Thus, the evidence attests that the Mariana Pimentel paleovalley was a fjord during the late Paleozoic glaciation. The duration of the late Paleozoic glaciation (which is longer than the Quaternary glaciation), the apatite fission track that suggests erosion up to 4 km thick in the study area, and the lack of preserved hanging valleys in the Mariana Pimentel indicate that the paleovalley once featured a higher dimension. Furthermore, the existence of paleofjords excavated in the border of the basement corroborates the idea of small ice centers controlled by topography during the late Paleozoic glaciation.

  2. Oral Region Homologies in Paleozoic Crinoids and Other Plesiomorphic Pentaradial Echinoderms

    OpenAIRE

    Kammer, Thomas W.; Sumrall, Colin D.; Zamora, Samuel; Ausich, William I.; Deline, Bradley

    2013-01-01

    The phylogenetic relationships between major groups of plesiomorphic pentaradial echinoderms, the Paleozoic crinoids, blastozoans, and edrioasteroids, are poorly understood because of a lack of widely recognized homologies. Here, we present newly recognized oral region homologies, based on the Universal Elemental Homology model for skeletal plates, in a wide range of fossil taxa. The oral region of echinoderms is mainly composed of the axial, or ambulacral, skeleton, which apparently evolved ...

  3. Geological analysis of paleozoic large-scale faulting in the south-central Pyrenees

    OpenAIRE

    Speksnijder, A.

    1986-01-01

    Detailed structural and sedimentological analysis reveals the existence of an east-west directed fundamental fault zone in the south-central Pyrenees, which has been intermittently active from (at least) the Devonian on. Emphasis is laid on the stUdy of fault-bounded post-Variscan (StephanoPermian) sedimentary basins, and the influence of Late Paleozoic faulting on the underlying Variscan basement. The present structure of the basement is rather complex as it results from multiple Variscan an...

  4. The fossil record, function, and possible origins of shell color patterns in Paleozoic marine invertebrates

    Energy Technology Data Exchange (ETDEWEB)

    Kobluk, D.R. (Univ. of Toronto, Ontario (Canada)); Mapes, R.H. (Ohio Univ., Athens (USA))

    1989-02-01

    Fossil invertebrate shells and carapaces displaying preserved original color patterns are among the rarest fossils. The fossil record of color patterns extends into the Middle Cambrian where the trilobite Anomocare displays a fan-like array of stripes on the pygidium. About 180 Paleozic genera are known with patterns, including trilobites, cephalopods, gastropods, brachiopods, bivalves, crinoids, and crustaceans. Based upon an analysis of these taxa, it appears that patterns and pigments in middle and late Paleozoic invertebrates may have served several functions such as warning displays, light screening, camouflage, or waste disposal. However, the presence of color patterns in fossil invertebrates in the early Paleozoic may have developed prior to the evolution of vision sufficiently sophisticated to see them. This suggests that camouflage and warning displays were not the original functions of color patterns, and that in the earliest Paleozoic they may not have been functional. The authors propose a hypothesis that involves three developmental phases in the evolution of invertebrate color patterns: (1) the incorporation of metabolic by-products, perhaps some pigmented and some not pigmented, into shells and carapaces as a means of disposal of dietary or metabolic wastes, (2) use of these pigments and patterns as an environmental adaptation, such as light screening, and (3) display during and following the evolution of vision in predators sufficiently sophisticated to see the patterns.

  5. The Paleozoic ichthyofauna of the Amazonas and Parnaíba basins, Brazil

    Science.gov (United States)

    Figueroa, Rodrigo Tinoco; Machado, Deusana Maria da Costa

    2018-03-01

    The Brazilian Paleozoic ichthyofauna from the Parnaíba and Amazonas basins regard a sparsely known diversity, including chondrichthyans and acanthodians, besides some osteichthyan remains. This work proposes a revision of the fossil material from these two sedimentary basins and synthesizes the morphological aspect of such material trying to understand the influences of those fossils to the paleontology of the region, comparing the Brazilian fossils with other gondwanan faunas. The Brazilian Paleozoic fish fauna shows great resemblance to those of Bolivia, especially during the Devonian. Many of the Acanthodian spines from the Manacapuru Formation (Amazonas Basin), and the Pimenteira Formation (Parnaíba Basin), are comparable to the taxa found in Bolivia. The lack of more Placoderm remains in the Brazilian outcrops is similar to the low diversity of this group in Bolivia, when compared to other South American and Euramerican localities. The most diverse Brazilian ichthyofauna is encountered in the Permian Pedra de Fogo Formation where numerous chondrichthyans and 'paleopterygians' remains are found, together with dipnoans and actinistians. Despite the apparent lack of more representative Paleozoic ichthyofaunas in Brazil, the available material that ranges from Lower Devonian to early Permian from Brazil bears important taxa that could address valuable taxonomic and biogeographic informations.

  6. Comparison of different methods for activation analysis of geological and pedological samples: Reactor and epithermal neutron activation, relative and monostandard method

    International Nuclear Information System (INIS)

    Alian, A.; Sansoni, B.

    1980-04-01

    Using purely instrumental methods, a comparative study is presented on neutron activation analysis of rock and soil samples by whole reactor neutron spectrum and epithermal neutrons with both relative and monostandard procedures. The latter procedure used with epithermal neutron activation analysis of soil samples necessitated the use of the 'effective resonance integrals' which were determined experimentally. The incorporation of the #betta# factor, representing deviation of reactor epithermal neutron flux from 1/E law, is developed in the present work. The main criteria for the choice of one or more of the procedures studied for a given purpose are also indicated. Analysis of 15 trace elements, Ca and Fe in the standard Japanese granite JG-1 using monostandard epithermal neutron activation gave results in good agreement with the average literature values. (orig./RB) [de

  7. Depth-dose evaluation for lung and pancreas cancer treatment by BNCT using an epithermal neutron beam

    International Nuclear Information System (INIS)

    Matsumoto, Tetsuo; Fukushima, Yuji

    2000-01-01

    The depth-dose distributions were evaluated for possible treatment of both lung and pancreas cancers using an epithermal neutron beam. The MCNP calculations showed that physical dose in tumors were 6 and 7 Gy/h, respectively, for lung and pancreas, attaining an epithermal neutron flux of 5x10 8 ncm -2 s -1 . The boron concentrations were assumed at 100 ppm and 30 ppm, respectively, for lung and pancreas tumors and normal tissues contains 1/10 tumor concentrations. The dose ratios of tumor to normal tissue were 2.5 and 2.4, respectively, for lung and pancreas. The dose evaluation suggests that BNCT could be applied for both lung and pancreas cancer treatment. (author)

  8. Design of a permanent Cd-shielded epithermal neutron irradiation site in the Syrian Miniature Neutron Source Reactor

    International Nuclear Information System (INIS)

    Khattab, K.; Haddad, Kh.; Haj-Hassan, H.

    2008-01-01

    A Cd-shield (cylindrical shell 1 mm in thickness, 34 mm in diameter and 180 mm in length) was used to design a permanent epithermal neutron irradiation site for epithermal neutron activation analysis (ENAA) in the Syrian Miniature Neutron Source Reactor (MNSR). This site was achieved by shielding the surface of the aluminum tube of one of the outer irradiation sites. The calculated depression ratio of thermal neutron flux was 1/10. Homogeneity of the neutron flux in the first outer irradiation site has been found numerically using the WIMSD4 and CITATION codes and experimentally by irradiating five short copper wires using the outer irradiation capsule. Good agreement was obtained between the calculated and the measured results of the neutron flux distributions. (author)

  9. Design of a permanent Cd-shielded epithermal neutron irradiation site in the Syrian Miniature Neutron Source Reactor

    International Nuclear Information System (INIS)

    Khattab, K.; Haddad, Kh.; Haj-Hassan, H.

    2009-01-01

    A Cd-shield (cylindrical shell 1 mm in thickness, 34 mm in diameter and 180 mm in length) was used to design a permanent epithermal neutron irradiation site for epithermal neutron activation analysis (ENAA) in the Syrian Miniature Neutron Source Reactor (MNSR). This site was achieved by shielding the surface of the aluminum tube of one of the outer irradiation sites. The calculated depression ratio of thermal neutron flux was 1/10. Homogeneity of the neutron flux in the first outer irradiation site has been found numerically using the WIMSD4 and CITATION codes and experimentally by irradiating five short copper wires using the outer irradiation capsule. Good agreement was obtained between the calculated and the measured results of the neutron flux distributions. (author)

  10. SPLET - A program for calculating the space-lethargy distribution of epithermal neutrons in a reactor lattice cell

    International Nuclear Information System (INIS)

    Matausek, M.V.; Zmijatevic, I.

    1981-01-01

    A procedure to solve the space-single-lethargy dependent transport equation for epithermal neutrons in a cylindricised multi-region reactor lattice cell has been developed and proposed in the earlier papers. Here, the computational algorithm is comprised and the computing program SPLET, which calculates the space-lethargy distribution of the spherical harmonics neutron flux moments, as well as the related integral quantities as reaction rates and resonance integrals, is described. (author)

  11. Hubungan Kondisi Geologi terhadap Alterasi dan Mineralisasi Endapan Epithermal Daerah Sualan, Kecamatan Talegong, Kabupaten Garut, Provinsi Jawa Barat

    OpenAIRE

    Kumala Sari, Paramitha Eka

    2013-01-01

    In exploration process of epithermal deposit, it is important to understand alteration and mineralization. The presence of alteration and mineralization zones help development of ore mineral exploration. Hydrothermal alteration is change of the chemistry, physics, mineralogy and origin textures of rocks as it interacts with the hydrothermal fluid. Alteration and mineralization zones has characteristics and certain minerals in each area.The research purposes are to determine the geological ...

  12. Elemental Mass Balance of the Hydrothermal Alteration Associated with the Baturappe Epithermal Silver-Base Metal Prospect, South Sulawesi, Indonesia

    OpenAIRE

    Nur, Irzal; Idrus, Arifudin; Pramumijoyo, Subagyo; Harijoko, Agung; Watanabe, Koichiro; Imai, Akira; Jaya, Asri; Irfan, Ulva Ria; Sufriadin

    2012-01-01

    Abstract The Baturappe prospect situated in southernmost part of Sulawesi island, Indonesia, is a hydrothermal mineralization district which is characterized by occurrences of epithermal silver-base metal mineralizations. The mineralizations hosted in basaltic-andesitic volcanic rocks of the late Middle-Miocene Baturappe Volcanics. This paper discusses a recent study of relationships between alteration mineralogy and whole-rock geochemistry, which focused on elemental mass balance calculat...

  13. Application of enzyme leach soil analysis for epithermal gold exploration in the Andes of Ecuador

    Energy Technology Data Exchange (ETDEWEB)

    Williams, T.M.; Gunn, A.G. [British Geological Survey, Nottingham (United Kingdom)

    2002-07-01

    Enzyme Leach (EL) soil surveys were undertaken over known epithermal Au mineralisation at El Mozo and Llano Largo, Azuay, Ecuador to assess the utility of the technique for identifying such deposits in the Ecuadorian Andes. The results indicate the development of both apical- and oxidation-type EL anomalies over auriferous structures at the two sites, the former systematically incorporating Au, and the latter Cl and Br. The spectrum of elements responsive to mineralisation at El Mozo (Cl, Br, I, La, Ce, Nd, Cu, Pb, Au, As, Sb, Ag, Zr, Sr) was found to be considerably greater than at Llano Largo (Cl, Br, Au, As, Sb, Ag, Zn), probably reflecting the contrasting high- and low-sulphidation assemblages of the two prospects. Ratios of EL versus aqua-regia extractable trace element concentrations ranged from 1: < 100 for Mn to 1: >400 for chalcophile elements such as Pb, Sb, As, Bi and Ag. Strong correlations between the concentrations of several analytes (including Mn, Sr, Cu, Co, As) extracted by the two procedures indicate, however, that EL datasets are extensively influenced by bulk matrix composition. Spatial variations of EL extractable Mn were found to exert no major influence on apical or oxidation suite anomaly patterns at El Mozo. However, Mn-normalisation of halogen data for Llano Largo elucidated otherwise obscure oxidation features, potentially related to Au mineralisation. Ratios between elements subject to apical enrichment and those of the oxidation suite (e.g. Cl/Au and Bi/Br) were found to highlight known Au targets with improved clarity. The formation mechanism of the recorded Au anomalies is uncertain, but may involve physical enrichment of Au in the soil during pedogenesis with subsequent in-situ formation of (EL soluble) Au halide complexes. The strength of such apical features is, in part, probably a function of the minimal depths to mineralisation which characterise El Mozo and Llano Largo. Oxidation halos formed by volatile non-metallic elements

  14. The alanine detector in BNCT dosimetry: dose response in thermal and epithermal neutron fields.

    Science.gov (United States)

    Schmitz, T; Bassler, N; Blaickner, M; Ziegner, M; Hsiao, M C; Liu, Y H; Koivunoro, H; Auterinen, I; Serén, T; Kotiluoto, P; Palmans, H; Sharpe, P; Langguth, P; Hampel, G

    2015-01-01

    The response of alanine solid state dosimeters to ionizing radiation strongly depends on particle type and energy. Due to nuclear interactions, neutron fields usually also consist of secondary particles such as photons and protons of diverse energies. Various experiments have been carried out in three different neutron beams to explore the alanine dose response behavior and to validate model predictions. Additionally, application in medical neutron fields for boron neutron capture therapy is discussed. Alanine detectors have been irradiated in the thermal neutron field of the research reactor TRIGA Mainz, Germany, in five experimental conditions, generating different secondary particle spectra. Further irradiations have been made in the epithermal neutron beams at the research reactors FiR 1 in Helsinki, Finland, and Tsing Hua open pool reactor in HsinChu, Taiwan ROC. Readout has been performed with electron spin resonance spectrometry with reference to an absorbed dose standard in a (60)Co gamma ray beam. Absorbed doses and dose components have been calculated using the Monte Carlo codes fluka and mcnp. The relative effectiveness (RE), linking absorbed dose and detector response, has been calculated using the Hansen & Olsen alanine response model. The measured dose response of the alanine detector in the different experiments has been evaluated and compared to model predictions. Therefore, a relative effectiveness has been calculated for each dose component, accounting for its dependence on particle type and energy. Agreement within 5% between model and measurement has been achieved for most irradiated detectors. Significant differences have been observed in response behavior between thermal and epithermal neutron fields, especially regarding dose composition and depth dose curves. The calculated dose components could be verified with the experimental results in the different primary and secondary particle fields. The alanine detector can be used without

  15. Fluid Inclusion Study of The Tumpangpitu High Sulfidation Epithermal Gold Deposit in Banyuwangi District, East Java, Indonesia

    Directory of Open Access Journals (Sweden)

    Yu Yu Myaing

    2018-03-01

    Full Text Available The Tumpangpitu high sulfidation (HS epithermal gold deposit is located in the south coast of East Java, Banyuwangi District, East Java Province, Indonesia. This area lies within the central portion of the Cenozoic Sunda‐Banda magmatic arc which trends southeast from northern Sumatra to west Java then eastward through east Java, Bali, Lombok, Sumbawa and terminating at Banda sea. The geology of the Tumpangpitu is predominantly occupied by Late Oligocene to Middle Miocene low-K calc-alkaline to alkaline andesitic volcanic rocks and interbedded with volcaniclastic rock sequences, which are associated with low-K intermediate intrusions. The mineralization style at the Tumpangpitu area is composed of a high‐sulfidation (HS epithermal gold-copper system which is typically associated with concealed gold-rich porphyry copper system. The HS epithermal mineralization is hosted by volcanic and volcaniclastic rocks in this research area. The mineralization domains are divided into Zone A, Zone B and Zone C which are situated along NW-SE-trending silica ledges zones. The HS epithermal mineralization is texturally occurs as vuggy replacements mineralization as well as stockworks, disseminated forms, fractures and veins. Fluid inclusion study was conducted for 6 quartz vein samples which petrographically entrapped fluid inclusions. Homogenization temperature (Th and melting temperature (Tm can microthermometrically be determined by fluid inclusion analysis. The average homogenization temperature (Th of the fluid inclusions gives 180˚C to 342˚C and melting temperature are from -0.1 ˚C to -1.4˚C. Tm corresponds to the salinities ranging from 0.1 to 4.5 wt% NaCl equivalent. The paleodepth of ore formation can be estimated from the salinity of fluid. Since the deposit was not formed at boiling condition, the minimum paleodepth of ore (quartz samples taken from both shallow level (53.35 m and deep level (135.15 m is determined at 650m and 1,220 m

  16. Epithermal neutron activation analysis of CR(VI)-reducer basalt-inhabiting bacteria

    International Nuclear Information System (INIS)

    Tsibakhashvili, N.Ya.; Kalabegishvili, T.L.; Murusidze, I.G.; Mosulishvili, L.M.; Frontas'eva, M.V.; Kirkesali, E.I.; Aksenova, N.G.; Holman, H.Y.

    2005-01-01

    Epithermal neutron activation analysis (ENAA) has been applied to studying elemental composition of Cr(VI)-reducer bacteria isolated from polluted basalts from the Republic of Georgia. Cr(VI)-reducing ability of the bacteria was examined by electron spin resonance (ESR) demonstrating that the bacteria differ in the rates of Cr(VI) reduction. A well-pronounced correlation between the ability of the bacteria to accumulate Cr(VI) and their ability to reduce Cr(V) to Cr(III) observed in our experiments is discussed. Elemental analysis of these bacteria also revealed that basalt-inhabiting bacteria are distinguished by relative contents of essential elements such as K, Na, Mg, Fe, Mn, Zn, and Co. A high rate of Cr(III) formation correlates with a high concentration of Co in the bacterium. ENAA detected some similarity in the elemental composition of the bacteria. The relatively high contents of Fe detected in the bacteria (140-340 μg/g of dry weight) indicate bacterial adaptation to the environmental conditions typical of the basalts. The concentrations of at least 12-19 different elements ranging from major- to ultratrace ones were determined in each type of bacteria simultaneously. The range of concentrations spans over 8 orders of magnitude

  17. Geochemical evaluation of mining wastes (tailings or tails) of epithermal ore mineralization, Hidalgo, Mexico

    International Nuclear Information System (INIS)

    Moreno, Raul; Monroy, Marcos G.; Castaneda, E. Pedro

    2009-01-01

    The mining district Pachuca-Real del Monte is located to the center-east of Mexico, between the geographical coordinates 20 degrees celsius 07 minutes 30 seconds north latitude and 98 degrees celsius 44 minutes 00 seconds of length west. The residues are derived from an epithermal mineralization. Concentrations of Pb and the Mn are significant. The mineralization is consisted of pyrite, limonite-goethite-hematite, sphalerite, galena, and chalcopyrite associated with quartz, calcite and silicates. X-rays diffraction patterns have determined quartz as the mayor mineral phase, with minor gypsum, calcite, alunite, and pyrite. The statistical analysis has presented the frequent association of Zn-Cd. The microanalysis with the scanning electronic microscope and electronic microprobe have showed the neoformation of the pyrite and the oxidation and precipitate of sulfides. The tests NOM-053 and EPA-1312 have showed that the Cd, Ni, Ag, Pb Mn, Zn, and As do not exceed the LMP. Only the Pb has been superior to the LMP in the first test. These residues might be classified as dangerous with regard to the Pb. (author) [es

  18. Adaptability of Brayton cycle conversion systems to fast, epithermal and thermal spectrum space nuclear reactors

    International Nuclear Information System (INIS)

    Tilliette, Z.P.

    1988-01-01

    The two French Government Agencies C.N.E.S. (Centre National d'Etudes Spatiales) and C.E.A. (Commissariat a l'Energie Atomique) are carrying out joint preliminary studies on space nuclear power systems for future ARIANE 5 launch vehicle applications. The Brayton cycle is the reference conversion system, whether the heat source is a liquid metal-cooled (NaK, Na or Li) reactor or a gas-cooled direct cycle concept. The search for an adequate utilization of this energy conversion means has prompted additional evaluations featuring the definition of satisfactory cycle conditions for these various kinds of reactor concepts. In addition to firstly studied fast and epithermal spectrum ones, thermal spectrum reactors can offer an opportunity of bringing out some distinctive features of the Brayton cycle, in particular for the temperature conditioning of the efficient metal hydrides (ZrH, Li/sub 7/H) moderators. One of the purposes of the paper is to confirm the potential of long lifetime ZrH moderated reactors associated with a gas cycle and to assess the thermodynamical consequences for both Nak(Na)-cooled or gas-cooled nuclear heat sources. This investigation is complemented by the definition of appropriate reactor arrangements which could be presented on a further occasion

  19. Determination of Uranium and Thorium in Brazilian coals by epithermal neutron activation analysis

    International Nuclear Information System (INIS)

    Bernedo, L.F.B.

    1981-08-01

    An experimental technique for the determination of uranium and thorium in coal by epithermal neutron activation was developed and systemized. Seventeen different coal samples, six copper monitors for neutron flux corrections and three NBS standard coal samples were irradiated together in a cadmium cylinder. Uranium and thorium were determined by measuring the 239 N sub(p) and 233 P sub(a) activities respectively, being both produced in (n,γ) reactions and subsequent β - decay. The 239 N sub(p) was measured by counting the 106.4 KeV γ-ray in a LEPS detector and the 233 P sub(a) by counting the 311.8 KeV γ-ray, but in a Ge(Li) detector. A 4096 multichannel analizer and a PDP-11 computer complemented the basic measuring equipment. An average precision of 3% was obtained in the analysis of seventeen coal samples coming from different strata and heights of Charqueadas and Morungava mines in Rio Grande do Sul State. The sensitivity of the method is around 100 ppb. This technique will allow determinations of up to twenty elements, besides uranium and thorium, and it can be applied in routine analysis. (Author) [pt

  20. Determination of uranium in tree bark samples by epithermal neutron activation analysis

    International Nuclear Information System (INIS)

    Lima, Nicole Pereira de; Saiki, Mitiko

    2017-01-01

    In this study uranium (U) concentrations were determined in certified reference materials (CRMs) and in tree bark samples collected in 'Cidade Universitaria Armando de Salles Oliveira' (CUASO) USP, Sao Paulo, SP, Brazil). The barks were collected from different species namely Poincianella pluviosa and Tipuana tipu. These bark samples were cleaned, dried, grated and milled for the analyses by epithermal neutron activation analysis method (ENAA). This method consists on irradiating samples and U standard in IEAR1 nuclear reactor with thermal neutron flux of 1:9 x 10 12 n cm -2 s -1 during 40 to 60 seconds depending on the samples matrices. The samples and standard were measured by gamma ray spectroscopy. U was identified by the peak of 74.66 keV of 239 U with half life of 23.47 minutes. Concentration of U was calculated by comparative method. For analytical quality control of U results, certified reference materials were analysed. Results obtained for CRMs presented good precision and accuracy, with |Z score| <= 0.39. Uranium concentrations in tree barks varied from 83.1 to 627.6 ng g - 1 and the relative standard deviations of these results ranged from 1.8 to 10%. (author)

  1. Investigations on the comparator technique used in epithermal neutron activation analysis

    International Nuclear Information System (INIS)

    Bereznai, T.; Bodizs, D.; Keoemley, G.

    1977-01-01

    The possible extension of the comparator technique of reactor neutron activation analysis into the field of epithermal neutron activation has been investigated. Ruthenium was used for multi-isotopic comparator. Experiments show that conversion of the so-called reference k-factors - determined by irradiation with reactor neutrons - into ksup(epi)-factors usable at activation under cadmium filter, can be evaluated with fair accuracy. Sources and extent of errors and their contribution to the final error of analysis are discussed. For equal irradiation and counting times advantage of ENAA for several elements is obvious: the much lower background activity permitted the sample to be measured closer to the detector, under better geometry conditions, consequently, permitting several elements to be determined quantitatively. The number of elements determined and the sensitivity of the method are much dependent on the experimental conditions, especially on the composition of the sample, on the PHIsub(e) value, the irradiation time and the efficiency of the Ge(Li) detector. (T.G.)

  2. YAP scintillators for resonant detection of epithermal neutrons at pulsed neutron sources

    International Nuclear Information System (INIS)

    Tardocchi, M.; Gorini, G.; Pietropaolo, A.; Andreani, C.; Senesi, R.; Rhodes, N.; Schooneveld, E. M.

    2004-01-01

    Recent studies indicate the resonance detector (RD) technique as an interesting approach for neutron spectroscopy in the electron volt energy region. This work summarizes the results of a series of experiments where RD consisting of YAlO 3 (YAP) scintillators were used to detect scattered neutrons with energy in the range 1-200 eV. The response of YAP scintillators to radiative capture γ emission from a 238 U analyzer foil was characterized in a series of experiments performed on the VESUVIO spectrometer at the ISIS pulsed neutron source. In these experiments a biparametric data acquisition allowed the simultaneous measurements of both neutron time-of-flight and γ pulse height (energy) spectra. The analysis of the γ pulse height and neutron time of flight spectra permitted to identify and distinguish the signal and background components. These measurements showed that a significant improvement in the signal-to-background ratio can be achieved by setting a lower level discrimination on the pulse height at about 600 keV equivalent photon energy. Present results strongly indicate YAP scintillators as the ideal candidate for neutron scattering studies with epithermal neutrons at both very low (<5 deg.) and intermediate scattering angles

  3. Determination of uranium in tree bark samples by epithermal neutron activation analysis

    Energy Technology Data Exchange (ETDEWEB)

    Lima, Nicole Pereira de; Saiki, Mitiko, E-mail: mitiko@ipen.com [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2017-11-01

    In this study uranium (U) concentrations were determined in certified reference materials (CRMs) and in tree bark samples collected in 'Cidade Universitaria Armando de Salles Oliveira' (CUASO) USP, Sao Paulo, SP, Brazil). The barks were collected from different species namely Poincianella pluviosa and Tipuana tipu. These bark samples were cleaned, dried, grated and milled for the analyses by epithermal neutron activation analysis method (ENAA). This method consists on irradiating samples and U standard in IEAR1 nuclear reactor with thermal neutron flux of 1:9 x 10{sup 12} n cm{sup -2} s{sup -1} during 40 to 60 seconds depending on the samples matrices. The samples and standard were measured by gamma ray spectroscopy. U was identified by the peak of 74.66 keV of {sup 239}U with half life of 23.47 minutes. Concentration of U was calculated by comparative method. For analytical quality control of U results, certified reference materials were analysed. Results obtained for CRMs presented good precision and accuracy, with |Z score| <= 0.39. Uranium concentrations in tree barks varied from 83.1 to 627.6 ng g{sup -} {sup 1} and the relative standard deviations of these results ranged from 1.8 to 10%. (author)

  4. Marine Gradients of Halogens in Moss Studied by Epithermal Neutron Activation Analysis

    CERN Document Server

    Frontasyeva, M V

    2002-01-01

    Epithermal neutron activation analysis is known to be a powerful technique for the simultaneous study of chlorine, bromine and iodine in environmental samples. In this paper it is shown to be useful to elucidate marine gradients of these elements. Examples are from a transect study in northern Norway where samples of the feather moss Hylocomium splendens were collected at distances 0-300 km from the coastline. All three elements decreased exponentially as a function of distance from the ocean in the moss samples, strongly indicating that atmospheric supply from the marine environment is the predominant source of these elements to the terrestrial ecosystem. These results are compared with similar data for surface soils along the same gradients. Comparison is also made with previous data for halogens in moss in Norway obtained by conventional NAA and covering similar transects in other geographical regions. The Cl/Br and Br/I ratios in moss showed a regular change distance from the ocean in all transects, and h...

  5. Epithermal Neutron Activation Analysis (ENAA) of Cr(VI)-reducer Basalt-inhabiting Bacteria

    CERN Document Server

    Tsibakhashvili, N Ya; Kirkesali, E I; Aksenova, N G; Kalabegishvili, T L; Murusidze, I G; Mosulishvili, L M; Holman, H Y N

    2005-01-01

    Epithermal neutron activation analysis (ENAA) has been applied to studying elemental composition of Cr(VI)-reducer bacteria isolated from polluted basalts from the Republic of Georgia. Cr(VI)-reducing ability of the bacteria was examined by electron spin resonance (ESR) demonstrating that the bacteria differ in the rates of Cr(VI) reduction. A well-pronounced correlation between the ability of the bacteria to accumulate Cr(V) and their ability to reduce Cr(V) to Cr(III) observed in our experiments is discussed. Elemental analysis of these bacteria also revealed that basalt-inhabiting bacteria are distinguished by relative contents of essential elements such as K, Na, Mg, Fe, Mn, Zn, and Co. A high rate of Cr(III) formation correlates with a high concentration of Co in the bacterium. ENAA detected some similarity in the elemental composition of the bacteria. The relatively high contents of Fe detected in the bacteria (140-340 $\\mu $g/g of dry weight) indicate bacterial adaptation to the environmental condition...

  6. An epithermal neutron source for BNCT based on an ESQ-accelerator

    International Nuclear Information System (INIS)

    Ludewigt, B.A.; Chu, W.T.; Donahue, R.J.; Kwan, J.; Phillips, T.L.; Reginato, L.L.; Wells, R.P.

    1997-07-01

    An accelerator-based BNCT facility is under development at the Lawrence Berkeley National Laboratory. Neutrons will be produced via the 7 Li(p,n) reaction at proton energies of about 2.5 MeV with subsequent moderation and filtering for shaping epithermal neutron beams for BNCT. Moderator, filter, and shielding assemblies have been modeled using MCNP. Head-phantom dose distributions have been calculated using the treatment planning software BNCT RTPE. The simulation studies have shown that a proton beam current of ∼ 20 mA is required to deliver high quality brain treatments in about 40 minutes. The results also indicate that significantly higher doses can be delivered to deep-seated tumors in comparison to the Brookhaven Medical Research Reactor beam. An electrostatic quadrupole (ESQ) accelerator is ideally suited to provide the high beam currents desired. A novel power supply utilizing the air-coupled transformer concept is under development. It will enable the ESQ-accelerator to deliver proton beam currents exceeding 50 mA. A lithium target has been designed which consists of a thin layer of lithium on an aluminum backing. Closely spaced, narrow coolant passages cut into the aluminum allow the removal of a 50kW heat-load by convective water cooling. The system under development is suitable for hospital installation and has the potential for providing neutron beams superior to reactor sources

  7. Benchmarking of epithermal methods in the lattice-physics code EPRI-CELL

    International Nuclear Information System (INIS)

    Williams, M.L.; Wright, R.Q.; Barhen, J.; Rothenstein, W.; Toney, B.

    1982-01-01

    The epithermal cross section shielding methods used in the lattice physics code EPRI-CELL (E-C) have been extensively studied to determine its major approximations and to examine the sensitivity of computed results to these approximations. The study has resulted in several improvements in the original methodology. These include: treatment of the external moderator source with intermediate resonance (IR) theory, development of a new Dancoff factor expression to account for clad interactions, development of a new method for treating resonance interference, and application of a generalized least squares method to compute best-estimate values for the Bell factor and group-dependent IR parameters. The modified E-C code with its new ENDF/B-V cross section library is tested for several numerical benchmark problems. Integral parameters computed by EC are compared with those obtained with point-cross section Monte Carlo calculations, and E-C fine group cross sections are benchmarked against point-cross section descrete ordinates calculations. It is found that the code modifications improve agreement between E-C and the more sophisticated methods. E-C shows excellent agreement on the integral parameters and usually agrees within a few percent on fine-group, shielded cross sections

  8. Geochemical evidence for Paleozoic crustal growth and tectonic conversion in the Northern Beishan Orogenic Belt, southern Central Asian Orogenic Belt

    Science.gov (United States)

    Yuan, Yu; Zong, Keqing; He, Zhenyu; Klemd, Reiner; Jiang, Hongying; Zhang, Wen; Liu, Yongsheng; Hu, Zhaochu; Zhang, Zeming

    2018-03-01

    The Beishan Orogenic Belt is located in the central southernmost part of the Central Asian Orogenic Belt (CAOB), which plays a key role in understanding the formation and evolution of the CAOB. Granitoids are the documents of crustal and tectonic evolution in orogenic belts. However, little is known regarding the petrogenesis and geodynamic setting of the widely distributed Paleozoic granitoids in the Northern Beishan Orogenic Belt (NBOB). The present study reveals significant differences concerning the petrogenesis and tectonic setting of early and late Paleozoic granitoids from the NBOB. The early Paleozoic granitoids from the 446-430 Ma Hongliuxia granite complex of the Mazongshan unit and the 466-428 Ma Shibanjing complex of the Hanshan unit show classic I-type granite affinities as revealed by the relative enrichment of LILEs and LREEs, pronounced depletions of Nb, Ta and Ti and the abundant presence of hornblende. Furthermore, they are characterized by strongly variable zircon εHf(t) values between - 16.7 and + 12.8 and evolved plagioclase Sr isotopic compositions of 0.7145-0.7253, indicating the involvement of both juvenile and ancient continental crust in the magma source. Thus, we propose that the early Paleozoic granitoids in the NBOB were generated in a subduction-related continental arc setting. In contrast, the late Paleozoic 330-281 Ma granitoids from the Shuangjingzi complex of the Hanshan unit exhibit positive zircon εHf(t) values between + 5.8 and + 13.2 and relatively depleted plagioclase Sr isotopic compositions of 0.7037-0.7072, indicating that they were mainly formed by remelting of juvenile crust. Thus, an intra-plate extensional setting is proposed to have occurred during formation of the late Paleozoic granitoids. Therefore, between the early and late Paleozoic, the magma sources of the NBOB granitoids converted from the reworking of both juvenile and ancient crusts during a subduction-induced compressional setting to the remelting of

  9. Origin and tectonic evolution of early Paleozoic arc terranes abutting the northern margin of North China Craton

    Science.gov (United States)

    Zhou, Hao; Pei, Fu-Ping; Zhang, Ying; Zhou, Zhong-Biao; Xu, Wen-Liang; Wang, Zhi-Wei; Cao, Hua-Hua; Yang, Chuan

    2017-12-01

    The origin and tectonic evolution of the early Paleozoic arc terranes abutting the northern margin of the North China Craton (NCC) are widely debated. This paper presents detrital zircon U-Pb and Hf isotopic data of early Paleozoic strata in the Zhangjiatun arc terrane of central Jilin Province, northeast (NE) China, and compares them with the Bainaimiao and Jiangyu arc terranes abutting the northern margin of the NCC. Detrital zircons from early Paleozoic strata in three arc terranes exhibit comparable age groupings of 539-430, 1250-577, and 2800-1600 Ma. The Paleoproterozoic to Neoarchean ages and Hf isotopic composition of the detrital zircons imply the existence of the Precambrian fragments beneath the arc terranes. Given the evidences from geology, igneous rocks, and detrital zircons, we proposed that the early Paleozoic arc terranes abutting the northern margin of the NCC are a united arc terrane including the exotic Precambrian fragments, and these fragments shared a common evolutionary history from Neoproterozoic to early-middle Paleozoic.

  10. Reworked crustal of early Paleozoic WuYi Orogen revealed by receiver function data

    Science.gov (United States)

    Wei, Y.; Duan, Y.; Tian, X.; Zhao, Y.

    2017-12-01

    Intraplate orogenic belt, which occurs at the rigid and undeformable plate interiors, is a distinct new type of orogen rather than an interplate or plate marginal orogenic belt, whose deformation occurs exclusively at plate margins. Therefore, intraplate orogenic belts are the most obvious exception to the plate-tectonic paradigm, they are uncommon in Earth's history. The early Paleozoic Wuyi orogen in South China is one of the few examples of intraplate orogen, and is a key to understanding the process of intraplate orogenesis and global early Paleozoic geodynamics. In this study, we select teleseismic records from 45 mobile linear seismic stations deployed in Wuyi Mountain and 58 permanent stations setting in Jiangxi and Fujian provinces, from January 2011 to December 2012, and calculate the crustal thickness and average crustal Vp/Vs ratio using the H-κ stacking method. The main results include the following: 1) the crustal average Poission's ratio shows an increase tendency from land to sea, the interior of Wuyi orogen belt with an low ration less than 0.23, and the coastline with high ration which is up to 0.28, which indicate a very heterogeneous crustal structure and composition in Wuyi orogen and coast belt. 2) the crustal thickness ranges 28-34 km and shows a tendency of thinning from inland to coast in the region of SE China margin, which maight mean the eastern Eurasia lithospheric is extension and thinning induced by the subducted paleo-Pacific slab. To conclusion, we assume that Wuyi orogen experienced upper crustal thickening, lower crust and lithosphere delamination during the early Paleozoic orogeny, and lithosphere extension in Mesozoic. This research is founded by the Natural Science Foundation of China (41174052 and 41604048).

  11. Archean inheritance in zircon from late Paleozoic granites from the Avalon zone of southeastern New England: an African connection

    Science.gov (United States)

    Zartman, R.E.; Don, Hermes O.

    1987-01-01

    In southeastern New England the Narragansett Pier Granite locally intrudes Carboniferous metasedimentary rocks of the Narragansett basin, and yields a monazite UPb Permian emplacement age of 273 ?? 2 Ma. Zircon from the Narragansett Pier Granite contains a minor but detectable amount of an older, inherited component, and shows modern loss of lead. Zircon from the late-stage, aplitic Westerly Granite exhibits a more pronounced lead inheritance -permitting the inherited component to be identified as Late Archean. Such old relict zircon has not been previously recognized in Proterozoic to Paleozoic igneous rocks in New England, and may be restricted to late Paleozoic rocks of the Avalon zone. We suggest that the Archean crustal component reflects an African connection, in which old Archean crust was underplated to the Avalon zone microplate in the late Paleozoic during collision of Gondwanaland with Avalonia. ?? 1987.

  12. The features of the isotope composition of carbon in the Paleozoic and Mesozoic oils of Western Siberia

    Energy Technology Data Exchange (ETDEWEB)

    Golyshev, S.I.; Lebedena, L.V.

    1984-01-01

    The isotope composition of the carbon in the oils from the Mesozoic and Paleozoic deposits is measured. The variations in the isotope composition of carbon for the Paleozoic oils is between 27.5 and 30.8 percent, while for the oils from the lower Jurassic and Triassic levels it is between 27.7 and 31.2 percent and for the upper Jurassic oils it is between 30.1 and 34.5 percent. The dependence of the isotope composition of the carbon in the oils on the type of original organic matter and its metamorphosis conditions during lithogenesis is analyzed. A softening in the isotope composition of the carbon in the oils from the oceanic deposits relative to continental deposits is found, together with a genetic individualism of the oils from the Paleozoic deposits and their difference from the oils in the Mesozoic deposits.

  13. Measurement of the neutron flux distributions, epithermal index, Westcott thermal neutron flux in the irradiation capsules of hydraulic conveyer (Hyd) and pneumatic tubes (Pn) facilities of the KUR

    International Nuclear Information System (INIS)

    Chatani, Hiroshi

    2001-05-01

    The reactions of Au(n, γ) 198 Au and Ti(n, p) 47 or 48 Sc were used for the measurements of the thermal and epithermal (thermal + epithermal) and the fast neutron flux distributions, respectively. In the case of Hyd (Hydraulic conveyer), the thermal + epithermal and fast neutron flux distributions in the horizontal direction in the capsule are especially flat; the distortion of the fluxes are 0.6% and 5.4%, respectively. However, these neutron fluxes in the vertical direction are low at the top and high at the bottom of the capsule. These differences between the top and bottom are 14% for both distributions. On the other hand, in polyethylene capsules of Pn-1, 2, 3 (Pneumatic tubes Nos. 1, 2, 3), in contrast with Hyd, these neutron flux distributions in the horizontal direction have gradients of 8 - 18% per 2.5 cm diameter, and those on the vertical axis have a distortion of approximately 5%. The strength of the epithermal dE/E component relative to the neutron density including both thermal and epithermal neutrons, i.e., the epithermal index, for the hydraulic conveyer (Hyd) and pneumatic tube No.2 (Pn-2), in which the irradiation experiments can be achieved, are determined by the multiple foil activation method using the reactions of Au(n, γ) 198 Au and Co(n, γ) 60(m+g) Co. The epithermal index observed in an aluminum capsule of Hyd is 0.034-0.04, and the Westcott thermal neutron flux is 1.2x10 14 cm -2 sec -1 at approximately 1 cm above the bottom. The epithermal index in a Pn-2 polyethylene capsule was measured by not only the multiple foil activation method but also the Cd-ratio method in which the Au(n, γ) 198 Au reaction in a cadmium cover is also used. The epithermal index is 0.045 - 0.055, and the thermal neutron flux is 1.8x10 13 cm -2 sec -1 . (J.P.N.)

  14. A new paleozoic Symmoriiformes (Chondrichthyes from the late Carboniferous of Kansas (USA and cladistic analysis of early chondrichthyans.

    Directory of Open Access Journals (Sweden)

    Alan Pradel

    Full Text Available BACKGROUND: The relationships of cartilaginous fishes are discussed in the light of well preserved three-dimensional Paleozoic specimens. There is no consensus to date on the interrelationship of Paleozoic chondrichthyans, although three main phylogenetic hypotheses exist in the current literature: 1. the Paleozoic shark-like chondrichthyans, such as the Symmoriiformes, are grouped along with the modern sharks (neoselachians into a clade which is sister group of holocephalans; 2. the Symmoriiformes are related to holocephalans, whereas the other Paleozoic shark-like chondrichthyans are related to neoselachians; 3. many Paleozoic shark-like chondrichthyans, such as the Symmoriiformes, are stem chondrichthyans, whereas stem and crown holocephalans are sister group to the stem and crown neoselachians in a crown-chondrichthyan clade. This third hypothesis was proposed recently, based mainly on dental characters. METHODOLOGY/PRINCIPAL FINDINGS: On the basis of two well preserved chondrichthyan neurocrania from the Late Carboniferous of Kansas, USA, we describe here a new species of Symmoriiformes, Kawichthys moodiei gen. et sp. nov., which was investigated by means of computerized X-ray synchrotron microtomography. We present a new phylogenetic analysis based on neurocranial characters, which supports the third hypothesis and corroborates the hypothesis that crown-group chondrichthyans (Holocephali+Neoselachii form a tightly-knit group within the chondrichthyan total group, by providing additional, non dental characters. CONCLUSIONS/SIGNIFICANCE: Our results highlight the importance of new well preserved Paleozoic fossils and new techniques of observation, and suggest that a new look at the synapomorphies of the crown-group chondrichthyans would be worthwhile in terms of understanding the adaptive significance of phylogenetically important characters.

  15. ESR-dosimetry in thermal and epithermal neutron fields for application in boron neutron capture therapy

    Energy Technology Data Exchange (ETDEWEB)

    Schmitz, Tobias

    2016-01-22

    Dosimetry is essential for every form of radiotherapy. In Boron Neutron Capture Therapy (BNCT) mixed neutron and gamma fields have to be considered. Dose is deposited in different neutron interactions with elements in the penetrated tissue and by gamma particles, which are always part of a neutron field. The therapeutic dose in BNCT is deposited by densely ionising particles, originating from the fragmentation of the isotope boron-10 after capture of a thermal neutron. Despite being investigated for decades, dosimetry in neutron beams or fields for BNCT remains complex, due to the variety in type and energy of the secondary particles. Today usually ionisation chambers combined with metal foils are used. The applied techniques require extensive effort and are time consuming, while the resulting uncertainties remain high. Consequently, the investigation of more effective techniques or alternative dosimeters is an important field of research. In this work the possibilities of ESR-dosimeters in those fields have been investigated. Certain materials, such as alanine, generate stable radicals upon irradiation. Using Electron Spin Resonance (ESR) spectrometry the amount of radicals, which is proportional to absorbed dose, can be quantified. Different ESR detector materials have been irradiated in the thermal neutron field of the research reactor TRIGA research reactor in Mainz, Germany, with five setups, generating different secondary particle spectra. Further irradiations have been conducted in two epithermal neutron beams. The detector response, however, strongly depends on the dose depositing particle type and energy. It is hence necessary to accompany measurements by computational modelling and simulation. In this work the Monte Carlo code FLUKA was used to calculate absorbed doses and dose components. The relative effectiveness (RE), linking absorbed dose and detector response, has been calculated using amorphous track models. For the simulation, detailed models of

  16. Gneiss Macuira: tectonic evolution of Paleozoic metamorphic rocks of the Alta Guajira, Colombia

    International Nuclear Information System (INIS)

    Lopez I; A Julian; Zuluaga C; A, Carlos

    2012-01-01

    The Macuira Gneiss is a Paleozoic metamorphic unit that outcrops in the Simarua, Jarara and Macuira ranges, Alta Guajira. It is composed by a lithologies metamorphosed under amphibolite facies P-T conditions and consist of amphibolitic and quartz feldspathic gneisses, amphibolites, schists, pegmatites, calc-silicated rocks and marbles, with migmatization evidences in gneisses and amphibolites. Five foliations (S1-5) and three folding events (F1-3) were identified and interpreted as product of two metamorphic events, developed in a progressive barrovian metamorphic gradient of intermediate pressure with intermediate P-T ratio, interpreted as product of continental collision tectonics. This unit is important in understanding of the tectonic evolution of the Alta Guajira and Caribbean because it records different deformational phases pre-, syn- and post-migmatitic, that could be related with different tectonic episodes: the first associated with the collision between Laurasia and Gondwana (Alleghanian Orogeny - Late Paleozoic), and the second related with the Caribbean Plate evolution (Andean Orogeny - Meso-Cenozoic).

  17. The Cottage Grove fault system (Illinois Basin): Late Paleozoic transpression along a Precambrian crustal boundary

    Science.gov (United States)

    Duchek, A.B.; McBride, J.H.; Nelson, W.J.; Leetaru, H.E.

    2004-01-01

    The Cottage Grove fault system in southern Illinois has long been interpreted as an intracratonic dextral strike-slip fault system. We investigated its structural geometry and kinematics in detail using (1) outcrop data, (2) extensive exposures in underground coal mines, (3) abundant borehole data, and (4) a network of industry seismic reflection profiles, including data reprocessed by us. Structural contour mapping delineates distinct monoclines, broad anticlines, and synclines that express Paleozoic-age deformation associated with strike slip along the fault system. As shown on seismic reflection profiles, prominent near-vertical faults that cut the entire Paleozoic section and basement-cover contact branch upward into outward-splaying, high-angle reverse faults. The master fault, sinuous along strike, is characterized along its length by an elongate anticline, ???3 km wide, that parallels the southern side of the master fault. These features signify that the overall kinematic regime was transpressional. Due to the absence of suitable piercing points, the amount of slip cannot be measured, but is constrained at less than 300 m near the ground surface. The Cottage Grove fault system apparently follows a Precambrian terrane boundary, as suggested by magnetic intensity data, the distribution of ultramafic igneous intrusions, and patterns of earthquake activity. The fault system was primarily active during the Alleghanian orogeny of Late Pennsylvanian and Early Permian time, when ultramatic igneous magma intruded along en echelon tensional fractures. ?? 2004 Geological Society of America.

  18. Improved Dose Targeting for a Clinical Epithermal Neutron Capture Beam Using Optional 6Li Filtration

    International Nuclear Information System (INIS)

    Binns, Peter J.; Riley, Kent J.; Ostrovsky, Yakov; Gao Wei; Albritton, J. Raymond; Kiger, W.S.; Harling, Otto K.

    2007-01-01

    Purpose: The aim of this study was to construct a 6 Li filter and to improve penetration of thermal neutrons produced by the fission converter-based epithermal neutron beam (FCB) for brain irradiation during boron neutron capture therapy (BNCT). Methods and Materials: Design of the 6 Li filter was evaluated using Monte Carlo simulations of the existing beam line and radiation transport through an ellipsoidal water phantom. Changes in beam performance were determined using three figures of merit: (1) advantage depth (AD), the depth at which the total biologically weighted dose to tumor equals the maximum weighted dose to normal tissue; (2) advantage ratio (AR), the ratio of the integral tumor dose to that of normal tissue averaged from the surface to the AD; and (3) advantage depth dose rate (ADDR), the therapeutic dose rate at the AD. Dosimetry performed with the new filter installed provided calibration data for treatment planning. Past treatment plans were recalculated to illustrate the clinical potential of the filter. Results: The 8-mm-thick Li filter is more effective for smaller field sizes, increasing the AD from 9.3 to 9.9 cm, leaving the AR unchanged at 5.7 but decreasing the ADDR from 114 to 55 cGy min -1 for the 12 cm diameter aperture. Using the filter increases the minimum deliverable dose to deep seated tumors by up to 9% for the same maximum dose to normal tissue. Conclusions: Optional 6 Li filtration provides an incremental improvement in clinical beam performance of the FCB that could help to establish a therapeutic window in the future treatment of deep-seated tumors

  19. Precious metal-bearing epithermal deposits in western Patagonia (NE Lago Fontana region), Argentina

    Science.gov (United States)

    Lanfranchini, Mabel Elena; Etcheverry, Ricardo Oscar; de Barrio, Raúl Ernesto; Recio Hernández, Clemente

    2013-04-01

    Precious metal-bearing quartz veins occur at the northeastern sector of the Lago Fontana region in southwestern Argentina, within the context of the Andean continental magmatic arc environment. The deposits and their associated alteration zones are spatially related to a Cretaceous calc-alkaline magmatism represented by silicic dikes and hypabyssal intrusions, and hosted by a Late Jurassic to Cretaceous volcano-sedimentary sequence. The veins and related veinlets crop out discontinuously, in general terms in a NW-SE belt. The primary vein mineral assemblage is composed mostly of pyrite ± galena ± chalcopyrite > hematite ± arsenopyrite in silica gangue minerals. Chemical analyses of grab samples from selected quartz veins show as much as 5.7 ppm Au and 224 ppm Ag, as well as elevated Pb, Cu, and Zn. Hydrothermal fluids caused an innermost silicification and adularia-sericite alteration assemblage, and an external propylitic halo. Sulfur isotope values measured for sulfides (δSS from -1.90 to +1.56‰), and oxygen and hydrogen isotopes measured on quartz crystals and extracted primary fluid inclusion waters (δOO = -2.85 to +5.40‰; δDO = -106.0 to -103.4‰) indicate that mineralization probably formed from magmatic fluids, which were mixed with meteoric waters. Also, fluid inclusion data from quartz veins point out that these fluids had low salinity (1.7-4.2 wt% NaCl equiv.), and temperatures of homogenization between 180 and 325 °C. Mineralogical, petrographic and geochemical features for mineralized surface exposures indicate a typical adularia-sericite, low sulfidation epithermal system in the Lago Fontana area that represents a promising target for further exploration programs.

  20. Development of new instrumentation for epithermal neutron scattering at very low angles

    International Nuclear Information System (INIS)

    Tardocchi, M.; Pietropaolo, A.; Andreani, C.; Gorini, G.; Perelli-Cippo, E.; Rhodes, N.J.; Schooneveld, E.M.; Senesi, R.

    2004-01-01

    New perspectives for epithermal neutron spectroscopy are opened up by the recent developments of Resonance Detectors (RD) for inverse geometry time-of-flight spectrometers at pulsed neutron sources. The RD is based on the combination of an analyser foil used as neutron-to-gamma converter and a suitable photon detector. Here, we report on the state of the RD which is based on a YAP scintillator viewing a natural uranium analyser foil. The response of the YAP detector to the radiative capture γ emission from the uranium analyser foil has been characterized with a bi-parametric measurement of a reference Pb sample, which allowed simultaneous measurements of both neutron time-of-flight and γ pulse height (energy) spectra. The analysis of the γ pulse height and neutron time-of-flight spectra permitted to identify the signal and background components. These measurements showed that a significant improvement in the signal-to-background ratio can be achieved by setting a lower level discrimination on the photon energy at about 600keV. The first application of RD is the Very Low Angle Detector Bank (VLAD) which is planned to be installed in the next three years as an upgrade of the VESUVIO spectrometer, at the ISIS pulsed neutron source. VLAD will extend the (q,ω) kinematical to low wave vector transfers (q10A-1) coupled to high-energy transfers (-bar ω>1eV), which is still unexplored by neutron scattering experiments. The first measurements obtained on an ice sample with a VLAD prototype consisting of four RD units are presented here

  1. The mineral products of boiling in the Golden Cross epithermal deposit

    International Nuclear Information System (INIS)

    Simmons, S.F.; Mauk, J.L.; Simpson, M.P.

    2000-01-01

    The Golden Cross low sulfidation epithermal deposit shows a number of features that are directly or indirectly related to boiling hydroythermal fluids. Occurrences of lattice calcite and their quartz pseudomorph equivalents in veins, and occurrences of adularia in veins and in the surrounding altered rocks in the vicinity of ore, are direct evidence of deposition in the presence of boiling hydrothermal fluids. Loss of carbon dioxide causes calcite deposition (platy variety) near the level of first boiling, while adularia deposits due to the attendant pH increase and cooling. Indirect evidence of boiling includes crustiform-colloform quartz banding, late massive calcite veins, and clay-carbonate alteration in the shallow and peripheral parts of the ore zone. The colloform quartz banding strongly resembles the banding in amorophous silica deposits found in geothermal pipes. This implies that fluids ascending the Empire vein structure were saturated in amorphous silica. If so, then they must have undergone phase separation, which initiated at considerable depth (e.g. > or =1000 m) and very hot temperatures (e.g. > or =300 degrees C). On the basis of stable isotope data, late massive veins appear to have deposited from CO 2 -rich steam-heated waters. Calcite deposited along heating paths as these waters descended into the upflow zone during late stage collapse of the hydrothermal plume. In active systems, such steam heated waters form by deep boiling. The high CO 2 contents of these waters promote hydrolytic alteration and the formation of clay-carbonate alteration. (author). 37 refs., 4 figs

  2. First evidence of epithermal gold occurrences in the SE Afar Rift, Republic of Djibouti

    Science.gov (United States)

    Moussa, N.; Fouquet, Y.; Le Gall, B.; Caminiti, A. M.; Rolet, J.; Bohn, M.; Etoubleau, J.; Delacourt, C.; Jalludin, M.

    2012-06-01

    The geology of the Republic of Djibouti, in the SE Afar Triangle, is characterized by intense tectonic and bimodal volcanic activity that began as early as 25-30 Ma. Each magmatic event was accompanied by hydrothermal activity. Mineralization generally occurs as gold-silver bearing chalcedony veins and is associated with felsic volcanism. Eighty samples from mineralized hydrothermal chalcedony, quartz ± carbonate veins and breccias were studied from ten sites representing four major volcanic events that range in age from early Miocene to the present. The most recent veins are controlled by fractures at the edges of grabens established during the last 4 Myr. Gold in excess of 200 ppb is present in 30% of the samples, with values up to 16 ppm. Mineralogical compositions allowed us to identify different types of mineralization corresponding to different depths in the hydrothermal system: (1) surface and subsurface mineralization characterized by carbonate chimneys, gypsum, silica cap and quartz ± carbonate veins that are depleted in metals and Au; (2) shallow banded chalcedony ± adularia veins related to boiling that contain up to 16 ppm Au, occurring as native gold and electrum with pyrite, and tetradymite; (3) quartz veins with sulfides, and (4) epidote alteration in the deepest hydrothermal zones. Samples in which pyrite is enriched in As tend to have a high Au content. The association with bimodal volcanism, the occurrence of adularia and the native Au and electrum in banded chalcedony veins are typical of epithermal systems and confirm that this type of mineralization can occur in a young intracontinental rift system.

  3. Development of new instrumentation for epithermal neutron scattering at very low angles

    Energy Technology Data Exchange (ETDEWEB)

    Tardocchi, M. [INFM, UdR Milano-Bicocca and Dipartimento di Fisica ' G.Occhialini' , Universita degli Studi di Milano-Bicocca, Pizza Della Scienza 3, Milan 20126 (Italy)]. E-mail: marco.tardocchi@mib.infn.it; Pietropaolo, A. [Dipartimento di Fisica, Universita degli Studi di Roma Tor Vergata and INFM, UdR Roma Tor Vergata, Rome (Italy); Andreani, C. [Dipartimento di Fisica, Universita degli Studi di Roma Tor Vergata and INFM, UdR Roma Tor Vergata, Rome (Italy); Gorini, G. [INFM, UdR Milano-Bicocca and Dipartimento di Fisica ' G.Occhialini' , Universita degli Studi di Milano-Bicocca, Pizza Della Scienza 3, Milan 20126 (Italy); Perelli-Cippo, E. [INFM, UdR Milano-Bicocca and Dipartimento di Fisica ' G.Occhialini' , Universita degli Studi di Milano-Bicocca, Pizza Della Scienza 3, Milan 20126 (Italy); Rhodes, N.J. [Isis Facility, Rutherford Appleton Laboratory, Chilton, Didcot (United Kingdom); Schooneveld, E.M. [Isis Facility, Rutherford Appleton Laboratory, Chilton, Didcot (United Kingdom); Senesi, R. [Dipartimento di Fisica, Universita degli Studi di Roma Tor Vergata and INFM, UdR Roma Tor Vergata, Rome (Italy)

    2004-12-11

    New perspectives for epithermal neutron spectroscopy are opened up by the recent developments of Resonance Detectors (RD) for inverse geometry time-of-flight spectrometers at pulsed neutron sources. The RD is based on the combination of an analyser foil used as neutron-to-gamma converter and a suitable photon detector. Here, we report on the state of the RD which is based on a YAP scintillator viewing a natural uranium analyser foil. The response of the YAP detector to the radiative capture {gamma} emission from the uranium analyser foil has been characterized with a bi-parametric measurement of a reference Pb sample, which allowed simultaneous measurements of both neutron time-of-flight and {gamma} pulse height (energy) spectra. The analysis of the {gamma} pulse height and neutron time-of-flight spectra permitted to identify the signal and background components. These measurements showed that a significant improvement in the signal-to-background ratio can be achieved by setting a lower level discrimination on the photon energy at about 600keV. The first application of RD is the Very Low Angle Detector Bank (VLAD) which is planned to be installed in the next three years as an upgrade of the VESUVIO spectrometer, at the ISIS pulsed neutron source. VLAD will extend the (q,{omega}) kinematical to low wave vector transfers (q10A-1) coupled to high-energy transfers (-bar {omega}>1eV), which is still unexplored by neutron scattering experiments. The first measurements obtained on an ice sample with a VLAD prototype consisting of four RD units are presented here.

  4. The volcanic rocks construction of the late paleozoic era and uranium mineralization in Beishan area of Gansu province

    International Nuclear Information System (INIS)

    An Zhengchang; Luo Xiaoqiang

    2010-01-01

    Late Paleozoic volcanic rocks in Beishan area are the favorable constructions of hydrothermal type and volcanic type deposit. From the distribution of volcanic rocks, the volcanic compositions, the volcanic facies, volcanic eruption method and rhythm, chemical and trace elements compositions, and so on, it discusses the characteristics of the Late Devonian volcanic construction in this area and its relationship with uranium mineralization, analyzes the role of volcanic ore-control mechanism, and summarizes uranium ore forming regularity of volcanic construction in Late Paleozoic. (authors)

  5. Multipurpose epithermal neutron beam on new research station at MARIA research reactor in Swierk-Poland

    Energy Technology Data Exchange (ETDEWEB)

    Gryzinski, M.A.; Maciak, M. [National Centre for Nuclear Research, Andrzeja Soltana 7, 05-400 Otwock-Swierk (Poland)

    2015-07-01

    MARIA reactor is an open-pool research reactor what gives the chance to install uranium fission converter on the periphery of the core. It could be installed far enough not to induce reactivity of the core but close enough to produce high flux of fast neutrons. Special design of the converter is now under construction. It is planned to set the research stand based on such uranium converter in the near future: in 2015 MARIA reactor infrastructure should be ready (preparation started in 2013), in 2016 the neutron beam starts and in 2017 opening the stand for material and biological research or for medical training concerning BNCT. Unused for many years, horizontal channel number H2 at MARIA research rector in Poland, is going to be prepared as a part of unique stand. The characteristics of the neutron beam will be significant advantage of the facility. High flux of neutrons at the level of 2x10{sup 9} cm{sup -2}s{sup -1} will be obtainable by uranium neutron converter located 90 cm far from the reactor core fuel elements (still inside reactor core basket between so called core reflectors). Due to reaction of core neutrons with converter U{sub 3}Si{sub 2} material it will produce high flux of fast neutrons. After conversion neutrons will be collimated and moderated in the channel by special set of filters and moderators. At the end of H2 channel i.e. at the entrance to the research room neutron energy will be in the epithermal energy range with neutron intensity at least at the level required for BNCT (2x10{sup 9} cm{sup -2}s{sup -1}). For other purposes density of the neutron flux could be smaller. The possibility to change type and amount of installed filters/moderators which enables getting different properties of the beam (neutron energy spectrum, neutron-gamma ratio and beam profile and shape) is taken into account. H2 channel is located in separate room which is adjacent to two other empty rooms under the preparation for research laboratories (200 m2). It is

  6. Compton suppression method and epithermal NAA in the determination of nutrients and heavy metals in Nigerian food and beverages

    Energy Technology Data Exchange (ETDEWEB)

    Ahmed, Y.A., E-mail: yaahmed1@gmail.co [Reactor Engineering Section, Centre for Energy Research and Training, Ahmadu Bello University, Zaria (Nigeria); Nuclear Engineering Teaching Laboratory, University of Texas at Austin, Austin, TX 78758 (United States); Landsberger, S.; O' Kelly, D.J.; Braisted, J. [Nuclear Engineering Teaching Laboratory, University of Texas at Austin, Austin, TX 78758 (United States); Gabdo, H. [Physics Department, Federal College of Education, Yola (Nigeria); Ewa, I.O.B.; Umar, I.M.; Funtua, I.I. [Reactor Engineering Section, Centre for Energy Research and Training, Ahmadu Bello University, Zaria (Nigeria)

    2010-10-15

    We used in this study Compton suppression method and epithermal neutron activation analysis to determine the concentration of nutrients and heavy metals in Nigerian food and beverages. The work was performed at the University of Texas TRIGA Reactor by short, medium, and long irradiation protocols, using thermal flux of 1.4x10{sup 12} n cm{sup -2} s{sup -1} and epithermal flux of 1.4x10{sup 11} n cm{sup -2} s{sup -1}. Application of Compton suppression method has reduced interferences from Compton scattered photons thereby allowing easy evaluation of Na, Cl, Ca, Cu, Mn, Mg, Co, Cr, Rb, Fe, and Se. The epithermal NAA method has enabled determination of Cd, As, Ba, Sr, Br, I, and V with little turn-around time. Quality Control and Quality Assurance of the method was tested by analyzing four Standard Reference Materials (non-fat powdered milk, apple leaves, citrus leaves, and peach leaves) obtained from National Institute for Standards and Technology. Our results show that sorghum, millet, and maize have high values of Zn, Mn, Fe, low values of Cd, As, and Se. Powdered milks, rice, beans, and soybeans were found to have moderate amounts of all the elements. Tobacco recorded high content of Cd, Mn, and As, whereas tea, tsobo leaves, Baobab leaves, and okro seed have more As values than others. However, biscuits, macaroni, spaghetti, and noodles show lower concentrations of all the elements. The distribution of these nutrients and heavy metals in these food and beverages shows the need to fortify biscuits and pastas with micro and macro-nutrients and reduce the use of tobacco, tea, tsobo leaves, Baobab leaves, and Okro seed to avoid intake of heavy elements.

