Sample records for radiogenic isotope systematics

  1. Tracking seasonal subglacial drainage evolution of alpine glaciers using radiogenic Nd and Sr isotope systematics: Lemon Creek Glacier, Alaska

    Clinger, A. E.; Aciego, S.; Stevenson, E. I.; Arendt, C. A.


    The transport pathways of water beneath a glacier are subject to change as melt seasons progress due to variability in the balance between basal water pressure and water flux. Subglacial hydrology has been well studied, but the understanding of spatial distribution is less well constrained. Whereas radiogenic isotopic tracers have been traditionally used as proxies to track spatial variability and weathering rates in fluvial and riverine systems, these techniques have yet to be applied extensively to the subglacial environment and may help resolve ambiguity in subglacial hydrology. Research has shown the 143Nd/144Nd values can reflect variation in source provenance processes due to variations in the age of the continental crust. Correlating the 143Nd/144Nd with other radiogenic isotope systematics such as strontium (87Sr/86Sr) provides important constraints on the role of congruent and incongruent weathering processes. Our study presents the application of Nd and Sr systematics using isotopic ratios to the suspended load of subglacial meltwater collected over a single melt season at Lemon Creek Glacier, USA (LCG). The time-series data show an average ɛNd ~ -6.83, indicating a young bedrock (~60 MYA). Isotopic variation helps track the seasonal expansion of the subglacial meltwater channels and subsequent return to early season conditions due to the parabolic trend towards less radiogenic Nd in June and towards more radiogenic Nd beginning in mid-August. However, the high variability in July and early August may reflect a mixture of source as the channels diverge and derive sediment from differently aged lithologies. We find a poor correlation between 143Nd/144Nd and 87Sr/86Sr (R2= 0.38) along with a slight trend towards more radiogenic 87Sr/86Sr values with time ((R2= 0.49). This may indicate that, even as the residence time decreases over the melt season, the LCG subglacial system is relatively stable and that the bedrock is congruently weathered. Our study

  2. Persistently strong Indonesian Throughflow during marine isotope stage 3: evidence from radiogenic isotopes

    Stumpf, Roland; Kraft, Steffanie; Frank, Martin; Haley, Brian; Holbourn, Ann; Kuhnt, Wolfgang


    The Indonesian Throughflow (ITF) connects the western Pacific Ocean with the eastern Indian Ocean, thus forming one of the major near surface current systems of the global thermohaline circulation. The intensity of the ITF has been found to be sensitive to changes in global ocean circulation, fluctuations in sea level, as well as to the prevailing monsoonal conditions of the Indonesian Archipelago and NW Australia. This study presents the first reconstruction of ITF dynamics combining radiogenic isotope compositions of neodymium (Nd), strontium (Sr), and lead (Pb) of the clay-size detrital fraction to investigate changes in sediment provenance, and paleo seawater Nd signatures extracted from the planktonic foraminifera and authigenic Fe-Mn oxyhydroxide coatings of the marine sediments focussing on marine isotope stage 3 (MIS3). Sediment core MD01-2378 was recovered within the framework of the International Marine Global Change Study (IMAGES) and is located in the area of the ITF outflow in the western Timor Sea (Scott Plateau, 13° 04.95‧ S and 121° 47.27‧ E, 1783 m water depth). In order to produce reliable seawater signatures, several extraction methods were tested against each other. The results of the study show that at this core location the extraction of surface water Nd isotope compositions from planktonic foraminifera is complicated by incomplete removal of contributions from Fe-Mn oxyhydroxides carrying ambient bottom water signatures. The bottom water Nd isotope signatures reliably obtained from the sediment coatings (average ɛNd = -5.0) document an essentially invariable water mass composition similar to today throughout the entire MIS3. The radiogenic Nd, Sr, and Pb isotope records of the clay-sized detrital fraction suggest that the Indonesian Archipelago rather than NW Australia was the main particle source at the location of core MD01-2378, and thus indicating a persistently strong ITF during MIS3. Furthermore, the variations of the detrital

  3. Error Propagation in Equations for Geochemical Modeling of Radiogenic Isotopes in Two-Component Mixing

    Surendra P Verma


    This paper presents error propagation equations for modeling of radiogenic isotopes during mixing of two components or end-members. These equations can be used to estimate errors on an isotopic ratio in the mixture of two components, as a function of the analytical errors or the total errors of geological field sampling and analytical errors. Two typical cases (``Small errors'' and ``Large errors'') are illustrated for mixing of Sr isotopes. Similar examples can be formulated for the other radiogenic isotopic ratios. Actual isotopic data for sediment and basalt samples from the Cocos plate are also included to further illustrate the use of these equations. The isotopic compositions of the predicted mixtures can be used to constrain the origin of magmas in the central part of the Mexican Volcanic Belt. These examples show the need of high quality experimental data for them to be useful in geochemical modeling of magmatic processes.

  4. Radioactive and radiogenic isotopes in sediments from Cooper Creek, Western Arnhem Land

    Frostick, A. [Charles Darwin University, Darwin, NT 0909 (Australia); ERISS, GPO Box 461, Darwin, NT 0801 (Australia)], E-mail:; Bollhoefer, A. [ERISS, GPO Box 461, Darwin, NT 0801 (Australia); Parry, D.; Munksgaard, N. [Charles Darwin University, Darwin, NT 0909 (Australia); Evans, K. [ERISS, GPO Box 461, Darwin, NT 0801 (Australia)


    Protection of the environment post-mining is a key objective of rehabilitation, especially where runoff and erosion from rehabilitated mine sites could potentially lead to contamination of the surrounding land and watercourses. As part of an overall assessment of the success of rehabilitation at the former Nabarlek uranium (U) mine, an appraisal of stable lead (Pb) isotopes, radionuclides and trace metals within sediments and soils was conducted to determine the off site impacts from a spatial and temporal perspective. The study found localised areas on and adjacent to the site where soils had elevated levels of trace metals and radionuclides. Lead isotope ratios are highly radiogenic in some samples, indicating the presence of U-rich material. There is some indication that erosion products with more radiogenic Pb isotope ratios have deposited in sediments downstream of the former ore body. However, there is no indication that the radiogenic erosion products found on the mine site at present have significantly contaminated sediments further downstream of Cooper Creek.

  5. Mesoclimatic imprints on palaeoclimate records from rift graben sediments: Implications from stable and radiogenic isotope data from mammalian tooth enamel

    Brachert, Thomas; Brügmann, Gerhard; Mertz, Dieter F.; Kullmer, Ottmar; Schrenk, Friedemann; Ssemmanda, Immaculate; Taubald, Herbert


    The Neogene of East Africa is regarded as a period of long-term increasing aridity. It has been proposed that this is the result of a cooling of Indian Ocean surface waters or is caused by tectonic processes leading to the updoming of East Africa. However, mesoclimatic effects induced by the dynamics of the formation of rifts involving uplift of the rift shoulder and subsidence of the rift valley have been largely neglected so far. We have studied mesoclimatic variability by monitoring the evolution of the Albertine Rift (western branch of the East African Rift System) for the last 7 Ma using the tooth enamel of hippopotamids (Mammalia) as environmental archive. These non-migratory, water-dependant terrestrial mammals are particularly useful for palaeoclimate reconstructions because they have no dietary preferences with respect to C3 - C4 vegetation. By inhabiting lakes and rivers, Hippopotamids document mesoclimates of topographic depressions such as rift valleys and, therefore, changes of relative valley depth rather than entirely global climate changes. Average stable isotope compositions of oxygen and carbon were obtained from transects along drill cores through enamel. The Sr isotopic composition was determined by laser ablation multi-collector ICP-MS (Nu Plasma). 13C/12C isotope values in enamel imply the presence of pure C3 browsers (delta 13C -1 per mil VPDB) from 2.3 to 1.0 Ma. This suggests a spread of grasslands during a maximum in aridity from 2.3 to 1.0 Ma. 18O/16O shows a systematic increase from values of -4.5 at 7.0 Ma to +1.4 per mil (delta 18O VPDB) 2.0 Ma ago. The Sr isotopic composition also increases systematically from 0.713 to 0.717 during this time period. This parallel evolution of 18O/16O and 87Sr/86Sr being climate and water provenance proxies, respectively, is interpreted in terms of rift shoulder uplift/subsidence of the rift valley floor. The oxygen isotopic composition of tooth enamel reflects the evolution of the meteoric water

  6. The growth of the continental crust: Constraints from radiogenic isotope geochemistry

    Taylor, Paul N.


    Most models for evolution of continental crust are expressed in the form of a diagram illustrating the cumulative crustal mass (normalized relative to the present crustal mass) as a function of time. Thus, geochronological data inevitably play a major role in either constructing or testing crustal growth models. For all models, determining the start-time for effective crustal accretion is of vital importance. To this end, the continuing search for, and reliable characterization of, the most ancient crustal rock-units remains a worthy enterprise. Another important role for geochronology and radiogenic isotope geochemistry is to assess the status of major geological events as period either of new crust generation or of reworking of earlier formed continental crust. For age characterization of major geological provinces, using the critieria outined, the mass (or volume) of crust surviving to the present day should be determinable as a function of crust formation age. More recent developments, however, appear to set severe limitations on recycling of crust, at least by the process of sediment subduction. In modeling crustal growth without recycling, valuable constaints on growth rate variations through time can be provided if variations in the average age of the continental crust can be monitored through geological history. The question of the average age of the exposed continental crust was addressed by determining Sm-Nd crustal residence model ages (T-CR) for fine-grained sediment loads of many of the world's major rivers.

  7. Automated Sample Preparation for Radiogenic and Non-Traditional Metal Isotopes: Removing an Analytical Barrier for High Sample Throughput

    Field, M. Paul; Romaniello, Stephen; Gordon, Gwyneth W.; Anbar, Ariel D.; Herrmann, Achim; Martinez-Boti, Miguel A.; Anagnostou, Eleni; Foster, Gavin L.


    MC-ICP-MS has dramatically improved the analytical throughput for high-precision radiogenic and non-traditional isotope ratio measurements, compared to TIMS. The generation of large data sets, however, remains hampered by tedious manual drip chromatography required for sample purification. A new, automated chromatography system reduces the laboratory bottle neck and expands the utility of high-precision isotope analyses in applications where large data sets are required: geochemistry, forensic anthropology, nuclear forensics, medical research and food authentication. We have developed protocols to automate ion exchange purification for several isotopic systems (B, Ca, Fe, Cu, Zn, Sr, Cd, Pb and U) using the new prepFAST-MC™ (ESI, Nebraska, Omaha). The system is not only inert (all-flouropolymer flow paths), but is also very flexible and can easily facilitate different resins, samples, and reagent types. When programmed, precise and accurate user defined volumes and flow rates are implemented to automatically load samples, wash the column, condition the column and elute fractions. Unattended, the automated, low-pressure ion exchange chromatography system can process up to 60 samples overnight. Excellent reproducibility, reliability, recovery, with low blank and carry over for samples in a variety of different matrices, have been demonstrated to give accurate and precise isotopic ratios within analytical error for several isotopic systems (B, Ca, Fe, Cu, Zn, Sr, Cd, Pb and U). This illustrates the potential of the new prepFAST-MC™ (ESI, Nebraska, Omaha) as a powerful tool in radiogenic and non-traditional isotope research.

  8. Radiogenic nephropathy; Radiogene Nephropathie

    Gotthardt, M. [Univ. Medisch Centrum St Radboud, Nijmegen (Netherlands). Nucleaire Geneeskunde


    Patient-individual dosimetric analyses are a useful tool in external beam radiotherapy (EBR) to protect patients from side effects such as radiogenic nephropathy. At this point in time, individual dosimetry is not used as a standard in patient treated with radiolabelled antibody fragments or polypeptides. The reasons are a number of problems, which make patient dosimetry more challenging than in EBR. While in EBR, the dose is distributed evenly in the organ and the organ volume can exactly be determined, in internal radiotherapy the tracer is not evenly distributed within the organ leading to a non-uniform dose distribution. In addition, the dose rate of the most commonly used radionuclides is lower than in EBR and the range of their radiation differ, so that the radiobiological effects are differing considerably in comparison to EBR. Conclusion: More complex models have to be used for clinical kidney dosimetry in internal radiotherapy. In this paper, we give a concise overview of the reasons for accumulation of radiotracers in the kidney, the most recent developments in kidney dosimetry, and approaches to reduce the kidney uptake of radiotracers in order to avoid radiogenic nephropathy. (orig.)

  9. Pleistocene paleo-groundwater as a pristine fresh water resource in southern Germany – evidence from stable and radiogenic isotopes

    Geldern, Robert van, E-mail: [Friedrich-Alexander-University Erlangen-Nuremberg (FAU), Department of Geography and Geosciences, GeoZentrum Nordbayern, Schlossgarten 5, 91054 Erlangen (Germany); Baier, Alfons; Subert, Hannah L. [Friedrich-Alexander-University Erlangen-Nuremberg (FAU), Department of Geography and Geosciences, GeoZentrum Nordbayern, Schlossgarten 5, 91054 Erlangen (Germany); Kowol, Sigrid [Erlanger Stadtwerke AG, Äußere Brucker Str. 33, 91052 Erlangen (Germany); Balk, Laura; Barth, Johannes A.C. [Friedrich-Alexander-University Erlangen-Nuremberg (FAU), Department of Geography and Geosciences, GeoZentrum Nordbayern, Schlossgarten 5, 91054 Erlangen (Germany)


    Shallow groundwater aquifers are often influenced by anthropogenic contaminants or increased nutrient levels. In contrast, deeper aquifers hold potentially pristine paleo-waters that are not influenced by modern recharge. They thus represent important water resources, but their recharge history is often unknown. In this study groundwater from two aquifers in southern Germany were analyzed for their hydrogen and oxygen stable isotope compositions. One sampling campaign targeted the upper aquifer that is actively recharged by modern precipitation, whereas the second campaign sampled the confined, deep Benkersandstein aquifer. The groundwater samples from both aquifers were compared to the local meteoric water line to investigate sources and conditions of groundwater recharge. In addition, the deep groundwater was dated by tritium and radiocarbon analyses. Stable and radiogenic isotope data indicate that the deep-aquifer groundwater was not part of the hydrological water cycle in the recent human history. The results show that the groundwater is older than ∼20,000 years and most likely originates from isotopically depleted melt waters of the Pleistocene ice age. Today, the use of this aquifer is strictly regulated to preserve the pristine water. Clear identification of such non-renewable paleo-waters by means of isotope geochemistry will help local water authorities to enact and justify measures for conservation of these valuable resources for future generations in the context of a sustainable water management. - Highlights: • Groundwater from deep aquifer identified as paleo-water with age over 20,000 years. • Low stable isotope values indicate recharge during Pleistocene. • Shallow aquifer mirrors stable isotope signature of average modern precipitation. • Identification of non-renewable paleo-waters enhance sustainable water management. • Strict protection measures of authorities justified by isotope geochemistry.

  10. Geochemical proxies of ocean circulation and weathering inputs: Radiogenic isotopes of Nd, Pb, Sr, Hf, and Os

    Frank, Martin, E-mail: [IFM-GEOMAR, Leibniz Institute of Marine Sciences at the University of Kiel, Wischhofstrasse 1-3, 24148 Kiel (Germany)


    Marine records of the radiogenic isotope composition of the elements neodymium (Nd), lead (Pb), hafnium (Hf), strontium (Sr), and osmium (Os) allow the reconstruction of past continental weathering inputs on different time scales as a function of their respective oceanic residence times. Sr and Os have oceanic residence times significantly longer than the global mixing time of the ocean and are efficiently mixed on a global scale. Their isotope composition changes on long time scales as a function of plate tectonics and major orogenies, which allows their use as precise stratigraphic tools for the entire Phanerozoic. In contrast, Hf, Pb, and in particular Nd, have residence times on the order of or shorter than the global mixing time of the ocean, which results in distinct isotopic signatures of water masses and allows the reconstruction of past water mass mixing and weathering inputs on both long and short time scales. Here applications of these isotopes systems with a focus on the shorter residence time tracers are reviewed (without claiming to be comprehensive) and problems and potential solutions are discussed.

  11. Pleistocene paleo-groundwater as a pristine fresh water resource in southern Germany--evidence from stable and radiogenic isotopes.

    van Geldern, Robert; Baier, Alfons; Subert, Hannah L; Kowol, Sigrid; Balk, Laura; Barth, Johannes A C


    Shallow groundwater aquifers are often influenced by anthropogenic contaminants or increased nutrient levels. In contrast, deeper aquifers hold potentially pristine paleo-waters that are not influenced by modern recharge. They thus represent important water resources, but their recharge history is often unknown. In this study groundwater from two aquifers in southern Germany were analyzed for their hydrogen and oxygen stable isotope compositions. One sampling campaign targeted the upper aquifer that is actively recharged by modern precipitation, whereas the second campaign sampled the confined, deep Benkersandstein aquifer. The groundwater samples from both aquifers were compared to the local meteoric water line to investigate sources and conditions of groundwater recharge. In addition, the deep groundwater was dated by tritium and radiocarbon analyses. Stable and radiogenic isotope data indicate that the deep-aquifer groundwater was not part of the hydrological water cycle in the recent human history. The results show that the groundwater is older than ~20,000 years and most likely originates from isotopically depleted melt waters of the Pleistocene ice age. Today, the use of this aquifer is strictly regulated to preserve the pristine water. Clear identification of such non-renewable paleo-waters by means of isotope geochemistry will help local water authorities to enact and justify measures for conservation of these valuable resources for future generations in the context of a sustainable water management.

  12. Biogeochemistry of stable Ca and radiogenic Sr isotopes in a larch-covered permafrost-dominated watershed of Central Siberia

    Bagard, Marie-Laure; Schmitt, Anne-Désirée; Chabaux, François; Pokrovsky, Oleg S.; Viers, Jérôme; Stille, Peter; Labolle, François; Prokushkin, Anatoly S.


    Stable Ca and radiogenic Sr isotope compositions were measured in different compartments (stream water, soil solutions, rocks, soils and soil leachates and vegetation) of a small permafrost-dominated watershed in the Central Siberian Plateau. The Sr and Ca in the area are supplied by basalt weathering and atmospheric depositions, which significantly impact the Sr isotopic compositions. Only vegetation significantly fractionates the calcium isotopes within the watershed. These fractionations occur during Ca uptake by roots and along the transpiration stream within the larch trees and are hypothesised to be the result of chromatographic processes and Ca oxalate crystallisations during Ca circulation or storage within plant organs. Biomass degradation significantly influences the Ca isotopic compositions of soil solutions and soil leachates via the release of light Ca, and organic and organo-mineral colloids are thought to affect the Ca isotopic compositions of soil solutions by preferential scavenging of 40Ca. The imprint of organic matter degradation on the δ44/40Ca of soil solutions is much more significant for the warmer south-facing slope of the watershed than for the shallow and cold soil active layer of the north-facing slope. As a result, the available stock of biomass and the decomposition rates appear to be critical parameters that regulate the impact of vegetation on the soil-water system in permafrost areas. Finally, the obtained δ44/40Ca patterns contrast with those described for permafrost-free environments with a much lower δ44/40Ca fractionation factor between soils and plants, suggesting specific features of organic matter decomposition in permafrost environments. The biologically induced Ca isotopic fractionation observed at the soil profile scale is not pronounced at the scale of the streams and large rivers in which the δ44/40Ca signature may be controlled by the heterogeneity of lithological sources.

  13. Hydrothermal versus active margin sediment supply to the eastern equatorial Pacific over the past 23 million years traced by radiogenic Pb isotopes: Paleoceanographic and paleoclimatic implications

    Höfig, Tobias W.; Hoernle, Kaj; Hauff, Folkmar; Frank, Martin


    We investigated the evolution of the Pb isotopic composition of bulk sediments on the Cocos Plate in sedimentary successions of Deep Sea Drilling Project (DSDP) Site 495 and Ocean Drilling Program/Integrated Ocean Drilling Program (ODP/IODP) Site 1256 over the past 23 million years of depositional history. Our study addresses the relationship of the sediment Pb isotope record to plate tectonics, weathering inputs, and paleoceanography. It is the first effort to characterize the Pb isotopic evolution of eastern equatorial Pacific sedimentation covering the entire tectonic pathway of the Cocos Plate from its formation at the East Pacific Rise to its arrival at the Central American subduction zone. The Sites 495 and 1256 bulk sediment Pb isotope records are fully consistent over time despite distinct differences between the type of sediment deposited at both locations. A systematic and continuous trend from ∼23 to ∼6-4 Ma toward more radiogenic Pb isotopic compositions, e.g., 206Pb/204Pb ratios increase from 18.29 to 18.81, reflects a decrease in the contribution of hydrothermal particles from the East Pacific Rise and an increase in the predominantly eolian contribution of mixed weathering products from the continental arcs of the Northern and south Central Andes as well as from southern Mexico. Surprisingly, both the Pb isotopic composition of the detrital fraction and that of past seawater indicate that inputs from nearby Central America and the Galápagos Archipelago did not significantly contribute to the sediments of our core locations but were overwhelmed by other sediment sources. A systematic change to less radiogenic Pb isotope ratios in sediments younger than ∼4-3 Ma, reaching present-day 206Pb/204Pb values near 18.70, reflects a reduction of the continental input from the South Central Volcanic Zone of the Andean Arc and increased contributions from southern Mexican igneous complexes. This isotopic trend reversal took place as a consequence of

  14. Mechanical properties and permeability of hydrogen isotopes through CrNi35WTiAl alloy, containing radiogenic helium

    Maksimkin, I.P.; Yukhimchuk, A.A.; Boitsov, I.Y.; Malkov, I.L.; Musyaev, R.K.; Baurin, A.Y.; Shevnin, E.V.; Vertey, A.V. [Russian Federal Nuclear Centre, RFNC-VNIIEf, Sarov (Russian Federation)


    The long-term contact of structural materials (SM) with tritium-containing media makes their properties in terms of kinetic permeability of hydrogen isotopes change. This change is the consequence of the defect formation in SM due to the result of {sup 3}He build-up generated by the radioactive decay of tritium dissolved in SM. This paper presents the experimental results concerning the permeability of hydrogen isotopes through CrNi35WTiAl alloy containing {sup 3}He and the impact of the presence of {sup 3}He and H on its mechanical properties. Tensile tests of cylindrical samples containing various concentrations of {sup 3}He (90, 230 and 560 appm) have been performed in inert and hydrogen atmospheres. The build-up of {sup 3}He has been made using the 'helium trick' technique. The maximal decrease in the plastic characteristics of the CrNi35WTiAl alloy occurs in samples with the highest {sup 3}He (560 appm) content at 873 K. The permeability of deuterium through the CrNi35WTiAl alloy in the initial state and that with 560 appm of {sup 3}He content was explored. The presence of this {sup 3}He concentration has shown an increase in deuterium permeability, evidently due to structural changes in the material under the impact of radiogenic helium.

  15. Automated sample preparation for radiogenic and non-traditional metal isotope analysis by MC-ICP-MS

    Field, M. P.; Romaniello, S. J.; Gordon, G. W.; Anbar, A. D.


    High throughput analysis is becoming increasingly important for many applications of radiogenic and non-traditional metal isotopes. While MC-ICP-MS instruments offer the potential for very high sample throughout, the requirement for labor-intensive sample preparation and purification procedures remains a substantial bottleneck. Current purification protocols require manually feeding gravity-driven separation columns, a process that is both costly and time consuming. This bottleneck is eliminated with the prepFAST-MC™, an automated, low-pressure ion exchange chromatography system that can process from 1 to 60 samples in unattended operation. The syringe-driven system allows sample loading, multiple acid washes, column conditioning and elution cycles necessary to isolate elements of interest and automatically collect up to 3 discrete eluent fractions at user-defined intervals (time, volume and flow rate). Newly developed protocols for automated purification of uranium illustrates high throughput (>30 per run), multiple samples processed per column (>30), complete (>99%) matrix removal, high recovery (> 98%, n=25), and excellent precision (2 sigma =0.03 permil, n=10). The prepFAST-MC™ maximizes sample throughput and minimizes costs associated with personnel and consumables providing an opportunity to greatly expand research horizons in fields where large isotopic data sets are required, including archeology, geochemistry, and climate/environmental science

  16. Radiogenic p-isotopes from SNIa, nuclear physics uncertainties and Galactic chemical evolution compared with values in primitive meteorites

    Travaglio, C; Rauscher, T; Dauphas, N; Roepke, F K R; Hillebrandt, W


    The nucleosynthesis of proton-rich isotopes is calculated for multi-dimensional Chandrasekhar-mass models of Type Ia supernovae with different metallicities. The predicted abundances of the short-lived radioactive isotopes 92Nb, 97Tc, 98Tc and 146Sm are given in this framework. The abundance seeds are obtained by calculating s-process nucleosynthesis in the material accreted onto a carbon-oxygen white dwarf from a binary companion. A fine grid of s-seeds at different metallicities and 13C-pocket efficiencies is considered. A galactic chemical evolution model is used to predict the contribution of SNIa to the solar system p-nuclei composition measured in meteorites. Nuclear physics uncertainties are critical to determine the role of SNeIa in the production of 92Nb and 146Sm. We find that, if standard Chandrasekhar-mass SNeIa are at least 50% of all SNIa, they are strong candidates for reproducing the radiogenic p-process signature observed in meteorites.

  17. Compilation of Radiogenic Isotope Data in Mexico and their Petrogenetic Implications

    Ignacio S Torres-Alvarado; Surendra P Verma1; Gerardo Carrasco-Nunez


    Seven hundred and twenty-five Sr, two hundred and forty-three Nd and one hundred and fifty-one Pb isotopic ratios from seven different Mexican magmatic provinces were compiled in an extensive geochemical database. Data were arranged according to the Mexican geological provinces, indicating for each province total number of analyses, range and mean of values and two times standard deviation (2). Data from seven provinces were included in the database: Mexican Volcanic Belt (MVB), Sierra Madre Occidental (SMO), Baja California (BC), Pacific Ocean (PacOc), Altiplano (AP), Sierra Madre del Sur (SMS), and Sierra Madre Oriental (SMOr). Isotopic values from upper mantle and lower crustal xenoliths, basement outcrops and sediments from the Cocos Plate were also compiled. In the MVB the isotopic ratios range as follows: 87Sr/86Sr 0.703003-0.70841; 143Nd/144Nd 0.512496-0.513098; 206Pb/204Pb 18.567-19.580; 207Pb/204Pb 15.466-15.647; 208Pb/204Pb 38.065-38.632. The SMO shows a large variation in 87Sr/86Sr ranging from ~ 0.7033 to 0.71387. 143Nd/144Nd ratios are relatively less variable with values from 0.51191 to 0.51286. Pb isotope ratios in the SMO are as follows: 206Pb/204Pb 18.060-18.860; 207Pb/204Pb 15.558- 15.636; 208Pb/204Pb 37.945-38.625. PacOc rocks show the most depleted Sr and Nd isotopic ratios (0.70232-0.70567 for Sr and 0.512631-0.513261 for Nd). Pb isotopes for PacOc show the following range: 206Pb/204Pb 18.049-19.910; 207Pb/204Pb 15.425-15.734; 208Pb/204Pb 37.449-39.404. The isotopic ratios of the AP rocks seem to be within the range of those from the PacOc. Most samples with reported Sr and Nd isotopic data are spread within and around the ``mantle array''. The SMO seems to have been formed by a mixing process between mantle derived magmas and continental crust. The MVB appears to have a larger mantle component, with AFC as the dominant petrogenetic process for the evolved rocks. There is still a need for Pb isotopic data in all Mexican magmatic provinces andof

  18. Radiogenic uveitis

    Lommatzsch, P.K.; Weise, B. (Karl-Marx-Universitaet, Leipzig (German Democratic Republic). Bereich Medizin)


    Short irradiation (0.25 Gy/min) causes stronger exudative reactions in the rabbit's eye (amotio chorioideae at retinae) than protracted irradiation (0.025 Gy/min) with equal total dose. In patients with melanoma of the choroid membrane short irradiation times (1 - 6 days) more frequently cause early exudative reactions (amotio chorioideae et retinae, hemorrhages of the vessels of the retina) than longer irradiation times (7 - 14 days). The radiogenic exudative reactions in general recede spontaneously.

  19. Systematic Osmium Isotope Binary Mixing Arrays in Arc Volcanism

    Alves, S.; Alves, S.; Schiano, P.; Capmas, F.; Allegre, C. J.


    Isotopic and geochemical studies on subduction-related lavas aim at constraining the nature of their mantle sources and the respective roles of source heterogeneity and petrogenetic processes in their compositions. Many components are potentially involved in producing the geochemical signatures of arc lavas: depleted mantle, subducted oceanic crust and sediments, and the overlying continental or oceanic crust. A further complication in characterizing mantle sources of arc lavas is complex mixing of some component parts via derivative fluids or melts released from the slab. Os isotope ratios are potential tracers of slab contribution in arc lavas because 1) subducted sediments are very radiogenic in Os compared to the upper mantle, and 2) Re behaves as a moderately incompatible element during mantle partial melting, whereas Os is highly compatible. Therefore, MORB have much higher Re/Os ratios than peridotites. Consequently, old oceanic crust is likely to be extremely more radiogenic than the depleted upper mantle so that recycled basaltic components should be identified by their elevated 187Os/188Os ratios. Os isotope ratios and Os and Re concentrations have been measured in 55 lavas coming from 10 different subduction zones. Samples span a large range of major element concentrations (from basalts to dacites) and Mg# (from 0.32 to 0.81). The 10 subduction zones, namely the Lesser Antilles, Java, Papua-New Guinea, the Philippines, Izu-Bonin, Kamchatka, the Aleutians, Mexico, Colombia and Peru-Chile, have a range of basement nature and thickness, as well as a range of age and sediment cover of the subducting plate. Measured 187Os/188Os ratios range from 0.130 to 1.524 and Os concentrations range from 0.048 to 46 ppt. Re concentrations range from 37 to 915 ppt. Os initial isotope ratios are systematically positively and linearly correlated with the inverse of Os concentrations in arc lavas from a given volcano, indicating that the Os isotopic compositions always

  20. Potential application of radiogenic isotopes and geophysical methods to understand the hydrothermal dystem of the Upper Geyser Basin, Yellowstone National Park

    Paces, James B.; Long, Andrew J.; Koth, Karl R.