  7. Compton suppression method and epithermal NAA in the determination of nutrients and heavy metals in Nigerian food and beverages.

    Science.gov (United States)

    Ahmed, Y A; Landsberger, S; O'Kelly, D J; Braisted, J; Gabdo, H; Ewa, I O B; Umar, I M; Funtua, I I

    2010-10-01

    We used in this study Compton suppression method and epithermal neutron activation analysis to determine the concentration of nutrients and heavy metals in Nigerian food and beverages. The work was performed at the University of Texas TRIGA Reactor by short, medium, and long irradiation protocols, using thermal flux of 1.4x10(12)n cm(-2)s(-1) and epithermal flux of 1.4x10(11)n cm(-2)s(-1). Application of Compton suppression method has reduced interferences from Compton scattered photons thereby allowing easy evaluation of Na, Cl, Ca, Cu, Mn, Mg, Co, Cr, Rb, Fe, and Se. The epithermal NAA method has enabled determination of Cd, As, Ba, Sr, Br, I, and V with little turn-around time. Quality Control and Quality Assurance of the method was tested by analyzing four Standard Reference Materials (non-fat powdered milk, apple leaves, citrus leaves, and peach leaves) obtained from National Institute for Standards and Technology. Our results show that sorghum, millet, and maize have high values of Zn, Mn, Fe, low values of Cd, As, and Se. Powdered milks, rice, beans, and soybeans were found to have moderate amounts of all the elements. Tobacco recorded high content of Cd, Mn, and As, whereas tea, tsobo leaves, Baobab leaves, and okro seed have more As values than others. However, biscuits, macaroni, spaghetti, and noodles show lower concentrations of all the elements. The distribution of these nutrients and heavy metals in these food and beverages shows the need to fortify biscuits and pastas with micro and macro-nutrients and reduce the use of tobacco, tea, tsobo leaves, Baobab leaves, and Okro seed to avoid intake of heavy elements. Copyright 2010 Elsevier Ltd. All rights reserved.

  8. Utilization of boron irradiation filters in reactor neutron activation via epithermal (n,γ) and fast neutron reactions

    International Nuclear Information System (INIS)

    Chisela, F.

    1986-01-01

    The technique of instrumental neutron activation analysis based on irradiation with reactor epithermal and fast neutrons has been described and evaluated. Important characteristics of boron neutron absorbers used to remove thermal neutrons from the reactor neutron spectrum have been examined and compared with those of cadmium. Three boron compound shields, have been designed and constructed at the BER II 5MW reactor for use in epithermal neutron activation analysis of biological materials. The major advantages offered by these filters in this application include the flexibility of varying the filter thickness, the low radioactivity induced in the filters during irradiation, ease of fabrication and the relatively low cost of the filter materials. The radiation heating due to the 10 B(n,α) 7 Li-reaction has been experimentally investigated for the filters used and the results obtained confirm the necessity for efficient cooling of these filters during irradiation. Three irradiation facilities have been characterized with respect to the neutron flux density and the flux spatial distribution. An experiment has been designed and carried out to compensate the flux inhomogeneity in two irradiation positions of the DBV facility caused by the reactor geometry. Several biological samples including well characterized reference materials have been analysed after epithermal activation and the results compared with those obtained with the classical thermal neutron activation method. Improved sensitivity of determination has been found for elements with high resonance integral to thermal neutron cross section ratios (RI/σ 0 ). The range of elements that can be determined instrumentally is extended and the time scale of analysis is considerably reduced. (orig.) [de

  9. Compton suppression method and epithermal NAA in the determination of nutrients and heavy metals in Nigerian food and beverages

    International Nuclear Information System (INIS)

    Ahmed, Y.A.; Landsberger, S.; O'Kelly, D.J.; Braisted, J.; Gabdo, H.; Ewa, I.O.B.; Umar, I.M.; Funtua, I.I.

    2010-01-01

    We used in this study Compton suppression method and epithermal neutron activation analysis to determine the concentration of nutrients and heavy metals in Nigerian food and beverages. The work was performed at the University of Texas TRIGA Reactor by short, medium, and long irradiation protocols, using thermal flux of 1.4x10 12 n cm -2 s -1 and epithermal flux of 1.4x10 11 n cm -2 s -1 . Application of Compton suppression method has reduced interferences from Compton scattered photons thereby allowing easy evaluation of Na, Cl, Ca, Cu, Mn, Mg, Co, Cr, Rb, Fe, and Se. The epithermal NAA method has enabled determination of Cd, As, Ba, Sr, Br, I, and V with little turn-around time. Quality Control and Quality Assurance of the method was tested by analyzing four Standard Reference Materials (non-fat powdered milk, apple leaves, citrus leaves, and peach leaves) obtained from National Institute for Standards and Technology. Our results show that sorghum, millet, and maize have high values of Zn, Mn, Fe, low values of Cd, As, and Se. Powdered milks, rice, beans, and soybeans were found to have moderate amounts of all the elements. Tobacco recorded high content of Cd, Mn, and As, whereas tea, tsobo leaves, Baobab leaves, and okro seed have more As values than others. However, biscuits, macaroni, spaghetti, and noodles show lower concentrations of all the elements. The distribution of these nutrients and heavy metals in these food and beverages shows the need to fortify biscuits and pastas with micro and macro-nutrients and reduce the use of tobacco, tea, tsobo leaves, Baobab leaves, and Okro seed to avoid intake of heavy elements.

  10. Epithermal neutron activation analysis of Spirulina platensis biomass, of the C-phycocianin and of DNA extracted from it

    International Nuclear Information System (INIS)

    Mosulishvili, L.M.; Belokobyl'skij, A.I.; Kirkesali, E.I.; Khizanishvili, A.I.; Frontas'eva, M.V.; Pomyakushina, E.V.

    2002-01-01

    The epithermal neutron activation analysis (ENAA) was used for study of the biomass of Spirulina platensis. The background levels of concentration of 27 macro-, micro- and trace elements ranging from 10 -3 up to 10 4 ppm were determined. It was found that the biomass of Spirulina does not contain toxic elements above the tolerance levels and can be utilized as a matrix of pharmaceuticals based on it. The concentrations of basic elements in C-phycocianin and DNA extracted from Spirulina platensis were determined by ENAA. A comparison of the element content of a whole Spirulina biomass with that of a refined C-phycocianin preparation was made

  11. Application of Epithermal Neutron Activation Analysis to Investigate Accumulation and Adsorption of Mercury by Spirulina platensis Biomass

    CERN Document Server

    Mosulishvili, L M; Khizanishvili, A I; Frontasyeva, M V; Kirkesali, E I; Aksenova, N G

    2004-01-01

    Epithermal neutron activation analysis was used to study interaction of blue-green alga Spirulina platensis with toxic metal mercury. Various concentrations of Hg(II) were added to cell cultures in a nutrient medium. The dynamics of accumulation of Hg was investigated over several days in relation to Spirulina biomass growth. The process of Hg adsorption by Spirulina biomass was studied in short-time experiments. The isotherm of adsorption was carried out in Freindlich coordinates. Natural Spirulina biomass has potential to be used in the remediation of sewage waters at Hg concentrations \\sim 100 {\\mu}g/l.

  12. Boron neutron capture therapy (BNCT) for glioblastoma multiforme using the epithermal neutron beam at the Brookhaven Medical Research Reactor

    International Nuclear Information System (INIS)

    Capala, J.; Diaz, A.Z.; Chadha, M.

    1997-01-01

    The abstract describes evaluation of boron neutron capture therapy (BNCT) for two groups of glioblastoma multiforme patients. From September 1994 to February 1996 15 patients have been treated. In September 1997 another 34 patients were examined. Authors determined a safe starting dose for BNCT using epithermal neutrons and BPA-F. They have also evaluated adverse effects of BNCT at this starting dose. Therapeutic effectiveness of this starting dose has been evaluated. No significant side effects from BPA-F infusion or BNCT treatment were observed in normal brains

  13. Application of epithermal neutron activation analysis to investigate accumulation and adsorption of mercury by Spirulina platensis biomass

    International Nuclear Information System (INIS)

    Mosulishvili, L.M.; Belokobyl'skij, A.I.; Khizanishvili, A.I.; Frontas'eva, M.V.; Kirkesali, E.I.; Aksenova, N.G.

    2004-01-01

    Epithermal neutron activation analysis was used to study interaction of blue-green alga Spirulina platensis with toxic metal mercury. Various concentrations of Hg(II) were added to cell cultures in a nutrient medium. The dynamics of accumulation of Hg was investigated over several days in relation to Spirulina biomass growth. The process of Hg adsorption by Spirulina biomass was studied in short-time experiments. The isotherm of adsorption was carried out in Freindlich coordinates. Natural Spirulina biomass has potential to be used in the remediation of sewage waters at Hg concentrations ∼100 μg/1

  14. Boron neutron capture therapy (BNCT) for glioblastoma multiforme using the epithermal neutron beam at the Brookhaven Medical Research Reactor

    Energy Technology Data Exchange (ETDEWEB)

    Capala, J. [Brookhaven National Lab., Upton, NY (United States); Diaz, A.Z.; Chadha, M. [Univ. Hospital, State Univ. of New York, NY (United States)] [and others

    1997-12-31

    The abstract describes evaluation of boron neutron capture therapy (BNCT) for two groups of glioblastoma multiforme patients. From September 1994 to February 1996 15 patients have been treated. In September 1997 another 34 patients were examined. Authors determined a safe starting dose for BNCT using epithermal neutrons and BPA-F. They have also evaluated adverse effects of BNCT at this starting dose. Therapeutic effectiveness of this starting dose has been evaluated. No significant side effects from BPA-F infusion or BNCT treatment were observed in normal brains.

  15. Study on the dose distribution of the mixed field with thermal and epi-thermal neutrons for neutron capture therapy

    International Nuclear Information System (INIS)

    Kobayashi, Tooru; Sakurai, Yoshinori; Kanda, Keiji

    1994-01-01

    Simulation calculations using DOT 3.5 were carried out in order to confirm the characteristics of depth-dependent dose distribution in water phantom dependent on incident neutron energy. The epithermal neutrons mixed to thermal neutron field is effective improving the thermal neutron depth-dose distribution for neutron capture therapy. A feasibility study on the neutron energy spectrum shifter was performed using ANISN-JR for the KUR Heavy Water Facility. The design of the neutron spectrum shifter is feasible, without reducing the performance as a thermal neutron irradiation field. (author)

  16. Epithermal Neutron Activation Analysis of Spirulina platensis Biomass, of the C-Phycocianin and of DNA Extracted from It

    CERN Document Server

    Mosulishvili, L M; Belokobylsky, A I; Kirkesali, E I; Khizanishvili, A I; Pomyakushina, E V

    2002-01-01

    The epithermal neutron activation analysis (ENAA) was used for study of the biomass of Spirulina platensis. The background levels of concentration 27 macro-, micro- and trace elements ranging from 10^{-3} up to 10^{4} ppm were determined. It was found that the biomass of spirulina does not contain toxic elements above the tolerance levels and can be utilized as a matrix of pharmaceuticals based on it. The concentrations of basic elements in C-phycocianin and DNA extracted from Spirulina platensis were determined by ENAA. A comparison of the element content of a whole spirulina biomass with that of a refined C-phycocianin preparation was made.

  17. Measurement of thermal, epithermal and fast neutron flux in the IEA-R1 reactor by the foil activation method

    International Nuclear Information System (INIS)

    Koskinas, M.F.

    1979-01-01

    Experimental and theoretical details of the foil activation method applied to neutrons flux measurements at the IEA-R1 reactor are presented. The thermal - and epithermal - neutron flux were determined form activation measurements of gold, cobalt and manganese foils; and for the fast neutron flux determination, aluminum, iron and nickel foils were used. The measurements of the activity induced in the metal foils were performed using a Ge-Li gamma spectrometry system. In each energy range of the reactor neutron spectrum, the agreement among the experimental flux values obtained using the three kind of materials, indicates the consistency of the theoretical approach and of the nuclear parameters selected. (Author) [pt

  18. Paleozoic oil/gas shale reservoirs in southern Tunisia: An overview

    Science.gov (United States)

    Soua, Mohamed

    2014-12-01

    During these last years, considerable attention has been given to unconventional oil and gas shale in northern Africa where the most productive Paleozoic basins are located (e.g. Berkine, Illizi, Kufra, Murzuk, Tindouf, Ahnet, Oued Mya, Mouydir, etc.). In most petroleum systems, which characterize these basins, the Silurian played the main role in hydrocarbon generation with two main 'hot' shale levels distributed in different locations (basins) and their deposition was restricted to the Rhuddanian (Lllandovery: early Silurian) and the Ludlow-Pridoli (late Silurian). A third major hot shale level had been identified in the Frasnian (Upper Devonian). Southern Tunisia is characterized by three main Paleozoic sedimentary basins, which are from North to South, the southern Chotts, Jeffara and Berkine Basin. They are separated by a major roughly E-W trending lower Paleozoic structural high, which encompass the Mehrez-Oued Hamous uplift to the West (Algeria) and the Nefusa uplift to the East (Libya), passing by the Touggourt-Talemzane-PGA-Bou Namcha (TTPB) structure close to southern Tunisia. The forementioned major source rocks in southern Tunisia are defined by hot shales with elevated Gamma ray values often exceeding 1400 API (in Hayatt-1 well), deposited in deep water environments during short lived (c. 2 Ma) periods of anoxia. In the course of this review, thickness, distribution and maturity maps have been established for each hot shale level using data for more than 70 wells located in both Tunisia and Algeria. Mineralogical modeling was achieved using Spectral Gamma Ray data (U, Th, K), SopectroLith logs (to acquire data for Fe, Si and Ti) and Elemental Capture Spectroscopy (ECS). The latter technique provided data for quartz, pyrite, carbonate, clay and Sulfur. In addition to this, the Gamma Ray (GR), Neutron Porosity (ΦN), deep Resistivity (Rt) and Bulk Density (ρb) logs were used to model bulk mineralogy and lithology. Biostratigraphic and complete

  19. Hydrocarbon preservation conditions in Mesozoic–Paleozoic marine strata in the South Yellow Sea Basin

    Directory of Open Access Journals (Sweden)

    Jie Liang

    2017-11-01

    Full Text Available In the South Yellow Sea Basin, Mesozoic–Paleozoic marine strata are generally well developed with large thickness, and they are characterized by multi-source and multi-stage hydrocarbon accumulation, providing a material basis for the formation of large-scale oil and gas fields. However, no substantial breakthrough has been made in this area. Based on previous research results, the complex tectonic pattern of this superimposed basin was formed by multi-stage tectonic movements and the favorable static conditions for hydrocarbon preservation were reworked or destroyed by later superimposition. Therefore, hydrocarbon preservation conditions are the key factors for restricting the breakthrough of marine oil and gas exploration in this area. In this paper, hydrocarbon preservation conditions of marine strata in the South Yellow Sea Basin were comprehensively analyzed from many aspects, such as tectonic movement, source conditions, caprock characteristics, magmatic activities, and hydrogeological and hydrogeochemical characteristics. It is indicated that the complex tectonic pattern of the South Yellow Sea Basin is resulted from tectonic events in multiple stages, and the development and evolution of regional source rocks are mainly controlled by two stages (i.e., the stable evolution stage of Mesozoic–Paleozoic marine basin and the Mesozoic–Cenozoic tectonic pattern transformation and basin formation stage, so the characteristics of differential oil and gas preservation are presented. Besides, better marine hydrocarbon preservation preconditions in this area are weaker tectonic reworking, development of high-quality thick source rocks, good vertical sealing capacity of caprocks, weaker magmatic activity and confined hydrogeological conditions. It is concluded that the Laoshan Uplift in the central part of the South Yellow Sea Basin is structurally stable with weaker faulting and magmatic activities, so it is better in oil and gas preservation

  20. The Measurement of Epithermal-to-Thermal U-238 Neutron Capture Rate (ρ28) in Aagesta Power Reactor Fuel

    International Nuclear Information System (INIS)

    Bernander, G.

    1967-09-01

    The epithermal-to-thermal neutron capture rate ratio ρ 28 in U-238 in Aagesta fuel has been measured by the chemical separation method. The method involves the isolation of Np-239 from uranium and fission products by reversed phase partition chromatography. Although somewhat elaborate, and in spite of difficulties with residual fission products, the method has yielded reasonably accurate results. Further development work on chemical procedures may lead to some improvement. A comparison with the coincidence method - electronic separation of activities - has not shown any large systematic differences between the two methods. The separation of the epithermal U-235 activation from the total has been achieved by means of the '1/v subtraction technique' using copper foils as the 1/v monitor. The complementary thermal column irradiations required have been performed in the research reactors TRIGA (Helsinki) and R1 (Stockholm). From the measured ρ 28 values the resonance escape probability (p) and the initial conversion ratio (ICR) may be calculated using cross-section data and other lattice parameters. Comparisons with theoretical values of ρ and ICR as calculated with the BURNUP lattice parameter code are favourable

  1. Simulation study of the photon quality correction factors of ionization chambers for FiR 1 epithermal neutron beam

    International Nuclear Information System (INIS)

    Koivunoro, H.; Uusi-Simola, J.; Savolainen, S.; Kotiluoto, P.; Auterinen, I.; Kosunen, A.

    2006-01-01

    At FiR 1 BNCT facility in Finland, neutron-insensitive Mg(Ar) ionization chambers are used for photon dose measurements in an epithermal neutron beam. Previously, photon sensitivity factors for the chamber for the measurements in a water phantom in FiR 1 beam have been determined experimentally from measurements in 60 Co gamma and in a 6 MV clinical accelerator photon beams. However, the response of the ionization chamber in a water phantom depends on energy spectrum and angle of the photons and the secondary electrons created inside the phantom and may differ depending on type of the irradiation source (accelerator vs. an epithermal neutron beam). Also, the experimental sensitivity factor does not take into account the possible perturbations in the photon production in phantom caused by the ionization chamber materials. Therefore, it is necessary to determine the photon quality correction factors (k Qγ ) for the Mg(Ar) chamber at the FiR 1 beam through computer simulations. In this study, the k Qγ factors have been determined for Mg(Ar) chamber from Monte Carlo calculations of absorbed photon dose at two depths in a water phantom using MCNP code. The k qγ factors obtained with this method are compared to the sensitivity factors determined with measurements in an accelerator photon beam and to the k Qγ factors published previously. (author)

  2. Paleostress and fluid-pressure regimes inferred from the orientations of Hishikari low sulfidation epithermal gold veins in southern Japan

    Science.gov (United States)

    Faye, Guillaume D.; Yamaji, Atsushi; Yonezu, Kotaro; Tindell, Thomas; Watanabe, Koichiro

    2018-05-01

    The orientation distribution of dilational fractures is affected by the state of stress around the fractures and by the pressure of the fluid that opened the fractures. Thus, the distribution can be inverted to determine not only the stress but also the pressure condition at the time of vein formation. However, epithermal ore veins that we observe today are the results of a great number of intermittent upwelling of overpressured fluids with different pressures. Here, we define driving pressure index (DPI) as the representative non-dimensionalized fluid pressure for the fluids. We collected the orientations of ∼1000 ore veins in the Hishikari gold mine, which were deposited at around 1 Ma, in southern Kyushu, Japan. It was found that the majority of the veins were deposited under an extensional stress with a NW-SE-trending σ3-axis and a northeasterly-inclined σ1-axis with relatively high stress ratio. The representative driving pressure ratio was ∼0.2. Data sets obtained at different depths in the mine indicated a positive correlation of representative driving pressure ratios with the depths. The correlation suggests repeated formation and break of pressure seals during the mineralization. Our compilation of the Pliocene-Quaternary stress regimes in southern Kyushu, including the result of the present study, suggests that epithermal gold mineralization was associated with distributed extensional deformations in southern Kyushu, and strain localization into an intra-arc rift seems to have terminated the mineralization.

  3. The Measurement of Epithermal-to-Thermal U-238 Neutron Capture Rate in Aagesta Power Reactor Fuel

    Energy Technology Data Exchange (ETDEWEB)

    Bernander, G

    1967-09-15

    The epithermal-to-thermal neutron capture rate ratio {rho}{sub 28} in U-238 in Aagesta fuel has been measured by the chemical separation method. The method involves the isolation of Np-239 from uranium and fission products by reversed phase partition chromatography. Although somewhat elaborate, and in spite of difficulties with residual fission products, the method has yielded reasonably accurate results. Further development work on chemical procedures may lead to some improvement. A comparison with the coincidence method - electronic separation of activities - has not shown any large systematic differences between the two methods. The separation of the epithermal U-235 activation from the total has been achieved by means of the '1/v subtraction technique' using copper foils as the 1/v monitor. The complementary thermal column irradiations required have been performed in the research reactors TRIGA (Helsinki) and R1 (Stockholm). From the measured {rho}{sub 28} values the resonance escape probability (p) and the initial conversion ratio (ICR) may be calculated using cross-section data and other lattice parameters. Comparisons with theoretical values of {rho} and ICR as calculated with the BURNUP lattice parameter code are favourable.

  4. Shielding design of a treatment room for an accelerator-based epithermal neutron irradiation facility for BNCT

    International Nuclear Information System (INIS)

    Evans, J.F.; Blue, T.E.

    1996-01-01

    Protecting the facility personnel and the general public from radiation exposure is a primary safety concern of an accelerator-based epithermal neutron irradiation facility. This work makes an attempt at answering the questions open-quotes How much?close quotes and open-quotes What kind?close quotes of shielding will meet the occupational limits of such a facility. Shielding effectiveness is compared for ordinary and barytes concretes in combination with and without borated polyethylene. A calculational model was developed of a treatment room, patient open-quotes scatterer,close quotes and the epithermal neutron beam. The Monte Carlo code, MCNP, was used to compute the total effective dose equivalent rates at specific points of interest outside of the treatment room. A conservative occupational effective dose rate limit of 0.01 mSv h -1 was the guideline for this study. Conservative Monte Carlo calculations show that constructing the treatment room walls with 1.5 m of ordinary concrete, 1.2 m of barytes concrete, 1.0 m of ordinary concrete preceded by 10 cm of 5% boron-polyethylene, or 0.8 m of barytes concrete preceded by 10 cm of 5% boron-polyethylene will adequately protect facility personnel. 20 refs., 8 figs., 2 tabs

  5. Development of the Very Low Angle Detector (VLAD) for detection of epithermal neutrons at low momentum transfers

    International Nuclear Information System (INIS)

    Tardocchi, M.; Andreani, C.; Cremonesi, O.; Gorini, G.; Perelli-Cippo, E.; Pietropaolo, A.; Rhodes, N.; Schooneveld, E.; Senesi, R.

    2006-01-01

    New perspectives for epithermal neutron spectroscopy are opened up by the recent development of new instrumentation for inverse geometry time of flight spectrometers at pulsed neutron sources. One example is the Very Low Angle Detector (VLAD) bank which will be installed as an upgrade of the VESUVIO neutron spectrometer, at the ISIS pulsed neutron source. VLAD is developed for detecting epithermal neutrons in the 1-100 eV energy range at very low scattering angles (l deg. - 5 deg.). VLAD will extend the kinematical region covered by today's neutron scattering experiments to the region of low wave vector transfers ( -1 ) and high energy transfers (>1 eV). Accessing such kinematical region will allow new experimental studies in condensed matter systems. The neutron detection is based on Resonance Detectors (RD), which consist of the combination of a resonance foil used as neutron-to-gamma converter and a photon detector. The results obtained with a prototype VLAD detector confirm the potential of this kind of experiments at scattering angles as low as 2 deg. - 5 deg. GEANT4 simulations are used to address issues, such as detector cross talk, which arise with the construction of compact RD arrays

  6. Comparison of Cadmium-Zinc-Telluride semiconductor and Yttrium-Aluminum-Perovskite scintillator as photon detectors for epithermal neutron spectroscopy

    International Nuclear Information System (INIS)

    Tardocchi, M.; Pietropaolo, A.; Andreani, C.; Gorini, G.; Imberti, S.; Perelli-Cippo, E.; Senesi, R.; Rhodes, N.; Schooneveld, E.M.

    2006-01-01

    The range of applications of epithermal neutron scattering experiments has been recently extended by the development of the Resonance Detector. In a Resonance Detector, resonant neutron absorption in an analyzer foil results in prompt emission of X- and γ-rays which are detected by a photon counter. Several combinations of analyzer foils and photon detectors have been studied and tested over the years and best results have been obtained with the combination of a natural uranium and (i) Cadmium-Zinc-Telluride (CZT) semiconductor (ii) Yttrium-Aluminum-Perovskite (YAP) scintillators. Here we compare the performance of the CZT semiconductor and YAP scintillator as Resonance Detector units. Two Resonance Detector prototypes made of natural uranium foil viewed by CZT and YAP were tested on the VESUVIO spectrometer at the ISIS spallation neutron source. The results show that both YAP and CZT can be used to detect epithermal neutrons in the energy range from 1 up to 66 eV. It was found that the signal-to-background ratio of the measurement can significantly be improved by raising the lower level discrimination threshold on the γ energy to about 600 keV. The advantages/disadvantages of the choice of a Resonance Detector based on YAP or CZT are discussed together with some potential applications

  7. Boron neutron capture therapy (BNCT). Recent aspect, a change from thermal neutron to epithermal neutron beam and a new protocol

    International Nuclear Information System (INIS)

    Nakagawa, Yoshinobu

    1999-01-01

    Since 1968, One-hundred seventy three patients with glioblastoma (n=81), anaplastic astrocytoma (n=44), low grade astrocytoma (n=16) or other types of tumor (n=32) were treated by boron-neutron capture therapy (BNCT) using a combination of thermal neutron and BSH in 5 reactors (HTR n=13, JRR-3 n=1, MuITR n=98, KUR n=28, JRR-2 n=33). Out of 101 patients with glioma treated by BNCT under the recent protocol, 33 (10 glioblastoma, 14 anaplastic astrocytoma, 9 low grade astrocytoma) patients lived or have lived longer than 3 years. Nine of these 33 lived or have lived longer than 10 years. According to the retrospective analysis, the important factors related to the clinical results were tumor dose radiation dose and maximum radiation dose in thermal brain cortex. The result was not satisfied as it was expected. Then, we decided to introduce mixed beams which contain thermal neutron and epithermal neutron beams. KUR was reconstructed in 1996 and developed to be available to use mixed beams. Following the shutdown of the JRR-2, JRR-4 was renewed for medical use in 1998. Both reactors have capacity to yield thermal neutron beam, epithermal neutron beam and mixed beams. The development of the neutron source lead us to make a new protocol. (author)

  8. The genesis of the slab window-related Arzular low-sulfidation epithermal gold mineralization (eastern Pontides, NE Turkey

    Directory of Open Access Journals (Sweden)

    Enver Akaryalı

    2013-07-01

    Full Text Available The Arzular mineralization is one of the best examples of epithermal gold deposits in the eastern Pontides orogenic belt. The mineralization is hosted by the subduction-related basaltic andesites and is mainly controlled by E–W and NE–SW trending fracture zones. The main ore minerals are galena, sphalerite, pyrite, chalcopyrite, tetrahedrite and gold. Homogenization temperatures of fluid inclusions are between 130 and 295 °C for quartz and between 90 and 133 °C for sphalerite. Sulphur isotope values obtained from pyrite, galena and sphalerite vary between −1.2‰ and 3‰, indicating that sulphur belongs to magmatic origin and was derived from the Lutetian non-adakitic granitic intrusions in the region. Oxygen isotope values are between 15.0‰ and 16.7‰, and hydrogen isotope values are between −87‰ and −91‰. The sulphur isotope thermometer yielded temperatures in the range of 244–291 °C for the ore formation. Our results support the hypothesis that the Arzular mineralization is a low-sulfidation epithermal gold deposit associated with non-adakitic subduction-related granitic magmas that were generated by slab window-related processes in a south-dipping subduction zone during the Lutetian.

  9. Early Permian intrusions in the Paleozoic sediments of the Eastern North Sea area

    DEFF Research Database (Denmark)

    Clausen, O.R.; Andresen, Katrine Juul; Rasmussen, Jens Andreas

    in the Northern Permian Basin which in the eastern North Sea is separated from the Southern Permian Basin by the Ringkøbing-Fyn High. The Permian basins were initiated during thermal subsidence following a late Carboniferous- early Permian rifting phase associated with extensive igneous activity recorded across...... the entire North Sea Basin. The easternmost intrusions and extrusions have been associated to the “Skagerrak-Centered Large Igneous Province” that has an early Permian age of c. 297 Ma. Compared to the Southern Permian Basin which historically has been intensely investigated because of the known presence...... of hydrocarbons within the Paleozoic sediments, the Northern Permian Basin has gained much less interest outside the hydrocarbon producing Mesozoic graben systems. This is mainly due to an apparent lack of potential source rocks. A major E-W striking northward dipping fault system characterizes the study area...

  10. Tectonic contact beetwen Paleozoic and Triassic rocks south of Podolševa (Slovenia

    Directory of Open Access Journals (Sweden)

    Bogomir Celarc

    2002-12-01

    Full Text Available Tectonic contact between Paleozoic and Triassic rocks south of Podolševa, which passes prominent cliffs over the left bank of Savinja river (Klemenča peč, Jamnikova peč, Golerjeva peč, Strevčeva peč and Huda peč, is on the basis of the new mapping a steep fault, dipping to the north. In the last phase, the fault was dextral strike – slip active, before was probably reverse, and can represent accompanying structure of Periadriatic lineament. It was under transpresive tectonic regime and complies with model of positive flower structure.We named it Podol{evski prelom (Podol{eva fault.

  11. Electrical structures in the northwest margin of the Junggar basin: Implications for its late Paleozoic geodynamics

    Science.gov (United States)

    Zhang, Sheng; Xu, Yixian; Jiang, Li; Yang, Bo; Liu, Ying; Griffin, W. L.; Luo, Yong; Huang, Rong; Zhou, Yong; Zhang, Liangliang

    2017-10-01

    Recent geological, geochemical and geophysical data have inclined to support the presence of a remnant Paleozoic oceanic lithosphere beneath the Western Junggar, southwestern Chinese Altaids. However, regional high-resolution geophysical data have been rarely deployed to image its geometry, making it difficult to trace its evolution and final geodynamic setting. Presently, two magnetotelluric (MT) profiles are deployed across the northwest margin of the Junggar basin and the southern Darbut belt to image the electrical structure of the crust and lithospheric mantle. High-quality data at 102 sites and the quasi-2D indications of phase tensor skew angles and impedance phase ellipses for relatively short periods (up to 500 s) allow us to invert the two profile data by a 2-D scheme. The resistivity cross-section of a NW-SE striking LINE2 sheds light on a fossil intraoceanic subduction system, and reveals the Miaoergou intrusions as a bowl-like pluton, indicating that the multi-phase intrusions primarily formed in a post-collisional setting. The resistivity cross-section of striking NE-SW LINE1 reveals a possible oceanic slab with relatively lower resistivity underlying the low-resistivity sedimentary strata and high-resistivity mélange. Given that the profile of LINE1 cuts the out-rise zone of a subducted slab developed during the late Paleozoic, the 2-D resistivity model may thus represent the zone that have experienced heterogeneous deformation, reflecting subduction with barrier variation parallel to the ancient trench. Moreover, as shown in previous results, the new MT data also illustrate that the Darbut Fault is a thin-skinned structure, which has been erased at depths during the subsequent magmatism.

  12. Selection of areas for testing in the Eleana formation: Paleozoic geology of western Yucca Flat

    Energy Technology Data Exchange (ETDEWEB)

    Sweeney, J J

    1984-07-01

    The Paleozoic geology of NTS is reviewed to select an area for underground nuclear testing in shale. Constraints on possible areas, dictated by test program requirements and economics, are areas with topographic slope less than 5/sup 0/, depths to working point less than 3000 ft., and working points above the water table. The rock formation selected is Unit J (argillite) of the Mississippian age Eleana Formation. Within NTS, Western Yucca Flat is selected as the best area to meet the requirements. Details of the Paleozoic structure of western Yucca Flat are presented. The interpretation is based on published maps, cross-sections, and reports as well as borehole, refraction seismic, and gravity data. In terms of subsurface structure and areas where Eleana Formation Unit J occurs at depths between 500 ft to 3000 ft, four possible testing areas are identified. The areas are designated here as A, B, C and the Gravity High. Available data on the water table (static water level) is reviewed for western Yucca Flat area. Depth to the water table increases from 500 to 600 ft in Area A to 1500 ft or more in the Gravity High area. Review of the water table data rules out area A and B for testing in argillite above the water table. Area C is relatively unexplored and water conditions are unknown there. Thus, the Gravity High is selected as the most promising area for selecting testing sites. There is a dolomite thrust sheet of unknown thickness overlying the argillite in the Gravity High area. An exploration program is proposed to better characterize this structure. Finally, recommendations are made for procedures to follow for eventual site characterization of a testing site in argillite. 22 references, 12 figures, 1 table.

  13. Bedded Barite Deposits from Sonora (nw Mexico): a Paleozoic Analog for Modern Cold Seeps

    Science.gov (United States)

    Canet, C.; Anadón, P.; González-Partida, E.; Alfonso, P.; Rajabi, A.; Pérez-Segura, E.; Alba-Aldave, L. A.

    2013-05-01

    The Mazatán barite deposits represent an outstanding example of Paleozoic bedded barite, a poorly understood type of mineral deposit of major economic interest. The largest barite bodies of Mazatán are hosted within an Upper Carboniferous flysch succession, which formed part of an accretionary wedge related to the subduction of the Rheic Ocean beneath Gondwana. As well, a few barite occurrences are hosted in Upper Devonian, pre-orogenic turbidites. A variety of mineralized structures is displayed by barite, including: septaria nodules, enterolitic structures, rosettes and debris-flow conglomerates. Barite is accompanied by chalcedony, pyrite (framboids) and berthierine. Gas-rich fluid inclusions in barite were analyzed by Raman spectroscopy and methane was identified, suggesting the occurrence of light hydrocarbons in the environment within which barite precipitated. 13C-depleted carbonates (δ13C: -24.3 to -18.8‰) were found in the barite deposits; they formed through anaerobic oxidation of methane coupled to sulfate reduction, and yield negative δ18O values (-11.9 to -5.2‰) reflecting the isotopic composition of Devonian-Carboniferous seawater. Methane-derived carbonates occur in modern hydrocarbon seeps and have been reported from Mesozoic and Cenozoic seep sediments, but they have never before been described in Paleozoic bedded barite deposits. δ34S of barite varies from +17.6 to +64.1‰, with the lowest values overlapping the range for coeval seawater sulfate; this distribution indicates a process of sulfate reduction. Barite precipitation can be explained by mixing of methane- and barium-rich fluids with pore-water (seawater) containing sulfate residual from microbial reduction. Two analyses from barite gave an 87Sr/86Sr within and slightly above the range for seawater at the time of deposition, with 0.708130 and 0.708588, which would preclude the involvement of hydrothermal fluids in the mineralization process.

  14. Delayed fungal evolution did not cause the Paleozoic peak in coal production.

    Science.gov (United States)

    Nelsen, Matthew P; DiMichele, William A; Peters, Shanan E; Boyce, C Kevin

    2016-03-01

    Organic carbon burial plays a critical role in Earth systems, influencing atmospheric O2 and CO2 concentrations and, thereby, climate. The Carboniferous Period of the Paleozoic is so named for massive, widespread coal deposits. A widely accepted explanation for this peak in coal production is a temporal lag between the evolution of abundant lignin production in woody plants and the subsequent evolution of lignin-degrading Agaricomycetes fungi, resulting in a period when vast amounts of lignin-rich plant material accumulated. Here, we reject this evolutionary lag hypothesis, based on assessment of phylogenomic, geochemical, paleontological, and stratigraphic evidence. Lignin-degrading Agaricomycetes may have been present before the Carboniferous, and lignin degradation was likely never restricted to them and their class II peroxidases, because lignin modification is known to occur via other enzymatic mechanisms in other fungal and bacterial lineages. Furthermore, a large proportion of Carboniferous coal horizons are dominated by unlignified lycopsid periderm with equivalent coal accumulation rates continuing through several transitions between floral dominance by lignin-poor lycopsids and lignin-rich tree ferns and seed plants. Thus, biochemical composition had little relevance to coal accumulation. Throughout the fossil record, evidence of decay is pervasive in all organic matter exposed subaerially during deposition, and high coal accumulation rates have continued to the present wherever environmental conditions permit. Rather than a consequence of a temporal decoupling of evolutionary innovations between fungi and plants, Paleozoic coal abundance was likely the result of a unique combination of everwet tropical conditions and extensive depositional systems during the assembly of Pangea.

  15. Previous geological exploration of antimony ore occurrences Krčeva Reka (eastern Serbia in terms of the potentiality of the epithermal gold

    Directory of Open Access Journals (Sweden)

    Vukas Radoslav B.

    2014-01-01

    Full Text Available This paper presents the results of a previous geological exploration of antimony ore occurrences in the area Krčeva river. Data analysis of geological, geophysical, geochemical prospecting and appropriate methods of laboratory testing identified a series of similarities to epithermal gold mineralization Carline type and formed a preliminary model of its creation.

  16. Gold grade of epithermal gold ore at Lamuntet, Brang Rea, West Sumbawa District, West Nusa Tenggara Province, Indonesia

    Science.gov (United States)

    Ernawati, Rika; Idrus, Arifudin; TBMP, Himawan

    2017-06-01

    Lamuntet is one of gold ore mining area carried out by the Artisanal Small scale Gold Mining (ASGM) located in West Sumbawa, Indonesia. Most of the miners at this area are not the local miners but also those from other regions. Mineralization of this area is strong identified as low sulfidation epithermal system. There are two blocks of this mining location, namely, Ngelampar block with an area of 0.164 km2 and Song block with an area of 0.067 km2. This study was focused on Ngelampar block. The characteristic of epithermal system is the existence of quartz vein with comb, vuggy, and sugary texture. The aim of this research was to analyze the gold grade and other metals, such as Cu, Ag, Pb, As, Zn, and Hg. The research methods included literature study from previous researches, field work, laboratory work, and interpretation. The literature study was performed on previous researches with similar study area. The field work comprised of direct observation and sampling. Fieldwork was done for a week to obtain gold ore/vein. Sixteen samples were analyzed to obtain the grade of ore/metal. The Hg laboratory analysis was then performed on the six samples with the highest gold grade. Laboratory works were conducted at Intertek Jakarta by using Fire Assay (FA) for gold grade and Atomic Absorption Spectrophotometry (AAS) for Cu, Ag, Pb, As, Zn, and Hg. Results of the analysis showed the range of Au was grade (0.1 ppm - 27.8 ppm), Cu was 26 ppm -1740 ppm, Pb was 101 ppm- >4000 ppm, Zn of 73 ppm- >10,000 ppm, Ag of 3 ppm -185 ppm, As was 150 ppm-6530 ppm, and Hg of 0.08 ppm - 1.89 ppm. L1 and L15 had high grade for all values (Au, Ag, Zn, Cu, As, and Hg). Gold mineralization was formed as electrum because of Ag content is higher than 20%. Associated minerals of the samples in the study area were galena, sphalerite, arsenopyrite, and chalcopyrite which showed the characteristic of rich base metal of Pb, Zn, and Cu at LS epithermal.

  17. Ore deposits and epithermal evidences associated with intra-magmatic faults at Aïn El Araâr-Oued Belif ring structure (NW of Tunisia)

    Science.gov (United States)

    Aissa, Wiem Ben; Aissa, Lassaâd Ben; Amara, Abdesslem Ben Haj; Tlig, Said; Alouani, Rabah

    2017-03-01

    Hydrothermal ore deposits at Aïn El Araâr-Oued Belif location are classified as epithermal deposits type. The ore bodies are hosted by upper Turonian (8-9 M.y) volcanic rhyodacitic complex. Polymetallic sulfide orebodies are mainly concentrated within intra-magmatic faults. Petrographic, XRD, and TEM-STEM investigations revealed that ore minerals are essentially, arsenopyrite, pyrite, chalcopyrite, pyrrhotite, hematite, goethite and magnetite with Au, Ag and Pt trace metals. Gangue minerals are mainly adularia, quartz, sericite, alunite, tridymite, chlorite, phlogopite and smectite. Epithermal alteration is well zoned with four successive characteristic zones: (1) zone of quartz-adularia-sericite and rare alunite; (2) zone of kaolinite and plagioclase albitization; (3) intermediate zone of illite-sericite; (4) sapropelic alteration type zone of chlorite-smectite and rare illite. This can be interpreted as a telescoping of two different acidity epithermal phases; low sulfidation (adularia-sericite) and high sulfidation (quartz-alunite), separated in time or due to a gradual increase of fluids acidity and oxicity within the same mineralization phase. Brecciated macroscopic facies with fragments hosting quartz-adularia-sericite minerals (low-sulfidation phase) without alunite, support the last hypothesis. Geodynamic context and mineral alteration patterns are closely similar to those of Maria Josefa gold mine at SE of Spain which exhibit a volcanic-hosted epithermal ore deposit in a similar vein system, within rhyolitic ignimbrites, altered to an argillic assemblage (illite-sericite abundant and subordinate kaolinite) that grades outwards into propylitic alteration (Sanger-von Oepen et al. (1990)). Mineralogical and lithologic study undertaken in the volcanic host rock at Aïn El Araâr-Oued Belif reveals a typical epithermal low-sulfidation and high-sulfidation ore deposits with dominance of low-sulfidation. Host rocks in these systems range from silicic to

  18. OPTIMIZATION OF THE EPITHERMAL NEUTRON BEAM FOR BORON NEUTRON CAPTURE THERAPY AT THE BROOKHAVEN MEDICAL RESEARCH REACTOR.

    Energy Technology Data Exchange (ETDEWEB)

    HU,J.P.; RORER,D.C.; RECINIELLO,R.N.; HOLDEN,N.E.

    2002-08-18

    Clinical trials of Boron Neutron Capture Therapy for patients with malignant brain tumor had been carried out for half a decade, using an epithermal neutron beam at the Brookhaven's Medical Reactor. The decision to permanently close this reactor in 2000 cut short the efforts to implement a new conceptual design to optimize this beam in preparation for use with possible new protocols. Details of the conceptual design to produce a higher intensity, more forward-directed neutron beam with less contamination from gamma rays, fast and thermal neutrons are presented here for their potential applicability to other reactor facilities. Monte Carlo calculations were used to predict the flux and absorbed dose produced by the proposed design. The results were benchmarked by the dose rate and flux measurements taken at the facility then in use.

  19. Errors of absolute methods of reactor neutron activation analysis caused by non-1/E epithermal neutron spectra

    International Nuclear Information System (INIS)

    Erdtmann, G.

    1993-08-01

    A sufficiently accurate characterization of the neutron flux and spectrum, i.e. the determination of the thermal flux, the flux ratio and the epithermal flux spectrum shape factor, α, is a prerequisite for all types of absolute and monostandard methods of reactor neutron activation analysis. A convenient method for these measurements is the bare triple monitor method. However, the results of this method, are very imprecise, because there are high error propagation factors form the counting errors of the monitor activities. Procedures are described to calculate the errors of the flux parameters, the α-dependent cross-section ratios, and of the analytical results from the errors of the activities of the monitor isotopes. They are included in FORTRAN programs which also allow a graphical representation of the results. A great number of examples were calculated for ten different irradiation facilities in four reactors and for 28 elements. Plots of the results are presented and discussed. (orig./HP) [de

  20. Geology and hydrothermal alteration at the Madh adh Dhahab epithermal precious-metal deposit, Kingdom of Saudi Arabia

    Science.gov (United States)

    Doebrich, J.L.; LeAnderson, J.P.

    1984-01-01

    Mahd adh Dhahab is a late Precambrian epithermal gold-silver-base metal deposit located in the west-central part of the Arabian Shield. North-trending quartz veins containing base and precious metals cut an east-striking, north-dipping homoclinal sequence of volcanic, volcaniclastic, and epiclastic rocks of intermediate to felsic composition. Ore was localized where the veins cut competent, coarse-grained, fragmental units directly below incompetent and impermeable tuff units. The proximity of an epizonal rhyolite porphyry stock to these contacts also was important in localizing ore. Ore minerals include native gold and silver, gold-silver tellurides, chalcopyrite, sphalerite, and minor galena, and five stages of mineralization have been identified.

  1. Metallogeny of the Gold Quadrilateral: style and characteristics of epithermal - subvolcanic mineralized structures, South Apuseni Mts., Romania

    Directory of Open Access Journals (Sweden)

    S̡erban-Nicolae Vlad

    2004-04-01

    Full Text Available The Romanian territory contains numerous ore deposits mined since pre-Roman times. An assessment of historical gold production of the Gold Quadri-lateral (GQ yielded a total estimate of 55.7 Moz of gold throughout an area of 2400 km2. Interpreted in terms of mineralization density this is 23,208 oz of gold/ km2. The geological setting of the GQ is represented mainly by Tertiary (14.7 My to 7.4 My calc-alkaline volcano-plutonic complexes of intermediate character in sedimentary basins of molasse type. These basins are tectonically controlled by NW-SE lineation across early Alpine magmatic products, i.e. subduction related Jurassic-Lower Cretaceous igneous association (island arc ophiolites and granitoids and Upper Cretaceous igneous association (banatites. The Tertiary magmatism is associated with extensional tectonics caused by NE escape of the Pannonian region during Upper Oligocene-Lower Miocene times. As a result of tectono-magmatic and mineralization-alteration characteristics, two metallogenetical types were separated in the GQ, i.e. calc-alkaline andesitic (CAM and sub-alkaline rhyodacitic (SRM. Both develop almost entirely low-sulfidation type of Au epithermal mineralization. However, two subtypes, -rich in sulfide (2-7% and -poor in sulfide (7-20% were delineated and correlated with CAM type and SRM type respectively. Furthermore, CAM is connected at deeper levels with Cu-Au+/-Mo porphyry systems in contrast with SRM, which is a non-porphyry environment. The Brad-Săcărâmb district contains mainly CAM type andesitic structures. It is a porphyry environment with epithermal low-sulfidation-rich sulfide vein halo (Barza, Troiţa-Bolcana deposits. However, a few SRM type patterns, such as Măgura Ţebii, Băiţa-Crăciuneşti and Săcărâmb, deposits exhibit Au-Ag-Te low-sulfidation-poor sulfide epithermal vein halo. The Zlatna-Stănija district exhibits similar characteristics, with Au-Ag+/-Pb, Zn veins in Cu-Au subvolcanic

  2. Evaluation of Weights of Evidence to Predict Epithermal-Gold Deposits in the Great Basin of the Western United States

    International Nuclear Information System (INIS)

    Raines, Gary L.

    1999-01-01

    The weights-of-evidence method provides a simple approach to the integration of diverse geologic information. The application addressed is to construct a model that predicts the locations of epithermal-gold mineral deposits in the Great Basin of the western United States. Weights of evidence is a data-driven method requiring known deposits and occurrences that are used as training sites in the evaluated area. Four hundred and fifteen known hot spring gold-silver, Comstock vein, hot spring mercury, epithermal manganese, and volcanogenic uranium deposits and occurrences in Nevada were used to define an area of 327.4 km 2 as training sites to develop the model. The model consists of nine weighted-map patterns that are combined to produce a favorability map predicting the distribution of epithermal-gold deposits. Using a measure of the association of training sites with predictor features (or patterns), the patterns can be ranked from best to worst predictors. Based on proximity analysis, the strongest predictor is the area within 8 km of volcanic rocks younger than 43 Ma. Being close to volcanic rocks is not highly weighted, but being far from volcanic rocks causes a strong negative weight. These weights suggest that proximity to volcanic rocks define where deposits do not occur. The second best pattern is the area within 1 km of hydrothermally altered areas. The next best pattern is the area within 1 km of known placer-gold sites. The proximity analysis for gold placers weights this pattern as useful when close to known placer sites, but unimportant where placers do not exist. The remaining patterns are significantly weaker predictors. In order of decreasing correlation, they are: proximity to volcanic vents, proximity to east-west to northwest faults, elevated airborne radiometric uranium, proximity to northwest to west and north-northwest linear features, elevated aeromagnetics, and anomalous geochemistry. This ordering of the patterns is a function of the quality

  3. Epithermal neutron flux in the experimental channels of the RA reactor; Fluks epitermalnih neutrona u eksperimentalnim kanalima reaktora RA

    Energy Technology Data Exchange (ETDEWEB)

    Raisic, N; Dobrosavljevic, N [Institute of Nuclear Sciences Boris Kidric, Vinca, Beograd (Serbia and Montenegro)

    1961-12-15

    Epithermal neutron flux was determined by measuring the cadmium ratio from activation analysis of gold and indium foils. Irradiation was done in experimental channels VK-5, VK-2, VK-7, VK-0, VK-HS next to the core, and next to the fuels elements. Activation of bare foils and foils covered by 0.8 and 1.0 mm thick cadmium foils was done simultaneously. Activity was measured by GM counter. Corrections were done for resonant neutrons self-absorption since the foils used were too thick concerning most important resonances of gold and indium. Final results were presented as spectrum factor r for their direct use in determining the effective neutron cross sections.

  4. Lithogeochemistry and fluid flow in the epithermal Veta Rublo base metal-silver deposit, Chonta Mine (Huancavelica, Perú)

    OpenAIRE

    Castroviejo Bolibar, Ricardo; Yparraguirre, José Andrés; Chacón, E.

    2007-01-01

    The Chonta Mine (75º00’30” W & 13º04’30”S, 4495 to 5000 m absl), owned by Compañía Minera Caudalosa, operates a polymetallic Zn-Pb-Cu-Ag vein system of the low sulphidation epithermal type, hosted by cenozoic volcanics of dacitic to andesitic composition (Domos de Lava Formation). Veta Rublo, one of the main veins of the system, is worked underground to nearly 300 m. It strikes 60-80º NE and dips 60-70º SE; its width varies between 0.30 and 2.20m, and it crops out along 1 km, but is continued...

  5. Epithermal neutron activation analysis of blue-green algae Spirulina Platensis as a matrix for selenium-containing pharmaceuticals

    International Nuclear Information System (INIS)

    Mosulishvili, L.M.; Kirkesali, E.I.; Belokobyl'skij, A.I.; Khizanishvili, A.I.; Frontas'eva, M.V.; Gundorina, S.F.; Oprea, C.D.

    2000-01-01

    To evaluate the potentiality of the blue-green algae Spirulina Platensis as a matrix for the production of Se-containing pharmaceuticals, the background levels of 31 major, minor and trace elements (Na, Mg, Al, Cl, K, Ca, Sc, V, Cr, Mn, Fe, Co, Ni (using (n,p)-reaction), As, Br, Zn, Rb, Mo, Ag, Sb, I, Ba, Sm, Tb, Tm, Hf, Ta, W, Au, Hg, Th) in Spirulina Platensis biomass were determined by means of epithermal neutron activation analysis. The possibility of the purpose-oriented incorporation of Se into Spirulina Platensis biomass was demonstrated. The polynomial dependence of the Se accumulation on nutritional medium loading was revealed. The employed analytical technique allows one to reliably control the amount of toxic elements in algae Spirulina Platensis. Based on this study, a conclusion of the possibility to use Spirulina Platensis as a matrix for the production of Se-containing pharmaceuticals was drawn

  6. Investigation of ancient pottery from Lefkanti, Greece, by epithermal gamma spectroscopy using loss-free counting technology

    International Nuclear Information System (INIS)

    Ochsenkuehn, K.M.; Zouridakis, N.

    1996-01-01

    For the analysis of pottery fragments from ancient Lefkanti, instrumental neutron activation analysis was used. To have a good throughput of samples, a detectable series of short-lived isotopes was selected for the investigation. The problem of the initial high radioactivity, which normally hinders a fast γ-spectroscopic analysis, was eluded by using loss-free counting technology. This technology allows the measurement of pottery samples of about 100 mg size 1 day after a 30 min epithermal irradiation. Up to 15 samples could be analyzed in one day under these working conditions, having the possibility to analyze the elements As, Eu, Ga, Gd, La, Mn, Sb, Sm, Th, U, W and Zn, which are enough to perform statistical characterizations of potteries. (author). 11 refs., 2 figs., 1 tab

  7. Application of semiconductor MOSFET and pin diode dosimeters to epithermal neutron beam dose distribution measurements in phantoms

    International Nuclear Information System (INIS)

    Carolan, M.G.; Wallace, S.A.; Allen, B.J.; Rosenfeld, A.B.; Mathur, J.N.

    1996-01-01

    For any clinical application of Boron Neutron Capture Therapy (BNCT) fast and accurate dose calculations will be required for treatment planning. Such calculations are also necessary for the planning and interpretation of results from pre-clinical and clinical trials where the speed of calculation is not so critical. A dose calculation system based on the MCNP Monte Carlo Neutron transport code has been developed by Wallace. This system takes image data from CT scans and constructs a voxel based geometrical model for input into MCNP. To validate the calculations, a number of phantoms were constructed and exposed in the HB11 epithermal neutron beam at the HFR of the CEC Joint Research Centre in Petten. The doses recorded by arrays of PIN diode neutron dosimeters and MOSFET gamma dosimeters in these phantoms were compared with the calculated results from the MCNP dose planning system. Initial results have been reported elsewhere. Poster 197. (author)

  8. The Paleozoic metamorphic history of the Central Orogenic Belt of China from 40Ar/39Ar geochronology of eclogite garnet fluid inclusions

    NARCIS (Netherlands)

    Qiu, H.N.; Wijbrans, J.R.

    2008-01-01

    The pressure-temperature-time evolution of the UHP eclogites of Dabie-Sulu, in the eastern sector of the Central Orogenic Belt of China shows a complex pattern of predominantly Triassic, and to a lesser extent Early Paleozoic ages.

  9. Mineralogy, structural control and age of the Incachule Sb epithermal veins, the Cerro Aguas Calientes collapse caldera, Central Puna

    Science.gov (United States)

    Salado Paz, Natalia; Petrinovic, Iván; Do Campo, Margarita; Brod, José Affonso; Nieto, Fernando; da Silva Souza, Valmir; Wemmer, Klauss; Payrola, Patricio; Ventura, Roberto

    2018-03-01

    The Incachule Sb epithermal veins is located near to the N-E rim of the Cerro Aguas Calientes collapse caldera (17.5-10.8 Ma), in the geologic province of Puna, Salta- Argentina. It is hosted in Miocene felsic volcanic rocks with continental arc signature. The district includes twelve vein systems with mineralization of Sb occurring in hydrothermal breccias and stockwork. The veins are composed of quartz-sulfide with pyrite, stibnite and arsenopyrite. All around the veins, wall rocks are variably altered to clay minerals and sulfates in an area of around 2.5 km wide by more than 7 km long. The hydrothermal alterations recognized are: silicic, phyllic and argillic. The veins are characterized by high contents of Sb, As, and Tl and intermediate contents of Pb-Zn-Cu, and traces of Ag and Au. Homogenization and ice-melting temperatures of fluid inclusions vary from 125 °C to 189 °C and -2.4 °C to -0.8 °C. The isotopic data indicated a range of δ34S -3.04‰ to +0.72‰ consistent with a magmatic source for sulfur. We present the firsts K-Ar ages for hydrothermal illite/smectite mixed layers (I/SR1, 60% illite layers) and illite that constrain the age of the ore deposit (8.5-6.7 ± 0.2 Ma). The data shown here, let characterized the Incachule district as a shallow low sulfidation epithermal system hosted in a collapse caldera. Our data also indicate that mineralization is structurally controlled by a fault system related to the 10.3 Ma collapse of Aguas Calientes caldera. The interpreted local stress field is consistent with the regional one.

  10. Thermal and epithermal neutron fluence rate gradient measurements by PADC detectors in LINAC radiotherapy treatments-field

    Energy Technology Data Exchange (ETDEWEB)

    Barrera, M. T., E-mail: mariate9590@gmail.com; Barros, H.; Pino, F.; Sajo-Bohus, L. [Universidad Simón Bolívar, Nuclear Physics Laboratory, Sartenejas, Caracas (Venezuela, Bolivarian Republic of); Dávila, J. [Física Médica C. A. and Universidad Central de Venezuela, Caracas (Venezuela, Bolivarian Republic of)

    2015-07-23

    LINAC VARIAN 2100 is where energetic electrons produce Bremsstrahlung radiation, with energies above the nucleon binding energy (E≈5.5MeV). This radiation induce (γ,n) and (e,e’n) reactions mainly in the natural tungsten target material (its total photoneutron cross section is about 4000 mb in a energy range from 9-17 MeV). These reactions may occur also in other components of the system (e.g. multi leaf collimator). During radiation treatment the human body may receive an additional dose inside and outside the treated volume produced by the mentioned nuclear reactions. We measured the neutron density at the treatment table using nuclear track detectors (PADC-NTD). These covered by a boron-converter are employed, including a cadmium filter, to determine the ratio between two groups of neutron energy, i.e. thermal and epithermal. The PADC-NTD detectors were exposed to the radiation field at the iso-center during regular operation of the accelerator. Neutron are determined indirectly by the converting reaction {sup 10}B(n,α){sup 7}Li the emerging charged particle leave their kinetic energy in the PADC forming a latent nuclear track, enlarged by chemical etching (6N, NaOH, 70°C). Track density provides information on the neutron density through calibration coefficient (∼1.6 10{sup 4} neutrons /track) obtained by a californium source. We report the estimation of the thermal and epithermal neutron field and its gradient for photoneutrons produced in radiotherapy treatments with 18 MV linear accelerators. It was obsered that photoneutron production have higher rate at the iso-center.

  11. Devonian paleomagnetism of the North Tien Shan: Implications for the middle-Late Paleozoic paleogeography of Eurasia

    Science.gov (United States)

    Levashova, Natalia M.; Mikolaichuk, Alexander V.; McCausland, Philip J. A.; Bazhenov, Mikhail L.; Van der Voo, Rob

    2007-05-01

    The Ural-Mongol belt (UMB), between Siberia, Baltica and Tarim, is widely recognized as the locus of Asia's main growth during the Paleozoic, but its evolution remains highly controversial, as illustrated by the disparate paleogeographic models published in the last decade. One of the largest tectonic units of the UMB is the Kokchetav-North Tien Shan Domain (KNTD) that stretches from Tarim in the south nearly to the West Siberian Basin. The KNTD comprises several Precambrian microcontinents and numerous remnants of Early Paleozoic island arcs, marginal basins and accretionary complexes. In Late Ordovician time, all these structures had amalgamated into a single contiguous domain. Its paleogeographic position is of crucial importance for elucidating the Paleozoic evolution of the UMB in general and of the Urals in particular. The Aral Formation, located in Kyrgyzstan in the southern part of the KNTD, consists of a thick Upper Devonian (Frasnian) basalt-andesite sequence. Paleomagnetic data show a dual-polarity characteristic component (Dec/Inc = 286° / + 56°, α95 = 9°, k = 21, N = 15 sites). The primary origin of this magnetization is confirmed by a positive test on intraformational conglomerates. We combine this result with other Paleozoic data from the KNTD and show its latitudinal motion from the Late Ordovician to the end of the Paleozoic. The observed paleolatitudes are found to agree well with the values extrapolated from Baltica to a common reference point (42.5°N, 73°E) in our sampling area for the entire interval; hence coherent motion of the KNTD and Baltica is strongly indicated for most of the Paleozoic. This finding contradicts most published models of the UMB evolution, where the KNTD is separated from Baltica by a rather wide Ural Ocean containing one or more major plate boundaries. An exception is the model of Şengör and Natal'in [A.M.C. Şengör, B.A. Natal'in, Paleotectonics of Asia: fragments of a synthesis, in: A. Yin and M. Harrison (eds

  12. The Chara-Sina dyke swarm in the structure of the Middle Paleozoic Vilyui rift system (Siberian Craton)

    Science.gov (United States)

    Kiselev, A. I.; Konstantinov, K. M.; Yarmolyuk, V. V.; Ivanov, A. V.

    2016-11-01

    The formation of the Vilyui rift system in the eastern Siberian Craton was finished with breakdown of the continent and formation of its eastern margin. A characteristic feature of this rift system is the radial distribution of dyke swarms of basic rocks. This peculiarity allows us to relate it to the breaking processes above the mantle plume, the center of which was located in the region overlain in the modern structure by the foreland of the Verkhoyan folded-thrust belt. The Chara-Sina dyke swarm is the southern part of a large area of Middle Paleozoic basaltic magmatism in the eastern Siberian Craton. The OIB-like geochemical characteristics of dolerite allow us to suggest that the melting substrate for Middle Paleozoic basaltic magmatism was represented by a relatively homogeneous, mid-depleted mantle of the plume with geochemical parameters similar to those of OIB.

  13. Evolutionary and ecological perspectives of Late Paleozoic ferns. Part III. Anachoropterid ferns (including Anachoropteris, Tubicaulis, the Sermayaceae, Kaplanopteridaceae and Psalixochlaenaceae)

    OpenAIRE

    Galtier, Jean; Phillips, Tom L.

    2014-01-01

    The anachoropterid ferns, previously assigned to the family Anachoropteridaceae, are a group of anatomically preserved late Paleozoic filicalean ferns characterized by a C-shaped foliar xylem with abaxially recurved arms (inversicatenalean anatomy) and two main protoxylem strands. The variously curved to strongly inrolled foliar xylem certainly reflects different evolutionary trends within the morphogenus Anachoropteris. The occurrence of two groups of Tubicaulis is supported by differences i...

  14. Late Archaean-early Proterozoic source ages of zircons in rocks from the Paleozoic orogen of western Galicia, NW Spain

    Energy Technology Data Exchange (ETDEWEB)

    Kuijper, R P; Priem, H N.A. [Laboratorium voor Isotopen-Geologie, Amsterdam (Netherlands); Den Tex, E [Rijksuniversiteit Utrecht (Netherlands). Inst. voor Aardwetenschappen

    1982-08-01

    U-Pb data are reported for nine suites of zircons and three monazites from the Paleozoic orogen in western Galicia: one paragneiss and six orthogneisses from the early Paleozoic basement, and two Carboniferous (ca. 310 Ma old) intrusions of two-mica granite. New whole-rock Rb-Sr analyses, along with earlier data, indicate an age of ca. 470-440 Ma (Ordovician) for the emplacement of the granitic precursors of the orthogneisses. Monazite from the paragneiss also yields an U-Pb age of ca. 470 Ma. From the high initial /sup 87/Sr//sup 86/Sr ratios an involvement of Precambrian continental crust material is evident in the generation of the early Paleozoic suite of granites, while the zircon U-Pb data give evidence of the presence of about 3.0-2.0 Ga old (late Archaean-early Proterozoic) components in the source material. Zircons from the oldest sedimentary rocks in the area, now present as catazonal paragneisses and a likely source for the granites, likewise reveal a provenance age of 3.0-2.0 Ga.

  15. Revisions to the original extent of the Devonian Shale-Middle and Upper Paleozoic Total Petroleum System

    Science.gov (United States)

    Enomoto, Catherine B.; Rouse, William A.; Trippi, Michael H.; Higley, Debra K.

    2016-04-11

    Technically recoverable undiscovered hydrocarbon resources in continuous accumulations are present in Upper Devonian and Lower Mississippian strata in the Appalachian Basin Petroleum Province. The province includes parts of New York, Pennsylvania, Ohio, Maryland, West Virginia, Virginia, Kentucky, Tennessee, Georgia, and Alabama. The Upper Devonian and Lower Mississippian strata are part of the previously defined Devonian Shale-Middle and Upper Paleozoic Total Petroleum System (TPS) that extends from New York to Tennessee. This publication presents a revision to the extent of the Devonian Shale-Middle and Upper Paleozoic TPS. The most significant modification to the maximum extent of the Devonian Shale-Middle and Upper Paleozoic TPS is to the south and southwest, adding areas in Tennessee, Georgia, Alabama, and Mississippi where Devonian strata, including potential petroleum source rocks, are present in the subsurface up to the outcrop. The Middle to Upper Devonian Chattanooga Shale extends from southeastern Kentucky to Alabama and eastern Mississippi. Production from Devonian shale has been established in the Appalachian fold and thrust belt of northeastern Alabama. Exploratory drilling has encountered Middle to Upper Devonian strata containing organic-rich shale in west-central Alabama. The areas added to the TPS are located in the Valley and Ridge, Interior Low Plateaus, and Appalachian Plateaus physiographic provinces, including the portion of the Appalachian fold and thrust belt buried beneath Cretaceous and younger sediments that were deposited on the U.S. Gulf Coastal Plain.

  16. Upper Paleozoic coal measures and unconventional natural gas systems of the Ordos Basin, China

    Directory of Open Access Journals (Sweden)

    Xuan Tang

    2012-11-01

    Full Text Available Upper Paleozoic coal measures in the Ordos Basin consist of dark mudstone and coal beds and are important source rocks for gas generation. Gas accumulations include coal-bed methane (CBM, tight gas and conventional gas in different structural areas. CBM accumulations are mainly distributed in the marginal area of the Ordos Basin, and are estimated at 3.5 × 1012 m3. Tight gas accumulations exist in the middle part of the Yishan Slope area, previously regarded as the basin-centered gas system and now considered as stratigraphic lithologic gas reservoirs. This paper reviews the characteristics of tight gas accumulations: poor physical properties (porosity < 8%, permeability < 0.85 × 10−3 μm2, abnormal pressure and the absence of well-defined gas water contacts. CBM is a self-generation and self-reservoir, while gas derived from coal measures migrates only for a short distance to accumulate in a tight reservoir and is termed near-generation and near-reservoir. Both CBM and tight gas systems require source rocks with a strong gas generation ability that extends together over wide area. However, the producing area of the two systems may be significantly different.

  17. Braided fluvial sedimentation in the lower paleozoic cape basin, South Africa

    Science.gov (United States)

    Vos, Richard G.; Tankard, Anthony J.

    1981-07-01

    Lower Paleozoic braided stream deposits from the Piekenier Formation in the Cape Province, South Africa, provide information on lateral and vertical facies variability in an alluvial plain complex influenced by a moderate to high runoff. Four braided stream facies are recognized on the basis of distinct lithologies and assemblages of sedimentary structures. A lower facies, dominated by upward-fining conglomerate to sandstone and mudstone channel fill sequences, is interpreted as a middle to lower alluvial plain deposit with significant suspended load sedimentation in areas of moderate to low gradients. These deposits are succeeded by longitudinal conglomerate bars which are attributed to middle to upper alluvial plain sedimentation with steeper gradients. This facies is in turn overlain by braid bar complexes of large-scale transverse to linguoid dunes consisting of coarse-grained pebbly sandstones with conglomerate lenses. These bar complexes are compared with environments of the Recent Platte River. They represent a middle to lower alluvial plain facies with moderate gradients and no significant suspended load sedimentation or vegetation to stabilize channels. These bar complexes interfinger basinward with plane bedded medium to coarse-grained sandstones interpreted as sheet flood deposits over the distal portions of an alluvial plain with low gradients and lacking fine-grained detritus or vegetation.

  18. Conodont color alteration index and upper Paleozoic thermal history of the Amazonas Basin, Brazil

    Science.gov (United States)

    Cardoso, Cassiane Negreiros; Sanz-López, Javier; Blanco-Ferrera, Silvia; Lemos, Valesca Brasil; Scomazzon, Ana Karina

    2015-12-01

    The conodont color alteration index (CAI) was determined in elements from core samples of the Frasnian Barreirinha Formation (one well) and of the Pennsylvanian-Permian Tapajós Group (twenty three wells and one limestone quarry) in the Amazonas Basin. The thermal history of the basin is analyzed using the CAI value distribution represented in maps and stratigraphic sections through correlation schemes, and in conjunction with previously published data. The pattern of palaeotemperatures for CAI values of 1.5-3 is coincident with organic matter maturation under a sedimentary overburden providing diagenetic conditions in the oil/gas window. Locally, conodonts show metamorphism (CAI value of 6-7) in relation to the intrusion of diabase bodies in beds including high geothermal gradient evaporites. Microtextural alteration on the surface conodonts commonly shows several types of overgrowth microtextures developed in diagenetic conditions. Locally, recrystallization in conodonts with a high CAI value is congruent with contact metamorphism in relation to Mesozoic intrusions. The CAI values of 1.5 or 2 observed close to the surface in several areas of the basin may be interpreted in relation to a high thermal palaeogradient derived from the magmatic episode or/and to the local denudation of the upper part of the Paleozoic succession prior to this thermal event.

  19. Two possibilities for New Siberian Islands terrane tectonic history during the Early Paleozoic based on paleomagnetic data

    Science.gov (United States)

    Metelkin, Dmitry V.; Chernova, Anna I.; Vernikovsky, Valery A.; Matushkin, Nikolay Yu.

    2017-04-01

    The New Siberian Islands (NSI), located in the East Siberian Sea in the junction region of various structural elements, are a key target for deciphering the tectonic evolution of the Eastern Arctic. In recent years, we went on several expeditions and gathered an extensive geological material for this territory. Among other things, we could prove that the basement of the De Long and Anjou archipelagos structures is Precambrian and the overlying Paleozoic sections formed within the same terrane. The form of the boundaries of the NSI terrane are actively debated and are probably continued from the Lyakhovsky islands in the south-west to the southern parts of the submerged Mendeleev Ridge, for which there is increasing evidence of continental crust. Today there are several models that interpret the Paleozoic-Mesozoic tectonic history and structural affiliation of the NSI terrane. Some propose that the Paleozoic sedimentary section formed in a passive margin setting of the Siberian paleocontinent. Others compare its history with marginal basins of the Baltica and Laurentia continents or consider the NSI terrane as an element of the Chukotka-Alaska microplate. These models are mainly based on results of paleobiogeographical and lithological-facies analyses, including explanations of probable sources for detrital zircons. Our paleomagnetic research on sedimentary, volcanogenic-sedimentary and igneous rocks of the Anjou (Kotelny and Bel'kovsky islands) and De Long (Bennett, Jeannette and Henrietta islands) archipelagos let us calculate an apparent polar wander path for the early Paleozoic interval of geological history, which allows us to conclude that the NSI terrane could not have been a part of the continental plates listed above, but rather had active tectonic boundaries with them. Our paleomagnetic data indicate that the NSI terrane drifted slowly and steadily in the tropical and subtropical regions no higher than 40 degrees. However, the main uncertainty for the

  20. A preliminary inter-centre comparison study for photon, thermal neutron and epithermal neutron responses of two pairs of ionisation chambers used for BNCT

    International Nuclear Information System (INIS)

    Roca, Antoaneta; Liu, Yuan-Hao; Wojnecki, Cecile; Green, Stuart; Nievaart, Sander; Ghani, Zamir; Moss, Ray

    2009-01-01

    The dual ionisation chamber technique is the recommended method for mixed field dosimetry of epithermal neutron beams. This paper presents initial data from an ongoing inter-comparison study involving two identical pairs of ionisation chambers used at the BNCT facilities of Petten, NL and of University of Birmingham, UK. The goal of this study is to evaluate the photon, thermal neutron and epithermal neutron responses of both pairs of TE(TE) (Exradin T2 type) and Mg(Ar) (Exradin M2 type) ionisation chambers in similar experimental conditions. At this stage, the work has been completed for the M2 type chambers and is intended to be completed for the T2 type chambers in the near future.

  1. Application of epithermal neutron activation in multielement analysis of silicate rocks employing both coaxial Ge(Li) and low energy photon detector systems

    Science.gov (United States)

    Baedecker, P.A.; Rowe, J.J.; Steinnes, E.

    1977-01-01

    The instrumental activation analysis of silicate rocks using epithermal neutrons has been studied using both high resolution coaxial Ge(Li) detectors and low energy photon detectors, and applied to the determination of 23 elements in eight new U.S.G.S. standard rocks. The analytical use X-ray peaks associated with electron capture or internal conversion processes has been evaluated. Of 28 elements which can be considered to be determinable by instrumental means, the epithermal activation approach is capable of giving improved sensitivity and precision in 16 cases, over the normal INAA procedure. In eleven cases the use of the low energy photon detector is thought to show advantages over convertional coaxial Ge(Li) spectroscopy. ?? 1977 Akade??miai Kiado??.

  2. Use of boron nitride for neutron spectrum characterization and cross-section validation in the epithermal range through integral activation measurements

    Science.gov (United States)

    Radulović, Vladimir; Trkov, Andrej; Jaćimović, Radojko; Gregoire, Gilles; Destouches, Christophe

    2016-12-01

    A recent experimental irradiation and measurement campaign using containers made from boron nitride (BN) at the Jožef Stefan Institute (JSI) TRIGA Mark II reactor in Ljubljana, Slovenia, has shown the applicability of BN for neutron spectrum characterization and cross-section validation in the epithermal range through integral activation measurements. The first part of the paper focuses on the determination of the transmission function of a BN container through Monte Carlo calculations and experimental measurements. The second part presents the process of tayloring the sensitivity of integral activation measurements to specific needs and a selection of suitable radiative capture reactions for neutron spectrum characterization in the epithermal range. A BN container used in our experiments and its qualitative effect on the neutron spectrum in the irradiation position employed is displayed in the Graphical abstract.

  3. Seismic Azimuthal Anisotropy of the Lower Paleozoic Shales in Northern Poland: can we reliably detect it?

    Science.gov (United States)

    Cyz, Marta; Malinowski, Michał

    2017-04-01

    Analysis of the azimuthal anisotropy is an important aspect of characterization the Lower Paleozoic shale play in northern Poland, since it can be used to map pre-existing fracture networks or help in optimal placement of the horizontal wells. Previous studies employed Velocity versus Azimuth (VVAz) method and found that this anisotropy is weak - on the order of 1-2%, only locally - close to major fault zones - being higher (ca. 7%). This is consistent with the recent re-interpretation of the cross-dipole sonic data, which indicates average shear wave anisotropy of 1%. The problem with the VVAz method is that it requires good definition of the interval, for which the analysis is made and it should be minimum 100 ms thick. In our case, the target intervals are thin - upper reservoir (Lower Silurian Jantar formation) is 15 m thick, lower reservoir (Upper Ordovician Sasino formation) is 25 m thick. Therefore, we prefer to use the Amplitude vs Azimuth (AVAz) method, which can be applied on a single horizon (e.g. the base of the reservoir). However, the AVAz method depends critically on the quality of the seismic data and preservation of amplitudes during processing. On top of the above mentioned issues, physical properties of the Lower Paleozoic shales from Poland seem to be unfavourable for detecting azimuthal anisotropy. For example, for both target formations, parameter g=(Vs/Vp)2 is close to 0.32, which implies that the anisotropy expressed by the anisotropic gradient in the dry (i.e. gas-filled fractures) case is close to zero. In case of e.g. the Bakken Shale, g is much higher (0.38-0.4), leading to a detectable anisotropic signature even in the dry case. Modelling of the synthetic AVAz response performed using available well data suggested that anisotropic gradient in the wet (fluid-filled) case should be detectable even in case of the weak anisotropy (1-2%). This scenario is consistent with the observation, that the studied area is located in the liquid

  4. Testing the limits of Paleozoic chronostratigraphic correlation via high-resolution (13Ccarb) biochemostratigraphy across the Llandovery–Wenlock (Silurian) boundary: Is a unified Phanerozoic time scale achievable?

    Science.gov (United States)

    Cramer, Bradley D.; Loydell, David K.; Samtleben, Christian; Munnecke, Axel; Kaljo, Dimitri; Mannik, Peep; Martma, Tonu; Jeppsson, Lennart; Kleffner, Mark A.; Barrick, James E.; Johnson, Craig A.; Emsbo, Poul; Joachimski, Michael M.; Bickert, Torsten; Saltzman, Matthew R.

    2010-01-01

    The resolution and fidelity of global chronostratigraphic correlation are direct functions of the time period under consideration. By virtue of deep-ocean cores and astrochronology, the Cenozoic and Mesozoic time scales carry error bars of a few thousand years (k.y.) to a few hundred k.y. In contrast, most of the Paleozoic time scale carries error bars of plus or minus a few million years (m.y.), and chronostratigraphic control better than ??1 m.y. is considered "high resolution." The general lack of Paleozoic abyssal sediments and paucity of orbitally tuned Paleozoic data series combined with the relative incompleteness of the Paleozoic stratigraphic record have proven historically to be such an obstacle to intercontinental chronostratigraphic correlation that resolving the Paleozoic time scale to the level achieved during the Mesozoic and Cenozoic was viewed as impractical, impossible, or both. Here, we utilize integrated graptolite, conodont, and carbonate carbon isotope (??13Ccarb) data from three paleocontinents (Baltica, Avalonia, and Laurentia) to demonstrate chronostratigraphic control for upper Llando very through middle Wenlock (Telychian-Sheinwoodian, ~436-426 Ma) strata with a resolution of a few hundred k.y. The interval surrounding the base of the Wenlock Series can now be correlated globally with precision approaching 100 k.y., but some intervals (e.g., uppermost Telychian and upper Shein-woodian) are either yet to be studied in sufficient detail or do not show sufficient biologic speciation and/or extinction or carbon isotopic features to delineate such small time slices. Although producing such resolution during the Paleozoic presents an array of challenges unique to the era, we have begun to demonstrate that erecting a Paleozoic time scale comparable to that of younger eras is achievable. ?? 2010 Geological Society of America.

  5. Magmatism and Epithermal Gold-Silver Deposits of the Southern Ancestral Cascade Arc, Western Nevada and Eastern California

    Science.gov (United States)

    John, David A.; du Bray, Edward A.; Henry, Christopher D.; Vikre, Peter

    2015-01-01

    Many epithermal gold-silver deposits are temporally and spatially associated with late Oligocene to Pliocene magmatism of the southern ancestral Cascade arc in western Nevada and eastern California. These deposits, which include both quartz-adularia (low- and intermediate-sulfidation; Comstock Lode, Tonopah, Bodie) and quartz-alunite (high-sulfidation; Goldfield, Paradise Peak) types, were major producers of gold and silver. Ancestral Cascade arc magmatism preceded that of the modern High Cascades arc and reflects subduction of the Farallon plate beneath North America. Ancestral arc magmatism began about 45 Ma, continued until about 3 Ma, and extended from near the Canada-United States border in Washington southward to about 250 km southeast of Reno, Nevada. The ancestral arc was split into northern and southern segments across an inferred tear in the subducting slab between Mount Shasta and Lassen Peak in northern California. The southern segment extends between 42°N in northern California and 37°N in western Nevada and was active from about 30 to 3 Ma. It is bounded on the east by the northeast edge of the Walker Lane. Ancestral arc volcanism represents an abrupt change in composition and style of magmatism relative to that in central Nevada. Large volume, caldera-forming, silicic ignimbrites associated with the 37 to 19 Ma ignimbrite flareup are dominant in central Nevada, whereas volcanic centers of the ancestral arc in western Nevada consist of andesitic stratovolcanoes and dacitic to rhyolitic lava domes that mostly formed between 25 and 4 Ma. Both ancestral arc and ignimbrite flareup magmatism resulted from rollback of the shallowly dipping slab that began about 45 Ma in northeast Nevada and migrated south-southwest with time. Most southern segment ancestral arc rocks have oxidized, high potassium, calc-alkaline compositions with silica contents ranging continuously from about 55 to 77 wt%. Most lavas are porphyritic and contain coarse plagioclase

  6. Climate and vegetational regime shifts in the late Paleozoic ice age earth.

    Science.gov (United States)

    DiMichele, W A; Montañez, I P; Poulsen, C J; Tabor, N J

    2009-03-01

    The late Paleozoic earth experienced alternation between glacial and non-glacial climates at multiple temporal scales, accompanied by atmospheric CO2 fluctuations and global warming intervals, often attended by significant vegetational changes in equatorial latitudes of Pangaea. We assess the nature of climate-vegetation interaction during two time intervals: middle-late Pennsylvanian transition and Pennsylvanian-Permian transition, each marked by tropical warming and drying. In case study 1, there is a catastrophic intra-biomic reorganization of dominance and diversity in wetland, evergreen vegetation growing under humid climates. This represents a threshold-type change, possibly a regime shift to an alternative stable state. Case study 2 is an inter-biome dominance change in western and central Pangaea from humid wetland and seasonally dry to semi-arid vegetation. Shifts between these vegetation types had been occurring in Euramerican portions of the equatorial region throughout the late middle and late Pennsylvanian, the drier vegetation reaching persistent dominance by Early Permian. The oscillatory transition between humid and seasonally dry vegetation appears to demonstrate a threshold-like behavior but probably not repeated transitions between alternative stable states. Rather, changes in dominance in lowland equatorial regions were driven by long-term, repetitive climatic oscillations, occurring with increasing intensity, within overall shift to seasonal dryness through time. In neither case study are there clear biotic or abiotic warning signs of looming changes in vegetational composition or geographic distribution, nor is it clear that there are specific, absolute values or rates of environmental change in temperature, rainfall distribution and amount, or atmospheric composition, approach to which might indicate proximity to a terrestrial biotic-change threshold.

  7. New paleomagnetic data from late Paleozoic sedimentary rocks of Novaya Zemlya Archipelago: tectonic implications

    Science.gov (United States)

    Abashev, Victor V.; Metelkin, Dmitry V.; Mikhaltsov, Nikolay E.; Vernikovsky, Valery A.; Matushkin, Nikolay Yu.

    2017-04-01

    New paleomagnetic data for Novaya Zemlya archipelago were obtained by processing the samples collection gathered during the 2014 field season. The paleomagnetic directions and paleomagnetic poles were determined from the Paleozoic sedimentary complexes located on the Southern Island (Upper Permian) and the Northern Island (Lower and Upper Devonian, Upper Carboniferous) of the archipelago. Positive fold and reversal tests indicate that the isolated paleomagnetic directions correspond to the primary magnetization components. The corresponding paleomagnetic pole are in good agreement with poles obtained earlier in the 1980s by E.L. Gurevich and I.A. Pogarskaya. Considering the confidence ovals, the paleomagnetic poles obtained for the sites of the Northern Island are located close to the corresponding path segment of the APWP of Europe. This means that at least since the early Devonian, the northern part of Novaya Zemlya Archipelago had a position that was close to its current position relatively to the Arctic margin of Europe and has not undergone significant shifts or rotations. However, the upper Permian paleomagnetic pole for the Southern Island is very different from the corresponding part of the European APWP. We are considering this pole position within a model, involving significant intraplate movement between the structures of the European and Siberian tectonic provinces until the Late Cretaceous. The sinistral strike-slips inferred by the model could have caused or were accompanying the opening of the Mesozoic rift system in Western Siberia. This event has reached its maximum within the South Kara basin and resulted in the north-westward (in geographic coordinates) displacement of the southern part of the Novaya Zemlya Archipelago in relation to the Arctic margin of Europe and in the deformation of the Pay-Khoy-Novaya Zemlya margin, which caused its modern curved form. The study was supported by the Russian Science Foundation, grant No. 14-37-00030 and the

  8. Geochemistry of the Late Paleozoic cherts in the Youjiang Basin: Implications for the basin evolution

    Directory of Open Access Journals (Sweden)

    Huang Hu

    2013-10-01

    Full Text Available We analyzed the major and rare earth element compositions of siliceous deposits from the Upper Devonian Liujiang Formation, Lower Carboniferous Luzhai Formation, Lower–Middle Permian Sidazhai Formation and Tapi Formation, which are widely distributed as bedded cherts in the interplatform basinal successions of the Youjiang Basin. The Liujiang Formation and Luzhai Formation cherts generally have high Al/(Al+Fe+Mn values (0.38–0.94 and are non-hydrothermal cherts. These cherts are generally characterized by moderately negative Ce anomalies and high Y/Ho values relatived to PAAS, indicating that the Youjiang Basin might have evolved into an open rift basin during the Late Devonian–Early Carboniferous. The Sidazhai Formation cherts from Ziyun generally have high Al/(Al+Fe+Mn values (0.60–0.78, suggesting negligible contribution from a hydrothermal component. The Sidazhai Formation cherts from Hechi and the Tapi Formation cherts from Malipo generally have low Al/(Al+Fe+Mn values (0.09–0.41, indicating an intense hydrothermal input. Relatived to the Sidazhai Formation cherts, the Tapi Formation cherts have higher Ce/Ce* values (0.68±0.19 and lower Y/Ho values (41.83±13.27, which may be affected by the terrigenous input from the Vietnam Block. The Sidazhai Formation cherts from Ziyun and Hechi exhibit negative Ce anomalies (0.43±0.12, 0.33±0.17, respectively with high Y/Ho values (57.44±16.20, 46.02±4.27, respectively, resembling the geochemical characteristics of open-ocean basin cherts. These cherts were deposited on a passive continental margin adjacent to the Babu branch ocean, which may have contributed to upwelling. Detailed spatial studies on geochemical characteristics of the Late Paleozoic cherts can unravel the evolution of the Youjiang Basin.

  9. Intraoperative boron neutron capture therapy for malignant gliomas. First clinical results of Tsukuba phase I/II trial using JAERI mixed thermal-epithermal beam

    International Nuclear Information System (INIS)

    Matsumura, A.; Yamamoto, T.; Shibata, Y.

    2000-01-01

    Since October 1999, a clinical trial of intraoperative boron neutron capture therapy (IOBNCT) is in progress at JRR-4 (Japan Research Reactor-4) in Japan Atomic Energy Research Institute (JAERI) using mixed thermal-epithermal beam (thermal neutron beam I: TNB-I). Compared to pure thermal beam (thermal neutron beam II: TNB-II), TNB-I has an improved neutron delivery into the deep region than TNB-II. The clinical protocol and the preliminary results will be discussed. (author)

  10. The Shah-Ali-Beiglou Zn-Pb-Cu (-Ag Deposit, Iran: An Example of Intermediate Sulfidation Epithermal Type Mineralization

    Directory of Open Access Journals (Sweden)

    Khadijeh Mikaeili

    2018-04-01

    Full Text Available The Shah-Ali-Beiglou epithermal base metal-silver deposit is located in the Tarom-Hashjin metallogenic province (THMP in northwestern Iran. This deposit is hosted by quartz monzonite dikes of Oligocene age and surrounded by andesite to trachyandesite volcanic and volcaniclastic rocks of Eocene age. The subvolcanic rocks in the study area vary in composition from quartz-monzonite to monzonite and have metaluminous, calc-alkaline to shoshonitic affinity. These rocks have I-type geochemical characteristic and are related to post-collisional tectonic setting. The mineralization occurs as NE-SW and E-W-trending brecciated veins controlled by strike-slip and normal faults, which are associated to the Late Oligocene compressional regime. The mineral paragenesis of the vein mineralization is subdivided into pre-ore stage, ore stage, post-ore stage, and supergene stage. Pre-ore stage is dominated by quartz, sericite, and subhedral to anhedral pyrite as disseminated form. Ore-stage is represented by quartz, sphalerite (from 0.1 mol % to 4 mol % FeS, galena, chalcopyrite, tetrahedrite-tennantite, minor seligmannite and enargite, as vein-veinlet, cement and clast breccias. Post-ore stage is defined by deposition of quartz and carbonate along with minor barite, and supergene stage is characterized by bornite, chalcocite, covellite, hematite, goethite, and jarosite. The ore mineralization is associated with the silicic alteration. The styles of alteration are silicic, carbonate, sericitic, chloritic, and propylitic. Fluid inclusions in sphalerite have a wide range of salinities between 0.35 wt % and 21.4 wt % NaCl equivalent and homogenization temperatures range from 123 to 320 °C. The isotopic values of sulfides vary from 2.8‰ to 6.7‰ suggesting a magmatic source for the sulfur. In the present study, based on geological setting, alteration style of the host and wall rocks, main textures, mineral assemblages, composition of ore minerals, and structural

  11. Dependence of the Ratio between the Resonance Integral and Thermal Neutron Cross Section on the Deviation of the Epithermal Neutron Spectrum from the 1/E Law

    International Nuclear Information System (INIS)

    Soliman, N.F.

    2012-01-01

    In k 0 - Neutron Activation Analysis (k 0 -NAA), the conversion from the tabulated Q 0 (ratio of the resonance integral to thermal neutron cross-section)to Q 0 (α) (α is the shape factor of the epithermal neutron flux, indicating the deviation of the epithermal neutron spectrum from the ideal 1/E shape) are calculated using a FORTRAN program. The calculations are done for most elements that can be detected by neutron activation using different values of the parameter (α) ranging from -0.1≤α≤+0.1. The obtained data are used to study the dependence of the values (α) on the irradiation position factor in (k 0 -NAA)equation for some selected isotopes differ in their resonance energy and its Q 0 values. The results show that, the irradiation factor is affective mainly for low thermal tro epithermal flux ratio f especially for Q 0 value greater than 50. so consequently determining the irradiation parameters α value is not needed for irradiation positions that rich with thermal neutron. But for high f values the irradiation position factor should be taken into account. On the other hand the constructed FORTRAN program can be used to calculate the value Q 0 (α) directly for different value of α

  12. In vitro biological effectiveness of JRR-4 epithermal neutron beam. Experiment under free air beam and in water phantom. Cooperative research

    CERN Document Server

    Yamamoto, T; Horiguchi, Y; Kishi, T; Kumada, H; Matsumura, A; Nose, T; Torii, Y; Yamamoto, K

    2002-01-01

    The surviving curve and the biological effectiveness factor of dose components generated in boron neutron capture therapy (BNCT) were separately determined in neutron beams at Japan Research Reactor No.4. Surviving fraction of V79 Chinese hamster cell with or without sup 1 sup 0 B was obtained using an epithermal neutron beam (ENB), a mixed thermal-epithermal neutron beam (TNB-1), and a thermal neutron beam (TNB-2), which were used or planned to use for BNCT clinical trial. The cell killing effect of these neutron beams with or without the presence of sup 1 sup 0 B depended highly on the neutron beam used, according to the epithermal and fast neutron content in the beam. The biological effectiveness factor values of the boron capture reaction for ENB, TNB-1 and TNB-2 were 3.99+-0.24, 3.04+-0.19 and 1.43+-0.08, respectively. The biological effectiveness factor values of the high-LET dose components based on the hydrogen recoils and the nitrogen capture reaction were 2.50+-0.32, 2.34+-0.30 and 2.17+-0.28 for EN...

  13. A New Model of the Early Paleozoic Tectonics and Evolutionary History in the Northern Qinling, China

    Science.gov (United States)

    Dong, Yunpeng; Zhang, Guowei; Yang, Zhao; Qu, Hongjun; Liu, Xiaoming

    2010-05-01

    The Qinling Orogenic Belt extends from the Qinling Mountains in the west to the Dabie Mountains in the east. It lies between the North China and South China Blocks, and is bounded on the north by the Lushan fault and on the south by the Mianlue-Bashan-Xiangguang fault (Zhang et al., 2000). The Qinling Orogenic Belt itself is divided into the North and South Qinling Terranes by the Shangdan suture zone. Although the Shangdan zone is thought to represent the major suture separating the two blocks, there still exists debate about the timing and mechanism of convergence between these two blocks. For instance, some authors suggested an Early Paleozoic collision between the North China Block and South China Block (Ren et al., 1991; Kroner et al., 1993; Zhai et al., 1998). Others postulated left-lateral strike-slip faulting along the Shangdan suture at ca. 315 Ma and inferred a pre-Devonian collision between the two blocks (Mattauer et al., 1985; Xu et al., 1988). Geochemistry of fine-grained sediments in the Qinling Mountains was used to argue for a Silurian-Devonian collision (Gao et al., 1995). A Late Triassic collision has also been proposed (Sengor, 1985; Hsu et al., 1987; Wang et al., 1989), based on the formation of ultrahigh-pressure metamorphic rocks in the easternmost part of the Qinling Orogenic Belt at ~230 Ma (e.g., Li et al., 1993; Ames et al., 1996). Paleomagnetic data favor a Late Triassic-Middle Jurassic amalgamation of the North China and South China Blocks (Zhao and Coe, 1987; Enkin et al., 1992). It is clear that most authors thought that the Qinling Mountains are a collisional orogen, even they have different methods about the timing of the orogeny. Based on new detailed investigations, we propose a new model of the Early Paleozoic Tectonics and Evolutionary History between the North China and South China Blocks along the Shangdan Suture. The Shangdan suture is marked by a great number of ophiolites, island-arc volcanic rocks and other related rock

  14. The Late Paleozoic relative gas fields of coal measure in China and their significances on the natural gas industry

    Directory of Open Access Journals (Sweden)

    Chenchen Fang

    2016-12-01

    Full Text Available The coal measure gas sources of coal-derived gas fields in the Late Paleozoic China are the Lower Carboniferous Dishuiquan Formation, the Upper Carboniferous Batamayineishan Formation and Benxi Formation, the Lower Permian Taiyuan Formation and Shanxi Formation, and the Upper Permian Longtan Formation. The coal-derived gas accumulates in Ordovician, Carboniferous, Permian, and Paleocene reservoirs and are distributed in Ordos Basin, Bohai Bay Basin, Junggar Basin, and Sichuan Basin. There are 16 gas fields and 12 of them are large gas fields such as the Sulige large gas field which is China's largest reserve with the highest annual output. According to component and alkane carbon isotope data of 99 gas samples, they are distinguished to be coal-derived gas from coal-derived gas with δ13C2 > −28.5‰ and δ13C1 -δ13C2 -δ13C3 identification chart. The Late Paleozoic relative gas fields of coal measure are significant for the Chinese natural gas industry: proven natural gas geological reserves and annual output of them account for 1/3 in China, and the gas source of three significant large gas fields is coal-derived, which of five significant large gas fields supporting China to be a great gas producing country. The average reserves of the gas fields and the large gas fields formed from the late Paleozoic coal measure are 5.3 and 1.7 times that of the gas fields and the large gas fields in China.

  15. Wavelength feature mapping as a proxy to mineral chemistry for investigating geologic systems: An example from the Rodalquilar epithermal system

    Science.gov (United States)

    van der Meer, Freek; Kopačková, Veronika; Koucká, Lucie; van der Werff, Harald M. A.; van Ruitenbeek, Frank J. A.; Bakker, Wim H.

    2018-02-01

    The final product of a geologic remote sensing data analysis using multi spectral and hyperspectral images is a mineral (abundance) map. Multispectral data, such as ASTER, Landsat, SPOT, Sentinel-2, typically allow to determine qualitative estimates of what minerals are in a pixel, while hyperspectral data allow to quantify this. As input to most image classification or spectral processing approach, endmembers are required. An alternative approach to classification is to derive absorption feature characteristics such as the wavelength position of the deepest absorption, depth of the absorption and symmetry of the absorption feature from hyperspectral data. Two approaches are presented, tested and compared in this paper: the 'Wavelength Mapper' and the 'QuanTools'. Although these algorithms use a different mathematical solution to derive absorption feature wavelength and depth, and use different image post-processing, the results are consistent, comparable and reproducible. The wavelength images can be directly linked to mineral type and abundance, but more importantly also to mineral chemical composition and subtle changes thereof. This in turn allows to interpret hyperspectral data in terms of mineral chemistry changes which is a proxy to pressure-temperature of formation of minerals. We show the case of the Rodalquilar epithermal system of the southern Spanish Gabo de Gata volcanic area using HyMAP airborne hyperspectral images.

  16. 40Ar/39Ar ages of adularia from the Golden Cross, Neavesville, and Komata epithermal deposits, Hauraki Goldfield, New Zealand

    International Nuclear Information System (INIS)

    Mauk, J.L.; Hall, C.M.

    2004-01-01

    New 40 Ar/ 39 Ar ages of adularia from three epithermal vein deposits in the Hauraki Goldfield constrain when these deposits formed. Adularia from veins at Neavesville has 40 Ar/ 39 Ar plateau and isochron ages of 6.89 ± 0.02 and 6.86 ± 0.02 Ma, respectively, similar to the 40 Ar/ 39 Ar plateau and isochron ages of adularia from veins at Golden Cross of 6.96 ± 0.04 and 6.93 ± 0.03 Ma, respectively. In contrast, Komata mineralisation formed at 5.99 ± 0.02 to 6.07 ± 0.03 Ma, based on the 40 Ar/ 39 Ar isochron and plateau ages of the adularia in these veins, similar to the previously reported 6.0 Ma age of mineralisation at Waihi/Favona. These preliminary data suggest that mineralisation in the Hauraki Goldfields occurred episodically. (author). 19 refs., 3 figs., 1 tab

  17. Fluid inclusion and stable isotopes studies of epithermal gold-bearing veins in the SE Afar Rift (Djibouti)

    Science.gov (United States)

    Moussa, N.; Boiron, M. C.; Grassineau, N.; Fouquet, Y.; Le Gall, B.; Mohamed, J.

    2015-12-01

    The Afar rift results from the interaction of a number of actively-propagating tectono-magmatic axes. Recent field investigations in the SE Afar rift have emphasized the importance of hydrothermal system in rift-related volcanic complexes. Mineralization occur as gold-silver bearing veins and are associated with felsic volcanism. Late carbonate veins barren of sulfides and gold are common. The morphologies and textures of quartz show crustiform colloform banding, massive and breccias. Microthermometric measurements were made on quartz-hosted two phases (liquid + vapor) inclusions; mean homogenization temperature range from 150°C to 340°C and ice-melting temperatures range from -0.2° to 1.6°C indicating that inclusion solutions are dilute and contain 0.35 to 2.7 equivalent wt. % NaCl. Furthermore, δ18O and δ13C values from calcite range from 3.7 to 26.6 ‰ and -7.5 to 0.3‰, respectively. The presence of platy calcite and adularia indicate that boiling condition existed. This study shows that precious-metal deposition mainly occurred from hydrothermal fluids at 200°C at around 300 and 450 m below the present-day surface in a typical low-sulphidation epithermal environment.

  18. IER-297 CED-2: Final Design for Thermal/Epithermal eXperiments with Jemima Plates with Polyethylene and Hafnium

    Energy Technology Data Exchange (ETDEWEB)

    Nelson, A. J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Percher, C. M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Zywiec, W. J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Heinrichs, D. P. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2018-01-11

    This report presents the final design (CED-2) for IER-297, and focuses on 15 critical configurations using highly enriched uranium (HEU) Jemima plates moderated by polyethylene with and without hafnium diluent. The goal of the U.S. Nuclear Criticality Safety Program’s Thermal/Epithermal eXperiments (TEX) is to design and conduct new critical experiments to address high priority nuclear data needs from the nuclear criticality safety and nuclear data communities, with special emphasis on intermediate energy (0.625 eV – 100 keV) assemblies that can be easily modified to include various high priority diluent materials. The TEX (IER 184) CED-1 Report [1], completed in 2012, demonstrated the feasibility of meeting the TEX goals with two existing NCSP fissile assets, plutonium Zero Power Physics Reactor (ZPPR) plates and highly enriched uranium (HEU) Jemima plates. The first set of TEX experiments will focus on using the plutonium ZPPR plates with polyethylene moderator and tantalum diluents.

  19. Devonian conodonts from the Foča–Prača Paleozoic complex (Durmitor Nappe, southeastern Bosnia and Herzegovina

    Directory of Open Access Journals (Sweden)

    Bogdan Jurkovšek

    2011-06-01

    Full Text Available Conodont study of the Crna Rijeka borehole CR-17, positioned in the frontal part of the Durmitor Nappe (Foča – Prača Paleozoic complex, SE Bosnia and Herzegovina is presented. The obtained fauna indicates an Early-Middle Devonian age and due to poor preservation an identification at a generic level is possible only. The recovered conodont elements have a high Color Alteration Index (CAI = 6,5–7 indicating a degree of metamorphism corresponding to a temperature interval from 440 °C to 720 °C.

  20. Barents Sea Paleozoic basement and basin configurations: Crustal structure from deep seismic and potential field data

    Science.gov (United States)

    Aarseth, Iselin; Mjelde, Rolf; Breivik, Asbjørn Johan; Huismans, Ritske; Faleide, Jan Inge

    2016-04-01

    The Barents Sea is underlain by at least two different basement domains; the Caledonian in the west and the Timanian in the east. The transition between these two domains is not well constrained and contrasting interpretations have been published recently. Interpretations of new high-quality magnetic data covering most of the SW Barents Sea has challenged the Late Paleozoic basin configurations in the western and central Barents Sea as outlined in previous studies. Two regional ocean bottom seismic (OBS) profiles were acquired in 2014. This new dataset crosses the two major directions of Caledonian deformation proposed by different authors: N-S direction and SW-NE direction. Of particular importance are the high velocity anomalies related to Caledonian eclogites, revealing the location of Caledonian suture zones in the northern Barents Sea. One of the main objectives with this project is to locate the main Caledonian suture in the western Barents Sea, as well as the possible Barentsia-Baltica suture postulated further eastwards. The collapse of the Caledonian mountain range predominantly along these suture zones is expected to be tightly linked to the deposition of large thicknesses of Devonian erosional products, and later rifting is expected to be influenced by inheritance of Caledonian trends. The P-wave travel-time modelling is done by use of a combined ray-tracing and inversion scheme, and gravity- and magnetic modelling will be used to augment the seismic model. The preliminary results indicate high P-wave velocities (mostly over 4 km/s) close to the seafloor as well as high velocity (around 6 km/s) zones at shallow depths which are interpreted as volcanic sills. The crustal transects reveal areas of complex geology and velocity inversions. A low seismic impedance contrast between the sedimentary section and top crystalline basement makes identification of this interface uncertain. Depth to Moho mostly lies around 30 km, except in an area of rapid change in

  1. Paleozoic and Paleoproterozoic Zircon in Igneous Xenoliths Assimilated at Redoubt Volcano, Alaska

    Science.gov (United States)

    Bacon, C. R.; Vazquez, J. A.; Wooden, J. L.

    2010-12-01

    Historically active Redoubt Volcano is a basalt-to-dacite cone constructed upon the Jurassic-early Tertiary Alaska-Aleutian Range batholith. New SHRIMP-RG U-Pb age and trace-element concentration results for zircons from gabbroic xenoliths and crystal-rich andesitic mush from a late Pleistocene pyroclastic deposit indicate that ~310 Ma and ~1865 Ma igneous rocks underlie Redoubt at depth. Two gabbros have sharply terminated prismatic zircons that yield ages of ~310 Ma. Zircons from a crystal mush sample are overwhelmingly ~1865 Ma and appear rounded due to incomplete dissolution. Binary plots of element concentrations or ratios show clustering of data for ~310-Ma grains and markedly coherent trends for ~1865-Ma grains; e.g., ~310-Ma grains have higher Eu/Eu* than most of the ~1865-Ma grains, the majority of which form a narrow band of decreasing Eu/Eu* with increasing Hf content which suggests that ~1865-Ma zircons come from igneous source rocks. It is very unlikely that detrital zircons from a metasedimentary rock would have this level of homogeneity in age and composition. One gabbro contains abundant ~1865 Ma igneous zircons, ~300-310 Ma fluid-precipitated zircons characterized by very low U and Th concentrations and Th/U ratios, and uncommon ~100 Ma zircons. We propose that (1) ~310 Ma gabbro xenoliths from Redoubt Volcano belong to the same family of plutons dated by Aleinikoff et al. (USGS Circular 1016, 1988) and Gardner et al. (Geology, 1988) located ≥500 km to the northeast in basement rocks of the Wrangellia and Alexander terranes and (2) ~1865 Ma zircons are inherited from igneous rock, potentially from a continental fragment that possibly correlates with the Fort Simpson terrane or Great Bear magmatic zone of the Wopmay Orogen of northwestern Laurentia. Possibly, elements of these Paleoproterozoic terranes intersected the Paleozoic North American continental margin where they may have formed a component of the basement to the Wrangellia

  2. Rb-Sr ages and initial 87Sr/86Sr ratios of late paleozoic granitic rocks from northern Chile

    International Nuclear Information System (INIS)

    Shibata, Ken; Ishihara, Shunso; Ulriksen, C.E.

    1984-01-01

    Rb-Sr whole-rock isochron ages were determined on three suites of so-called Paleozoic granitic rocks from northern coastal Chile. The granitic rocks from the Valparaiso and Ci Funcho areas are dated as 296.3 +- 5.4 Ma and 262.2 +- 4.6 Ma, respectively, which are in accord with geologically estimated age. The rocks from the Chanaral area is dated as 212.8 +- 8.6 Ma, which is correlated close to the Triassic-Jurassic boundary age. A K-Ar age of 196 +- 6 Ma was obtained on biotite in granite from Esmeralda between Ci Funcho and Chanaral. These age results demonstrate that no Precambrian plutonism occurred in the studied area, and that so-called Paleozoic granitic rocks in the Ci Funcho-Chanaral area are divided into Permian and early Mesozoic in age. Initial 87 Sr/ 86 Sr ratios of the ilmenite-series granitic rocks from the coastal region are 0.70641 (Valparaiso), 0.70635 (Ci Funcho) and 0.70455 (Chanaral). These relatively low ratios deny substantial crustal contribution to the granitoids. The initial ratios of magnetite-series granitoids from porphyry- and manto-type mineralized areas (Chiquicamata, El Salvador and Tocopilla) are as low as 0.70344 to 0.70464. (author)

  3. Total petroleum systems of the Paleozoic and Jurassic, Greater Ghawar Uplift and adjoining provinces of central Saudi Arabia and northern Arabian-Persian Gulf

    Science.gov (United States)

    Pollastro, Richard M.

    2003-01-01

    The greater Paleozoic and Jurassic petroleum systems of the Arabian Peninsula form two of the most prolific petroleum-producing systems in the world. Source rocks of these systems extend throughout the eastern Arabian Peninsula and Arabian-Persian Gulf. Primary elements of these Paleozoic and Jurassic petroleum systems - source, reservoir, and seal rocks - are of great areal extent and exceptional quality. The combination of these regionally extensive, exceptional petroleum-system elements, and the formation of large subtle structural closures prior to, or coincident with, peak oil generation and migration, have produced oil and gas fields with reserve volumes second to none.

  4. The Stypsi-Megala Therma porphyry-epithermal mineralization, Lesvos Island, Greece: new mineralogical and geochemical data

    Science.gov (United States)

    Periferakis, Argyrios; Voudouris, Panagiotis; Melfos, Vasilios; Mavrogonatos, Constantinos; Alfieris, Dimitrios

    2017-04-01

    anomalies to those previously reported by [1] but also provide additional information in a series of elements: Cu (up to 843 ppm), Mo (up to 76 ppm), Au (up to 120 ppb), Pb (up to 339ppm), Zn (up to 815ppm), Se (up to 10ppm), Te (up to 4 ppm), Bi (up to 4 ppm) and Sn (up to 23 ppm). The Lesvos Island may be interpreted as the westward extension of the Eocene-Miocene Biga peninsula Cu-Au porphyry belt, with potential for future discoveries of Cu-Mo±Au deposits in the Aegean area. [1] Voudouris P, Alfieris D (2005) New porphyry-Cu±Mo occurrences in northeastern Aegean/Greece: Ore mineralogy and transition to epithermal environment. In: Mao J, Bierlein FP (eds) Mineral deposit research: Meeting the global challenge. Springer Verlag, 473-476; [2] Kontis E, Kelepertsis AE, Skounakis S (1994) Geochemistry and alteration facies associated with epithermal precious metal mineralization in an active geothermal system, northern Lesvos, Greece. Min Deposita, 29:430-433; [3] Muntean JL, Einaudi MT (2000) Porphyry Gold Deposits of the Refugio District, Maricunga Belt, Northern Chile. Econ. Geology, 95, 1445-1472.

  5. Lithological and Hydrothermal Alteration Mapping of Epithermal, Porphyry and Tourmaline Breccia Districts in the Argentine Andes Using ASTER Imagery

    Directory of Open Access Journals (Sweden)

    Francisco J. Testa

    2018-01-01

    Full Text Available The area of interest is located on the eastern flank of the Andean Cordillera, San Juan province, Argentina. The 3600 km2 area is characterized by Siluro-Devonian to Neogene sedimentary and igneous rocks and unconsolidated Quaternary sediments. Epithermal, porphyry-related, and magmatic-hydrothermal breccia-hosted ore deposits, common in this part of the Frontal Cordillera, are associated with various types of hydrothermal alteration assemblages. Kaolinite – alunite-rich argillic, quartz – illite-rich phyllic, epidote – chlorite – calcite-rich propylitic and silicic are the most common hydrothermal alteration assemblages in the study area. VNIR, SWIR and TIR ASTER data were used to characterize geological features on a portion of the Frontal Cordillera. Red-green-blue band combinations, band ratios, logical operations, mineral indices and principal component analysis were applied to successfully identify rock types and hydrothermal alteration zones in the study area. These techniques were used to enhance geological features to contrast different lithologies and zones with high concentrations of argillic, phyllic, propylitic alteration mineral assemblages and silicic altered rocks. Alteration minerals detected with portable short-wave infrared spectrometry in hand specimens confirmed the capability of ASTER to identify hydrothermal alteration assemblages. The results from field control areas confirmed the presence of those minerals in the areas classified by ASTER processing techniques and allowed mapping the same mineralogy where pixels had similar information. The current study proved ASTER processing techniques to be valuable mapping tools for geological reconnaissance of a large area of the Argentinean Frontal Cordillera, providing preliminary lithologic and hydrothermal alteration maps that are accurate as well as cost and time effective.

  6. Epithermal uranium deposits in a volcanogenic context: the example of Nopal 1 deposit, Sierra de Pena Blanca, Mexico

    Science.gov (United States)

    Calas, G.; Angiboust, S.; Fayek, M.; Camacho, A.; Allard, T.; Agrinier, P.

    2009-12-01

    The Peña Blanca molybdenum-uranium field (Chihuahua, Mexico) exhibits over 100 airborne anomalies hosted in tertiary ignimbritic ash-flow tuffs (44 Ma) overlying the Pozos conglomerate and a sequence of Cretaceous carbonate rocks. Uranium occurrences are associated with breccia zones at the intersection of two or more fault systems. Periodic reactivation of these structures associated with Basin and Range and Rio Grande tectonic events resulted in the mobilization of U and other elements by meteoric fluids heated by geothermal activity. Trace element geochemistry (U, Th, REE) provides evidence for local mobilization of uranium under oxidizing conditions. In addition, O- and H-isotope geochemistry of kaolinite, smectite, opal and calcite suggests that argillic alteration proceeded at shallow depth with meteoric water at 25-75 °C. Focussed along breccia zones, fluids precipitated several generations of pyrite and uraninite together with kaolinite, as in the Nopal 1 mine, indicating that mineralization and hydrothermal alteration of volcanic tuffs are contemporaneous. Low δ34S values (~ -24.5 ‰) of pyrites intimately associated with uraninite suggest that the reducing conditions at the origin of the U-mineralization arise from biological activity. Later, the uplift of Sierra Pena Blanca resulted in oxidation and remobilization of uranium, as confirmed by the spatial distribution of radiation-induced defect centers in kaolinites. These data show that tectonism and biogenic reducing conditions can play a major role in the formation and remobilization of uranium in epithermal deposits. By comparison with the other uranium deposits at Sierra Pena Blanca and nearby Sierra de Gomez, Nopal 1 deposit is one of the few deposits having retained a reduced uranium mineralization.

  7. The Totumo mud volcano and its near-shore marine sedimentological setting (North Colombia) - From sedimentary volcanism to epithermal mineralization

    Science.gov (United States)

    Dill, H. G.; Kaufhold, S.

    2018-04-01

    The Holocene mud volcano exposed at Totumo (younger than 4150 ± 50 yr BP) lines up together with some other landforms of its kind along the Caribbean Coast in northern Colombia. It currently vents a mud of the silicate-phosphate-bearing sulfur-sodium chloride type. The mud volcanoes evolved in an active continental margin setting of the South American Cordillera with high seismicity and affected by pervasive neotectonic structural disturbances. During the Neogene and Quaternary linear terrigenous shoreline sediments alternating with delta deposits evolved on this mobile crustal segment between the Andes and ancient Precambrian cratons. Meso- to microtidal sedimentary settings during transgression and progradation created meta- to instable sedimentary and petrophysical conditions (e.g. overpressure and gas-bearing bubble sands), favorable for the formation of mud volcanoes, whose lithofacies is subdivided into (1) footwall facies (detritus from metabasic, -pelitic source rocks), (2) mud volcano plus lateral facies (material from deep-seated hydrothermal sources, hydrocarbon plays, and brine reflux from the sea), (3) hanging wall facies, sand characterized by a strong longshore drift. The sedimentary volcanism in the area is characterized by different temperatures of formation: (1) pre-stage (oxides, garnet, alumosilicates, tourmaline, zircon, barite, Fe sulfides and -sulfates), light (Ca sulfates, calcite, quartz, feldspar) and clay minerals (kaolinite, mica, pyrophyllite, chlorite, vermiculite) are efficient tools to determine the source of mud, to subdivide the mud volcano system as to its facies and describe its physical-chemical regime as to the temperature of formation, pH and Eh values. The mud volcano system of Totumo bridges the gap between sedimentary "volcanism" and epithermal hot spring deposits of intermediate to high sulfidation and forms a useful "guide" to hydrocarbon accumulation.

  8. Quantitative Hydraulic Models Of Early Land Plants Provide Insight Into Middle Paleozoic Terrestrial Paleoenvironmental Conditions

    Science.gov (United States)

    Wilson, J. P.; Fischer, W. W.

    2010-12-01

    Fossil plants provide useful proxies of Earth’s climate because plants are closely connected, through physiology and morphology, to the environments in which they lived. Recent advances in quantitative hydraulic models of plant water transport provide new insight into the history of climate by allowing fossils to speak directly to environmental conditions based on preserved internal anatomy. We report results of a quantitative hydraulic model applied to one of the earliest terrestrial plants preserved in three dimensions, the ~396 million-year-old vascular plant Asteroxylon mackei. This model combines equations describing the rate of fluid flow through plant tissues with detailed observations of plant anatomy; this allows quantitative estimates of two critical aspects of plant function. First and foremost, results from these models quantify the supply of water to evaporative surfaces; second, results describe the ability of plant vascular systems to resist tensile damage from extreme environmental events, such as drought or frost. This approach permits quantitative comparisons of functional aspects of Asteroxylon with other extinct and extant plants, informs the quality of plant-based environmental proxies, and provides concrete data that can be input into climate models. Results indicate that despite their small size, water transport cells in Asteroxylon could supply a large volume of water to the plant's leaves--even greater than cells from some later-evolved seed plants. The smallest Asteroxylon tracheids have conductivities exceeding 0.015 m^2 / MPa * s, whereas Paleozoic conifer tracheids do not reach this threshold until they are three times wider. However, this increase in conductivity came at the cost of little to no adaptations for transport safety, placing the plant’s vegetative organs in jeopardy during drought events. Analysis of the thickness-to-span ratio of Asteroxylon’s tracheids suggests that environmental conditions of reduced relative

  9. Paleozoic evolution of active margin basins in the southern Central Andes (northwestern Argentina and northern Chile)

    Science.gov (United States)

    Bahlburg, H.; Breitkreuz, C.

    The geodynamic evolution of the Paleozoic continental margin of Gondwana in the region of the southern Central Andes is characterized by the westward progression of orogenic basin formation through time. The Ordovician basin in the northwest Argentinian Cordillera Oriental and Puna originated as an Early Ordovician back-arc basin. The contemporaneous magmatic arc of an east-dipping subduction zone was presumably located in northern Chile. In the back-arc basin, a ca. 3500 meter, fining-up volcaniclastic apron connected to the arc formed during the Arenigian. Increased subsidence in the late Arenigian allowed for the accomodation of large volumes of volcaniclastic turbidites during the Middle Ordovician. Subsidence and sedimentation were caused by the onset of collision between the para-autochthonous Arequipa Massif Terrane (AMT) and the South American margin at the Arenigian-Llanvirnian transition. This led to eastward thrusting of the arc complex over its back-arc basin and, consequently, to its transformation into a marine foreland basin. As a result of thrusting in the west, a flexural bulge formed in the east, leading to uplift and emergence of the Cordillera Oriental shelf during the Guandacol Event at the Arenigian-Llanvirnian transition. The basin fill was folded during the terminal collision of the AMT during the Oclóyic Orogeny (Ashgillian). The folded strata were intruded post-tectonically by the presumably Silurian granitoids of the "Faja Eruptiva de la Puna Oriental." The orogeny led to the formation of the positive area of the Arco Puneño. West of the Arco Puneño, a further marine basin developed during the Early Devonian, the eastern shelf of which occupied the area of the Cordillera Occidental, Depresión Preandina, and Precordillera. The corresponding deep marine turbidite basin was located in the region of the Cordillera de la Costa. Deposition continued until the basin fill was folded in the early Late Carboniferous Toco Orogeny. The basin

  10. Late-Paleozoic-Mesozoic deformational and deformation related metamorphic structures of Kuznetsk-Altai region

    Science.gov (United States)

    Zinoviev, Sergei

    2014-05-01

    Kuznetsk-Altai region is a part of the Central Asian Orogenic Belt. The nature and formation mechanisms of the observed structure of Kuznetsk-Altai region are interpreted by the author as the consequence of convergence of Tuva-Mongolian and Junggar lithospheric block structures and energy of collision interaction between the blocks of crust in Late-Paleozoic-Mesozoic period. Tectonic zoning of Kuznetsk-Altai region is based on the principle of adequate description of geological medium (without methods of 'primary' state recovery). The initial indication of this convergence is the crust thickening in the zone of collision. On the surface the mechanisms of lateral compression form a regional elevation; with this elevation growth the 'mountain roots' start growing. With an approach of blocks an interblock elevation is divided into various fragments, and these fragments interact in the manner of collision. The physical expression of collision mechanisms are periodic pulses of seismic activity. The main tectonic consequence of the block convergence and collision of interblock units is formation of an ensemble of regional structures of the deformation type on the basis of previous 'pre-collision' geological substratum [Chikov et al., 2012]. This ensemble includes: 1) allochthonous and autochthonous blocks of weakly deformed substratum; 2) folded (folded-thrust) systems; 3) dynamic metamorphism zones of regional shears and main faults. Characteristic of the main structures includes: the position of sedimentary, magmatic and PT-metamorphic rocks, the degree of rock dynamometamorphism and variety rock body deformation, as well as the styles and concentrations of mechanic deformations. 1) block terranes have weakly elongated or isometric shape in plane, and they are the systems of block structures of pre-collision substratum separated by the younger zones of interblock deformations. They stand out among the main deformation systems, and the smallest are included into the

  11. Characteristics of hydrothermal alteration mineralogy and geochemistry of igneous rocks from the epithermal Co-O mine and district, Eastern Mindanao (Philippines)

    Science.gov (United States)

    Sonntag, Iris; Hagemann, Steffen

    2010-05-01

    Detailed petrographic as well as hyperspectral analyses using PIMA (Portable Infrared Mineral Analyser) and geochemical (major, trace and rare earth elements) studies were conducted on samples of the epithermal, low sulfidation Co-O mine (47,869 ounces gold produced in 2009 with an average grade of 13.3 g/t gold) and district in Eastern Mindanao (Philippines). The aims of the study were to unravel the petrogenetic origin of the various volcanic (host rocks) and intrusive rocks (potential fluid driver) as well as their relationship and influence on the hydrothermal alteration zoning and fluid chemistry. The auriferous veins at the Co-O mine were formed during two hydrothermal stages associated with the district wide D1 and D2 deformation events. Gold in stage 1 quartz veins is in equilibrium with galena and sphalerite, whereas in stage 2 it is associated with pyrite. Auriferous quartz veins of stage 1 reflect temperatures below 250° C or strong variations in pH and fO2 at higher temperatures, due to potential involvement of acidic gas or meteoric water. Cathodoluminescense studies revealed strong zonation of quartz associated with Au, presumably related to changes in the Al content, which is influenced by the pH. Plumose textures indicate times of rapid deposition, whereas saccharoidal quartz grains are related to potential calcite replacement. The geology of the Co-O mine and district is dominated by Miocene volcanic rocks (basic to intermediate flows and pyroclastics units), which are partly covered by Pliocene volcanic rocks and late Oligocene to Miocene limestones. The Miocene units are intruded by diorite (presumably Miocene in age). The epithermal mineralization event may be related to diorite intrusions. The geochemistry of all igneous rocks in the district is defined by a sub-alkaline affinity and is low to medium K in composition. Most units are related to a Miocene subduction zone with westward subduction, whereas the younger Pliocene rocks are related to

  12. In vitro biological effectiveness of JRR-4 epithermal neutron beam. Experiment under free air beam and in water phantom. Cooperative research

    International Nuclear Information System (INIS)

    Yamamoto, Tetsuya; Matsumura, Akira; Nose, Tadao; Yamamoto, Kazuyoshi; Kumada, Hiroaki; Kishi, Toshiaki; Hori, Naohiko; Torii, Yoshiya; Horiguchi, Yoji

    2002-05-01

    The surviving curve and the biological effectiveness factor of dose components generated in boron neutron capture therapy (BNCT) were separately determined in neutron beams at Japan Research Reactor No.4. Surviving fraction of V79 Chinese hamster cell with or without 10 B was obtained using an epithermal neutron beam (ENB), a mixed thermal-epithermal neutron beam (TNB-1), and a thermal neutron beam (TNB-2), which were used or planned to use for BNCT clinical trial. The cell killing effect of these neutron beams with or without the presence of 10 B depended highly on the neutron beam used, according to the epithermal and fast neutron content in the beam. The biological effectiveness factor values of the boron capture reaction for ENB, TNB-1 and TNB-2 were 3.99±0.24, 3.04±0.19 and 1.43±0.08, respectively. The biological effectiveness factor values of the high-LET dose components based on the hydrogen recoils and the nitrogen capture reaction were 2.50±0.32, 2.34±0.30 and 2.17±0.28 for ENB, TNB-1 and TNB-2, respectively. The biological effectiveness factor values of the neutron and photon components were 1.22±0.16, 1.23±0.16 and 1.21±0.16, respectively. The depth function of biological effectiveness factor in water phantom and the difference in biological effectiveness factor among boron compounds were also determined. The experimental determination of biological effectiveness factor outlined in this paper is applicable to the dose calculation for each dose component of the neutron beams and contribute to an accurate biological effectiveness factor as comparison with a neutron beam at a different facility employed in ongoing and planned BNCT clinical trials. (author)

  13. Sensitivity of reactor integral parameters to #betta##betta# parameter of resolved resonances of fertile isotopes and to the α values, in thermal and epithermal spectra

    International Nuclear Information System (INIS)

    Barroso, D.E.G.