    Numerous geochemical and geophysical studies have been conducted at Yellowstone National Park to better understand the hydrogeologic processes supporting the thermal features of the Park. This report provides the first 87Sr/86Sr and 234U/238U data for thermal water from the Upper Geyser Basin (UGB) intended to evaluate whether heavy radiogenic isotopes might provide insight to sources of groundwater supply and how they interact over time and space. In addition, this report summarizes previous geophysical studies made at Yellowstone National Park and provides suggestions for applying non-invasive ground and airborne studies to better understand groundwater flow in the subsurface of the UGB. Multiple samples from Old Faithful, Aurum, Grand, Oblong, and Daisy geysers characterized previously for major-ion concentrations and isotopes of water (δ2H, δ18O, and 3H) were analyzed for Sr and U isotopes. Concentrations of dissolved Sr and U are low (4.3–128 ng g-1 Sr and 0.026–0.0008 ng g-1 U); consequently only 87Sr/86Sr data are reported for most samples. Values of 87Sr/86Sr for most geysers remained uniform between April and September 2007, but show large increases in all five geysers between late October 2007 and early April, 2008. By late summer of 2008, 87Sr/86Sr values returned to values similar to those observed a year earlier. Similar patterns are not present in major-ion data measured on the same samples. Furthermore, large geochemical differences documented between geysers are not observed in 87Sr/86Sr data, although smaller differences between sites may be present. Sr-isotope data are consistent with a stratified hydrologic system where water erupted in spring and summer of 2007 and summer of 2008 equilibrated with local intracaldera rhyolite flows at shallower depths. Water erupted between October 2007 and April 2008 includes greater amounts of groundwater that circulated deep enough to acquire a radiogenic 87Sr/86Sr, most likely from Archean basement

  1. Calcium biogeochemical cycle at the beech tree-soil solution interface from the Strengbach CZO (NE France): insights from stable Ca and radiogenic Sr isotopes

    Schmitt, Anne-Désirée; Gangloff, Sophie; Labolle, François; Chabaux, François; Stille, Peter


    Calcium (Ca) is the fourth most abundant element in mineral nutrition and plays key physiological and structural roles in plant metabolism. At the soil-water-plant scale, stable Ca isotopes are a powerful tool for the identification of plant-mineral interactions and recycling via vegetation. Radiogenic Sr isotopes are often used as tracers of Ca sources and mixtures of different reservoirs. In this study, stable Ca and radiogenic Sr are combined and analysed in several organs from two beech trees that were collected in June and September in the Strengbach critical zone observatory (CZO) (NE France) and in corresponding soil solutions. At the beech-tree scale, this study confirms the field Ca adsorption (i.e., physico-chemical mechanism and not vital effects) on carboxyl acid groups of pectin in the apoplasm of small roots. The analysis of the xylem sap and corresponding organs shows that although the Strengbach CZO is nutrient-poor, Ca seems to be non-limiting for tree-growth. Different viscosities of xylem sap between the stemwood and branches or leaves can explain δ44/40Ca values in different tree-organs. The bark and phloem 40Ca-enrichments could be due to Ca-oxalate precipitation in the bark tissues and in the phloem. The results from this study regarding the combination of these two isotopic systems show that the isotopic signatures of the roots are dominated by Ca fractionation mechanisms and Sr, and thus Ca, source variations. In contrast, translocation mechanisms are only governed by Ca fractionation processes. This study showed that at the root-soil solution interface, litter degradation was not the main source of Ca and Sr and that the soil solutions are not the complement of uptake by roots for samples from the 2011/2013 period. The opposite is observed for older samples. These observations indicate the decreasing contribution of low radiogenic Sr fluxes, such as recycling, alimenting the soil solutions. Such reduced importance of nutrient uptake and

  2. A model for osmium isotopic evolution of metallic solids at the core-mantle boundary

    Munir Humayun


      Radiogenic and unradiogenic Os isotopes require a new physical model A cumulate pile model of the CMB provides a suitable explanation Other isotope systematics are consistent with this model Some...

  3. Radiogenic p-isotopes from type Ia supernova, nuclear physics uncertainties, and galactic chemical evolution compared with values in primitive meteorites

    Travaglio, C. [INAF—Astrophysical Observatory Turin, Strada Osservatorio 20, I-10025 Pino Torinese (Turin) (Italy); Gallino, R. [B2FH Association, I-10025 Pino Torinese (Turin) (Italy); Rauscher, T. [Centre for Astrophysics Research, School of Physics, Astronomy and Mathematics, University of Hertfordshire, Hatfield AL10 9AB (United Kingdom); Dauphas, N. [Origins Laboratory, Department of the Geophysical Sciences and Enrico Fermi Institute, The University of Chicago, Chicago, IL 60637 (United States); Röpke, F. K. [Universität Würzburg, Am Hubland, D-97074 Würzburg (Germany); Hillebrandt, W., E-mail:, E-mail: [Max-Planck-Institut für Astrophysik, Karl-Schwarzschild-Str. 1, D-85748 Garching bei München (Germany)


    The nucleosynthesis of proton-rich isotopes is calculated for multi-dimensional Chandrasekhar-mass models of Type Ia supernovae (SNe Ia) with different metallicities. The predicted abundances of the short-lived radioactive isotopes {sup 92}Nb, {sup 97,} {sup 98}Tc, and {sup 146}Sm are given in this framework. The abundance seeds are obtained by calculating s-process nucleosynthesis in the material accreted onto a carbon-oxygen white dwarf from a binary companion. A fine grid of s-seeds at different metallicities and {sup 13}C-pocket efficiencies is considered. A galactic chemical evolution model is used to predict the contribution of SN Ia to the solar system p-nuclei composition measured in meteorites. Nuclear physics uncertainties are critical to determine the role of SNe Ia in the production of {sup 92}Nb and {sup 146}Sm. We find that, if standard Chandrasekhar-mass SNe Ia are at least 50% of all SN Ia, they are strong candidates for reproducing the radiogenic p-process signature observed in meteorites.

  4. Osmium-Isotope and Platinum-Group-Element Systematics of Impact-Melt Rocks, Chesapeake Bay Impact Structure, Virginia, USA

    Lee, Seung Ryeol; Wright Horton, J., Jr.; Walker, Richard J.


    Osmium (Os) isotopes and platinum-group elements (PGEs) are useful for geochemically identifying a meteoritic component within impact structures, because meteorites are typically characterized by low (187)Os/(188)Os ratios and high PGE concentrations. In contrast, most types of crustal target rocks have high radiogenic Os and very low PGE concentrations. We have examined Os isotope and PGE systematics of impact-melt rocks and pre-impact target rocks from a 2004 test hole in the late Eocene Chesapeake Bay impact structure and from nearby coreholes. Our goal is to determine the proportion of the projectile component in the melt rock Additional information is included in the original extended abstract.

  5. The provenance of Cretaceous to Quaternary sediments in the Tarfaya basin, SW Morocco: Evidence from trace element geochemistry and radiogenic Nd-Sr isotopes

    Ali, Sajid; Stattegger, Karl; Garbe-Schönberg, Dieter; Frank, Martin; Kraft, Steffanie; Kuhnt, Wolfgang


    We present trace element compositions, rare earth elements (REEs) and radiogenic Nd-Sr isotope analyses of Cretaceous to recent sediments of the Tarfaya basin, SW Morocco, in order to identify tectonic setting, source rocks composition and sediments provenance. The results suggest that the sediments originate from heterogeneous source areas of the Reguibat Shield and the Mauritanides (West African Craton), as well as the western Anti-Atlas, which probably form the basement in this area. For interpreting the analyzed trace element results, we assume that elemental ratios such as La/Sc, Th/Sc, Cr/Th, Th/Co, La/Co and Eu/Eu∗ in the detrital silicate fraction of the sedimentary rocks behaved as a closed system during transport and cementation, which is justified by the consistency of all obtained results. The La/Y-Sc/Cr binary and La-Th-Sc ternary relationships suggest that the Tarfaya basin sediments were deposited in a passive margin setting. The trace element ratios of La/Sc, Th/Sc, Cr/Th and Th/Co indicate a felsic source. Moreover, chondrite-normalized REE patterns with light rare earth elements (LREE) enrichment, a flat heavy rare earth elements (HREE) and negative Eu anomalies can also be attributed to a felsic source for the Tarfaya basin sediments. The Nd isotope model ages (TDM = 2.0-2.2 Ga) of the Early Cretaceous sediments suggest that sediments were derived from the Eburnean terrain (Reguibat Shield). On the other hand, Late Cretaceous to Miocene--Pliocene sediments show younger model ages (TDM = 1.8 Ga, on average) indicating an origin from both the Reguibat Shield and the western Anti-Atlas. In contrast, the southernmost studied Sebkha Aridal section (Oligocene to Miocene-Pliocene) yields older provenance ages (TDM = 2.5-2.6 Ga) indicating that these sediments were dominantly derived from the Archean terrain of the Reguibat Shield.

  6. Enhanced sea-ice export from the Arctic to the GIN seas during the Younger Dryas: A "Canadian" source from radiogenic isotope signatures

    Hillaire-Marcel, C.; Maccali, J.; Not, C.; Poirier, A.


    The Younger Dryas (YD) cooling event and the related slowing of the Atlantic Meridional Overturning Circulation (AMOC) have been linked to a large array of processes. The most widely supported causal mechanism involves an influx of freshwater into the North Atlantic Ocean linked to a partial drainage of glacial Lake Agassiz. Recently, a northward drainage route, through the Mackenzie River outlet into the Arctic Ocean, has been suggested from land-based studies [Murton et al., Nature 464, 740-743]. Sedimentological and geochemical analysis of cores raised from Lomonosov Ridge and the Fram Strait area, yield relatively robust evidence for enhanced ice-rafting deposition -IRD- (with a 5-fold increase -) during the critical interval. At Lomonosov, the corresponding sedimentary layer (from ca. 13 to 12 ka) is marked by a pulse of detrital carbonates in the silt to sand fractions, with approximately equal amounts of calcite and dolomite, pointing towards an Arctic Canadian sediment source area [Not & Hillaire-Marcel, Nature Communication, Jan. 31, 2012]. The layer also depicts a 5 fold increase 230Th-excess, which we link to an enhanced flux of scavenging particles. At both sites, the geochemical signatures of the YD-layer, based on elemental (Zr/Al) and isotopic (Sr, Nd and Pb) data on bulk sediments and residues ensuing from the removal of exchangeable fractions (Zr/Al, Nd, Pb, Sr), are used to identify detrital sediment source areas. Whereas three major source areas variably contributed to IRD during the MIS 3-Present interval (i.e., the Russian, Canadian and Greenland margins), the YD interval singles out by strongelemental and isotopic excursions, notably a peak in radiogenic Sr, indicating prominent supplies from the Canadian end-member. This suggests enhanced sea-ice production and drifting along the BeaufordGyre, then the Trans-Polar Drift. A major drainage event along the Mackenzie outlet area, as proposed in the above reference,would be a suitable trigger for

  7. Understanding the interaction of injected CO2 and reservoir fluids in the Cranfield enhanced oil recovery (EOR) field (MS, USA) by non-radiogenic noble gas isotopes

    Gyore, Domokos; Stuart, Finlay; Gilfillan, Stuart


    Identifying the mechanism by which the injected CO2 is stored in underground reservoirs is a key challenge for carbon sequestration. Developing tracing tools that are universally deployable will increase confidence that CO2 remains safely stored. CO2 has been injected into the Cranfield enhanced oil recovery (EOR) field (MS, USA) since 2008 and significant amount of CO2 has remained (stored) in the reservoir. Noble gases (He, Ne, Ar, Kr, Xe) are present as minor natural components in the injected CO2. He, Ne and Ar previously have been shown to be powerful tracers of the CO2 injected in the field (Györe et al., 2015). It also has been implied that interaction with the formation water might have been responsible for the observed CO2 loss. Here we will present work, which examines the role of reservoir fluids as a CO2 sink by examining non-radiogenic noble gas isotopes (20Ne, 36Ar, 84Kr, 132Xe). Gas samples from injection and production wells were taken 18 and 45 months after the start of injection. We will show that the fractionation of noble gases relative to Ar is consistent with the different degrees of CO2 - fluid interaction in the individual samples. The early injection samples indicate that the CO2 injected is in contact with the formation water. The spatial distribution of the data reveal significant heterogeneity in the reservoir with some wells exhibiting a relatively free flow path, where little formation water is contacted. Significantly, in the samples, where CO2 loss has been previously identified show active and ongoing contact. Data from the later stage of the injection shows that the CO2 - oil interaction has became more important than the CO2 - formation water interaction in controlling the noble gas fingerprint. This potentially provides a means to estimate the oil displacement efficiency. This dataset is a demonstration that noble gases can resolve CO2 storage mechanisms and its interaction with the reservoir fluids with high resolution

  8. Re-Os isotopic systematics of primitive lavas from the Lassen region of the Cascade arc, California

    Borg, L.E.; Brandon, A.D.; Clynne, M.A.; Walker, R.J.


    Rhenium-osmium isotopic systematics of primitive calc-alkaline lavas from the Lassen region appear to be controlled by mantle wedge processes. Lavas with a large proportion of slab component have relatively low Re and Os abundances, and have radiogenic Os and mid ocean ridge basalt-like Sr and Pb isotopic compositions. Lavas with a small proportion of slab component have higher Re and Os elemental abundances and display mantle-like Os, Sr, Nd, and Pb isotopic compositions. Assimilation with fractional crystallization can only generate the Re-Os systematics of the Lassen lavas from a common parent if the distribution coefficient for Re in sulfide is ~40-1100 times higher than most published estimates and if most incompatible element abundances decrease during differentiation. High Re/Os ratios in mid ocean ridge basalts makes subducted oceanic crust a potential source of radiogenic Os in volcanic arcs. The slab beneath the southernmost Cascades is estimated to have 187Os/188Os ratios as high as 1.4. Mixing between a slab component and mantle wedge peridotite can generate the Os isotopic systematics of the Lassen lavas provided the slab component has a Sr/Os ratio of ~7.5X105 and Os abundances that are 100-600 times higher than mid ocean ridge basalts. For this model to be correct, Os must be readily mobilized and concentrated in the slab component, perhaps as a result of high water and HCl fugacities in this subduction environment. Another possible mechanism to account for the correlation between the magnitude of the subduction geochemical signature and Os isotopic composition involves increasing the stability of an Os-bearing phase in mantle wedge peridotites as a result of fluxing with the slab component. Melting of such a source could yield low Os magmas that are more susceptible to crustal contamination, and hence have more radiogenic Os isotopic compositions, than magmas derived from sources with a smaller contribution from the slab. Thus, the addition of the

  9. Technical Report on the Behavior of Trace Elements, Stable Isotopes, and Radiogenic Isotopes During the Processing of Uranium Ore to Uranium Ore Concentrate

    Marks, N. E. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Borg, L. E. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Eppich, G. R. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Gaffney, A. M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Genneti, V. G. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Hutcheon, I. D. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Kristo, M. J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Lindvall, R. E. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Ramon, C. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Robel, M. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Roberts, S. K. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Schorzman, K. C. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Sharp, M. A. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Singleton, M. J. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Williams, R. W. [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)


    The goals of this SP-1 effort were to understand how isotopic and elemental signatures behave during mining, milling, and concentration and to identify analytes that might preserve geologic signatures of the protolith ores. The impurities that are preserved through the concentration process could provide useful forensic signatures and perhaps prove diagnostic of sample origin.

  10. Probing Archean lithosphere using the Lu-Hf isotope systematics of peridotite xenoliths from Somerset Island kimberlites, Canada

    Schmidberger, Stefanie S.; Simonetti, Antonio; Francis, Don; Gariépy, Clément


    A knowledge of the Hf isotopic composition of the subcontinental lithosphere beneath Archean cratons is essential to constrain the Hf isotope budget of the Earth's mantle. Hf isotopic measurements were obtained by MC-ICP-MS for a suite of refractory peridotite xenoliths and constituent garnets from the Nikos kimberlite (100 Ma) on Somerset Island in order to constrain the isotopic composition and age of the lithosphere beneath the northern Canadian craton. The low-temperature Nikos peridotites (Somerset lithosphere, are characterized by higher 176Lu/ 177Hf ratios (0.03-0.05) and Hf isotopic values ( 176Hf/ 177Hf (0.1Ga)=0.28296-0.28419) than the deep-seated high-temperature peridotites (>1100°C; 0.004-0.03, 0.28265-0.28333, respectively). These differences in Hf isotope signatures suggest that shallow and deep subcontinental lithosphere beneath Somerset Island represent isotopically distinct domains and do not share a common petrogenetic history. The Lu-Hf isotope systematics of the shallow low-temperature peridotites define a positively sloped line that plot along a 2.8 Ga reference isochron. A number of these peridotites are characterized by highly radiogenic Hf isotopic compositions suggestive of long-term radiogenic ingrowth (billions of years). These findings are consistent with an interpretation that the shallow Somerset lithosphere (to depths of ˜150 km) stabilized in the Archean. The majority of the high-temperature peridotites plot closer to the composition of the host kimberlite. Although the observed isotopic variation may be attributed in part to kimberlite-related Hf addition, it is possible that these deep-seated xenoliths represent younger mantle. The superchondritic 176Lu/ 177Hf ratios observed for a number of the shallow low-temperature peridotites indicate strong fractionation of Lu and Hf, suggesting mantle root formation in the garnet stability field (depths >80 km). The Hf isotope compositions for the Somerset low-temperature peridotites

  11. Preliminary Report on U-Th-Pb Isotope Systematics of the Olivine-Phyric Shergottite Tissint

    Moriwaki, R.; Usui, T.; Yokoyama, T.; Simon, J. I.; Jones, J. H.


    Geochemical studies of shergottites suggest that their parental magmas reflect mixtures between at least two distinct geochemical source reservoirs, producing correlations between radiogenic isotope compositions, and trace element abundances.. These correlations have been interpreted as indicating the presence of a reduced, incompatible-element- depleted reservoir and an oxidized, incompatible-element-rich reservoir. The former is clearly a depleted mantle source, but there has been a long debate regarding the origin of the enriched reservoir. Two contrasting models have been proposed regarding the location and mixing process of the two geochemical source reservoirs: (1) assimilation of oxidized crust by mantle derived, reduced magmas, or (2) mixing of two distinct mantle reservoirs during melting. The former clearly requires the ancient martian crust to be the enriched source (crustal assimilation), whereas the latter requires a long-lived enriched mantle domain that probably originated from residual melts formed during solidification of a magma ocean (heterogeneous mantle model). This study conducts Pb isotope and U-Th-Pb concentration analyses of the olivine-phyric shergottite Tissint because U-Th-Pb isotope systematics have been intensively used as a powerful radiogenic tracer to characterize old crust/sediment components in mantle- derived, terrestrial oceanic island basalts. The U-Th-Pb analyses are applied to sequential acid leaching fractions obtained from Tissint whole-rock powder in order to search for Pb isotopic source components in Tissint magma. Here we report preliminary results of the U-Th-Pb analyses of acid leachates and a residue, and propose the possibility that Tissint would have experienced minor assimilation of old martian crust.

  12. Radiogenic and stable isotopes of mid-Miocene silicic volcanism in eastern Oregon: Evidence for variable and high Sr / low δ18O domains west of the terrane-cratonic lithosphere transition

    Jenkins, E. N.; Streck, M. J.; Ramos, F. C.; Bindeman, I. N.


    Widespread mid-Miocene rhyolite volcanism of eastern Oregon mostly coeval with flood basalts of the Columbia River Basalt Province allows for mapping crustal domains using radiogenic and stable isotopes. Rhyolites are thought to be derived in large part by partial melting of the crust and thus yield direct information on the composition of the crust. Silicic volcanism is expressed in the form of numerous domes and tuffs exposed over a wide area (~300 km in N-S dimension and ~100 km in E-W dimension) west of the craton boundary, which runs parallel but mostly east of the Oregon-Idaho state border as delineated by geophysical characteristics and isotopic transitions. Here, we mainly focus on initial 87Sr/86Sr ratios and δ18O obtained from mid-Miocene silicic volcanic centers in eastern Oregon. Our data, in combination with data from the literature, indicate variable 87Sr/86Sr mostly along longitudinal sections, yet more similar ratios in latitudinal directions. Except for rare examples on the west side, dispersion of 87Sr/86Sr ratios among both silicic and basaltic rocks occurs eastward of 118.6°W. For example, rhyolites in the Owyhee region between 117.10°W and 117.25°W retain 87Sr/86Sr ratios ranging from 0.70413 to 0.70566. The most radiogenic Sri ratio of 0.70787 in our study is obtained on a plagioclase separate from Buchanan Dome complex located near the western boundary of our study area. Feldspar separates and fresh groundmass of samples from adjacent centers yield similar 87Sr/86Sr ratios. δ18O values for feldspars range from below 2‰ to above 9‰. In addition, there is a crude trend of rhyolites having lower δ18O and more radiogenic 87Sr/86Sr ratios. With one exception, all samples with 87Sr/86Sr above 0.7050 are depleted in 18O (δ18O 6‰). The most depleted oxygen ratios (<2‰) come from rhyolites ~80 km west of the cratonic margin reflecting remelting or assimilation of hydrothermally altered crust. Yet, some compositionally similar rhyolites

  13. Systematic Study on Triaxial Superdeformed Bands of Hf Isotopes

    ZHANG Da-Li; DING Bin-Gang


    Properties of the triaxial superdeformed (TSD) bands of Hf isotopes are investigated systematically within the supersymmetry scheme including many-body interactions and a perturbation possessing the SO(5) (or SU(5)) symmetry on the rotational symmetry. Quantitatively good results of the γ-ray energies, the dynamical moments of inertia,and the spin of the TSD bands in Hf isotopes are obtained. It shows that this approach is quite powerful in describing the properties of the triaxial superdeformation in Hf isotopes.

  14. Magnesium isotope systematics in Martian meteorites

    Magna, Tomáš; Hu, Yan; Teng, Fang-Zhen; Mezger, Klaus


    Magnesium isotope compositions are reported for a suite of Martian meteorites that span the range of petrological and geochemical types recognized to date for Mars, including crustal breccia Northwest Africa (NWA) 7034. The δ26Mg values (per mil units relative to DSM-3 reference material) range from -0.32 to -0.11‰; basaltic shergottites and nakhlites lie to the heavier end of the Mg isotope range whereas olivine-phyric, olivine-orthopyroxene-phyric and lherzolitic shergottites, and chassignites have slightly lighter Mg isotope compositions, attesting to modest correlation of Mg isotopes and petrology of the samples. Slightly heavier Mg isotope compositions found for surface-related materials (NWA 7034, black glass fraction of the Tissint shergottite fall; δ26Mg > -0.17‰) indicate measurable Mg isotope difference between the Martian mantle and crust but the true extent of Mg isotope fractionation for Martian surface materials remains unconstrained. The range of δ26Mg values from -0.19 to -0.11‰ in nakhlites is most likely due to accumulation of clinopyroxene during petrogenesis rather than garnet fractionation in the source or assimilation of surface material modified at low temperatures. The rather restricted range in Mg isotope compositions between spatially and temporally distinct mantle-derived samples supports the idea of inefficient/absent major tectonic cycles on Mars, which would include plate tectonics and large-scale recycling of isotopically fractionated surface materials back into the Martian mantle. The cumulative δ26Mg value of Martian samples, which are not influenced by late-stage alteration processes and/or crust-mantle interactions, is - 0.271 ± 0.040 ‰ (2SD) and is considered to reflect δ26Mg value of the Bulk Silicate Mars. This value is robust taking into account the range of lithologies involved in this estimate. It also attests to the lack of the Mg isotope variability reported for the inner Solar System bodies at current

  15. Generation and fate of glacial sediments in the central Transantarctic Mountains based on radiogenic isotopes and implications for reconstructing past ice dynamics

    Farmer, G. Lang; Licht, Kathy J.


    The Nd, Sr and Pb isotopic compositions of glacial tills from the Byrd and Nimrod Glaciers in the central Transantarctic Mountains (TAM) in East Antarctica were obtained to assess the sources of detritus transported by these ice masses. Tills from lateral moraines along the entire extent of both glaciers have isotopic compositions consistent with their derivation predominately from erosion of adjacent bedrock. Fine- (<63μ) and coarser-grained (0.5 mm-2 mm) sediment from these tills have identical isotopic characteristics, indicating that fine-grained detritus is the product of further comminution of coarser sediments. Comparison of present-day till isotopic data to existing data from fine-grained LGM tills in the central Ross Sea confirm that these were deposited from East Antarctic ice that expanded through the TAM and indicates that the LGM sediments are mixtures of detritus eroded along the entire path of ice transiting the TAM. If specific lithologies were preferentially eroded as ice passed through the TAM, it is not clearly evident in the Ross Sea till isotopic compositions. Our data do demonstrate, however, that glacial tills generated from erosion of inboard regions of the mountain belt yield sediment with a larger component of 560 Ma to 600 Ma detrital zircons and lower average εNd(0) values (<-5) than that produced further downstream. As a result, past retreat of ice grounding-lines up the narrow valleys of the TAM resulting in active erosion of inboard region should recognizable in glacial sediments deposited in the Ross Sea and so provide a means to identify times when the East Antarctic ice sheet was smaller than today. This study highlights both the value and necessity of utilizing multiple provenance methods in evaluating glacial erosion and transport when reconstructing past ice sheet dynamics.

  16. Iron isotope systematics of the Skaergaard intrusion

    Lesher, Charles; Lundstrom, C.C.; Barfod, Gry

    report the results of a broad study of the iron isotope compositions of gabbros within the layered and upper border series of the Skaergaard intrusion, pegmatite and granophyre associated with these gabbroic rocks, and the sandwich horizon thought to represent the product of extreme differentiation and/or...... crystallization on non-traditional stable isotope systems, particularly iron. FeTi oxide minerals (titanomagnetite and ilmenite) appear after ~60% of the magma had solidified. This was a significant event affecting the liquid line of descent and potentially accompanied by iron isotope fractionation. Here we...... liquid immiscibility. Forty-eight whole rock samples from well-constrained stratigraphic levels in the intrusion were crushed, powdered and dissolved, followed by iron separation by ion chromatography. Purified solutions were analyzed by MC- ICPMS in high-resolution mode using the sample-std bracket...

  17. Iron isotope systematics of the Skaergaard intrusion

    Lesher, Charles; Lundstrom, C.C.; Barfod, Gry

    crystallization on non-traditional stable isotope systems, particularly iron. FeTi oxide minerals (titanomagnetite and ilmenite) appear after ~60% of the magma had solidified. This was a significant event affecting the liquid line of descent and potentially accompanied by iron isotope fractionation. Here we...... report the results of a broad study of the iron isotope compositions of gabbros within the layered and upper border series of the Skaergaard intrusion, pegmatite and granophyre associated with these gabbroic rocks, and the sandwich horizon thought to represent the product of extreme differentiation and....../or liquid immiscibility. Forty-eight whole rock samples from well-constrained stratigraphic levels in the intrusion were crushed, powdered and dissolved, followed by iron separation by ion chromatography. Purified solutions were analyzed by MC- ICPMS in high-resolution mode using the sample-std bracket...

  18. Iron isotope systematics in planetary reservoirs

    Sossi, Paolo A.; Nebel, Oliver; Foden, John


    Iron is the only polyvalent major element, and controls reduction-oxidation (redox) reactions in a host of geologic processes and reservoirs, from the mineral- to planetary-scale, on Earth and in space. Mass transfer of Fe is often accompanied by changes in bonding environment, meaning the resultant variation in bond-strength in crystals, liquids and gases induces stable isotope fractionation, even at high temperatures. In the absence of iron exchange, electron transfer can also affect iron's valence state and calculated oxygen fugacity (fO2), however its isotope composition remains unchanged. Thus, iron isotopes are a powerful tool to investigate processes that involve mass transfer, redox reactions and changes in bonding environment in planetary systems. Primitive chondritic meteorites show remarkable isotopic homogeneity, δ57 Fe = - 0.01 ± 0.01 ‰ (2SE), over a wide range of Fe/Mg vs Ni/Mg, a proxy for fO2 in the solar nebula. In chondrites, there are iron isotope differences between metal and silicates that become more pronounced at higher metamorphic grades. However, on a planetary scale, Mars and Vesta overlap with chondrites, preserving no trace of core formation or volatile depletion on these bodies. Upon assessment of pristine lherzolites, the Bulk Silicate Earth is heavier than chondrites (δ57 Fe = + 0.05 ± 0.01 ‰; 2SE), and similar to or slightly lighter than the Moon. That the mantles of some differentiated inner solar system bodies extend to heavier compositions (+ 0.2 ‰) than chondrites may principally result from volatile depletion either at a nebular or late accretion stage. Within terrestrial silicate reservoirs, iron isotopes provide insight into petrogenetic and geodynamic processes. Partial melting of the upper mantle produces basalts that are heavier than their sources, scaling with degree of melting and driving the increasingly refractory peridotite to lighter compositions. Mid-Ocean Ridge Basalts (MORBs) are homogeneous to δ57 Fe

  19. Rapid Environmental Fluctuations Recorded over the Last Glacial/Interglacial Cycle in the Sediments from Borehole PRGL1-4 (Gulf of Lions; Western Mediterranean) using Radiogenic Isotopes (Sr & Nd)

    Nizou, J.


    The study of sediments deposited and preserved in oceanic basins unable us to examine how terrigenous sediment supply varied through time in relation to paleoenvironmental and climatic changes on land. The geochemical and isotopic compositions of marine sediment are used to unravel its provenance, and provide information about its formation. Providing that the paleoclimatic frame is known, such data give an insight into the rock-source location and allow us to decipher between genetic processes of mechanical erosion and chemical alteration. Borehole PRGL1-4 (European project PROMESS), located in the Gulf of Lions (W Mediterranean) at 300 mwd, was investigated geochemically at high-temporal resolution over the last glacial/interglacial cycle (i.e. 130 ka) to study sediment-source variations during rapid climate changes. Besides, sediments originating from the Rhône's and the Pyreneo-Languedocian's catchment areas have been analyzed to measure the isotopic composition of five source end-members that are the Alps, the Higher Rhône valley, the Lower Rhône valley, the Languedoc and the Pyrenees. Epsilon Nd and 87Sr/86Sr were measured on 60 samples encompassing 4 marine isotopic stages with an emphasis on Heinrich events. The epsilon Nd values of PRGL1-4 lean towards the Lower Rhône valley unradiogenic end-member during cold stadial intervals, and towards the Alpine radiogenic end-member during warm interstadials. The presence of an ice cap over the crystalline Alpine watershed during cold phases could prevent the sediments originating from this region from reaching the Gulf of Lions. The same pattern is observed during the time of Heinrich events. An influence of the sea level variations on the sedimentation at the borehole site during the Heinrich events is unlikely since they are only 10 to 15 m in amplitude. Furthermore, a major isotopic shift in epsilon Nd mean values is displayed around 40 ka that coincides with the connection of the Durance to the Rhône River

  20. Partial radiogenic heat model for Earth revealed by geoneutrino measurements

    S. Abe; . et al.; M.P. Decowski


    The Earth has cooled since its formation, yet the decay of radiogenic isotopes, and in particular uranium, thorium and potassium, in the planet’s interior provides a continuing heat source. The current total heat flux from the Earth to space is 44.2±1.0 TW, but the relative contributions from residu

  1. Isotope and trace element systematics in a spinel-lherzolite-bearing suite of basanitic volcanic rocks from San Luis Potosi, Mexico

    Pier, J.E.G.