    1982-01-01

    A sensitivity analysis of reactor integral parameter to more 10% variation in the resolved resonance parameters #betta##betta# of the fertile isotope and the variations of more 10% in the α values (#betta# sub(#betta#)/#betta# sub(f)) of fissile isotopes of PWR fuel elements, is done. The analysis is made with thermal and epithermal spectra, those last generated in a fuel cell with low V sub(M)/V sub(F). The HAMMER system, the interface programs HELP and LITHE and the HAMMER computer codes, were used as a base for this study. (E.G.) [pt

  14. Internal-standard method for the determination of uranium, thorium, lanthanum and europium in carbonaceous shale and monazite by epithermal neutron activation analysis

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Shuenn-Gang; Tsai, Hui-Tuh; Wu, Shaw-Chii [Institute of Nuclear Energy Research, Lung-Tan (Taiwan, Republic of China)

    1981-10-03

    An internal-standard method was applied for the determination of uranium, thorium, lanthanum and europium is carbonaceous shale samples and monazite sand by epithermal neutron activation analysis using gold as an internal standard element. The samples were irradiated in a zero-power reactor at the Institute of Nuclear Energy Research and measured with a high-resolution Ge(Li) detector. The detection limit is 0.1 ppm for uranium and europium, 1 ppm for thorium, 5 ppm for lanthanum, and the realative error of all elements is within +-2.6%.

  15. TECTONIC POSITION OF MARBLE MELANGES IN THE EARLY PALEOZOIC ACCRETION-COLLISIONAL SYSTEM OF THE WESTERN PRIBAIKALIE

    Directory of Open Access Journals (Sweden)

    V. S. Fedorovsky

    2014-01-01

    Full Text Available The Early Paleozoic collisional system located in the Olkhon region at the western shores of Lake Baikal resulted from collision of the Siberian paleocontinent and a complex aggregate composed by fragments of a microcontinent, island arcs, back-arc structures and accretionary prisms. The main events were associated with complete manifestation of shear tectogenesis initiated by oblique collision. The current structure includes tectonically displaced components of ancient geodynamic systems that used to have been located dozens and hundreds of kilometres apart. Horizontal amplitudes of tectonic displacement seem to have been quite high; however, numerical data are still lacking to support this conclusion. Information about the structure of the upper crust in the Paleozoic is also lacking as only deep metamorphic rocks (varying from epidote-amphibolite to granulite facies are currently outcropped. Formations comprising the collisional collage are significantly different in composition and protoliths, and combinations of numerous shifted beds give evidence of a 'bulldozer' effect caused by the collisional shock followed by movements of crushed components of the ocean-continent zone along the margin of the Siberian paleocontinent. As evidenced by the recent cross-section, deep horizons of the Early Paleozoic crust comprise the collisional system between the Siberian craton and the Olkhon composite terrain. A permanent inclusion in the collisional combinations of rocks are unusual synmetamorphic injected bodies of carbonate rocks. Such rocks comprise two groups, marble melanges and crustal carbonate melted rocks. Obviously, carbonate rocks (that composed the original layers and horizons of stratified beds can become less viscous to a certain degree at some locations during the process of oblique collision and acquire unusual properties and can thus intrude into the surrounding rocks of silicate composition. Such carbonate rocks behave as protrusions

  16. Reactor AQUILON. The hardening of neutron spectrum in natural uranium rods, with a computation of epithermal fissions (1961); Pile AQUILON. Durcissement du spectre des neutrons dans les barreaux d'uranium et calcul des fissions epithermiques (1961)

    Energy Technology Data Exchange (ETDEWEB)

    Durand -Smet, R; Lourme, P [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires

    1961-07-01

    - Microscopic flux measurements in reactor Aquilon have allowed to investigate the thermal and epithermal flux distribution in natural uranium rods, then to obtain the neutron spectrum variations in uranium, Wescott '{beta}' term of the average spectrum in the rod, and the ratio of epithermal to therma fissions. A new definition for the infinite multiplication factor is proposed in annex, which takes into account epithermal parameters. (authors) [French] - Un certain nombre de mesures effectuees dans la pile Aquilon ont permis d'etablir la distribution fine des flux thermique et epithermique dans les barreaux d'uranium, et d'en deduire les variations du spectre des neutrons dans l'uranium, le terme {beta} du spectre de Wescott moyen dans le barreau et le nombre de fissions epithermiques. En annexe, il est propose une definition nouvelle du coefficient de multiplication infini, qui fait intervenir les parametres epithermiques. (auteurs)

  17. Sedimentological aspects of four Lower-Paleozoic formations in the northern part of the province of León (Spain)

    NARCIS (Netherlands)

    Oele, E.

    1964-01-01

    This paper deals with the sedimentary structures and sedimentary petrography of the four lowermost formations of the Paleozoic as developed in the Northern part of the Province of León (Cantabrian Mountains, Spain). Three of the four formations have a detrital character, and one consists of

  18. Fission track analysis and evolution of mesozoic-paleozoic hydrocarbon resource-rocks headed in Northern Jiangsu-South Yellow sea basin

    International Nuclear Information System (INIS)

    Xu Hong; Cai Qianzhong; Sun Heqing; Guo Zhenxuan; Yan Guijing; Dai Jing; Liu Dongying

    2008-01-01

    Fission track data of different geologic epoches from Binhai salient, Yancheng sag, Haian sag, Baiju sag, Gaoyou sag, Hongze sag and Jinhu sag of northern Jiangsu basin and seismic data from Laoshan uplift in South Yellow Sea basin and evolution of Paleozoic hydrocarbon resource-rocks headed in the Northern Jiangsu-South Yellow Sea basin were studied. Results indicate that Binhai salient uplifted in 38-15 Ma, forming 'structure uplifting model', Paleozoic hydrocarbon resource-rocks have the appearance of 'different layers but identical mature, different layers but identical temperature' with Laoshan uplift. All sags have the characters of 'long time heating model', and sedimentations in Cenozoic were exploited by 2 km. Mesozoic-Paleozoic hydrocarbon resource- rocks of Laoshan uplift get ahead of 10 km. Structure evolution was compared with Binhai salient. According to the modeling results of secondary hydrocarbon generation, Mesozoic-Paleozoic hydrocarbon resource-rocks of Laoshan uplift have the good reservoir potentiality and probably become an important new window for sea oil and gas exploration. (authors)

  19. Application of magnetic susceptibility as a paleoclimatic proxy on Paleozoic sedimentary rocks and characterization of the magnetic signal – IGCP-580 projects and event

    Czech Academy of Sciences Publication Activity Database

    da Silva, A-Ch.; Whalen, M. T.; Hladil, Jindřich; Koptíková, Leona; Chen, D.; Spassov, S.; Boulvain, F.; Devleeschouwer, X.

    2014-01-01

    Roč. 37, č. 2 (2014), s. 87-95 ISSN 0705-3797 Institutional support: RVO:67985831 Keywords : rock magnetism * high-resolution stratigraphy * palaeoclimatic archives * computing * Paleozoic * Phanerozoic * Recent Subject RIV: DE - Earth Magnetism, Geodesy, Geography Impact factor: 2.000, year: 2014 http://www.episodes.co.in/contents/2014/june/pp87-95.pdf

  20. Tectono-thermal Evolution of the Lower Paleozoic Petroleum Source Rocks in the Southern Lublin Trough: Implications for Shale Gas Exploration from Maturity Modelling

    Science.gov (United States)

    Botor, Dariusz

    2018-03-01

    The Lower Paleozoic basins of eastern Poland have recently been the focus of intensive exploration for shale gas. In the Lublin Basin potential unconventional play is related to Lower Silurian source rocks. In order to assess petroleum charge history of these shale gas reservoirs, 1-D maturity modeling has been performed. In the Łopiennik IG-1 well, which is the only well that penetrated Lower Paleozoic strata in the study area, the uniform vitrinite reflectance values within the Paleozoic section are interpreted as being mainly the result of higher heat flow in the Late Carboniferous to Early Permian times and 3500 m thick overburden eroded due to the Variscan inversion. Moreover, our model has been supported by zircon helium and apatite fission track dating. The Lower Paleozoic strata in the study area reached maximum temperature in the Late Carboniferous time. Accomplished tectono-thermal model allowed establishing that petroleum generation in the Lower Silurian source rocks developed mainly in the Devonian - Carboniferous period. Whereas, during Mesozoic burial, hydrocarbon generation processes did not develop again. This has negative influence on potential durability of shale gas reservoirs.

  1. Status report: numerical modeling of ground-water flow in the Paleozoic formations, western Paradox Basin, Utah

    International Nuclear Information System (INIS)

    Dunbar, D.B.; Thackston, J.W.

    1985-10-01

    A three-dimensional finite-difference numerical model was applied to simulate the ground-water flow pattern in Paleozoic strata within the western Paradox Basin region. The primary purpose of the modeling was to test the present conceptual hydrogeologic model and evaluate data deficiencies. All available data on ground-water hydrology, although sparse in this area, were utilized as input to the model. Permeability and potentiometric levels were estimated from petroleum company drill-stem tests and water-supply wells; formation thicknesses were obtained from geologic correlation of borehole geophysical logs. Hydrogeologic judgment weighed heavily in the assignment of hydrologic values to geologic features for this preliminary modeling study. Calibration of the model was accomplished through trial-and-error matching of simulated potentiometric contours with available head data. Hypothetical flow patterns, flux rates, recharge amounts, and surface discharge amounts were produced by the model. 34 refs., 17 figs., 3 tabs

  2. Geochemistry and chronology of the early Paleozoic diorites and granites in the Huangtupo volcanogenic massive sulfide (VMS) deposit, Eastern Tianshan, NW China: Implications for petrogenesis and geodynamic setting

    Science.gov (United States)

    Zheng, Jiahao; Chai, Fengmei; Feng, Wanyi; Yang, Fuquan; Shen, Ping

    2018-03-01

    The Eastern Tianshan orogen contains many late Paleozoic porphyry Cu and magmatic Cu-Ni deposits. Recent studies demonstrate that several early Paleozoic volcanogenic massive sulfide (VMS) Cu-polymetallic and porphyry Cu deposits were discovered in the northern part of Eastern Tianshan. This study presents zircon U-Pb, whole-rock geochemical, and Sr-Nd isotopic data for granites and diorites from the Huangtupo VMS Cu-Zn deposit, northern part of the Eastern Tianshan. Our results can provide constraints on the genesis of intermediate and felsic intrusions as well as early Paleozoic geodynamic setting of the northern part of Eastern Tianshan. LA-ICP-MS zircon U-Pb analyses suggest that the granites and diorites were formed at 435 ± 2 Ma and 440 ± 2 Ma, respectively. Geochemical characteristics suggest that the Huangtupo granites and diorites are metaluminous rocks, exhibiting typical subduction-related features such as enrichment in LILE and LREE and depletion in HFSE. The diorites have moderate Mg#, positive εNd(t) values (+6.4 to +7.3), and young Nd model ages, indicative of a depleted mantle origin. The granites exhibit mineral assemblages and geochemical characteristics of I-type granites, and they have positive εNd(t) values (+6.7 to +10.2) and young Nd model ages, suggesting a juvenile crust origin. The early Paleozoic VMS Cu-polymetallic and porphyry Cu deposits in the northern part of Eastern Tianshan were genetically related. The formation of the early Paleozoic magmatic rocks as well as VMS and porphyry Cu deposits in the northern part of Eastern Tianshan was due to a southward subduction of the Junggar oceanic plate.

  3. A review on late Paleozoic ice-related erosional landforms in the Paraná Basin: origin and paleogeographical implications

    Directory of Open Access Journals (Sweden)

    Eduardo Luiz Menozzo da Rosa

    Full Text Available ABSTRACT: The Late Paleozoic Ice Age is recorded in the Paraná Basin as glacial deposits, deformational features and ice-related erosional landforms of the Itararé Group. Erosional landforms are often employed to build paleogeographic models that depict the location of ice masses and paleo ice-flow directions. This paper provides a review of the literature and new data on micro- to meso-scale ice-related, erosional landforms of the Paraná Basin. Examined landforms can be placed into four broad categories based on their mode of origin. Subglacial landforms on rigid substrates occur on the Precambrian basement or on older units in the Paraná Basin. They include streamlined landforms and striated pavements formed by abrasion and/or plucking beneath advancing glaciers. Subglacial landforms on soft beds are intraformational surfaces generated by erosion and deformation of unconsolidated deposits when overridden by glaciers. Ice-keel scour marks are soft-sediment striated/grooved landforms developed by the scouring of free-floating ice masses on underlying sediments. Striated clast pavements are horizons containing aligned clasts that are abraded subglacially due to the advance of glaciers on unconsolidated deposits. Only those erosional landforms formed subglacially can be used as reliable paleo ice-flow indicators. Based on these data, the paleogeography of the Paraná Basin during the Late Paleozoic Ice Age fits into a model of several glacial lobes derived from topographically-controlled ice spreading centers located around the basin instead of a single continental ice sheet.

  4. Impedance-matching hearing in Paleozoic reptiles: evidence of advanced sensory perception at an early stage of amniote evolution.

    Directory of Open Access Journals (Sweden)

    Johannes Müller

    Full Text Available BACKGROUND: Insights into the onset of evolutionary novelties are key to the understanding of amniote origins and diversification. The possession of an impedance-matching tympanic middle ear is characteristic of all terrestrial vertebrates with a sophisticated hearing sense and an adaptively important feature of many modern terrestrial vertebrates. Whereas tympanic ears seem to have evolved multiple times within tetrapods, especially among crown-group members such as frogs, mammals, squamates, turtles, crocodiles, and birds, the presence of true tympanic ears has never been recorded in a Paleozoic amniote, suggesting they evolved fairly recently in amniote history. METHODOLOGY/PRINCIPAL FINDINGS: In the present study, we performed a morphological examination and a phylogenetic analysis of poorly known parareptiles from the Middle Permian of the Mezen River Basin in Russia. We recovered a well-supported clade that is characterized by a unique cheek morphology indicative of a tympanum stretching across large parts of the temporal region to an extent not seen in other amniotes, fossil or extant, and a braincase specialized in showing modifications clearly related to an increase in auditory function, unlike the braincase of any other Paleozoic tetrapod. In addition, we estimated the ratio of the tympanum area relative to the stapedial footplate for the basalmost taxon of the clade, which, at 23:1, is in close correspondence to that of modern amniotes capable of efficient impedance-matching hearing. CONCLUSIONS/SIGNIFICANCE: Using modern amniotes as analogues, the possession of an impedance-matching middle ear in these parareptiles suggests unique ecological adaptations potentially related to living in dim-light environments. More importantly, our results demonstrate that already at an early stage of amniote diversification, and prior to the Permo-Triassic extinction event, the complexity of terrestrial vertebrate ecosystems had reached a level that

  5. The Juchatengo complex: an upper-level ophiolite assemblage of late Paleozoic age in Oaxaca, southern Mexico

    Science.gov (United States)

    Grajales-Nishimura, José Manuel; Ramos-Arias, Mario Alfredo; Solari, Luigi; Murillo-Muñetón, Gustavo; Centeno-García, Elena; Schaaf, Peter; Torres-Vargas, Ricardo

    2018-04-01

    The Juchatengo complex (JC) suite is located between the Proterozoic Oaxacan complex to the north and the Xolapa complex to the south, and was amalgamated by late Paleozoic magmatism. It consists of mafic and sedimentary rocks that have oceanic affinities, with internal pseudostratigraphic, structural and metamorphic characteristics, which resemble a typical upper-level ophiolite assemblage. New U-Pb zircon and previous hornblende K-Ar analyses yield ages of ca. 291-313 Ma (U-Pb) for plagiogranites and ca. 282-277 Ma for tonalites intruding the entire sequence, including pelagic sediments at the top, with a maximum deposition age of ca. 278 Ma and noteworthy local provenance. These data constrain the age of the JC to the Late Pennsylvanian-Early Permian period. Hf isotopic analyses obtained from zircons in the JC plagiogranite and tonalite show that they come from a similar primitive mantle source (176Hf/177Hf: 0.282539-0.283091; ƐHf(t): + 3.2 to + 15.0). ƐHf(t) values from near 0 to - 2.8 in the tonalites indicate a contribution from the continental crust. Trace elements and REE patterns in whole rock and zircons point to a primitive mantle source for differentiated mafic, plagiogranite dykes and tonalitic plutons. Geochronological and geochemical data address the generation of new oceanic crust above the subduction zone, probably in a backarc setting. In this tectonic scenario, the JC ophiolite originated due to the convergence of the paleo-Pacific plate below the already integrated Oaxacan and Acatlán complexes in western Pangea. The dextral displacement places the deformation in a transtensional regime during the late Paleozoic age.

  6. Standardization of thermal and epithermal INAA methods for simultaneous determination of U and Th in mixed oxide samples

    International Nuclear Information System (INIS)

    Acharya, R.; Pujari, P.K.; Chandra, Ruma

    2010-01-01

    Full text: Uranium and thorium are important fuel materials for nuclear power program. In recent years utilization of thoria based fuel has assumed significance due to higher energy requirements. Thorium based mixed oxide is the proposed fuel for Advanced Heavy Water Reactors (AHWR). In this respect, studies are carried out through preparation of natural U and Th mixed oxides by powder metallurgical route, wherein composition of U and Th is specific and requires strict control in terms their contents and homogeneity in the mixture. Stringent chemical quality control necessitates compositional characterization of the fuel material i.e. accurate and precise determination of U and Th. A suitable method which does not need any chemical dissolution and yields high precision results with minima sample handling is desirable. Instrumental neutron activation analysis (INAA) using reactor neutron is the technique of choice. In view of this, INAA methods namely thermal lNAA (TNAA) (utilizing whole reactor neutrons) and epithermal INAA (ENAA) (utilizing epicadmium neutrons) were standardized for the determination of U and Th in presence of each other in mixed oxide samples. In the present work pneumatic carrier facility (PCF) of Dhruva reactor and self-serve facility of CIRUS reactor were used for TNAA and ENAA respectively. Standards, synthetic samples and mixed oxide samples prepared in cellulose matrix, were irradiated for 1 minute at PCF of Dhruva reactor and for 1 hour at CIRUS reactor under cadmium cover (0.5 mm). Radioactive assay was carried out using 40% relative efficiency HPGe detector. Peak areas under the full energy peaks were evaluated by peak fit method using the PHAST software. Both activation and daughter products of U ( 239 U, 74.6 keV and 239 Np, 277 keV) and Th ( 233 Th, 86 keV and 233 Pa, 312 keV) were used for their concentration determination. The method was validated by analyzing synthetic mixed oxide samples (6-48%U-Th mixed oxide). The % deviations

  7. Sodium storage in deep paleoweathering profiles beneath the Paleozoic-Triassic unconformity

    Science.gov (United States)

    Thiry, M.; Parcerisa, D.; Ricordel-Prognon, C.; Schmitt, J.-M.

    2009-04-01

    in potassium. The Na+ enrichment is most likely linked with the peculiar geochemical setting of the Triassic environment where for instance halite moulds are very common in transgressive epicontinental deposits. The leaching of such salts, the role of salty marine aerosols, or a periodic/episodic contribution of seawater or evaporative solutions may be equally invoked. Mass balance Taking into account the surpergene origin of albitization and its widespread development on the Paleozoic basement rocks (from Morocco to Scandinavia) means that high amounts of Na+ have been stored in the deep paleoweathering profiles of the Triassic continents. This sodium storage in weathering profiles has to be taken in consideration in addition to the major sodium chloride accumulation in the basins during the Permo-Triassic times. Further investigations are needed to demonstrate the extent of these paleoweathering profiles and then to estimate the amount of this continental sodium storage. References Cathelineau M (1986) The hydrothermal alkali metasomatism effects on granitic rocks: Quartz dissolution and related sub-solidus changes. Jour. Petrol., 27: 945-965. Hay, W.W.; Migdisov, A.; Balukhovsky, A.N.; Wold, C.N.; Flogel, S., Soding, E. (2006) Evaporites and the salinity of the ocean during the Phanerozoic: Implications for climate, ocean circulation and life. Palaeogeography, Palaeoclimatology, Palaeoecology, 240/1-2: 3-46. Parcerisa D., Thiry M., Schmitt J.-M. (2009) Albitisation related to the Triassic unconformity in igneous rocks of the Morvan Massif (France), International Journal of Earth Sciences, DOI: 10.1007/s00531-008-0405-1. Petersson J, Eliasson T (1997) Mineral evolution and element mobility during episyenitization (dequartzification) and albitization in the postkinematic Bohus granite, southwest Sweden. Lithos, 42: 123-146. Ricordel C, Parcerisa D, Thiry M, Moreau M-G, Gómez-Gras D (2007) Triassic magnetic overprints related to albitization in granites from the

  8. Mineralogical, stable isotope, and fluid inclusion studies of spatially related porphyry Cu and epithermal Au-Te mineralization, Fakos Peninsula, Limnos Island, Greece

    Science.gov (United States)

    Fornadel, Andrew P.; Voudouris, Panagiotis Ch.; Spry, Paul G.; Melfos, Vasilios

    2012-05-01

    The Fakos porphyry Cu and epithermal Au-Te deposit, Limnos Island, Greece, is hosted in a ~20 Ma quartz monzonite and shoshonitic subvolcanic rocks that intruded middle Eocene to lower Miocene sedimentary basement rocks. Metallic mineralization formed in three stages in quartz and quartz-calcite veins. Early porphyry-style (Stage 1) metallic minerals consist of pyrite, chalcopyrite, galena, bornite, sphalerite, molybdenite, and iron oxides, which are surrounded by halos of potassic and propylitic alteration. Stage 2 mineralization is composed mostly of quartz-tourmaline veins associated with sericitic alteration and disseminated pyrite and molybdenite, whereas Stage 3, epithermal-style mineralization is characterized by polymetallic veins containing pyrite, chalcopyrite, sphalerite, galena, enargite, bournonite, tetrahedrite-tennantite, hessite, petzite, altaite, an unknown cervelleite-like Ag-telluride, native Au, and Au-Ag alloy. Stage 3 veins are spatially associated with sericitic and argillic alteration. Fluid inclusions in quartz from Stage 1 (porphyry-style) mineralization contain five types of inclusions. Type I, liquid-vapor inclusions, which homogenize at temperatures ranging from 189.5°C to 403.3°C have salinities of 14.8 to 19.9 wt. % NaCl equiv. Type II, liquid-vapor-NaCl, Type III liquid-vapor-NaCl-XCl2 (where XCl is an unknown chloride phase, likely CaCl2), and Type IV, liquid-vapor-hematite ± NaCl homogenize to the liquid phase by liquid-vapor homogenization or by daughter crystal dissolution at temperatures of 209.3 to 740.5 °C, 267.6 to 780.8 °C, and 357.9 to 684.2 °C, respectively, and, Type V, vapor-rich inclusions. Stage 2 veins are devoid of interpretable fluid inclusions. Quartz from Stage 3 (epithermal-style) veins contains two types of fluid inclusions, Type I, liquid-vapor inclusions that homogenize to the liquid phase (191.6 to 310.0 °C) with salinities of 1.40 to 9.73 wt. % NaCl equiv., and Type II, vapor-rich inclusions. Mixing

  9. Use of boron nitride for neutron spectrum characterization and cross-section validation in the epithermal range through integral activation measurements

    Energy Technology Data Exchange (ETDEWEB)

    Radulović, Vladimir, E-mail: vladimir.radulovic@ijs.si [Jožef Stefan Institute, Jamova cesta 39, SI-1000 Ljubljana (Slovenia); Trkov, Andrej [Jožef Stefan Institute, Jamova cesta 39, SI-1000 Ljubljana (Slovenia); IAEA, Vienna International Centre, PO Box 100, A-1400 Vienna (Austria); Jaćimović, Radojko [Jožef Stefan Institute, Jamova cesta 39, SI-1000 Ljubljana (Slovenia); Gregoire, Gilles; Destouches, Christophe [CEA, DEN, DER, Instrumentation Sensors and Dosimetry Laboratory, Cadarache, F-13108 St. Paul-Lez-Durance (France)

    2016-12-21

    A recent experimental irradiation and measurement campaign using containers made from boron nitride (BN) at the Jožef Stefan Institute (JSI) TRIGA Mark II reactor in Ljubljana, Slovenia, has shown the applicability of BN for neutron spectrum characterization and cross-section validation in the epithermal range through integral activation measurements. The first part of the paper focuses on the determination of the transmission function of a BN container through Monte Carlo calculations and experimental measurements. The second part presents the process of tayloring the sensitivity of integral activation measurements to specific needs and a selection of suitable radiative capture reactions for neutron spectrum characterization in the epithermal range. A BN container used in our experiments and its qualitative effect on the neutron spectrum in the irradiation position employed is displayed in the Graphical abstract. - Graphical abstract: Neutron spectra inside the JSI TRIGA Mark II PT irradiation position, obtained with a Monte Carlo calculation: blue: unperturbed, green inside a BN container, of wall thickness 4 mm, 13 mm in diameter and 14 mm in height.

  10. Use of boron nitride for neutron spectrum characterization and cross-section validation in the epithermal range through integral activation measurements

    International Nuclear Information System (INIS)

    Radulović, Vladimir; Trkov, Andrej; Jaćimović, Radojko; Gregoire, Gilles; Destouches, Christophe

    2016-01-01

    A recent experimental irradiation and measurement campaign using containers made from boron nitride (BN) at the Jožef Stefan Institute (JSI) TRIGA Mark II reactor in Ljubljana, Slovenia, has shown the applicability of BN for neutron spectrum characterization and cross-section validation in the epithermal range through integral activation measurements. The first part of the paper focuses on the determination of the transmission function of a BN container through Monte Carlo calculations and experimental measurements. The second part presents the process of tayloring the sensitivity of integral activation measurements to specific needs and a selection of suitable radiative capture reactions for neutron spectrum characterization in the epithermal range. A BN container used in our experiments and its qualitative effect on the neutron spectrum in the irradiation position employed is displayed in the Graphical abstract. - Graphical abstract: Neutron spectra inside the JSI TRIGA Mark II PT irradiation position, obtained with a Monte Carlo calculation: blue: unperturbed, green inside a BN container, of wall thickness 4 mm, 13 mm in diameter and 14 mm in height.

  11. The Marianas-San Marcos vein system: characteristics of a shallow low sulfidation epithermal Au-Ag deposit in the Cerro Negro district, Deseado Massif, Patagonia, Argentina

    Science.gov (United States)

    Vidal, Conrado Permuy; Guido, Diego M.; Jovic, Sebastián M.; Bodnar, Robert J.; Moncada, Daniel; Melgarejo, Joan Carles; Hames, Willis

    2016-08-01

    The Cerro Negro district, within the Argentinian Deseado Massif province, has become one of the most significant recent epithermal discoveries, with estimated reserves plus resources of ˜6.7 Moz Au equivalent. The Marianas-San Marcos vein system contains about 70 % of the Au-Ag resources in the district. Mineralization consists of Upper Jurassic (155 Ma) epithermal Au- and Ag-rich veins of low to intermediate sulfidation style, hosted in and genetically related to Jurassic intermediate composition volcanic rocks (159-156 Ma). Veins have a complex infill history, represented by ten stages with clear crosscutting relationships that can be summarized in four main episodes: a low volume, metal-rich initial episode (E1), an extended banded quartz episode with minor mineralization (E2), a barren waning stage episode (E3), and a silver-rich late tectonic-hydrothermal episode (E4). The first three episodes are interpreted to have formed at the same time and probably from fluids of similar composition: a 290-230 °C fluid dominated by meteoric and volcanic waters (-3‰ to -0‰ δ18Owater), with geothermal features. The last tectonic-hydrothermal mineralization episode (E4), interpreted to have formed at lower temperatures, could be related to this late tectonic and hydrothermal activity.

  12. The epithermal critical experiments; Experiences critiques avec des neutrons epitliermiques; Nadteplovye kriticheskie ehksperimenty; Experimentos criticos con neutrones epitermicos

    Energy Technology Data Exchange (ETDEWEB)

    Morewitz, H A; Carpenter, S O [Atomics International, Canoga Park, CA (United States)

    1962-03-15

    The epithermal critical experiments. The present phase of the advanced-epithermal-thorium-reactor programme consists of integral-reactor-physic s experiments designed to provide neutron-cross-section information in the 10-MeV to 1-keV range. A series of nine, multi-region, slow-fast, pseudospherica l critical assemblies of the honey- comb, split-table type are being studied. So far, three assemblies have' been run. The outer driver-decouple r region drives an interior U{sup 233}-Th fuelled spherical test region whose neutron-flux spectrum is successively degraded by increasing the graphite moderator to fuel ratio. A square-wave oscillator experiment defines the central reactivity worths of forty small samples of different materials to 10{sup -8} {Delta}k for each assembly. Additionally, intercalibrated artificial neutron sources are oscillated to determine the various central neutron importance functions. The spectra are obtained by fission-counter measurements with calibrated foils of different thresholds and by a Li{sup 6}-solid-state- counter sandwich spectrometer. A digital computer routine will be used to compile all measurements into a self-consistent library of spectrum averaged cross-sections. (author) [French] La phase actuelle du programme de reacteur au thorium a neutrons epithermiques comprend des experiences integrales de physique des reacteurs pour obtenir des renseignements sur les sections efficaces neutroniques pour la gamme d'energie comprise entre 1 keV et 10 MeV. Les auteurs etudient une serie de neuf ensembles critiques pseudospheriques, a plusieurs regions, a couplage neutrons lents et neutrons rapides du type a alveoles et a coeur divise. A ce jour, trois de ces ensembles ont ete mis en service. La region exterieure, mettant en service ou hors service, commande une zone d'essai interieure de forme spherique ou le combustible est constitue de {sup 233}U-Th, dont le spectre du flux de neutrons est degrade progressivement par augmentation du

  13. Procedure and code for calculating black control rods taking into account epithermal absorption, code CAS-1; Postupak i program za proracun crnih kontrolnih sipki, uzimajuci u obzir i epitermalnu apsorpciju, CAS-1

    Energy Technology Data Exchange (ETDEWEB)

    Martinc, R; Trivunac, N; Zivkovic, Z [Boris Kidric Institute of nuclear sciences Vinca, Belgrade (Yugoslavia)

    1964-12-15

    This report describes the computer code CAS-1, calculation method and procedure applied for calculating the black control rods taking into account the epithermal neutron absorption. Results obtained for supercell method applied for regular lattice reflected in the multiplication medium is part of this report in addition to the computer code manual.

  14. Paleozoic magmatism and porphyry Cu-mineralization in an evolving tectonic setting in the North Qilian Orogenic Belt, NW China

    Science.gov (United States)

    Qiu, Kun-Feng; Deng, Jun; Taylor, Ryan D.; Song, Kai-Rui; Song, Yao-Hui; Li, Quan-Zhong; Goldfarb, Richard J.

    2016-05-01

    The NWW-striking North Qilian Orogenic Belt records the Paleozoic accretion-collision processes in NW China, and hosts Paleozoic Cu-Pb-Zn mineralization that was temporally and spatially related to the closure of the Paleo Qilian-Qinling Ocean. The Wangdian Cu deposit is located in the eastern part of the North Qilian Orogenic Belt, NW China. Copper mineralization is spatially associated with an altered early Paleozoic porphyritic granodiorite, which intruded tonalites and volcaniclastic rocks. Alteration zones surrounding the mineralization progress outward from a potassic to a feldspar-destructive phyllic assemblage. Mineralization consists mainly of quartz-sulfide stockworks and disseminated sulfides, with ore minerals chalcopyrite, pyrite, molybdenite, and minor galena and sphalerite. Gangue minerals include quartz, orthoclase, biotite, sericite, and K-feldspar. Zircon LA-ICPMS U-Pb dating of the ore-bearing porphyritic granodiorite yielded a mean 206Pb/238U age of 444.6 ± 7.8 Ma, with a group of inherited zircons yielding a mean U-Pb age of 485 ± 12 Ma, consistent with the emplacement age (485.3 ± 6.2 Ma) of the barren precursor tonalite. Rhenium and osmium analyses of molybdenite grains returned model ages of 442.9 ± 6.8 Ma and 443.3 ± 6.2 Ma, indicating mineralization was coeval with the emplacement of the host porphyritic granodiorite. Rhenium concentrations in molybdenite (208.9-213.2 ppm) suggest a mantle Re source. The tonalities are medium-K calc-alkaline. They are characterized by enrichment of light rare-earth elements (LREEs) and large-ion lithophile elements (LILEs), depletion of heavy rare-earth elements (HREEs) and high-field-strength elements (HFSEs), and minor negative Eu anomalies. They have εHf(t) values in the range of +3.6 to +11.1, with two-stage Hf model ages of 0.67-1.13 Ga, suggesting that the ca. 485 Ma barren tonalites were products of arc magmatism incorporating melts from the mantle wedge and the lithosphere. In contrast, the

  15. Paleozoic magmatism and porphyry Cu-mineralization in an evolving tectonic setting in the North Qilian Orogenic Belt, NW China

    Science.gov (United States)

    Qiu, Kun-Feng; Deng, Jun; Taylor, Ryan D.; Song, Kai-Rui; Song, Yao-Hui; Li, Quan-Zhong; Goldfarb, Richard J.

    2016-01-01

    The NWW-striking North Qilian Orogenic Belt records the Paleozoic accretion–collision processes in NW China, and hosts Paleozoic Cu–Pb–Zn mineralization that was temporally and spatially related to the closure of the Paleo Qilian-Qinling Ocean. The Wangdian Cu deposit is located in the eastern part of the North Qilian Orogenic Belt, NW China. Copper mineralization is spatially associated with an altered early Paleozoic porphyritic granodiorite, which intruded tonalites and volcaniclastic rocks. Alteration zones surrounding the mineralization progress outward from a potassic to a feldspar-destructive phyllic assemblage. Mineralization consists mainly of quartz-sulfide stockworks and disseminated sulfides, with ore minerals chalcopyrite, pyrite, molybdenite, and minor galena and sphalerite. Gangue minerals include quartz, orthoclase, biotite, sericite, and K-feldspar. Zircon LA-ICPMS U–Pb dating of the ore-bearing porphyritic granodiorite yielded a mean 206Pb/238U age of 444.6 ± 7.8 Ma, with a group of inherited zircons yielding a mean U–Pb age of 485 ± 12 Ma, consistent with the emplacement age (485.3 ± 6.2 Ma) of the barren precursor tonalite. Rhenium and osmium analyses of molybdenite grains returned model ages of 442.9 ± 6.8 Ma and 443.3 ± 6.2 Ma, indicating mineralization was coeval with the emplacement of the host porphyritic granodiorite. Rhenium concentrations in molybdenite (208.9–213.2 ppm) suggest a mantle Re source. The tonalities are medium-K calc-alkaline. They are characterized by enrichment of light rare-earth elements (LREEs) and large-ion lithophile elements (LILEs), depletion of heavy rare-earth elements (HREEs) and high-field-strength elements (HFSEs), and minor negative Eu anomalies. They have εHf(t) values in the range of +3.6 to +11.1, with two-stage Hf model ages of 0.67–1.13 Ga, suggesting that the ca. 485 Ma barren tonalites were products of arc magmatism incorporating melts from the mantle wedge and

  16. Structural evolution of the Irtysh Shear Zone: implication for the Late Paleozoic amalgamation of multiple arc systems in Central Asia

    Science.gov (United States)

    Li, Pengfei; Sun, Min; Rosenbaum, Gideon

    2015-04-01

    The NW-SE Irtysh Shear Zone represents a major tectonic boundary in the Central Asian Orogenic Belt, recording the amalgamation history between the peri-Siberian orogenic system and the Kazakhstan orogenic system. The structural evolution and geodynamics of this shear zone is still poorly documented. Here we present new structural data complemented by chronological data in an attempt to unravel the geodynamic significance of the Irtysh Shear Zone in the context of accretion history of the Central Asian Orogenic Belt. Our results show three episodes of deformation for the shear zone. D1 foliation is locally recognized in low strain area and recorded by garnet inclusions, whereas D2 is represented by a sub-horizontal fabric and related NW-SE lineation. D3 is characterized by a transpersonal deformation event, to form a series of NW-SE mylonitic belts with sinistral kinematics, and to overprint D2 fabric forming regional-scale NW-SE upright folds. A paragneiss sample from the shear zone yielded the youngest detrital zircon peaks in the late Carboniferous, placing a maximum age constraint on the deformation, which overlaps in time with the late Paleozoic collision between the Chinese Altai and the intraoceanic arc system of the East Junggar and West Junggar. We interpret three episodes of deformation to represent orogenic thickening (D1), collapse (D2) and thickening (D3) in response to this collisional event. Sinistral shearing (D3) together with the coeval dextral shearing in the Tianshan accommodate eastward extrusion of the Kazakhstan orogenic system during the late Paleozoic amalgamation of the Central Asian Orogenic Belt. Acknowledgements: This study was financially supported by the Major Basic Research Project of the Ministry of Science and Technology of China (Grant: 2014CB440801), Hong Kong Research Grant Council (HKU705311P and HKU704712P), National Science Foundation of China (41273048, 41273012) and a HKU CRCG grant. The work is a contribution of the Joint

  17. Sedimentology and stratigraphy of Neoproterozoic-lower Paleozoic carbonate-siliciclastic succession of the southwesternmost Amazon Craton, state of Rondônia, Brazil

    OpenAIRE

    Afonso, Jhon Willy Lopes; Nogueira, Afonso César Rodrigues

    2018-01-01

    ABSTRACT: Facies and stratigraphic analysis were carried out in Neoproterozoic-Lower Paleozoic carbonate-siliciclastic deposits of Cacoal and Pimenta Bueno formations exposed on basement rocks and into the Pimenta Bueno Graben, northwestern portion of Parecis Basin, southwesternmost Amazon Craton. The redescription and redefinion of this succession confirmed the previous interpretation for the Cacoal Formation as a Marinoan (~ 635 Ma) cap carbonate. The Cacoal Formation is subdivided here in ...

  18. Geochronology of the Sleeper deposit, Humboldt County, Nevada: epithermal gold-silver mineralization following emplacement of a silicic flow-dome complex

    Science.gov (United States)

    Conrad, J.E.; McKee, E.H.; Rytuba, J.J.; Nash, J.T.; Utterback, W.C.

    1993-01-01

    The high-grade gold-silver deposits at the Sleeper mine are low sulfidation, quartz-adularia-type epithermal deposits, formed during the final stages of igneous hydrothermal activity of a small middle Miocene silicic flow-dome complex in north-central Nevada. There were multiple pulses of alteration and mineralization but all occurred within a period of less than 2 m.y. Later supergene alteration formed opal and alunite about 5.4 Ma but produced no Au or Ag mineralization other than some remobilization to produce locally rich pockets of secondary Au and Ag enrichment and is unrelated to the older magmatic hydrothermal system. The Sleeper deposit in the northern part of the Great Basin is genetically related to bimodal volcanism that followed a long period of arc-related andesitic volcanism in the same general region. -from Authors

  19. Different Activation Techniques for the Study of Epithermal Spectra, Applied to Heavy Water Lattices of Varying Fuel-To-Moderator Ratio

    Energy Technology Data Exchange (ETDEWEB)

    Sokolowski, E K

    1966-06-15

    Spectral indices at the cell boundary have been studied as functions of lattice pitch in the reference core of the Swedish R0 reactor. Epithermal indices were determined by activation of In{sup 115}, employing three different techniques: the two-foil, the cadmium ratio and the sandwich foil methods. The latter of these has the advantage of being independent of assumptions about foil cross sections or spectral functions, and it gives a spectrum index that lends itself readily to comparisons with theoretical multigroup calculations. Alternatively the results can be expressed in terms of the Westcott parameters r and T{sub n} when this is justified by the spectral conditions. The agreement between the three methods investigated is generally good. Good agreement is also found with multigroup collision.

  20. From success to persistence: Identifying an evolutionary regime shift in the diverse Paleozoic aquatic arthropod group Eurypterida, driven by the Devonian biotic crisis.

    Science.gov (United States)

    Lamsdell, James C; Selden, Paul A

    2017-01-01

    Mass extinctions have altered the trajectory of evolution a number of times over the Phanerozoic. During these periods of biotic upheaval a different selective regime appears to operate, although it is still unclear whether consistent survivorship rules apply across different extinction events. We compare variations in diversity and disparity across the evolutionary history of a major Paleozoic arthropod group, the Eurypterida. Using these data, we explore the group's transition from a successful, dynamic clade to a stagnant persistent lineage, pinpointing the Devonian as the period during which this evolutionary regime shift occurred. The late Devonian biotic crisis is potentially unique among the "Big Five" mass extinctions in exhibiting a drop in speciation rates rather than an increase in extinction. Our study reveals eurypterids show depressed speciation rates throughout the Devonian but no abnormal peaks in extinction. Loss of morphospace occupation is random across all Paleozoic extinction events; however, differential origination during the Devonian results in a migration and subsequent stagnation of occupied morphospace. This shift appears linked to an ecological transition from euryhaline taxa to freshwater species with low morphological diversity alongside a decrease in endemism. These results demonstrate the importance of the Devonian biotic crisis in reshaping Paleozoic ecosystems. © 2016 The Author(s). Evolution © 2016 The Society for the Study of Evolution.

  1. Early Paleozoic tectonic reactivation of the Shaoxing-Jiangshan fault zone: Structural and geochronological constraints from the Chencai domain, South China

    Science.gov (United States)

    Sun, Hanshen; Li, Jianhua; Zhang, Yueqiao; Dong, Shuwen; Xin, Yujia; Yu, Yingqi

    2018-05-01

    The Shaoxing-Jiangshan fault zone (SJFZ), as a fundamental Neoproterozoic block boundary that separates the Yangtze Block from the Cathaysia Block, is the key to understanding the evolution of South China from Neoproterozoic block amalgamation to early Paleozoic crustal reworking. New structural observations coupled with geochronological ages from the Chencai domain indicate that intense ductile deformation and metamorphism along the SJFZ occurred at ∼460-420 Ma, in response to the early Paleozoic orogeny in South China. To the east of the SJFZ, the deformation involves widespread generations of NE-striking foliation, intrafolial folds, and local development of sinistral-oblique shear zones. The shearing deformation occurred under amphibolite facies conditions at temperatures of >550 °C (locally even >650 °C). To the west of the SJFZ, the deformation corresponds to sinistral-oblique shearing along NE-striking, steep-dipping zones under greenschist facies conditions at temperatures of 400-500 °C. These deformation styles, as typical mid-crustal expressions of continental reworking, reflect tectonic reactivation of the pre-existing, deeply rooted Neoproterozoic block boundary in the early Paleozoic. We infer that the tectonic reactivation, possibly induced by oblique underthrusting of north Cathaysia, facilitated ductile shearing and burial metamorphic reactions, giving rise to the high-strain zones and high-grade metamorphic rocks. With respect to pre-existing mechanical weakness, our work highlights the role of tectonic reactivation of early structures in localizing later deformation before it propagates into yet undeformed domains.

  2. An Early Permian epithermal gold system in the Tulasu Basin in North Xinjiang, NW China: Constraints from in situ oxygen-sulfur isotopes and geochronology

    Science.gov (United States)

    Dong, Leilei; Wan, Bo; Deng, Chen; Cai, Keda; Xiao, Wenjiao

    2018-03-01

    The Axi and Jingxi-Yelmand gold deposits, being the largest gold deposits in the Chinese North Tianshan, NW China, are located ca. l0 km apart in the Tulasu Basin, and are hosted by the Late Devonian - Early Carboniferous Dahalajunshan Formation. In situ LA-ICP-MS titanium analyses on quartz from the Axi and Jingxi-Yelmand deposits are broadly identical. Accordingly, the calculated ore-forming temperatures by Ti-in-quartz thermometer give average temperatures of 279 °C and 294 °C, respectively. Results of in situ SIMS analyses of oxygen and sulfur isotopes on quartz and pyrite from these two deposits are similar. Temperature-corrected fluids of the Axi deposit have δ18O values of 2.6-8.1‰ and δ34S values of 0.8-2.4‰, whereas the fluids of the Jingxi-Yelmand deposit have δ18O of 6.4-8.9‰ and δ34S of -0.4 to 4.0‰. The oxygen and sulfur isotopes from the two deposits indicate a magmatic origin. LA-ICP-MS zircon U-Pb ages of Aqialehe Formation sandstone provided a lower limit for the mineralization timing of the Axi deposit (288 Ma). In situ SIMS U-Pb analyses on entrapped zircon (297 Ma) and newly recognized 284.5 Ma columnar rhyolite implies that the Jingxi-Yelmand deposit formed in the Early Permian. Based on the magmatic affinity of the ore fluids, similar age and ore-formation temperatures, we propose that the Axi and Jingxi-Yelmand deposits comprise an epithermal gold system, which was driven by the same Permian magma in the Tulasu Basin. The ore geological features together with our new results indicate that the Axi and Jingxi-Yelmand deposits are intermediate and high sulfidation type epithermal deposits, respectively.

  3. Lead isotopic composition of paleozoic and late proterozoic marine carbonate rocks in the vicinity of Yucca Mountains, Nevada

    International Nuclear Information System (INIS)

    Zartman, R.E.; Kwak, L.M.

    1993-01-01

    Paleozoic and Late Proterozoic marine carbonate rocks (limestones, dolomites, and their metamorphic equivalents) cropping out in the vicinity of Yucca Mountain contain lead with an isotopic composition strongly suggesting them to be a major source of the lead observed at Trench 14 in the carbonate phase of carbonate-silica veins and nearby surficial calcrete deposits. Six whole-rock samples of marine carbonate rocks yield 206 Pb/ 204 Pb = 19.21-29.06, 207 Pb/ 204 Pb = 15.74-16.01, and 208 Pb/ 204 Pb = 37.90-39.25, and leachate and residue fractions of the rocks reveal additional isotopic heterogeneity within individual samples. Two samples of eolian dust also have isotopic compositions lying along a 'carbonate' to 'silicate' mixing trend that appears to arise entirely from pedeogenic processes. The tendency for the marine carbonate rocks to evolve highly uranogenic, but not thorogenic, lead results in a distinctive isotopic composition that serves as a tracer in eolian dust and secondary carbonate minerals derived from the marine carbonate rocks

  4. Late Paleozoic sedimentation on the northern margin of the North China block: implications for regional tectonics and climate change

    Energy Technology Data Exchange (ETDEWEB)

    Cope, T.; Ritts, B.D.; Darby, B.J.; Fildani, A.; Graham, S.A.

    2005-03-01

    The Late Paleozoic collision between the North China continental block and the Altaid arc terranes of Mongolia represents one of the earliest and most fundamental tectonic events in the ongoing construction of Asia. New detrital zircon provenance data from Carboniferous-Permian nonmarine strata on the northern margin of North China imply that the northern margin of the North China block constituted a continental margin arc prior to this collision (-400-275 Ma) and that collision took place via south-directed subduction beneath North China. A significant and widespread climate change took place in North China in mid-Permian time, and is recorded by a change from Carboniferous and Lower Permian humid-climate, coal-bearing sedimentary facies to Upper Permian and Lower Triassic arid-climate redbeds. In northern North China, this climate change is accompanied by a paleocurrent reversal, which indicates the onset of uplift on the northern margin of the North China block. The temporal association of climate change and uplift suggests that aridification of North China may have been caused by a rainshadow effect from topography related to the convergence and ultimate collision between the North China block and the Altaid arc terranes of Mongolia. Alternatively, climate change may have occurred as a result of northward drift of the North China block through arid subtropical latitudes.

  5. Crustal structure beneath the Paleozoic Parnaíba Basin revealed by airborne gravity and magnetic data, Brazil

    Science.gov (United States)

    de Castroa, David L.; Fuck, Reinhardt A.; Phillips, Jeffrey D.; Vidotti, Roberta M.; Bezerra, Francisco H. R.; Dantas, Elton L.

    2014-01-01

    The Parnaíba Basin is a large Paleozoic syneclise in northeastern Brazil underlain by Precambrian crystalline basement, which comprises a complex lithostructural and tectonic framework formed during the Neoproterozoic–Eopaleozoic Brasiliano–Pan African orogenic collage. A sag basin up to 3.5 km thick and 1000 km long formed after the collage. The lithologic composition, structure, and role in the basin evolution of the underlying basement are the focus of this study. Airborne gravity and magnetic data were modeled to reveal the general crustal structure underneath the Parnaíba Basin. Results indicate that gravity and magnetic signatures delineate the main boundaries and structural trends of three cratonic areas and surrounding Neoproterozoic fold belts in the basement. Triangular-shaped basement inliers are geophysically defined in the central region of this continental-scale Neoproterozoic convergence zone. A 3-D gravity inversion constrained by seismological data reveals that basement inliers exhibit a 36–40.5 km deep crustal root, with borders defined by a high-density and thinner crust. Forward modeling of gravity and magnetic data indicates that lateral boundaries between crustal units are limited by Brasiliano shear zones, representing lithospheric sutures of the Amazonian and São Francisco Cratons, Tocantins Province and Parnaíba Block. In addition, coincident residual gravity, residual magnetic, and pseudo-gravity lows indicate two complex systems of Eopaleozoic rifts related to the initial phase of the sag deposition, which follow basement trends in several directions.

  6. 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

  7. Paleozoic-involving thrust array in the central Sierras Interiores (South Pyrenean Zone, Central Pyrenees): regional implications

    Science.gov (United States)

    Rodriguez, L.; Cuevas, J.; Tubía, J. M.

    2012-04-01

    This work deals with the structural evolution of the Sierras Interiores between the Tena and Aragon valleys. The Sierras Interiores is a WNW-trending mountain range that bounds the South Pyrenean Zone to the north and that is characterized by a thrust-fold system with a strong lithological control that places preferably decollements in Triassic evaporites. In the studied area of the Sierras Interiores Cenomanian limestones cover discordantly the Paleozoic rocks of the Axial Zone because there is a stratigraphic lacuna developed from Triassic to Late Cretaceous times. A simple lithostratigraphy of the study area is made up of Late Cenomanian to Early Campanian limestones with grey colour and massive aspect in landscape (170 m, Lower calcareous section), Campanian to Maastrichtian brown coloured sandstones (400-600 m, Marboré sandstones) and, finally, Paleocene light-coloured massive limestones (130-230 m), that often generate the higher topographic levels of the Sierras Interiores due to their greater resistance to erosion. Above the sedimentary sequence of the Sierras Interiores, the Jaca Basin flysch succession crops out discordantly. Based on a detailed mapping of the studied area of the Sierras Interiores, together with well and structural data of the Jaca Basin (Lanaja, 1987; Rodríguez and Cuevas, 2008) we have constructed a 12 km long NS cross section, approximately parallel to the movement direction deduced for this region (Rodríguez et al., 2011). The main structure is a thrust array made up of at least four Paleozoic-involving thrusts (the deeper thrust system) of similar thickness in a probably piggyback sequence, some of which are blind thrusts that generate fold-propagation-folds in upper levels. The higher thrust of the thrust array crops out duplicating the lower calcareous section all over the Sierras Interiores. The emplacement of the deeper thrust system generated the tightness of previous structures: south directed piggyback duplexes (the upper

  8. Petrology and geochemistry of meta-ultramafic rocks in the Paleozoic Granjeno Schist, northeastern Mexico: Remnants of Pangaea ocean floor

    Science.gov (United States)

    Torres-Sánchez, Sonia Alejandra; Augustsson, Carita; Jenchen, Uwe; Rafael Barboza-Gudiño, J.; Alemán Gallardo, Eduardo; Ramírez Fernández, Juan Alonso; Torres-Sánchez, Darío; Abratis, Michael

    2017-08-01

    The Granjeno Schist is a meta-volcanosedimentary upper Paleozoic complex in northeastern Mexico. We suggest different tectonic settings for metamorphism of its serpentinite and talc-bearing rocks based on petrographic and geochemical compositions. According to the REE ratios (LaN/YbN = 0.51 -20.0 and LaN/SmN = 0.72-9.1) and the enrichment in the highly incompatible elements Cs (0.1 ppm), U (2.8 ppm), and Zr (60 ppm) as well as depletion in Ba (1 - 15 ppm), Sr (1 -184 ppm), Pb (0.1 -14 ppm), and Ce (0.1 -1.9 ppm) the rocks have mid-ocean ridge and subduction zones characteristics. The serpentinite contains Al-chromite, ferrian chromite and magnetite. The Al-chromite is characterized by Cr# of 0.48 to 0.55 suggesting a MORB origin, and Cr# of 0.93 to 1.00 for the ferrian chromite indicates a prograde metamorphism. We propose at least two serpentinization stages of lithospheric mantle for the ultramafic rock of the Granjeno Schist, (1) a first in an ocean-floor environment at sub-greenschist to greenschist facies conditions and (2) later a serpentinization phase related to the progressive replacement of spinel by ferrian chromite and magnetite at greenschist to low amphibolite facies conditions during regional metamorphism. The second serpentinization phase took place in an active continental margin during the Pennsylvanian. We propose that the origin of the ultramafic rocks is related to an obduction and accretional event at the western margin of Pangea.

  9. Petrology and geochemistry of meta-ultramafic rocks in the Paleozoic Granjeno Schist, northeastern Mexico: Remnants of Pangaea ocean floor

    Directory of Open Access Journals (Sweden)

    Torres-Sánchez Sonia Alejandra

    2017-08-01

    Full Text Available The Granjeno Schist is a meta-volcanosedimentary upper Paleozoic complex in northeastern Mexico. We suggest different tectonic settings for metamorphism of its serpentinite and talc-bearing rocks based on petrographic and geochemical compositions. According to the REE ratios (LaN/YbN = 0.51 –20.0 and LaN/SmN = 0.72–9.1 and the enrichment in the highly incompatible elements Cs (0.1 ppm, U (2.8 ppm, and Zr (60 ppm as well as depletion in Ba (1 – 15 ppm, Sr (1 –184 ppm, Pb (0.1 –14 ppm, and Ce (0.1 –1.9 ppm the rocks have mid-ocean ridge and subduction zones characteristics. The serpentinite contains Al-chromite, ferrian chromite and magnetite. The Al-chromite is characterized by Cr# of 0.48 to 0.55 suggesting a MORB origin, and Cr# of 0.93 to 1.00 for the ferrian chromite indicates a prograde metamorphism. We propose at least two serpentinization stages of lithospheric mantle for the ultramafic rock of the Granjeno Schist, (1 a first in an ocean-floor environment at sub-greenschist to greenschist facies conditions and (2 later a serpentinization phase related to the progressive replacement of spinel by ferrian chromite and magnetite at greenschist to low amphibolite facies conditions during regional metamorphism. The second serpentinization phase took place in an active continental margin during the Pennsylvanian. We propose that the origin of the ultramafic rocks is related to an obduction and accretional event at the western margin of Pangea.

  10. Genetic Types and Source of the Upper Paleozoic Tight Gas in the Hangjinqi Area, Northern Ordos Basin, China

    Directory of Open Access Journals (Sweden)

    Xiaoqi Wu

    2017-01-01

    Full Text Available The molecular and stable isotopic compositions of the Upper Paleozoic tight gas in the Hangjinqi area in northern Ordos Basin were investigated to study the geochemical characteristics. The tight gas is mainly wet with the dryness coefficient (C1/C1–5 of 0.853–0.951, and δ13C1 and δ2H-C1 values are ranging from -36.2‰ to -32.0‰ and from -199‰ to -174‰, respectively, with generally positive carbon and hydrogen isotopic series. Identification of gas origin indicates that tight gas is mainly coal-type gas, and it has been affected by mixing of oil-type gas in the wells from the Shilijiahan and Gongkahan zones adjacent to the Wulanjilinmiao and Borjianghaizi faults. Gas-source correlation indicates that coal-type gas in the Shiguhao zone displays distal-source accumulation. It was mainly derived from the coal-measure source rocks in the Upper Carboniferous Taiyuan Formation (C3t and Lower Permian Shanxi Formation (P1s, probably with a minor contribution from P1s coal measures from in situ Shiguhao zone. Natural gas in the Shilijiahan and Gongkahan zones mainly displays near-source accumulation. The coal-type gas component was derived from in situ C3t-P1s source rocks, whereas the oil-type gas component might be derived from the carbonate rocks in the Lower Ordovician Majiagou Formation (O1m.

  11. Late Paleozoic to Jurassic chronostratigraphy of coastal southern Peru: Temporal evolution of sedimentation along an active margin

    Science.gov (United States)

    Boekhout, F.; Sempere, T.; Spikings, R.; Schaltegger, U.

    2013-11-01

    We present an integrated geochronological and sedimentological study that significantly revises the basin and magmatic history associated with lithospheric thinning in southern coastal Peru (15-18°S) since the onset of subduction at ˜530 Ma. Until now, estimating the age of the sedimentary and volcanic rocks has heavily relied on paleontologic determinations. Our new geochronological data, combined with numerous field observations, provide the first robust constraints on their chronostratigraphy, which is discussed in the light of biostratigraphical attributions. A detailed review of the existing local units simplifies the current stratigraphic nomenclature and clarifies its absolute chronology using zircon U-Pb ages. We observe that the Late Paleozoic to Jurassic stratigraphy of coastal southern Peru consists of two first-order units, namely (1) the Yamayo Group, a sedimentary succession of variable (0-2 km) thickness, with apparently no nearby volcanic lateral equivalent, and (2) the overlying Yura Group, consisting of a lower, 1-6 km-thick volcanic and volcaniclastic unit, the Chocolate Formation, and an upper, 1-2 km-thick sedimentary succession that are in markedly diachronous contact across the coeval arc and back-arc. We date the local base of the Chocolate Formation, and thus of the Yura Group, to 216 Ma, and show that the underlying Yamayo Group spans a >110 Myr-long time interval, from at least the Late Visean to the Late Triassic, and is apparently devoid of significant internal discontinuities. The age of the top of the Chocolate Formation, i.e. of the volcanic arc pile, varies from ˜194 Ma to less than ˜135 Ma across the study area. We suggest that this simplified and updated stratigraphic framework can be reliably used as a reference for future studies.