    Lherzolite-bearing basanitic magmas of Quaternary age have erupted to form maars, lava/cinder cones and lava flows in two volcanic fields (Ventura and Santo Domingo) in the central Mexican state of San Luis Potosi. The systematics of the radiogenic isotopes of Sr, Nd, and Pb and the relationship between these parameters and elemental compositions are used to investigate the petrogenesis of the volcanic rocks and the nature of their mantle sources. Sr and Nd isotopic data are presented for 19 basanitic rocks, 5 kaersutites, and 6 lherzolitic xenoliths; Pb data presented for the same 19 volcanic rocks and 4 of the 5 kaersutites. The isotopic compositions for all of these samples fall within the mantle range defined by MORBs and OIBs. The basanites generally plot within the OIB field on isotopic diagrams; most of the kaersutites are displaced to slightly more-depleted (i.e. MORB-like) values than the volcanic samples and the xenoliths, with one exception, are significantly more-depleted than either of these sample-types. As crustal contamination is considered unlikely for most of the volcanic samples, these trends are thought to arise from mixing multiple mantle components. The absence of similar isotopic elemental relationships for Epsilon Nd and the lack of correlation between {sup 206}Pb/{sup 204}Pb and the other Pb isotopes require a mixture of at least three mantle reservoirs: a depleted reservoir analogous to that of the MORBs, a St. Helena-type component, and a third component, which primarily affects Sr and {sup 208}Pb/{sup 204}Pb composition. This third component carries relatively radiogenic Sr and {sup 208}Pb/{sup 204}Pb and appears to be correlated with the degree of melting.

  2. Radiogenic and stable Sr isotope ratios (87Sr/86Sr, δ88/86Sr) as tracers of riverine cation sources and biogeochemical cycling in the Milford Sound region of Fiordland, New Zealand

    Andrews, M. Grace; Jacobson, Andrew D.; Lehn, Gregory O.; Horton, Travis W.; Craw, Dave


    This study reports radiogenic Sr isotope ratios (87Sr/86Sr), stable Sr isotope ratios (δ88/86Sr), and major ion concentrations for river, rock, sediment, soil, and plant samples collected from the Cleddau and Hollyford catchments in the Milford Sound region of Fiordland, New Zealand. The catchments primarily drain gabbro, but some tributaries access limestone and volcanogenic sediments. The goal of the study was to understand controls on riverine δ88/86Sr values in a landscape with multiple factors that may influence chemical weathering, including dense vegetation, high rainfall, and abundant, freshly-eroded Holocene fluvio-glacial and landslide debris. Rivers draining gabbro have higher δ88/86Sr values than bedrock, by as much as ∼0.14‰, and the δ88/86Sr values strongly correlate with molar Ca/Sr ratios (R2 = 0.69). Leaching of rocks and sediment reveals no evidence for the preferential dissolution of minerals having high δ88/86Sr values and Ca/Sr ratios. In-stream Sr isotope fractionation seems unlikely because comparison against 87Sr/86Sr and Ca/Sr ratios demonstrates that riverine δ88/86Sr values conservatively trace water-mass mixing. The riverine data are best explained by the input of soil water, which is distinct from potential bedrock end-members (i.e., silicates and carbonates) based on δ88/86Sr but indistinguishable in terms of Ca/Sr and 87Sr/86Sr. While strontium isotope fractionation during secondary mineral formation and pedogenesis is possible, clay mineral formation is minor and most soils are poorly developed. Instead, soil water δ88/86Sr values more likely reflect plant uptake. Plant samples yielded a wide range of δ88/86Sr values, but on average, they are lower than those for bedrock, consistent with the expectation that plants preferentially incorporate lighter Sr isotopes. Mass-balance constraints, together with 87Sr/86Sr ratios, indicate that soil water δ88/86Sr values are ∼0.30‰ higher than bedrock δ88/86Sr values, and

  3. A change of Sr cycle in the Ediacaran Ocean: Evidence from radiogenic and stable isotope ratios of Sr, in Three Gorges, South China.

    Sawaki, Y.; Tahata, M.; Komiya, T.; Maruyama, S.


    Objective. To decode surface environmental changes and patterns of biological evolution during the Ediacaran Methods employed. We undertook deep drilling in Three Gorges area in South China to obtain continuous and fresh samples without surface alteration and oxidation. 87Sr/86Sr and 88Sr/86Sr ratios of the fresh carbonate rocks were measured with multiple collector-inductively coupled plasma-mass spectrometric techniques. We discuss the surface environmental change in the Ediacaran by comparing the Sr isotope ratios with 13C/12C and 18O/16O. Result. The chemostratigraphy of 87Sr/86Sr ratios of the drilled samples displays a smooth curve and two large positive shifts in the Ediacaran. The combination of the detailed chemostratigraphies of 13C/12C, 18O/16O, and 87Sr/86Sr enable us to find connections among them and indicates that the first large positive shift of 87Sr/86Sr is slightly preceded by negative 13C/12C and positive 18O/16O excursions. The second large positive shift of 87Sr/86Sr is simultaneous with positive 13C/12C shift and clearly precedes next negative 13C/12C excursion. Considering Mn content and Fe content of carbonate rocks, which respond to redox in the ocean, the first positive shift can be explained by Gaskiers glaciation. Exposed surface of continental crust were increased by regression accompanied by Gaskiers glaciation and enhanced weathering rate by rivers increased seawater 87Sr/86Sr. The second positive shift of 87Sr/86Sr is a long-term fluctuation. We speculate enhanced weathering rate, resulting from convergence of Gondwana supercontinent, as a cause of the second positive shift of 87Sr/86Sr. Chemostratigraphy of 88Sr/86Sr also displays a smooth curve. Before Gaskiers glaciation, 88Sr/86Sr curve have a negative correlation with 87Sr/86Sr fluctuation. We interpret that this negative correlation is explained by mass-dependent fractionation. When Sr are increased in ocean (high 87Sr/86Sr), 86Sr are selectively taken in carbonate (low 88Sr

  4. Role of radiogenic heat generation in surface heat flow formation

    Khutorskoi, M. D.; Polyak, B. G.


    Heat generation due to decay of long-lived radioactive isotopes is considered in the Earth's crust of the Archean-Proterozoic and Paleozoic provinces of Eurasia and North America. The heat flow that forms in the mantle is calculated as the difference between the heat flow observed at the boundary of the solid Earth and radiogenic heat flow produced in the crust. The heat regime in regions with anomalously high radiogenic heat generation is discussed. The relationship between various heat flow components in the Precambrian and Phanerozoic provinces has been comparatively analyzed, and the role of erosion of the surfaceheat- generating layer has been estimated.



    Measurements of S, O, and radiogenic isotope ratios are all potentially powerful tracers of magma interaction with country rocks and the importance of assimilation processes in the genesis of magmatic Ni-CuPGE deposits. Sulfur isotope measurements of deposits such as those in the 1.1 Ga Duluth Complex, the Permo-Triassic intrusions of the Noril'sk area, and the 1.4 Ga Kabanga intrusions provide evidence for the derivation of S from both sulfide-and sulfate-bearing country rocks. The 1.3 Ga Voisey's Bay deposit provides an example where δ34S values of the ores commonly fall within the accepted mantle range of 0 ± 2‰, but detailed studies of Proterozoic metasedimentary country rocks show that their weighted average δ34S value is also within this range. A thorough knowledge of the isotopic compositions of potential contaminants is essential for a proper evaluation of the role of country rock derived S in ore formation. When O and radiogenic isotopic measurements are employed as tracers to evaluate magma-country rock interaction it is essential to provide evidence that open system processes have not perturbed the isotopic systematics. Low-temperature hydrothermal processes can mask evidence of high-temperature processes in the oxygen isotope system, and in radiogenic systems such as Re/Os and Pb where involved elements may be mobile under hydrothermal conditions, or host phases may close to exchange and uptake at different temperatures. Careful petrographic observation and analyses of individual minerals may be required before the models involving the contamination of magmas by country rocks can be meaningfully applied.%硫、氧同位素和放射性同位素比值在示踪岩浆与围岩的反应及在岩浆镍-铜-铂族元素矿床成因中同化过程的重要性方面有很大作用.如1.1 Ga的Duluth杂岩、Noril'sk地区二叠-三叠纪侵入岩和1.4 Ga的Kabanga侵入岩体中矿床的硫同位素测定结果证明硫来自含

  6. High-precision Mg isotopic systematics of bulk chondrites

    Schiller, Martin; Handler, Monica R.; Baker, Joel A.


    Variations of the mass-independent abundance of 26Mg ( δ26Mg*) and stable Mg ( δ25Mg) isotope composition of chondrites are important because they constrain the homogeneity of 26Al and Mg isotopes in the proto-planetary disc and the validity of the short-lived 26Al-to- 26Mg chronometer applied to meteorites. We present high-precision Mg isotope data and Al/Mg ratios of chondrites representing nearly all major chondrite classes, including a step-leaching experiment on the CM2 chondrite Murchison. δ26Mg* variations in leachates of Murchison representing acid soluble material are ≤ 30 times smaller than reported for neutron-rich isotopes of Ti and Cr and do not reveal resolvable deficits in δ26Mg* (-0.002 to + 0.118‰). Very small variations in δ26Mg* anomalies in bulk chondrites (-0.006 to + 0.019‰) correlate with increasing 27Al/ 24Mg ratios and δ50Ti, reflecting the variable presence of calcium-aluminium-rich inclusions (CAIs) in some types of carbonaceous chondrites. Similarly, release of radiogenic 26Mg produced by 26Al decay from CAI material in the step-leaching of Murchison best explains the high δ26Mg* observed in the last, aggressive, leaching steps of this experiment. Overall, the observed variations in δ26Mg* are small and potential differences beyond that which result from the presence of CAI-like material cannot be detected within the analytical uncertainties of this study (± 0.004‰). The results do not allow radical heterogeneity of 26Al (≥±30%) or measurable Mg nucleosynthetic heterogeneity (≥±0.005‰) to have existed on a planetesimal scale in the proto-planetary disc. Combined with published δ26Mg* data for CAIs, the bulk chondrite data yield a precise initial ( 26Al/ 27Al) 0 = (5.21 ± 0.06) × 10 -5 and δ26Mg* = -0.0340 ± 0.0016‰ for the Solar System. However, it is not possible with the currently available data to determine with certainty whether CAIs and the material from which planetesimals accreted including

  7. Coupled Pb isotopic and trace element systematics of the Tissint meteorite: Geochemical signatures of the depleted shergottite source mantle

    Moriwaki, Ryota; Usui, Tomohiro; Simon, Justin I.; Jones, John H.; Yokoyama, Tetsuya; Tobita, Minato


    The application of Martian meteorite U-Th-Pb isotope systematics to track the geochemical evolution of the Martian mantle has had limited success because of the difficulty in discriminating an indigenous magmatic Pb component from secondary near-surface components that have additionally been overprinted by terrestrial contamination. To mitigate this challenge, a successive acid-leaching experiment was conducted on the Tissint meteorite, the freshest, witnessed fall of a primitive, olivine-bearing Martian basalt. Trace element concentration analyses of acid leachates and residues indicate that secondary terrestrial contaminants were effectively removed by the early steps in the leaching experiments and that the acid residues contain pristine Pb from Tissint. The acid residue, which shows the most depleted REE signature, also has the least radiogenic Pb isotopic composition (206Pb/204Pb = 10.948, 207Pb/204Pb = 11.187, 208Pb/204Pb = 30.228). A two-stage mantle evolution model based on this composition indicates that the Tissint mantle has the lowest μ-value (238U/204Pb = 1.62 ± 0.09) among the shergottite sources.

  8. Unlocking the zinc isotope systematics of iron meteorites

    Bridgestock, L. J.; Williams, H.; Rehkämper, M.; Larner, F.; Giscard, M. D.; Hammond, S.; Coles, B.; Andreasen, R.; Wood, B. J.; Theis, K. J.; Smith, C. L.; Benedix, G. K.; Schönbächler, M.


    Zinc isotope compositions (δ66Zn) and concentrations were determined for metal samples of 15 iron meteorites across groups IAB, IIAB, and IIIAB. Also analyzed were troilite and other inclusions from the IAB iron Toluca. Furthermore, the first Zn isotope data are presented for metal-silicate partitioning experiments that were conducted at 1.5 GPa and 1650 K. Three partitioning experiments with run durations of between 10 and 60 min provide consistent Zn metal-silicate partition coefficients of ∼0.7 and indicate that Zn isotope fractionation between molten metal and silicate is either small (at less than about ±0.2‰) or absent. Metals from the different iron meteorite groups display distinct ranges in Zn contents, with concentrations of 0.08-0.24 μg/g for IIABs, 0.8-2.5 μg/g for IIIABs, and 12-40 μg/g for IABs. In contrast, all three groups show a similar range of δ66Zn values (reported relative to ‘JMC Lyon Zn’) from +0.5‰ to +3.0‰, with no clear systematic differences between groups. However, distinct linear trends are defined by samples from each group in plots of δ66Zn vs. 1/Zn, and these correlations are supported by literature data. Based on the high Zn concentration and δ66Zn ≈ 0 determined for a chromite-rich inclusion of Toluca, modeling is employed to demonstrate that the Zn trends are best explained by segregation of chromite from the metal phase. This process can account for the observed Zn-δ66Zn-Cr systematics of iron meteorite metals, if Zn is highly compatible in chromite and Zn partitioning is accompanied by isotope fractionation with Δ66Znchr-met≈-1.5‰. Based on these findings, it is likely that the parent bodies of the IAB complex, IIAB and IIIAB iron meteorites featured δ66Zn values of about -1.0 to +0.5‰, similar to the Zn isotope composition inferred for the bulk silicate Earth and results obtained for chondritic meteorites. Together, this implies that most solar system bodies formed with similar bulk Zn isotope

  9. Hydrogen Isotopic Systematics of Nominally Anhydrous Phases in Martian Meteorites

    Tucker, Kera

    Hydrogen isotope compositions of the martian atmosphere and crustal materials can provide unique insights into the hydrological and geological evolution of Mars. While the present-day deuterium-to-hydrogen ratio (D/H) of the Mars atmosphere is well constrained (~6 times that of terrestrial ocean water), that of its deep silicate interior (specifically, the mantle) is less so. In fact, the hydrogen isotope composition of the primordial martian mantle is of great interest since it has implications for the origin and abundance of water on that planet. Martian meteorites could provide key constraints in this regard, since they crystallized from melts originating from the martian mantle and contain phases that potentially record the evolution of the H 2O content and isotopic composition of the interior of the planet over time. Examined here are the hydrogen isotopic compositions of Nominally Anhydrous Phases (NAPs) in eight martian meteorites (five shergottites and three nakhlites) using Secondary Ion Mass Spectrometry (SIMS). This study presents a total of 113 individual analyses of H2O contents and hydrogen isotopic compositions of NAPs in the shergottites Zagami, Los Angeles, QUE 94201, SaU 005, and Tissint, and the nakhlites Nakhla, Lafayette, and Yamato 000593. The hydrogen isotopic variation between and within meteorites may be due to one or more processes including: interaction with the martian atmosphere, magmatic degassing, subsolidus alteration (including shock), and/or terrestrial contamination. Taking into consideration the effects of these processes, the hydrogen isotope composition of the martian mantle may be similar to that of the Earth. Additionally, this study calculated upper limits on the H2O contents of the shergottite and nakhlite parent melts based on the measured minimum H2O abundances in their maskelynites and pyroxenes, respectively. These calculations, along with some petrogenetic assumptions based on previous studies, were subsequently used

  10. SIMS zircon ages and Nd isotope systematics of the 2.2 Ga mafic intrusions in northern and eastern Finland

    Eero Hanski


    Full Text Available Using the SIMS, ID-TIMS and Sm-Nd isotopic methods and the electron microprobe, we have studied several differentiated mafic intrusions of the c. 2.2 Ga gabbro-wehrlite association (GWA from four Paleoproterozoic schist belts and the Archean Kuhmo Greenstone Belt. Back-scattered electron images and electron microprobe analyses revealed that zircon crystals vary from well-preserved to turbid and highly altered with individual grains often displaying irregular, hydrated, CaO-bearing domains. In the most pristine domains, suitable for establishing the crystallization ages, SIMS 207Pb/206Pb ages fall in the range of 2210–2220 Ma, which is consistent with the most concordant ID-TIMS UPb ages. One of the studied intrusions that had previously yielded a conventional U-Pb date of less than 2.0 Ga, could be shown by spot analysis to belong to the 2.2 Ga family. In contrast to the well-preserved zircon domains, altered domains exhibit a variable and often strong U-Pb discordance up to 70 % and have distinctly lower 207Pb/206Pb ages. Some zircon grains record isotopic resetting at the time of the Svecofennian orogeny(ca. 1.8–1.9 Ga, while the most discordant ones project in the concordia diagram to late Paleozoic lower intercept ages indicating a relative recent Pb loss. The mineral chemistry of zircon suggests that the leakage of radiogenic Pb can be ascribed to an opensystembehavior related to hydrothermal alteration via action of CaCl2-bearing fluids.Common albitization of plagioclase in the GWA intrusions has caused this mineral to behave as an open system with regard to the Sm-Nd isotopic systematics. Despite this uncertainty, our Nd isotopic data indicate that the magma that produced the GWA intrusions in various parts of northern and eastern Finland was isotopically homogeneousand had an initial εNd(2220 Ma value of c. +0.6 precluding significant upper crustal contamination upon emplacement and subsequent fractional crystallization.

  11. Radiogenic cell transformation and carcinogenesis

    Yang, T. C.; Georgy, K. A.; Mei, M.; Durante, M.; Craise, L. M.


    Radiation carcinogenesis is one of the major biological effects considered important in the risk assessment for space travel. Various biological model systems, including both cultured cells and animals, have been found useful for studying the carcinogenic effects of space radiations, which consist of energetic electrons, protons and heavy ions. The development of techniques for studying neoplastic cell transformation in culture has made it possible to examine the cellular and molecular mechanisms of radiation carcinogenesis. Cultured cell systems are thus complementary to animal models. Many investigators have determined the oncogenic effects of ionizing and nonionizing radiation in cultured mammalian cells. One of the cell systems used most often for radiation transformation studies is mouse embryonic cells (C3H10T1/2), which are easy to culture and give good quantitative dose-response curves. Relative biological effectiveness (RBE) for heavy ions with various energies and linear energy transfer (LET) have been obtained with this cell system. Similar RBE and LET relationship was observed by investigators for other cell systems. In addition to RBE measurements, fundamental questions on repair of sub- and potential oncogenic lesions, direct and indirect effect, primary target and lesion, the importance of cell-cell interaction and the role of oncogenes and tumor suppressor genes in radiogenic carcinogenesis have been studied, and interesting results have been found. Recently several human epithelial cell systems have been developed, and ionizing radiation have been shown to transform these cells. Oncogenic transformation of these cells, however, requires a long expression time and/or multiple radiation exposures. Limited experimental data indicate high-LET heavy ions can be more effective than low-LET radiation in inducing cell transformation. Cytogenetic and molecular analyses can be performed with cloned transformants to provide insights into basic genetic

  12. Prodigious degassing of a billion years of accumulated radiogenic helium at Yellowstone.

    Lowenstern, J B; Evans, W C; Bergfeld, D; Hunt, A G


    Helium is used as a critical tracer throughout the Earth sciences, where its relatively simple isotopic systematics is used to trace degassing from the mantle, to date groundwater and to time the rise of continents. The hydrothermal system at Yellowstone National Park is famous for its high helium-3/helium-4 isotope ratio, commonly cited as evidence for a deep mantle source for the Yellowstone hotspot. However, much of the helium emitted from this region is actually radiogenic helium-4 produced within the crust by α-decay of uranium and thorium. Here we show, by combining gas emission rates with chemistry and isotopic analyses, that crustal helium-4 emission rates from Yellowstone exceed (by orders of magnitude) any conceivable rate of generation within the crust. It seems that helium has accumulated for (at least) many hundreds of millions of years in Archaean (more than 2.5 billion years old) cratonic rocks beneath Yellowstone, only to be liberated over the past two million years by intense crustal metamorphism induced by the Yellowstone hotspot. Our results demonstrate the extremes in variability of crustal helium efflux on geologic timescales and imply crustal-scale open-system behaviour of helium in tectonically and magmatically active regions.

  13. Sr-O isotope systematics in the Campi Flegrei magma systems

    Wörner, Gerhard; Iovine, Raffaella; Carmine Mazzeo, Fabio; D'Antonio, Massimo; Arienzo, Ilenia; Civetta, Lucia; Orsi, Giovanni


    Combined radiogenic Sr- and stable O-isotopes are a powerful tool to distinguish between (a) contamination of mantle magma sources by fluids and subducted sediment and (b) assimilation of magmas during ascent through the crust. Advance in laser fluorination mass spectrometry permits to measure small samples and single mineral grains. This allows to directly link Sr- and O-isotope measurements practically for the same sample material. Although isotopic heterogeneity remains a problem even at this level, this approach avoids problems of weathering and mineral-melt disequilibria. We analysed mineral separates (feldspar, Fe-cpx, Mg-cpx, magnetite, olivine) from 37 samples covering the stratigraphic sequence of the Campi Flegrei volcanic field: Pre-Campanian Ignimbrite (Pre CI; >39.28 ka), Campanian Ignimbrite (CI; 39.28 ka), Post Campanian Ignimbrite/Pre Neapolitan Yellow Tuff (Post CI/pre NYT; 14.90 ka), Neapolitan Yellow Tuff (NYT; 14.90 ka), and Post-Neapolitan Yellow Tuff (Post NYT; 12.8 ka-1538 A.D.) deposits. Sr isotopic compositions were determined using standard cation-exchange methods on separated hand-picked feldspar, clinopyroxene and olivine phenocrysts (~300mg) and on whole rocks, in case of not enough amount of crystals. By infrared laser fluorination was, instead, measured the oxygen isotopic composition of ~0.3 mg of hand-picked phenocrysts. Recalculating measured mineral O-isotope values to magmatic values to account for mineral-melt 18O/16O-fractionation at various SiO2-contens of the melt should provide a data set that better constrains magma isotope compositions and magma sources. Sr-isotopes span a range from 0.7069 to 0.7082 that exceed the variations in the bulk rock samples (0.7071-0.7081). However, these ranges vary significantly between eruptive periods. For example the Sr-isotope variation in the Neapolitan Yellow Tuff is only between 0.70750 and 0.70754 for minerals and whole rocks. Similarly, recalculated δ18O-melt values show a large

  14. Partial radiogenic heat model for Earth revealed by geoneutrino measurements

    Kamland Collaboration; Gando, A.; Gando, Y.; Ichimura, K.; Ikeda, H.; Inoue, K.; Kibe, Y.; Kishimoto, Y.; Koga, M.; Minekawa, Y.; Mitsui, T.; Morikawa, T.; Nagai, N.; Nakajima, K.; Nakamura, K.; Narita, K.; Shimizu, I.; Shimizu, Y.; Shirai, J.; Suekane, F.; Suzuki, A.; Takahashi, H.; Takahashi, N.; Takemoto, Y.; Tamae, K.; Watanabe, H.; Xu, B. D.; Yabumoto, H.; Yoshida, H.; Yoshida, S.; Enomoto, S.; Kozlov, A.; Murayama, H.; Grant, C.; Keefer, G.; Piepke, A.; Banks, T. I.; Bloxham, T.; Detwiler, J. A.; Freedman, S. J.; Fujikawa, B. K.; Han, K.; Kadel, R.; O'Donnell, T.; Steiner, H. M.; Dwyer, D. A.; McKeown, R. D.; Zhang, C.; Berger, B. E.; Lane, C. E.; Maricic, J.; Miletic, T.; Batygov, M.; Learned, J. G.; Matsuno, S.; Sakai, M.; Horton-Smith, G. A.; Downum, K. E.; Gratta, G.; Tolich, K.; Efremenko, Y.; Perevozchikov, O.; Karwowski, H. J.; Markoff, D. M.; Tornow, W.; Heeger, K. M.; Decowski, M. P.


    The Earth has cooled since its formation, yet the decay of radiogenic isotopes, and in particular uranium, thorium and potassium, in the planet's interior provides a continuing heat source. The current total heat flux from the Earth to space is 44.2+/-1.0TW, but the relative contributions from residual primordial heat and radiogenic decay remain uncertain. However, radiogenic decay can be estimated from the flux of geoneutrinos, electrically neutral particles that are emitted during radioactive decay and can pass through the Earth virtually unaffected. Here we combine precise measurements of the geoneutrino flux from the Kamioka Liquid-Scintillator Antineutrino Detector, Japan, with existing measurements from the Borexino detector, Italy. We find that decay of uranium-238 and thorium-232 together contribute TW to Earth's heat flux. The neutrinos emitted from the decay of potassium-40 are below the limits of detection in our experiments, but are known to contribute 4TW. Taken together, our observations indicate that heat from radioactive decay contributes about half of Earth's total heat flux. We therefore conclude that Earth's primordial heat supply has not yet been exhausted.

  15. Pb isotopes during mingling and melting

    Waight, Tod Earle; Lesher, Charles E.


    Pb isotopic data are presented for hybrid rocks formed by mingling between mantle-derived tholeiitic magma of the Eocene Miki Fjord macrodike (East Greenland) and melt derived from the adjacent Precambrian basement. Bulk mixing and AFC processes between end-members readily identified in the field...... fail to model the Pb isotope systematics. Selective contamination during diffusional exchange, which can explain the complex Sr and Nd isotope compositions of the hybrid rocks (Blichert-Toft et al., 1992), cannot fully account for the variability of the Pb isotopic data using the identified crustal end......-members. The crustal anatectic end-member, although similar in Sr and Nd isotope composition, has a markedly different Pb isotopic composition than its source gneiss. The differences are consistent with preferential incorporation of radiogenic Pb from accessory phases such as metamict zircon or loosely-bound Pb from...

  16. Rb-Sr and Sm-Nd Isotope Systematics of Shergottite NWA 856: Crystallization Age and Implications for Alteration of Hot Desert SNC Meteorites

    Brandon, A. D.; Nyquist, L. E.; Shih, C.-Y.; Wiesmann, H.


    Nakhlite NWA 998 was discovered in Algeria in 2001, and is unique among the six known members of this group of Martian meteorites in containing significant modal orthopyroxene. Initial petrologic and isotopic data were reported by Irving et al. This 456 gram stone consists mainly of sub-calcic augite with subordinate olivine and minor orthopyroxene, titanomagnetite, pyrrhotite, chlorapatite, and intercumulus An(sub 35) plagioclase. We report here preliminary results of radiogenic isotopic analyses conducted on fragmental material from the main mass.

  17. C, O, Sr and Nd isotope systematics of carbonates of Papaghni sub-basin, Andhra Pradesh, India: Implications for genesis of carbonate-hosted stratiform uranium mineralisation and geodynamic evolution of the Cuddapah basin

    Absar, Nurul; Nizamudheen, B. M.; Augustine, Sminto; Managave, Shreyas; Balakrishnan, S.


    The Cuddapah basin (CB) is one of a series of Proterozoic basins that overlie the Archaean cratons of India, and contains a unique stratiform carbonate-hosted uranium mineralisation. In the present work, we discuss stable (C, O) and radiogenic (Nd, Sr) isotope systematics of carbonates of the Papaghni sub-basin in order to understand uranium ore forming processes and geodynamic evolution of the CB. Uranium mineralised dolomites (UMDs) of the basal Vempalle Formation show a significantly lighter (~ 1.5‰) C-isotope signature compared to that of open-marine stromatolitic sub-tidal facies, suggesting input of isotopically lighter carbon through in situ remineralisation of organic matter (OM). This implies deposition in a hydrologically-restricted, redox-stratified lagoonal basin wherein exchange with open oceanic dissolved inorganic carbon (DIC) was limited. Persistent bottom water anoxia was created and maintained through consumption of dissolved oxygen (DO) by decaying OM produced in oxidised surface water zone. Significantly more radiogenic εNd(t) of UMD (- 6.31 ± 0.54) compared to that of Dharwar upper crust (- 8.64 ± 3.11) indicates that dissolved constituents did not originate from the Dharwar craton, rather were derived from more juvenile exotic sources - possibly from a continental arc. Dissolved uranyl ions (U+ 6) were introduced to the basin through fluvial run-off and were reduced to immobile uranous ions (U+ 4) at the redox interface resulting in precipitation of pitchblende and coffinite. Carbonate horizons of upper Vempalle Formation and Tadpatri Formation show progressively more radiogenic Nd isotope compositions signifying increased juvenile arc contribution to the Papaghni sub-basin through time, which is also corroborated by the presence of younger zircons (1923 ± 22 Ma) in Pulivendla quartzites. We propose that the Papaghni sub-basin opened as a back-arc extensional basin at ~ 2 Ga as a result of westerly-directed subduction of oceanic crust

  18. Endogenous opiates mediate radiogenic behavioral change

    Mickley, G.A.; Stevens, K.E.; White, G.A.; Gibbs, G.L.


    Exposure of C57BL/6J mice to ionizing radiation caused stereotypical locomotor hyperactivity similar to that produced by morphine. Naloxone administration prevented this radiation-induced behavioral activation. These results support the hypothesis that endorphins are involved in some aspects of radiogenic behavioral change.

  19. Triple oxygen isotope systematics of structurally bonded water in gypsum

    Herwartz, Daniel; Surma, Jakub; Voigt, Claudia; Assonov, Sergey; Staubwasser, Michael


    The triple oxygen isotopic composition of gypsum mother water (gmw) is recorded in structurally bonded water in gypsum (gsbw). Respective fractionation factors have been determined experimentally for 18O/16O and 17O/16O. By taking previous experiments into account we suggest using 18αgsbw-gmw = 1.0037; 17αgsbw-gmw = 1.00195 and θgsbw-gmw = 0.5285 as fractionation factors in triple oxygen isotope space. Recent gypsum was sampled from a series of 10 ponds located in the Salar de Llamara in the Atacama Desert, Chile. Total dissolved solids (TDS) in these ponds show a gradual increase from 23 g/l to 182 g/l that is accompanied by an increase in pond water 18O/16O. Gsbw falls on a parallel curve to the ambient water from the saline ponds. The offset is mainly due to the equilibrium fractionation between gsbw and gmw. However, gsbw represents a time integrated signal biased towards times of strong evaporation, hence the estimated gmw comprises elevated 18O/16O compositions when compared to pond water samples taken on site. Gypsum precipitation is associated with algae mats in the ponds with lower salinity. No evidence for respective vital effects on the triple oxygen isotopic composition of gypsum hydration water is observed, nor are such effects expected. In principle, the array of δ18Ogsbw vs. 17Oexcess can be used to: (1) provide information on the degree of evaporation during gypsum formation; (2) estimate pristine meteoric water compositions; and (3) estimate local relative humidity which is the controlling parameter of the slope of the array for simple hydrological situations. In our case study, local mining activities may have decreased deep groundwater recharge, causing a recent change of the local hydrology.