  12. Two-stage structural development of a Paleozoic auriferous shear zone at the Globe-Progress deposit, Reefton, New Zealand

    International Nuclear Information System (INIS)

    Milham, L.; Craw, D.

    2009-01-01

    The Globe-Progress gold deposit at Reefton is hosted in a curvilinear mineralised zone that cuts Paleozoic Greenland Group basement metagreywackes. Two discrete phases of mineralisation have resulted in the formation of five different ore types along the shear. An initial phase of mineralisation formed hydrothermal quartz veins and associated Au, As, and S enrichment, with low-grade mineralised host rock. These quartz veins and mineralised host rocks form the outer regions of the mineralised zone. A second hydrothermal phase introduced Sb, Au, As, and S during brittle shear deformation focused on the pre-existing mineralised rocks. This deformation and mineralisation resulted in the formation of metre-scale cataclasite ore and quartz breccia from mineralised host rock and hydrothermal quartz veins, respectively. Cataclasite was derived from argillite layers in the host rock, from which Na, Fe, and Mg have been leached during mineralisation; Al, Ti, and Cr have been conserved; and there has been minor enrichment in Sr, Pb, Zn, and Cu. No quartz was added to the cataclasite or quartz breccia during mineralisation, but some quartz recrystallisation occurred locally, and quartz clasts were physically incorporated into the cataclasite during deformation. The presence of euhedral sulfides in the cataclasite (40% of total sulfides), late-stage undeformed stibnite veins infilling breccia (1-5 cm 3 scale), and undeformed free gold in quartz breccia, imply that the second phase of mineralisation persisted both during and after cataclasis and brecciation. Antimony deposition is greatest in the central cataclasite, up to 6 wt%, and locally in the quartz breccia where stibnite veins are present. Concentrations of Sb decrease with distance from the shear zone. The second, Sb-rich phase of mineralisation in the Globe-Progress deposit resembles similar Sb-rich overprints in the correlative Victorian goldfield of Australia. (author). 38 refs., 10 figs., 1 tab.

  13. Deposition of a saline giant in the Mississippian Windsor Group, Nova Scotia, and the nascent Late Paleozoic Ice Age

    Science.gov (United States)

    MacNeil, Laura A.; Pufahl, Peir K.; James, Noel P.

    2018-01-01

    Saline giants are vast marine evaporite deposits that currently have no modern analogues and remain one of the most enigmatic of chemical sedimentary rocks. The Mississippian Windsor Group (ca. 345 Ma), Maritimes Basin, Atlantic Canada is a saline giant that consists of two evaporite-rich sedimentary sequences that are subdivided into five subzones. Sequence 1 is composed almost entirely of thick halite belonging to Subzone A (Osagean). Sequence 2 is in unconformable contact and comprised of stacked carbonate-evaporite peritidal cycles of Subzones B through E (Meramecian). Subzone B, the focus of research herein, documents the transition from wholly evaporitic to open marine conditions and thus, preserves an exceptional window into the processes forming saline giants. Lithofacies stacking patterns in Subzone B reveal that higher-order fluctuations in relative sea level produced nine stacked parasequences interpreted to reflect high frequency glacioeustatic oscillations during the onset of the Late Paleozoic Ice Age. Each parasequence reflects progradation of intertidal and sabkha sediments over subtidal carbonate and evaporite deposits. Dissimilarities in cycle composition between sub-basins imply the development of contrasting brine chemistries from differing recharge rates with the open ocean. What the Windsor Group shows is that evaporite type is ostensibly linked to the amplitude and frequency of sea level rise and fall during deposition. True saline giants, like the basinwide evaporites of Sequence 1, apparently require low amplitude, long frequency changes in sea level to promote the development of stable brine pools that are only periodically recharged with seawater. By contrast, the high amplitude, short frequency glacioeustatic variability in sea level that controlled the accumulation of peritidal evaporites in Subzone B produce smaller, subeconomic deposits with more complex facies relationships.

  14. Late Devonian glacial deposits from the eastern United States signal an end of the mid-Paleozoic warm period

    Science.gov (United States)

    Brezinski, D.K.; Cecil, C.B.; Skema, V.W.; Stamm, R.

    2008-01-01

    A Late Devonian polymictic diamictite extends for more than 400??km from northeastern Pennsylvania across western Maryland and into east-central West Virginia. The matrix-supported, unbedded, locally sheared diamictite contains subangular to rounded clasts up to 2??m in diameter. The mostly rounded clasts are both locally derived and exotic; some exhibit striations, faceting, and polish. The diamictite commonly is overlain by laminated siltstone/mudstone facies associations (laminites). The laminites contain isolated clasts ranging in size from sand and pebbles to boulders, some of which are striated. The diamictite/laminite sequence is capped by massive, coarse-grained, pebbly sandstone that is trough cross-bedded. A stratigraphic change from red, calcic paleo-Vertisols in strata below the diamictite to non-calcic paleo-Spodosols and coal beds at and above the diamictite interval suggests that the climate became much wetter during deposition of the diamictite. The diamictite deposit is contemporaneous with regressive facies that reflect fluvial incision during the Late Devonian of the Appalachian basin. These deposits record a Late Devonian episode of climatic cooling so extreme that it produced glaciation in the Appalachian basin. Evidence for this episode of climatic cooling is preserved as the interpreted glacial deposits of diamictite, overlain by glaciolacustrine varves containing dropstones, and capped by sandstone interpreted as braided stream outwash. The Appalachian glacigenic deposits are contemporaneous with glacial deposits in South America, and suggest that Late Devonian climatic cooling was global. This period of dramatic global cooling may represent the end of the mid-Paleozoic warm interval that began in the Middle Silurian. ?? 2008 Elsevier B.V. All rights reserved.

  15. Variable post-Paleozoic deformation detected by seismic reflection profiling across the northwestern "prong" of New Madrid seismic zone

    Science.gov (United States)

    McBride, J.H.; Pugin, Andre J.M.; Nelson, W.J.; Larson, T.H.; Sargent, S.L.; Devera, J.A.; Denny, F.B.; Woolery, E.W.

    2003-01-01

    High-resolution shallow seismic reflection profiles across the northwesternmost part of the New Madrid seismic zone (NMSZ) and northwestern margin of the Reelfoot rift, near the confluence of the Ohio and Mississippi Rivers in the northern Mississippi embayment, reveal intense structural deformation that apparently took place during the late Paleozoic and/or Mesozoic up to near the end of the Cretaceous Period. The seismic profiles were sited on both sides of the northeast-trending Olmsted fault, defined by varying elevations of the top of Mississippian (locally base of Cretaceous) bedrock. The trend of this fault is close to and parallel with an unusually straight segment of the Ohio River and is approximately on trend with the westernmost of two groups of northeast-aligned epicenters ("prongs") in the NMSZ. Initially suspected on the basis of pre-existing borehole data, the deformation along the fault has been confirmed by four seismic reflection profiles, combined with some new information from drilling. The new data reveal (1) many high-angle normal and reverse faults expressed as narrow grabens and anticlines (suggesting both extensional and compressional regimes) that involved the largest displacements during the late Cretaceous (McNairy); (2) a different style of deformation involving probably more horizontal displacements (i.e., thrusting) that occurred at the end of this phase near the end of McNairy deposition, with some fault offsets of Paleocene and younger units; (3) zones of steeply dipping faults that bound chaotic blocks similar to that observed previously from the nearby Commerce geophysical lineament (CGL); and (4) complex internal deformation stratigraphically restricted to the McNairy, suggestive of major sediment liquefaction or landsliding. Our results thus confirm the prevalence of complex Cretaceous deformations continuing up into Tertiary strata near the northern terminus of the NMSZ. ?? 2003 Elsevier Science B.V. All rights reserved.

  16. Mineralogy, alteration patterns, geochemistry, and fluid properties of the Ag-Au epithermal deposit Nová Baňa, Slovakia

    Science.gov (United States)

    Majzlan, Juraj; Berkh, Khulan; Kiefer, Stefan; Koděra, Peter; Fallick, Anthony E.; Chovan, Martin; Bakos, František; Biroň, Adrián; Ferenc, Štefan; Lexa, Jaroslav

    2018-02-01

    In this contribution, we report new data on mineralogy, alteration patterns, geochemistry, fluid properties and source of fluids for the deposit Nová Baňa, one of the smaller epithermal deposits in the Middle Miocene Štiavnica andesite stratovolcano (Western Carpathians, Slovakia). Ore veins and the associated rocks were studied in samples from outcrops and old mines, grab samples, and bore holes from the central part of the deposit (ore structures Althandel, Jozef, Jakub, Vavrinec), northern part (Freischurf), SE part (Gupňa) and SW part (Šibeničný vrch). Pervasive hydrothermal alteration transformed the rock-forming minerals into a mixture of adularia and fine-grained quartz, with lesser amount of pyrite, Ti oxides and Fe oxides. This assemblage was further altered to omnipresent interstratified illite/smectite that was used in this study as a geothermometer, corroborating the results from the fluid inclusion work. Ore minerals comprise predominantly pyrite, sphalerite, galena but all sulfides are relatively sparse in the samples studied. Minerals of precious metals are electrum, Ag-tetrahedrite, acanthite, members of the polybasite-pearceite and pyrargyrite-proustite solid solution, and rare miargyrite, Hg-Ag tetrahedrite, and diaphorite. In the central part, we have found also some stibnite. In the SE part of the deposit, acanthite, uytenbogaardtite, and petrovskaite occur and seem to be related to supergene enrichment of the ores. In bulk ore samples, Zn usually dominates over Pb and Cu. The average Ag:Au ratio for the entire deposit is 64:1. The concentrations of precious metals in the grab samples reach maxima of 50 ppm Au and 570 ppm Ag in the SE part and 116 ppm Au and 1110 ppm Ag in the central part of the deposit. Fluid inclusions show signs of trapping of a heterogeneous fluid. In the central, northern and SE parts of the deposit, homogenization temperatures of 190-260 °C and consistently low salinities of minerals is recalculated to fluid

  17. A new indicator mineral methodology based on a generic Bi-Pb-Te-S mineral inclusion signature in detrital gold from porphyry and low/intermediate sulfidation epithermal environments in Yukon Territory, Canada

    Science.gov (United States)

    Chapman, R. J.; Allan, M. M.; Mortensen, J. K.; Wrighton, T. M.; Grimshaw, M. R.

    2017-12-01

    Porphyry-epithermal and orogenic gold are two of the most important styles of gold-bearing mineralization within orogenic belts. Populations of detrital gold resulting from bulk erosion of such regions may exhibit a compositional continuum wherein Ag, Cu, and Hg in the gold alloy may vary across the full range exhibited by natural gold. This paper describes a new methodology whereby orogenic and porphyry-epithermal gold may be distinguished according to the mineralogy of microscopic inclusions observed within detrital gold particles. A total of 1459 gold grains from hypogene, eluvial, and placer environments around calc-alkaline porphyry deposits in Yukon (Nucleus-Revenue, Casino, Sonora Gulch, and Cyprus-Klaza) have been characterized in terms of their alloy compositions (Au, Ag, Cu, and Hg) and their inclusion mineralogy. Despite differences in the evolution of the different magmatic hydrothermal systems, the gold exhibits a clear Bi-Pb-Te-S mineralogy in the inclusion suite, a signature which is either extremely weak or (most commonly) absent in both Yukon orogenic gold and gold from orogenic settings worldwide. Generic systematic compositional changes in ore mineralogy previously identified across the porphyry-epithermal transition have been identified in the corresponding inclusion suites observed in samples from Yukon. However, the Bi-Te association repeatedly observed in gold from the porphyry mineralization persists into the epithermal environment. Ranges of P-T-X conditions are replicated in the geological environments which define generic styles of mineralization. These parameters influence both gold alloy composition and ore mineralogy, of which inclusion suites are a manifestation. Consequently, we propose that this methodology approach can underpin a widely applicable indicator methodology based on detrital gold.

  18. Geology of Paleozoic Rocks in the Upper Colorado River Basin in Arizona, Colorado, New Mexico, Utah, and Wyoming, Excluding the San Juan Basin

    Science.gov (United States)

    Geldon, Arthur L.

    2003-01-01

    The geology of the Paleozoic rocks in the Upper Colorado River Basin in Arizona, Colorado, New Mexico, Utah, and Wyoming, was studied as part of the U.S. Geological Survey's Regional Aquifer-System Analysis Program to provide support for hydrogeological interpretations. The study area is segmented by numerous uplifts and basins caused by folding and faulting that have recurred repeatedly from Precambrian to Cenozoic time. Paleozoic rocks in the study area are 0-18,000 feet thick. They are underlain by Precambrian igneous, metamorphic, and sedimentary rocks and are overlain in most of the area by Triassic formations composed mostly of shale. The overlying Mesozoic and Tertiary rocks are 0-27,000 feet thick. All Paleozoic systems except the Silurian are represented in the region. The Paleozoic rocks are divisible into 11 hydrogeologic units. The basal hydrogeologic unit consisting of Paleozoic rocks, the Flathead aquifer, predominantly is composed of Lower to Upper Cambrian sandstone and quartzite. The aquifer is 0-800 feet thick and is overlain gradationally to unconformably by formations of Cambrian to Mississippian age. The Gros Ventre confining unit consists of Middle to Upper Cambrian shale with subordinate carbonate rocks and sandstone. The confining unit is 0-1,100 feet thick and is overlain gradationally to unconformably by formations of Cambrian to Mississippian age. The Bighom aquifer consists of Middle Cambrian to Upper Ordovician limestone and dolomite with subordinate shale and sandstone. The aquifer is 0-3,000 feet thick and is overlain unconformably by Devonian and Mississipplan rocks. The Elbert-Parting confining unit consists of Lower Devonian to Lower Mississippian limestone, dolomite, sandstone, quartzite, shale, and anhydrite. It is 0-700 feet thick and is overlain conformably to unconformably by Upper Devonian and Mississippian rocks. The Madison aquifer consists of two zones of distinctly different lithology. The lower (Redwall-Leadville) zone

  19. New age constraints on the palaeoenvironmental evolution of the late Paleozoic back-arc basin along the western Gondwana margin of southern Peru

    Science.gov (United States)

    Boekhout, F.; Reitsma, M. J.; Spikings, R.; Rodriguez, R.; Ulianov, A.; Gerdes, A.; Schaltegger, U.

    2018-03-01

    The tectonic evolution of the western Gondwana margin during Pangaea amalgation is recorded in variations in the Permo-Carboniferous back-arc basin sedimentation of Peru. This study provides the first radiometric age constraints on the volcanic and sedimentary sequences of south-central eastern Peru up to the western-most tip of Bolivia, and now permits the correlation of lateral facies variations to the late Paleozoic pre-Andean orogenic cycle. The two phases of Gondwanide magmatism and metamorphism at c. 315 Ma and c. 260 Ma are reflected in two major changes in this sedimentary environment. Our detrital U-Pb zircon ages demonstrate that the timing of Ambo Formation deposition corroborates the Late Mississipian age estimates. The transition from the Ambo to the Tarma Formation around the Middle Pennsylvanian Early Gondwanide Orogeny (c. 315 Ma) represents a relative deepening of the basin. Throughout the shallow marine deposits of the Tarma Formation evidence for contemporaneous volcanism becomes gradually more pronounced and culminates around 312 - 309 Ma. Continuous basin subsidence resulted in a buildup of platform carbonates of the Copacabana Formation. Our data highlights the presence of a previously unrecognized phase of deposition of mainly fluvial sandstones and localized volcanism (281-270 Ma), which we named ´Oqoruro Formation'. This sedimentary succession was previously miss-assigned to the so-called Mitu Group, which has recently been dated to start deposition in the Middle Triassic (∼245-240 Ma). The emersion of this marine basin coincides with the onset of a major plutonic pulse related to the Late Gondwanide Orogeny (c. 260). Exhumation lead to the consequent retreat of the epeiric sea to the present-day sub-Andean region, and the coeval accumulation of the fluvial Oqoruro Formation in south eastern Peru. These late Paleozoic palaeoenvironmental changes in the back-arc basins along the western Gondwana margin of southern reflect changes in

  20. Criteria for the recognition and correlation of sandstone units in the Precambrian and Paleozoic-Mesozoic clastic sequence in the near east

    Science.gov (United States)

    Weissbrod, T.; Perath, I.

    A systematic study of the Precambrian and Paleozoic-Mesozoic clastic sequences (Nubian Sandstone) in Israel and Sinai, and a comparative analysis of its stratigraphy in neighbouring countries, has shown that besides the conventional criteria of subdivision (lithology, field appearance, photogeological features, fossil content), additional criteria can be applied, which singly or in mutual conjuction enable the recognition of widespread units and boundaries. These criteria show lateral constancy, and recurrence of a similar vertical sequence over great distances, and are therefore acceptable for the identification of synchronous, region-wide sedimentary units (and consequently, major unconformities). They also enable, once the units are established, to identify detached (not in situ) samples, samples from isolated or discontinous outcrops, borehole material or archive material. The following rock properties were tested and found to be usefuls in stratigraphic interpretation, throughout large distribution areas of the clastic sequence: Landscape, which is basically the response of a particular textural-chemic al aggregate to atmospheric weathering. Characteristic outcrop feature — styles of roundness or massivity, fissuring or fliatin, slope profile, bedding — express a basic uniformity of these platform-type clastics. Colors are often stratigraphically constant over hundreds of kilometers, through various climates and topographies, and express some intrinsic unity of the rock bodies. Grain size and sorting, when cross-plotted, enable to differentiate existing unit. The method requires the analysis of representative numbers of samples. Vertical trends of median grain size and sorting show reversals, typically across unconformities. Feldstar content diminishes from 15-50% in Precambrian-Paleozoic rocks to a mere 5% or less in Mesozoic sandstones — a distinctive regionwide time trend. Dominance of certain feldstar types characterizes Precambrian and Paleozoic

  1. Petrological and geochemical features of the early Paleozoic granitic gneisses and iron ores in the Tianhu iron deposit, Eastern Tianshan, NW China: Implications for ore genesis

    Science.gov (United States)

    Zheng, Jiahao; Mao, Jingwen; Yang, Fuquan; Chai, Fengmei; Shen, Ping

    2017-08-01

    This paper reports whole-rock geochemical, zircon U-Pb and Hf isotopic data for ore-hosted granitic gneisses, mineral compositions of oxides, and sulfur isotopic data for sulfides in iron ores from the Tianhu deposit, central part of the Eastern Tianshan. Our results can provide crucial constraints on the genesis of granitic gneisses and early Paleozoic tectonic setting of the Eastern Tianshan. LA-ICP-MS U-Pb dating on magmatic zircons yielded weighted mean 206Pb/238U ages of 463 to 438 Ma, interpreted as the crystallization ages of the granitic protoliths and the formation ages of the Tianhu Group. Zircon U-Pb age of ore-hosted granitic gneiss (ca. 459 Ma) can provide reliable constrains on upper limit for iron mineralization age in the Tianhu deposit. Geochemical characteristics suggest that the protoliths of the Tianhu granitic gneisses are metaluminous to weakly peraluminous high-K calc-alkaline granitic rocks, exhibiting typical subduction-related features such as strong enrichment in LREE and LILE and depletion in HFSE. Zircon Hf isotopic compositions show a positive trend from 463 to 438 Ma, indicating that 460 Ma magmas came from both ancient and juvenile sources, whereas 438 Ma magmas involved more juvenile material. Some early Paleozoic granitoids were recently identified in the Eastern Tianshan with the ages between ca. 475 and ca. 425 Ma. The formation of these early Paleozoic granitoids was in response to subduction processes, suggesting that subduction of Junggar Ocean probably began in the Early Ordovician and lasted until Late Silurian. Pyrite and pyrrhotite in iron ores have δ34SCDT values from + 4.6 to + 15.7‰, which are consistent with the marine source, but inconsistent with the magmatic source or those involved evaporites in skarn iron deposit. Geological, geochemical, and isotopic data suggest that the Tianhu iron ores were formed by volcano-sedimentary processes in a subduction environment during the early Paleozoic time, and Tianhu is a

  2. Geochronology and geochemistry of early Paleozoic intrusive rocks from the Khanka Massif in the Russian Far East: Petrogenesis and tectonic implications

    Science.gov (United States)

    Xu, Ting; Xu, Wen-Liang; Wang, Feng; Ge, Wen-Chun; Sorokin, A. A.

    2018-02-01

    This paper presents new geochronological and geochemical data for early Paleozoic intrusive rocks from the Khanka Massif in the Russian Far East, with the aim of elucidating the Paleozoic evolution and tectonic attributes of the Khanka Massif. New U-Pb zircon data indicate that early Paleozoic magmatism within the Khanka Massif can be subdivided into at least four stages: 502, 492, 462-445, and 430 Ma. The 502 Ma pyroxene diorites contain 58.28-59.64 wt% SiO2, 2.84-3.69 wt% MgO, and relatively high Cr and Ni contents. Negative εHf(t) values (- 1.8 to - 0.4), along with other geochemical data, indicate that the primary magma was derived from partial melting of mafic lower crust with the addition of mantle material. The 492 Ma syenogranites have high SiO2 and K2O contents, and show positive Eu anomalies, indicating the primary magma was generated by partial melting of lower crust at relatively low pressure. The 445 Ma Na-rich trondhjemites display high Sr/Y ratios and positive εHf(t) values (+ 1.8 to + 3.9), indicating the primary magma was generated by partial melting of thickened hydrous mafic crust. The 430 Ma granitoids have high SiO2 and K2O contents, zircon εHf(t) values of - 5.4 to + 5.8, and two-stage model ages of 1757-1045 Ma, suggesting the primary magma was produced by partial melting of heterogeneous Proterozoic lower crustal material. The geochemistry of these early Paleozoic intrusive assemblages indicates their formation in an active continental margin setting associated with the subduction of a paleo-oceanic plate beneath the Khanka Massif. The εHf(t) values show an increasingly negative trend with increasing latitude, revealing a lateral heterogeneity of the lower crust beneath the Khanka Massif. Regional comparisons of the magmatic events indicate that the Khanka Massif in the Russian Far East has a tectonic affinity to the Songnen-Zhangguangcai Range Massif rather than the adjacent Jiamusi Massif.

  3. High-resolution sequence stratigraphy of lower Paleozoic sheet sandstones in central North America: The role of special conditions of cratonic interiors in development of stratal architecture

    Science.gov (United States)

    Runkel, Anthony C.; Miller, J.F.; McKay, R.M.; Palmer, A.R.; Taylor, John F.

    2007-01-01

    Well-known difficulties in applying sequence stratigraphic concepts to deposits that accumulated across slowly subsiding cratonic interior regions have limited our ability to interpret the history of continental-scale tectonism, oceanographic dynamics of epeiric seas, and eustasy. We used a multi-disciplinary approach to construct a high-resolution stratigraphic framework for lower Paleozoic strata in the cratonic interior of North America. Within this framework, these strata proved readily amenable to modern sequence stratigraphic techniques that were formulated based on successions along passive margins and in foreland basins, settings markedly different from the cratonic interior. Parasequences, parasequence stacking patterns, systems tracts, maximum flooding intervals, and sequence-bounding unconformities can be confidently recognized in the cratonic interior using mostly standard criteria for identification. The similarity of cratonic interior and foreland basin successions in size, geometry, constituent facies, and local stacking patterns of nearshore parasequences is especially striking. This similarity indicates that the fundamental processes that establish shoreface morphology and determine the stratal expression of retreat and progradation were likewise generally the same, despite marked differences in tectonism, physiography, and bathymetry between the two settings. Our results do not support the widespread perception that Paleozoic cratonic interior successions are so anomalous in stratal geometries, and constitute such a poor record of time, that they are poorly suited for modern sequence stratigraphic analyses. The particular arrangement of stratal elements in the cratonic interior succession we studied is no more anomalous or enigmatic than the variability in architecture that sets all sedimentary successions apart from one another. Thus, Paleozoic strata of the cratonic interior are most appropriately considered as a package that belongs in a

  4. Strontium Isotopic Composition of Paleozoic Carbonate Rocks in the Nevada Test Site Vicinity, Clark, Lincoln, and Nye Counties, Nevada and Inyo County, California

    International Nuclear Information System (INIS)

    James B. Paces; Zell E. Peterman; Kiyoto Futa; Thomas A. Oliver; Brian D. Marshall.

    2007-01-01

    Ground water moving through permeable Paleozoic carbonate rocks represents the most likely pathway for migration of radioactive contaminants from nuclear weapons testing at the Nevada Test Site, Nye County, Nevada. The strontium isotopic composition (87Sr/86Sr) of ground water offers a useful means of testing hydrochemical models of regional flow involving advection and reaction. However, reaction models require knowledge of 87Sr/86Sr data for carbonate rock in the Nevada Test Site vicinity, which is scarce. To fill this data gap, samples of core or cuttings were selected from 22 boreholes at depth intervals from which water samples had been obtained previously around the Nevada Test Site at Yucca Flat, Frenchman Flat, Rainier Mesa, and Mercury Valley. Dilute acid leachates of these samples were analyzed for a suite of major- and trace-element concentrations (MgO, CaO, SiO2, Al2O3, MnO, Rb, Sr, Th, and U) as well as for 87Sr/86Sr. Also presented are unpublished analyses of 114 Paleozoic carbonate samples from outcrops, road cuts, or underground sites in the Funeral Mountains, Bare Mountain, Striped Hills, Specter Range, Spring Mountains, and ranges east of the Nevada Test Site measured in the early 1990's. These data originally were collected to evaluate the potential for economic mineral deposition at the potential high-level radioactive waste repository site at Yucca Mountain and adjacent areas (Peterman and others, 1994). Samples were analyzed for a suite of trace elements (Rb, Sr, Zr, Ba, La, and Ce) in bulk-rock powders, and 87Sr/86Sr in partial digestions of carbonate rock using dilute acid or total digestions of silicate-rich rocks. Pre-Tertiary core samples from two boreholes in the central or western part of the Nevada Test Site also were analyzed. Data are presented in tables and summarized in graphs; however, no attempt is made to interpret results with respect to ground-water flow paths in this report. Present-day 87Sr/86Sr values are compared to values

  5. U-Pb Detrital Zircon Geochronologic Constraints on Depositional Age and Sediment Source Terrains of the Late Paleozoic Tepuel-Genoa Basin

    Science.gov (United States)

    Griffis, N. P.; Montanez, I. P.; Isbell, J.; Gulbranson, E. L.; Wimpenny, J.; Yin, Q. Z.; Cúneo, N. R.; Pagani, M. A.; Taboada, A. C.

    2014-12-01

    The late Paleozoic Ice Age (LPIA) is the longest-lived icehouse of the Phanerozoic and the only time a metazoan dominated and vegetated world transitioned from an icehouse climate into a greenhouse. Despite several decades of research, the timing, extent of glaciation and the location of ice centers remain unresolved, which prohibits reconstruction of ice volume. The Permo-Carboniferous sediments in the Tepuel-Genoa Basin, Patagonia contains a near complete record of sedimentation from the lower Carboniferous through lower Permian. Outsized clasts, thin pebble-rich diamictites and slumps represent the last of the late Paleozoic glacially influenced deep-water marine sediments in the Mojón de Hierro Fm. and the Paleozoic of Patagonia. U-Pb analysis of detrital zircons separated from slope sediments reveal groupings (20 myr bins, n≥5 zircons) with peak depositional ages of 420, 540 to 660 and 1040 Ma. Zircon age populations recovered from the Mojón de Hierro Fm. compare well with bedrock ages of the Deseado Massif of SE Patagonia, suggesting this may be a potential source of sediments. The maximum depositional age of the sediments is 306.05 ± 3.7 Ma (2σ) as determined by the median age of the two youngest concordant zircons that overlap in error. The youngest zircon from the analysis yields a 238U/206Pb age of 301.3 ± 4.5 Ma (2σ; MSWD = 2.3). Younger zircons from the analysis compare well with the age of granite bedrock exposed along the basin margin to the E-NE suggesting they may reflect a more proximal source. These data, which indicate a maximum age of late Carboniferous for the Mojón de Hierro Fm, provide the first geochemical constraints for the timing of final deposition of glaciomarine sediments in the Tepuel-Genoa Basin, and contributes to the biostratigraphic correlation of the late Paleozoic succession in Patagonia with other key LPIA basins that has thus far been hindered by faunal provincialism.

  6. Emplacement and deformation of the Cerro Durazno Pluton delineates stages of the lower Paleozoic tectono-magmatic evolution in NW-Argentina

    Science.gov (United States)

    Hongn, F.; Riller, U.

    2003-04-01

    Regional-scale transpression and transtension are considered to be important in the lower Paleozoic tectono-magmatic evolution of metamorphic and granitoid basement rocks of the southern central Andes. In order to test whether such kinematic changes affected Paleozoic basement rocks on the local scale, i.e. in the Eastern Cordillera of NW-Argentina, we performed a detailed field-based structural analysis of the 456 Ma granitoid Cerro Durazno pluton (CDP). The results of our analysis point to the following stages in the geodynamic evolution of this area: (1) Metamorphism and deformation of Neoproterozoic-Paleozoic basement rocks occurred at high T and low to medium P prior to emplacement of the CDP. This lead to the formation of schists and migmatites characterized by pervasive planar and linear mineral shape fabrics and the growth of andalusite, cordierite and fibrolite. (2) Magmatic foliation in the CDP is defined by the shape-preferred orientation of euhedral feldspar phenocrysts and microgranitoid enclaves. These fabrics are concordant to the NE-SW striking intrusive contact with migmatitic host rocks. The lack of submagmatic or high-T solid-state fabrics in the CDP may indicate that cooling and solidification of granitoid magma was not accompanied by regional deformation. Alternatively, emplacement of granitoid magma may have been facilitated by the creation of open space at mid-crustal level induced by regional deformation. (3) Ductile deformation under greenschist metamorphic conditions overprinted magmatic fabrics of the CDP. This is evident by NW-SE striking metamorphic foliation surfaces transecting magmatic shape fabrics at high angles. During this deformation, the pluton was thrust on a SW-dipping shear zone toward the NE over low-grade metamorphic host rocks which lead to a condensation of metamorphic isograds in the host rocks. Ages of strained pegmatitic dikes indicate that this deformation occurred at about 430 Ma. In summary, the difference in age

  7. Paleomagnetism of Early Paleozoic Rocks from the de Long Archipelago and Tectonics of the New Siberian Islands Terrane

    Science.gov (United States)

    Metelkin, D. V.; Chernova, A. I.; Matushkin, N. Y.; Vernikovskiy, V. A.

    2017-12-01

    The De Long archipelago is located to the north of the Anjou archipelago as a part of a large group between the Laptev Sea and the East Siberian Sea - the New Siberian Islands and consists of Jeannette Island, Bennett Island and Henrietta Island. These islands have been shown to be part of a single continental terrane, whose tectonic history was independent of other continental masses at least since the Ordovician. Paleomagnetic and precise geological data for the De Long archipelago were absent until recently. Only in 2013 special international field trips to the De Long Islands could be organized and geological, isotope-geochronological and paleomagnetic studies were carried out.On Jeannette Island a volcanic-sedimentary sequence intruded by mafic dikes was described. The age of these dikes is more likely Early Ordovician, close to 480 Ma, as evidenced by the results of our 40Ar/39Ar and paleomagnetic investigations of the dolerites as well as the result from detrital zircons in the host rocks published before. On Bennett Island, there are widespread Cambrian-Ordovician mainly terrigenous rocks. Paleomagnetic results from these rocks characterize the paleogeographic position of the De Long archipelago at 465 Ma and perhaps at 530 Ma, although there is no evidence for the primary origin of magnetization for the latter. On Henrietta Island the Early Cambrian volcanic-sedimentary section was investigated. A paleomagnetic pole for 520 Ma was obtained and confirmed by new 40Ar/39Ar results. Adding to our previous paleomagnetic data for the Anjou archipelago the extended variant of the apparent polar wander path for the New Siberian Island terrane was created. The established paleolatitudes define its location in the equatorial and subtropical zone no higher than 40 degrees during the Early Paleozoic. Because there are no good confirmations for true polarity and related geographic hemisphere we present two possibilities for tectonic reconstruction. But both these

  8. Granitoids of the Dry Valleys area, southern Victoria Land : geochemistry and evolution along the early Paleozoic Antarctic Craton margin

    International Nuclear Information System (INIS)

    Allibone, A.H.; Cox, S.C.; Smillie, R.W.

    1993-01-01

    different tectonomagmatic histories along the early Paleozoic Antarctic Craton margin. (author). 60 refs., 9 figs., 1 tab

  9. Polygenetic Karsted Hardground Omission Surfaces in Lower Silurian Neritic Limestones: a Signature of Early Paleozoic Calcite Seas

    Science.gov (United States)

    James, Noel P.; Desrochers, André; Kyser, Kurt T.

    2015-04-01

    Exquisitely preserved and well-exposed rocky paleoshoreline omission surfaces in Lower Silurian Chicotte Formation limestones on Anticosti Island, Quebec, are interpreted to be the product of combined marine and meteoric diagenesis. The different omission features include; 1) planar erosional bedding tops, 2) scalloped erosional surfaces, 3) knobs, ridges, and swales at bedding contacts, and 4) paleoscarps. An interpretation is proposed that relates specific omission surface styles to different diagenetic-depositional processes that took place in separate terrestrial-peritidal-shallow neritic zones. Such processes were linked to fluctuations in relative sea level with specific zones of diagenesis such as; 1) karst corrosion, 2) peritidal erosion, 3) subtidal seawater flushing and cementation, and 4) shallow subtidal deposition. Most surfaces are interpreted to have been the result of initial extensive shallow-water synsedimentary lithification that were, as sea level fell, altered by exposure and subaerial corrosion, only to be buried by sediments as sea level rose again. This succession was repeated several times resulting in a suite of recurring polyphase omission surfaces through many meters of stratigraphic section. Synsedimentary cloudy marine cements are well preserved and are thus interpreted to have been calcitic originally. Aragonite components are rare and thought to have to have been dissolved just below the Silurian seafloor. Large molluscs that survived such seafloor removal were nonetheless leached and the resultant megamoulds were filled with synsedimentary calcite cement. These Silurian inner neritic-strandline omission surfaces are temporally unique. They are part of a suite of marine omission surfaces that are mostly found in early Paleozoic neritic carbonate sedimentary rocks. These karsted hardgrounds formed during a calcite-sea time of elevated marine carbonate saturation and extensive marine cement precipitation. The contemporaneous greenhouse

  10. Selenium in Paleozoic stone coal (carbonaceous shale) as a significant source of environmental contamination in rural southern China

    Science.gov (United States)

    Belkin, H. E.; Luo, K.

    2012-04-01

    Selenium occurs in high concentrations (typically > 10 and up to 700 ppm) in organic-rich Paleozoic shales and cherts (called "stone coal" - shíméi), in southern China. Stone coals are black shales that formed in anoxic to euxinic environments and typically contain high concentrations of organic carbon, are enriched in various metals such as V, Mo, Pb, As, Cr, Ni, Se, etc., and are distinguished from "humic" coal in the Chinese literature. We have examined stone coal from Shaanxi, Hubei, and Guizhou Provinces, People's Republic of China and have focused our study on the mode of occurrence of Se and other elements (e.g. As, Pb, etc.) hazardous to human health. Scanning electron microscope, energy-dispersive analysis and electron microprobe wave-length dispersive spectroscopy were used to identify and determine the composition of host phases observed in the stone coals. Native selenium, Se-bearing pyrite and other sulfides are the hosts for Se, although we cannot preclude an organic or clay-mineral association. Stone coals are an important source of fuel (reserves over 1 billion tonnes), both domestically and in small industry, in some rural parts of southern China and present significant environmental problems for the indigenous population. The stone coals create three main environmental problems related to Se pollution. First, the residual soils formed on stone coal are enriched in Se and other metals contained in the stone coals and, depending on the speciation and bioavailability of the metals, may enrich crops and vegetation grown on them. Second, weathering and leaching of the stone coal contaminates the local ground water and/or surface waters with Se and other metals. Third, the local population uses the stone coal as a source of fuel, which releases the more volatile elements (Se and As) into the atmosphere in the homes. The ash will be extremely enriched with the balance of the heavy metal suite. Disposal of the ash on agricultural lands or near water

  11. The belt of metagabbros of La Pampa: Lower Paleozoic back-arc magmatism in south-central Argentina

    Science.gov (United States)

    Chernicoff, Carlos J.; Zappettini, Eduardo O.; Villar, Luisa M.; Chemale, Farid, Jr.; Hernández, Laura

    2009-12-01

    Combined geological, geochronological, geochemical and geophysical studies have led to identification of a large (˜300 km long, ˜5 km wide) N-S trending belt of metagabbros in the province of La Pampa, south-central Argentina. This belt, though only poorly exposed in the localities of Valle Daza and Sierra de Lonco Vaca, stands out in the geophysical data (aeromagnetics and gravity). Modeling of the aeromagnetic data permits estimation of the geometry of the belt of metagabbros and surrounding rocks. The main rock type exposed is metagabbros with relict magmatic nucleii where layering is preserved. A counterclockwise P-T evolution affected these rocks, i.e., during the Middle Ordovician the protolith reached an initial granulite facies of metamorphism (M1), evolving to amphibolite facies (M2). During the Upper Devonian, a retrograde, greenschist facies metamorphism (M3) partially affected the metagabbros. The whole-rock Sm-Nd data suggest a juvenile source from a depleted mantle, with model ages ranging from 552 to 574 Ma, and positive Epsilon values of 6.51-6.82. A crystallization age of 480 Ma is based on geological considerations, i.e. geochronological data of the host rocks as well as comparisons with the Las Aguilas mafic-ultramafic belt of Sierra de San Luis (central Argentina). The geochemical studies indicate an enriched MORB and back-arc signature. The La Pampa metagabbros are interpreted to be originated as a result of the extension that took place in a back-arc setting coevally with the Famatinian magmatic arc (very poorly exposed in the western part of the study area). The extensional event was 'aborted' by the collision of the Cuyania terrane with Pampia-Gondwana in the Middle Ordovician, causing deformation and metamorphism throughout the arc-back-arc region. The similarities between the La Pampa metagabbros and the mafic-ultramafic Las Aguilas belt of the Sierra de San Luis are very conspicuous, for example, the age (Lower Paleozoic), geochemical

  12. Determination of elemental concentrations in airborne particulate matter in the City of Santiago de Chile, through neutron activation analysis using epithermal neutrons and Compton suppression system

    International Nuclear Information System (INIS)

    Rojas S, Ximena

    1995-01-01

    In order to optimize the Neutron-Activation Analysis (NAA) technique currently carried out in our country, the present work was carried out in the United States where irradiations with epithermal neutrons and a Compton suppression system were used, which allowed the characterization of aerosols of the city of Santiago de Chile. With this purpose, 54 filters of polycarbonate membranes were analysed with aerosols collected in an area of the capital during Spring 1993 and Winter of 1994. As a result, an improvement in the detection limits was observed, specially in elements such as Ni and Zn, which are not easily detectable through NAA. The application of both systems also permits the usage of this technique in geological and biological samples, where the presence of Na, Al and Cl obstruct the determination of some elements. The determined elements in both fractions were Mn, V, Cu, As, Sb, Co, Br, Cl, Ni, Zn, Ca, Al, Na and Fe. (author). 8 refs., 7 figs., 9 tabs

  13. Estimation of total as well as bioaccessible levels and average daily dietary intake of iodine from Japanese edible seaweeds by epithermal neutron activation analysis

    International Nuclear Information System (INIS)

    Fukushima, M.; Chatt, A.

    2012-01-01

    An epi-thermal instrumental neutron activation analysis (EINAA) method in conjunction with Compton suppression spectrometry (EINAA-CSS) was used for the determination of total iodine in eight different species of edible seaweeds from Japan. This method gave an absolute detection limit of about 2 μg. The accuracy of the method was evaluated using various reference materials and found to be generally in agreement within ±6% of the certified values. The longitudinal distributions of iodine at different growing stages in Japanese sea mustard and tangle seaweeds were investigated. For a 150-cm-high tangle, the highest concentration (5,360 mg/kg) of iodine was found at the root, then decreased slowly to 780 mg/kg in the middle portion (60-75 cm), and increased to 2,300 mg/kg at the apex. On the other hand, for a 190-cm-high sea mustard the highest levels of iodine were found both at the roots (164 mg/kg) and apex (152 mg/kg) with lower values (98 mg/kg) in the middle section. In order to estimate the bioaccessible fraction of iodine, seaweeds were digested by an in vitro enzymolysis method, dietary fibre separated from residue, and both fractions analyzed by EINAA-CSS. The average daily dietary intakes of total (0.14 mg) as well as bioaccessible fraction (0.12 mg) of iodine from the consumption of sea mustards were estimated. (author)

  14. Multiple episodes of hydrothermal activity and epithermal mineralization in the southwestern Nevada volcanic field and their relations to magmatic activity, volcanism and regional extension

    International Nuclear Information System (INIS)

    Weiss, S.I.; Noble, D.C.; Jackson, M.C.

    1994-01-01

    Volcanic rocks of middle Miocene age and underlying pre-Mesozoic sedimentary rocks host widely distributed zones of hydrothermal alteration and epithermal precious metal, fluorite and mercury deposits within and peripheral to major volcanic and intrusive centers of the southwestern Nevada volcanic field (SWNVF) in southern Nevada, near the southwestern margin of the Great Basin of the western United States. Radiometric ages indicate that episodes of hydrothermal activity mainly coincided with and closely followed major magmatic pulses during the development of the field and together spanned more than 4.5 m.y. Rocks of the SWNVF consist largely of rhyolitic ash-flow sheets and intercalated silicic lava domes, flows and near-vent pyroclastic deposits erupted between 15.2 and 10 Ma from vent areas in the vicinity of the Timber Mountain calderas, and between about 9.5 and 7 Ma from the outlying Black Mountain and Stonewall Mountain centers. Three magmatic stages can be recognized: the main magmatic stage, Mountain magmatic stage (11.7 to 10.0 Ma), and the late magmatic stage (9.4 to 7.5 Ma)

  15. The Heart of China revisited: II Early Paleozoic (ultra)high-pressure and (ultra)high-temperature metamorphic Qinling orogenic collage

    Science.gov (United States)

    Bader, Thomas; Franz, Leander; Ratschbacher, Lothar; de Capitani, Christian; Webb, A. Alexander G.; Yang, Zhao; Pfänder, Jörg A.; Hofmann, Mandy; Linnemann, Ulf

    2013-07-01

    Orogens with multiple (ultra)high-pressure ((U)HP) and (ultra)high-temperature ((U)HT) metamorphic events provide a complex but telling record of oceanic and continental interaction. The Early Paleozoic history of the "Heart of China," the Qinling orogenic collage, offers snapshots of at least three (U)HP and two (U)HT metamorphic events. The preservation of remnants of both oceanic and continental domains together with a ≥110 Myr record of magmatism allows the reconstruction of the processes that resulted in this disparate metamorphism. Herein, we first illuminate the pressure-temperature-time (P-T-t) evolution of the Early Paleozoic (U)HP and (U)HT events by refining the petrographic descriptions and P-T estimates, assess published, and employ new U/Th-Pb zircon, monazite, and titanite, and 40Ar-39Ar phengite geochronology to date the magmatic and metamorphic events. Then we explore how the metamorphic and magmatic events are related tectonically and how they elucidate the affinities among the various complexes in the Qinling orogenic collage. We argue that a Meso-Neoproterozoic crustal fragment—the Qinling complex—localized subduction-accretion events that involved subduction, oceanic-arc formation, and back-arc spreading along its northern margin, and mtantle-wedge exhumation and spreading-ridge subduction along its southern margin.

  16. A-type granitoid in Hasansalaran complex, northwestern Iran: Evidence for extensional tectonic regime in northern Gondwana in the Late Paleozoic

    Science.gov (United States)

    Azizi, Hossein; Kazemi, Tahmineh; Asahara, Yoshihiro

    2017-07-01

    The Hasansalaran plutonic complex is one of the main intrusive bodies with a wide range of granite, monzonite, diorite and syenite that crop out in northwest Iran. This body includes Paleozoic granitoids that are surrounded and cut by Cretaceous granitoids. Zircon U-Pb age dating shows that the crystallization of this body occurred at 360 Ma ago in the Early Carboniferous. Whole rock compositions of the investigated intrusive body, show high contents of Ga (11.1-76.3 ppm), Zr (73.5-1280 ppm), Zn (43.7-358 ppm), Y(17.9-177 ppm), enrichment of rare earth elements (REEs) together with high Ga/Al ratios and a strong Eu negative anomaly, fairly consistent with typical A-type signature. The low εNd(t = 360 Ma) value (model for evolution of northwest Iran in the Late Paleozoic. Based on our model, the upwelling of a mantle plume, probably due to the proto-Tethys oceanic rollback activity beneath northern Gondwana, had a crucial role in the uplifting of the continental crust and resulted in the crystallization of A-type granitoids with some gabbroic rocks in northwest Iran.

  17. Structure of the surface of the Paleozoic basement of the cis-Kopetdag trough in connection with the oil and gas content of the sedimentary cover

    Energy Technology Data Exchange (ETDEWEB)

    Odekov, O.A.; Mel' nik, N.M.; Tulaeva, S.V.

    1981-01-01

    Use of a complex of different methods permitted a new approach to the study of the nature of the surface of the Paleozoic basement. As a result of constructing models of the deep structure of the cis-Kopetdag trough and the Bakhardok monocline a new map of the major tectonic elements of the region has been developed and a map of the surface structure of the Paleozoic basement and a map of the Moho discontinuity have been compiled. The former gives a major new solution to many problems of the dep structure of the region: 1) in the zone of juncture of the cis-Kopetdag trough and the Bakhardok monocline a new positive structural element has been identified, called the Bakhardok-Kumbet buried superarch; 2) a completely new morphology of the western part of the Serakh connector has been given, within which two independent buried arches are identified, the Shatlyk and Tedzhenskii; 3) it has been established that the Izgantskii arch of the sedimentary cover corresponds to the Izgant uplifted block of the basement. These structural elements are described, methods for identifying them are outlined, and some principles of the variatin of the parameters of the geophysical fields are described. The prospects for the juncture zone are estimated as fairly high from the viewpoint of discovering different types of oil and gas deposits in the widest stratigraphic interval, from the Lower Jurassic to the Neokomian.

  18. Paleogeographic significance of Clavohamulus hintzei Miller (Conodonta) and other Ibexian conodonts in an early Paleozoic carbonate platform facies of the Argentine Precordillera

    Science.gov (United States)

    Lehnert, O.; Miller, J.F.; Repetski, J.E.

    1997-01-01

    Pre-Tremadocian conodonts and trilobites and Tremadocian conodonts are reported from the Cambrian and Ordovician La Silla Formation in the Cerro La Silla section in east-southeast Ja??chal, San Juan Province, Argentina. A shallow marine conodont fauna contains elements of Clavohamulus hintzei Miller, a common species in North America, but reported for the first time from the early Paleozoic platform carbonates of the western Argentine Precordillera. The presence of this species suggests a correlation with the Clavohamulus hintzei conodont subbiozone of the Cordylodus intermedius conodont biozone in North America, considered Early Ordovician (Skullrockian Stage, Ibexian Series) in North America, but by South American and European standards, this biozone would be of latest Cambrian age. C. hintzei and associated conodonts of the La Silla Formation are typical of the tropical faunas of the North American Midcontinent Faunal Province; Late Cambrian trilobites from lower in the formation also are typical North American taxa. The presence of these faunas in the platform carbonates is consistent with plate reconstructions suggesting that the Precordillera was in a tropical or subtropical position close to Laurentia during the late Precambrian and early Paleozoic. These new paleontological data provide one more argument for recent models of the Precordillera as a displaced terrane derived from the Ouachita Embayment at the southern margin of Laurentia.

  19. The paleozoic of Amazonas basin south edge: Tapajos river, Para state; O paleozoico da borda sul da bacia do Amazonas: rio Tapajos, estado do Para

    Energy Technology Data Exchange (ETDEWEB)

    Matsuda, Nilo Siguehiko [Petrobras E e P, Rio de Janeiro, RJ (Brazil). Exploracao. Estratigrafia e Sedimentologia Geologia Aplicada a Exploracao], E-mail: nilo@petrobras.com.br; Winter, Wilson Rubem [Petrobras, Campoas dos Goytacases, RJ (Brazil). Exploracao. Sedimentologia e Estratigrafia], E-mail: winter@petrobras.com.br; Wanderley Filho, Joaquim Ribeiro; Cacela, Alessandra Suzely Moda [Petrobras, Manaus, AM (Brazil). Exploracao. Unidade de Operacoes de Exploracao e Producao da Amazonia], Emails: jwand@petrobras.com.br, alessandra.suzely@petrobras.com.br

    2009-11-15

    The intracratonic Amazonas Basin covers an area close to 500.000km{sup 2} shared between the Amazonas and Para states. The phanerozoic stratigraphic framework is up to 6.000m thick and may be subdivided into two, first order depositional sequences: the Paleozoic sequence, intruded by diabase dikes and sills and the Mesozoic-Cenozoic sequence. Analyzing the stratigraphic framework, the great tectonic influence on the basin development can be appreciated. The mainly NW-SE structural directions of the basement, which mark the boundaries of the geochronological provinces of the Amazonas, are clearly identified along the Tapajos River. The Paleozoic sequence outcrops on the southern border of the Amazonas Basin embraces potential source rocks, reservoirs and seal rocks. They can be subdivided in three, second order sequences, limited by regional unconformities, as: the Ordovician/Devonian, which corresponds to the Pitinga lithostratigraphic formation; the Devonian-Tournaisian, which corresponds to the Maecuru, Erere, Barreirinha and Curiri formations and, the Pensylvanian-Permian that are represented by the Monte Alegre and Itaituba formations. This field trip guide presents these classic lithostratigraphic outcrop units, together with a brief sedimentological description and an analysis of their positioning related to sequence stratigraphical concepts. (author)

  20. Glacially striated, soft sediment surfaces on late Paleozoic tillite at São Luiz do Purunã, PR

    Directory of Open Access Journals (Sweden)

    Ivo Trosdtorf Jr.

    2005-06-01

    Full Text Available Striae and furrows found on the upper surfaces of three stratigraphically superposed decimetric beds of late Paleozoic lodgement tillite of the Itararé Subgroup in the northern Paraná Basin were engraved by ploughing of clasts and possibly also ice protuberances at the base of the glacier, on unconsolidated to partially consolidated sediment. Associated features indicate that the rheology of the bed varied from stiff during lodgement to soft and deformable during ploughing. Poor drainage of meltwater at the glacier-bed interface may have contributed to lower the strength of sediment to deformation. The deformed interval was probably generated during a single glacial phase or advance of a glacier grounding in a marine or lacustrine water body. Changes in the dynamics of the glacier involving slow and fast flow were correlated respectively with alternation of deposition and erosion. The proposed model is analogous to that of lodgement till complexes from the Pleistocene of the northern hemisphere. Retreat of the glacier was probably fast, followed by settling of muds on top of the upper striated and furrowed surface, and progradation of deltaic sands during post-glacial time.Estrias e sulcos encontrados sobre três camadas decimétricas, estratigraficamente superpostas, de tilito de alojamento neopaleozóico do Subgrupo Itararé, na porção norte da Bacia do Paraná, foram formados por aração de clastos e, possivelmente, por protuberâncias de gelo, na base da geleira. Feições associadas indicam que a reologia do sedimento variou de rígido, durante o alojamento, a inconsolidado e deformável durante a aração. A baixa drenagem da água de degelo na interface geleira-substrato pode ter contribuído para reduzir a resistência do sedimento à deformação. A sucessão acima foi gerada provavelmente durante uma única fase glacial ou avanço de geleira sobre corpo de água marinho ou lacustre. Mudanças na dinâmica da geleira envolvendo

  1. Tectonic context of the penetrative fracture system origin in the Early Paleozoic shale complex (Baltic Basin, Poland/Sweden).

    Science.gov (United States)

    Jarosiński, Marek; Gluszynski, Andrzej; Bobek, Kinga; Dyrka, Ireneusz

    2017-04-01

    Characterization of natural fracture and fault pattern play significant role for reservoir stimulation design and evaluation of its results. Having structural observations limited to immediate borehole surrounding it is a common need to build up a fracture model of reservoir in a range of stimulation reservoir volume or even beyond. To do this we need both a 3D seismic model and a consistent concept of the regional tectonic evolution. We present the result of integrated tectonic study in several deep boreholes target the Lower Paleozoic shale complex of Baltic Basin (BB), combined with analysis of 3D seismic survey and outcrop screening in Scania (Swedish part of the BB). During deposition of shale complex in the Ordovician and Silurian the research area was located 200-300 km away from the continental margin of Baltica involved in the Caledonian collision with the Eastern Avalonia. This distance allowed the shale complex to avoid significant tectonic deformation. Regional seismic cross section reveals the general pattern of the BB infill characteristic for the foreland basin underwent post-collisional isostatic rebound. Due to stress changes in collisional context the shale complex was cross-cut by steep, mostly inverse faults trending NW-SE and NE-SW. The fault zones oriented NW-SE are associated with an array of en echelon faults characteristic for strike-slip displacement. In our interpretation, these faults of Silurian (Wenlock) age create pattern of the regional pop-up structure, which is simultaneously involved in the plate flexure extension. Seismic attributes (e.g. curvature or ant tracking) highlight lineaments which mostly mimic the faults orientation. However, attributes show also some artefacts that come from regular array of seismic sources and receivers, which mimic the orthogonal joint system. Structural observations on borehole core lead us to conclusion that regular, orthogonal fracture system developed after maximum burial of the complex

  2. Evidence for de-sulfidation to form native electrum in the Fire Creek epithermal gold-silver deposit, north-central Nevada

    Science.gov (United States)

    Perez, J.; Day, J. M.; Cook, G. W.

    2012-12-01

    The Fire Creek property is a newly developed and previously unstudied epithermal Au-Ag deposit located in the Northern Shoshone range of north central Nevada. The mineralization occurs within and above en echelon N-NW trending basaltic dykes that are hosted within a co-genetic and bimodal suite of mid-Miocene basalts and andesites formed in association with the Yellowstone hotspot-track. Previous studies of Au-Ag mineralization in the Great Basin have focused primarily on extensively mined and/or low-grade deposits. Therefore, the ability for unrestricted sampling of a major Au-Ag deposit early in its exploration and development represents an opportunity for refined understanding of epithermal ore genesis processes. New petrology reveals at least two distinct pulses of mineralization that in relative order of timing are: 1) S-rich veins which are associated with initial host-rock alteration; 2) quartz- and/or calcite-rich veins which vary from fine-grained to lath-like quartz crystals with large calcite crystals in vein centers. Native electrum occurs only within the second phase of mineralization and typically occurs within quartz and adjacent to cross-cut first-phase S-rich veins. In places the electrum appears to replace or form overgrowths around existing sulfide phases. High levels of gold and silver are found in both the first (0.8 g Au/tonne) and second-phase pulses (37 g Au/tonne). Fire Creek shares many similarities with its northern neighbor, the Mule Canyon Au-Ag deposit, with high Fe sulfide contents for some of the ores, altered wall-rocks and the presence of narrow and discontinuous gold-bearing siliceous veins. Like Fire Creek, Mule Canyon possesses two distinct mineralizing phases, a sulfide rich and a late stage calcite/silica assemblage. The first pulse appears to be identical in both locations with a variation of disseminated to euhedral iron-sulfides and associated intense alteration of host rock. However, Fire Creek differs from Mule Canyon in

  3. Mineralized breccia clasts: a window into hidden porphyry-type mineralization underlying the epithermal polymetallic deposit of Cerro de Pasco (Peru)

    Science.gov (United States)

    Rottier, Bertrand; Kouzmanov, Kalin; Casanova, Vincent; Bouvier, Anne-Sophie; Baumgartner, Lukas P.; Wälle, Markus; Fontboté, Lluís

    2018-01-01

    Cerro de Pasco (Peru) is known for its large epithermal polymetallic (Zn-Pb-Ag-Cu-Bi) mineralization emplaced at shallow level, a few hundred meters below the paleo-surface, at the border of a large diatreme-dome complex. Porphyry-style veins crosscutting hornfels and magmatic rock clasts are found in the diatreme breccia and in quartz-monzonite porphyry dikes. Such mineralized veins in clasts allow investigation of high-temperature porphyry-style mineralization developed in the deep portions of magmatic-hydrothermal systems. Quartz in porphyry-style veins contains silicate melt inclusions as well as fluid and solid mineral inclusions. Two types of high-temperature (> 600 °C) quartz-molybdenite-(chalcopyrite)-(pyrite) veins are found in the clasts. Early, thin (1-2 mm), and sinuous HT1 veins are crosscut by slightly thicker (up to 2 cm) and more regular HT2 veins. The HT1 vein quartz hosts CO2- and sulfur-rich high-density vapor inclusions. Two subtypes of the HT1 veins have been defined, based on the nature of mineral inclusions hosted in quartz: (i) HT1bt veins with inclusions of K-feldspar, biotite, rutile, and minor titanite and (ii) HT1px veins with inclusions of actinolite, augite, titanite, apatite, and minor rutile. Using an emplacement depth of the veins of between 2 and 3 km (500 to 800 bar), derived from the diatreme breccia architecture and the supposed erosion preceding the diatreme formation, multiple mineral thermobarometers are applied. The data indicate that HT1 veins were formed at temperatures > 700 °C. HT2 veins host assemblages of polyphase brine inclusions, generally coexisting with low-density vapor-rich inclusions, trapped at temperatures around 600 °C. Rhyolitic silicate melt inclusions found in both HT1 and HT2 veins represent melt droplets transported by the ascending hydrothermal fluids. LA-ICP-MS analyses reveal a chemical evolution coherent with the crystallization of an evolved rhyolitic melt. Quartz from both HT1 and HT2 veins

  4. A prospect for the development of an epithermal neutron beam from the horizontal channel at the TRNC for brain tumors treatment based on the BNCT method

    International Nuclear Information System (INIS)

    Ben-Ghazail, Mustafa Ali

    2005-01-01

    In this work the epithermal neutron was development from horizontal channel VI at Tajoura research reactor which can be used for Boron Neutron Capture Therapy. The analysis of reactivity and control rod worth is performed by three dimensional continues energy MCNP-4C code with neutron cross section data from the ENDF/B-VI evaluation. The neutron beam which is developed for medical purpose is generated from the reactor core by means of U-235 fission. The neutrons leaking through the cavity of HC in Be-9 reflector is guided through a tube made of stainless steel to patient position. The HC has two wheels. The first wheel is small and is used as a gate. The second is large and have three positions one to close the gate, the second to open the gate while the third for loading collimator. The collimator consists of the moderators and filters to optimize the neutron beam which is installed in the loading position. The HC VI is extended to the room constructed to allow space for other horizontal channels users. materials are used to optimize the neutron beam which was selected depending on neutron beam properties related to core loading and control rod position. The results of the development study show that the required values for the neutron beam characteristic can be nearly reached. The different comparisons of the calculations performed using MCNP-4C code with the requirements values of characteristics neutron beam show that the result values of MCNP-4C code model are reliable. (author)

  5. Mineral types of hydrothermal alteration zones in the Dukat ore field and their relationships to leucogranite and epithermal gold-silver ore, northeastern Russia

    Science.gov (United States)

    Filimonova, L. G.; Trubkin, N. V.; Chugaev, A. V.

    2014-05-01

    The paper considers the localization of potassic and propylitic hydrothermal alteration zones in the domal volcanic-plutonic structure controlling the position of the Dukat ore field with the eponymous unique epithermal Au-Ag deposit. Comprehensive mineralogical and geochemical data on rocks and minerals in hydrothermal alteration zones and associated intrusions have shown that quartz-jarosite-sericite, quartz-pyrite-sericite, and quartz-adularia-chlorite alterations were formed with the participation of fluid flows related to a fingerlike projection of a high-K leucogranite porphyry intrusion with large phenocrysts. These hydrothermal alterations developed in the rifted graben under conditions of divergent plate boundaries, whereas quartz-clinozoisite-calcite, epidote-chlorite, and garnet-calcite-chlorite alterations were linked to K-Na leucogranite intrusive bodies and developed under conditions of convergent plate boundaries reactivated as a result of formation of the marginal Okhotsk-Chukotka volcanic belt. Phase separation and coagulation of specific portions of ascending fluids resulted in the formation and stabilization of small-sized particles of native silver and other ore components, which enabled involvement in flows of secondary geothermal solutions and ore-forming fluids. The Sr, Nd, and Pb isotopic compositions of rocks and minerals from the hydrothermal alteration zones, associated intrusions, and economic orebodies at the Dukat deposit indicate that their components have been derived from the juvenile continental crust, which was altered in pre-Cretaceous periods of endogenic activity. The components of gangue minerals of potassic and propylitic hydrothertmal alterations and associated intrusions have been taken from deep sources differing in 87Sr/86Sr and 143Nd/144Nd at similar U/Pb and Th/Pb ratios. Chalcophile lead in products of hydrothermal activity and melanocratic inclusions in leucogranite has been taken from regions with elevated U/Pb and

  6. Mineralogy of the epithermal precious and base metal deposit Banská Hodruša at the Rozália Mine (Slovakia)

    Science.gov (United States)

    Kubač, Alexander; Chovan, Martin; Koděra, Peter; Kyle, J. Richard; Žitňan, Peter; Lexa, Jaroslav; Vojtko, Rastislav

    2018-03-01

    The Au-Ag-Pb-Zn-Cu epithermal deposit Banská Hodruša of intermediate-sulphidation type is located in the Middle Miocene Štiavnica stratovolcano on the inner side of the Carpathian arc in Slovakia. This deposit represents an unusual subhorizontal multi-stage vein system, related to processes of underground cauldron subsidence and exhumation of a subvolcanic granodiorite pluton. Veins are developed on a low-angle normal shear zone, possibly representing a detachment zone in andesitic wall rocks that formed during emplacement and exhumation of the granodiorite pluton. The deposit consists of two parts, separated by a thick sill of quartz-diorite porphyry. The eastern part is currently mined, and the western part has already been depleted. The Banská Hodruša mineralization was formed during four stages: (1) low-grade silicified breccia at subhorizontal structures at the base of the deposit; (2) stockwork of steep veins with rhodonite-rhodochrosite, quartz-sulphide-carbonate and quartz-gold assemblages; (3) thin quartz-gold veins with medium dip in tension cracks inside the shear zone and complementary detachment hosted quartz-base metals-gold veins; (4) Post-ore veins. Gold and electrum (920-730) occur as intergrowths with base metal sulphides or hosted in quartz and carbonates, accompanied by Au-Ag tellurides (hessite, petzite). Rare Te-polybasite and Cu-cervelleite result from re-equilibration of early Te-bearing minerals during cooling. Sulphide minerals include low Fe sphalerite ( 1.25 wt%), galena, chalcopyrite, and pyrite. The wall rock alteration is represented mostly by adularia, illite, chlorite, quartz, calcite and pyrite. Precipitation of gold, Au-Ag tellurides, Mn-bearing minerals and adularia resulted from boiling of fluids due to hydraulic fracturing, as well as opening of dilatational structures within the shear zone.

  7. Characteristics of the Paleozoic slope break system and its control on stratigraphic-lithologic traps: An example from the Tarim Basin, western China

    Directory of Open Access Journals (Sweden)

    Hao Liu

    2015-07-01

    Full Text Available Based on comprehensive analyses of seismic and log data, this study indicates that mainly four widespread angular to minor angular unconformities (Tg8, Tg51, Tg5 and Tg3 were formed during the Paleozoic. Through the interpretation of structural unconformities, calculation of eroded thickness, correction of palaeo-water depth and compaction and compilation of the Early Paleozoic structural maps, the Early Paleozoic slope break belt (geomorphologic unit of the Tarim Basin is subdivided into uplift area, subaqueous uplift area, rift slope break belt, flexure slope break belt (slope belt, depression area and deep basin area. Palaeogeomorphology of the Cambrian-Early Ordovician was approximately in EW trend within which three tectonic units including the Tabei Palaeo-uplift, the northern Depressional Belt and the southern Palaeo-uplift developed respectively and are grouped into two slope break systems namely as the Tabei Palaeo-uplift and the southern Palaeo-uplift. These tectonic units obviously control the deposition of isolated platform, open platform, restricted platform and deep basin. Influenced by extrusion in the Mid-Late Ordovician, the southern and northern subaqueous uplifts gradually elevated and then were eroded. Resultantly two slope break systems developed, namely as the northern and central Palaeo-uplifts which obviously controlled the deposition of provenance area, isolated platform, mixed continental shelf, slope and basin facies. The intensive extrusion of the Mid-Late Ordovician leads to significant tectonic deformation of the Tarim Basin: large area of uplifting and erosion and development of EW trending anticline and syncline. Deposition of shore, tidal flat, delta, shallow marine clastics and deep marine facies is obviously controlled by the Tabei, the southern and the Tadong Palaeo-uplifts. Slope break systems control development of stratigraphic unconformity and thus truncation and onlap unconformity zones become favorable

  8. Petrogenesis of granitoids and associated xenoliths in the early Paleozoic Baoxu and Enping plutons, South China: Implications for the evolution of the Wuyi-Yunkai intracontinental orogen

    Science.gov (United States)

    Yu, Yang; Huang, Xiao-Long; Sun, Min; He, Peng-Li

    2018-05-01

    The early Paleozoic Wuyi-Yunkai orogen was associated with extensive felsic magmatic activities and the orogenic core was mainly distributed in the Yunkai and Wugong domains located in the western Cathaysia block and in the Wuyi domain located in the central part of the Cathaysia block. In order to investigate the evolution of the Wuyi-Yunkai orogen, elemental and Sr-Nd isotopic analyses were performed for granites from the Baoxu pluton in the Yunkai domain and from the Enping pluton in the central part of the Cathaysia block. The Baoxu pluton consists of biotite granite with abundant xenoliths of gneissic granite, granodiorite and diorite, and the Enping pluton is mainly composed of massive granodiorite. Biotite granites (441 ± 5 Ma) and gneissic granite xenolith (443 ± 4 Ma) of the Baoxu pluton are all weakly peraluminous (A/CNK = 1.05-1.10). They show high Sr/Y and La/Yb ratios and have negative bulk-rock εNd(t) values (-7.0 to -4.4), which are similar to coeval gneissic S-type granites in the Yunkai domain and were probably derived from dehydration melting of a sedimentary source with garnet residue in the source. Granodiorites (429 ± 3 Ma) from Enping and granodiorite xenolith (442 ± 4 Ma) from Baoxu are metaluminous and have REE patterns with enriched light REE and flat middle to heavy REE, possibly generated by the dehydration melting of an igneous basement at middle to lower crustal level. Diorite xenolith from Baoxu is ultrapotassic (K2O = 4.9 wt%), has high contents of MgO (7.0 wt%), Cr (379 ppm) and Ni (171 ppm) and shows pronounced negative Nb, Ta and Ti anomalies. This xenolith also has negative εNd(t) value (-3.6) and low Rb/Ba and high Ba/Sr ratios, and is thus interpreted to be derived from an enriched lithospheric mantle with the breakdown of phlogopite. Early Paleozoic I- and S-type granites in the Wuyi-Yunkai orogen mostly have negative εNd(t) values and do not have juvenile components, consistent with genesis by an intracontinental

  9. The Acampamento Velho Formation is a succession of rhyolitic basaltic belong to the lower Paleozoic.: Geochemical characterization of the trace elements and strange lands

    International Nuclear Information System (INIS)

    De Almeida, M.; Zerfass, H.; De Lima, L.

    1998-01-01

    During at the end of Brazilian orogeny cycle (lower Paleozoic), the Camaqua basin was filled by a thick vulcanic series, named Acampamento Velho Formation , which consists of a recurrence of basaltic episodes (at the base) and the alternance of pyroclastic rocks with a rhyolitic composition TBr and Igr) in the intermediate portion and rhyolitic flows (Dr) at the top. Based on the geochemical results, especially on the trace elements such as Zr, Ti, Nb, Y, YB,Th. Ta and the REE., it is confirmed the stratigraphical succession and the depositation chronological order observed in the field. All the volcanic succession presents a behavior pattern typical of post- collisional orogenic, rocks, originated from the crustal contamination of basaltic magmas generated in an environment of the active continental margin. (author)

  10. Re-Os dating on pyrite and metal sources tracing in porphyry-type and neutral epithermal deposits: example of the Bolcana, Troita and Magura deposits, Apuseni Mountains, Romania

    International Nuclear Information System (INIS)

    Cardon, Olivier

    2007-01-01

    Many porphyry-type (Cu-Au) and neutral epithermal (Pb-Zn and Au ± Ag) ore deposits are encountered in the region of the Apuseni Mountains, located at the foot of the Carpathian chain in the Western Romania. These deposits are related to a Neogene andesitic volcanism. In order to demonstrate possible genetic relationships between the porphyry-type and neutral epithermal deposits, the Bolcana porphyry has been investigated since it is surrounded by a number of epithermal low-sulfidation veins with a Pb-Zn ± Au mineralisation. These veins are currently mined at the Troita and Magura sites. A structural analysis and a 3D modelling pf these deposits indicate that the geometry and orientation of fractures and mineralized vein are consistent both with direction of regional extension and with a NW-SE progression of the different andesitic intrusions. In order to establish precisely the temporal relationship between the different ore deposits, a Re-Os dating method has been developed and applied on pyrite which is ubiquitous in all of the deposits. This method enabled us to assign an age of 10.9 ± 1.9 Ma for the porphyry-hosted mineralization. The ages obtained for the epithermal systems are somewhat approximative as perturbations of the Re-Os system are observed for these environments. A fractionation of rhenium responsible for a significant enrichment in this element for the apical zone of the porphyry has been demonstrated. This enrichment is most probably related to a maximum boiling event, which may also explain a similar enrichment in arsenic for the pyrite in the same zone. The sources for the metals have been characterized at the district scale by combining two isotopic systems (Re-Os and Pb-Pb) on both pyrite and galena. The osmium data indicate that the Troita deposit has composition which is similar to that of the Bolcana porphyry. In contrast the results obtained for the Magura deposits indicate the Re-OS system has in this case been perturbed due to a

  11. Predictive mapping using GIS to locate epithermal gold deposits at Cabo de Gata (Prov. of Almeria, Spain); Cartografia predictiva mediante SIG de depositos epitermales de oro en Cabo de Gata, Almeria, Espana

    Energy Technology Data Exchange (ETDEWEB)

    Rogol-Sanchez, J. P.; Chica-Olmo, M.; Rodriguez-Galiano, V.; Pardo-Iguzquiza, E.

    2011-07-01

    The main aim of mineral potential mapping is to generate predictive maps showing the spatial distribution of a numerical index of favour ability for the presence of a mineral deposit of the type sought. We have studied the mineral favorability for epithermal gold deposits in the Cabo de Gata volcanic field in the Province of Almeria in Spain. Predictive maps deriving from the models suggest the presence of several potentially favourable zones. The performance of predictive maps is similar in most cases. Nevertheless, data-driven methods are able to capture more readily the spatial distribution of known gold occurrences in the area. (Author) 32 refs.

  12. Radon levels in houses and workplaces in a uranium rich region in Spain

    International Nuclear Information System (INIS)

    Quindos Poncela, L.S.; Fernandez Navarro, P.L.; Gomez Arozamena, J.; Lopez Romero, A.

    1997-01-01

    The results of a study of the evaluation of the doses per inhalation of radon in a population from a region of Spain rich in uranium is compared with those of workers of a mining installation in the region

  13. Naturally Occurring Radioactive Materials in Uranium-Rich Coals and Associated Coal Combustion Residues from China.

    Science.gov (United States)

    Lauer, Nancy; Vengosh, Avner; Dai, Shifeng

    2017-11-21

    Most coals in China have uranium concentrations up to 3 ppm, yet several coal deposits are known to be enriched in uranium. Naturally occurring radioactive materials (NORM) in these U-rich coals and associated coal combustion residues (CCRs) have not been well characterized. Here we measure NORM (Th, U, 228 Ra, 226 Ra, and 210 Pb) in coals from eight U-rich coal deposits in China and the associated CCRs from one of these deposits. We compared NORM in these U-rich coals and associated CCRs to CCRs collected from the Beijing area and natural loess sediments from northeastern China. We found elevated U concentrations (up to 476 ppm) that correspond to low 232 Th/ 238 U and 228 Ra/ 226 Ra activity ratios (≪1) in the coal samples. 226 Ra and 228 Ra activities correlate with 238 U and 232 Th activities, respectively, and 226 Ra activities correlate well with 210 Pb activities across all coal samples. We used measured NORM activities and ash yields in coals to model the activities of CCRs from all U-rich coals analyzed in this study. The activities of measured and modeled CCRs derived from U-rich coals exceed the standards for radiation in building materials, particularly for CCRs originating from coals with U > 10 ppm. Since beneficial use of high-U Chinese CCRs in building materials is not a suitable option, careful consideration needs to be taken to limit potential air and water contamination upon disposal of U- and Ra-rich CCRs.

  14. New U-Pb ages in the Diablillos Intrusive Complex, Southern Puna, Argentina: A long magmatic event in the Paleozoic Arc, SW Gondwana

    Energy Technology Data Exchange (ETDEWEB)

    Ortiz, Agustin; Hauser, Natalia [Universidade de Brasilia (UnB), DF (Brazil). Instituto de Geociencias. Lab. de Geocronologia; Becchio, Raul; Nieves, Alexis; Suzano, Nestor [Universidad Nacional de Salta (UNSa)-CONICET, Salta (Argentina)

    2015-07-01

    The Puna geological region comprises Salta, Jujuy and Catamarca provinces, northwestern Argentina. This 4000 meter above sea level high-plateau region lies between the Central Argentinian Andes. The Puna basement in the central Andes consists of Proterozoic–Paleozoic metamorphic rocks and granitoids. Diverse authors, proposed different models to explain the origin of the basement, where two orogenic events are recognized: the Pampean (Upper Precambrian–Lower Cambrian) and Famatinian (Upper Cambrian–Lower Silurian) (e.g. Ramos et al., 1986; Ramos, 1988; Loewy et al., 2004; for opposite points of view see Becchio et al., 1999; Bock et al., 2000; Buttner et al., 2005). Hence, Lucassen et al. (2000) proposed for the Central Andean basement, an evolution in a mobile belt, where the Pampean and Famatinian cycles are not distinct events but, they are one single, non-differentiable event from 600 to 400 Ma. The mobile belt culminated in low-P/ high-T metamorphism at approximately 525-500 Ma. Then, these were followed by a long-lasting high-thermal gradient regime in the mid-crust until Silurian times. Becchio et al., (2011) defined the Diablillos Intrusive Complex (CID, by its Spanish name), emplaced in the Inca Viejo Range. This range splits the Salares Ratones-Centenario with the Salar Diablillos (Fig.1). This Complex is located in the Eastern Magmatic Belt, Southern Puna, Argentina. Here we present new zircons U-Pb ages by LA-MC-ICPMS in the Diablillos Intrusive Complex, contributing to understanding the magmatic event in the lower Paleozoic arc, SW Gondwana. (author)

  15. Blueschist metamorphism and its tectonic implication of Late Paleozoic-Early Mesozoic metabasites in the mélange zones, central Inner Mongolia, China

    Science.gov (United States)

    Zhang, Jinrui; Wei, Chunjing; Chu, Hang

    2015-01-01

    Blueschists in central Inner Mongolia are distributed as layers and blocks in mélanges including the southern zone in Ondor Sum area and the northern zone in Manghete and Naomuhunni areas. They have been attributed to the subduction of Early Paleozoic oceanic crust. Blueschists from Ondor Sum and Naomuhunni are characterized by occurrence of sodic amphibole coexisting with epidote, albite, chlorite, calcic amphibole (in Ondor Sum) and muscovite (in Naomuhunni). Blueschists in Manghete contain porphyroblastic albite with inclusions of garnet and epidote in a matrix dominated by calcic-sodic amphibole, epidote, chlorite, albite and muscovite. Phase equilibria modeling for three blueschist samples using pseudosection suggest that the AlM2 contents in sodic amphibole can be used as a good barometer in the limited assemblage involving sodic amphibole + actinolite + epidote + chlorite + albite + quartz under pressures 7-10 kbar. In the sodic amphibole-bearing assemblages, the NaM4 contents in sodic amphibole mainly decrease as temperature rises, being a potential thermometry. The calculated pseudosections constrain the P-T conditions of blueschists to be 3.2-4.2 kbar/355-415 °C in Ondor Sum, 8.2-9.0 kbar/455 °C-495 °C in Manghete and 6.6-8.1 kbar/420-470 °C in Naomuhunni. These P-T estimates indicate a rather high geothermal gradient of 18-25 °C/km for the blueschist metamorphism, being of intermediate P/T facies series. Available zircon U-Pb age data suggests that the protoliths of blueschists were formed later than Late Paleozoic-Early Mesozoic and metamorphosed soon afterwards. An alternative interpretation for the tectonic implication of blueschists in central Inner Mongolia is that they may be a new type attributed to closure of limited ocean basins and do not represent a tectonic regime occurred in conventional subduction setting.

  16. Crustal contamination versus an enriched mantle source for intracontinental mafic rocks: Insights from early Paleozoic mafic rocks of the South China Block

    Science.gov (United States)

    Xu, Wenjing; Xu, Xisheng; Zeng, Gang

    2017-08-01

    Several recent studies have documented that the silicic rocks (SiO2 > 65 wt.%) comprising Silicic Large Igneous Provinces are derived from partial melting of the crust facilitated by underplating/intraplating of "hidden" large igneous province-scale basaltic magmas. The early Paleozoic intracontinental magmatic rocks in the South China Block (SCB) are dominantly granitoids, which cover a combined area of 22,000 km2. In contrast, exposures of mafic rocks total only 45 km2. These mafic rocks have extremely heterogeneous isotopic signatures that range from depleted to enriched (whole rock initial 87Sr/86Sr = 0.7041-0.7102; εNd(t) = - 8.4 to + 1.8; weighted mean zircon εHf(t) = - 7.4 to + 5.2), show low Ce/Pb and Nb/U ratios (0.59-13.1 and 3.5-20.9, respectively), and variable Th/La ratios (0.11-0.51). The high-MgO mafic rocks (MgO > 10 wt.%) tend to have lower εNd(t) values (- 4) and Sm/Nd ratios (> 0.255). The differences in geochemistry between the high-MgO and low-MgO mafic rocks indicate greater modification of the compositions of high-MgO mafic magmas by crustal material. In addition, generally good negative correlations between εNd(t) and initial 87Sr/86Sr ratios, MgO, and K2O, along with the presence of inherited zircons in some plutons, indicate that the geochemical and isotopic compositions of the mafic rocks reflect significant crustal contamination, rather than an enriched mantle source. The results show that high-MgO mafic rocks with fertile isotopic compositions may be indicative of crustal contamination in addition to an enriched mantle source, and it is more likely that the lithospheric mantle beneath the SCB during the early Paleozoic was moderately depleted than enriched by ancient subduction processes.

  17. The distribution, geochronology and geochemistry of early Paleozoic granitoid plutons in the North Altun orogenic belt, NW China: Implications for the petrogenesis and tectonic evolution

    Science.gov (United States)

    Meng, Ling-Tong; Chen, Bai-Lin; Zhao, Ni-Na; Wu, Yu; Zhang, Wen-Gao; He, Jiang-Tao; Wang, Bin; Han, Mei-Mei

    2017-01-01

    Abundant early Paleozoic granitoid plutons are widely distributed in the North Altun orogenic belt. These rocks provide clues to the tectonic evolution of the North Altun orogenic belt and adjacent areas. In this paper, we report an integrated study of petrological features, U-Pb zircon dating, in situ zircon Hf isotope and whole-rock geochemical compositions for the Abei, 4337 Highland and Kaladawan Plutons from north to south in the North Altun orogenic belt. The dating yielded magma crystallization ages of 514 Ma for the Abei Pluton, 494 Ma for the 4337 Highland Pluton and 480-460 Ma for the Kaladawan Pluton, suggesting that they are all products of oceanic slab subduction because of the age constraint. The Abei monzogranites derived from the recycle of Paleoproterozoic continental crust under low-pressure and high-temperature conditions are products of subduction initiation. The 4337 Highland granodiorites have some adakitic geochemical signatures and are sourced from partial melting of thickened mafic lower continental crust. The Kaladawan quartz diorites are produced by partial melting of mantle wedge according to the positive εHf(t) values, and the Kaladawan monzogranite-syenogranite are derived from partial melting of Neoproterozoic continental crust mixing the juvenile underplated mafic material from the depleted mantle. These results, together with existing data, provide significant information about the evolution history of oceanic crust subduction during the 520-460 Ma. The initiation of subduction occurred during 520-500 Ma with formation of Abei Pluton; subsequent transition from steep-angle to flat-slab subduction at ca.500 Ma due to the arrival of buoyant oceanic plateaus, which induces the formation of 4337 Highland Pluton. With ongoing subduction, the steep-angle subduction system is reestablished to cause the formation of 480-460 Ma Kaladawan Pluton. Meanwhile, it is this model that account for the temporal-spatial distribution of these early

  18. A- and I-type metagranites from the North Shahrekord Metamorphic Complex, Iran: Evidence for Early Paleozoic post-collisional magmatism

    Science.gov (United States)

    Badr, Afsaneh; Davoudian, Ali Reza; Shabanian, Nahid; Azizi, Hossein; Asahara, Yoshihiro; Neubauer, Franz; Dong, Yunpeng; Yamamoto, Koshi

    2018-02-01

    The North Shahrekord Metamorphic Complex (NSMC) of the central Sanandaj-Sirjan Zone (SaSZ) consists of metagranitoid bodies, which were metamorphosed within high pressure-low temperature conditions. Whole rock chemistry shows relatively high amounts of SiO2 (65-77 wt%) and Al2O3 (12-15 wt%), low amounts of Nb, P, Sr, Ti, a high ratio of Ga/Al (4-9) and a negative Eu anomaly. The chemical compositions of metagranites are reasonably similar to A- and I-type granites. U-Pb zircon ages of three samples of metagranites indicate that crystallization of the granites occurred at 521.6 ± 9.1 to 513.5 ± 8.5 Ma, Middle Cambrian. The initial 87Sr/86Sr and 143Nd/144Nd ratios of samples vary from 0.7057-0.7239 and 0.511801-0.511890, respectively. High initial 87Sr/86Sr ratios and low εNd(t) values (- 3.39 to - 1.07) associated with high ratios of 206Pb/204Pb(t) = 17.8557-18.8045, 207Pb/204Pb(t) = 15.6721-15.7220, and 208Pb/204Pb(t) = 37.7490-38.4468 infer a significant contribution of continental crust in generating the source magma of the metagranite bodies. The results reveal that the metagranites were mainly produced through mixing of basaltic melts with components similar to metasedimentary sources. The new results show that crystallization of the metagranites occurred in Early Paleozoic times and much earlier than break-up and drifting of the SaSZ from the Arabian plate, suggesting that the metagranites were mainly produced in the western Iran after the closure of the Proto-Tethys Ocean. This model is consistent with the previously suggested models for formation of an Early Paleozoic granitoid belt along the northern rim of Gondwana.

  19. New U-Pb ages in the Diablillos Intrusive Complex, Southern Puna, Argentina: A long magmatic event in the Paleozoic Arc, SW Gondwana

    International Nuclear Information System (INIS)

    Ortiz, Agustin; Hauser, Natalia

    2015-01-01

    The Puna geological region comprises Salta, Jujuy and Catamarca provinces, northwestern Argentina. This 4000 meter above sea level high-plateau region lies between the Central Argentinian Andes. The Puna basement in the central Andes consists of Proterozoic–Paleozoic metamorphic rocks and granitoids. Diverse authors, proposed different models to explain the origin of the basement, where two orogenic events are recognized: the Pampean (Upper Precambrian–Lower Cambrian) and Famatinian (Upper Cambrian–Lower Silurian) (e.g. Ramos et al., 1986; Ramos, 1988; Loewy et al., 2004; for opposite points of view see Becchio et al., 1999; Bock et al., 2000; Buttner et al., 2005). Hence, Lucassen et al. (2000) proposed for the Central Andean basement, an evolution in a mobile belt, where the Pampean and Famatinian cycles are not distinct events but, they are one single, non-differentiable event from 600 to 400 Ma. The mobile belt culminated in low-P/ high-T metamorphism at approximately 525-500 Ma. Then, these were followed by a long-lasting high-thermal gradient regime in the mid-crust until Silurian times. Becchio et al., (2011) defined the Diablillos Intrusive Complex (CID, by its Spanish name), emplaced in the Inca Viejo Range. This range splits the Salares Ratones-Centenario with the Salar Diablillos (Fig.1). This Complex is located in the Eastern Magmatic Belt, Southern Puna, Argentina. Here we present new zircons U-Pb ages by LA-MC-ICPMS in the Diablillos Intrusive Complex, contributing to understanding the magmatic event in the lower Paleozoic arc, SW Gondwana. (author)

  20. Carboniferous - Early Permian magmatic evolution of the Bogda Range (Xinjiang, NW China): Implications for the Late Paleozoic accretionary tectonics of the SW Central Asian Orogenic Belt

    Science.gov (United States)

    Wali, Guzalnur; Wang, Bo; Cluzel, Dominique; Zhong, Linglin

    2018-03-01

    The Late Paleozoic magmatic evolution of the Bogda Range (Chinese North Tianshan) is important for understanding the accretionary history of the Central Asian Orogenic Belt. We investigated the Carboniferous and Lower Permian volcanic and sedimentary sequences of the Daheyan section, southern Bogda Range, and present new zircon U-Pb ages and whole-rock geochemical data for the volcanic rocks. One Carboniferous rhyolite is dated at 298 ± 8 Ma; a Permian basalt yielded many Proterozoic zircon xenocrysts, and its maximum age (∼297 Ma) is constrained by the detrital zircon ages of the sandstone that stratigraphically underlies it. These volcanic rocks belong to calc-alkaline series. We further synthesize previous geochronological, geochemical and isotopic data of magmatic and sedimentary rocks in the Bogda Range. The available data indicate that the magmatism occurred continuously from 350 Ma to 280 Ma. A comprehensive analysis allows us to propose that: (1) the Carboniferous to Early Permian magmatic rocks of the Bogda Range generally show consistent arc-type features; (2) increasing mantle input through time suggests intra-arc extension in a supra-subduction zone; (3) the localized occurrence of Early Permian alkaline pillow basalts and deep water sediments close to the major shear zone advocate a transtensional crustal thinning during the transition from Carboniferous convergence to Early Permian transcurrent tectonics; (4) occurrence of a large number of Proterozoic zircon xenocrysts in the Late Paleozoic magmatic rocks, and Proterozoic detrital zircons in the coeval clastic sediments suggest a continental or transitional basement of the Bogda Arc; (5) subduction in the Bogda area terminated prior to the deposition of Middle Permian terrestrial sediments.

  1. The predictable nature of the Paleozoic sedimentary sequence beneath the Bruce nuclear site in Southern Ontario, Canada

    International Nuclear Information System (INIS)

    Parmenter, Andrew; Jensen, Mark; Crowe, Richard

    2012-01-01

    Document available in extended abstract form only. A key aspect of a Deep Geologic Repository (DGR) safety case is the ability to develop and communicate an understanding of the geologic stability and resilience to change at time frames relevant to demonstrating repository performance. As part of an on-going Environmental Assessment, Ontario Power Generation (OPG) recently completed site-specific investigations within an 850 m thick Paleozoic sedimentary sequence beneath the Bruce nuclear site for the proposed development of a DGR for Low and Intermediate Level Waste (L and ILW). As envisioned, the shaft-accessed DGR would be excavated at a nominal depth of 680 m within the low permeability Ordovician argillaceous limestone of the Cobourg Formation, which is overlain by more than 200 m of low permeability Ordovician shale. The geo-scientific investigations revealed a relatively undeformed and laterally continuous architecture within the sedimentary sequence at the repository scale (1.5 km 2 ) and beyond. This paper explores the predictable nature of the sedimentary sequence that has contributed to increasing confidence in an understanding of the spatial distribution of groundwater system properties, deep groundwater system evolution and natural barrier performance. Multi-disciplinary geo-scientific investigations of the Bruce nuclear site were completed in 3 phases between 2006 and 2010. The sub-surface investigations included a deep drilling, coring and in-situ testing program and, the completion of a 19.7 km (9 lines) 2-D seismic reflection survey. The drilling program involved 6 (150 mm dia.) deep boreholes (4-vertical; 2 inclined) that were extended through the sedimentary sequence from 4 drill sites, arranged around the 0.3 km 2 footprint of the proposed repository. The more than 3.8 km of rock core (77 mm dia.) retrieved have provided, in part, a strong basis to understand bedrock lithology and mineralogy, facies assemblages, structure, and oil and gas

  2. Helium isotope data from the Goldfield epithermal system, Nevada: Evidence for volatile input from a primitive mantle source during ore formation

    Science.gov (United States)

    Hofstra, A. H.; Manning, A. H.

    2013-12-01

    Goldfield is the largest high sulfidation epithermal gold mining district in the United States with over 130 t of gold production and 23 sq. km. of argillic alteration (with alunite, pyrophyllite, or kaolinite). It formed at 20.0×0.5 Ma in an andesite to rhyolite volcanic field in the ancestral Cascades continental magmatic arc. Previous stable isotope studies of quartz, alunite, and sulfide minerals suggest that the gold ores formed in a magmatic vapor plume derived from a subjacent porphyry intrusion, which displaced and mixed with meteoric groundwater at shallow levels. The isotopic compositions of He, Ne, and Ar trapped in fluid inclusions in hydrothermal minerals (Cu-sulfides and sulfosalts, pyrite, quartz) were measured to further constrain volatile source and migration processes. Gases were released by thermal decrepitation at 300°C and analyzed using a high resolution static sector mass spectrometer. The isotopic compositions of Ne and Ar are typical of air-saturated water (ASW), indicating that the samples contain little nucleogenic Ne or radiogenic Ar derived from underlying old crustal sources. In contrast, He/Ne and He/Ar ratios are much greater than ASW, indicating that a component of He was produced in the subsurface. The wide range of He R/Ra values, 0.4 to 20, suggests that He was derived from both crustal and mantle sources. 4He/40Ar* and 4He/21Ne* systematics are characteristic of magma degassing. The highest R/Ra values (15-20) are well above those previously reported for modern volcanic rocks and geothermal fluids in subduction-related arcs. Such R/Ra values indicate a primitive mantle source, perhaps below the subducting slab. We hypothesize that the discharge of metal-laden fluids from the subjacent porphyry intrusion was influenced by the input of hot volatiles from mafic mantle-derived magmas. This scenario implies a magma column that remained open to the flux of volatiles over a considerable depth range, from the mantle to the shallow

  3. Geology of the epithermal Ag-Au Huevos Verdes vein system and San José district, Deseado massif, Patagonia, Argentina

    Science.gov (United States)

    Dietrich, Andreas; Gutierrez, Ronald; Nelson, Eric P.; Layer, Paul W.

    2012-03-01

    The San José district is located in the northwest part of the Deseado massif and hosts a number of epithermal Ag-Au quartz veins of intermediate sulfidation style, including the Huevos Verdes vein system. Veins are hosted by andesitic rocks of the Bajo Pobre Formation and locally by rhyodacitic pyroclastic rocks of the Chon Aike Formation. New 40Ar/39Ar constraints on the age of host rocks and mineralization define Late Jurassic ages of 151.3 ± 0.7 Ma to 144.7 ± 0.1 Ma for volcanic rocks of the Bajo Pobre Formation and of 147.6 ± 1.1 Ma for the Chon Aike Formation. Illite ages of the Huevos Verdes vein system of 140.8 ± 0.2 and 140.5 ± 0.3 Ma are 4 m.y. younger than the volcanic host rock unit. These age dates are among the youngest reported for Jurassic volcanism in the Deseado massif and correlate well with the regional context of magmatic and hydrothermal activity. The Huevos Verdes vein system has a strike length of 2,000 m, with several ore shoots along strike. The vein consists of a pre-ore stage and three main ore stages. Early barren quartz and chalcedony are followed by a mottled quartz stage of coarse saccharoidal quartz with irregular streaks and discontinuous bands of sulfide-rich material. The banded quartz-sulfide stage consists of sulfide-rich bands alternating with bands of quartz and bands of chlorite ± illite. Late-stage sulfide-rich veinlets are associated with kaolinite gangue. Ore minerals are argentite and electrum, together with pyrite, sphalerite, galena, chalcopyrite, minor bornite, covellite, and ruby silver. Wall rock alteration is characterized by narrow (propylitic alteration. Gangue minerals are dominantly massive quartz intergrown with minor to accessory adularia. Epidote, illite, illite/smectite, and, preferentially at deeper levels, Fe-chlorite gangue indicate near-neutral pH hydrothermal fluids at temperatures of >220°C. Kaolinite occurring with the late sulfide-rich veinlet stage indicates pH 315°, whereas strike

  4. Temporal and spatial distribution of alteration, mineralization and fluid inclusions in the transitional high-sulfidation epithermal-porphyry copper system at Red Mountain, Arizona

    Science.gov (United States)

    Lecumberri-Sanchez, Pilar; Newton, M. Claiborne; Westman, Erik C.; Kamilli, Robert J.; Canby, Vertrees M.; Bodnar, Robert J.

    2013-01-01

    Red Mountain, Arizona, is a Laramide porphyry Cu system (PCD) that has experienced only a modest level of erosion compared to most other similar deposits in the southwestern United States. As a result, the upper portion of the magmatic–hydrothermal system, which represents the transition from shallower high-sulfidation epithermal mineralization to deeper porphyry Cu mineralization, is well preserved. Within the Red Mountain system, alteration, mineralization and fluid inclusion assemblages show a systematic distribution in both time and space. Early-potassic alteration (characterized by the minerals biotite and magnetite) is paragenetically earlier than late-potassic alteration (K-feldspar–anhydrite) and both are followed by later phyllic (sericite–pyrite) alteration. Advanced argillic alteration (pyrophyllite–alunite–other clay minerals) is thought to be coeval with or postdate phyllic alteration. Minerals characteristic of advanced argillic alteration are present in the near surface. Phyllic alteration extends to greater depths compared to advanced argillic alteration. Early-potassic and late-potassic alteration are only observed in the deepest part of the system. Considerable overlap of phyllic alteration with both early-potassic and late-potassic alteration zones is observed. The hypogene mineralization contains 0.4–1.2% Cu and is spatially and temporally related to the late-potassic alteration event. Molybdenum concentration is typically In the deepest part of the system, an early generation of low-to-moderate density and salinity liquid + vapor inclusions with opaque daughter minerals is followed in time by halite-bearing inclusions that also contain opaque daughter minerals indicating that an early intermediate-density magmatic fluid evolved to a high-density, high-salinity mineralizing fluid. The increase in density and salinity of fluids with time observed in the deeper parts of the system may be the result of immiscibility (“boiling”) of

  5. Sequence stratigraphic and sedimentologic significance of biogenic structures from a late Paleozoic marginal- to open-marine reservoir, Morrow Sandstone, subsurface of southwest Kansas, USA

    Science.gov (United States)

    Buatois, L.A.; Mangano, M.G.; Alissa, A.; Carr, T.R.

    2002-01-01

    high diversity of biogenic structures representing the activity of a benthic fauna developed under normal salinity conditions. Trace fossil and facies analyses allow environmental subdivision of the shoreface-offshore successions and suggest deposition in a weakly storm-affected nearshore area. An onshore-offshore replacement of the Skolithos ichnofacies by the Cruziana ichnofacies is clearly displayed. The lower Morrow fluvio-estuarine valley was incised during a drop of sea level coincident with the Mississippian-Pennsylvanian transition, but was mostly filled during a subsequent transgression. The transgressive nature of the estuarine infill is further indicated by the upward replacement of depauperate brackish-water trace fossil assemblages by the open-marine Cruziana ichnofacies. Additional stratal surfaces of allostratigraphic significance identified within the estuary include the bayline surface, the tidal ravinement surface, the wave ravinement surface, and a basinwide flooding surface recording inundation of the valley interfluves. A younger sequence boundary within the lower Morrow is also recorded in the Gentzler field at the base of a forced regression shoreface, demarcated by the firmground Glossifungites ichnofacies, indicating a rapid basinward facies migration during a sea-level drop. Trace fossil models derived from the analysis of Mesozoic and Cenozoic reservoirs are generally applicable to the study of these late Paleozoic reservoirs. Pennsylvanian brackish-water facies differ ichnologically from their post-Paleozoic counterparts, however, in that they have: (1) lower trace fossil diversity, (2) lower degree of bioturbation, (3) scarcity of crustacean burrows, (4) absence of firmground suites, and (5) absence of ichnotaxa displaying specific architectures designed to protect the tracemaker from salinity fluctuations. Morrow open-marine ichnofaunas closely resemble their post-Paleozoic equivalents. ?? 2002 Elsevier Science B.V. All rights reserved.

  6. Eclogite-facies metamorphism in impure marble from north Qaidam orogenic belt: Geodynamic implications for early Paleozoic continental-arc collision

    Science.gov (United States)

    Chen, Xin; Xu, Rongke; Schertl, Hans-Peter; Zheng, Youye

    2018-06-01

    In the North Qaidam ultrahigh-pressure (UHP) metamorphic belt, impure marble and interbedded eclogite represent a particular sedimentary provenance and tectonic setting, which have important implications for a controversial problem - the dynamic evolution of early Paleozoic subduction-collision complexes. In this contribution, detailed field work, mineral chemistry, and whole-rock geochemistry are presented for impure marble to provide the first direct evidence for the recycling of carbonate sediments under ultrahigh-pressures during subduction and collision in the Yuka terrane, in the North Qaidam UHP metamorphic belt. According to conventional geothermobarometry, pre-peak subduction to 0.8-1.3 GPa/485-569 °C was followed by peak UHP metamorphism at 2.5-3.3 GPa/567-754 °C and cooling to amphibolite facies conditions at 0.6-0.7 GPa/571-589 °C. U-Pb dating of zircons from impure marble reveals a large group with ages ranging from 441 to 458 Ma (peak at 450 Ma), a smaller group ranging from 770 to 1000 Ma (peak at 780 Ma), and minor >1.8 Ga zircon aged ca. 430 Ma UHP metamorphism. The youngest detrital zircons suggest a maximum depositional age of ca. 442 Ma and a burial rate of ca. 1.0-1.1 cm/yr when combined with P-T conditions and UHP metamorphic age. The REE and trace element patterns of impure marble with positive Sr and U anomalies, negative high field strength elements (Nb, Ta, Zr, Hf, and Ti), and Ce anomalies imply that the marble had a marine limestone precursor. Impure marble intercalated with micaschist and eclogite was similar to limestone and siltstone protoliths deposited in continental fore-arc or arc setting with basic volcanic activity. Therefore, the Yuka terrane most likely evolved in a continental island arc setting during the Paleozoic. These data suggest that metasediments were derived from a mixture of Proterozoic continental crust and juvenile early Paleozoic oceanic and/or island arc crust. In addition, their protoliths were likely

  7. Thermal evolution of Lower Paleozoic sedimentary successions from organic and inorganic studies: the case history of the Holy Cross Mountains (central Poland)

    Science.gov (United States)

    Trolese, Matteo; Stefano Celano, Antonio; Corrado, Sveva; Caricchi, Chiara; Schito, Andrea; Aldega, Luca

    2015-04-01

    The rapid increase in shale gas production in the USA has triggered a growing interest in unconventional resources in Eastern and Northern Europe. In this framework, the potential shale gas reserves in Poland are the most promising in Europe, extending from the Baltic Sea to the Ukraine border. In this area, the Baltic, Podlasie and Lublin basins have already become objective of shale gas exploration and the Holy Cross Mountains (HCM, Central Poland) represents the outcropping analog of the buried targeted Lower Paleozoic successions, providing a unique opportunity to study and assess source rock potential. In this work, we provide new thermal maturity data of Paleozoic rocks exposed in the HCM. A multi-method approach, coupling organic matter/graptolites (i.e., marine organoclasts) optical analysis and X-ray diffraction of clay-sized fraction of sediments, was applied to constrain the burial - thermal evolution of the sedimentary succession. The investigated area of the HCM includes two different tectonic blocks: the Łysogóry region to the North and the Kielce region to the South, separated by the Holy Cross Fault (HCF). lllite content in mixed layer illite-smectite determinations and vitrinite/graptolites reflectance measurements (Roeq%), performed on samples (Cambrian - Devonian) collected from both the regions, show a substantial difference between the two blocks in terms of thermal maturity and burial history. Roeq% values in the southern block range from 0.5% to 1.0%, with few exceptions, indicating early to mid-mature stage of hydrocarbon generation. Samples collected in the northern block show much higher values, mainly from 1.2% up to 1.7%, representative of the gas generation window. The I-S ordering type also shows relevant differences in the two blocks. In the southern block, mixed-layered clay minerals varies from R1 (short-range) to R3 (long-range), whereas R3 structures are recorded in the northern block. Vitrinite reflectance and mixed-layer I

  8. Geologic map and upper Paleozoic stratigraphy of the Marble Canyon area, Cottonwood Canyon quadrangle, Death Valley National Park, Inyo County, California

    Science.gov (United States)

    Stone, Paul; Stevens, Calvin H.; Belasky, Paul; Montañez, Isabel P.; Martin, Lauren G.; Wardlaw, Bruce R.; Sandberg, Charles A.; Wan, Elmira; Olson, Holly A.; Priest, Susan S.

    2014-01-01

    This geologic map and pamphlet focus on the stratigraphy, depositional history, and paleogeographic significance of upper Paleozoic rocks exposed in the Marble Canyon area in Death Valley National Park, California. Bedrock exposed in this area is composed of Mississippian to lower Permian (Cisuralian) marine sedimentary rocks and the Jurassic Hunter Mountain Quartz Monzonite. These units are overlain by Tertiary and Quaternary nonmarine sedimentary deposits that include a previously unrecognized tuff to which we tentatively assign an age of late middle Miocene (~12 Ma) based on tephrochronologic analysis, in addition to the previously recognized Pliocene tuff of Mesquite Spring. Mississippian and Pennsylvanian rocks in the Marble Canyon area represent deposition on the western continental shelf of North America. Mississippian limestone units in the area (Tin Mountain, Stone Canyon, and Santa Rosa Hills Limestones) accumulated on the outer part of a broad carbonate platform that extended southwest across Nevada into east-central California. Carbonate sedimentation was interrupted by a major eustatic sea-level fall that has been interpreted to record the onset of late Paleozoic glaciation in southern Gondwana. Following a brief period of Late Mississippian clastic sedimentation (Indian Springs Formation), a rise in eustatic sea level led to establishment of a new carbonate platform that covered most of the area previously occupied by the Mississippian platform. The Pennsylvanian Bird Spring Formation at Marble Canyon makes up the outer platform component of ten third-order (1 to 5 m.y. duration) stratigraphic sequences recently defined for the regional platform succession. The regional paleogeography was fundamentally changed by major tectonic activity along the continental margin beginning in middle early Permian time. As a result, the Pennsylvanian carbonate shelf at Marble Canyon subsided and was disconformably overlain by lower Permian units (Osborne Canyon and

  9. Geochemistry of Early Paleozoic boninites from the Central Qilian block, Northwest China: Constraints on petrogenesis and back-arc basin development

    Science.gov (United States)

    Gao, Zhong; Zhang, Hong-Fei; Yang, He; Luo, Bi-Ji; Guo, Liang; Xu, Wang-Chun; Pan, Fa-Bin

    2018-06-01

    Early Paleozoic boninites occur in the Central Qilian orogenic belt, Northwest China. Their petrogenesis provides insights into lithosphere process and tectonic evolution of the Qilian block. In this paper, we carry out a study of geochronological, geochemical and Sr-Nd isotopic compositions for the Early Paleozoic boninites in the Lajishan area of the Central Qilian block. The Lajishan boninites (∼483 Ma) have high Al2O3/TiO2 (36.7-64.7) and CaO/TiO2 (31.1-49.6) ratios, and high MgO (7.86-10.47 wt%), Cr (439-599 ppm) and Ni (104-130 ppm) contents, indicating that the boninites result from a refractory mantle source. They are depleted in high field-strength elements (HFSE) and enriched in large ion lithophile elements (LILE), coupled with slightly high initial 87Sr/86Sr values of 0.7059-0.7074 and low εNd(t) values of -1.05 to +2.66, indicating that the mantle source was metasomatized by subducted slab-derived components. We found that an assemblage of low-Ca group and high-Ca group boninites occurred in the Lajishan belt. The high-Ca group boninites were derived from relatively fertile mantle with slightly higher melting degree, whereas the low-Ca group boninites were generated by partial melting of more refractory mantle wedge peridotites with slightly lower melting degree. The assemblage of low-Ca group and high-Ca group boninites reveals that the low-Ca group boninites were generated by the further melting of the more refractory mantle source after the segregation of the high-Ca group boninitic magmas in response to the back-arc basin opening. In the light of reported boninites worldwide, a diagram of Zr/Y vs. CaO/Al2O3 is used to identify boninites in fore-arc and back-arc regions. We suggest that the Lajishan boninites represent the products of back-arc basin development in response to the northward subduction of the Qaidam-West Qinling ocean slab.

  10. Assessment of Appalachian basin oil and gas resources: Utica-Lower Paleozoic Total Petroleum System: Chapter G.10 in Coal and petroleum resources in the Appalachian basin: distribution, geologic framework, and geochemical character

    Science.gov (United States)

    Ryder, Robert T.; Ruppert, Leslie F.; Ryder, Robert T.

    2014-01-01

    The Utica-Lower Paleozoic Total Petroleum System (TPS) in the Appalachian Basin Province is named for the Upper Ordovician Utica Shale, which is the source rock, and for multiple lower Paleozoic sandstone and carbonate units that are the important reservoirs. The total organic carbon (TOC) values for the Utica Shale are usually greater than 1 weight percent. TOC values ranging from 2 to 3 weight percent outline a broad, northeast-trending area that extends across western and southern Pennsylvania, eastern Ohio, northern West Virginia, and southeastern New York. The Utica Shale is characterized by type II kerogen, which is a variety of kerogen that is typically prone to oil generation. Conondont color-alteration index (CAI) isograds, which are based on samples from the Upper Ordovician Trenton Limestone (or Group), indicate that a pod of mature Utica Shale source rocks occupies most of the TPS.

  11. Hydrologic properties and ground-water flow systems of the Paleozoic rocks in the upper Colorado River basin in Arizona, Colorado, New Mexico, Utah, and Wyoming, excluding the San Juan Basin

    Science.gov (United States)

    Geldon, Arthur L.

    2003-01-01

    The hydrologic properties and ground-water flow systems of Paleozoic sedimentary rocks in the Upper Colorado River Basin were investigated under the Regional Aquifer-System Analysis (RASA) program of the U.S. Geological Survey in anticipation of the development of water supplies from bedrock aquifers to fulfill the region's growing water demands. The study area, in parts of Arizona, Colorado, New Mexico, Utah, and Wyoming, covers about 100,000 square miles. It includes parts of four physiographic provinces--the Middle Rocky Mountains, Wyoming Basin, Southern Rocky Mountains, and Colorado Plateaus. A variety of landforms, including mountains, plateaus, mesas, cuestas, plains, badlands, and canyons, are present. Altitudes range from 3,100 to 14,500 feet. Precipitation is distributed orographically and ranges from less than 6 inches per year at lower altitudes to more than 60 inches per year in some mountainous areas. Most of the infrequent precipitation at altitudes of less than 6,000 feet is consumed by evapotranspiration. The Colorado and Green Rivers are the principal streams: the 1964-82 average discharge of the Colorado River where it leaves the Upper Colorado River Basin is 12,170 cubic feet per second (a decrease of 5,680 cubic feet per second since construction of Glen Canyon Dam in 1963). On the basis of their predominant lithologic and hydrologic properties, the Paleozoic rocks are classified into four aquifers and three confining units. The Flathead aquifer, Gros Ventre confining unit, Bighorn aquifer, Elbert-Parting confining unit, and Madison aquifer (Redwall-Leadville and Darwin-Humbug zones) make up the Four Corners aquifer system. A thick sequence, composed mostly of Mississippian and Pennsylvanian shale, anhydrite, halite, and carbonate rocks--the Four Corners confining unit (Belden-Molas and Paradox-Eagle Valley subunits)--overlies the Four Corners aquifer system in most areas and inhibits vertical ground-water flow between the Four Corners aquifer

  12. Productivity Contribution of Paleozoic Woodlands to the Formation of Shale-Hosted Massive Sulfide Deposits in the Iberian Pyrite Belt (Tharsis, Spain)

    Science.gov (United States)

    Fernández-Remolar, David C.; Harir, Mourad; Carrizo, Daniel; Schmitt-Kopplin, Philippe; Amils, Ricardo

    2018-03-01

    The geological materials produced during catastrophic and destructive events are an essential source of paleobiological knowledge. The paleobiological information recorded by such events can be rich in information on the size, diversity, and structure of paleocommunities. In this regard, the geobiological study of late Devonian organic matter sampled in Tharsis (Iberian Pyrite Belt) provided some new insights into a Paleozoic woodland community, which was recorded as massive sulfides and black shale deposits affected by a catastrophic event. Sample analysis using TOF-SIMS (Time of Flight Secondary Ion Mass Spectrometer), and complemented by GC/MS (Gas Chromatrograph/Mass Spectrometer) identified organic compounds showing a very distinct distribution in the rock. While phytochemical compounds occur homogeneously in the sample matrix that is composed of black shale, the microbial-derived organics are more abundant in the sulfide nodules. The cooccurrence of sulfur bacteria compounds and the overwhelming presence of phytochemicals provide support for the hypothesis that the formation of the massive sulfides resulted from a high rate of vegetal debris production and its oxidation through sulfate reduction under suboxic to anoxic conditions. A continuous supply of iron from hydrothermal activity coupled with microbial activity was strictly necessary to produce this massive orebody. A rough estimate of the woodland biomass was made possible by accounting for the microbial sulfur production activity recorded in the metallic sulfide. As a result, the biomass size of the late Devonian woodland community was comparable to modern woodlands like the Amazon or Congo rainforests.

  13. Hierarchy of sedimentary discontinuity surfaces and condensed beds from the middle Paleozoic of eastern North America: Implications for cratonic sequence stratigraphy

    Science.gov (United States)

    McLaughlin, P.I.; Brett, Carlton E.; Wilson, M.A.

    2008-01-01

    Sedimentological analyses of middle Paleozoic epeiric sea successions in North America suggest a hierarchy of discontinuity surfaces and condensed beds of increasing complexity. Simple firmgrounds and hardgrounds, which are comparatively ephemeral features, form the base of the hierarchy. Composite hardgrounds, reworked concretions, authigenic mineral crusts and monomictic intraformational conglomerates indicate more complex histories. Polymictic intraformational conglomerates, ironstones and phosphorites form the most complex discontinuity surfaces and condensed beds. Complexity of discontinuities is closely linked to depositional environments duration of sediment starvation and degree of reworking which in turn show a relationship to stratigraphic cyclicity. A model of cratonic sequence stratigraphy is generated by combining data on the complexity and lateral distribution of discontinuities in the context of facies successions. Lowstand, early transgressive and late transgressive systems tracts are representative of sea-level rise. Early and late transgressive systems tracts are separated by the maximum starvation surface (typically a polymictic intraformational conglomerate or condensed phosphorite), deposited during the peak rate of sea-level rise. Conversely the maximum flooding surface, representing the highest stand of sea level, is marked by little to no break in sedimentation. The highstand and falling stage systems tracts are deposited during relative sea-level fall. They are separated by the forced-regression surface, a thin discontinuity surface or condensed bed developed during the most rapid rate of sea-level fall. The lowest stand of sea level is marked by the sequence boundary. In subaerially exposed areas it is occasionally modified as a rockground or composite hardground.

  14. A geochemical record of polycyclic aromatic hydrocarbons (PAHs) during the late Paleozoic Ice Age: The relationship between atmospheric pCO2, climate and fire.

    Science.gov (United States)

    Hren, M. T.; Harris, G.; Montanez, I. P.; DiMichele, W.; Eley, Y.; White, J. D.; Wilson, J. P.; McElwain, J.; Poulsen, C. J.

    2017-12-01

    The late Paleozoic Ice Age (LPIA) represents a dynamic period of widespread glacial/interglacial cycling as the earth underwent a major transition from an icehouse to greenhouse climate. During this transition period, pCO2 is shown to have varied by several hundred ppm and within the predicted range for anthropogenic change. Glacial/interglacial changes in atmospheric pCO2 during this time are associated with restructuring of tropical forests and carbon cycle dynamics. At present however, there is considerable debate over the potential hydrologic and fire-frequency feedbacks associated with this climatic variability. Polycyclic aromatic hydrocarbons (PAHs) are produced from the incomplete combustion of organic matter and are shown to be preserved over hundreds of millions of years. Thus, these organic compounds provide a potential record of the feedbacks between global biogeochemical systems and fire. We analyzed sedimentary organic matter from the Illinois Basin spanning the late Carboniferous glacial-interglacial cycles to assess the evolution of fire during this period. Our data show a decrease in the overall abundance of high molecular weight PAHs (HMW) from 312 to 304 Myr with significant variability that is coincident with the general timing of pCO2 cycling. Decreasing PAH abundance is also coincident with a proposed long-term change in pO2 and may reflect the influence of atmospheric oxygen in regulating fire occurrence and hydrologic cycling in tropical ecosystems in the late Carboniferous.

  15. Abiotic and biotic responses to Milankovitch-forced megamonsoon and glacial cycles recorded in South China at the end of the Late Paleozoic Ice Age

    Science.gov (United States)

    Fang, Qiang; Wu, Huaichun; Hinnov, Linda A.; Tian, Wenqian; Wang, Xunlian; Yang, Tianshui; Li, Haiyan; Zhang, Shihong

    2018-04-01

    At the end of the Late Paleozoic Ice Age (LPIA) from late Early Permian to early Late Permian, the global climate was impacted by a prevailing megamonsoon and Gondwanan deglaciation. To better understand the abiotic and biotic responses to Milankovitch-forced climate changes during this time period, multi-element X-ray fluorescence (XRF) geochemistry analyses were conducted on 948 samples from the late Early-late Middle Permian Maokou Formation at Shangsi, South China. The Fe/Ti, S/Ti, Ba/Ti and Ca time series, which were calibrated with an existing "floating" astronomical time scale (ATS), show the entire suite of Milankovitch rhythms including 405 kyr long eccentricity, 128 and 95 kyr short eccentricity, 33 kyr obliquity and 20 kyr precession. Spectral coherency and cross-phase analysis reveals that chemical weathering (monitored by Fe/Ti) and upwelling (captured by S/Ti and Ba/Ti) are nearly antiphase in the precession band, which suggests a contrast between summer and winter monsoon intensities. Strong obliquity signal in the Ba/Ti series is proposed to derive from changes in thermohaline circulation intensity from glaciation dynamics in southern Gondwana. The abundance of foraminifer, brachiopod and ostracod faunas within the Maokou Formation were mainly controlled by the 1.1 Myr obliquity modulation cycle. The obliquity-forced high-nutrient and oxygen-depleted conditions generally produced a benthic foraminifer bloom, but threatened the brachiopod and ostracod faunas.

  16. Determination of rare-earths and other trace elements in neo proterozoic-neo paleozoic dykes from Ceara state, Brazil, by neutron activation analysis

    Energy Technology Data Exchange (ETDEWEB)

    Anjos, Rafael Martins dos; Figueiredo, Ana M.G., E-mail: rafael.anjos@usp.b, E-mail: anamaria@ipen.b [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil). Centro do Reator Nuclear de Pesquisas. Lab. de Analise por Ativacao com Neutrons; Cardoso, Gustavo Luan; Marques, Leila S., E-mail: leila@iag.usp.b [Universidade de Sao Paulo (IAG/USP), SP (Brazil). Inst. de Astronomia, Geofisica e Ciencias Atmosfericas

    2011-07-01

    Trace elements such as rare earths, U, Th, Ta, Ba and Hf can be very useful in petrogenetic studies of igneous and metamorphic rocks, giving information about the origin and evolution of magmas. Instrumental Neutron Activation Analysis (INAA) is an accurate and precise for trace element analysis in geological samples, and provides the information required for this kind of studies. In this study, rare earths and incompatible trace elements were determined by INAA in the geological reference materials GS-N and BE-N, to quality control, and for the investigation of acid dykes of neo proterozoic-neo paleozoic ages, which outcrop in the Medio Coreau and Ceara Central domains from the Borborema Province (Ceara State). The powdered samples (particle sizes less than 100 mesh), crushed by using a mechanical agate mortar grinder, were irradiated at the IEA-R1 nuclear reactor at IPEN-CNEN/SP, and the induced activity was measured by high resolution gamma-ray spectrometry. The accuracy and precision of the method were evaluated and preliminary results of dyke samples are presented. (author)

  17. Sedimentology and stratigraphy of Neoproterozoic-lower Paleozoic carbonate-siliciclastic succession of the southwesternmost Amazon Craton, state of Rondônia, Brazil

    Directory of Open Access Journals (Sweden)

    Jhon Willy Lopes Afonso

    2018-02-01

    Full Text Available ABSTRACT: Facies and stratigraphic analysis were carried out in Neoproterozoic-Lower Paleozoic carbonate-siliciclastic deposits of Cacoal and Pimenta Bueno formations exposed on basement rocks and into the Pimenta Bueno Graben, northwestern portion of Parecis Basin, southwesternmost Amazon Craton. The redescription and redefinion of this succession confirmed the previous interpretation for the Cacoal Formation as a Marinoan (~ 635 Ma cap carbonate. The Cacoal Formation is subdivided here in two units separate by sharp contact found exclusively overlying Mesoproterozoic crystalline basement rocks: 1 a homonymous formation characterized by diamictites, sandstones and siltstones with dropstones interpreted as glacio-marine deposits; and 2 the Espigão d’Oeste Formation that consists of dolostone, dolomitic stromatolites, dolostone-siltstone rhythmite and siltstone interpreted as shallow to moderately deep platform deposits. The Ordovician to Silurian Pimenta Bueno Formation is a filling of Pimenta Bueno graben and overlies locally the Meso and Neoproterozoic rocks. This unit consists in diamictites, sandstones, siltstones and pelites interpreted as glacial-marine and tide- to storm-influenced platform deposits, recording a glacio-eustatic regressive-transgressive event. This new stratigraphic proposal modify the current stratigraphy for the Parecis Basin and suggest, at least, two levels of glaciation exposed in the sothwesternmost Amazon Craton related to the Marinoan and Late Ordovician-Early Silurian events.

  18. Total petroleum systems and geologic assessment of undiscovered oil and gas resources in the San Juan Basin Province, exclusive of Paleozoic rocks, New Mexico and Colorado

    Science.gov (United States)

    ,

    2013-01-01

    In 2002, the U.S. Geological Survey (USGS) estimated undiscovered oil and gas resources that have the potential for additions to reserves in the San Juan Basin Province, New Mexico and Colorado. Paleozoic rocks were not appraised. The last oil and gas assessment for the province was in 1995. There are several important differences between the 1995 and 2002 assessments. The area assessed is smaller than that in the 1995 assessment. This assessment of undiscovered hydrocarbon resources in the San Juan Basin Province also used a slightly different approach in the assessment, and hence a number of the plays defined in the 1995 assessment are addressed differently in this report. After 1995, the USGS has applied a total petroleum system (TPS) concept to oil and gas basin assessments. The TPS approach incorporates knowledge of the source rocks, reservoir rocks, migration pathways, and time of generation and expulsion of hydrocarbons; thus the assessments are geologically based. Each TPS is subdivided into one or more assessment units, usually defined by a unique set of reservoir rocks, but which have in common the same source rock. Four TPSs and 14 assessment units were geologically evaluated, and for 13 units, the undiscovered oil and gas resources were quantitatively assessed.