  20. Helium isotopic systematics of oceanic islands and mantle heterogeneity

    Kurz, M.D.; Jenkins, W.J. (Woods Hole Oceanographic Institution, MA (USA)); Hart, S.R. (Massachusetts Inst. of Tech., Cambridge (USA). Dept. of Earth and Planetary Sciences)


    The results of helium isotopic analyses in basaltic phenocrysts from the islands of Gough and Tristan da Cunha are reported which seem to indicate that the mantle beneath these islands are not primitive or undepleted relative to mid-ocean ridge basalt (MORB). New analyses from Loihi Seamount are also reported which do indicate a more primitive source. When these data are combined with values for MORBs previously obtained and plotted with respect to /sup 87/Sr//sup 86/Sr, the observed trends offer insight into the different source regions for oceanic island basalts and the nature of mantle heterogeneity.

  1. Radiogenic transformation of human mammary epithelial cells in vitro

    Yang, T. C.; Georgy, K. A.; Tavakoli, A.; Craise, L. M.; Durante, M.


    Cancer induction by space radiations is a major concern for manned space exploration. Accurate assessment of radiation risk at low doses requires basic understanding of mechanism(s) of radiation carcinogenesis. For determining the oncogenic effects of ionizing radiation in human epithelial cells, we transformed a mammary epithelial cell line (185B5), which was immortalized by benzo(a)pyrene, with energetic heavy ions and obtained several transformed clones. These transformed cells showed growth properties on Matrigel similar to human mammary tumor cells. To better understand the mechanisms of radiogenic transformation of human cells, we systematically examined the alterations in chromosomes and cancer genes. Among 16 autosomes examined for translocations, by using fluorescence in situ hybridization (FISH) technique, chromosomes 3, 12, 13, 15, 16, and 18 appeared to be normal in transformed cells. Chromosomes 1, 4, 6, 8, and 17 in transformed cells, however, showed patterns different from those in nontransformed cells. Southern blot analyses indicated no detectable alterations in myc, ras, Rb, or p53 genes. Further studies of chromosome 17 by using in situ hybridization with unique sequence p53 gene probe and a centromere probe showed no loss of p53 gene in transformed cells. Experimental results from cell fusion studies indicated that the transforming gene(s) is recessive. The role of genomic instability and tumor suppressor gene(s) in radiogenic transformation of human breast cells remains to be identified.


    A. Т. Gubin


    Full Text Available Mathematical ratios were established according to the description of the calculation procedure for the values of the nominal risk coefficient given in the ICRP Recommendations 2007. It is shown that the lifetime radiogenic risk is a linear functional from the distribution of the dose in time with a multiplier descending with age. As a consequence, application of the nominal risk coefficient in the risk calculations is justified in the case when prolonged exposure is practically evenly distributed in time, and gives a significant deviation at a single exposure. When using the additive model of radiogenic risk proposed in the UNSCEAR Report 2006 for solid cancers, this factor is almost linearly decreasing with the age, which is convenient for its practical application.

  3. Current status of tumor radiogenic therapy

    Feng-Ling Min; Hong Zhang; Wen-Jian Li


    Although tumor gene therapy falls behind its clinical use, the combination of irradiation and gene therapy is full ofpromise in cancer therapy based on traditional radiotherapy, chemotherapy and surgery. We have termed it as radiogenic therapy. This review focuses on the following aspects of radiogenic therapy in recent years: improvement of gene transfer efficiency by irradiation, radiotherapy combined with cytokine gene delivery or enhancement of the immunity of tumor cells by transgene, direct stimulation by radiation toproduce cytotoxic agents, increase of tumor cell radiosensitivity in gene therapy by controlling the radiosensitivity genes and adjusting the fraction dose and interval of radiation so as to achieve the optimum antitumor effect while reducing the normal tissue damage, radioprotective gene therapy enhancing radiation tumor killing effect while protecting the normal tissue and organs with transgene using transfer vectors.

  4. Radiogenic lead from poly-metallic thorium ores as a valuable material for advanced nuclear facilities

    Kulikov, Gennady G.; Apse, Vladimir A.; Kulikov, Evgeny G.; Kozhahmet, Bauyrzhan K.; Shkodin, Alexey O.; Shmelev, Anatoly N.


    Main purpose of the study is assessing reasonability for recovery, production and application of radiogenic lead as a coolant, neutron moderator and neutron reflector in advanced fast reactors and accelerator-driven systems (ADS). The following results were obtained: 1. Radiogenic lead with high content of isotope {sup 208}Pb can be extracted from thorium or mixed thorium-uranium ores because {sup 208}Pb is a final product of {sup 232}Th natural decay chain. 2. The use of radiogenic lead with high {sup 208}Pb content in advanced fast reactors and ADS makes it possible to improve significantly their neutron-physical and thermal-hydraulic parameters. 3. The use of radiogenic lead with high {sup 208}Pb content in advanced fast reactors as a coolant opens the possibilities for more intense fuel breeding and for application of well-known oxide fuel instead of the promising but not tested enough nitride fuel under the same safety parameters. 4. The use of radiogenic lead with high {sup 208}Pb content in advanced fast reactors as a neutron reflector opens a possibility for substantial elongation of prompt neutron lifetime. As a result, chain fission reaction in the reactor core could be slowed down, and the reactor operation could become safer. 5. The use of radiogenic lead with high {sup 208}Pb content in ADS as a coolant can upgrade substantially the level of neutron flux in the ADS blanket. Thus, favorable conditions could be formed in the ADS blanket for effective transmutation of radioactive wastes with low cross-sections of radiative neutron capture.

  5. Pb-, Sr- and Nd-Isotopic systematics and chemical characteristics of cenozoic basalts, Eastern China

    Peng, Z.C.; Zartman, R.E.; Futa, K.; Chen, D.G.


    Forty-eight Paleogene, Neogene and Quaternary basaltic rocks from northeastern and east-central China have been analyzed for major-element composition, selected trace-element contents, and Pb, Sr and Nd isotopic systematics. The study area lies entirely within the marginal Pacific tectonic domain. Proceeding east to west from the continental margin to the interior, the basalts reveal an isotopic transition in mantle source material and/or degree of crustal interaction. In the east, many of the rocks are found to merge both chemically and isotopically with those previously reported from the Japanese and Taiwan island-arc terrains. In the west, clear evidence exists for component(s) of Late Archean continental lithosphere to be present in some samples. A major crustal structure, the Tan-Lu fault, marks the approximate boundary between continental margin and interior isotopic behaviors. Although the isotopic signature of the western basalts has characteristics of lower-crustal contamination, a subcrustal lithosphere, i.e. an attached mantle keel, is probably more likely to be the major contributor of their continental "flavor". The transition from continental margin to interior is very pronounced for Pb isotopes, although Sr and Nd isotopes also combine to yield correlated patterns that deviate strikingly from the mid-ocean ridge basalt (MORB) and oceanic-island trends. The most distinctive chemical attribute of this continental lithosphere component is its diminished U Pb as reflected in the Pb isotopic composition when compared to sources of MORB, oceanic-island and island-arc volcanic rocks. Somewhat diminished Sm Nd and elevated Rb Sr, especially in comparison to the depleted asthenospheric mantle, are also apparent from the Nd- and Sr-isotopic ratios. ?? 1986.

  6. Constraints from Li isotope systematics on subduction recycling, arc magmatism, and continent growth: An overview

    Leeman, W. P.; Lee, C. A.; Chan, L. H.


    Great expectations that Li isotopic systematics can uniquely constrain many fluid-mitigated geologic processes have met with mixed success for a variety of reasons. On a local scale (some volcanic arc segments) Li composition can be highly correlated with other geochemical tracers of subduction fluids whereas, globally, such correlations tend to be disappointingly poor. The utility of Li isotopes as a tracer is limited in part by extensive overlap between mantle and subduction inputs, by limited understanding of equilibrium isotopic fractionation effects, and by apparent departures from equilibrium behavior. On the other hand, Li elemental systematics provide important constraints on global recycling processes because major litho-tectonic reservoirs have distinctive enrichments or depletions with respect to Nb or other HFSEs. Such chemical fractionations can be understood in terms of differential solubility of these elements in aqueous fluids vs. silicate melts, as well as the roles of weathering, dehydration, metamorphic or melting processes. For example, arc lavas are are systematically enriched in Li compared to those from other settings and typically have Li/Nb greater than BSE (consistent with addition of Li-rich fluids to their sources). In contrast, bulk continental crust and orogenic granitoids tend to have lower Li/Nb than BSE or arc lavas. Moreover, mass balance implies that the residual mantle (DM) produced by segregation of crust has higher Li/Nb than BSE. However, if continental crust is ultimately derived by subduction related magmatism, high Li/Nb would be expected for the crust and low Li/Nb for the upper mantle. This interesting conundrum is easiest explained in terms of selective Li removal from crustal protolith rocks via chemical weathering and erosion, which also is consistent with Li isotopic compositions of crust, mantle and seawater reservoirs. Thus, Li elemental and isotopic systematics (and relevant proxies) provide complementary

  7. Systematic measurement of beta-decay half-lives of short-lived isotopes

    Hirose, T.; Yamamoto, H.; Kawade, K. [Nagoya Univ. (Japan); Iida, T.; Takahashi, A.; Kasugai, Y.; Ikeda, Y.


    We have measured the half-lives of short-lived isotopes for past decade and deduced the half-lives of 6 isotopes further. These results demonstrated that most of the literature values shorter than 10 min systematically deviated from our measurement ones. The cause seems to be that a large number of the previous half-life studies were performed with scintillation counters before 1970 and they had a difficulty in distinguishing the interest {gamma}-ray from the contamination and correcting for pile-up and dead-time losses. Moreover, the deviated data found to be quoted for evaluation. (author)

  8. Carbon and nitrogen isotope systematics in diamond: Different sensitivities to isotopic fractionation or a decoupled origin?

    Hogberg, K.; Stachel, T.; Stern, R. A.


    Using stable isotope data obtained on multiple aliquots of diamonds from worldwide sources, it has been argued that carbon and nitrogen in diamond are decoupled. Here we re-investigate the carbon-nitrogen relationship based on the most comprehensive microbeam data set to date of stable isotopes and nitrogen concentrations in diamonds (n = 94) from a single locality. Our diamond samples, derived from two kimberlites in the Chidliak Field (NE Canada), show large variability in δ13C (- 28.4 ‰ to - 1.1‰, mode at - 5.8‰), δ15N (- 5.8 to + 18.8‰, mode at - 3.0‰) and nitrogen contents ([N]; 3800 to less than 1 at.ppm). In combination, cathodoluminescence imaging and microbeam analyses reveal that the diamonds grew from multiple fluid pulses, with at least one major hiatus documented in some samples that was associated with a resorption event and an abrupt change from low δ13C and [N] to mantle-like δ13C and high [N]. Overall, δ13C appears to be uncorrelated to δ15N and [N] on both the inter- and intra-diamond levels. Co-variations of δ15N-log[N], however, result in at least two parallel, negatively correlated linear arrays, which are also present on the level of the individual diamonds falling on these two trends. These arrays emerge from the two principal data clusters, are characterized by slightly negative and slightly positive δ15N (about - 3 and + 2‰, respectively) and variable but overall high [N]. Using published values for the diamond-fluid nitrogen isotope fractionation factor and nitrogen partition coefficient, these trends are perfectly reproduced by a Rayleigh fractionation model. Overall, three key elements are identified in the formation of the diamond suite studied: (1.) a low δ13C and low [N] component that possibly is directly associated with an eclogitic diamond substrate or introduced during an early stage fluid event. (2.) Repeated influx of a variably nitrogen-rich mantle fluid (mildly negative δ13C and δ15N). (3.) In waning

  9. Oxygen isotope equilibration systematics between quartz and water

    Matthews, A. (Hebrew Univ., Jerusalem, Israel); Beckinsale, R.D.


    The /sup 18/O//sup 16/O fractionation accompanying the hydrothermal crystallization of quartz from silicic acid at 265/sup 0/ to 465/sup 0/C has been studied in order to assess the influences of (a) rate of quartz formation, (b) the nature of the reaction mechanism, and (c) temperature. At 360/sup 0/ and 465/sup 0/C, there are no indications of rate effects influencing isotope partitioning, but at 265/sup 0/C (where fractionation factors show an unusally large scatter) the evidence is inconclusive in this respect. All reaction appears to occur through solution-precipitation processes, with the intermediate phases, cristobalite and silica K, giving identical fractionation factors (within experimental errors) to quartz samples formed at the same temperature. The temperature-dependence of fractionation in the range 265/sup 0/ to 465/sup 0/C is given by the equation 10/sup 3/ ln ..cap alpha..(SiO/sub 2/--H/sub 2/O) = 3.05 x 10/sup 6/T/sup -2/ - 2.09. The data are in good agreement with other experimental calibrations of the quartz-water fractionation.

  10. Carbon and Nitrogen Isotope Systematics in a Sector-Zoned Diamond from the Mir Kimberlite, Yakutia

    Hauri, E.; Bulanova, G.; Pearson, G.; Griffin, B.


    A single Yakutian octahedral diamond, displaying striking cubic and octahedral growth sectors surrounded by an octahedral rim, has been analysed for carbon and nitrogen isotopic compositions by SIMS and for nitrogen concentration (by SIMS and FTIR) and nitrogen aggregation state (FTIR). A graphite "seed" inclusion identified within the diamond, enriched in K, Ca, Ti, Rb and Sr, provides evidence that the diamond may have grown from a carbonate melt/fluid interacting with upper mantle rocks. Carbon and nitrogen isotope compositions become progressively heavier from the core region (d13C = -7 to -5 and d15N= -3) towards the inner rim zones (d13C = -3 and d15N = +8.9 to +5) of the diamond. Nitrogen concentration and aggregation measurements show corresponding decreases that generally correlate with the isotopic variations. These systematic variations within the core and intermediate regions of the diamond are consistent with their formation during diamond growth from CO2-rich fluids as a continuous event, accompanied by slight progressive isotopic fractionation of carbon and nitrogen. However, the observed isotope and nitrogen abundance trends are not those predicted from thermodynamic modelling of fluid-solid equilibria in a C-N-O-H-bearing system due to changes in parameters such as fO2 (Deines, 1980; Deines et al 1989). Within the finely-zoned octahedral rim region, non-systematic variations in nitrogen abundance, nitrogen aggregation, and nitrogen and carbon isotope ratios were observed. Several interpretations are given for this phenomenon, including kinetic effects during growth of the diamond rim under different conditions from those of the core-intermediate regions, or rapidly changing fluid sources during the growth. No fractionation of nitrogen isotopes between cubic and octahedral growth zones was identified within the studied diamond, in contrast with the fractionation phenomena found in synthetic diamonds of mixed growth. Our results illustrate the

  11. Iron Isotope Systematics of the Bushveld Complex, South Africa: Initial Results

    Stausberg, N.; Lesher, C. E.; Hoffmann-Barfod, G.; Glessner, J. J.; Tegner, C.


    Iron isotopes show systematic changes in igneous rocks that have been ascribed to fractional crystallization, partial melting, as well as, diffusion effects. Layered mafic intrusions, such as the Paleoproterozoic Bushveld Igneous Complex, are ideally suited to investigate stable isotope fractionation arising principally by fractional crystallization. The upper 2.1km of the Bushveld Complex (Upper and Upper Main Zone, UUMZ) crystallized from a basaltic magma produced by a major recharge event, building up a sequence of tholeiitic, Fe-rich, gabbroic cumulate rocks that display systematic variations in mineralogy and mineral compositions consistent with fractional crystallization. Within this sequence, magnetite joins the liquidus assemblage at ˜260m, followed by olivine at 460m and apatite at 1000m. Here, we present iron isotope measurements of bulk cumulate rocks from the Bierkraal drill core of UUMZ of the western limb. Iron was chemically separated from its matrix and analyzed for δ56Fe (relative to IRMM- 014) with a Nu plasma MC-ICPMS at the University of California, Davis, using (pseudo-) high resolution and sample-standard bracketing. The δ56Fe values for Bushveld cumulates span a range from 0.04‰ to 0.36‰, and systematically correlate with the relative abundance of pyroxene + olivine, magnetite and plagioclase. Notably, the highest δ56Fe values are found in plagioclase-rich cumulates that formed prior to magnetite crystallization. δ56Fe is also high in magnetite-rich cumulates at the onset of magnetite crystallization, while subsequent cumulates exhibit lower and variable δ56Fe principally reflecting fractionation of and modal variations in magnetite, pyroxene and fayalitic olivine. The overall relationships for δ56Fe are consistent with positive mineral - liquid Fe isotope fractionation factors for magnetite and plagioclase, and negative to near zero values for pyroxene and olivine. These initial results are being integrated into a forward model of

  12. Radiogenic neoplasia in thyroid and mammary clonogens

    Clifton, K.H.


    We have developed rat thyroid and mammary clonogen transplantation systems for the study of radiogenic cancer induction at the target cell level in vivo. The epithelial cell populations of both glands contain small subpopulations of cells which are capable of giving rise to monoclonal glandular structures when transplanted and stimulated with appropriate hormones. Previous results indicated that these clonogens are the precursor cells of radiogenic cancer, and that initiation, is common event at the clonegenic cell level. Detailed information on the physiologic control of clonogen proliferation, differentiation, and total numbers is thus essential to an understanding of the carcinogenic process. We report here studies on investigations on the relationships between grafted thyroid cell number and the rapidity and degree of reestablishment of the thyroid-hypothalamus-pituitary feedback axis in thyroidectomized rats maintained on a normal diet or an iodine deficient diet; studies of the persistence of, and the differentiation potential and functional characteristics of, the TSH-(thyrotropin-) responsive sub- population of clonogens during goitrogenesis, the plateau-phase of goiter growth, and goiter involution; studies of changes in the size of the clonogen sub-population during goitrogenesis, goiter involution and the response to goitrogen rechallenge; and a large carcinogenesis experiment on the nature of the grafted thyroid cell number-dependent suppression of promotion/progression to neoplasia in grafts of radiation-initiated thyroid cells. Data from these studies will be used in the design of future carcinogenesis experiments on neoplastic initiation by high and low LET radiations and on cell interactions during the neoplastic process.

  13. Disturbed Sr and Nd Isotope Systematics in Zircons With Concordant SHRIMP U-Pb Ages

    Weaver, K. L.; Bennett, V. C.; Depaolo, D. J.; Mundil, R.


    Little is known about the Sr- and Nd-isotopic systematics of zircon. With slow diffusion rates and a high resistance to weathering, zircon should preserve accurate age information and initial Sr and Nd isotopic ratios. As a common accessory mineral, it could provide petrogenetic information for rocks that have been altered, weathered, or metamorphosed. We have investigated the Sm-Nd and Rb-Sr systematics of zircons from unmetamorphosed granitic rocks that have yielded concordant U-Pb SHRIMP (Sensitive High Resolution Ion Microprobe) ages and have depleted mantle signatures for Nd and Sr isotopes. Zircon populations from mantle-derived igneous rocks with ages of 0.1, 1.7, and 3.8 Ga were chosen for Sr and Nd isotopic analysis. Low concentrations (Sr, 4 to 8 ppm and Nd, 6 to 12 ppm) and small grain size necessitate the use of multigrain aliquots. Meaningful results can be obtained only if all of the zircons in the rock are a coherent population with homogeneous ages throughout and among grains. Zircon U-Pb ages were characterized using the SHRIMP RG, and trace element concentrations were measured by LA-ICPMS. The populations are homogeneous and the material ablated by the ion beam ( ˜~20 μ m spot size) shows little evidence of lead loss. Results on zircons of 100 Ma and 1700 Ma indicate that both the Rb-Sr and Sm-Nd systems have been severely disturbed. For the 1700 Ma granitic rocks from the Yavapai sequence of Arizona, zircon Sm-Nd apparent ages are ca. 1000 Ma! Leaching was used to remove contributions from adhering or included minerals, but leached residues that presumably most closely approximate the composition of the pure zircon (e.g. have high Sm/Nd) are no less disturbed than unleached samples. Despite the U-Pb SHRIMP ages indicating a closed system, the zircons have failed to preserve a reasonable age or initial isotopic composition for Sr and Nd, indicating that parts of the crystal might be severely affected by radiation damage resulting in disturbed

  14. Archean Lithosphere Beneath Arctic Canada: Lu-Hf Isotope Systematics for Kimberlite-Hosted Garnet-Peridotites From Somerset Island

    Schmidberger, S. S.; Simonetti, A.; Francis, D.; Gariepy, C.


    Knowledge of the age of lithospheric mantle underlying the continents provides valuable constraints for the timing of formation and stabilization of Archean cratons. This study reports Lu-Hf isotopic data for garnet-peridotites, and their constituent garnets, from the Nikos kimberlite (100 Ma) on Somerset Island in the Canadian Arctic obtained using a Micromass IsoProbe multicollector inductively coupled plasma mass spectrometer (MC-ICP-MS) at GEOTOP-UQAM. The low temperature peridotites (1100 C; 160-190 km) and their 176Hf/177Hf(0.1Ga) isotopic compositions (0.28265-0.28333; \\epsilonHf(0.1Ga)=-2 to +22) are less radiogenic than those of the shallow xenoliths. A Lu-Hf isochron for six peridotites yields a mid Archean age of 3.4\\pm0.3 Ga and an initial 176Hf/177Hf ratio of 0.28101\\pm24. The remaining peridotites (n=9), in contrast, are characterized by extremely high (+35) initial \\epsilonHf(3.4Ga) values, which correlate negatively with their 176Lu/177Hf ratios, suggesting addition of Hf as a result of metasomatic interaction with the host kimberlite. The garnets from the low temperature (3.4 Ga old) peridotites are characterized by high 176Lu/177Hf ratios and define an errorchron age of 1.4\\pm0.2 Ga, which may reflect re-equilibration of Hf during kimberlite magmatism.

  15. Radiogenic Lead with Dominant Content of 208Pb: New Coolant and Neutron Moderator for Innovative Nuclear Facilities

    A. N. Shmelev


    Full Text Available As a rule materials of small atomic weight (light and heavy water, graphite, and so on are used as neutron moderators and reflectors. A new very heavy atomic weight moderator is proposed—radiogenic lead consisting mainly of isotope 208Pb. It is characterized by extremely low neutron radiative capture cross-section (0.23 mbarn for thermal neutrons, i.e., less than that for graphite and deuterium and highest albedo of thermal neutrons. It is evaluated that the use of radiogenic lead makes it possible to slow down the chain fission reaction on prompt neutrons in a fast reactor. This can increase safety of the fast reactors and reduce as well requirements pertaining to the fuel fabrication technology. Radiogenic lead with high 208Pb content as a liquid-metal coolant of fast reactors helps to achieve a favorable (negative reactivity coefficient on coolant temperature. It is noteworthy that radiogenic lead with high 208Pb content may be extracted from thorium (as well as thorium-uranium ores without isotope separation. This has been confirmed experimentally by the investigations performed at San Paulo University, Brazil.

  16. Kalkkop Crater, Cape Province, South Africa: Confirmation of impact origin using osmium isotope systematics

    Koeberl, Christian; Reimold, Wolf Uwe; Shirey, Steven B.; le Roux, F. G.


    The Kalkkop structure, a circular depression with a diameter of 640 m, is situated in the Eastern Cape Province, South Africa. In 1992, a bore hole was drilled in the center of the crater to a depth of 151.8 m. To assess a possible impact origin of this structure, the abundances and isotopic ratios of osmium and rhenium were measured in breccias and in sandstones and shales derived from the basement. The basement rocks show rhenium and osmium abundances and isotopic compositions of osmium and neodymium ( 187Os /188Os = 0.61 to 0.92 and ɛNd = -6 to-7) that are typical for continental crust. One of the breccia samples shows a significantly elevated osmium content and a much lower ( 187Os /188Os ratio of about 0.215 (( 187Os /188Os ratio = 1.79 ). This ratio is much closer to meteoritic compositions than to crust, indicating the presence of about 0.05% of an extraterrestrial component in the breccia. This is the first time that osmium isotope systematics have been used to confirm the impact origin of a crater structure, and demonstrates their sensitivity for impact studies.

  17. On the valency state of radiogenic lead in zircon and its consequences

    Kramers, J.; Frei, R; Newville, M.; Kober, B.; Villa, I.; (UCopenhagen); (Universitä); (t Bern); (UC); (University of Heidelberg)


    In zircon U-Pb systematics, extreme robustness up to the temperatures of granulite facies and anatexis contrasts with apparently easy loss of radiogenic Pb at low temperatures, often without any metamorphic event being in evidence. Here we propose that this paradoxical behaviour can be understood with the hypothesis that radiogenic Pb in zircon is tetravalent. We review data and arguments in favour of this hypothesis. Diffusion profiles calculated for Pb{sup 2+} in a 25 {micro}m radius zircon xenocryst in a melt at 1000 C, combined with the incompatibility of Pb{sup 2+}, or for a zircon core inside a younger zircon rim at this temperature, show age effects that should have been observed in SIMS dating. Further, in zircon evaporation as well as in leaching experiments, common Pb is generally released preferentially to radiogenic Pb. After removal of less radiogenic Pb, the evaporation record generally shows pure radiogenic Pb during the final evaporation steps. The distribution of residual Pb in a leached titanite, revealed by PIXE, is similar to that of Ti. Lastly, XANES spectra of a 1 Ga old titanite (predominantly radiogenic Pb) and an Alpine one (predominantly common Pb) are significantly different, although the former does not resemble that of PbO{sub 2}. The arguments why radiogenic Pb should be tetravalent are based on analogies with studies relating to the tetravalent state of {sup 234}Th and the hexavalent state of {sup 234}U, which show that {alpha}-recoil in silicates generates a strongly oxidizing environment at the site where the recoiling nucleus comes to rest. Further, a zircon grain, being small, should remain highly oxidizing in its interior by the constant loss of {beta}-particles, maintaining the 4+ state of radiogenic Pb. From its effective ion radius, similar to that of Zr{sup 4+}, and its charge, Pb{sup 4+} has to be compatible in the zircon lattice. Also, by analogy with U{sup 4+}, Th{sup 4+} and Hf{sup 4+}, its diffusivity should be several

  18. A systematic regional trend in helium isotopes across the northernbasin and range province, Western North America

    Kennedy, B. Mack; van Soest, Matthijs C.


    An extensive study of helium isotopes in fluids collectedfrom surface springs, fumaroles and wells across the northern Basin andRange Province reveals a systematic trend of decreasing 3He/4He ratiosfrom west to east. The western margin of the Basin and Range ischaracterized by mantle-like ratios (6-8 Ra) associated with active orrecently active crustal magma systems (e.g., Coso, Long Valley,Steamboat, and the Cascade volcanic complex). Moving towards the east,the ratios decline systematically to a background value of ~;0.1 Ra. Theregional trend is consistent with extensive mantle melting concentratedalong the western margin and is coincident with an east-to-west increasein the magnitude of northwest strain. The increase in shear strainenhances crustal permeability resulting in high vertical fluid flow ratesthat preserve the high helium isotope ratios at the surface. Superimposedon the regional trend are "helium spikes," local anomalies in the heliumisotope composition. These "spikes" reflect either local zones of mantlemelting or locally enhanced crustal permeability. In the case of theDixie Valley hydrothermal system, it appears to be a combination ofboth.

  19. Release of radiogenic noble gases as a new signal of rock deformation

    Bauer, Stephen J.; Gardner, W. Payton; Lee, Hyunwoo


    In this study we investigate the release of radiogenic noble gas isotopes during mechanical deformation. We developed an analytical system for dynamic mass spectrometry of noble gas composition and helium release rate of gas produced during mechanical deformation of rocks. Our results indicate that rocks release accumulated radiogenic helium and argon from mineral grains as they undergo deformation. We found that the release of accumulated 4He and 40Ar from rocks follows a reproducible pattern and can provide insight into the deformation process. Increased gas release can be observed before dilation, and macroscopic failure is observed during high-pressure triaxial rock deformation experiments. Accumulated radiogenic noble gases can be released due to fracturing of mineral grains during small-scale strain in Earth materials. Helium and argon are highly mobile, conservative species and could be used to provide information on changes in the state of stress and strain in Earth materials, and as an early warning signal of macroscopic failure. These results pave the way for the use of noble gases to trace and monitor rock deformation for earthquake prediction and a variety of other subsurface engineering projects.

  20. Pb isotopes during crustal melting and magma mingling - A cautionary tale from the Miki Fjord macrodike, central east Greenland

    Waight, Tod Earle; Lesher, Charles


    Pb isotopic data are presented for hybrid rocks formed by mingling between mantle-derived tholeiitic magma of the Eocene Miki Fjord macrodike (East Greenland) and melt derived from the adjacent Precambrian basement. Bulk mixing and AFC processes between end-members readily identified in the field...... fail to model the Pb isotope systematics. Selective contamination during diffusional exchange, which can explain the complex Sr and Nd isotope compositions of the hybrid rocks (Blichert-Toft et al., 1992), cannot fully account for the variability of the Pb isotopic data using the identified crustal end......-members. The crustal anatectic end-member, although similar in Sr and Nd isotope composition, has a markedly different Pb isotopic composition than its source gneiss. The differences are consistent with preferential incorporation of radiogenic Pb from accessory phases such as metamict zircon or loosely-bound Pb from...

  1. Pb isotopes during crustal melting and magma mingling - A cautionary tale from the Miki Fjord macrodike, central east Greenland

    Waight, Tod Earle; Lesher, Charles


    Pb isotopic data are presented for hybrid rocks formed by mingling between mantle-derived tholeiitic magma of the Eocene Miki Fjord macrodike (East Greenland) and melt derived from the adjacent Precambrian basement. Bulk mixing and AFC processes between end-members readily identified in the field...... fail to model the Pb isotope systematics. Selective contamination during diffusional exchange, which can explain the complex Sr and Nd isotope compositions of the hybrid rocks (Blichert-Toft et al., 1992), cannot fully account for the variability of the Pb isotopic data using the identified crustal end......-members. The crustal anatectic end-member, although similar in Sr and Nd isotope composition, has a markedly different Pb isotopic composition than its source gneiss. The differences are consistent with preferential incorporation of radiogenic Pb from accessory phases such as metamict zircon or loosely-bound Pb from...