  19. Collision of the Tacheng block with the Mayile-Barleik-Tangbale accretionary complex in Western Junggar, NW China: Implication for Early-Middle Paleozoic architecture of the western Altaids

    Science.gov (United States)

    Zhang, Ji'en; Xiao, Wenjiao; Luo, Jun; Chen, Yichao; Windley, Brian F.; Song, Dongfang; Han, Chunming; Safonova, Inna

    2018-06-01

    Western Junggar in NW China, located to the southeast of the Boshchekul-Chingiz (BC) Range and to the north of the Chu-Balkhash-Yili microcontinent (CBY), played a key role in the architectural development of the western Altaids. However, the mutual tectonic relationships have been poorly constrained. In this paper, we present detailed mapping, field structural geology, and geochemical data from the Barleik-Mayile-Tangbale Complex (BMTC) in Western Junggar. The Complex is divisible into Zones I, II and III, which are mainly composed of Cambrian-Silurian rocks. Zone I contains pillow lava, siliceous shale, chert, coral-bearing limestone, sandstone and purple mudstone. Zone II consists of basaltic lava, siliceous shale, chert, sandstone and mudstone. Zone III is characterized by basalt, chert, sandstone and mudstone. These rocks represent imbricated ocean plate stratigraphy, which have been either tectonically juxtaposed by thrusting or form a mélange with a block-in-matrix structure. All these relationships suggest that the BMTC is an Early-Middle Paleozoic accretionary complex in the eastern extension of the BC Range. These Early Paleozoic oceanic rocks were thrust onto Silurian sediments forming imbricate thrust stacks that are unconformably overlain by Devonian limestone, conglomerate and sandstone containing fossils of brachiopoda, crinoidea, bryozoa, and plant stems and leaves. The tectonic vergence of overturned folds in cherts, drag-related curved cleavages and σ-type structures on the main thrust surface suggests top-to-the-NW transport. Moreover, the positive εNd(t) values of volcanic rocks from the Tacan-1 drill-core, and the positive εHf(t) values and post-Cambrian ages of detrital zircons from Silurian and Devonian strata to the south of the Tacheng block indicate that its basement is a depleted and juvenile lithosphere. And there was a radial outward transition from coral-bearing shallow marine (shelf) to deep ocean (pelagic) environments, and from

  20. Shoshonitic- and adakitic magmatism of the Early Paleozoic age in the Western Kunlun orogenic belt, NW China: Implications for the early evolution of the northwestern Tibetan plateau

    Science.gov (United States)

    Wang, Jian; Hattori, Keiko; Liu, Jianguo; Song, Yue; Gao, Yongbao; Zhang, Han

    2017-08-01

    The Western Kunlun orogenic belt in the northwestern margin of the Tibetan plateau contains two magmatic belts; early Paleozoic belt in the northern part of Western Kunlun Terrane (WKT), and early Mesozoic belt in the southern part of WKT. Both formed from northward subduction of the Paleo-Tethys. The early Paleozoic belt contains large Datong and Qiukesu igneous complexes and many smaller plutons. The Datong complex is mainly composed of dark-colored porphyritic syenite and monzonite with minor light-colored dykes of granite and monzonite. The dark-colored rocks are characterized by moderate SiO2 (58.2-69.3 wt.%), and high Al2O3 (15.3-17.1 wt.%), total alkali (Na2O + K2O = 8.07-10.2 wt.%) and ratios of K2O/Na2O (0.77-1.83). They plot in "shoshonite" field, and show high abundances of LILE including LREE ((La/Yb)n = 15.4-26.2; mean 20.2) with pronounced negative anomalies of Nb-Ta-P-Ti in normalized trace elemental patterns and weak negative anomalies of Eu (δEu = 2Eun/(Smn + Gdn) = 0.68-0.80). The light-colored rocks contain slightly higher concentrations of SiO2 (60.3-72.0 wt.%), similar Al2O3 (14.7-17.6 wt.%), and slightly lower total alkalis (6.57-9.14 wt.%) than dark-colored rocks. They show adakitic geochemical signatures with low Y (5.80-17.2 ppm) and Yb (0.63-1.59 ppm), and high Sr/Y (> 40). U-Pb zircon dating indicates that shoshonitic rocks and adakitic dykes formed at 444 Ma to 443 Ma, and a separate small adakitic plug at 462 Ma. The mean εHf(t) values of zircon range from - 1.6 to - 0.94 (n = 14) with TDM2 of 1.5 Ga for shoshonitic rocks and εHf(t) values from - 1.8 to + 0.72 (n = 12) with TDM2 of 1.4 to 1.5 Ga for adakitic rocks. Shoshonitic rocks show initial 87Sr/86Sr and εNd(t) of 0.7092-0.7100 and - 3.9 to - 3.2, respectively, and adakitic rocks yield initial 87Sr/86Sr and εNd(t) of 0.7099-0.7134 and - 3.6 to - 3.1, respectively. Similar Sr, Nd, and Hf isotope compositions for the shoshonitic and adakitic rocks suggest similar ancient rocks

  1. A Systems Approach to Identifying Exploration and Development Opportunities in the Illinois Basin: Digital Portifolio of Plays in Underexplored Lower Paleozoic Rocks [Part 1 of 2

    Energy Technology Data Exchange (ETDEWEB)

    Seyler, Beverly; Harris, David; Keith, Brian; Huff, Bryan; Lasemi, Yaghoob

    2008-06-30

    This study examined petroleum occurrence in Ordovician, Silurian and Devonian reservoirs in the Illinois Basin. Results from this project show that there is excellent potential for additional discovery of petroleum reservoirs in these formations. Numerous exploration targets and exploration strategies were identified that can be used to increase production from these underexplored strata. Some of the challenges to exploration of deeper strata include the lack of subsurface data, lack of understanding of regional facies changes, lack of understanding the role of diagenetic alteration in developing reservoir porosity and permeability, the shifting of structural closures with depth, overlooking potential producing horizons, and under utilization of 3D seismic techniques. This study has shown many areas are prospective for additional discoveries in lower Paleozoic strata in the Illinois Basin. This project implemented a systematic basin analysis approach that is expected to encourage exploration for petroleum in lower Paleozoic rocks of the Illinois Basin. The study has compiled and presented a broad base of information and knowledge needed by independent oil companies to pursue the development of exploration prospects in overlooked, deeper play horizons in the Illinois Basin. Available geologic data relevant for the exploration and development of petroleum reservoirs in the Illinois Basin was analyzed and assimilated into a coherent, easily accessible digital play portfolio. The primary focus of this project was on case studies of existing reservoirs in Devonian, Silurian, and Ordovician strata and the application of knowledge gained to future exploration and development in these underexplored strata of the Illinois Basin. In addition, a review of published reports and exploration in the New Albany Shale Group, a Devonian black shale source rock, in Illinois was completed due to the recent increased interest in Devonian black shales across the United States. The New

  2. Upper Paleozoic mafic and intermediate volcanic rocks of the Mount Pleasant caldera associated with the Sn-W deposit in southwestern New Brunswick (Canada): Petrogenesis and metallogenic implications

    Science.gov (United States)

    Dostal, Jaroslav; Jutras, Pierre

    2016-10-01

    Upper Paleozoic ( 365 Ma) mafic and intermediate volcanic rocks of the Piskahegan Group constitute a subordinate part of the Mount Pleasant caldera, which is associated with a significant polymetallic deposit (tungsten-molybdenum-bismuth zones 33 Mt ore with 0.21% W, 0.1% Mo and 0.08% Bi and tin-indium zones 4.8 Mt with 0.82% Sn and 129 g/t In) in southwestern New Brunswick (Canada). The epicontinental caldera complex formed during the opening of the late Paleozoic Maritimes Basin in the northern Appalachians. The mafic and intermediate rocks make up two compositionally distinct associations. The first association includes evolved rift-related continental tholeiitic basalts, and the second association comprises calc-alkaline andesites, although both associations were emplaced penecontemporaneously. The basalts have low Mg# 0.34-0.40, smooth chondrite-normalized REE patterns with (La/Yb)n 5-6, primitive mantle-normalized trace element patterns without noticeable negative Nb-Ta anomalies, and their ɛNd(T) ranges from + 2.5 to + 2.2. The basalts were generated by partial melting of a transition zone between spinel and garnet mantle peridotite at a depth of 70-90 km. The calc-alkaline andesites of the second association have chondrite-normalized REE patterns that are more fractionated, with (La/Yb)n 7-8.5, but without significant negative Eu anomalies. Compared to the basaltic rocks, they have lower ɛNd(T) values, ranging from + 0.5 to + 1.9, and their mantle-normalized trace element plots show negative Nb-Ta anomalies. The ɛNd(T) values display negative correlations with indicators of crustal contamination, such as Th/La, Th/Nb and SiO2. The andesitic rocks are interpreted to have formed by assimilation-fractional crystallization processes, which resulted in the contamination of a precursor basaltic magma with crustal material. The parent basaltic magma for both suites underwent a different evolution. The tholeiitic basalts experienced shallow-seated fractional

  3. Paleozoic tectonic evolution of the Dananhu-Tousuquan island arc belt, Eastern Tianshan: Constraints from the magmatism of the Yuhai porphyry Cu deposit, Xinjiang, NW China

    Science.gov (United States)

    Wang, Yunfeng; Chen, Huayong; Han, Jinsheng; Chen, Shoubo; Huang, Baoqiang; Li, Chen; Tian, Qinglei; Wang, Chao; Wu, Jianxin; Chen, Mingxia

    2018-03-01

    The Yuhai intrusions (quartz diorite, granite and pyroxene diorite) are located in the eastern part of the Dananhu-Tousuquan island arc belt of the Eastern Tianshan, and associated with the early Paleozoic porphyry Cu mineralization. LA-ICP-MS zircon U-Pb dating yielded emplacement ages of 443.5 ± 4.1 Ma for the quartz diorite, 325.4 ± 2.5 Ma for the granite, and 291 ± 3.0 Ma for the pyroxene diorite. These rocks are tholeiitic to calc-alkaline and metaluminous, with A/CNK values ranging from 0.66 to 1.10. The Silurian ore-bearing Yuhai quartz diorite is rich in LREEs and LILEs (e.g., K, Ba, Pb and Sr), and depleted in HREEs and HFSEs (e.g., Nb, Ta and Ti). These rocks are MgO-rich (1.90-3.80 wt.%; Mg# = 37-72), with high Sr/Y, La/Yb and Ba/Th ratios, positive εNd(t) (6.31-6.84) and εHf(t) (13.26-16.40), low (87Sr/86Sr)i (0.7037-0.7039), and low Nb/U and Ta/U ratios. The data suggest that the quartz diorite was generated by the partial melting of subducted juvenile oceanic slab. The oxygen fugacity (ƒO2) of the quartz diorite, calculated by zircon Ce4+/Ce3+ ratios, is higher than that of the granite and pyroxene diorite, implying that the quartz diorite was more favorable to porphyry Cu mineralization. The Carboniferous Yuhai granite reveals similar geochemical features with the quartz diorite, except for the lower Mg# (27-33), and the more elevated Th/U and Th/La ratios. Furthermore, these rocks also show high εNd(t) (5.2-5.8) and εHf(t) (11.03-14.85) values, and low (87Sr/86Sr)i (0.7036-0.7037). These features indicate that the parental magma of the granite was probably derived from a juvenile lower crust with no significant mantle component involvement. Different from the Yuhai quartz diorite and granite, the early Permian Yuhai pyroxene diorite contains low SiO2 (50.76-55.74 wt.%) and high MgO (3.96-4.33 wt.%; Mg# = 40-44). The εNd(t), εHf(t) and (87Sr/86Sr)i values of the pyroxene diorite are 5.77-6.42, 7.99-12.10 and 0.7035-0.7040, respectively. The

  4. Geology and geochemistry of epithermal precious metal vein systems in the intra-oceanic arcs of Palau and Yap, western Pacific

    Science.gov (United States)

    Rytuba, J.J.; Miller, W.R.

    1990-01-01

    The Palau and Yap arcs are part of an intra-oceanic island-arc-trench system which separates the Pacific and Philippine plates in the western Pacific Ocean. The 350-km-long Palau arc consists of over 200 islands while the 400-km-long Yap arc located to the north has only four major islands exposed. Four of the largest islands in Palau are composed primarily of early Eocene to mid-Miocene volcanic rocks and the four islands comprising Yap contain only Miocene volcanic rocks. Basalt and basaltic andesites of the Babelthuap Formation are the oldest volcanic rocks in Palau and are characterized by high MgO, Ni and Cr and low TiO2 and have a boninitic affinity. They form the central and southeastern parts of Babelthuap Island. Oligocene arc tholeiite flows having an age of 34-35.5 Ma comprise most of the three smaller volcanic islands in Palau and the western part of Babelthuap. The youngest volcanic rocks are dacitic intrusions having an age of 22.7-23.2 Ma. The Yap arc is unusual in that metamorphic rocks up to amphibolite grade form most of the islands. These are underlain by a melange composed of igneous and volcanic clasts as well as clasts from a dismembered copper-gold skarn deposit. Miocene volcanic rocks consisting of flows and volcaniclastic deposits overlie the melange and metamorphic complex. An epithermal precious-metal vein system hosted by flows and flow breccias of the Babelthuap Formation occurs in an area 1.5 km by 1 km on the southeast side of Babelthuap Island. Over 50 veins and mineralized breccias ranging up to 2 m in width and having a strike length up to 500 m contain from trace to 13.0 ppm gold. The veins consist of quartz with varying amounts of sulfides and iron oxides after sulfides and the mineralized breccias consist of brecciated country rock cemented by quartz and iron oxides after sulfides. The veins and mineralized breccias generally dip within 15?? of vertical and have two preferred orientations, north-northwest and north

  5. Cs-137 geochronology, epithermal neutron activation analysis, and principal component analysis of heavy metals pollution of the Black Sea anoxic continental shelf sediments

    Science.gov (United States)

    Duliu, O. G.; Cristache, C.; Oaie, G.; Culicov, O. A.; Frontasyeva, M. V.

    2009-04-01

    Anthropogenic Cs-137 Gamma-ray Spectroscopy assay (GrSA) performed at the National Institute of Research and Development for Physics and Nuclear Engineering - Bucharest (Romania) in correlation with Epithermal Neutrons Activation Analysis (ENAA) performed at the Joint Institute of Nuclear Researches - Dubna (Russia) were used to investigate a 50 cm core containing unconsolidated sediments collected at a depth of 600 m off Romanian town of Constantza, located in the anoxic zone of the Black Sea Continental Shelf. A digital radiography showed the presence of about 265 distinct laminae, 1 to 3 mm thick, a fact attesting a stationary sedimentary process, completely free of bioturbation. After being radiographed, the core was sliced into 45 segments whose thickness gradually increased from 0.5 to 5 cm, such that the minimum thickness corresponded to the upper part of the core. From each segment two aliquots of about 0.5 g and 50 g were extracted for subsequent ENAA and Cs-137 GrSA. The Cs-137 vertical profile evidenced two maxima, one of them was very sharp and localized at a depth of 1 cm and the other very broad, almost undistinguished at about 8 cm depth, the first one being attributed to 1986 Chernobyl accident. Based on these date, we have estimated a sedimentation ratio of about 0.5 mm/year, value taken as reference for further assessment of recent pollution history. By means of ENAA we have determined the vertical content of five presumed pollutants, e.i. Zn, As, Br, Sn and Sb and of Sc, as natural, nonpolluting element. In the first case, all five elements presented a more or less similar vertical profile consisting of an almost exponential decrease for the first 10 cm below sediment surface followed by a plateau until the core base, i.e. 50 cm below surface, dependency better described by the equation: c(z) = c0 [1+k exp (-z/Z)] (1) where: where c(z) represents the concentration vertical profile; z represents depth (in absolute value); c0 represents the plateau

  6. Late Paleozoic to Mesozoic extension in southwestern Fujian Province, South China: Geochemical, geochronological and Hf isotopic constraints from basic-intermediate dykes

    Directory of Open Access Journals (Sweden)

    Sen Wang

    2017-05-01

    Full Text Available The tectonic evolution of SE China block since late Paleozoic remains debated. Here we present a new set of zircon U-Pb geochronological, Lu-Hf isotopic data and whole-rock geochemistry for two stages of basic-intermediate dykes from the southwestern Fujian. The samples were collected from the NE-trending (mainly diabases and NW-trending (mainly diabasic diorites dykes and yielded zircon U-Pb ages of 315 and 141 Ma, with εHf (t values of −8.90 to 7.49 and −23.39 to −7.15 (corresponding to TDM2 values of 850 to 1890 Ma and 737 to 2670 Ma, respectively. Geochemically these rocks are characterized by low TiO2 (0.91–1.73 wt.% and MgO (3.04–7.96 wt.%, and high Al2O3 (12.5–16.60 wt.% and K2O (0.60–3.63 wt.%. Further they are enriched in LREEs and LILEs (Rb, Ba, Th and K, but depleted in HFSEs (Nb, Ta and Zr. The tectonic discrimination analysis revealed that the dykes were formed in an intraplate extensional environment. However, the NW trending dykes show crust-mantle mixed composition, which indicate an extensional tectonic setting with evidence for crustal contamination. The SE China block experienced two main stages of extensional tectonics from late Carboniferous to early Cretaceous. The tectonic evolution of the SE China block from late Devonian to Cretaceous is also evaluated.

  7. Closure Time of the Junggar-Balkhash Ocean: Constraints From Late Paleozoic Volcano-Sedimentary Sequences in the Barleik Mountains, West Junggar, NW China

    Science.gov (United States)

    Liu, Bo; Han, Bao-Fu; Chen, Jia-Fu; Ren, Rong; Zheng, Bo; Wang, Zeng-Zhen; Feng, Li-Xia

    2017-12-01

    The Junggar-Balkhash Ocean was a major branch of the southern Paleo-Asian Ocean. The timing of its closure is important for understanding the history of the Central Asian Orogenic Belt. New sedimentological and geochronological data from the Late Paleozoic volcano-sedimentary sequences in the Barleik Mountains of West Junggar, NW China, help to constrain the closure time of the Junggar-Balkhash Ocean. Tielieketi Formation (Fm) is dominated by littoral sediments, but its upper glauconite-bearing sandstone is interpreted to deposit rapidly in a shallow-water shelf setting. By contrast, Heishantou Fm consists chiefly of volcanic rocks, conformably overlying or in fault contact with Tielieketi Fm. Molaoba Fm is composed of parallel-stratified fine sandstone and sandy conglomerate with graded bedding, typical of nonmarine, fluvial deposition. This formation unconformably overlies the Tielieketi and Heishantou formations and is conformably covered by Kalagang Fm characterized by a continental bimodal volcanic association. The youngest U-Pb ages of detrital zircons from sandstones and zircon U-Pb ages from volcanic rocks suggest that the Tielieketi, Heishantou, Molaoba, and Kalagang formations were deposited during the Famennian-Tournaisian, Tournaisian-early Bashkirian, Gzhelian, and Asselian-Sakmarian, respectively. The absence of upper Bashkirian to Kasimovian was likely caused by tectonic uplifting of the West Junggar terrane. This is compatible with the occurrence of coeval stitching plutons in the West Junggar and adjacent areas. The Junggar-Balkhash Ocean should be finally closed before the Gzhelian, slightly later or concurrent with that of other ocean domains of the southern Paleo-Asian Ocean.

  8. Shear Wave Splitting analysis of borehole microseismic reveals weak azimuthal anisotropy hidden behind strong VTI fabric of Lower Paleozoic shales in northern Poland

    Science.gov (United States)

    Gajek, Wojciech; Verdon, James; Malinowski, Michał; Trojanowski, Jacek

    2017-04-01

    Azimuthal anisotropy plays a key-role in hydraulic fracturing experiments, since it provides information on stress orientation and pre-existing fracture system presence. The Lower Paleozoic shale plays in northern Poland are characterized by a strong (15-18%) Vertical Transverse Isotropy (VTI) fabric which dominates weak azimuthal anisotropy being of order of 1-2%. A shear wave travelling in the subsurface after entering an anisotropic medium splits into two orthogonally polarized waves travelling with different velocities. Splitting parameters which can be assessed using a microseismic array are polarization of the fast shear wave and time delay between two modes. Polarization of the fast wave characterizes the anisotropic system on the wave path while the time delay is proportional to the magnitude of anisotropy. We employ Shear Wave Splitting (SWS) technique using a borehole microseismic dataset collected during a hydraulic stimulation treatment located in northern Poland, to image fracture strike masked by a strong VTI signature. During the inversion part, the VTI background parameters were kept constant using information from 3D seismic (VTI model used for pre-stack depth migration). Obtained fracture azimuths averaged over fracturing stages are consistent with the available XRMI imager logs from the nearby vertical well, however they are different from the large-scale maximum stress direction (by 40-45 degrees). Inverted Hudson's crack density (ca. 2%) are compatible with the low shear-wave anisotropy observed in the cross-dipole sonic logs (1-2%). This work has been funded by the Polish National Centre for Research and Development within the Blue Gas project (No BG2/SHALEMECH/14). Data were provided by the PGNiG SA. Collaboration with University of Bristol was supported within TIDES COST Action ES1401.

  9. Devonian post-orogenic extension-related volcano-sedimentary rocks in the northern margin of the Tibetan Plateau, NW China: Implications for the Paleozoic tectonic transition in the North Qaidam Orogen

    Science.gov (United States)

    Qin, Yu; Feng, Qiao; Chen, Gang; Chen, Yan; Zou, Kaizhen; Liu, Qian; Jiao, Qianqian; Zhou, Dingwu; Pan, Lihui; Gao, Jindong

    2018-05-01

    The Maoniushan Formation in the northern part of the North Qaidam Orogen (NQO), NW China, contains key information on a Paleozoic change in tectonic setting of the NQO from compression to extension. Here, new zircon U-Pb, petrological, and sedimentological data for the lower molasse sequence of the Maoniushan Formation are used to constrain the timing of this tectonic transition. Detrital zircons yield U-Pb ages of 3.3-0.4 Ga with major populations at 0.53-0.4, 1.0-0.56, 2.5-1.0, and 3.3-2.5 Ga. The maximum depositional age of the Maoniushan Formation is well constrained by a youngest detrital zircon age of ∼409 Ma. Comparing these dates with geochronological data for the region indicates that Proterozoic-Paleozoic zircons were derived mainly from the NQO as well as the Oulongbuluk and Qaidam blocks, whereas Archean zircons were probably derived from the Oulongbuluk Block and the Tarim Craton. The ∼924, ∼463, and ∼439 Ma tectonothermal events recorded in this region indicate that the NQO was involved in the early Neoproterozoic assembly of Rodinia and early Paleozoic microcontinental convergence. A regional angular unconformity between Devonian and pre-Devonian strata within the NQO suggests a period of strong mountain building between the Oulongbuluk and Qaidam blocks during the Silurian, whereas an Early Devonian post-orogenic molasse, evidence of extensional collapse, and Middle to Late Devonian bimodal volcanic rocks and Carboniferous marine carbonate rocks clearly reflect long-lived tectonic extension. Based on these results and the regional geology, we suggest that the Devonian volcano-sedimentary rocks within the NQO were formed in a post-orogenic extensional setting similar to that of the East Kunlun Orogen, indicating that a major tectonic transition from compression to extension in these two orogens probably commenced in the Early Devonian.

  10. Executive summary--2002 assessment of undiscovered oil and gas resources in the San Juan Basin Province, exclusive of Paleozoic rocks, New Mexico and Colorado: Chapter 1 in Total petroleum systems and geologic assessment of undiscovered oil and gas resources in the San Juan Basin Province, exclusive of Paleozoic rocks, New Mexico and Colorado

    Science.gov (United States)

    ,

    2013-01-01

    In 2002, the U.S. Geological Survey (USGS) estimated undiscovered oil and gas resources that have the potential for additions to reserves in the San Juan Basin Province (5022), New Mexico and Colorado (fig. 1). Paleozoic rocks were not appraised. The last oil and gas assessment for the province was in 1995 (Gautier and others, 1996). There are several important differences between the 1995 and 2002 assessments. The area assessed is smaller than that in the 1995 assessment. This assessment of undiscovered hydrocarbon resources in the San Juan Basin Province also used a slightly different approach in the assessment, and hence a number of the plays defined in the 1995 assessment are addressed differently in this report. After 1995, the USGS has applied a total petroleum system (TPS) concept to oil and gas basin assessments. The TPS approach incorporates knowledge of the source rocks, reservoir rocks, migration pathways, and time of generation and expulsion of hydrocarbons; thus the assessments are geologically based. Each TPS is subdivided into one or more assessment units, usually defined by a unique set of reservoir rocks, but which have in common the same source rock. Four TPSs and 14 assessment units were geologically evaluated, and for 13 units, the undiscovered oil and gas resources were quantitatively assessed.

  11. Geochronological and sedimentological evidences of Panyangshan foreland basin for tectonic control on the Late Paleozoic plate marginal orogenic belt along the northern margin of the North China Craton

    Science.gov (United States)

    Li, Jialiang; Zhou, Zhiguang; He, Yingfu; Wang, Guosheng; Wu, Chen; Liu, Changfeng; Yao, Guang; Xu, Wentao; Zhao, Xiaoqi; Dai, Pengfei

    2017-08-01

    There is a wide support that the Inner Mongolia Palaeo-uplift on the northern margin of the North China Craton has undergone an uplifting history. However, when and how did the uplift occurred keeps controversial. Extensive field-based structural, metamorphic, geochemical, geochronological and geophysical investigations on the Inner Mongolia Palaeo-uplift, which suggested that the Inner Mongolia Palaeo-uplift was an uplifted region since the Early Precambrian or range from Late Carboniferous-Early Jurassic. The geochemical characteristics of the Late Paleozoic to Early Mesozoic intrusive rocks indicated that the Inner Mongolia Palaeo-uplift was an Andean-type continental margin that is the extensional tectonic setting. To address the spatial and temporal development of the Inner Mongolia Palaeo-uplift, we have carried out provenance analysis of Permian sedimentary rocks which collected from the Panyangshan basin along the northern margin of the North China Craton. The QFL diagram revealed a dissected arc-recycled orogenic tectonic setting. Moreover, the framework grains are abundant with feldspar (36-50%), indicating the short transport distance and unstable tectonic setting. Detrital zircon U-Pb analysis ascertained possible provenance information: the Precambrian basement ( 2490 and 1840 Ma) and continental arc magmatic action ( 279 and 295 Ma) along the northern margin of the North China Craton. The projection in rose diagrams of the mean palaeocurrent direction, revealing the SSW and SSE palaeoflow direction, also shows the provenance of the Panyangshan basin sources mainly from the Inner Mongolia Palaeo-uplift. The andesite overlying the Naobaogou Formation has yielded U-Pb age of 277.3 ± 1.4 Ma. The additional dioritic porphyry dike intruded the Naobaogou and Laowopu Formations, which has an emplacement age of 236 ± 1 Ma. The above data identify that the basin formed ranges from Early Permian to Middle Triassic (277-236 Ma). Accordingly, the Inner Mongolia

  12. Silurian extension in the Upper Connecticut Valley, United States and the origin of middle Paleozoic basins in the Québec embayment

    Science.gov (United States)

    Rankin, D.W.; Coish, R.A.; Tucker, R.D.; Peng, Z.X.; Wilson, S.A.; Rouff, A.A.

    2007-01-01

    Pre-Silurian strata of the Bronson Hill arch (BHA) in the Upper Connecticut Valley, NH-VT are host to the latest Ludlow Comerford Intrusive Suite consisting, east to west, of a mafic dike swarm with sheeted dikes, and an intrusive complex. The rocks are mostly mafic but with compositions ranging from gabbro to leucocratic tonalite. The suite is truncated on the west by the Monroe fault, a late Acadian thrust that carries rocks of the BHA westward over Silurian-Devonian strata of the Connecticut Valley-Gaspe?? trough (CVGT). Dikes intrude folded strata with a pre-intrusion metamorphic fabric (Taconian?) but they experienced Acadian deformation. Twenty fractions of zircon and baddeleyite from three sample sites of gabbrodiorite spanning nearly 40 km yield a weighted 207Pb/206Pb age of 419 ?? 1 Ma. Greenschist-facies dikes, sampled over a strike distance of 35 km, were tholeiitic basalts formed by partial melting of asthenospheric mantle, with little or no influence from mantle or crustal lithosphere. The dike chemistry is similar to mid-ocean ridge, within-plate, and back-arc basin basalts. Parent magmas originated in the asthenosphere and were erupted through severely thinned lithosphere adjacent to the CVGT. Extensive middle Paleozoic basins in the internides of the Appalachian orogen are restricted to the Que??bec embayment of the Laurentian rifted margin, and include the CVGT and the Central Maine trough (CMT), separated from the BHA by a Silurian tectonic hinge. The NE-trending Comerford intrusions parallel the CVGT, CMT, and the tectonic hinge, and indicate NW-SE extension. During post-Taconian convergence, the irregular margins of composite Laurentia and Avalon permitted continued collision in Newfoundland (St. Lawrence promontory) and coeval extension in the Que??bec embayment. Extension may be related to hinge retreat of the northwest directed Brunswick subduction complex and rise of the asthenosphere following slab break-off. An alternative hypothesis is

  13. U-Pb SHRIMP-RG zircon ages and Nd signature of lower Paleozoic rifting-related magmatism in the Variscan basement of the Eastern Pyrenees

    Science.gov (United States)

    Martinez, F.J.; Iriondo, A.; Dietsch, C.; Aleinikoff, J.N.; Peucat, J.J.; Cires, J.; Reche, J.; Capdevila, R.

    2011-01-01

    The ages of orthogneisses exposed in massifs of the Variscan chain can determine whether they are part of a pre-Neoproterozoic basement, a Neoproterozoic, Panafrican arc, or are, in fact, lower Paleozoic, and their isotopic compositions can be used to probe the nature of their source rocks, adding to the understanding of the types, distribution, and tectonic evolution of peri-Gondwanan crystalline basement. Using SHRIMP U-Pb zircon geochronology and Nd isotopic analysis, pre-Variscan metaigneous rocks from the N??ria massif in the Eastern Pyrenean axial zone and the Guilleries massif, 70km to the south, have been dated and their Nd signatures characterized. All dated orthogneisses from the N??ria massif have the same age within error, ~457Ma, including the Ribes granophyre, interpreted as a subvolcanic unit within Caradocian sediments contemporaneous with granitic magmas intruded into Cambro-Ordovician sediments at deeper levels. Orthogneisses in the Guilleries massif record essentially continuous magmatic activity during the Ordovician, beginning at the Cambro-Ordovician boundary (488??3Ma) and reaching a peak in the volume of magma in the early Late Ordovician (~460Ma). Metavolcanic rocks in the Guilleries massif were extruded at 452??4Ma and appear to have their intrusive equivalent in thin, deformed veins of granitic gneiss (451??7Ma) within metasedimentary rocks. In orthogneisses from both massifs, the cores of some zircons yield Neoproterozoic ages between ~520 and 900Ma. The age of deposition of a pre-Late Ordovician metapelite in the Guilleries massif is bracketed by the weighted average age of the youngest detrital zircon population, 582??11Ma, and the age of cross-cutting granitic veins, 451??7Ma. Older detrital zircons populations in this metapelite include Neoproterozoic (749-610Ma; n=10), Neo- to Mesoproterozoic (1.04-0.86Ga; n=7), Paleoproterozoic (2.02-1.59Ga; n=5), and Neoarchean (2.74-2.58Ga; n=3). Nd isotopic analyses of the N??ria and Guilleries

  14. Lower Paleozoic deep-water facies of the Medfra area, central Alaska: A section in Geologic studies in Alaska by the U.S. Geological Survey, 1997

    Science.gov (United States)

    Dumoulin, Julie A.; Bradley, Dwight C.; Harris, Anita G.; Repetski, John E.

    1999-01-01

    Deep-water facies, chiefly hemipelagic deposits and turbidites, of Cambrian through Devonian age are widely exposed in the Medfra and Mt. McKinley quadrangles. These strata include the upper part of the Telsitna Formation (Middle-Upper Ordovician) and the Paradise Fork Formation (Lower Silurian-Lower Devonian) in the Nixon Fork terrane, the East Fork Hills Formation (Upper Cambrian-Lower Devonian) in the East Fork subterrane of the Minchumina terrane, and the chert and argillite unit (Ordovician) and the argillite and quartzite unit (Silurian- Devonian? and possibly older) in the Telida subterrane of the Minchumina terrane.In the western part of the study area (Medfra quadrangle), both hemipelagic deposits and turbidites are largely calcareous and were derived from the Nixon Fork carbonate platform. East- ern exposures (Mt. McKinley quadrangle; eastern part of the Telida subterrane) contain much less carbonate; hemipelagic strata are mostly chert, and turbidites contain abundant rounded quartz and lesser plagioclase and potassium feldspar. Deep-water facies in the Medfra quadrangle correlate well with rocks of the Dillinger terrane exposed to the south (McGrath quadrangle), but coeval strata in the Mt. McKinley quadrangle are compositionally similar to rocks to the northeast (Livengood quadrangle). Petrographic data thus suggest that the Telida subterranes presently defined is an artificial construct made up of two distinct sequences of disparate provenance.Restoration of 90 and 150 km of dextral strike-slip on the Iditarod and Farewell faults, respectively, aligns the deep-water strata of the Minchumina and Dillinger terranes in a position east of the Nixon Fork carbonate platform. This restoration supports the interpretation that lower Paleozoic rocks in the Nixon Fork and Dillinger terranes, and in the western part of the Minchumina terrane (East Fork subterrane and western part of the Telida subterrane), formed along a single continental margin. Rocks in the

  15. NEW PALEOMAGNETIC DATA ON THE SILURIAN AND DEVONIAN SEDIMENTARY ROCKS FROM PODOLIA, SW UKRAINE, AND KINEMATICS OF THE EAST EUROPEAN PLATFORM IN THE MIDDLE PALEOZOIC

    Directory of Open Access Journals (Sweden)

    V. G. Bakhmutov

    2014-01-01

    Full Text Available Paleomagnetic data are the priority source of information for global paleotectonic reconstructions representing horizontal movements of the crustal blocks. Upon receipt of new paleomagnetic data, kinematic models of the East European platform in the Paleozoic are regularly revised and improved. The article presents results of the paleomagnetic study of sedimentary gray-colored and red beds of the Silurian and Lower Devonian sequences located in the Dniester river basin, Podolia region, SW Ukraine. The study covered 17 outcrops that are stratigraphically correlated with the Wenlock, Ludlow, Pridoli states of the Sillurian and the Lochkovian stage of the Devon. Over 400 samples of grey limestone, argillite, dolomite, red limestone and sandstone were analyzed, and two components of natural remnant magnetization (NRM were revealed. The first component with SSW declination and negative inclination is revealed in the majority of the samples during AF- and T-magnetic cleaning. Its pole positions, that are calculated separately for each series, are trending to the Permian segment of the apparent polar wander path (APWP published by Torsvik et al. [2012] for Baltica / Stable Europe. Considering its chemical origin, this NRM component is related to formation of authigenic minerals due to rock remagnetization. The second component is revealed only in some samples taken from the red beds (during thermal demagnetization in the range of unblocking temperatures from 590 to 690 °С and in few samples of grey limestone (in AF fields from 30 to 70 mT or in the range of unblocking temperatures from 300 to 460 °С. This component has SW declination and positive inclination, goes to the origin of coordinates of the diagrams, and has all the indicators of primary magnetization of sediments. Calculated positions of the poles (0 ºS and 329 ºE for grey limestone of the Tiverskaya series, 2.3 °S and 338.4 °E for red beds of the Dniestrovskaya series, etc. are well

  16. Petrogenesis of late Paleozoic-to-early Mesozoic granitoids and metagabbroic rocks of the Tengchong Block, SW China: implications for the evolution of the eastern Paleo-Tethys

    Science.gov (United States)

    Zhu, Ren-Zhi; Lai, Shao-Cong; Qin, Jiang-Feng; Zhao, Shao-Wei

    2018-03-01

    This paper presents precise zircon U-Pb, bulk-rock geochemical, and Sr-Nd-Pb isotopic data for metagabbro, quartz diorite, and granite units within the Tengchong Block of SW China, which forms the southeastern extension of the Himalayan orogeny and the southwestern section of the Sanjiang orogenic belt, a key region for furthering our understanding of the evolution of the eastern Paleo-Tethys. These data reveal four groups of zircon U-Pb ages that range from the late Paleozoic to the early Mesozoic, including a 263.6 ± 3.6 Ma quartz diorite, a 218.5 ± 5.4 Ma two-mica granite, a 205.7 ± 3.1 Ma metagabbroic unit, and a 195.5 ± 2.2 Ma biotite granite. The quartz diorite in this area contains low concentrations of SiO2 (60.71-64.32 wt%), is sodium-rich, and is metaluminous, indicating formation from magmas generated by a mixed source of metamafic rocks with a significant metapelitic sedimentary material within lower arc crust. The two-mica granites contain high concentrations of SiO2 (73.2-74.3 wt%), are strongly peraluminous, and have evolved Sr-Nd-Pb isotopic compositions, all of which are indicative of a crustal source, most probably from the partial melting of felsic pelite and metagreywacke/psammite material. The metagabbros contain low concentrations of SiO2 (50.17-50.96 wt%), are sodium-rich, contain high concentrations of Fe2O3T (9.79-10.06 wt%) and CaO (6.88-7.12 wt%), and are significantly enriched in the Sr (869-894 ppm) and LREE (198.14-464.60 ppm), indicative of derivation from magmas generated by a metasomatized mantle wedge modified by the sedimentary-derived component. The biotite granites are weakly peraluminous and formed from magmas generated by melting of metasedimentary sources dominated by metagreywacke/psammite material. Combining the petrology and geochemistry of these units with the regional geology of the Indosinian orogenic belt provides evidence for two stages of magmatism: an initial stage that generated magmas during partial melting of

  17. Mineralogical and geochemical characteristics of uranium-rich fluoriteinEl-Missikat mineralized granite,Central Eastern Desert, Egypt

    Directory of Open Access Journals (Sweden)

    Mohamed Fahmy Raslan

    2009-12-01

    Full Text Available A unique, highly radioactive variety of fluor it emineral has been recorded in the uranium occurrence of El-Missikat sheared granite pluton. In this occurrence, the uranium assumes different forms, including its presence as discrete, visible, secondary minerals, rare uraninite and its association with the jasperoid and silica veinlets. However,in some other parts of the sheared zone, the uranium was found to be solely incorporated with fluorite crystals,filling veinlet sand fractures with out any other manife station.This paper focuses ont her elevant mineralogical and geochemical characteristics of this unique fluorite variety.In addition to an investigation with binocular and polarizing microscopes, the separated fluorite grains were analyzed usingan environmental scanning electronmicroscope(ESEM and a field-emission scanning electron microscope.In addition to this,some fluorite crystals were subjected to electron microprobe analyses. While the fluorite accounted for as much as 20% of the sheared granite samples studied, it was found to range from 82 to 96 % in the different size fractions of the separated heavy mineral content. In some parts of the separated fluorite crystals,uranium inquantities of up to 2200 ppm was found to be heterogeneously distributed in the fluoritelattice,regardless of its coloration.

  18. Palynological study (spores, Acritarchs and Chitinozoans) in the paleozoic (Cambrian to Dinantian) of western and meridional Morocco (biostratigraphy, paleo-bio-geography and characterisation of organic matter); Etude palynologique (spores, Chitinozoaires, Acritarches) dans le Paleozoique: Cambrien a Dinantien du Maroc occidental et meridional (biostratigraphie, paleobiogeographie et caracterisation de la matiere organique)

    Energy Technology Data Exchange (ETDEWEB)

    Rahmani, K.

    1995-01-27

    The palynological study of paleozoic levels in ten wells and two cross sections in western and meridional Morocco has permit to establish the inventory of organic micro-fossils. Some of these are spores and Acritarchs which constitute much rich and more conserved than to Chitinozoans. The different associations yield from the middle Cambrian to the lower Carboniferous have allowed the setting of a bio-zonation. This latter, consists of 7 biozones based on Carboniferous and Acritarchs in the lower Paleozoic, and 12 biozones in the Devonian and lower Carboniferous based essentially on the spores. This bio-zonation however, does not provide full information. This is due to the degradation of the micro-fossils, their absence of an unsuitable facies, a shortage of samples, erosion or lack of sedimentation. Most of these short comings were dated and their importance was considered in relation to the different epeirogeny known in Morocco. The biozones distinguished were based on index taxa of spores, Chitinozoans or Acritarchs which coexist with biostratigraphic micro-fossils in Morocco or in others regions referred to. This biozones allowed: the indication of the precision of many subdivisions within the Paleozoic of the studied areas the setting of local, regional and intercontinental correlations, subsequently: Anti-Atlas, Moroccan Meseta, Algeria, Libya, North, America, Canada and Europe. The paleo-bio-geographic evolution traced from the middle Cambrian to the lower Carboniferous has demonstrated that the position of Morocco between north Gondwana and Avalonia zone at the lower Paleozoic and between Africa and Europe during the upper Paleozoic, has associated this area to different geological phenomena. Morocco also constituted a paleo-bio-geographic bridge which has allowed diverse exchanges, especially floristic one, between the Gondvanian and the Laurasian domains. This privileged position of Morocco in the geographic and geologic line has certainly influenced the

  19. Neoproterozoic-Early Paleozoic Peri-Pacific Accretionary Evolution of the Mongolian Collage System: Insights From Geochemical and U-Pb Zircon Data From the Ordovician Sedimentary Wedge in the Mongolian Altai

    Science.gov (United States)

    Jiang, Y. D.; Schulmann, K.; Kröner, A.; Sun, M.; Lexa, O.; Janoušek, V.; Buriánek, D.; Yuan, C.; Hanžl, P.

    2017-11-01

    Neoproterozoic to early Paleozoic accretionary processes of the Central Asian Orogenic Belt have been evaluated so far mainly using the geology of ophiolites and/or magmatic arcs. Thus, the knowledge of the nature and evolution of associated sedimentary prisms remains fragmentary. We carried out an integrated geological, geochemical, and zircon U-Pb geochronological study on a giant Ordovician metasedimentary succession of the Mongolian Altai Mountains. This succession is characterized by dominant terrigenous components mixed with volcanogenic material. It is chemically immature, compositionally analogous to graywacke, and marked by significant input of felsic to intermediate arc components, pointing to an active continental margin depositional setting. Detrital zircon U-Pb ages suggest a source dominated by products of early Paleozoic magmatism prevailing during the Cambrian-Ordovician and culminating at circa 500 Ma. We propose that the Ordovician succession forms an "Altai sedimentary wedge," the evolution of which can be linked to the geodynamics of the margins of the Mongolian Precambrian Zavhan-Baydrag blocks. This involved subduction reversal from southward subduction of a passive continental margin (Early Cambrian) to the development of the "Ikh-Mongol Magmatic Arc System" and the giant Altai sedimentary wedge above a north dipping subduction zone (Late Cambrian-Ordovician). Such a dynamic process resembles the tectonic evolution of the peri-Pacific accretionary Terra Australis Orogen. A new model reconciling the Baikalian metamorphic belt along the southern Siberian Craton with peri-Pacific Altai accretionary systems fringing the Mongolian microcontinents is proposed to explain the Cambro-Ordovician geodynamic evolution of the Mongolian collage system.

  20. Unconventional Gas Resources in the Paleozoic of Central Europe Ressources de gaz non conventionnels dans le Paléozoïque de l’Europe Centrale

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    Littke R.

    2011-05-01

    Full Text Available Whereas gas production from unconventional reserves has greatly increased over the past decades, there is still a largely unexplored potential in the Paleozoic of Central Europe. For this area, the paper summarizes some important aspects of the geology of tight sandstone gas reservoirs, gas shales and coalbed methane. Tight sandstones with low permeabilities are especially present in the Permian (Rotliegend Formation of The Netherlands and northern Germany, but also in the underlying Carboniferous. There is already active production from some of these reservoirs. Further development greatly depends on understanding of gas charge as well as the regional distribution of porosity and permeability which in turn depend on facies and diagenesis. In contrast exploration for gas shales is just at the very beginning. Whereas Mesozoic shales in the southern Lower Saxony Basin have to be regarded as prime targets due to thickness, maturity and organic matter content, there are additional targets in the Mississippian, but also in older rocks. Currently an international gas shale research programme (Gas shales in Europe, GASH gathers relevant data for these units. Coalbed methane exploration started already about 20 years ago in the Ruhr Basin, but was not successful at that time due to small flow rates. On the other hand, production from abandoned coal mines provided substantial amounts of gas. Due to the abundance of coal seams and the suitable maturity conditions and gas contents, there is a high potential for future substantial coalbed methane in the area. Alors que l’extraction du gaz naturel des gisements non conventionnels a fortement augmenté ces dernières dizaines d’années, un large potentiel de ressources reste inexploré dans les couches paléozoïques de l’Europe Centrale. Cet article présente, pour cette région, quelques aspects importants de la géologie des grès de faible perméabilité (tight gas sands, des gaz de schiste (gas

  1. Late Paleozoic closure of the Ob-Zaisan Ocean along the Irtysh/Chara shear zone and implications for arc amalgamation and oroclinal bending in the western Central Asian Orogenic Belt

    Science.gov (United States)

    Li, Pengfei; Sun, Min; Rosenbaum, Gideon

    2016-04-01

    The Irtysh/Chara Shear Zone is one of the largest strike-slip systems in the Central Asian Orogenic Belt (CAOB). It records collisional processes of the peri-Siberian orogenic system with the West Junggar-Kazakhstan-Tianshan orogenic system following the closure of the Ob-Zaisan Ocean, but the exact timing of these events remains enigmatic. We conducted detailed structural analysis along the Irtysh Shear Zone (NW China), which together with new geochronological data allows us to reconstruct the tectonic evolution during the final closure of the Ob-Zaisan Ocean. Our results showed that subduction-accretion processes lasted at least until the Late Carboniferous in the Chinese Altai and the East/West Junggar. The subsequent arc amalgamation is characterized by a cycle of crustal thickening, orogenic collapse and transpressional thickening. On a larger scale, the West Junggar- Kazakhstan -Tianshan orogenic system defines a U-shape oroclinal structure (e.g. Xiao et al., 2010). A major phase of oroclinal bending that involved ~110° rotation may have occurred during the Late Devonian to Early Carboniferous (Levashova et al., 2012). Previous authors have linked oroclinal bending with the late Paleozoic amalgamation of the western CAOB, and proposed that a quasi-linear West Junggar- Kazakhstan -Tianshan orogenic system was buckled during the convergence of the Siberian and Tarim cratons following the closure of the Ob-Zaisan Ocean (in the north) and the South Tianshan Ocean (in the south) (e.g. Abrajevitch et al., 2008). This model, however, is not supported by our new data that constrain the closure of the Ob-Zaisan Ocean to the Late Carboniferous. Alternatively, we propose that oroclinal bending may have involved two phases of bending, with the ~110° rotation in the Late Devonian to Early Carboniferous possibly associated with trench retreat. Further tightening may have occurred in response to the convergence of the Siberian and Tarim cratons during the Late

  2. Early Paleozoic dioritic and granitic plutons in the Eastern Tianshan Orogenic Belt, NW China: Constraints on the initiation of a magmatic arc in the southern Central Asian Orogenic Belt

    Science.gov (United States)

    Du, Long; Long, Xiaoping; Yuan, Chao; Zhang, Yunying; Huang, Zongying; Sun, Min; Zhao, Guochun; Xiao, Wenjiao

    2018-03-01

    Early Paleozoic dioritic and granitic plutons in the Eastern Tianshan Orogenic Belt (ETOB) have been studied in order to constraint the initiation of a magmatic arc formed in this region. Zircon U-Pb dating indicates that two dioritic plutons in the northern ETOB were generated in the Late Ordovician (452 ± 4 Ma) and the Early Silurian (442 ± 3 Ma), respectively. Diorites from the two plutons are characterized by enrichments in large ion lithophile elements (LILE) and highly incompatible elements, with depletions in high field strength elements (HSFE) displaying typical geochemical features of a subduction-related origin. They have positive εNd(t) values (+5.08-+6.58), relatively young Nd model ages (TDM = 0.71-1.08 Ga), with Ta/Yb (0.05-0.09) and Nb/Ta ratios (12.06-15.19) similar to those of depleted mantle, suggesting a juvenile mantle origin. Their high Ba/La (13.3-35.9), low Th/Yb (0.72-2.02), and relatively low Ce/Th (4.57-14.7) and Ba/Th (47.8-235) ratios indicate that these diorites were probably produced by partial melting of a depleted mantle wedge metasomatized by both subducted sediment-derived melts and slab-derived aqueous fluids. Zircon U-Pb dating of a granitic pluton in the northern ETOB yielded a Late Ordovician intrusion age of 447 ± 5 Ma. Granites from this pluton show calc-alkaline compositions with geochemical characteristics of I-type granites. They also show positive εNd(t) values (+6.49-+6.95) and young Nd model ages (TDM = 0.69-0.87 Ga), indicating that the granites were most likely derived from juvenile lower crust. Our new dating results on the dioritic and granitic plutons suggest that arc-type magmatism in the northern ETOB began prior to or at the Late Ordovician (452-442 Ma). In addition, north-dipping subduction of the Kangguertage oceanic lithosphere may account for the arc-type magmatism and the geodynamic process of the ETOB in the Early Paleozoic.

  3. Early paleozoic granitoids in the southern Vanoise basement: U-Pb geochronology of the Arpont meta-granite (Savoy, French Alps); Granitoides d`age paleozoique inferieur dans le socle de Vanoise meridionale: geochronologie U-Pb du metagranite de l`Arpont (Alpes de Savoir, France)

    Energy Technology Data Exchange (ETDEWEB)

    Bertrand, J.M. [Laboratoire de geodynamique des chaines alpines, LGCA-CISM, 73 - Le Bourget-du-Lac (France); Leterrier, J. [Centre de recherches petrographiques et geochimique, 54 - Vandoeuvre-les-Nancy (France)

    1997-12-01

    The U-Pb age of a meta-granite from southern Vanoise (Brianconnais` domain) at 479{+-} 4 Ma confirms hat the micaschists which dominate this pre-alpine basement are, at least, of Early Paleozoic age. The rare magmatic rocks occurring in Vanoise and showing alkaline affinities, may be compared to the orthogneisses belonging to the Cambrian-Ordovician extensional event well known in other parts of the Varican belt. (authors) 27 refs.

  4. Shahejie-Shahejie/Guantao/Wumishan and Carboniferous/Permian Coal-Paleozoic Total Petroleum Systems in the Bohaiwan Basin, China (based on geologic studies for the 2000 World Energy Assessment Project of the U.S. Geological Survey)

    Science.gov (United States)

    Ryder, Robert T.; Qiang, Jin; McCabe, Peter J.; Nuccio, Vito F.; Persits, Felix

    2012-01-01

    This report discusses the geologic framework and petroleum geology used to assess undiscovered petroleum resources in the Bohaiwan basin province for the 2000 World Energy Assessment Project of the U.S. Geological Survey. The Bohaiwan basin in northeastern China is the largest petroleum-producing region in China. Two total petroleum systems have been identified in the basin. The first, the Shahejie&ndashShahejie/Guantao/Wumishan Total Petroleum System, involves oil and gas generated from mature pods of lacustrine source rock that are associated with six major rift-controlled subbasins. Two assessment units are defined in this total petroleum system: (1) a Tertiary lacustrine assessment unit consisting of sandstone reservoirs interbedded with lacustrine shale source rocks, and (2) a pre-Tertiary buried hills assessment unit consisting of carbonate reservoirs that are overlain unconformably by Tertiary lacustrine shale source rocks. The second total petroleum system identified in the Bohaiwan basin is the Carboniferous/Permian Coal–Paleozoic Total Petroleum System, a hypothetical total petroleum system involving natural gas generated from multiple pods of thermally mature coal beds. Low-permeability Permian sandstones and possibly Carboniferous coal beds are the reservoir rocks. Most of the natural gas is inferred to be trapped in continuous accumulations near the center of the subbasins. This total petroleum system is largely unexplored and has good potential for undiscovered gas accumulations. One assessment unit, coal-sourced gas, is defined in this total petroleum system.

  5. Refined permo-triassic paleomagnetic pole for the Siberian platform and geomagnetic secular variations at the Paleozoic-Mesozoic boundary as recorded in volcanic traps key sections of northern Siberia

    Science.gov (United States)

    Pavlov, V. E.; Veselovskiy, R. V.; Khokhlov, A.; Latyshev, A. V.; fluteau, F.

    2011-12-01

    Two new volcanic key sections of the Siberian traps erupted ~ 250 million years ago have been studied in the Norilsk region (NW of the Siberian platform). Along with results obtained earlier from both this area (Heunemann et al., 2004) and Maymecha-Kotuy region (northern Siberian platform, Pavlov et al., 2011) these data constitute rather extensive database, including paleomagnetic information on about 200 volcanic flows. Using this information we can not only get refined permo-triassic paleomagnetic pole for the Siberian platform, based exceptionally on lava flows data, but also estimate amplitude of geomagnetic secular variation at the Paleozoic-Mesozoic boundary and check their compatibility with statistic models, suggested for description of recent (Late Cenozoic) Earth's magnetic field. Moreover, our results can be also used to obtain additional time constraints on duration of the trap emplacement and to isolate volcanic pulses within the traps sections. We present a report where we discuss all these topics. This work was supported by grants NSF # EAR 0807585 and RBRF #09-05-01180, 11-05-00601,10-05- 00557.

  6. A Cambrian mixed carbonate-siliciclastic platform in SW Gondwana: evidence from the Western Sierras Pampeanas (Argentina) and implications for the early Paleozoic paleogeography of the proto-Andean margin

    Science.gov (United States)

    Ramacciotti, Carlos D.; Casquet, César; Baldo, Edgardo G.; Galindo, Carmen; Pankhurst, Robert J.; Verdecchia, Sebastián O.; Rapela, Carlos W.; Fanning, Mark

    2018-05-01

    The Western Sierras Pampeanas (WSP) of Argentina record a protracted geological history from the Mesoproterozoic assembly of the Rodinia supercontinent to the early Paleozoic tectonic evolution of SW Gondwana. Two well-known orogenies took place at the proto-Andean margin of Gondwana in the Cambrian and the Ordovician, i.e., the Pampean (545-520 Ma) and Famatinian (490-440 Ma) orogenies, respectively. Between them, an extensive continental platform was developed, where mixed carbonate-siliciclastic sedimentation occurred. This platform was later involved in the Famatinian orogeny when it underwent penetrative deformation and metamorphism. The platform apparently extended from Patagonia to northwestern Argentina and the Eastern Sierras Pampeanas, and has probable equivalents in SW Africa, Peru, and Bolivia. The WSP record the outer (deepest) part of the platform, where carbonates were deposited in addition to siliciclastic sediments. Detrital zircon U-Pb SHRIMP ages from clastic metasedimentary successions and Sr-isotope compositions of marbles from the WSP suggest depositional ages between ca. 525 and 490 Ma. The detrital zircon age patterns further suggest that clastic sedimentation took place in two stages. The first was sourced mainly from re-working of the underlying Neoproterozoic metasedimentary rocks and the uplifted core of the early Cambrian Pampean orogen, without input from the Paleoproterozoic Río de la Plata craton. Sediments of the second stage resulted from the erosion of the still emerged Pampean belt and the Neoproterozoic Brasiliano orogen in the NE with some contribution from the Río de la Plata craton. An important conclusion is that the WSP basement was already part of SW Gondwana in the early Cambrian, and not part of the exotic Precordillera/Cuyania terrane, as was previously thought.

  7. Early Paleozoic U-Pb age of zircons from meta-granophyres f the Grand-Saint-Bernard nappe (zona interna, Aosta Valley, Italy); Age paleozoique inferieur (U-Pb sur zircon) de metagranophyres de la nappe du Grand-Saint-Bernard (zona interna, Vallee d'Aoste, Italie)

    Energy Technology Data Exchange (ETDEWEB)

    Bertrand, J.M. [Laboratoire de Geodynamique des Chaines Alpines, LGCA, Campus Scientifique, 73 - Le Bourget-du-Lac (France)

    2000-04-01

    The U-Pb age of a meta-granophyre from the Val de Rhemes (Brianconnais basement of the Aosta valley) of 511{+-}9 Ma suggests that the micaschists which dominate the pre-alpine basement of the Grand-Saint-Bernard Nappe are, in part, of Early Paleozoic age. The Brianconnais domain is characterized by a Cambrian to Ordovician alkalineto sub-alkaline (monzonitic) magmatism, similar in age to orthogneisses known in other parts of the Variscan belt and generally interpreted as related to an extensional event. (authors)

  8. Late Paleozoic onset of subduction and exhumation at the western margin of Gondwana (Chilenia Terrane): Counterclockwise P-T paths and timing of metamorphism of deep-seated garnet-mica schist and amphibolite of Punta Sirena, Coastal Accretionary Complex, central Chile (34° S)

    Science.gov (United States)

    Hyppolito, T.; García-Casco, A.; Juliani, C.; Meira, V. T.; Hall, C.

    2014-10-01

    In this study, the Paleozoic albite-epidote-amphibolite occurring as meter-sized intercalations within garnet-mica schist at Punta Sirena beach (Pichilemu region, central Chile) is characterized for the first time. These rocks constitute an unusual exposure of subduction-related rocks within the Paleozoic Coastal Accretionary Complex of central Chile. Whereas high pressure (HP) greenschist and cofacial metasediments are the predominant rocks forming the regional metamorphic basement, the garnet-mica schist and amphibolite yield higher P-T conditions (albite-epidote amphibolite facies) and an older metamorphic age. Combining detailed mineral chemistry and textural information, P-T calculations and Ar-Ar ages, including previously published material from the Paleozoic Accretionary Complex of central Chile, we show that the garnet-mica schist and associated amphibolite (locally retrograded to greenschist) are vestiges of the earliest subducted material now forming exotic bodies within the younger HP units of the paleo-accretionary wedge. These rocks are interpreted as having been formed during the onset of subduction at the southwestern margin of Gondwana. However, we show that the garnet-mica schist formed at a slightly greater depth (ca. 40 km) than the amphibolite (ca. 30 km) along the same hot-subduction gradient developed during the onset of subduction. Both lithotypes reached their peak-P conditions at ca. 335-330 Ma and underwent near-isobaric cooling followed by cooling and decompression (i.e., counterclockwise P-T paths). The forced return flow of the garnet-mica schist from the subduction channel started at ca. 320 Ma and triggered the exhumation of fragments of shallower accreted oceanic crust (amphibolite). Cores of phengite (garnet-mica schist) and amphibole (amphibolite) grains have similar chemical compositions in both the S1 and S2 domains, indicating rotation of these grains during the transposition of the burial-related (prograde peak-T) foliation S1

  9. Crustal basement controls granitoid magmatism, and implications for generation of continental crust in subduction zones: A Sr-Nd-Hf-O isotopic study from the Paleozoic Tongbai orogen, central China

    Science.gov (United States)

    Wang, Hao; Wu, Yuan-Bao; Yang, Jin-Hui; Qin, Zheng-Wei; Duan, Rui-Chun; Zhou, Lian; Yang, Sai-Hong

    2017-06-01

    Ascertaining the petrogenesis of granitoid rocks in subduction zones holds the key for understanding the processes of how continental crust is produced. The synchronous Taoyuan and Huanggang plutons occur in two different geological units of the Paleozoic Tongbai orogen of central China. They provide an optimal opportunity for a study to address the role of the crustal basement in generating voluminous granitoid magmatism in subduction zones. The Taoyuan and Huanggang plutons have identical U-Pb zircon crystallization ages of 440-444 Ma, which are temporally related to northward subduction of the Paleotethyan Ocean. The Taoyuan samples show high SiO2 (73.36-79.16%) and low Al2O3 (12.00-13.45%) contents, Mg numbers (20.6-38.2), and Sr/Y (2.04-10.1) and (La/Yb)N (2.34-7.32) ratios with negative Eu anomalies (Eu/Eu* = 0.33-0.93). They yielded positive εNd(t) (+ 3.0 to + 6.7) and εHf(t) (+ 11.8 to + 13.2) values, elevated initial Sr isotopic ratios (0.7040-0.7057) and relatively low zircon δ18O values of 4.62-5.39‰. These suggest that they were produced through partial melting of hydrothermally altered lower crust of the accreted Erlangping oceanic arc. In contrast, the Huanggang samples exhibit variable whole-rock geochemical and isotopic compositions with SiO2 contents of 57.01-64.42 wt.%, initial Sr isotopic ratios of 0.7065-0.7078, and εNd(t) values of - 5.7 to - 9.4. Additionally, they have high zircon δ18O values of 7.57-8.45‰ and strongly negative zircon εHf(t) values of - 14.4 to - 10.5. They were suggested to have been mainly derived from ancient continental crust of the Kuanping crustal unit with the addition of 20-40% juvenile, mantle-derived material. Accordingly, the granitoids in both oceanic and continental arcs are likely to be mainly derived from intracrustal melting of their crustal basement. It is revealed by the Huanggang pluton that little net continental crust growth occurs in continental arcs, and addition of new volume of continental

  10. Late Paleozoic to Triassic magmatism in the north-central High Andes, Chile: New insights from SHRIMP U-Pb geochronology and O-Hf isotopic signatures in zircon

    Science.gov (United States)

    Hernández González, Álvaro; Deckart, Katja; Fanning, Mark; Arriagada, César

    2014-05-01

    The Chilean High Andes (28o- 31oS) comprises a vast number of late Paleozoic - Triassic granitoids which give information about the last stages of Gondwana assemblage. Particularly, previous studies determined two tectonic configurations during this time: subduction related compressional setting (late Carboniferous - Late Permian) and non-subduction post-collisional extensional setting (Late Permian - Triassic), as the last stage of Gondwana assemblage. However, new O-Hf isotopic data along new U-Pb SHRIMP ages in zircon have shown that this model should be modified and updated to the new analytical data available. δ18O values indicate a strong change in the tectonic configuration approximately 270 Ma (earliest middle Permian) and thus, units can be divided into 2 mayor groups: late Carboniferous to earliest middle Permian and middle Permian to Triassic. The oldest group shows slightly low values of ɛHfi (ca. +1 to -4) with high δ18O (ca. >6.5 o/oo), indicating an elevated supracrustal component and the addition of less radiogenic continental-like material, which along significant residence time (TDM2: Mesoproterozoic) can be interpreted as magmas formed at depth in a subduction-related continental arc, and contaminated with supracrustal material and/or oceanic sediments transported through the subducted slab to the mantle-wedge. Subsequently, middle Permian - Triassic rocks show a wider range of ɛHfi values (ca. +3 to -3) with relatively low, mantle-like δ18O (ca. 4.5-6.5 o/oo), indicating a source of magmas without the addition of supracrustal material for some plutons, whilst for others, a slight input. The higher positive values of ɛHfi can be related to the influence of new juvenile material in the source of some magmas. This isotopic data can be interpreted as rocks formed as the result of melting of an old thinned mafic crust (with mantle-like δ18O values characteristic of this type of rocks) with limited addition of supracrustal material; in

  11. Environmental control on concretion-forming processes: Examples from Paleozoic terrigenous sediments of the North Gondwana margin, Armorican Massif (Middle Ordovician and Middle Devonian) and SW Sardinia (Late Ordovician)

    Science.gov (United States)

    Dabard, Marie-Pierre; Loi, Alfredo

    2012-08-01

    Concretions of various compositions are common in the Paleozoic terrigenous successions of the north Gondwana margin. This study focuses on phosphatic (P) and siliceous (Si) concretions present in some successions of the Armorican Massif (NW France) and SW Sardinia (W Italy). It shows that they consist of mudstones, fine- to very fine-grained sandstones or shellbeds with a more or less abundant P-cement and form a continuum between a phosphatic end-member and a siliceous biogenic end-member. The P2O5 contents are ranging from 0.26% to 21.5% and are related to apatite. The SiO2 contents vary from 25% to 82% and are linked both to a terrigenous phase and to a biogenic silica phase. Concretions showing the lower P-contents (P2O5 5). Comparison with the surrounding sediments shows that all the concretions are enriched in chlorite and in Middle Rare Earth Elements (Las/Gds: 0.12-0.72) and some of them in Y (up to 974 ppm), Rare Earth Elements (more than 300 ppm) and Sr (260-880 ppm). The concretions with highest biogenic silica concentrations are contained in the outer shelf sediments whereas the other concretions are present from the proximal part of the inner shelf to the outer shelf. A genetic model in two stages is proposed. During early diagenesis, the dissolution of shells and degradation of organic matter progressively enrich the pore water in dissolved Si, Ca and P. When the suboxic zone is reached, P-precipitation begins, leading to the formation of protoconcretions. In shallow environments, the relative permeability of sediments and the winnowing or reworking of the upper few centimetres by bottom currents allow for suboxic conditions to be maintained, leading to P-rich concretion formation. In deeper environments, the anoxic zone is reached more rapidly, thereby preventing extensive phosphogenesis. Nevertheless in the protoconcretions the early P-cement preserves pore spaces from compaction. In the presence of biogenic siliceous particles, the fluids are

  12. The Paleozoic record of Thaumatoporella PIA, 1927?

    Czech Academy of Sciences Publication Activity Database

    Schlagintweit, F.; Hladil, Jindřich; Nose, M.; Salerno, C.