  2. Hydrogen and carbon isotope systematics in hydrogenotrophic methanogenesis under H2-limited and H2-enriched conditions: implications for the origin of methane and its isotopic diagnosis

    Okumura, Tomoyo; Kawagucci, Shinsuke; Saito, Yayoi; Matsui, Yohei; Takai, Ken; Imachi, Hiroyuki


    Hydrogen and carbon isotope systematics of H2O-H2-CO2-CH4 in hydrogenotrophic methanogenesis and their relation to H2 availability were investigated. Two H2-syntrophic cocultures of fermentatively hydrogenogenic bacteria and hydrogenotrophic methanogens under conditions of pure cultures of hydrogenotrophic methanogens under conditions of 105 Pa-H2 were tested. Carbon isotope fractionation between CH4 and CO2 during hydrogenotrophic methanogenesis was correlated with pH2, as indicated in previous studies. The hydrogen isotope ratio of CH4 produced during rapid growth of the thermophilic methanogen Methanothermococcus okinawensis under high pH2 conditions ( 105 Pa) was affected by the isotopic composition of H2, as concluded in a previous study of Methanothermobacter thermautotrophicus. This " {δ D}_{{H}_2} effect" is a possible cause of the diversity of previously reported values for hydrogen isotope fractionation between CH4 and H2O examined in H2-enriched culture experiments. Hydrogen isotope fractionation between CH4 and H2O, defined by (1000 + {δ D}_{{CH}_4} )/(1000 + {δ D}_{{H}_2O} ), during hydrogenotrophic methanogenesis of the H2-syntrophic cocultures was in the range 0.67-0.69. The hydrogen isotope fractionation of our H2-syntrophic dataset overlaps with those obtained not only from low- pH2 experiments reported so far but also from natural samples of "young" methane reservoirs (0.66-0.74). Conversely, such hydrogen isotope fractionation is not consistent with that of "aged" methane in geological samples (≥0.79), which has been regarded as methane produced via hydrogenotrophic methanogenesis from the carbon isotope fractionation. As a possible process inducing the inconsistency in hydrogen isotope signatures between experiments and geological samples, we hypothesize that the hydrogen isotope signature of CH4 imprinted at the time of methanogenesis, as in the experiments and natural young methane, may be altered by diagenetic hydrogen isotope exchange

  3. Ce isotope systematics of island arc lavas from the Lesser Antilles

    Bellot, Nina; Boyet, Maud; Doucelance, Régis; Pin, Christian; Chauvel, Catherine; Auclair, Delphine


    The La-Ce systematics has one of the longest half-lifes (T1/2 = 292.5 Ga) of radioactive decay systems used in isotope geochemistry. Variations of the 138Ce/142Ce ratio are expected to be small and the use of Ce as isotopic tracer requires a very precise measurement. Compared to Sm-Nd studies, the La-Ce decay system can provide additional information about the nature of sediments recycled in subduction zones, because unusually large Ce anomalies relative to the neighboring rare earth elements exist in marine sediments such as fish teeth or hydrothermal deposits. Here, we present a chemical purification technique for Ce, and mass spectrometric technique to perform accurate and reproducible analyses of Ce isotopes of natural samples. We report a large set of Ce isotope data including analysis of 2 Ce reference material solutions (AMES and JMC-304), 2 rock standards (BCR-2 and BHVO-2), 2 chondrites (the carbonaceous chondrite Allende and the enstatite chondrite Sahara 97072), 4 mid-ocean ridge basalts, 30 arc lavas from the Martinique Island and 5 oceanic sediments from DSDP-site 144 drilled on the Demerara rise. The long-term, external precision obtained on the AMES reference material is 80 ppm (2 s.d., 138Ce/142Ce = 0.0225732 ± 18, n = 89). However, we note an evolution of isotopic ratios measured in static mode over the duration of this study (33 months). When the reproducibility is calculated from the AMES reference material measured during the same analytical session, it averages 40 ppm. All the 138Ce/142Ce ratios have been normalized to the AMES value of 0.0225746 (measured in session 7, 2 s.d. = 14 ppm, n = 8), a session during which the chondritic value has been defined and the peak tailing was negligible. The 138Ce/142Ce ratio measured for the JMC-304 Ce reference reagent is 0.0225706 ± 9 (2 s.d. = 38 ppm, n = 10). The analytical precision on natural samples is improved by a factor of about 4 in relation to previous studies on island arcs (Tanaka et al

  4. Radiogenic neoplasia in thyroid and mammary clonogens

    Clifton, K.H.


    We have developed rat thyroid and mammary clonogen transplantation systems for the study of radiogenic cancer induction at the target cell level in vivo. The epithelial cell populations of both glands contain small subpopulations of cells which are capable of giving rise to monoclonal glandular structures when transplanted and stimulated with appropriate hormones. During the end of the last grant year and the first half of the current grant year, we have completed analyses and summarized for publication: investigations on the relationship between grafted thyroid cell number and the rapidity and degree of reestablishment of the thyroid-hypothalamicpituitary axis in thyroidectomized rats maintained on a normal diet or an iodine deficient diet; studies of the persistence of, and the differentiation potential and functional characteristics of, the TSH- (thyrotropin-) responsive sub-population of clonogens during goitrogenesis, the plateau-phase of goiter growth, and goiter involution; studies of changes in the size of the clonogen sub-population during goitrogenesis, goiter involution and the response to goitrogen rechallenge; and the results of the large carcinogenesis experiment on the nature of the grafted thyroid cell number-dependent suppression of promotion/progression to neoplasia in grafts of radiation-initiated thyroid cells. We are testing new techniques for the culture, cytofluorescent analysis and characterization mammary epithelial cells and of clonogens in a parallel project, and plan to apply similar technology to the thyroid epithelial cells and clonogen population. Data from these studies will be used in the design of future carcinogenesis experiments on neoplastic initiation by high and low LET radiations and on cells interactions during the neoplastic process.

  5. Correlations Among Microstructure, Morphology, Chemistry, and Isotopic Systematics of Hibonite in CM Chondrites

    Han, J.; Liu, M.-C..; Keller, L. P.; Davis, A. M.


    Introduction: Hibonite is a primary refractory phase occurring in many CAIs, typically with spinel and perovskite. Our microstructural studies of CAIs from carbonaceous chondrites reveal a range of stacking defect densities and correlated non-stoichiometry in hibonite. We also conducted a series of annealing experiments, demonstrating that the Mg-Al substitution stabilized the formation of defect-structured hibonite. Here, we continue a detailed TEM analysis of hibonite-bearing inclusions from CM chondrites that have been well-characterized isotopically. We examine possible correlations of microstructure, morphology, mineralogy, and chemical and isotopic systematics of CM hibonites in order to better understand the formation history of hibonite in the early solar nebula. Methods: Fifteen hibonite-bearing inclusions from the Paris CM chondrite were analyzed using a JEOL 7600F SEM and a JEOL 8530F electron microprobe. In addition to three hibonite-bearing inclusions from the Murchison CM chondrite previously reported, we selected three inclusions from Paris, Pmt1-6, 1-9, and 1-10, representing a range of 26Al/27Al ratios and minor element concentrations for a detailed TEM study. We extracted TEM sections from hibonite grains using a FEI Quanta 3D field emission gun SEM/FIB. The sections were then examined using a JEOL 2500SE field-emission scanning TEM equipped with a Thermo-Noran thin window EDX spectrometer. Results and Discussion: A total of six hibonite-bearing inclusions, including two platy hibonite crystals (PLACs) and four spinel-hibonite inclusions (SHIBs), were studied. There are notable differences in chemical and isotopic compositions between the inclusions (Table 1), indicative of their different formation environment or timing. Our TEM observations show perfectly-ordered, stoichiometric hibonite crystals without stacking defects in two PLACs, 2-7-1 and 2-8-2, and in three SHIBs, Pmt1-6, 1-9, and 1-10. In contrast, SHIB 1-9-5 hibonite grains contain a

  6. Re-Os isotope systematics in black shales from the Lesser Himalaya: their chronology and role in the 187Os/ 188Os evolution of seawater

    Singh, Sunil K.; Trivedi, J. R.; Krishnaswami, S.


    Re and Os abundances and Os isotope systematics have been measured in a number of black shales sampled from outcrops and two underground phosphorite mines, Maldeota and Durmala, in the Lesser Himalaya. The Re and Os concentrations in these samples exhibit wide range, 0.2 to 264 ng/g and 0.02 to 13.5 ng/g, respectively, with a mean Re/Os of ˜25. The 187Os/ 188Os of these samples also show a broad range 1.02 to 11.6, with many of them far more radiogenic than the currently eroding continental crust. The black shales from the Maldeota and Durmala mines, collected a few meters above the Krol-Tal (Pc-C) boundary and occurring in the same stratigraphic horizon, yield 187Re- 187Os isochron ages of 554 ± 16 and 552 ± 22 Ma, respectively, consistent with fossil evidences and those assigned for the Pc-C boundary at various other locations. These results indicate closed system behaviour of Re and Os in these mine samples and reaffirm the validity of 187Re- 187Os pair to date organic-rich sediments. The age of these mine samples from the outer belt seems to be a few hundred millions of years younger than the preliminary Re-Os age of 839 ± 138 Ma for black shales from Theog, collected from the inner belt. These initial results lean toward the hypothesis that the inner belt sediments were deposited earlier than the outer belt; however, more analyses of black shales are needed to confirm this. The role of weathering black shales from the Himalaya in contributing to the Os isotope evolution of seawater over the past ˜25 Ma was assessed using a simple budget model for seawater Os and assuming values for Os fluxes and 187Os/ 188Os based on the available limited data on Os concentration and its 187Os/ 188Os in rivers and oceans. These calculations indicate that the required contributions from black shale weathering to account for the entire increase in oceanic 187Os/ 188Os over the past ˜16 Ma is difficult to satisfy by varying only the Os flux from HTP rivers ( 187Os/ 188Os

  7. Systematic investigation of projectile fragmentation using beams of unstable B and C isotopes

    Thies, R.; Heinz, A.; Adachi, T.; Aksyutina, Y.; Alcantara-Núñes, J.; Altstadt, S.; Alvarez-Pol, H.; Ashwood, N.; Aumann, T.; Avdeichikov, V.; Barr, M.; Beceiro-Novo, S.; Bemmerer, D.; Benlliure, J.; Bertulani, C. A.; Boretzky, K.; Borge, M. J. G.; Burgunder, G.; Camaño, M.; Caesar, C.; Casarejos, E.; Catford, W.; Cederkäll, J.; Chakraborty, S.; Chartier, M.; Chulkov, L. V.; Cortina-Gil, D.; Crespo, R.; Datta, U.; Díaz Fernández, P.; Dillmann, I.; Elekes, Z.; Enders, J.; Ershova, O.; Estradé, A.; Farinon, F.; Fraile, L. M.; Freer, M.; Freudenberger, M.; Fynbo, H. O. U.; Galaviz, D.; Geissel, H.; Gernhäuser, R.; Göbel, K.; Golubev, P.; Gonzalez Diaz, D.; Hagdahl, J.; Heftrich, T.; Heil, M.; Heine, M.; Henriques, A.; Holl, M.; Ickert, G.; Ignatov, A.; Jakobsson, B.; Johansson, H. T.; Jonson, B.; Kalantar-Nayestanaki, N.; Kanungo, R.; Knöbel, R.; Kröll, T.; Krücken, R.; Kurcewicz, J.; Kurz, N.; Labiche, M.; Langer, C.; Le Bleis, T.; Lemmon, R.; Lepyoshkina, O.; Lindberg, S.; Machado, J.; Marganiec, J.; Maroussov, V.; Mostazo, M.; Movsesyan, A.; Najafi, A.; Nilsson, T.; Nociforo, C.; Panin, V.; Paschalis, S.; Perea, A.; Petri, M.; Pietri, S.; Plag, R.; Prochazka, A.; Rahaman, A.; Rastrepina, G.; Reifarth, R.; Ribeiro, G.; Ricciardi, M. V.; Rigollet, C.; Riisager, K.; Röder, M.; Rossi, D.; Sanchez del Rio, J.; Savran, D.; Scheit, H.; Simon, H.; Sorlin, O.; Stoica, V.; Streicher, B.; Taylor, J. T.; Tengblad, O.; Terashima, S.; Togano, Y.; Uberseder, E.; Van de Walle, J.; Velho, P.; Volkov, V.; Wagner, A.; Wamers, F.; Weick, H.; Weigand, M.; Wheldon, C.; Wilson, G.; Wimmer, C.; Winfield, J. S.; Woods, P.; Yakorev, D.; Zhukov, M. V.; Zilges, A.; Zuber, K.; R3B Collaboration


    Background: Models describing nuclear fragmentation and fragmentation fission deliver important input for planning nuclear physics experiments and future radioactive ion beam facilities. These models are usually benchmarked against data from stable beam experiments. In the future, two-step fragmentation reactions with exotic nuclei as stepping stones are a promising tool for reaching the most neutron-rich nuclei, creating a need for models to describe also these reactions. Purpose: We want to extend the presently available data on fragmentation reactions towards the light exotic region on the nuclear chart. Furthermore, we want to improve the understanding of projectile fragmentation especially for unstable isotopes. Method: We have measured projectile fragments from 10,12 -18C and B-1510 isotopes colliding with a carbon target. These measurements were all performed within one experiment, which gives rise to a very consistent data set. We compare our data to model calculations. Results: One-proton removal cross sections with different final neutron numbers (1 p x n ) for relativistic 10,12 -18C and B-1510 isotopes impinging on a carbon target. Comparing model calculations to the data, we find that the epax code is not able to describe the data satisfactorily. Using abrabla07 on the other hand, we find that the average excitation energy per abraded nucleon needs to be decreased from 27 MeV to 8.1 MeV. With that decrease abrabla07 describes the data surprisingly well. Conclusions: Extending the available data towards light unstable nuclei with a consistent set of new data has allowed a systematic investigation of the role of the excitation energy induced in projectile fragmentation. Most striking is the apparent mass dependence of the average excitation energy per abraded nucleon. Nevertheless, this parameter, which has been related to final-state interactions, requires further study.

  8. Nanoscale variations in 187Os isotopic composition and HSE systematics in a Bultfontein peridotite

    Wainwright, A. N.; Luguet, A.; Schreiber, A.; Fonseca, R. O. C.; Nowell, G. M.; Lorand, J.-P.; Wirth, R.; Janney, P. E.


    Understanding the mineralogical controls on radiogenic chronometers is a fundamental aspect of all geochronological tools. As with other common dating tools, it has become increasingly clear that the Re-Os system can be impacted by multiple mineral formation events. The accessory and micrometric nature of the Re-Os-bearing minerals has made assessing this influence complex. This is especially evident in cratonic peridotites, where long residence times and multiple metasomatic events have created a complex melting and re-enrichment history. Here we investigate a harzburgitic peridotite from the Bultfontein kimberlite (South Africa) which contains sub-micron Pt-Fe-alloy inclusions within base metal sulphides (BMS). Through the combination of the focused ion beam lift-out technique and low blank mass spectrometry we were able to remove and analyse the Pt-Fe-alloy inclusions for their Re-Os composition and highly siderophile element (HSE) systematics. Six repeats of the whole-rock yield 187Os/188Os compositions of 0.10893-0.10965, which correspond to Re depletion model ages (TRD) of 2.69-2.79 Ga. The Os, Ir and Pt concentrations are slightly variable across the different digestions, whilst Pd and Re remain constant. The resulting HSE pattern is typical of cratonic peridotites displaying depleted Pt and Pd. The Pt-Fe-alloys have PUM-like 187Os/188Os compositions of 0.1294 ± 24 (2-s.d.) and 0.1342 ± 38, and exhibit a saw-tooth HSE pattern with enriched Re and Pt. In contrast, their BMS hosts have unradiogenic 187Os/188Os of 0.1084 ± 6 and 0.1066 ± 3, with TRD ages of 2.86 and 3.09 Ga, similar to the whole-rock systematics. The metasomatic origin of the BMS is supported by (i) the highly depleted nature of the mantle peridotite and (ii) their Ni-rich sulphide assemblage. Occurrence of Pt-Fe-alloys as inclusions within BMS grains demonstrates the genetic link between the BMS and Pt-Fe-alloys and argues for formation during a single but continuous event of silicate melt

  9. Os-He Isotope Systematics of Iceland Picrites: Evidence for a Deep Origin of the Iceland Plume

    Brandon, Alan D.; Graham, David W.; Waight, Tod; Gautason, Bjarni


    Recent work on the origin of the Iceland hotspot suggests that it may result from upwelling upper mantle material rather than a deep plume. To constrain the depths of origins of Iceland mantle sources, Os and He isotope systematics were obtained on a suite picrites that span the compositional range observed within the neovolcanic zones.

  10. Re-Os isotope measurements of single sulfide inclusions in a Siberian diamond and its nitrogen aggregation systematics

    Pearson, D. G.; Shirey, S. B.; Bulanova, G. P.; Carlson, R. W.; Milledge, H. J.


    We have measured the Re-Os isotopic compositions of individual syngenetic sulfide inclusions from three different growth zones within a central cross section plate cut from a single Siberian diamond. Individual sulfides in their diamond host were isolated by laser cutting. The sulfides, and hence the different growth zones of the diamond have been suggested to differ in age by up to 2 Ga on the basis of their Pb isotope compositions. Re-Os model ages of the four inclusions range from 3.1 ± 0.3 to 3.5 ± 0.3 Ga and suggest a Middle Archaean age for the diamond. A sulfide inclusion in the rim of the diamond is very different in elemental composition from those of the core and intermediate zones. It is enriched in Os, Re, Pb, and Zn and has more radiogenic Os and Pb isotopes. The inclusion is connected to the surface of the diamond by a healed crack, revealed by cathodoluminescence. The compositional distinction may be caused either by postformational interaction between an ancient sulfide and a fluid, possibly at the time of kimberlite eruption, or later stage growth of new diamond plus sulfide. Such chemical complexities, and the presence of healed fractures within the host diamond, emphasize the desirability of analyzing individual inclusions from well-characterized diamonds if isotope data for inclusions are to be better understood. Nitrogen contents and aggregation state in the core and intermediate zone of the host diamond closely approximate theoretically calculated isotherms based on consideration of experimentally determined nitrogen aggregation kinetics. The nitrogen content of the rim diamond is too low to obtain spectra that allow accurate deconvolution of relative aggregation levels for use in residence time calculations. The aggregation state of nitrogen in the core and intermediate growth zones is compatible with a long, ca. 3 Ga mantle residence time at normal lithospheric temperatures. The similarity of the sulfide inclusion Re-Os model ages to the

  11. Sulfur isotope composition of metasomatised mantle xenoliths from the Bultfontein kimberlite (Kimberley, South Africa): Contribution from subducted sediments and the effect of sulfide alteration on S isotope systematics

    Giuliani, Andrea; Fiorentini, Marco L.; Martin, Laure A. J.; Farquhar, James; Phillips, David; Griffin, William L.; LaFlamme, Crystal


    Sulfur isotopes are a powerful geochemical tracer in high-temperature processes, but have rarely been applied to the study of mantle metasomatism. In addition, there are very limited S isotope data on sub-continental lithospheric mantle (SCLM) material. For cratonic regions, these data are restricted to sulfide inclusions in diamonds. To provide new constraints on the S isotope composition of the SCLM and on the source(s) of mantle metasomatic fluids beneath the diamondiferous Kimberley region (South Africa), we investigated the S isotope systematics of five metasomatised mantle xenoliths from the Bultfontein kimberlite. Pentlandite and chalcopyrite in these xenoliths were analysed by in situ secondary-ion mass spectrometry (SIMS), with bulk-rock material measured by gas source isotope ratio mass spectrometry techniques. Based on previous studies, the xenoliths experienced different types of metasomatism to one another at distinct times (∼180 and ∼90-80 Ma). Contained pentlandite grains show variable alteration to heazlewoodite (i.e. Ni sulfide) + magnetite. The in situ S isotope analyses of pentlandite exhibit a relatively restricted range between -5.9 and - 1.4 ‰δ34 S (compared to VCDT), with no statistically meaningful differences between samples. Chalcopyrite only occurs in one sample and shows δ34 S values between -5.4 and - 1.0 ‰. The bulk-rock Ssulfide isotope analyses vary between -3.4 and + 0.8 ‰δ34 S. Importantly, the only sample hosting dominantly fresh sulfides shows a bulk-rock δ34 S value consistent with the mean value for the sulfides, whereas the other samples exhibit higher bulk 34S/32S ratios. The differences between bulk-rock and average in situδ34 S values are directly correlated with the degree of sulfide alteration. This evidence indicates that the elevated 34S/32S ratios in the bulk samples are not due to the introduction of heavy S (commonly as sulfates) and are best explained by isotopic fractionation coupled with the removal

  12. Mantle mixing and crustal contamination as the origin of the high-Sr radiogenic magmatism of Stromboli (Aeolian arc)

    Luais, Béatrice


    The temporal evolution of the volcanic activity on Stromboli (Aeolian arc) is characterized by high-K calc-alkaline magmatism followed by shoshonitic magmatism. Rocks from the two series can be distinguished by their K and P concentrations, hygromagmaphile element concentrations, and Sr isotopic ratios, which are higher in the shoshonitic series than in high-K calc-alkaline series. The mantle oxygen isotopic ratios of the shoshonitic series (Javoy, 1976 [39]) suggest that these characteristics are generated in the upper mantle. The geochemical and isotopic characteristics of the magmatism on Stromboli are midway between those of calc-alkaline rocks from the Aeolian arc and potassic rocks from Central Italy (Campanian region). The similarity between the most radiogenic and LILE-enriched samples of the shoshonitic series and the low-K magmatism in Central Italy suggests that the volcanism on Stromboli is the result of mantle mixing between a calc-alkaline magma and a radiogenic Sr/hygromagmaphile element-enriched magma, such as the high-K magmatism in Central Italy (Alban Hills). The chemical and isotopic characteristics of the differentiated samples can be explained by crustal contamination during the differentiation of the basic liquid by fractional crystallization. An anorthose-bearing xenolith with high Sr isotopic composition of crustal origin (0.71300) is a likely candidate for this crustal component.

  13. Mantle mixing and crustal contamination as the origin of the high-Sr radiogenic magmatism of Stromboli (Aeolian arc)

    Luais, B.


    The temporal evolution of the volcanic activity on Stromboli (Aeolian arc) is characterized by high-K calc-alkaline magmatism followed by shoshonitic magmatism. Rocks from the two series can be distinguished by their K and P concentrations, hygromagmaphile element concentrations, and Sr isotopic ratios, which are higher in the shoshonitic series than in high-K calc-alkaline series. The mantle oxygen isotopic ratios of the shoshonitic series suggest that these characteristics are generated in the upper mantle. The geometrical and isotopic characteristics of the magmatism on Stromboli are midway between those of calc-alkaline rocks from the Aeolian arc and potassic rocks from Central Italy (Campanian region). The similarity between the most radiogenic and LILE-enriched samples of the shoshonitic series and the low-K magmatism in Central Italy suggests that the volcanism on Stromboli is the result of mantle mixing between a calc-alkaline magma and a radiogenic Sr/hygromagmaphile element-enriched magma, such as the high-K magmatism in Central Italy (Alban Hills). The chemical and isotopic characteristics of the differentiated samples can be explained by crustal contamination during the differentiation of the basic liquid by fractional crystallization. An anorthose-bearing xenolith with high Sr isotopic composition of crustal origin (0.71300) is a likely candidate for thus crustal component.

  14. Li and B Isotope Systematics of Ultrahigh-pressure Metamorphic Rocks from the Chinese Continental Scientific Drilling Program

    Yilin Xiao; Rolf L. Romer; Jochen Hoefs; Anette Meixner; Zeming Zhang


    @@ 1 Introduction Recent improvements in the precision of Li and B isotope measurements have demonstrated the potential of these elements in tracing a wide range of geological processes. The Li and B isotope systematics of ultrahigh-pressure (UHP) metamorphic rocks provides a unique opportunity to investigate the behaviour of Li and B during fluid-rock interaction at high temperatures and very high pressures and to constrain the fluid budget and the recycling of subducted crustal materials into the mantle during UHP metamorphism.

  15. Clumped-Isotope Thermometry and Oxygen Isotope Systematics in Speleothem Calcite From a Near Cave-Entrance Environment

    Carlson, P. E.; Banner, J.; Breecker, D.; Affek, H. P.


    Speleothems that grow in well-ventilated zones of caves have not been widely used in paleoclimate studies, yet may provide paleotemperature records. These zones are characterized by low CO2 concentrations year-round and, in temperate climates, large seasonal temperature fluctuations. They are typically avoided for paleoclimate reconstruction due to concerns about kinetic isotope effects (KIE). However, speleothems in general seem to be sensitive to KIE, even in non-ventilated areas and can nonetheless provide useful paleoclimate records. At Westcave Preserve (Westcave), a shallow, well-ventilated cave in central Texas, we have found seasonal temperature differences recorded in both the oxygen isotope and clumped isotope compositions of speleothem calcite grown on glass-plate substrates harvested from active drips. Although growth rates in this cave are relatively rapid, speleothem analogs in Westcave are growing near oxygen-isotopic equilibrium with their drip waters (between the calibrations of Kim and O'Neil, 1997 and Coplen, 2007). We have tested the compatibility of the Zaarur et al. (2013) clumped isotope bulk solution thermometer calibration to glass-substrate calcite in the cave collected during various months. This technique can provide absolute temperatures, but is sensitive to kinetic isotope effects, often significantly overestimating growth temperatures of speleothems. When this thermometer was applied to calcite collected from near where the plates were impacted by drip water, it overestimated measured temperatures by 7.7 ± 4.3°C, showing moderate KIE. When applied to calcite away from the drip impact, it overestimated temperatures by 18.7 ± 4.2°C, showing KIE increasing away from the drip. Measured monthly average temperatures in the cave ranged seasonally between 8 and 28°C, and daily temperatures vary significantly. At Westcave, calcite growth rates increase with temperature, and the calcite may therefore preferentially record warmer daily or

  16. Regional trends in radiogenic heat generation in the Precambrian basement of the Western Canadian Basin

    Jones, F. W.; Majorowicz, J. A.

    Radiogenic heat generation values for 381 basement samples from 229 sites in the western Canadian basin exhibit a lognormal frequency distribution. The mean value = 2.06 (S.D. = 1.22) µWm-3 is larger than the radiogenic heat generation values reported for the shield in the Superior (ca. 1.2 µWm-3, Jessop and Lewis, 1978) and Churchill (ca. 0.7 µWm-3, Drury, 1985) provinces. When equal Log A contour intervals are used to map the basement heat generation, three large zones of relatively high heat generation are found. One coincides with the Peace River Arch basement structure and one with the Athabasca axis (Darnley, 1981). There is no apparent indication of increased heat flow through the Paleozoic formations associated with these two zones. The third zone, in southwestern Saskatchewan, coincides with a high heat flow zone in the Swift Current area. The lack of correlation between heat flow and heat generation in Alberta may be due to the disturbance to the heat flow in the Paleozoic formations by water motion, or may indicate that the heat is from uranium, thorium and potassium isotope enrichment near the basement surface rather than enrichment throughout the entire upper crust.

  17. Systematic of Nuclear Ground State Properties in Sr Isotope by Covariant Density Functional Theory

    TIAN; Yuan


    <正>The hyperfine structure and isotope shifts of Sr-isotopes, both even-even and odd-even nuclei, are studied in the covariant density functional theory (DFT) with the new parameter set DD-PC1. Pairing correlation is treated by using the Bogoliubov with a separable form of the pairing interaction. Spin-parity,

  18. Calcium isotope systematics in small upland catchments affected by spruce dieback in the period of extreme acid rain (1970-1990)

    Novak, Martin; Farkas, Juraj; Holmden, Chris; Hruska, Jakub; Curik, Jan; Stepanova, Marketa; Prechova, Eva; Veselovsky, Frantisek; Komarek, Arnost


    Recently, new isotope tools have become available to study the behavior of nutrients in stressed ecosystems. In this study, we focus on changes in the abundance ratio of calcium (Ca) isotopes accompanying biogeochemical processes in small forested catchments. We monitored del44Ca values in ecosystem pools and fluxes in four upland sites situated in the Czech Republic, Central Europe. A heavily acidified site in the Eagle Mts. (northern Czech Republic) experienced 13 times higher atmospheric Ca inputs, compared to the other three sites, which were less affected by forest decline. Industrial dust was responsible for the elevated Ca input. Del44Ca values of individual poos/fluxes were used to identify Ca sources for the bioavailable Ca soil reservoir and for runoff. The bedrock of the study sites differed (leucogranite, orthogneiss vs. serpentinite and amphibolite). Across the sites, mean del44Ca values increased in the order: spruce bark < fine roots < needles < soil < bedrock < canopy throughfall < open-area precipitation < runoff < soil water. Plant preferentially took up isotopically light Ca, while residual isotopically heavy Ca was sorbed to soil particles or exported via runoff. Even at sites with a low del44Ca values of bedrock, runoff had a high del44Ca value. At the base-poor site, most runoff came from atmospheric deposition and residual Ca following plant uptake. It appeared that bedrock weathering did not supply enough Ca to replenish the bioavailable Ca pool in the soil. Currently, we are analyzing Ca isotope composition of individual rock-forming minerals to better assess the effect of different weathering rates of minerals with low/high radiogenic 40Ca contents on runoff del44Ca.

  19. Basin-Scale nd Isotope Gradients in South Atlantic Marine Sedimentary Records

    Ran, W.; Abouchami, W.; Zahn, R.; Masque, P.