    2013-01-01

    Roč. 66, č. 3 (2013), s. 155-182 ISSN 1330-030X Institutional support: RVO:67985831 Keywords : Parathuramminida * calcareous algae * incertae sedis * Thaumatoporella * Bisphaera * Cribrosphaeroides Subject RIV: DB - Geology ; Mineralogy Impact factor: 0.500, year: 2013

  13. Uranium-rich opal from the Nopal I uranium deposit, Peña Blanca, Mexico: Evidence for the uptake and retardation of radionuclides

    Science.gov (United States)

    Schindler, Michael; Fayek, Mostafa; Hawthorne, Frank C.

    2010-01-01

    The Nopal I uranium deposit of the Sierra Peña Blanca, Mexico, has been the focus of numerous studies because of its economic importance and its use as a natural analog for nuclear-waste disposal in volcanic tuff. Secondary uranyl minerals such as uranophane, Ca[(UO 2)(SiO 3OH)] 2(H 2O) 5, and weeksite, (K,Na) 2[(UO 2) 2(Si 5O 13)](H 2O) 3, occur in the vadose zone of the deposit and are overgrown by silica glaze. These glazes consist mainly of opal A, which contains small particles of uraninite, UO 2, and weeksite. Close to a fault between brecciated volcanic rocks and welded tuff, a greenish silica glaze coats the altered breccia. Yellow silica glazes from the center of the breccia pipe and from the high-grade pile coat uranyl-silicates, predominantly uranophane and weeksite. All silica glazes are strongly zoned with respect to U and Ca, and the distribution of these elements indicates curved features and spherical particles inside the coatings. The concentrations of U and Ca correlate in the different zones and both elements inversely correlate with the concentration of Si. Zones within the silica glazes contain U and Ca in a 1:1 ratio with maximum concentrations of 0.08 and 0.15 at.% for the greenish and yellow glazes, respectively, suggesting trapping of either Ca 1U 1-aqueous species or -particles in the colloidal silica. X-ray photoelectron spectroscopy (XPS), Fourier-transform infra-red spectroscopy (FTIR), and oxygen-isotope ratios measured by secondary-ion mass spectrometry (SIMS) indicate higher U 6+/U 4+ ratios, higher proportions of Si-OH groups and lower δ 18O values for the greenish silica glaze than for the yellow silica glaze. These differences in composition reflect increasing brecciation, porosity, and permeability from the center of the breccia pipe (yellow silica glaze) toward the fault (green silica glaze), where the seepage of meteoric water and Eh are higher.

  14. Mineral potential tracts for orogenic, Carlin-like, and epithermal gold deposits in the Islamic Republic of Mauritania, (phase V, deliverable 69): Chapter H in Second projet de renforcement institutionnel du secteur minier de la République Islamique de Mauritanie (PRISM-II)

    Science.gov (United States)

    Goldfarb, Richard J.; Marsh, Erin; Anderson, Eric D.; Horton, John D.; Finn, Carol A.; Beaudoin, Georges

    2015-01-01

    The gold resources of Mauritania presently include two important deposits and a series of poorly studied prospects. The Tasiast belt of deposits, which came into production in 2007, is located in the southwestern corner of the Rgueïbat Shield and defines a world-class Paleoproterozoic(?) orogenic gold ore system. The producing Guelb Moghrein deposit occurs along a shear zone in Middle Archean rocks at the bend in the Northern Mauritanides and is most commonly stated to be an iron oxide-copper-gold (IOCG) type of deposit, although it also has some important characteristics of orogenic gold and skarn deposits. Both major deposits are surrounded by numerous prospects that show similar mineralization styles. The Guelb Moghrein deposit, and IOCG deposit types in general are discussed in greater detail in a companion report by Fernette (2015). In addition, many small gold prospects, which are probably orogenic gold occurrences and are suggested to be early Paleozoic in age, occur along the length of Southern Mauritanides. Existing data indicate the gold deposits and prospects in Mauritania have a sulfide assemblage most commonly dominated by pyrrhotite and chalcopyrite, and have ore-related fluids with apparently high salinities.

  15. Epithermal and Thermal Spectrum Indices in Heavy Water Lattices

    Energy Technology Data Exchange (ETDEWEB)

    Sokolowski, E K; Jonsson, A

    1967-05-15

    Spectral indices have been measured by foil activation technique in a number of different D{sub 2}O-moderated lattices in the Swedish zero power reactor R0 and the pressurized exponential assembly TZ. In most cases the fuel was in the form of single rods, distributed uniformly in the lattice. Parameters in these cases were lattice pitch and fuel composition. A 31-rod cluster lattice was also investigated, with the moderator temperature varying up to 210 deg C. On the basis of these measurements, as well as measurements on cluster lattices, reported by other investigators, it has been possible to derive simple correlations for the spectral indices, which seem to be of fairly general validity for D{sub 2}O lattices. The experimental results have also been compared to calculations with the multigroup collision probability program FLEF.

  16. Neutron scattering from α-Ce at epithermal neutron energies

    Indian Academy of Sciences (India)

    phose into delocalised conduction electrons, while maintaining their f character.” “This insight that f electrons could form energy bands and contribute to the. Fermi surface was controversial for many ..... [11] A P Murani, Z A Bowden, A D Taylor, R Osborn and W G Marshall, Phys. Rev. B48, 13981 (1993). [12] Y Kuramoto ...

  17. Epithermal and Thermal Spectrum Indices in Heavy Water Lattices

    International Nuclear Information System (INIS)

    Sokolowski, E.K.; Jonsson, A.

    1967-05-01

    Spectral indices have been measured by foil activation technique in a number of different D 2 O-moderated lattices in the Swedish zero power reactor R0 and the pressurized exponential assembly TZ. In most cases the fuel was in the form of single rods, distributed uniformly in the lattice. Parameters in these cases were lattice pitch and fuel composition. A 31-rod cluster lattice was also investigated, with the moderator temperature varying up to 210 deg C. On the basis of these measurements, as well as measurements on cluster lattices, reported by other investigators, it has been possible to derive simple correlations for the spectral indices, which seem to be of fairly general validity for D 2 O lattices. The experimental results have also been compared to calculations with the multigroup collision probability program FLEF

  18. Thermal and epithermal neutrons in the treatment of neoplasms

    International Nuclear Information System (INIS)

    Sweet, W.H.; Wellum, G.; Tolpin, E.; Messer, J.R.

    1975-01-01

    Progress is reported in the preparation and testing of boron compounds for use as targets in the neutron capture therapy of neoplasms. The synthesis and structural confirmation of the disulfide, B 1 H 11 SSB 12 H 11 -4 is reported as well as a new structural model for its mono-oxidized derivative, B 12 H 11 SOSB 12 H 11 -4 , which showed useful tumor:blood concentration ratios in rats after three I. V. injections. The material, B 12 H 11 (SH) 2 -2 , was isolated and identified from impure Cs 2 B 12 H 11 SH. The former anion was shown to be responsible, in its oxidized form, for the excellent tumor uptake results shown by impure B 12 H 11 SH -2 in the past. As a consequence of this work, a borane polymer was synthesized which has shown extremely encouraging tumor uptake properties. The synthesis of this polymer depended on our production and characterization of the first stable thiyl radical at room temperature, B 12 H 11 -S: -2 . The retesting of certain phosphate boranes is reported. And a reagent, namely acetyl sulfenyl chloride, lSCOCH 3 , has been found which will produce B 12 H 11 SH -2 in a laboratory synthesis. The ability of sulfur derivatives of B 12 H 11 SH -2 to bind to proteins was examined, as was the blood distribution of two of these interesting boranes. The amount of non-protein bound borane was related to the rate of blood clearance of the borane in rats. Progress is also reported on dog irradiation experiments. (U.S.)

  19. Assessment of Appalachian basin oil and gas resources: Devonian gas shales of the Devonian Shale-Middle and Upper Paleozoic Total Petroleum System: Chapter G.9 in Coal and petroleum resources in the Appalachian basin: distribution, geologic framework, and geochemical character

    Science.gov (United States)

    Milici, Robert C.; Swezey, Christopher S.; Ruppert, Leslie F.; Ryder, Robert T.

    2014-01-01

    This report presents the results of a U.S. Geological Survey (USGS) assessment of the technically recoverable undiscovered natural gas resources in Devonian shale in the Appalachian Basin Petroleum Province of the eastern United States. These results are part of the USGS assessment in 2002 of the technically recoverable undiscovered oil and gas resources of the province. This report does not use the results of a 2011 USGS assessment of the Devonian Marcellus Shale because the area considered in the 2011 assessment is much greater than the area of the Marcellus Shale described in this report. The USGS assessment in 2002 was based on the identification of six total petroleum systems, which include strata that range in age from Cambrian to Pennsylvanian. The Devonian gas shales described in this report are within the Devonian Shale-Middle and Upper Paleozoic Total Petroleum System, which extends generally from New York to Tennessee. This total petroleum system is divided into ten assessment units (plays), four of which are classified as conventional and six as continuous. The Devonian shales described in this report make up four of these continuous assessment units. The assessment results are reported as fully risked fractiles (F95, F50, F5, and the mean); the fractiles indicate the probability of recovery of the assessment amount. The products reported are oil, gas, and natural gas liquids. The mean estimates for technically recoverable undiscovered hydrocarbons in the four gas shale assessment units are 12,195.53 billion cubic feet (12.20 trillion cubic feet) of gas and 158.91 million barrels of natural gas liquids

  20. Elasticity and Density of Paleozoic Shales from Bornholm

    DEFF Research Database (Denmark)

    Fabricius, Ida Lykke; Haugwitz, C.; Larsen, Pernille Birkelund

    2017-01-01

    Darcy. We found that solid density and elastic stiffness parameters only vary insignificantly with solid composition, when TOC is lower than 5%, but that mass density and TOC are correlated when TOC is higher than 5%. A similar correlation was not seen for TOC and Sonic logging data. A reason can...

  1. Ore levels in Paleozoic of Semipalatinsk test site

    International Nuclear Information System (INIS)

    Ergaliev, G.Kh.; Myasnikov, A.K.; Fomichev, V.I.

    1999-01-01

    The regularity of the deposition of main mineralization of industrial types within Semipalatinsk test site proves and here and there defines more exactly location of the ore levels in Eastern Kazakhstan. Two mega levels, namely: Cambrian-Ordovician (siliceous-basalt, island-arc) and Carboniferous (especially carbonaceous-tarragons) ones are the most perspective for localizing the leading gold mineralization in the region

  2. Improving global paleogeography since the late Paleozoic using paleobiology

    Directory of Open Access Journals (Sweden)

    W. Cao

    2017-12-01

    Full Text Available Paleogeographic reconstructions are important to understand Earth's tectonic evolution, past eustatic and regional sea level change, paleoclimate and ocean circulation, deep Earth resources and to constrain and interpret the dynamic topography predicted by mantle convection models. Global paleogeographic maps have been compiled and published, but they are generally presented as static maps with varying map projections, different time intervals represented by the maps and different plate motion models that underlie the paleogeographic reconstructions. This makes it difficult to convert the maps into a digital form and link them to alternative digital plate tectonic reconstructions. To address this limitation, we develop a workflow to restore global paleogeographic maps to their present-day coordinates and enable them to be linked to a different tectonic reconstruction. We use marine fossil collections from the Paleobiology Database to identify inconsistencies between their indicative paleoenvironments and published paleogeographic maps, and revise the locations of inferred paleo-coastlines that represent the estimated maximum transgression surfaces by resolving these inconsistencies. As a result, the consistency ratio between the paleogeography and the paleoenvironments indicated by the marine fossil collections is increased from an average of 75 % to nearly full consistency (100 %. The paleogeography in the main regions of North America, South America, Europe and Africa is significantly revised, especially in the Late Carboniferous, Middle Permian, Triassic, Jurassic, Late Cretaceous and most of the Cenozoic. The global flooded continental areas since the Early Devonian calculated from the revised paleogeography in this study are generally consistent with results derived from other paleoenvironment and paleo-lithofacies data and with the strontium isotope record in marine carbonates. We also estimate the terrestrial areal change over time associated with transferring reconstruction, filling gaps and modifying the paleogeographic geometries based on the paleobiology test. This indicates that the variation of the underlying plate reconstruction is the main factor that contributes to the terrestrial areal change, and the effect of revising paleogeographic geometries based on paleobiology is secondary.

  3. Evolution of viviparous reproduction in Paleozoic and Mesozoic reptiles.

    Science.gov (United States)

    Blackburn, Daniel G; Sidor, Christian A

    2014-01-01

    Although viviparity (live-bearing reproduction) is widely distributed among lizards and snakes, it is entirely absent from other extant Reptilia and many extinct forms. However, paleontological evidence reveals that viviparity was present in at least nine nominal groups of pre-Cenozoic reptiles, representing a minimum of six separate evolutionary origins of this reproductive mode. Two viviparous clades (sauropterygians and ichthyopterygians) lasted more than 155 million years, a figure that rivals the duration of mammalian viviparity. Circumstantial evidence indicates that extinct viviparous reptiles had internal fertilization, amniotic fetal membranes, and placentas that sustained developing embryos via provision of respiratory gases, water, calcium, and possibly organic nutrients. Production of offspring via viviparity facilitated the invasion of marine habitats in at least five reptilian lineages. Thus, this pattern of embryonic development and reproduction was central to the ecology and evolution of these ancient animals, much as it is to numerous extant species of vertebrates.

  4. Weathering characteristics of the Lower Paleozoic black shale in ...

    Indian Academy of Sciences (India)

    permeability show that porosity increases significantly after weathering but permeability changes little. Furthermore, the ... As such, black shales usually have a high content of ... in the accumulation of soluble weathering phases, providing ...

  5. Lost Terranes of Zealandia: possible development of late Paleozoic and early Mesozoic sedimentary basins at the southwest Pacific margin of Gondwanaland, and their destination as terranes in southern South America Terrenos perdidos de Zealandia: posible desarrollo de cuencas sedimentarias del Paleozoico tardío y Mesozoico temprano en el margen suroccidental del Pacífico de Gondwana y su destino como terrenos en el sur de América del Sur

    Directory of Open Access Journals (Sweden)

    Christopher J Adams

    2010-07-01

    Full Text Available Latest Precambrian to Ordovician metasedimentary successions and Cambrian-Ordovician and Devonian-Carboniferous granitoids form the major part of the basement of southern Zealandia and adjacent sectors of Antarctica and southeast Australia. Uplift/cooling ages of these rocks, and local Devonian shallow-water cover sequences suggest that final consolidation of the basement occurred through Late Paleozoic time. A necessary consequence of this process would have been contemporaneous erosion and the substantial development of marine sedimentary basins at the Pacific margin of Zealandia. These are found nowhere at the present day, suggesting that the basins have been lost by tectonic erosion, perhaps in a margin-parallel dextral translation similar to late Paleozoic-Mesozoic suspect terranes of New Zealand. Aprobable detrital zircon age pattern is assembled for these lost Zealandia sediments, and then compared with those of pre-Jurassic (probable Triassic to Devonian metasedimentary rocks in the Chilean archipelago. Significant Mesoproterozoic, latest Neoproterozoic-Cambrian and Devonian-Carboniferous detrital zircon age components are common to both, thus supporting a possible Chilean terrane destination for these 'lost terranes of Zealandia'.Las sucesiones metasedimentarias del Precámbrico tardío al Ordovícico y granitoides del Cámbrico-Ordovícico y Devónico-Carbonífero constituyen la mayor parte del basamento del sur de Zealandia y sectores adyacentes de la Antartica y el sudeste de Australia. Las edades de enfriamiento/alzamiento de estas rocas y la cobertura local de secuencias de aguas someras del Devónico, sugieren que la consolidación definitiva del basamento se produjo durante el Paleozoico tardío. Una consecuencia necesaria de este proceso habría sido la erosion contemporánea y el desarrollo sustancial de cuencas sedimentarias marinas en el margen del Pacífico de Zealandia. Estas no se encuentran en ninguna parte en la

  6. Structural overprint of a late Paleozoic accretionary system in north-central Chile (34°-35°S during post-accretional deformation Modificación estructural de un sistema acrecional del Paleozoico tardío en el centro-norte de Chile (34°-35°S, durante deformación posacrecional

    Directory of Open Access Journals (Sweden)

    Arne P Willner

    2009-01-01

    Full Text Available In the Coastal Cordillera of central Chile a coherently preserved architecture of a late Paleozoic accretionary prism is exposed at 36°-35°S in cióse spatial association with a neighbouring área at 34°-35°S, where it is strongly modified by post-accretional processes. Syn- and post-accretional struetures can be distinguished relatively easily in this región studying the deviations from the original architecture. South of 35°S a transitional contact between two major units is observed, which reflects a continuous change of the mode of accretion in the accretionary wedge before -305 Ma: the structurally overlying metagreywacke of the Eastern Series exhibits struetures typical of frontal accretion, Le., subvertical chevron folds of bedding planes with an axial-plane foliation Sr With increasing finite strain structurally downwards, open F2 folds develop associated with a S2-foliation which becomes gradually flattened as it rotates into a subhorizontal orientation. S2 is the penetrative transposition foliation in the structurally underlying Western Series. It affeets the continent-derived metagreywacke series as well as metabasite intercalations of oceanic origin and was formed during basal accretion. This principal evolution of the accretionary system places firm constraints on the original architecture also in regions where it was destructed after accretion. Accretion ceased at -225 Ma, when a major tectonic change from a convergent to an extensional/strike-slip regime oceurred. Although the development of the margin in central Chile is largely characterized by extensión during Mesozoic and Cenozoic times, two pronounced episodes involving shortening of the forearc particularly affected the Western Series north of 35°S: 1. Expressions of strike-slip activity during Jurassic times involve local steepening of the originally flat S2-foliation planes, local rotation of the stretching lineation L2 into the N-S direction, tight upright folding

  7. La Formación Los Llantenes en la Precordillera de Jagüé (La Rioja y la identificación de un episodio de extensión en la evolución temprana de las cuencas del Paleozoico superior en el oeste argentino The Los Llantenes Formation in the Precordillera of Jagüé (La Rioja Province and the recognition of a rifting stage in the early evolution of the late Paleozoic basins in western Argentina

    Directory of Open Access Journals (Sweden)

    Ricardo A Astini

    2011-07-01

    Formación Los Llantenes, sumado a la procedencia local, permiten interpretar el desarrollo de depocentros asociados con un marco tectónico extensional o transtensivo, conclusiones importantes para reconstruir la historia de la cuenca.In the northern part of the Argentine Precordillera, northwestern La Rioja, the Upper Paleozoic is over 4,000 m thick. Very coarse conglomerates from the basal section have not been described nor adequately interpreted. This work analyses this unit in the context of a stratigraphic revision of the upper Paleozoic of the region, and interprets the conglomerate as a rift deposit. The thick (>1,000 m and coarse purple conglomeratic succession, herein named 'Los Llantenes Formation', non-conformably rests on the basement rocks of the region and underlies deposits of the first glacial record associated with the Gondwanan glaciation. While its great thickness and restricted areal extent indicate localized subsidence, the crude stratification, poor sorting and abundance of >1-m boulders indicate an origin related to high-gradient, low-efficiency alluvial fans. Their composition and coarse-grained size indicate local provenance, abrupt relief and incipiently developed drainage systems and a highly compartmentalized and abrupt paleogeography. A complex glacial history generated deep 'U'-shaped paleovalleys in the Los Llantenes Formation, developing paleovalleys that accommodated basal lodgment tills and glacial diamictites with sedimentologic features comparable to the Cerro Tres Cóndores Formation (Visean in age exposed to the south. The age of the conglomerales of Los Llantenes Formation, clearly preglacial, can be stratigraphically bracketed between the Middle Devonian substrate cropping out to the south in the sierra de Las Minitas and the Middle Mississippian, age of the Cerro Tres Condores Formation. Consequently, Los Llantenes Formation may partly correlate with the Agua de Lucho Formation (Tournaisian-Vissean that in the area of Río del Pe

  8. Epithermal neutron activation analysis of major and trace elements in Red Sea scleractinian corals

    International Nuclear Information System (INIS)

    Abdo, S.Y.; Sherif, M.M.; Frontasyeva, M.V.

    2017-01-01

    Five corals belonging to common scleractinian reef-building species, and collected from Gulf of Suez, Egypt were subjected to neutron activation analysis. The content of 26 elements: Na, Mg, Cl, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Zn, As, Br, Rb, Sr, Sb, I, Cs, Ba, La, Ce, Gd, Hf, Th, and U was experimentally determined. Ca and Sr have the highest content i.e. 38.4-39.5% and 0.73-0.78% respectively while, the content of all other elements was within the ranges reported for the worldwide corals. For a better understanding of the coral exoskeleton elemental content, the partition coefficient calculated for all determined elements showed a wide range of values varying from 2 × 10 -4 in the case of Cl to 2 × 10 3 for Ce and other insoluble elements. Although all corals were collected in the vicinity of the Port Suez no traces of anthropogenic contamination were evidenced. (author)

  9. Determination of several trace elements in Chinese herbs with epithermal neutral activation analysis

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Chien-Yi [Chung Shan Medical Univ., Inst. of Biochemistry, Taiwan (China); Chang Lai, Sheng-Pin [Chung Shan Medical Univ. Hospital, Dept. of Nuclear Medicine Chief, Taiwan (China)

    2002-04-01

    For purpose of medication and health, Chinese herbs have been long adopted throughout oriental communities. Thus, more than ten trace elements in herbal medicines that are frequently consumed by children in central Taiwan were analyzed herein to explore the importance of various herbs. These elements are considered beneficial to human health in many folds. INAA was applied to determine the concentrations of elements as Al, Cl and Sc, while ENAA analyzed As, Cd, Mn, and Sb in this work. Among various local herbs, the elemental concentrations varied from 10{sup 4} to 10{sup -3} {mu}g/g. The experimental results suggest that the ENAA method can be applied successfully to analyze trace elements of As, Cd, Mn, and Sb in herbs. Yet, thirteen elements were verified, and a quantified index AT was introduced to help classifying the elements. The ATs in various Chinese herbs are also discussed herein and the accuracy is in excellent agreement with values reported in previously published data. (author)

  10. Accelerator-based epithermal neutron sources for boron neutron capture therapy of brain tumors.

    Science.gov (United States)

    Blue, Thomas E; Yanch, Jacquelyn C

    2003-01-01

    This paper reviews the development of low-energy light ion accelerator-based neutron sources (ABNSs) for the treatment of brain tumors through an intact scalp and skull using boron neutron capture therapy (BNCT). A major advantage of an ABNS for BNCT over reactor-based neutron sources is the potential for siting within a hospital. Consequently, light-ion accelerators that are injectors to larger machines in high-energy physics facilities are not considered. An ABNS for BNCT is composed of: (1) the accelerator hardware for producing a high current charged particle beam, (2) an appropriate neutron-producing target and target heat removal system (HRS), and (3) a moderator/reflector assembly to render the flux energy spectrum of neutrons produced in the target suitable for patient irradiation. As a consequence of the efforts of researchers throughout the world, progress has been made on the design, manufacture, and testing of these three major components. Although an ABNS facility has not yet been built that has optimally assembled these three components, the feasibility of clinically useful ABNSs has been clearly established. Both electrostatic and radio frequency linear accelerators of reasonable cost (approximately 1.5 M dollars) appear to be capable of producing charged particle beams, with combinations of accelerated particle energy (a few MeV) and beam currents (approximately 10 mA) that are suitable for a hospital-based ABNS for BNCT. The specific accelerator performance requirements depend upon the charged particle reaction by which neutrons are produced in the target and the clinical requirements for neutron field quality and intensity. The accelerator performance requirements are more demanding for beryllium than for lithium as a target. However, beryllium targets are more easily cooled. The accelerator performance requirements are also more demanding for greater neutron field quality and intensity. Target HRSs that are based on submerged-jet impingement and the use of microchannels have emerged as viable target cooling options. Neutron fields for reactor-based neutron sources provide an obvious basis of comparison for ABNS field quality. This paper compares Monte Carlo calculations of neutron field quality for an ABNS and an idealized standard reactor neutron field (ISRNF). The comparison shows that with lithium as a target, an ABNS can create a neutron field with a field quality that is significantly better (by a factor of approximately 1.2, as judged by the relative biological effectiveness (RBE)-dose that can be delivered to a tumor at a depth of 6cm) than that for the ISRNF. Also, for a beam current of 10 mA, the treatment time is calculated to be reasonable (approximately 30 min) for the boron concentrations that have been assumed.

  11. Improvements on the calculation of the epithermal disadvantage factor for thermal nuclear reactors

    Energy Technology Data Exchange (ETDEWEB)

    Aboustta, Mohamed A.; Martinez, Aquilino S. [Universidade Federal, Rio de Janeiro, RJ (Brazil). Coordenacao dos Programas de Pos-graduacao de Engenharia

    1997-12-01

    The disadvantage factor takes into account the neutron flux variation through the fuel cell. In the fuel the flux is depressed in relation to its level in the moderator region. In order to avoid detailed calculations for each different set of cell dimensions, which turns out necessary the development of problem-dependent neutron cross section libraries, a disadvantage factor based on a two-region equivalence theory was proposed for the EPRI-CELL code. However, it uses a rational approximation to the neutron escape probability to describe the neutron transport between cell regions. Such approximation allows the use of the equivalence principals but introduces a non negligible error which results in an underestimation of the cell neutron fluxes. A new proposed treatment, that will be presented in this work, remarkably improves the numerical calculation and reduces the error of the above mentioned method. (author). 4 refs., 2 figs.

  12. Density and energy distribution of epithermal secondary electrons in a plasma with fast charged particles

    International Nuclear Information System (INIS)

    Jayakumar, R.; Fleischmann, H.H.

    1989-01-01

    The production of intermediate energy secondary electrons in plasmas through collisions with fast charged particles is investigated. The density and the distribution of the secondary electrons are obtained by calculating the generation, slow down and diffusion rates, using basic Rutherford collision cross sections. It is shown that the total density of secondaries is much smaller than the fast particle density and that the energy distribution has roughly a 1/√E dependence. The higher generation secondary populations are also obtained. (orig.)

  13. Improvements on the calculation of the epithermal disadvantage factor for thermal nuclear reactors

    International Nuclear Information System (INIS)

    Aboustta, Mohamed A.; Martinez, Aquilino S.

    1997-01-01

    The disadvantage factor takes into account the neutron flux variation through the fuel cell. In the fuel the flux is depressed in relation to its level in the moderator region. In order to avoid detailed calculations for each different set of cell dimensions, which turns out necessary the development of problem-dependent neutron cross section libraries, a disadvantage factor based on a two-region equivalence theory was proposed for the EPRI-CELL code. However, it uses a rational approximation to the neutron escape probability to describe the neutron transport between cell regions. Such approximation allows the use of the equivalence principals but introduces a non negligible error which results in an underestimation of the cell neutron fluxes. A new proposed treatment, that will be presented in this work, remarkably improves the numerical calculation and reduces the error of the above mentioned method. (author). 4 refs., 2 figs

  14. Determination of iodine in Asian diets by epithermal and radiochemical neutron activation analysis

    Czech Academy of Sciences Publication Activity Database

    Kučera, Jan; Iyengar, GV.; Řanda, Zdeněk; Parr, RM.

    2004-01-01

    Roč. 259, č. 3 (2004), s. 505-509 ISSN 0236-5731 R&D Projects: GA AV ČR IAA4048301 Institutional research plan: CEZ:AV0Z1048901 Keywords : iodine * Asian diets Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 0.457, year: 2004

  15. Physical parameters and biological effects of the LVR-15 epithermal neutron beam

    Czech Academy of Sciences Publication Activity Database

    Burian, J.; Gambarini, G.; Marek, M.; Mareš, Vladislav; Rejchrt, J.; Vanossi, E.; Viererbl, L.; Judas, L.

    -, - (2006), s. 481-484 [International Congress on Neutron Capture Therapy /12./. Kagawo, 09.10.2006-13.10.2006] R&D Projects: GA MPO(CZ) 1H-PK2/05 Institutional research plan: CEZ:AV0Z50110509 Keywords : brain tumors * neutron capture therapy * NTC * dosimetry Subject RIV: FD - Oncology ; Hematology

  16. Filtered epithermal quasi-monoenergetic neutron beams at research reactor facilities.

    Science.gov (United States)

    Mansy, M S; Bashter, I I; El-Mesiry, M S; Habib, N; Adib, M

    2015-03-01

    Filtered neutron techniques were applied to produce quasi-monoenergetic neutron beams in the energy range of 1.5-133keV at research reactors. A simulation study was performed to characterize the filter components and transmitted beam lines. The filtered beams were characterized in terms of the optimal thickness of the main and additive components. The filtered neutron beams had high purity and intensity, with low contamination from the accompanying thermal emission, fast neutrons and γ-rays. A computer code named "QMNB" was developed in the "MATLAB" programming language to perform the required calculations. Copyright © 2014 Elsevier Ltd. All rights reserved.

  17. Simulation study of accelerator based quasi-mono-energetic epithermal neutron beams for BNCT.

    Science.gov (United States)

    Adib, M; Habib, N; Bashter, I I; El-Mesiry, M S; Mansy, M S

    2016-01-01

    Filtered neutron techniques were applied to produce quasi-mono-energetic neutron beams in the energy range of 1.5-7.5 keV at the accelerator port using the generated neutron spectrum from a Li (p, n) Be reaction. A simulation study was performed to characterize the filter components and transmitted beam lines. The feature of the filtered beams is detailed in terms of optimal thickness of the primary and additive components. A computer code named "QMNB-AS" was developed to carry out the required calculations. The filtered neutron beams had high purity and intensity with low contamination from the accompanying thermal, fast neutrons and γ-rays. Copyright © 2015 Elsevier Ltd. All rights reserved.

  18. Determination of several trace elements in Chinese herbs with epithermal neutral activation analysis

    International Nuclear Information System (INIS)

    Chen, Chien-Yi; Chang Lai, Sheng-Pin

    2002-01-01

    For purpose of medication and health, Chinese herbs have been long adopted throughout oriental communities. Thus, more than ten trace elements in herbal medicines that are frequently consumed by children in central Taiwan were analyzed herein to explore the importance of various herbs. These elements are considered beneficial to human health in many folds. INAA was applied to determine the concentrations of elements as Al, Cl and Sc, while ENAA analyzed As, Cd, Mn, and Sb in this work. Among various local herbs, the elemental concentrations varied from 10 4 to 10 -3 μg/g. The experimental results suggest that the ENAA method can be applied successfully to analyze trace elements of As, Cd, Mn, and Sb in herbs. Yet, thirteen elements were verified, and a quantified index AT was introduced to help classifying the elements. The ATs in various Chinese herbs are also discussed herein and the accuracy is in excellent agreement with values reported in previously published data. (author)

  19. Methods of Reducing Bias in Combined Thermal/Epithermal Neutron (CTEN) Assays of Heterogeneous Waste

    Energy Technology Data Exchange (ETDEWEB)

    Estep, R.J.; Melton, S.; Miko, D.

    1998-11-17

    We examined the effectiveness of two different methods for correcting CTEN passive and active assays for bias due to variations in the source position in different drum types. Both use the same drum-averaged correction determined from a neural network trained to active flux monitor ratios as a starting point. One method then uses a neural network to obtain a spatial correction factor sensitive to the source location. The other method uses emission tomography. Both methods were found to give significantly improved assay accuracy over the drum-averaged correction, although more study is needed to determine which method works better.

  20. Methods of Reducing Bias in Combined Thermal/Epithermal Neutron (CTEN) Assays of Heterogeneous Waste

    International Nuclear Information System (INIS)

    Estep, R.J.; Melton, S.; Miko, D.

    1998-01-01

    We examined the effectiveness of two different methods for correcting CTEN passive and active assays for bias due to variations in the source position in different drum types. Both use the same drum-averaged correction determined from a neural network trained to active flux monitor ratios as a starting point. One method then uses a neural network to obtain a spatial correction factor sensitive to the source location. The other method uses emission tomography. Both methods were found to give significantly improved assay accuracy over the drum-averaged correction, although more study is needed to determine which method works better

  1. Cadmium-Zinc-Telluride photon detector for epithermal neutron spectroscopy--pulse height response characterisation

    International Nuclear Information System (INIS)

    Tardocchi, M.; Pietropaolo, A.; Andreani, C.; Bracco, A.; D'Angelo, A.; Gorini, G.; Imberti, S.; Senesi, R.; Rhodes, N.J.; Schooneveld, E.M.

    2004-01-01

    The Resonance Detector Spectrometer was recently revised for neutron spectroscopic studies in the eV energy region. In this technique one makes use of a photon detector to record the gamma emission from analyser foils used as neutron-gamma converters. The pulse-height response of a Cadmium-Zinc-Telluride photon detector to neutron capture emission from 238 U and 197 Au analyser foils was characterised in the neutron energy range 1-200 eV. The experiment was performed on the VESUVIO spectrometer at the ISIS neutron-pulsed source. A biparametric data acquisition, specifically developed for these measurements, allowed the simultaneous measurements of both the neutron time of flight and γ pulse-height spectra. Through the analysis of the γ pulse-height spectra the main components of the signal associated with resonant and non-resonant neutron absorption were identified. It was also shown that, in principle, energy discrimination can be used to improve the signal to background ratio of the neutron time-of-flight measurement

  2. The background cross section method for calculating the epithermal neutron spectra

    International Nuclear Information System (INIS)

    Martinez, A.S.

    1983-01-01

    We have developed a new methodology to the multigroup constants calculations, for thermal and fast reactors. The method to obtain the constants is extremely fast and simple, and it avoid repeated computations of the detailed neutron spectrum for different cell configurations (composition, geometry and temperature). (author) [pt

  3. Design of an irradiation facility with thermal, epithermal and fast neutron beams

    International Nuclear Information System (INIS)

    Pfister, G.; Bernnat, W.; Seidel, R.; Schatz, A.K.; Wagner, F.M.; Waschkowski, W.; Schraube, H.

    1992-01-01

    The main features of a neutron irradiation facility to be installed at the planned research reactor FRM-II are presented. In addition to the operational possibilities of the existing facility at the reactor FRM-I, the new facility will produce quasi-monoenergetic neutron fields and a neutron beam in the keV region whose spectrum can be modified by application of suitable filters and scatterers. For this beam, which is well suited for boron capture therapy, calculated boron reaction rates inside a phantom and an experimental verification of the calculations at the existing facility are presented. (orig.) [de

  4. Single-crystal filters for attenuating epithermal neutrons and gamma rays in reactor beams

    DEFF Research Database (Denmark)

    Rustad, B.M.; Als-Nielsen, Jens Aage; Bahnsen, A.

    1965-01-01

    Cross section of representative samples of bismuth and quartz were measured at room and liquid nitrogen temperatures over neutron energy range of 0.0007 to 2.0 ev to obtain data for design of single-crystal 32-cm bismuth filters for attenuating fast neutrons and γ-rays in reactor beams; filters may...

  5. Epithermal neutron activation analysis investigation of Clarion-Clipperton abyssal plane clay and polymetallic micronodules.

    Science.gov (United States)

    Duliu, O G; Cristache, C I; Culicovc, O A; Frontasyeva, M V; Szobotca, S A; Toma, M

    2009-05-01

    The content of seven major (Na, Al, Cl, Mn, K, Ca, Ti, Fe) and 30 trace (Sc, V, Cr, Ni, Co, Zn, Cu, As, Sr, Rb, Zr, Mo, Sn, In, Sb, Ba, Cs, La, Ce, Nd, Eu, Sm, Tb, Dy, Yb, Hf, Ta, W, Th, U) elements determined by INAA in 13 samples of abyssal clay and two samples of micronodules collected from the North pacific Ocean Clarion-Clipperton abyssal plane is presented and discussed with respect to some rocks models.

  6. Epithermal neutron activation analysis investigation of Clarion-Clipperton abyssal plane clay and polymetallic micronodules

    International Nuclear Information System (INIS)

    Duliu, O.G.; Cristache, C.I.; Culicovc, O.A.; Frontasyeva, M.V.; Szobotca, S.A.; Toma, M.

    2009-01-01

    The content of seven major (Na, Al, Cl, Mn, K, Ca, Ti, Fe) and 30 trace (Sc, V, Cr, Ni, Co, Zn, Cu, As, Sr, Rb, Zr, Mo, Sn, In, Sb, Ba, Cs, La, Ce, Nd, Eu, Sm, Tb, Dy, Yb, Hf, Ta, W, Th, U) elements determined by INAA in 13 samples of abyssal clay and two samples of micronodules collected from the North pacific Ocean Clarion-Clipperton abyssal plane is presented and discussed with respect to some rocks models.

  7. Epithermal neutron activation analysis investigation of Clarion-Clipperton abyssal plane clay and polymetallic micronodules

    Energy Technology Data Exchange (ETDEWEB)

    Duliu, O.G. [University of Bucharest, Department of Atomic and Nuclear Physics, P.O. Box MG-11, 077125 Magurele, Ilfov (Romania)], E-mail: duliu@b.astral.ro; Cristache, C.I. [National Institute of Research and Development for Physics and Nuclear Engineering ' Horia-Hulubei' , P.O. Box MG-6, 077125 Magurele, Ilfov (Romania)], E-mail: ocarmen@ifin.nipne.ro; Culicovc, O.A. [Joint Institute of Nuclear Research, 6, Joliot Curie str., 141980 Dubna (Russian Federation)], E-mail: otilia_culicov@yahoo.com; Frontasyeva, M.V. [Joint Institute of Nuclear Research, 6, Joliot Curie str., 141980 Dubna (Russian Federation)], E-mail: marina@nf.jinr.ru; Szobotca, S.A. [National Institute of Geoecology and Marine Geology, 34 Dimitrie Onciul str., 024504 Bucharest (Romania)], E-mail: szobi@geoecomar.ro; Toma, M. [National Institute of Research and Development for Physics and Nuclear Engineering ' Horia-Hulubei' , P.O. Box MG-6, 077125 Magurele, Ilfov (Romania)

    2009-05-15

    The content of seven major (Na, Al, Cl, Mn, K, Ca, Ti, Fe) and 30 trace (Sc, V, Cr, Ni, Co, Zn, Cu, As, Sr, Rb, Zr, Mo, Sn, In, Sb, Ba, Cs, La, Ce, Nd, Eu, Sm, Tb, Dy, Yb, Hf, Ta, W, Th, U) elements determined by INAA in 13 samples of abyssal clay and two samples of micronodules collected from the North pacific Ocean Clarion-Clipperton abyssal plane is presented and discussed with respect to some rocks models.

  8. Are modern geothermal waters in northwest Nevada forming epithermal gold deposits?

    Science.gov (United States)

    Breit, George N.; Hunt, Andrew G.; Wolf, Ruth E.; Koenig, Alan E.; Fifarek, Richard; Coolbaugh, Mark F.

    2010-01-01

    Hydrothermal systems currently are active near some gold deposits in northwestern Nevada. Possible links of these modern systems to gold mineralization were evaluated by chemically and isotopically analyzing water samples from the Brady, Dixie Valley, Humboldt House, San Emidio-Empire, Soda Lake, and Wabuska geothermal areas. In addition, quartz veins from Humboldt House and the adjacent Florida Canyon Mine were analyzed to compare ore and gangue phases with those predicted to form from proximal hydrothermal fluids.Nearly all water samples are alkali-chloride-type. Total dissolved solids range from 800 to 3900 mg/L, and pH varies from 5.6 to 7.8. Geochemical modeling with SOLVEQ, WATCH, and CHILLER predict the precipitation of silica in all systems during cooling. Anhydrite, calcite, barite, pyrite, base-metal sulfides, and alumino-silicates are variably saturated at calculated reservoir temperatures and also precipitate during boiling/cooling of some fluids. Measured dissolved gold concentrations are low (<0.2μg/L), but are generally consistent with contents predicted by equilibrium of sampled solutions with elemental gold at reservoir temperatures.  Although the modern geothermal waters can precipitate ore minerals, the low gold and other ore metal concentrations require very large fluid volumes to form a deposit of economic interest.

  9. The Paleozoic Dust Bowl: Dust Deposition in Tropical Western Pangaea (Midcontinent U.S.) at the Terminus of the Late Paleozoic Ice Age

    Science.gov (United States)

    Soreghan, G. S.; Heavens, N. G.; Benison, K. C.; Soreghan, M. J.; Mahowald, N. M.; Foster, T.; Zambito, J.; Sweet, A.; Kane, M.

    2012-12-01

    Atmospheric dust is well recognized and studied as both an archive and agent of climate change in Earth's relatively recent past. Archives of past dust include loess deposits and dust recovered from ocean- and ice-cores. Dust remains poorly known in Earth's past prior to the Cenozoic, but is increasingly recognized in the form of paleo-loess deposits, and (epeiric) marine strata that accumulated isolated from fluvio-deltaic influx. Here, we report on the growing recognition of voluminous dust deposits preserved in the Permian record of the U.S. Midcontinent (western tropical Pangaea). Fine-grained redbeds predominate in Permian strata throughout the U.S. Midcontinent, but notably in a swath extending from Oklahoma through South Dakota. These units consist predominantly of red mudstone and siltstone in commonly massive units, but sedimentary structures and bedding that signal aqueous processes (e.g. laminations, ripples) have led most to infer deltaic or tidal deposition. The absence of channel systems to deliver the sediment, as well as the predominantly massive and laterally continuous character and the uniform fine grain size signal wind transport, implying that these units record sustained dust deposition overprinted at times by sub-aqueous deposition in lakes, including ephemeral saline and acid lakes that led to evaporite cementation. Detrital zircon geochronology indicates that much of the dust originated in the relatively distant Appalachian-Ouachita orogenic systems, which formed part of the central Pangaean mountains (CPM), the collisional zone that sutured the supercontinent. Within the Anadarko basin of Oklahoma, Permian redbeds record >2 km of predominantly dust deposition, some of the thickest dust deposits yet documented in Earth's record. Yet the tropical setting is remarkably non-uniformitarian, as much Quaternary loess occurs in mid- to high-latitude regions, commonly linked to glacial genesis. We are currently investigating with both data and modeling possible causes and consequences of this massive dust record, which may include (1) partial glacial genesis in the CPM, (2) the action of the Pangaean mega-monsoon, and (3) particularly effective dust traps in the Midcontinent region. Modeling constrains the erosivity (the effect of winds and soil moisture effects) of a range of possible climate states on dust mobilization and underscores the relative difficulty of sourcing dust directly from the Appalachian-Ouachita orogenic system under most circumstances. Combining data and modeling helps constrain the erodibility (sediment availability, coherence, etc.) of dust sources. Reconstructions of marine dust deposition to the south and the west of the Anadarko basin suggest glacial-interglacial timescale erodibility changes were similar to those seen in the Midcontinent in the last 20,000 years, when it was at a much higher latitude.

  10. Geochemical Evaluation of black shales from the deposit Nizna Slana, lower paleozoic, Western Carpatians

    International Nuclear Information System (INIS)

    Turanova, L.; Turan, J.; Khun, M.

    1996-01-01

    Black shales from the deposit Nizna Slana and its immediate surroundings can be divided into black shales ss, carbonate black shales and siliceous black shales on the basis of chemical composition. Basic statistical characteristics of main and trace elements, as well as content of organic carbon, are evaluated and compared in this paper, either numerically, or graphically using the box-and whisker diagrams (median, 25 % percentile, 75 % percentile, total extent). (authors)

  11. Burning of forest materials under late Paleozoic high atmospheric oxygen levels

    Science.gov (United States)

    Richard A., Jr. Wildman; Leo J. Hickey; Matthew B. Dickinson; Robert A. Berner; Jennifer M. Robinson; Michael Dietrich; Robert H. Essenhigh; Craig B. Wildman

    2004-01-01

    Theoretical models suggest that atmospheric oxygen reached concentrations as high as 35% O2 during the past 550 m.y. Previous burning experiments using strips of paper have challenged this idea, concluding that ancient wildfires would have decimated plant life if O2 significantly exceeded its present level of 21%. New...

  12. Microbial methane in the shallow Paleozoic sediments and glacial deposits of Illinois, U.S.A.

    Science.gov (United States)

    Coleman, D.D.; Liu, Chao-Li; Riley, K.M.

    1988-01-01

    Methane formed by the microbial decomposition of buried organic matter is virtually ubiquitous in the groundwaters of Illinois. Chemical and carbon isotopic compositions are reported for gas samples collected from over 200 private and municipal water wells and from 39 small gas wells completed in glacial deposits (drift-gas wells). Carbon and hydrogen isotopic data for methane, carbon dioxide and water show that these gases were formed by the carbon dioxide reduction pathway, the same mechanism which has been previously shown to be responsible for microbial methane formation in the marine environment. The isotopic composition of methane in these samples can be closely correlated with the chemical composition of the gas and with water chemistry. The data are interpreted as indicating that isotopically very light methane is found in waters where the residence time of groundwater in the methanogenesis zone was very short relative to the methane production rate. ?? 1988.

  13. Geometry of the neoproterozoic and paleozoic rift margin of western Laurentia: Implications for mineral deposit settings

    Science.gov (United States)

    Lund, K.

    2008-01-01

    The U.S. and Canadian Cordilleran miogeocline evolved during several phases of Cryogenian-Devonian intracontinental rifting that formed the western mangin of Laurentia. Recent field and dating studies across central Idaho and northern Nevada result in identification of two segments of the rift margin. Resulting interpretations of rift geometry in the northern U.S. Cordillera are compatible with interpretations of northwest- striking asymmetric extensional segments subdivided by northeast-striking transform and transfer segments. The new interpretation permits integration of miogeoclinal segments along the length of the western North American Cordillera. For the U.S. Cordillera, miogeoclinal segments include the St. Mary-Moyie transform, eastern Washington- eastern Idaho upper-plate margin, Snake River transfer, Nevada-Utah lower-plate margin, and Mina transfer. The rift is orthogonal to most older basement domains, but the location of the transform-transfer zones suggests control of them by basement domain boundaries. The zigzag geometry of reentrants and promontories along the rift is paralleled by salients and recesses in younger thrust belts and by segmentation of younger extensional domains. Likewise, transform transfer zones localized subsequent transcurrent structures and igneous activity. Sediment-hosted mineral deposits trace the same zigzag geometry along the margin. Sedimentary exhalative (sedex) Zn-Pb-Ag ??Au and barite mineral deposits formed in continental-slope rocks during the Late Devonian-Mississippian and to a lesser degree, during the Cambrian-Early Ordovician. Such deposits formed during episodes of renewed extension along miogeoclinal segments. Carbonate-hosted Mississippi Valley- type (MVT) Zn-Pb deposits formed in structurally reactivated continental shelf rocks during the Late Devonian-Mississippian and Mesozoic due to reactivation of preexisting structures. The distribution and abundance of sedex and MVT deposits are controlled by the polarity and kinematics of the rift segment. Locally, discrete mineral belts parallel secondary structures such as rotated crustal blocks at depth that produced sedimentary subbasins and conduits for hydrothermal fluids. Where the miogeocline was overprinted by Mesozoic and Cenozoic deformation and magmatism, igneous rock-related mineral deposits are common. ??2008 Geological Society of America.

  14. Nitrogen in biogenic and abiogenic minerals from Paleozoic black shales: an NRA study

    International Nuclear Information System (INIS)

    Gallien, J.-P.; Orberger, B.; Daudin, L.; Pinti, D.L.; Pasava, J.

    2004-01-01

    Nuclear reaction analyses were performed on feldspars, quartz, abiogenic and biogenic sulfides and phosphates in organic matter-rich black shales. The goal was to study N-fractionation in black shales during diagenesis and contemporaneous hydrothermalism. Light elements (N, C) together with heavier ones (K, Ca, Ni, Fe, Zn) were analyzed by PIXE. Due to the heterogeneous sample composition, a scanning mode was used. Each phase was identified before extracting the corresponding spectra for quantification. Six phases, carrying nitrogen (and C), have been identified. K-feldspars are the richest in N (1.0-2.4 wt.%), followed by organic carbon (0.67 wt.%). Quartz, biogenic and abiogenic sulfides and phosphates contain N in the range of 0.56-1.08 wt.%. The present N-distribution in the black shales is explained by a two-step nitrogen release: (1) organic matter decay produces N, P, S nutriments for the development of a hydrothermal vent fauna and (2) biomineralization of this vent fauna liberates nitrogen to early diagenetic fluids. The extreme N enrichment of feldspars is related to its crystal structure, favoring the potassium substitution by NH 4 + , and the N-uptake during organic matter replacement

  15. Paleozoic and mesozoic GIS data from the Geologic Atlas of the Rocky Mountain Region: Volume 1

    Science.gov (United States)

    Graeber, Aimee; Gunther, Gregory

    2017-01-01

    The Rocky Mountain Association of Geologists (RMAG) is, once again, publishing portions of the 1972 Geologic Atlas of the Rocky Mountain Region (Mallory, ed., 1972) as a geospatial map and data package. Georeferenced tiff (Geo TIFF) images of map figures from this atlas has served as the basis for these data products. Shapefiles and file geodatabase features have been generated and cartographically represented for select pages from the following chapters:• Phanerozoic Rocks (page 56)• Cambrian System (page 63)• Ordovician System (pages 78 and 79)• Silurian System (pages 87 - 89)• Devonian System (pages 93, 94, and 96 - 98)• Mississippian System (pages 102 and 103)• Pennsylvanian System (pages 114 and 115)• Permian System (pages 146 and 149 - 154)• Triassic System (pages 168 and 169)• Jurassic System (pages 179 and 180)• Cretaceous System (pages 197 - 201, 207 - 210, 215, - 218, 221, 222, 224, 225, and 227).The primary purpose of this publication is to provide regional-scale, as well as local-scale, geospatial data of the Rocky Mountain Region for use in geoscience studies. An important aspect of this interactive map product is that it does not require extensive GIS experience or highly specialized software.

  16. Isotope dating of rare-metal mineral associations in black shales of Paleozoic

    International Nuclear Information System (INIS)

    Anderson, E.B.; Zaslavskij, V.G.; Lobikov, A.F.; Kuchina, G.N.; Markova, T.A.; Andreevskij, L.I.

    1987-01-01

    Results of isotopic-geochemical study of carbon-bearing (black) shales containing uranium mineralization using local uranium-lead method are presented. The carried out investigations of uranium-lead systems of host black shales and uranium-bearing metasomatites testify to the decisive role of tectonic-magmatic activization of the region during formation of polygenic-polychronic mineralized zones

  17. Paleozoic stratigraphy and tectonics in northernmost Nevada: Implications for the nature of the Antler orogeny

    Energy Technology Data Exchange (ETDEWEB)

    Ketner, K.B. (Geological Survey, Denver, CO (United States)); Ehman, K.D. (Exxon Production Research Co., Houston, TX (United States)); Repetski, J.E.; Stamm, R.G.; Wardlaw, B.R. (Geological Survey, Reston, VA (United States))

    1993-04-01

    Recent mapping and revised ages have clarified geologic relations in northern Nevada. In the Bull Run Mountains-Copper Mountains area, Proterozoic quartzite, phyllite, marble, and greenstone are overlain successively, depositionally, and nearly concordantly by the Cambrian Prospect Mountain Quartzite, Pioche Shale, and Eldorado Dolomite; the Cambrian to Ordovician Tennessee Mountain Formation composed of limestone, siltstone, and greenstone; the Ordovician Valmy Formation composed of a lower member of greenstone, limestone, mudstone, and chert, and an upper member of quartzite and argillite; and, disconformably by a Mississippian sequence of interbedded conglomerate, limestone, siltstone, and greenstone. The Prospect Mountain, Pioche, and Eldorado form a relatively shallow-water, shelf sequence containing trilobites and displaying cross-bedding, ooliths, oncolites, and fenestral fabric. The overlying Tennessee Mountain and Valmy are devoid of such features and contain many black, finely laminated, and graded strata, suggesting a deeper-water environment. This upper Proterozoic to Permian sequence is interpreted as indicating: (1) increased tectonic subsidence or sea-level rise in the latter part of the Cambrian; (2) elevation above sea level and erosion of Devonian, Silurian, and Upper Ordovician rocks in earliest Mississippian; (3) subsidence below sea level in later Early Mississippian; (4) elevation above sea level with sporadic, moderate deformation, and local, deep erosion in medial Pennsylvanian; (5) subsidence below sea level in medial Pennsylvanian or later; (6) intermittent eruption of basic volcanics peaking in Early Ordovician and again in Mississippian. The disconformable relation between the Valmy Formation and overlying Mississippian strata indicates that the Antler orogeny of earliest Mississippian age, here consisted primarily of uplift and deep erosion. Evidence of strong Early Mississippian folding and contractional faulting is not apparent.

  18. Sr-Nd-Pb isotopes of the post-paleozoic magmatism from eastern Paraguay

    International Nuclear Information System (INIS)

    Comin-Chiaramonti, P; Gasparon, M; Gomes, C.B; Antonini, P

    2001-01-01

    The Parana Angola-Namibia igneous province (PAN) is characterized by Early Cretaceous flood tholeiites and tholeiitic dyke swarms associated with alkaline rocks of Early and Late Cretaceous ages, respectively, and with scarce post-Mesozoic magmatic rocks (Comin-Chiaramonti et al., 1997; 1999; Marques et al., 1999). The Eastern Paraguay, at the westernmost side of the Parana Basin, is of special interest because: (1) it is located between two main cratonic blocks, i.e. the southernmost tip of the Amazon Craton, and the northermost exposure of the Rio de La Plata Craton; (2) it was the site of repeated Na-K-alkaline magmatism since Late-Permian-Triassic times (i.e.: 250-240 Ma, Na-alkaline; c. 145 Ma, K-alkaline; 128-126 Ma, K-alkaline; 120-90 Ma, Na-alkaline; 61-33 Ma, Na-alkaline; cf. Comin-Chiaramonti and Gomes, 1996; Comin-Chiaramonti et al., 1999), and of Early Cretaceous tholeiitic magmatism, both low- and high-Ti variants, L-Ti and H-Ti, respectively (133-131 Ma; cf. Marzoli et al., 1999); (3) the younger sodic magmatic rocks are closely associated in space to the potassic analogues (Comin- Chiaramonti et al., 1999). The paper aims discussing the most important Sr- Nd-Pb isotope features of the alkaline and tholeiitic magmas from Eastern Paraguay in comparison with the PAN analogues (au)

  19. New observations and interpretations of the enigmatic poorly know Late Paleozoic Irregularina Bykova, 1955

    Czech Academy of Sciences Publication Activity Database

    Schlagintweit, F.; Hladil, Jindřich; Nose, M.

    2013-01-01

    Roč. 9, č. 1 (2013), s. 3-22 ISSN 1842-371X Institutional support: RVO:67985831 Keywords : Parathuramminida * incertae sedis * psammobionts * cryptoendoliths * protozoa Subject RIV: DB - Geology ; Mineralogy http://www.geo-paleontologica.org/actapalrom/Online_first.html

  20. Reflectance measurements of zooclasts and solid bitumen in Lower Paleozoic shales, southern Scandinavia

    DEFF Research Database (Denmark)

    Petersen, Henrik I.; Schovsbo, Niels H.; Nielsen, Arne Thorshøj

    2013-01-01

    -like particles and graptolite fragments. The Middle Cambrian to Furongian (upper Cambrian) shales may contain sparse fragments of vase-shaped microfossils (VSM) that seem to follow the maturation trend of chitinozoans. In the present sample set, the reflectance of chitinozoans and VSM is comparable...

  1. Exploration practices and prospect of Upper Paleozoic giant gas fields in the Ordos Basin

    Directory of Open Access Journals (Sweden)

    Shengli Xi

    2015-11-01

    Full Text Available Natural gas resources is abundant in the Ordos Basin, where six gas fields with more than 100 billion cubic meters of gas reserves have been successively developed and proved, including Jingbian, Yulin, Zizhou, Wushenqi, Sulige and Shenmu. This study aims to summarize the fruitful results and functional practices achieved in the huge gas province exploration, which will be regarded as guidance and reference for the further exploration and development in this basin. Based on the past five decades' successful exploration practices made by PetroChina Changqing Oilfield Company, we first comb the presentation of geological theories at different historical stages as well as the breakthrough in the course. Then, we analyze a complete set of adaptive techniques obtained from the long-time technological research and conclude historical experiences and effective measures in terms of broadening exploration ideas, such as the fluvial delta reservoir-forming theory, giant tight gas reservoir-forming theory, the idea of sediment source system in the southern basin, etc., and innovating technical and management mechanism, such as all-digit seismic prediction, fine logging evaluation for gas formations, stimulation of tight sand reservoirs, flat project and benchmarking management, and so on.

  2. Possible Significance of Early Paleozoic Fluctuations in Bottom Current Intensity, Northwest Iapetus Ocean

    Science.gov (United States)

    Lash, Gary G.

    1986-06-01

    Sedimentologic and geochemical characteristics of red and green deep water mudstone exposed in the central Appalachian orogen define climatically-induced fluctuations in bottom current intensity along the northwest flank of the Iapetus Ocean in Early and Middle Ordovician time. Red mudstone accumulated under the influence of moderate to vigorous bottom current velocities in oxygenated bottom water produced during climatically cool periods. Interbedded green mudstone accumulated at greater sedimentation rates, probably from turbidity currents, under the influence of reduced thermohaline circulation during global warming periods. The close association of green mudstone and carbonate turbidites of Early Ordovician (late Tremadocian to early Arenigian) age suggests that a major warming phase occurred at this time. Increasing temperatures reduced bottom current velocities and resulted in increased production of carbonate sediment and organic carbon on the carbonate platform of eastern North America. Much of the excess carbonate sediment and organic carbon was transported into deep water by turbidity currents. Although conclusive evidence is lacking, this eustatic event may reflect a climatic warming phase that followed the postulated glacio-eustatic Black Mountain event. Subsequent Middle Ordovician fluctuations in bottom current intensity recorded by thin red-green mudstone couplets probably reflect periodic growth and shrinkage of an ice cap rather than major glacial episodes.

  3. Th and U in the Paleozoic and Mesozoic systems of Kitakami range (preliminary report)

    International Nuclear Information System (INIS)

    Katada, Masato; Kanaya, Hiroshi; Sato, Choji.