    Recent 231Pa/230Th and Nd isotopes studies have suggested a slower and re-configured Meridional Overturning Circulation in the Atlantic (AMOC) during the Last Glacial Maximum (LGM) [1]. We have undertaken a Sr and Nd isotope study on sediment core MD02-2594 (34°43'S, 17°20'E, 2440 m) located in the Cape Basin where nutrient-based proxies - δ13C and Cd/Ca ratios - and low 231Pa/230Th, a tracer of deep water overturning rate, indicate the presence of Southern Component Water (SCW) and a weaker AMOC during the LGM [1]. Samples cover the LGM and Holocene sections of the core previously analysed for Pa/Th [1]. Sr and Nd isotope data were obtained on the bulk sediment as well as on the Fe-Mn oxides leachates and the residual detrital fraction extracted using established sequential leaching procedure. Analyses were performed on a ThermoFisher Triton TIMS at MPIC and Nd isotopes measured as NdO. Our results show that the bulk sediment Nd isotope record is, as expected, overprinted by the Nd isotope composition of the lithogenic fraction and follows closely the 231Pa/230Th record. Sr isotope ratios in Fe-Mn leachates have been used as diagnostic of a seawater origin for the Fe-Mn oxides which should yield modern seawater Sr isotopic composition. Our samples have 87Sr/86Sr ratios similar to or slightly higher than those measured for seawater [2]. The Nd isotope composition of the Fe-Mn leachates show, nevertheless, a distinct signature from both the bulk sediment and the detrital fraction, both of which display systematically less radiogenic Nd isotope ratios throughout the whole record. The seawater ɛNd record exhibits a decreasing trend from the LGM into the Bolling-Allerød and Younger Dryas, prior to stabilizing at a value of about -9 during the Holocene. Covariations between Nd isotope ratios of Fe-Mn leachates and 231Pa/230Th reveal contrasted behaviour during the LGM and the Holocene period: low and nearly constant glacial Pa/Th values are associated with

  20. Lithium isotope systematics in a forested granitic catchment (Strengbach, Vosges Mountains, France)

    Lemarchand, Emmanuel; Chabaux, François; Vigier, Nathalie; Millot, Romain; Pierret, Marie-Claire


    Over the last decade it has become apparent that Li isotopes may be a good proxy to trace silicate weathering. However, the exact mechanisms which drive the behaviour of Li isotopes in surface environments are not totally understood and there is a need to better calibrate and characterize this proxy. In this study, we analysed the Li concentrations and isotopic compositions in the various surface reservoirs (soils, rocks, waters and plants) of a small forested granitic catchment located in the Vosges Mountains (Strengbach catchment, France, OHGE Li fluxes were calculated in both soil profiles and at the basin scale and it was found that even in this forested basin, atmospheric inputs and litter fall represented a minor flux compared to input derived from the weathering of rocks and soil minerals (which together represent a minimum of 70% of dissolved Li). Li isotope ratios in soil pore waters show large depth dependent variations. Average dissolved δ 7Li decreases from -1.1‰ to -14.4‰ between 0 and -30 cm, but is +30.7‰ at -60 cm. This range of Li isotopic compositions is very large and it encompasses almost the entire range of terrestrial Li isotope compositions that have been previously reported. We interpret these variations to result from both the dissolution and precipitation of secondary phases. Large isotopic variations were also measured in the springs and stream waters, with δ 7Li varying from +5.3‰ to +19.6‰. δ 7Li increases from the top to the bottom of the basin and also covaries with discharge at the outlet. These variations are interpreted to reflect isotopic fractionations occurring during secondary phase precipitation along the water pathway through the rocks. We suggest that the dissolved δ 7Li increases with increasing residence time of waters through the rocks, and so with increasing time of interaction between waters and solids. A dissolution precipitation model was used to fit the dissolved Li isotopic

  1. Systematic study of the (n,p) and (n,n'p) reactions on titanium isotopes

    Avrigeanu, M.; Ivascu, M.; Avrigeanu, V.


    Geometry-dependent hybrid and Hauser-Feshbach model calculations were performed for (n,p), (n,n'p) and (n,2n) reaction cross-sections for stable titanium isotopes in the energy range from threshold to 20 MeV. A consistent set of input parameters was established. The single-particle level density used in the pre-equilibrium emission calculation was related to the level density parameter of the Hauser-Feshbach calculations, including its energy dependence. Consequently, lower pre-equilibrium emission fractions were obtained. Systematics of the pre-equilibrium and statistical contributions to (n,p) reaction cross-sections are analysed in connection with the isotope effect put into evidence by the titanium data.

  2. Argon isotope fractionation induced by stepwise heating

    Trieloff, Mario; Falter, Martina; Buikin, Alexei I.; Korochantseva, Ekaterina V.; Jessberger, Elmar K.; Altherr, Rainer


    Noble gas isotopes are widely used to elucidate the history of the rocks in which they have been trapped, either from distinct reservoirs or by accumulation following radioactive decay. To extract noble gases from their host rocks, stepwise heating is the most commonly used technique to deconvolve isotopically different components, e.g., atmospheric, in situ radiogenic, or excess radiogenic from mantle or crustal reservoirs. The accurate determination of the isotopic composition of these different components is of crucial importance, e.g., for ages obtained by 40Ar- 39Ar stepheating plateaus. However, diffusion theory-based model calculations predict that the stepwise thermal extraction process from mineral phases induces isotope fractionation and, hence, adulterates the original composition. Such effects are largely unconsidered, as they are small and a compelling experimental observation is lacking. We report the first unequivocal evidence for significant mass fractionation of argon isotopes during thermal extraction, observed on shungite, a carbon-rich Precambrian sedimentary rock. The degree of fractionation, as monitored by 38Ar/ 36Ar and 40Ar/ 36Ar ratios, very well agrees with theoretical predictions assuming an inverse square root dependence of diffusion coefficient and atomic mass, resulting in easier extraction of lighter isotopes. Hence, subatmospheric 40Ar/ 36Ar ratios obtained for argon extracted at low temperatures may not represent paleoatmospheric argon. Shungite argon resembles modern atmospheric composition, but constraints on the timing of trapping appear difficult to obtain, as shungites are multicomponent systems. In 40Ar- 39Ar stepwise heating, the isotope fractionation effect could cause systematic underestimations of plateau ages, between 0.15 and 0.4% depending on age, or considerably higher if samples contain appreciable atmospheric Ar. The magnitude of this effect is similar to the presently achieved uncertainties of this increasingly

  3. The Role of Accessory Phases in the Sm-Nd Isotope Systematics of the Acasta Gneiss Complex

    Bauer, A.; Fisher, C. M.; Vervoort, J. D.; Bowring, S. A.


    The Acasta Gneiss Complex (AGC) of the Slave Craton in the Northwest Territories, Canada, contains some of Earth's oldest continental crust. It is characterized by a range of compositionally diverse gneisses with crystallization ages of 3.3 to > 4.0 Ga1-5. The AGC has undergone a multistage history of metamorphism and deformation. Given these post-crystallization processes, the extent of Nd isotope heterogeneity suggested by published4-7 whole rock Sm-Nd analyses of these rocks has been called into question. Criticisms include the likelihood of mixed lithologies at the hand-sample scale and the potential for open-system behavior of the Sm-Nd isotopic system in these rocks. We obtained whole rock compositional, Sm-Nd and Lu-Hf isotope data paired with Hf in zircon and Nd in titanite and apatite data to further evaluate the isotope record, and use U-Pb and Lu-Hf of zircon as a basis for identifying mixed or complex samples. Preferential preservation of Lu-Hf over Sm-Nd isotope systematics in multiply deformed, complex rocks may be controlled by the minerals that dominate the Hf and Nd budgets, with the majority of the Hf effectively sheltered in zircon and the Nd largely hosted in accessory phases such as apatite and titanite. This composite dataset enables us to evaluate the possibility that Hf and Nd isotopic systematics have been decoupled in these samples that have such critical bearing on our understanding of early crust-forming processes. [1]Bowring and Williams (1999). CoMP, 134(1), 3-16. [2]Iizuka, T. et al. (2006) Geology, 34(4), 245-248. [3]Iizuka et al (2007). Precambrian Res, 153(3), 179-208. [4]Bowring et al. 1989. Nature, 340: 222-225. [5]Mojzsis et al. (2014). GCA, 133, 68-96. [6]Bowring and Housh (1995) Science 269, 1535-1540. [7]Moorbath et al (1997) Chem. Geol. 135, 213-231.

  4. Oxygen isotope systematics of chondrules in the Allende CV3 chondrite: High precision ion microprobe studies

    Rudraswami, N.G.; Ushikubo, T.; Nakashima, D.; Kita, N.T.

    chondrules range from -5 ppt to 0 ppt, indicating that not all BO chondrules plot near the terrestrial fractionation line as suggested by previous bulk chondrule analyses. Based on these data, we suggest the presence of multiple oxygen isotope reservoirs...

  5. Zn and Ni Isotope Systematics in the Black Sea, an Analogue for Past Ocean Anoxia

    Little, S. H.; Vance, D.; Cameron, V.; Rijkenberg, M. J. A.; Andersen, M. B.; Lyons, T. W.


    Organic rich sediments, indicators of low bottom water oxygen, are often enriched in trace metals. Their concentrations in such sediments are thus used to probe past Earth surface conditions. Enrichment mechanisms are difficult to distinguish from concentrations alone, however. A range of processes fractionate metal stable isotopes, offering the potential to unpick these controls. The Black Sea is the classic modern analogue for past euxinia. Deep euxinic waters (dissolved sulfide ≤380mM) underlie a surface oxic layer and redoxcline at 80-250m. It is an ideal starting point to explore the behaviour of metal stable isotopes in low oxygen conditions. We report water column and sedimentary Zn and Ni data. A maximum in dissolved Zn (~3nM) occurs at the upper boundary of the redoxcline, probably reflecting cellular uptake above and sulfide co-precipitation below. Water column dissolved Ni concentrations remain within a narrow range throughout (9-12nM), with subtle variations in the redoxcline associated with Fe-Mn cycling and interaction with sulfide. Significant Zn and Ni isotopic variation (ca 1.5‰) is observed associated with these concentration variations. In the strongly sulfidic deep waters, Zn and Ni are homogeneous and isotopically heavy: [Zn] = 0.40 ± 0.05nM, δ66Zn = 0.96 ± 0.05‰, [Ni] = 10.7 ± 0.7nM, δ58Ni = 1.86 ± 0.16‰ (n=6, 1sd), suggesting preferential removal of light isotopes to the particulate phase. Sediments underlying oxic waters show no authigenic enrichment and isotope ratios close to crustal values (δ60Ni ~ 0.2‰, δ66Zn ~ 0.3‰). In contrast, Ni and Zn are enriched in sediments underlying the euxinic portion of the water column (by factors of 2-3). Authigenic Ni isotope values are light (δ60Niauth = 0.30 ± 0.21‰, n=13, 1sd) compared to the deep Black Sea water column, consistent with removal of light isotopes to the particulate phase. This may reflect sorption to Mn oxides, or co-precipitation with sulfide. Authigenic Zn

  6. Ca isotope fingerprints of early crust-mantle evolution

    Kreissig, K.; Elliott, T.


    The utility of 40Ca/ 44Ca as a tracer of pre-existing crustal contributions in early Archaean cratons has been explored to identify traces of Hadean crust and to assess the style of continental growth. The relatively short half-life of 40K (˜1.3 Gy) means that its decay to 40Ca occurs dominantly during early Earth History. If Archaean crust had a significant component derived from a more ancient protolith, as anticipated by "steady state" crustal evolution models, this should be clearly reflected in radiogenic 40Ca/ 44Ca ratios (or positive initial ɛ Ca) in different Archaean cratons. A high precision thermal ionisation technique has been used to analyse the 40Ca/ 44Ca ratios of plagioclase separates and associated whole rocks in ˜3.6 Ga (early Archaean) samples from Zimbabwe and West Greenland. Three out of four tonalite, trondhjemite, granodiorite (TTG) suite samples from Zimbabwe display initial 40Ca/ 44Ca ratios indistinguishable from our measured modern MORB value (i.e., ɛ Ca(3.6) ˜ 0). Greenland samples, however, are very diverse ranging from ɛ Ca(3.7) = 0.1 in mafic pillow lavas and felsic sheets from the Isua supracrustal belt, up to very radiogenic signatures (ɛ Ca(3.7) = 2.9) in both mafic rocks of the Akilia association and felsic TTG from the coastal Amîtsoq gneisses. At face value, these results imply the Zimbabwe crust is juvenile whereas most Greenland samples include an earlier crustal component. Yet the west Greenland craton, as with many Archaean localities, has experienced a complex geological history and the interpretation of age-corrected initial isotope values requires great care. Both felsic and mafic samples from Greenland display ɛ Ca(3.7) so radiogenic that they are not readily explained by crustal growth scenarios. The presence of such radiogenic 40Ca/ 44Ca found in low K/Ca plagioclases requires Ca isotope exchange between plagioclase and whole rock during later metamorphic event(s). In addition the unexpectedly radiogenic Ca

  7. A Systematic Regional Trend in Helium Isotopes Across the NorthernBasin and Range Province, Western North America

    Kennedy, B. Mack; van Soest, Matthijs C.


    An extensive study of helium isotopes in fluids collectedfrom surface springs, fumaroles and wells across the northern Basin andRange Province reveals a systematic trend of decreasing 3He/4He ratiosfrom west to east. The western margin of the Basin and Range ischaracterized by mantle-like ratios (6-8 Ra) associated with active orrecently active crustal magma systems (e.g. Coso, Long Valley, Steamboat,and the Cascade volcanic complex). Moving towards the east, the ratiosdecline systematically to a background value of ~;0.1 Ra. The regionaltrend is consistent with extensive mantle melting concentrated along thewestern margin and is coincident with an east-to-west increase in themagnitude of northwest strain. The increase in shear strain enhancescrustal permeability resulting in high vertical fluid flow rates thatpreserve the high helium isotope ratios at the surface. Superimposed onthe regional trend are "helium spikes", local anomalies in the heliumisotope composition. These "spikes" reflect either local zones of mantlemelting or locally enhanced crustal permeability. In the case of theDixie Valley hydrothermal system, it appears to be a combination ofboth.

  8. Evidence for Radiogenic Sulfur-32 in Type AB Presolar Silicon Carbide Grains?

    Fujiya, Wataru; Zinner, Ernst; Pignatari, Marco; Herwig, Falk


    We report C, Si, and S isotope measurements on 34 presolar silicon carbide grains of Type AB, characterized by 12C/13C < 10. Nitrogen, Mg-Al-, and Ca-Ti-isotopic compositions were measured on a subset of these grains. Three grains show large 32S excesses, a signature that has been previously observed for grains from supernovae (SNe). Enrichments in 32S may be due to contributions from the Si/S zone and the result of S molecule chemistry in still unmixed SN ejecta or due to incorporation of radioactive 32Si from C-rich explosive He shell ejecta. However, a SN origin remains unlikely for the three AB grains considered here, because of missing evidence for 44Ti, relatively low 26Al/27Al ratios (a few times 10-3), and radiogenic 32S along with low 12C/13C ratios. Instead, we show that born-again asymptotic giant branch (AGB) stars that have undergone a very-late thermal pulse (VLTP), known to have low 12C/13C ratios and enhanced abundances of the light s-process elements, can produce 32Si, which makes such sta...

  9. Lead isotope systematics of some igneous rocks from the Egyptian Shield

    Gillespie, J. G.; Dixon, T. H.


    Lead isotope data on whole-rock samples and two feldspar separates for a variety of Pan-African (late Precambrian) igneous rocks for the Egyptian Shield are presented. It is pointed out that the eastern desert of Egypt is a Late Precambrian shield characterized by the widespread occurrence of granitic plutons. The lead isotope ratios may be used to delineate boundaries between Late Precambrian oceanic and continental environments in northeastern Africa. The samples belong to three groups. These groups are related to a younger plutonic sequence of granites and adamellites, a plutonic group consisting of older tonalites to granodiorites, and the Dokhan volcanic suite.

  10. Quasi – biological model of radiogenic cancer morbidity

    A. T. Gubin


    Full Text Available The methods: Linear differential equations were used to formalize contemporary assumptions of self –sustaining tissue cell kinetics under the impact of adverse factors, on the formation and repairing of cell “pre-cancer” defects, on inheritance and retaining such defects in daughter cells which results in malignant neoplasms, on age-dependent impairment of human body’s function to eliminate such cells.The results: The model reproduces the well-known regularities of radiogenic cancer morbidity increase depending on instantaneous radiation exposure age and on attained age: the relative reduction at increased radiation age which the model attributes to age decrease of stem cells, relative reduction at increased time after radiation induced by “sorting out” of cells with “pre-cancer” defects, absolute increase with age proportional to natural cause mortality rate.The relevance of the developed quasi-biological model is displayed via comparison to the ICRP model for radiogenic increase of solid carcinomas’ morbidity after single radiation exposure. The latter model had been developed after Japanese cohort observations. For both genders high goodness-of-fit was achieved between the models at values of Gompertz’ law factor which had been defined for men and women in this cohort via selecting the value of the only free parameter indicating age-dependent exponential retardation of stem cells’ division.The conclusion: The proposed model suggests that the estimation of radiogenic risk inter-population transfer can be done on the basis of the data on age-dependent mortality intensity increase from all natural causes. The model also creates the premises for inter-species transfer of risk following the well-known parameters of cell populations’ kinetics in animal’s organs and tissues and Gompertz’s law parameters. This model is applicable also for analyses of age-dependent changes of background cancer morbidity. 

  11. Chromium stable isotope systematic – implications for the redox evolution of the earth

    Døssing, Lasse Nørbye

    The isotopic composition of chromium (Cr) holds great promise as a paleo-redox proxy.Whereas the reduction of oxidized Cr(VI) to Cr(III) yields a well-defined kineticfractionation, the fractionation imparted during oxidative weathering is only described theoretically. This thesis demonstrates...

  12. Complexity of In-situ zircon U-Pb-Hf isotope systematics during arc magma genesis at the roots of a Cretaceous arc, Fiordland, New Zealand

    Milan, L. A.; Daczko, N. R.; Clarke, G. L.; Allibone, A. H.


    Zircons from seventeen samples of Western Fiordland Orthogneiss (WFO) diorites and three samples of country rock (two schists and one Darran Suite diorite) from the lowermost exposed sections of the Median Batholith, Fiordland, New Zealand, were analysed for in-situ U-Pb and Hf-isotopes. The WFO represents the deeper levels of Early Cretaceous continental arc magmatism on the Pacific margin of Gondwana, marking the final stage of long-lived arc magmatism on the margin spanning the Palaeozoic. The WFO plutons were emplaced at high-P (mid to deep crust at c. 8-12 kbar) between 124 and 114 Ma. Minor very high-P (c. 18 kbar) WFO eclogite and omphacite granulite facies orthogneiss (Breaksea Orthogneiss) are inferred to have crystallised in the base of thickened crust at c. 124 Ma. Zircons from the Breaksea Orthogneiss are considered to be variably affected by Pb-loss due to emplacement of the adjacent (Malaspina) Pluton at c. 114 Ma. By identifying Pb-loss, magmatic ages were able to be inferred in respect to apparent Pb-loss ages. Hf isotope data for the WFO define an excursion to less radiogenic Hf isotope ratios with time, reflecting increased recycling of an old source component. Peaks at c. 555, 770 and 2480 Ma, determine the age spectra of inherited populations of zircons within the WFO. This contrasts with detrital zircon patterns in country rocks of the Takaka terrane, which include peaks at c. 465 Ma, and 1250-900 Ma that are absent in the WFO inheritance pattern. These results indicate a previously unrecognised Precambrian lower crustal component of New Zealand. Recycling of this lower crust became increasingly important as a source for the final stage or Mesozoic arc magmatism along this segment of the palaeo-Pacific margin of Gondwana.

  13. The Early Differentiation History of Mars from W-182-Nd-142 Isotope Systematics in the SNC Meteorites

    Foley, C. Nicole; Wadhwa, M.; Borg, L. E.; Janney, P. E.; Hines, R.; Grove, T. L.


    We report here the results of an investigation of W and Nd isotopes in the SNC (Shergottite-Nakhlite-Chassignite (martian)) meteorites. We have determined that epsilon W-182 values in the nakhlites are uniform within analytical uncertainties and have an average value of approx. 3. Also, while epsilon W-182 values in the shergottites have a limited range (from 0.3-0.7), their epsilon Nd-142 values vary considerably (from -0.2-0.9). There appears to be no correlation between epsilon W-182 and epsilon Nd-142 in the nakhlites and shergottites. These results shed new light on early differentiation processes on Mars, particularly on the timing and nature of fractionation in silicate reservoirs. Assuming a two-stage model, the metallic core is estimated to have formed at approx. 12 Myr after the beginning of the solar system. Major silicate differentiation established the nakhlite source reservoir before approx. 4542 Ma and the shergottite source reservoirs at 4525 [sup +19 sub -21] Ma. These ages imply that, within the uncertainties afforded by the Hf-182-W-182 and Sm-146-Nd-142 chronometers, the silicate differentiation events that established the source reservoirs of the nakhlites and shergottites may have occurred contemporaneously, possibly during crystallization of a global magma ocean. The distinct W-182-Nd-142 isotope systematics in the nakhlites and the shergottites imply the presence of at least three isotopically distinct silicate reservoirs on Mars, two of which are depleted in incompatible lithophile elements relative to chondrites, and the third is enriched. The two depleted silicate reservoirs most likely reside in the Martian mantle, while the enriched reservoir could be either in the crust or the mantle. Therefore, the W-182-Nd-142 isotope systematics indicate that the nakhlites and the shergottites originated from distinct source reservoirs and cannot be petrogenetically related. A further implication is that the source reservoirs of the nakhlites and

  14. Systematic study of heavy cluster emission from {210-226}^Ra isotopes

    Santhosh, K P; Priyanka, B; Unnikrishnan, M S


    The half lives for various clusters lying in the cold reaction valleys of {210-226}^Ra isotopes are computed using our Coulomb and proximity potential model (CPPM). The computed half lives of 4^He and 14^C clusters from {210-226}^Ra isotopes are in good agreement with experimental data. Half lives are also computed using the Universal formula for cluster decay (UNIV) of Poenaru et al., and are found to be in agreement with CPPM values. Our study reveals the role of doubly magic 208^Pb daughter in cluster decay process. Geiger - Nuttall plots for all clusters up to 62^Fe are studied and are found to be linear with different slopes and intercepts. {12,14}^C emission from 220^Ra; 14^C emission from {222,224}^Ra; 14^C and 20^O emission from 226^Ra are found to be most favourable for measurement and this observation will serve as a guide to the future experiments.

  15. Systematic investigation of projectile fragmentation using beams of unstable B and C isotopes

    Thies, R; Adachi, T; Aksyutina, Y; Alcantara-Núñes, J; Altstadt, S; Alvarez-Pol, H; Ashwood, N; Aumann, T; Avdeichikov, V; Barr, M; Beceiro-Novo, S; Bemmerer, D; Benlliure, J; Bertulani, C A; Boretzky, K; Borge, M J G; Burgunder, G; Caamano, M; Caesar, C; Casarejos, E; Catford, W; Cederkäll, J; Chakraborty, S; Chartier, M; Chulkov, L V; Cortina-Gil, D; Crespo, R; Datta, U; Fernández, P Díaz; Dillmann, I; Elekes, Z; Enders, J; Ershova, O; Estradé, A; Farinon, F; Fraile, L M; Freer, M; Freudenberger, M; Fynbo, H O U; Galaviz, D; Geissel, H; Gernhäuser, R; Göbel, K; Golubev, P; Diaz, D Gonzalez; Hagdahl, J; Heftrich, T; Heil, M; Heine, M; Henriques, A; Holl, M; Ickert, G; Ignatov, A; Jakobsson, B; Johansson, H T; Jonson, B; Kalantar-Nayestanaki, N; Kanungo, R; Kelic-Heil, A; Knöbel, R; Kröll, T; Krücken, R; Kurcewicz, J; Kurz, N; Labiche, M; Langer, C; Bleis, T Le; Lemmon, R; Lepyoshkina, O; Lindberg, S; Machado, J; Marganiec, J; Maroussov, V; Mostazo, M; Movsesyan, A; Najafi, A; Nilsson, T; Nociforo, C; Panin, V; Paschalis, S; Perea, A; Petri, M; Pietri, S; Plag, R; Prochazka, A; Rahaman, A; Rastrepina, G; Reifarth, R; Ribeiro, G; Ricciardi, M V; Rigollet, C; Riisager, K; Röder, M; Rossi, D; del Rio, J Sanchez; Savran, D; Scheit, H; Simon, H; Sorlin, O; Stoica, V; Streicher, B; Taylor, J T; Tengblad, O; Terashima, S; Togano, Y; Uberseder, E; Van de Walle, J; Velho, P; Volkov, V; Wagner, A; Wamers, F; Weick, H; Weigand, M; Wheldon, C; Wilson, G; Wimmer, C; Winfield, J S; Woods, P; Yakorev, D; Zhukov, M V; Zilges, A; Zuber, K


    Background: Models describing nuclear fragmentation and fragmentation-fission deliver important input for planning nuclear physics experiments and future radioactive ion beam facilities. These models are usually benchmarked against data from stable beam experiments. In the future, two-step fragmentation reactions with exotic nuclei as stepping stones are a promising tool to reach the most neutron-rich nuclei, creating a need for models to describe also these reactions. Purpose: We want to extend the presently available data on fragmentation reactions towards the light exotic region on the nuclear chart. Furthermore, we want to improve the understanding of projectile fragmentation especially for unstable isotopes. Method: We have measured projectile fragments from 10,12-18C and 10-15B isotopes colliding with a carbon target. These measurements were all performed within one experiment, which gives rise to a very consistent dataset. We compare our data to model calculations. Results: One-proton removal cross sec...

  16. Entropy-information perspective to radiogenic heat distribution in continental crust

    Singh, R N; Manglik, A.


    Depth distribution of radiogenic heat sources in continental crust is an important parameter that controls its thermal structure as well as the mantle heat flow at the base of continental lithosphere. Various models for the depth distribution of radiogenic heat sources have been proposed. Starting from constant and exponential models based on linear heat flow–heat generation relationship the present-day layered models integrate crustal structure and laboratory measurements of radiogenic heat ...

  17. Disturbance of isotope systematics in meteorites during shock and thermal metamorphism and implications for shergottite chronology

    Gaffney, A M; Borg, L E; Asmerom, Y


    Shock and thermal metamorphism of meteorites from differentiated bodies such as the Moon and Mars have the potential to disturb chronometric information contained in these meteorites. In order to understand the impact-related mechanisms and extent of disturbance to isochrons, we undertook experiments to shock and heat samples of 10017, a 3.6 billion year old lunar basalt. One sub-sample was shocked to 55 GPa, a second subsample was heated to 1000 C for one week, and a third sub-sample was maintained as a control sample. Of the isotope systems analyzed, the Sm-Nd system was the least disturbed by shock or heat, followed by the Rb-Sr system. Ages represented by the {sup 238}U-{sup 206}Pb isotope system were degraded by shock and destroyed with heating. In no case did either shock or heating alone result in rotated or reset isochrons that represent a spurious age. In some cases the true crystallization age of the sample was preserved, and in other cases age information was degraded or destroyed. Although our results show that neither shock nor thermal metamorphism alone can account for the discordant ages represented by different isotope systems in martian meteorites, we postulate that shock metamorphism may render a meteorite more susceptible than unshocked material to subsequent disturbance during impact-related heating or aqueous alteration on Mars or Earth. The combination of these processes may result in the disparate chronometric information preserved in some meteorites.

  18. Pb, Nd, Sr and Os isotopic systematics of Brazilian cretaceous potassic rocks

    Araujo, Ana Lucia Novaes; Sichel, Susanna Eleonora [Universidade Federal Fluminense, Niteroi, RJ (Brazil). Inst. de Geociencias. Laboratorio de Geologia Marinha (LAGEMAR)]. E-mail:; Gaspar, Jose Carlos; Costa, Vicente Sergio [Brasilia Univ., DF (Brazil). Inst. de Geociencias; Carlson, Richard Walter [Carnegie Institution of Washington, Washington, DC (United States). DTM; Teixeira, Noevaldo Araujo [NTX Consultoria, Brasilia, DF (Brazil)


    Mafic potassic rocks of the Alto Paranaiba (Minas Gerais), Juina (Mato Grosso), and Pimenta BUeno (Mato Grosso) belong to a large lineament of rocks that crosses from western to southeastern Brazil and have been associated to a hot spot track by several authors. These provinces intruded the Neoproterozoic Brasilia and Paraguay fold belts (Alto Paranaiba, Paranatinga), and the Mesoproterozoic Rio Negro-Jurema belt (Juina, Pimenta Vueno). Pb isotopic compositions of the studied provinces show a wide variation. {sup 206} Pb/{sup 204} Pb of kimberlites (18.47-19.23) and kamafugities (17.79-18.71) from the Alto Paranaiba Province are close to the Tristaan/Walvis Ridge composition. The {sup 206} Pb/{sup 204} Pb of the paranatinga (19.38-19.87) and Pimenta Bueno (19.78-21.00) provinces are similar to the South African Group I Kimberlite compositional fields, while Juina is displaced to higher Pb isotopic ratios (, close to those shown ny HIMU ocean island +(OIB).Although the Pb isotopic composition of the more northern alkalic provinces ranges towards the values seen for HIMU OIB, the Sr andNd isotopic composition of these samples is not like HIMU, nor in combination with Pb, like any other ocean island basalt. With the exception of the limberlites from the Alto Paranaiba, which range to quite unradiogenic compositions, most of the samples have {sup 187} Os/{sup 188} Os between 0.13 and 0.15. The Nd model ages of Juina kimberlites vary from 1.70-1.73 Ga, and could be indicating a prior accretion period into the mobile belt. Nd model ages for paranatinga kimberlites vary between 0.56 and 0.64 Ga and Pimenta Bueno kimberlites from 0.72 to 1.05 Ga. Minimum Re depletion model ages for Paranatinga kimberlites vary between 0.74 and 0.93 and Pimenta Bueno kimberlites from 0.9 to 1.3 Ga, indicating that the Nd isotopic signartures could have been affected by metasomatic overprint in Neoroterozoic. (author)

  19. Natural radiogenic heat production in the northeastern part of the North German Basin; Natuerliche radiogene Waermeproduktion im Nordostdeutschen Becken

    Ullner, H.A. [GeoForschungsZentrum Potsdam (Germany)


    The radiogenic heat-production rate is a parameter that affects the thermal structure in the sedimentary cover. The parameter is important to warrant an extensive study. The first results gained in the northeastern part of the North German Basin show values in the range between 2.2 and 2.6 {mu}W/m{sup 3} in Permian mudstones in the Peckensen borehole and in the Bonese borehole (Altmark area). Comparable results were obtained in mudstones from a {gamma}-ray log measured in the Rheinsberg borehole (Brandenburg area). (orig.) [Deutsch] Die Untersuchung der thermischen Struktur des nordostdeutschen Beckens erfordert Kenntnisse ueber die radiogene Waermeproduktion der in zahlreichen Bohrungen aufgeschlossenen Sedimente. Die erste Ergebnisse eines am GFZ Postdam begonnenen Messprogrammes zeigen Waermeproduktionsraten im Bereich 2,2 bis 2,6 {mu}W/m{sup 3} in Tonsteinen des Perm in den Bohrungen Peckensen und Bonese (Altmark). Eine vergleichbare Waermeproduktion wurde anhand eines {gamma}-ray-Logs in Tonsteinen in der Bohrung Rheinsberg (Brandenburg) ermittelt. (orig.)

  20. Rare earth element concentrations and Nd isotopes in the Southeast Pacific Ocean

    Jeandel, C; Delattre, H; Grenier, M; Pradoux, C; Lacan, F


    .... At this station Nd isotopic compositions are clearly more radiogenic than in the open ocean, suggesting that boundary exchange process is releasing lithogenic rare earth element from the volcanic Andes...

  1. Sr, Ca, and C isotope systematic in small tropical catchments, La Selva, Costa Rica

    Wiegand, B. A.; Schwendenmann, L.


    Sr, Ca, and C isotopes were analyzed to assess sources and biogeochemical processes affecting surface and groundwater composition of four small catchments located at La Selva Biological Station, Costa Rica. 87Sr/86Sr ratios were employed to quantify inputs from mineral weathering and atmospheric sources. δ13C values of dissolved organic carbon (DOC) and δ44Ca values provide information on biological processes that affect water chemistry. Sr2+ and Ca2+ concentrations of surface and groundwater show large variations due to intermixture of bedrock groundwater with local groundwater [1]. Low 87Sr/86Sr ratios suggest weathering of volcanic rocks as the primary solute source in bedrock groundwater, while atmospheric and in situ weathering contributions are predominant in local groundwater. Contributions of bedrock groundwater constitute > 60 % in the Salto, Saltito and Arboleda catchments, whereas the Taconazo catchment receives atmospheric inputs of > 95 % in addition to local weathering contributions. Surface water and groundwater wells show δ13C-DOC values between -24 ‰ and -30 ‰ due to transfer of organic carbon from the soil zone. δ44Ca values of dissolved Ca2+ in surface and groundwater are considerably fractionated from the input sources rainwater and bedrock groundwater. Light δ44Ca values are preferentially distributed in stream water and shallow groundwater horizons and contrast with heavy Ca isotopes in deeper groundwater wells. Biological processes including plant uptake and decomposition in combination with cation exchange processes in the soils may explain the fractionation of Ca isotopes. [1]Genereux et al., 2009. Water Resour. Res, 45, W08413, doi:10.1029/2008WR007630

  2. Surface water?groundwater interactions in an alluvial plain: Chemical and isotopic systematics

    Négrel, Ph.; Petelet-Giraud, E.; Barbier, J.; Gautier, E.


    Our work on the Loire River forms part of a French National Research Program dedicated to wetlands and aims to better understand the global functioning of the system from the hydrological, geochemical, ecological and sociological aspects. The present study, using a coupled hydrological and geochemical (stable and Sr isotopes) approach, focuses on the 'Soulangy' site with its secondary anastomosing channels just below the confluence of the Loire and Allier rivers, and also on the 'Dorna``nt' site with two unconnected oxbow lakes 50 km upstream of the confluence. The stable isotopes of water ( δ18O, δ2H) show that the alluvial (or riverbank) aquifer feeds the Loire River during the summer, but is not recharged by the river during flood periods in the winter; the alluvial groundwater thus has a purely local origin from precipitation. The major elements reveal an anthropogenic input of Cl and more importantly of NO 3, especially near farms. The 87Sr/ 86Sr isotopes identify different groundwater layers in the alluvium, i.e. an upper and a lower alluvial aquifer, and a perched aquifer at Dornant, that have relatively complex relationships with the surface water. The two main rivers (Loire and Allier) present distinct geochemical characteristics reflecting the different lithologies that they drain upstream. In addition, the secondary channels, lying parallel to the Loire main stream at the Soulangy site, give different geochemical signatures, which shows that they are not fed by the same overflows of the Loire; they are more-or-less well connected to the upper level of the alluvial plain, and a longitudinal study of one of these channels has revealed a Loire River influence progressively replaced by a water contribution from the upper alluvial aquifer. Similarly, the two oxbow lakes at the Dornant site are not supplied by the same water during the summer months. A conceptual scheme of the Loire hydrosystem based on δ18O and 87Sr/ 86Sr suggests that the isotopic

  3. Systematic study of proton capture rates for Mo and Cd isotopes

    Bajpeyi, Awanish; Shukla, A. [Rajiv Gandhi Institute of Petroleum Technology, Department of Physics, Raebareli (India); Koning, A.J. [Nuclear Research and Consultancy Group NRG, Petten (Netherlands); Aaberg, Sven [Lund University, Mathematical Physics, P.O. Box 118, Lund (Sweden)


    Proton capture reactions play a very important role in the understanding of nucleosynthesis. In the present work, p-capture reactions have been studied coherently with nuclear structure for the nuclei under consideration. We have calculated proton capture cross sections and S-factor for relevant isotopes of molybdenum and cadmium in the energy range 2.0 to 4.5 Mev. Calculated results for nuclear structure as well reaction rates are compared with the available experimental and theoretical results and are found to be in good agreement. (orig.)

  4. Oxygen isotope systematics in an evolving geothermal system: Coso Hot Springs, California

    Etzel, Thomas M.; Bowman, John R.; Moore, Joseph N.; Valley, John W.; Spicuzza, Michael J.; McCulloch, Jesse M.


    Oxygen isotope and clay mineralogy studies have been made on whole rock samples and feldspar separates from three wells along the high temperature West Flank of the Coso geothermal system, California. The reservoir rocks have experienced variable 18O/16O depletion, with δ18O values ranging from primary values of + 7.5‰ down to - 4.6‰. Spatial patterns of clay mineral distributions in the three wells are not closely correlated with the distributions expected from measured, pre-production temperature profiles, but do correlate with spatial patterns of 18O/16O depletion, indicating that the stability of clay minerals in the three wells is a function of fluid-rock interaction in addition to temperature. Detailed δ18O measurements in the three wells identify a limited number of localized intervals of extensive 18O/16O depletion. These intervals document localized zones of higher permeability in the geothermal system that have experienced significant fluid infiltration, water-rock interaction and oxygen isotopic exchange with the geothermal fluids. The local zones of maximum 18O/16O depletion in each well correspond closely with current hot water production zones. Most feldspar separates have measured δ18O values too high to have completely attained oxygen isotope exchange equilibrium with the reservoir fluid at pre-production temperatures. In general, the lower the δ18O value of the feldspar, the closer the feldspar approaches exchange equilibrium with the geothermal fluid. This correlation suggests that fracture-induced increases in permeability increase both fluid infiltration and the surface area of the host rock exposed to geothermal fluid, promoting fluid-rock interaction and oxygen isotope exchange. The two most 18O/16O-depleted feldspar samples have δ18O values too low to be in exchange equilibrium with the pre-production reservoir fluid at pre-production temperatures. These discrepancies suggest that the reservoir fluid in the West Flank of the Coso

  5. KamLAND results and the radiogenic terrestrial heat

    Fiorentini, G; Mantovani, F; Ricci, B; Fiorentini, Gianni; Lissia, Marcello; Mantovani, Fabio; Ricci, Barbara


    We find that recent results from the KamLAND collaboration on geologically produced antineutrinos, N(U+Th) = 28+16-15 events, correspond to a radiogenic heat production from Uranium and Thorium decay chains H(U+Th) = 38+35-33 TW. The 99% confidence limit on the geo-neutrino signal translates into the upper bound H(U+Th) < 162 TW, which is much weaker than that claimed by KamLAND, H(U+Th) < 60 TW, based on a too narrow class of geological models. We also performed an analysis of KamLAND data including recent high precision measurements of the C13(\\alpha,n)O16 cross section. The result, N(U+Th) = 31+14-13, corroborates the evidence (approx 2.5\\sigma) for geo-neutrinos in KamLAND data.

  6. Quaternary naltrexone reverses radiogenic and morphine-induced locomotor hyperactivity

    Mickley, G.A.; Stevens, K.E.; Galbraith, J.A.; White, G.A.; Gibbs, G.L.


    The present study attempted to determine the relative role of the peripheral and central nervous system in the production of morphine-induced or radiation-induced locomotor hyperactivity of the mouse. Toward this end, we used a quaternary derivative of an opiate antagonist (naltrexone methobromide), which presumably does not cross the blood-brain barrier. Quaternary naltrexone was used to challenge the stereotypic locomotor response observed in these mice after either an i.p. injection of morphine or exposure to 1500 rads /sup 60/Co. The quaternary derivative of naltrexone reversed the locomotor hyperactivity normally observed in the C57BL/6J mouse after an injection of morphine. It also significantly attenuated radiation-induced locomotion. The data reported here support the hypothesis of endorphin involvement in radiation-induced and radiogenic behaviors. However, these conclusions are contingent upon further research which more fully evaluates naltrexone methobromide's capacity to cross the blood-brain barrier.

  7. Systematic study of heavy cluster emission from {sup 210-226}Ra isotopes

    Santhosh, K.P., E-mail: [School of Pure and Applied Physics, Kannur University, Payyanur Campus, Payyanur 670 327 (India); Sahadevan, Sabina; Priyanka, B.; Unnikrishnan, M.S. [School of Pure and Applied Physics, Kannur University, Payyanur Campus, Payyanur 670 327 (India)


    The half lives for various clusters lying in the cold reaction valleys of {sup 210-226}Ra isotopes are computed using our Coulomb and proximity potential model (CPPM). The computed half lives of {sup 4}He and {sup 14}C clusters from {sup 210-226}Ra isotopes are in good agreement with experimental data. Half lives are also computed using the universal formula for cluster decay (UNIV) of Poenaru et al., and are found to be in agreement with CPPM values. Our study reveals the role of doubly magic {sup 208}Pb daughter in cluster decay process. Geiger-Nuttall plots for all clusters up to {sup 62}Fe are studied and are found to be linear with different slopes and intercepts. {sup 12,14}C emission from {sup 220}Ra; {sup 14}C emission from {sup 222,224}Ra; {sup 14}C and {sup 20}O emission from {sup 226}Ra are found to be most favourable for measurement and this observation will serve as a guide to the future experiments.

  8. Carbon Isotope Systematics in Mineral-Catalyzed Hydrothermal Organic Synthesis Processes at High Temperature and Pressures

    Fu, Qi; Socki, R. A.; Niles, Paul B.


    Observation of methane in the Martian atmosphere has been reported by different detection techniques. Reduction of CO2 and/or CO during serpentization by mineral surface catalyzed Fischer-Tropsch Type (FTT) synthesis may be one possible process responsible for methane generation on Mars. With the evidence a recent study has discovered for serpentinization in deeply buried carbon rich sediments, and more showing extensive water-rock interaction in Martian history, it seems likely that abiotic methane generation via serpentinization reactions may have been common on Mars. Experiments involving mineral-catalyzed hydrothermal organic synthesis processes were conducted at 750 C and 5.5 Kbars. Alkanes, alcohols and carboxylic acids were identified as organic compounds. No "isotopic reversal" of delta C-13 values was observed for alkanes or carboxylic acids, suggesting a different reaction pathway than polymerization. Alcohols were proposed as intermediaries formed on mineral surfaces at experimental conditions. Carbon isotope data were used in this study to unravel the reaction pathways of abiotic formation of organic compounds in hydrothermal systems at high temperatures and pressures. They are instrumental in constraining the origin and evolution history of organic compounds on Mars and other planets.

  9. Proof of direct radiogenic destruction of collagen in vitro

    Acil, Y.; Springer, I.N.; Gassling, P.; Warnke, P.H.; Acmaz, S.; Soenmez, T.T.; Wiltfang, J. [Univ. Hospital Schleswig-Holstein, Kiel (Germany). Dept. of Oral and Maxillofacial Surgery; Niehoff, P.; Kimmig, B. [Univ. Hospital Schleswig-Holstein, Kiel (DE). Dept. of Radiotherapy (Radiooncology); Lefteris, V. [Univ. of Athens Medical School (Greece). Dept. of Oral and Maxillofacial Surgery


    Background: Fibroses of vessels and soft tissue are side effects of radiotherapy. The authors assumed that there was an immediate direct radiogenic damage of collagen of bone, periosteum and skin. Material and Methods: 15 porcine jaws samples (group 1) were exposed to a total dose of 60 Gy (cobalt-60, 2 Gy/day, five fractions/week). 15 jaws samples were stored accordingly (group 2, no irradiation, control). Collagen fragments of bone, periosteum and skin samples of groups 1 and 2 were isolated by ultrafiltration. Collagen types were characterized by SDS-PAGE measurement of the mature collagen cross-links hydroxylysylpyridinoline (HP) and lysylpyridinoline (LP) by high-performance liquid chromatography (HPLC) and analysis of hydroxyproline (Hyp) was used to determine the ratio of the amount of collagen fragments from irradiated as opposed to nonirradiated samples. Results: The concentrations of HP, LP and Hyp in ultrafiltrates of probes of irradiated bone, periosteum and skin were markedly increased (average factors for bone: 3.69, 1.84, and 3.40, respectively; average factors for periosteum: 1.55, 1.41, and 1.77, respectively; average factors for skin: 1.55, 1.60, and 2.23, respectively) as compared to nonirradiated probes. SDS-PAGE did show collagen types I and V in nonirradiated bone, I and III in nonirradiated skin, and I in nonirradiated periosteum samples. In irradiated samples, smeared bands illustrated fragmentation of the collagen molecule. Conclusion: The increased concentrations of HP, LP and Hyp in ultrafiltrates indicated increased concentrations of split collagen. Direct and instant radiogenic damage of (extracellular matrix of) bone, periosteum and skin tissue collagen could be demonstrated. (orig.)

  10. Isotopic and fluid-inclusion constraints on the formation of polymetallic vein deposits in the central Argentinian Patagonia

    Dejonghe, Léon; Darras, Benoît; Hughes, Guillermo; Muchez, Philippe; Scoates, James S.; Weis, Dominique


    The lead isotope compositions of galena and the fluid-inclusion systematics of nine barite-bearing polymetallic (Au, Ag, Pb, Zn) deposits of the central Argentinian Patagonia (Chubut and Rio Negro provinces) have been investigated to constrain the compositions and sources of the mineralizing fluids. Most of the deposits occur as veins, with less common wall-rock disseminations and/or stockworks, and are low-sulfidation epithermal deposits hosted in Jurassic volcanic rocks. Fluid-inclusion homogenization temperatures (Th) from quartz and sphalerite from the deposits fall within the range of 100-300 °C, with the highest measured average temperatures for the most eastern deposits (Mina Angela - 298 °C; Cañadón Bagual - 343 °C). The salinities of the hydrothermal fluids at all deposits were low to moderate (≤10.4 equiv. wt% NaCl). Three groups of ore deposits can be defined on the basis of 206Pb/204Pb ratios for galena and these show a general decrease from west to east (from 18.506 to 18.000). The central Argentinian Patagonia deposits have distinctly less radiogenic lead isotope compositions than similar deposits from Peru and Chile, except for the porphyry copper deposits of central and southern Peru. Galena from the Mina Angela deposit is characterized by very low radiogenic lead isotope compositions (18.000Precambrian basement. The geographic trend in lead isotope compositions of both galena and whole rocks indicates a crustal contribution which increases eastwards, also reflected in the strontium-neodymium isotope systematics of the host lavas. Finally, due to the lack of precise age determinations for the central Patagonian polymetallic deposits, a potential link with Andean porphyry copper systems remains an open question.

  11. Oxygen isotope systematics of gem corundum deposits in Madagascar: relevance for their geological origin

    Giuliani, Gaston; Fallick, Anthony; Rakotondrazafy, Michel; Ohnenstetter, Daniel; Andriamamonjy, Alfred; Ralantoarison, Théogène; Rakotosamizanany, Saholy; Razanatseheno, Marie; Offant, Yohann; Garnier, Virginie; Dunaigre, Christian; Schwarz, Dietmar; Mercier, Alain; Ratrimo, Voahangy; Ralison, Bruno


    The oxygen isotopic composition of gem corundum was measured from 22 deposits and occurrences in Madagascar to provide a gemstone geological identification and characterization. Primary corundum deposits in Madagascar are hosted in magmatic (syenite and alkali basalt) and metamorphic rocks (gneiss, cordieritite, mafic and ultramafic rocks, marble, and calc-silicate rocks). In both domains the circulation of fluids, especially along shear zones for metamorphic deposits, provoked in situ transformation of the corundum host rocks with the formation of metasomatites such as phlogopite, sakenite, and corundumite. Secondary deposits (placers) are the most important economically and are contained in detrital basins and karsts. The oxygen isotopic ratios (18O/16O) of ruby and sapphire from primary deposits are a good indicator of their geological origin and reveal a wide range of δ18O (Vienna Standard Mean Ocean Water) between 1.3 and 15.6‰. Metamorphic rubies are defined by two groups of δ18O values in the range of 1.7 to 2.9‰ (cordieritite) and 3.8 to 6.1‰ (amphibolite). “Magmatic” rubies from pyroxenitic xenoliths contained in the alkali basalt of Soamiakatra have δ18O values ranging between 1.3 and 4.7‰. Sapphires are classified into two main groups with δ18O in the range of 4.7 to 9.0‰ (pyroxenite and feldspathic gneiss) and 10.7 to 15.6‰ (skarn in marble from Andranondambo). The δ18O values for gem corundum from secondary deposits have a wide spread between -0.3 and 16.5‰. The ruby and sapphire found in placers linked to alkali basalt environments in the northern and central regions of Madagascar have consistent δ18O values between 3.5 and 6.9‰. Ruby from the placers of Vatomandry and Andilamena has δ18O values of 5.9‰, and between 0.5 and 4.0‰, respectively. The placers of the Ilakaka area are characterized by a huge variety of colored sapphires and rubies, with δ18O values between -0.3 and 16.5‰, and their origin is debated. A

  12. Stable isotope systematics of surface water bodies in the Himalayan and trans-Himalayan (Kashmir) region

    Kanchan Pandey; J T Padia; R Ramesh; K K Sharma


    Stable hydrogen (D) and oxygen (18O) isotope ratios of the headwaters of the Indus and its tributaries, surface ice in glaciers, saline and fresh water lakes and thermal springs in the Himalayan and Trans- Himalayan (Kashmir) region are reported. The D-18O relationship for the river samples shows a slope of 9.12 ± 0.29 which agrees well with the estimate of 8.99 ± 0.33 based on a simple Rayleigh fractionation model. The unique signature of a higher deuterium excess (d) of the `Western Disturbance' is preserved in these samples. An altitude effect of -0.9 per mil/km is observed in the 18O of Indus waters. At a lower altitude (Beas) the altitude effect is almost double, indicating that the altitude effect decreases with elevation in this region.

  13. Rhenium-osmium concentration and isotope systematics in group IIAB iron meteorites

    Morgan, J.W.; Horan, M.F.; Walker, R.J.; Grossman, J.N.


    Rhenium and osmium abundances, and osmium isotopic compositions were measured by negative thermal ionization mass spectrometry in thirty samples, including replicates, of five IIA and eight IIB iron meteorites. Log plots of Os vs. Re abundances for IIA and IIB irons describe straight lines that approximately converge on Lombard, which has the lowest Re and Os abundances and highest 187Re/188Os measured in a IIA iron to date. The linear IIA trend may be exactly reproduced by fractional crystallization, but is not well fitted using variable partition coefficients. The IIB iron trend, however, cannot be entirely explained by simple fractional crystallization. One explanation is that small amounts of Re and Os were added to the asteroid core during the final stages of crystallization. Another possibility is that diffusional enrichment of Os may have occurred in samples most depleted in Re and Os. -from Authors

  14. Systematic Study of Tensor Force Effect on Pseudospin Orbital Splittings in Sn Isotopes

    WANG; Yan-zhao; YU; Guo-liang; LI; Zhen-yu; GU; Jian-zhong


    <正>The tensor force is a noncentral and nonlocal spin-spin coupling term of the nucleon-nucleon interaction whose effect on the nuclear structure has been discussed in the framework of the self-consistent mean field approaches and the shell model in the past a few years. Based on the Skyrme Hartree-Fock-Bogoliubov approach, we systematically investigated the role of the tensor force on the

  15. Sulfur isotope systematics of microbial mats in shallow-sea hydrothermal vents, Milos Island, Greece

    Gilhooly, W. P.; Fike, D. A.; Amend, J. P.; Price, R. E.; Druschel, G.


    Milos is an island arc volcano venting submarine magmatic fluids directly into overlying seawater. Our study sites are located in an extensive shallow-water hydrothermal vent field less than 200 m offshore of Paleochori Bay in 5 m water depth. The vent fluids are highly sulfidic (> 3mM), at high-temperature (50-115C), and acidic (pH 5). The seafloor vent features include large patches (> 1 m2) of white microbial mats, patches of yellow elemental sulfur, and sediments stained orange by arsenic sulfides. The microbial communities that populate the shallow-sea hydrothermal vents stand in stark contrast to other nearshore environments typically found at wave base and within the photic zone. We explore sulfur isotope patterns along sharp environmental gradients established between ambient seawater and the efflux of vent fluids in the effort to better understand resource exploitation by microbial mat communities living in extreme conditions. Pore water samples, push-cores, biofilms, and water column samples were collected by SCUBA along sampling transects radiating out from the center of white mats into background sediments. We analyzed these samples for δ34S of dissolved sulfate, sulfide, elemental sulfur, and mineral sulfides (iron monosulfides and pyrite). Free gas sulfides collected directly from vents had δ34S values ranging +2.1 to +2.8%. Pore water sulfide, collected from below white mats with δ34S values ranging +1.9 to +2.9%, was isotopically similar to free gas samples. High pore water sulfate concentrations (8-25 mM) coupled with 34S-enriched pore water sulfides are not geochemical signatures indicative of dissimilatory sulfate reduction (where δ34Ssulfide <<0%). The δ34S of pore water sulfates collected across one dive site show a mixing trend, ranging from +18% in the center, +20% mid-transect, and +21% in sediments outside of the mat. This trend may be caused by oxidation of vent sulfides by entrained seawater (δ34S = +21.2%). We continue to target

  16. Boron isotope systematics during magma-carbonate interaction: an experimental study from Merapi (Indonesia) and Vesuvius (Italy)

    Deegan, F. M.; Jolis, E. M.; Troll, V. R.; Freda, C.; Whitehouse, M.


    Carbonate assimilation is increasingly recognized as an important process affecting the compositional evolution of magma and its inherent ability to erupt explosively due to release of carbonate-derived CO2 [e.g., 1, 2, 3]. In order to gain insights into this process, we performed short time-scale carbonate dissolution experiments in silicate melt using natural starting materials from Merapi and Vesuvius volcanoes at magmatic pressure and temperature [2, 4]. The experiments enable us to resolve in detail the timescales, textures and chemical features of carbonate assimilation. Three compositionally distinct glass domains have been defined: i) Ca-normal glass, similar in composition to the starting material; ii) Ca-rich, contaminated glass; and iii) a diffusional glass interface between the Ca-normal and Ca-rich glass, characterized by steady interchange between SiO2 and CaO. Here we present new boron isotope data for the experimental products obtained by SIMS. The glasses show distinct and systematic variation in their δ11B (%) values. The contaminated glasses generally show extremely negative δ11B values (down to -41 %) relative to both the uncontaminated experimental glass and fresh arc volcanics (-7 to +7 % [5]). Considering that carbonates have δ11B values of +9 to +26 [6], the data cannot be explained by simple mixing processes between the end-members alone. This implies that the δ11B of the original contaminant was drastically modified before being incorporated into the melt, which can be explained by B isotope fractionation during breakdown and degassing of the carbonate. Our data represents the first B isotope analyses of experimental products of carbonate assimilation. They provide novel and well constrained insights into the behavior of boron upon degassing of carbonate. This, in turn, has implications for both i) late stage contamination and volatile addition to hazardous volcanic systems located over carbonate basement (cf. [7]) and ii) studies of

  17. Highly Siderophile Elements and Osmium Isotope Systematics in Ureilites: Are the Carbonaceous Veins Primary Components?

    Rankenburg, K.; Brandon, A. D.; Humayun, M.


    Ureilites are an enigmatic group of primitive carbon-bearing achondrites of ultramafic composition. The majority of the 143 ureilite meteorites consist primarily of olivine and pyroxene (and occasionally chromite) [1]. They are coarse-grained, slowly cooled, and depleted in incompatible lithophile elements. Minor amounts of dark interstitial material consisting of carbon, metal, sulfides, and fine-grained silicates occur primarily along silicate grain boundaries, but also intrude the silicates along fractures and cleavage planes. Variable degrees of impact shock features have also been imparted on ureilites. The prevailing two origins proposed for these rocks are either as melting residues of carbonaceous chondritic material [2], [3], or alternatively, derivation as mineral cumulates from such melts [4], [5], [6]. It has recently been proposed that ureilites are the residues of a smelting event, i.e. residues of a partial melting event under highly reducing conditions, where a solid Fe-bearing phase reacts with a melt and carbon to form Fe metal and carbon monoxide [7]. Rapid, localized extraction and loss of the basaltic component into space resulting from high eruption velocities could preserve unequilibrated oxygen isotopes and produce the observed olivine-pyroxene residues via 25-30% partial melting of chondritic-like precursor material.

  18. Tracing slab dehydration using neon and argon isotope systematics in high pressure minerals

    Smye, A.; Jackson, C.; Parman, S. W.; Kelley, S. P.


    Mounting evidence suggests that noble gases are transported from Earth's surface reservoirs back into the mantle during subduction of oceanic lithosphere [e.g. 1]. Recent experiments [2] show that noble gases are relatively soluble in ring-structured minerals, such as amphibole, highlighting the potential for hydrated oceanic crust to control the input flux of noble gases into subduction zones. However, it is unclear whether the return flux of noble gases is controlled by mineral solubility alone or whether diffusive loss during subduction is important. Here, we address this issue by combining the solubility data with recently acquired He and Ne [3], and previously published Ar [4], diffusivity measurements in amphibole to parameterize a diffusion-solubility model, simulating noble gas fractionation during subduction. The model predicts that the light noble gases, He and Ne, are efficiently extracted from hot slabs at depths shallower than 50 km, whereas Ar and, by implication, Kr and Xe are retained in the slab past sub-arc depths. Conversely, cold slabs with low porosity volume fractions have the potential to recycle Ne. Our modelling shows that the Ne/Ar elemental ratio of slab minerals is strongly influenced by thermal regime and grain boundary porosity. We test these predictions against a new laser fusion dataset of Ne and Ar isotopic measurements in high-pressure minerals from a suite of exhumed high-pressure rocks that have experienced varying degrees of subduction and dehydration. Refs: [1] Holland, G. and Ballentine, C. (2006). Nature 441, 186-191. [2] Jackson et al. (2013). Nat.Geosci. 6, 562-565. [3] Jackson et al. submitted. [4] Harrison, T.M. (1981). CMP 78, 324-331.

  19. Systematization of cross sections for the production of residual nuclei on separated tin isotopes in reactions induced by various-energy protons

    Balabekyan, A. R., E-mail:; Danagulyan, A. S. [Yerevan State University (Armenia); Drnoyan, J. R.; Demekhina, N. A. [Joint Institute for Nuclear Research (Russian Federation); Hovhannisyan, G. H.; Simonyan, A. E. [Yerevan State University (Armenia); Adam, J.; Solnishkin, A. A.; Tsoupko-Sytnikov, V. M. [Joint Institute for Nuclear Research (Russian Federation)


    Cross sections for the production of residual nuclei on the isotopes {sup 112,118,120,124}Sn irradiated with 0.66-, 1.0-, 3.65-, and 8.1-GeV proton beams were investigated. A ten-parameter semiempirical formula was used to systematize the cross sections in question. A comparative analysis of parameter values obtained at different proton energies was performed.

  20. Osmium isotope and highly siderophile element systematics of the lunar crust

    Day, James M. D.; Walker, Richard J.; James, Odette B.; Puchtel, Igor S.


    Coupled 187Os/ 188Os and highly siderophile element (HSE: Os, Ir, Ru, Pt, Pd, and Re) abundance data are reported for pristine lunar crustal rocks 60025, 62255, 65315 (ferroan anorthosites, FAN) and 76535, 78235, 77215 and a norite clast in 15455 (magnesian-suite rocks, MGS). Osmium isotopes permit more refined discrimination than previously possible of samples that have been contaminated by meteoritic additions and the new results show that some rocks, previously identified as pristine, contain meteorite-derived HSE. Low HSE abundances in FAN and MGS rocks are consistent with derivation from a strongly HSE-depleted lunar mantle. At the time of formation, the lunar floatation crust, represented by FAN, had 1.4 ± 0.3 pg g - 1 Os, 1.5 ± 0.6 pg g - 1 Ir, 6.8 ± 2.7 pg g - 1 Ru, 16 ± 15 pg g - 1 Pt, 33 ± 30 pg g - 1 Pd and 0.29 ± 0.10 pg g - 1 Re (˜ 0.00002 × CI) and Re/Os ratios that were modestly elevated ( 187Re/ 188Os = 0.6 to 1.7) relative to CI chondrites. MGS samples are, on average, characterised by more elevated HSE abundances (˜ 0.00007 × CI) compared with FAN. This either reflects contrasting mantle-source HSE characteristics of FAN and MGS rocks, or different mantle-crust HSE fractionation behaviour during production of these lithologies. Previous studies of lunar impact-melt rocks have identified possible elevated Ru and Pd in lunar crustal target rocks. The new results provide no supporting evidence for such enrichments. If maximum estimates for HSE in the lunar mantle are compared with FAN and MGS averages, crust-mantle concentration ratios ( D-values) must be ≤ 0.3. Such D-values are broadly similar to those estimated for partitioning between the terrestrial crust and upper mantle, with the notable exception of Re. Given the presumably completely different mode of origin for the primary lunar floatation crust and tertiary terrestrial continental crust, the potential similarities in crust-mantle HSE partitioning for the Earth and Moon are

  1. Osmium isotope and highly siderophile element systematics of the lunar crust

    Day, J.M.D.; Walker, R.J.; James, O.B.; Puchtel, I.S.


    Coupled 187Os/188Os and highly siderophile element (HSE: Os, Ir, Ru, Pt, Pd, and Re) abundance data are reported for pristine lunar crustal rocks 60025, 62255, 65315 (ferroan anorthosites, FAN) and 76535, 78235, 77215 and a norite clast in 15455 (magnesian-suite rocks, MGS). Osmium isotopes permit more refined discrimination than previously possible of samples that have been contaminated by meteoritic additions and the new results show that some rocks, previously identified as pristine, contain meteorite-derived HSE. Low HSE abundances in FAN and MGS rocks are consistent with derivation from a strongly HSE-depleted lunar mantle. At the time of formation, the lunar floatation crust, represented by FAN, had 1.4 ?? 0.3 pg g- 1 Os, 1.5 ?? 0.6 pg g- 1 Ir, 6.8 ?? 2.7 pg g- 1 Ru, 16 ?? 15 pg g- 1 Pt, 33 ?? 30 pg g- 1 Pd and 0.29 ?? 0.10 pg g- 1 Re (??? 0.00002 ?? CI) and Re/Os ratios that were modestly elevated (187Re/188Os = 0.6 to 1.7) relative to CI chondrites. MGS samples are, on average, characterised by more elevated HSE abundances (??? 0.00007 ?? CI) compared with FAN. This either reflects contrasting mantle-source HSE characteristics of FAN and MGS rocks, or different mantle-crust HSE fractionation behaviour during production of these lithologies. Previous studies of lunar impact-melt rocks have identified possible elevated Ru and Pd in lunar crustal target rocks. The new results provide no supporting evidence for such enrichments. If maximum estimates for HSE in the lunar mantle are compared with FAN and MGS averages, crust-mantle concentration ratios (D-values) must be ??? 0.3. Such D-values are broadly similar to those estimated for partitioning between the terrestrial crust and upper mantle, with the notable exception of Re. Given the presumably completely different mode of origin for the primary lunar floatation crust and tertiary terrestrial continental crust, the potential similarities in crust-mantle HSE partitioning for the Earth and Moon are somewhat

  2. Comparative analysis of using natural and radiogenic lead as heat-transfer agent in fast reactors

    Laas, R. A.; Gizbrekht, R. V.; Komarov, P. A.; Nesterov, V. N.


    Fast reactors with lead coolant have several advantages over analogues. Performance can be further improved by replacement of natural composition lead with radiogenic one. Thus, two main issues need to be addressed: induced radioactivity in coolant and efficient neutron multiplication factor in the core will be changed and need to be estimated. To address these issues analysis of the scheme of the nuclear transformations in the lead heat-transfer agent in the process of radiation was carried out. Induced radioactivity of radiogenic and natural lead has been studied. It is shown that replacement of lead affects multiplication factor in a certain way. Application of radiogenic lead can significantly affect reactor operation.

  3. S- and Sr-isotopic compositions in barite-silica chimney from the Franklin Seamount, Woodlark Basin, Papua New Guinea: constraints on genesis and temporal variability of hydrothermal fluid

    Ray, Durbar; Banerjee, Ranadip; Balakrishnan, S.; Paropkari, Anil L.; Mukhopadhyay, Subir


    Isotopic ratios of strontium and sulfur in six layers across a horizontal section of a hydrothermal barite-silica chimney from Franklin Seamount of western Woodlark Basin have been investigated. Sr-isotopic ratios in barite samples (87Sr/86Sr = 0.70478-0.70493) are less radiogenic than seawater (87Sr/86Sr = 0.70917) indicating that substantial leaching of sub-seafloor magma was involved in the genesis of hydrothermal fluid. The SO2 of magma likely contributed a considerable amount of lighter S-isotope in fluid and responsible for the formation of barite, which is isotopically lighter (δ34S = 19.4-20.5 ‰) than modern seawater (δ34S ~ 21 ‰). The systematic changes in isotopic compositions across the chimney wall suggest temporal changes in the mode of mineral formation during the growth of the chimney. Enrichment of heavy S- and Sr-isotopes (δ34S = 20.58 ‰; 87Sr/86Sr = 0.70493) in the outermost periphery of the chimney indicates that, at the initial stage of chimney development, there was a significant contribution of seawater sulfate during barite mineralization. Thereafter, thickening of chimney wall occurred due to precipitation of fluid carrying more magmatic components relative to seawater. This led to a gradual enrichment of lighter isotopes (δ34S = 20.42-19.48 ‰; 87Sr/86Sr = 0.70491-0.704787) toward the inner portion of the chimney wall. In contrast, the innermost layer surrounding the fluid conduit is characterized by heavier and more radiogenic isotopes (δ34S = 20.3 ‰; 87Sr/86Sr = 0.7049). This suggests there was increasing influence of percolating seawater on the mineral paragenesis at the waning phase of the chimney development.

  4. Effects of Continental Weathering and Sedimentary Sorting on the Hf, Nd, and Pb Isotopic Composition of Sediments and Implications for Dissolved Input to the Ocean

    van de Flierdt, T.; Hemming, S. R.; Goldstein, S. L.


    The application of radiogenic isotopes of dissolved trace metals (Hf, Pb, Nd) in the ocean to study climate induced weathering changes on the continents is a relatively new and exciting field of research. Most studies on the radiogenic isotope composition of past seawater are based on chemical sediments such as ferromanganese crusts, and suggest a strong linkage in changes in the style of weathering (chemical vs. physical/glacial) on the continents and the isotopic composition of seawater for elements such as Hf and Pb. This is evidenced by records from the northwest Atlantic, which show significant changes in the Hf and Pb isotopic composition of seawater associated with the onset of Northern Hemisphere Glaciation (NHG) over the past 3 Myr. On the other hand, the impact of glacial weathering on the Nd isotopic composition of seawater is generally thought to be negligible. In order to better understand the systematics and mechanisms of weathering, erosion, and run-off, as well as their bearing on the isotopic composition of the ocean we choose the following strategy: sediments from the Amerilik and Gothabs Fjords near Nuuk (Greenland) have been analyzed for their bulk rock and grain size specific Hf, Nd, and Pb isotopic compositions (sand, silt, mud). Both Fjords are surrounded by early Archean gneisses, among the oldest rocks on Earth, and are filled with glacially floured sediments. Precambrian rocks surround a large fraction of the circum-North Atlantic area that was covered by ice sheets during the NHG, and the source rocks in this region are the most extreme examples. Current knowledge about the impact of weathering processes on isotope systematics implies that the largest changes in the Hf (and Pb) isotopic composition of seawater are expected to arise from glacial weathering of old continental sources. Our data reveal large differences in grain size specific isotope ratios, e.g. between the mud and sand fractions, for sediments with an old provenance

  5. Geology and D-O-C Isotope Systematics of the Tieluping Silver Deposit,Henan,China:Implications for Ore Genesis

    CHEN Yanjing; Franco PIRAJNO; SUI Yinghui


    The Tieluping silver deposit, which is sited along NE-trending faults within the high-grade metamorphic basement of the Xiong'er terrane, is part of an important Mesozoic orogenic-type Ag-Pb and Au belt recently discovered. Ore formation includes three stages: Early (E), Middle (M) and Late (L), which include quartz-pyrite (E),polymetallic sulfides (M) and carbonates (L), respectively. The E-stage fluids are characterized by δD=-90‰,δ13Cco2=2.0‰ and δ18O=9‰ at 373℃, and are deeply sourced; the L-stage fluids, with δD=-70‰,δ13Cco2=-1.3‰ and δ18O=-2‰, are shallow-sourced meteoric water; whereas the M-stage fluids, with δD=-109‰,δ13Cco2=0.1‰ and δ18O=2‰, are a mix of deep-sourced and shallow-sourced fluids. Comparisons of the D-O-C isotopic systematics of the Estage ore-forming fluids with the fluids derived from Mesozoic granites, Archean-Paleoproterozoic metamorphic basement and Paleo-Mesoproterozoic Xiong'er Group, show that these units cannot generate fluids with the measured isotopic composition (high δ18O and δ13C ratios and low δD ratios) characteristic of the ore-forming fluids. This suggests that the E-stage ore-forming fluids originated from metamorphic devolatilization of a carbonate-shale-chert lithological association, locally rich in organic matter, which could correspond to the Meso-Neoproterozoic Guandaokou and Luanchuan Groups, rather than to geologic units in the Xiong'er terrane, the lower crust and the mantle. This supports the view that the rocks of the Guandaokou and Luanchuan Groups south of the Machaoying fault might be the favorable sources. A tectonic model that combines collisional orogeny, metallogeny and hydrothermal fluid flow is proposed to explain the formation of the Tieluping silver deposit. During the Mesozoic collision between the South and North China paleocontinents, a crustal slab containing a lithological association consisting of carbonate-shale-chert, locally rich in organic matter (carbonaceous

  6. Identification of radiogenic heat source distribution in the crust: A variational approach

    R N Singh; Ajay Manglik


    Radiogenic heat sources present in the continental crust contribute significantly to the total surface heat flow and temperature distribution in the crust. Various modelsforthe depth distribution of radiogenic sources have been proposed. Among these modelsthe exponential model has been shown to be an optimal, smooth model through the variational approach applied to the heat conduction equation. In the present work, a two-layered model of the crust is considered and heat transport by advection is included in the upper layer. The heat transport in the lower layer is by conduction only. Application of variational principle determines the nature of the radiogenic source distribution in both the layers. The resultsthus obtained indicate a radiogenic source distribution which is more complex than a simple exponential model.

  7. On the valency state of radiogenic lead in zircon and its consequences

    Kramers, J.; Frei, Robert; Newville, M.


    at this temperature, show age effects that should have been observed in SIMS dating. Further, in zircon evaporation as well as in leaching experiments, common Pb is generally released preferentially to radiogenic Pb. After removal of less radiogenic Pb, the evaporation record generally shows pure radiogenic Pb during...... not resemble that of PbO2. The arguments why radiogenic Pb should be tetravalent are based on analogies with studies relating to the tetravalent state of 234Th and the hexavalent state of 234U, which show that a-recoil in silicates generates a strongly oxidizing environment at the site where the recoiling......-recoil damaged sites could be leached out by any electrolyte solution that reduces it to the divalent state, making it both incompatible and soluble. Thus, discordia can be generated in weathering. The curious observation that discordant Archaean zircon suites generally define trends to lower intercepts at up...

  8. Entropy-information perspective to radiogenic heat distribution in continental crust

    R. N. Singh


    Full Text Available Depth distribution of radiogenic heat sources in continental crust is an important parameter that controls its thermal structure as well as the mantle heat flow at the base of continental lithosphere. Various models for the depth distribution of radiogenic heat sources have been proposed. Starting from constant and exponential models based on linear heat flow–heat generation relationship the present-day layered models integrate crustal structure and laboratory measurements of radiogenic heat sources in various exposed rocks representing crustal composition. In the present work, an extended entropy theory formalism is used for estimation of radiogenic heat sources distribution in continental crust based on principle of maximum entropy (POME. The extended entropy principle yields a constant heat generation model if only a constraint given by total radiogenic heat in the crust is used and an exponential form of radiogenic heat sources distribution if an additional constraint in the form of a second moment is used in the minimization of entropy.

  9. Consistent evaluations of (n,2n) and (n,np) reaction excitation functions for some even-even isotopes using empirical systematics

    Manokhin, Vassily N. [Russian Nuclear Data Center, Institute of Physics and Power Engineering, Obninsk (Russian Federation); Odano, Naoteru; Hasegawa, Akira [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment


    An approach for consistent evaluation of (n,2n) and (n,np) reaction excitation functions for some even-even isotopes with the (n,np) reaction thresholds lower than (n,2n) reaction ones is described. For determination of cross sections in the maximum of the (n,2n) and (n,np) reaction excitation functions some empirical systematics developed by Manokhin were used together with trends in dependence of gaps between the (n,2n) and (n,np) thresholds on atomic mass number A. The shapes of the (n,2n) and (n,np) reaction excitation functions were calculated using the normalized functions from the Manokhin's systematics. Excitation functions of (n,2n) and (n,np) reactions were evaluated for several nuclei by using the systematics and it was found that the approach used for the present study gives reasonable results. (author)

  10. Strontium and neodymium isotope systematics of target rocks and impactites from the El'gygytgyn impact structure: Linking impactites and target rocks

    Wegner, Wencke; Koeberl, Christian


    The 3.6 Ma El'gygytgyn structure, located in northeastern Russia on the Chukotka Peninsula, is an 18 km diameter complex impact structure. The bedrock is formed by mostly high-silica volcanic rocks of the 87 Ma old Okhotsk-Chukotka Volcanic Belt (OCVB). Volcanic target rocks and impact glasses collected on the surface, as well as drill core samples of bedrock and impact breccias have been investigated by thermal ionization mass spectrometry (TIMS) to obtain new insights into the relationships between these lithologies in terms of Nd and Sr isotope systematics. Major and trace element data for impact glasses are added to compare with the composition of target rocks and drill core samples. Sr isotope data are useful tracers of alteration processes and Nd isotopes reveal characteristics of the magmatic sources of the target rocks, impact breccias, and impact glasses. There are three types of target rocks mapped on the surface: mafic volcanics, dacitic tuff and lava of the Koekvun' Formation, and dacitic to rhyolitic ignimbrite of the Pykarvaam Formation. The latter represents the main contributor to the impact rocks. The drill core is divided into a suevite and a bedrock section by the Sr isotope data, for which different postimpact alteration regimes have been detected. Impact glasses from the present-day surface did not suffer postimpact hydrothermal alteration and their data indicate a coherent alteration trend in terms of Sr isotopes with the target rocks from the surface. Surprisingly, the target rocks do not show isotopic coherence with the Central Chukotka segment of the OCVB or with the Berlozhya magmatic assemblage (BMA), a late Jurassic felsic volcanic suite that crops out in the eastern part of the central Chukotka segment of the OCVB. However, concordance for these rocks exists with the Okhotsk segment of the OCVB. This finding argues for variable source magmas having contributed to the build-up of the OCVB.

  11. Radiogenic and Stable Isotope and Hydrogeochemical Investigation of Groundwater, Pajarito Plateau and Surrounding Areas, New Mexico

    Patrick Longmire, Michael Dale, Dale Counce, Andrew Manning, Toti Larson, Kim Granzow, Robert Gray, and Brent Newman


    From October 2004 through February 2006, Los Alamos National Laboratory, the New Mexico Environment Department-Department of Energy Oversight Bureau, and the United States Geological Survey conducted a hydrochemical investigation. The purpose of the investigation was to evaluate groundwater flow paths and determine groundwater ages using tritium/helium-3 and carbon-14 along with aqueous inorganic chemistry. Knowledge of groundwater age and flow paths provides a technical basis for selecting wells and springs for monitoring. Groundwater dating is also relevant to groundwater resource management, including aquifer sustainability, especially during periods of long-term drought. At Los Alamos, New Mexico, groundwater is either modern (post-1943), submodern (pre-1943), or mixed (containing both pre- and post-1943 components). The regional aquifer primarily consists of submodern groundwater. Mixed-age groundwater results from initial infiltration of surface water, followed by mixing with perched alluvial and intermediate-depth groundwater and the regional aquifer. No groundwater investigation is complete without using tritium/helium-3 and carbon-14 dating methods to quantify amounts of modern, mixed, and/or submodern components present in samples. Computer models of groundwater flow and transport at Los Alamos should be calibrated to groundwater ages for perched intermediate zones and the regional aquifer determined from this investigation. Results of this study clearly demonstrate the occurrence of multiple flow paths and groundwater ages occurring within the Sierra de los Valles, beneath the Pajarito Plateau, and at the White Rock Canyon springs. Localized groundwater recharge occurs within several canyons dissecting the Pajarito Plateau. Perched intermediate-depth groundwater and the regional aquifer beneath Pueblo Canyon, Los Alamos Canyon, Sandia Canyon, Mortandad Canyon, Pajarito Canyon, and Canon de Valle contain a modern component. This modern component consists of tritium, nitrate, perchlorate, chromate, boron, uranium, and/or high explosive compounds. It is very unlikely that there is only one transport or travel time, ranging from 25 to 62 years, for these conservative chemicals migrating from surface water to the regional water table. Lengths of groundwater flow paths vary within deep saturated zones containing variable concentrations of tritium. The 4-series springs discharging within White Rock Canyon contain a modern component of groundwater, primarily tritium. Average groundwater ages for the regional aquifer beneath the Pajarito Plateau varied from 565 to 10,817 years, based on unadjusted carbon-14 measurements.

  12. Origin of the mysterious Yin-Shang bronzes in China indicated by lead isotopes

    Sun, Wei-dong; Zhang, Li-peng; Guo, Jia; Li, Cong-ying; Jiang, Yu-hang; Zartman, Robert E.; Zhang, Zhao-feng


    Fine Yin-Shang bronzes containing lead with puzzlingly highly radiogenic isotopic compositions appeared suddenly in the alluvial plain of the Yellow River around 1400 BC. The Tongkuangyu copper deposit in central China is known to have lead isotopic compositions even more radiogenic and scattered than those of the Yin-Shang bronzes. Most of the Yin-Shang bronzes are tin-copper alloys with high lead contents. The low lead and tin concentrations, together with the less radiogenic lead isotopes of bronzes in an ancient smelting site nearby, however, exclude Tongkuangyu as the sole supplier of the Yin-Shang bronzes. Interestingly, tin ingots/prills and bronzes found in Africa also have highly radiogenic lead isotopes, but it remains mysterious as to how such African bronzes may have been transported to China. Nevertheless, these African bronzes are the only bronzes outside China so far reported that have lead isotopes similar to those of the Yin-Shang bronzes. All these radiogenic lead isotopes plot along ~2.0–2.5 Ga isochron lines, implying that deposits around Archean cratons are the most likely candidates for the sources. African cratons along the Nile and even micro-cratons in the Sahara desert may have similar lead signatures. These places were probably accessible by ancient civilizations, and thus are the most favorable suppliers of the bronzes. PMID:26988425

  13. Lead isotopes in iron and manganese oxide coatings and their use as an exploration guide for concealed mineralization

    Gulson, B.L.; Church, S.E.; Mizon, K.J.; Meier, A.L.


    Lead isotopes from Fe and Mn oxides that coat stream pebbles from around the Mount Emmons porphyry molybdenum deposit in Colorado were studied to assess the feasibility of using Pb isotopes to detect concealed mineral deposits. The Fe/Mn oxide coatings were analyzed to determine their elemental concentrations using ICP-AES. The Pb isotope compositions of solutions from a selected suite of samples were measured, using both thermal ionization and ICP mass spectrometry, to compare results determined by the two analytical methods. Heavy mineral concentrates from the same sites were also analyzed to compare the Pb isotope compositions of the Fe/Mn coatings with those found in panned concentrates. The Fe/Mn and 206Pb/204Pb ratios of the oxide coatings are related to the lithology of the host rocks; Fe/Mn oxide coatings on pebbles of black shale have higher Fe/Mn values than do the coatings on either sandstone or igneous rocks. The shale host rocks have a more radiogenic signature (e.g. higher 206Pb/ 204Pb) than the sandstone or igneous host rocks. The Pb isotope data from sandstone and igneous hosts can detect concealed mineralized rock on both a regional and local scale, even though there are contributions from: (1) metals from the main-stage molybdenite ore deposit; (2) metals from the phyllic alteration zone which has a more radiogenic Pb isotope signature reflecting hydrothermal leaching of Pb from the Mancos Shale; (3) Pb-rich base metal veins with a highly variable Pb isotope signature; and (4) sedimentary country rocks which have a more radiogenic Pb isotope signature. An investigation of within-stream variation shows that the Pb isotope signature of the molybdenite ore zone is retained in the Fe/Mn oxide coatings and is not camouflaged by contributions from Pb-rich base-metal veins that crop out upstream. In another traverse, the Pb isotope data from Fe/Mn oxide coatings reflect a complex mixing of Pb from the molybdenite ore zone and its hornfels margin, Pb

  14. Evaluation of the age related systematic patterns of stable oxygen and carbon isotope values of Swiss stone pine (Pinus cembra L.) Eastern Carpathians, Romania

    Nagavciuc, Viorica; Popa, Ionel; Persoiu, Aurel; Kern, Zoltán


    Tree-ring derived stable isotope time series are becoming increasingly important parameters in investigation of past environmental changes. However, potential age related trend-bias on these parameters, and the proper handling of it, is still not well understood. We here present measurements on a new multicentennial data set of annually resolved stable oxygen (δ18O) and carbon (δ13C) isotope compositions from 3 living and 4 subfossil Stone pine (Pinus cembra) samples collected at a timberline habitat in the Eastern Carpathians (Romania) to evaluate any potential systematic ontogenetic pattern on their δ18O and δ13C data. Oldest analyzed ring represented 129th, 135th and 142th cambial year in the living and 115th, 130th, 165th and 250th cambial year in the subfossil samples. The fact that Stone pine samples are backbone of the longest dendrochronological series both in the Alps and the Carpathians arouses special interest concerning their potential in stable isotope dendroclimatological research. Whole-ring samples were prepared to alpha-cellulose by the modified Jayme-Wise method. Cellulose samples were analyzed by a high-temperature pyrolysis system (Thermo Quest TC-EA) coupled to an isotope ratio mass spectrometer (Thermo Finningan Delta V). A ring by ring (i.e., non-pooled) approach was followed since age-related trends are by definition intrinsic to individual tree-ring series so pooling of rings may distort the detection of the trends. Raw measured δ13C values have been corrected for changes in the atmospheric CO2 regarding both its stable isotope signature and mixing ratio. Neither isotopic parameter showed any age related variance bias suggesting a homoscedastic character. Alignment of the δ13C data by cambial age revealed a relatively short period (~40 years) of systematic behaviour manifested in a ~1‰ enrichment in 13C over a moderate but persistent positive trend (~0.33‰ per 100years, p<10-10) can be observed for carbon discrimination afterwards

  15. Determining Carbon and Oxygen Stable Isotope Systematics in Brines at Elevated p/T Conditions to Enhance Monitoring of CO2 Induced Processes in Carbon Storage Reservoirs

    Becker, V.; Myrttinen, A.; Mayer, B.; Barth, J. A.


    Stable carbon isotope ratios (δ13C) are a powerful tool for inferring carbon sources and mixing ratios of injected and baseline CO2 in storage reservoirs. Furthermore, CO2 releasing and consuming processes can be deduced if the isotopic compositions of end-members are known. At low CO2 pressures (pCO2), oxygen isotope ratios (δ18O) of CO2 usually assume the δ18O of the water plus a temperature-dependent isotope fractionation factor. However, at very high CO2 pressures as they occur in CO2 storage reservoirs, the δ18O of the injected CO2 may in fact change the δ18O of the reservoir brine. Hence, changing δ18O of brine constitutes an additional tracer for reservoir-internal carbon dynamics and allows the determination of the amount of free phase CO2 present in the reservoir (Johnson et al. 2011). Further systematic research to quantify carbon and oxygen isotope fractionation between the involved inorganic carbon species (CO2, H2CO3, HCO3-, CO32-, carbonate minerals) and kinetic and equilibrium isotope effects during gas-water-rock interactions is necessary because p/T conditions and salinities in CO2 storage reservoirs may exceed the boundary conditions of typical environmental isotope applications, thereby limiting the accuracy of stable isotope monitoring approaches in deep saline formations (Becker et al. 2011). In doing so, it is crucial to compare isotopic patterns observed in laboratory experiments with artificial brines to similar experiments with original fluids from representative field sites to account for reactions of dissolved inorganic carbon (DIC) with minor brine components. In the CO2ISO-LABEL project, funded by the German Ministry for Education and Research, multiple series of laboratory experiments are conducted to determine the influence of pressure, temperature and brine composition on the δ13C of DIC and the δ18O of brines in water-CO2-rock reactions with special focus placed on kinetics and stable oxygen and carbon isotope fractionation

  16. Isotopic Systematics (U, nitrate and Sr) of the F-Area Acidic Contamination Plume at the Savannah River Site: Clues to Contaminant History and Mobility

    Christensen, J. N.; Conrad, M. E.; Bill, M.; Denham, M.; Wan, J.; Rakshit, S.; Stringfellow, W. T.; Spycher, N.


    reduction processes. In detail, the variation in the isotopic composition of F-Area nitrate does not support biologic denitrification within the plume. However, the isotopic composition of a surface water sample is consistent with denitrification occurring along the flow path between the plume seep-line and the surface stream. Strontium from F-Area groundwater samples covers a wide range in concentration (<<20 to 145 ppb) and 87Sr/86Sr (0.7096 to 0.7133). There is no systematic relationship between 87Sr/86Sr & 90Sr or 1/[Sr] suggesting possible Sr exchange with clays minerals. The isotopic compositions of groundwater and porewater samples vary systematically with sampling depth below the water table as illustrated by U isotopic data for depth discrete porewater samples and the δ15N of well samples. There appears to be a shallow zone within the top 10 ft of the aquifer, defined by reversals in the trends of U isotopic data and nitrate δ18O.

  17. Coupled Hf-Nd-Pb isotope co-variations of HIMU oceanic island basalts from Mangaia, Cook-Austral islands, suggest an Archean source component in the mantle transition zone

    Nebel, Oliver; Arculus, Richard J.; van Westrenen, Wim; Woodhead, Jon D.; Jenner, Frances E.; Nebel-Jacobsen, Yona J.; Wille, Martin; Eggins, Stephen M.


    Although it is widely accepted that oceanic island basalts (OIB) sample geochemically distinct mantle reservoirs including recycled oceanic crust, the composition, age, and locus of these reservoirs remain uncertain. OIB with highly radiogenic Pb isotope signatures are grouped as HIMU (high-μ, with μ = 238U/204Pb), and exhibit unique Hf-Nd isotopic characteristics, defined as ΔɛHf, deviant from a terrestrial igneous rock array that includes all other OIB types. Here we combine new Hf isotope data with previous Nd-Pb isotope measurements to assess the coupled, time-integrated Hf-Nd-Pb isotope evolution of the most extreme HIMU location (Mangaia, French Polynesia). In comparison with global MORB and other OIB types, Mangaia samples define a unique trend in coupled Hf-Nd-Pb isotope co-variations (expressed in 207Pb/206Pb vs. ΔɛHf). In a model employing subducted, dehydrated oceanic crust, mixing between present-day depleted MORB mantle (DMM) and small proportions (˜5%) of a HIMU mantle endmember can re-produce the Hf-Nd-Pb isotope systematics of global HIMU basalts (sensu stricto; i.e., without EM-1/EM-2/FOZO components). An age range of 3.5 to affected by other enriched mantle endmembers (sensu lato). If correct, this requires isolation of parts of the mantle transition zone for >3 Gyr and implies that OIB chemistry can be used to test geodynamic models.

  18. Sr, Nd, Pb and Li isotope geochemistry and Ar-Ar dating of alkaline lavas from northern James Ross Island (Antarctic Peninsula) - implications for back-arc magma formation

    Kosler, J.; Magna, T.; Mlcoch, B.; Mixa, P.; Hendriks, B. W. H.; Holub, F. V.; Nyvlt, D.


    The elemental and isotopic (Sr, Nd, Pb and Li) composition of Cenozoic back-arc alkaline basalts emplaced east of the Antarctic Peninsula in James Ross Island Volcanic Group (JRIVG) is different from the compositions of the fore-arc alkaline volcanic rocks in Southern Shetlands and nearby Bransfield Strait. The variability in elemental and isotopic composition is not consistent with the JRIVG derivation from a single mantle source but rather it suggests that the magma was mainly derived from a depleted mantle with subordinate OIB-like enriched mantle component (EM II). The isotopic data are consistent with mantle melting during extension and possible roll-back of the subducted lithosphere of the Antarctic plate in Miocene to Pliocene times, as indicated by the existing geochronological data and the new Ar-Ar age determinations. Magma contamination by Triassic - Early Tertiary clastic sediments deposited in the back-arc basin was only localized and affected Li isotopic composition in two of the samples, while most of the basalts show very little variation in delta 7Li values, as anticipated for "mantle-driven" Li isotopic composition. These variations are difficult to resolve with radiogenic isotope systematics but Li isotopes may prove sensitive in tracking complex geochemical processes acting through the oceanic crust pile, including hydrothermal leaching and seawater equilibration.

  19. Isotope systematics of a juvenile intraplate volcano: Pb, Nd, and srisotope ratios of basalts from Loihi Seamount, Hawaii

    Staudigel, H. (Columbia Univ., Palisades, NY (USA). Lamont-Doherty Geological Observatory; Scripps Institution of Oceanography, La Jolla, CA (USA)); Zindler, A.; Leslie, T. (Columbia Univ., Palisades, NY (USA). Lamont-Doherty Geological Observatory); Hart, S.R.; Chen, C.Y. (Massachusetts Inst. of Tech., Cambridge (USA). Dept. of Earth and Planetary Sciences); Clague, D. (Geological Survey, Menlo Park, CA (USA))


    Sr, Nd, and Pb isotope ratios for a representative suite of 15 basanites, alkali basalts, transitional basalts and tholeiites from Loihi Seamount, Hawaii, display unusually large variations for a single volcano, but lie within known ranges for Hawaiian basalts. Nd isotope ratios in alkali basalts show the largest relative variation (0.51291 - 0.51305), and include the nearly constant tholeiite value (approx.= 0.51297). Pb isotope ratios show similarly large ranges for tholeiites and alkali basalts and continue Tatsumoto's (31) 'Loa' trend towards higher /sup 206/Pb//sup 204/Pb, ratios, resulting in a substantial overlap with the 'Kea' trend. /sup 206/Pb//sup 204/Pb ratios for Loihi and other volcanoes along the Loa and Kea trends (31) are observed to correlate with the age of the underlying lithosphere suggesting lithosphere involvement in the formation of Hawaiian tholeiites. Loihi lavas display no correlation of Nd, Sr, or Pb isotope ratios with major element compositions or eruptive age, in contrast with observations of some other Hawaiian volcanoes. Isotope data for Loihi, as well as average values for Hawaiian volcanoes, are not adequately explained by previously proposed two-end-member models; new models for the origin and the development of Hawaiian volcanoes must include mixing of at least three geochemically distinct source regions and allow for the involvement of heterogeneous oceanic lithosphere.

  20. Extreme heterogeneity in Sr isotope systematic in the Himalayan leucogranites: A possible mechanism of partial melting based on thermal modeling

    Dilip K Mukhopadhyay


    The small leucogranite plutons occurring in linear belts in the Higher Himalayas have formed due to post-collision partial melting within the Himalayan crust. Several studies have documented that the Sr isotopic ratios in the granite bodies show chaotic variation and meaningful Rb-Sr isochron ages are difficult, if not impossible, to obtain. In tectonically overthickened crust, the depth-temperature profile (geotherm) remains strongly transient for the first tens of millions of years. It is proposed here that the intersecting relations between the transient geotherms and activity-dependent solidus/melting curves may generate small pods of magma at di erent depths and at di erent times. Each of these pods will have its unique Sr isotopic ratios. Coalescence of these small pods of magma without any e ective homogenization due to deformation-induced fast segregation, ascent and emplacement may lead to pluton-wide extreme heterogeneity in Sr isotopic ratios.

  1. Microscopic study of low-lying yrast spectra and deformation systematics in neutron-rich 98−106Sr isotopes

    Anil Chandan; Suram Singh; Arun Bharti; S K Khosa


    Variation-after-projection (VAP) calculations in conjunction with Hartree–Bogoliubov (HB) ansatz have been carried out for = 98–106 strontium isotopes. In this framework, the yrast spectra with ≥ 10+, (2) transition probabilities, quadrupole deformation parameter and occupation numbers for various shell model orbits have been obtained. The results of the calculation for yrast spectra give an indication that it is important to include the hexadecapole–hexadecapole component of the two-body interaction for obtaining various nuclear structure quantities in Sr isotopes. Besides this, it is also found that the simultaneous polarization of 3/2 and 5/2 proton subshells is a significant factor in making a sizeable contribution to the deformation in neutron-rich Sr isotopes.

  2. Rb-Sr Isotopic Systematics of Alkali-Rich Fragments in the Yamato-74442 LL-Chondritic Breccia

    Yokoyama, T.; Misawa, K.; Okano, O.; Shih, C.-Y.; Nyquist, L. E.; Simo, J. I.; Tappa, M. J.; Yoneda, S.


    Alkali-rich igneous fragments were identified in the brecciated LL-chondrites, Kr henberg (LL5)], Bhola (LL3-6) and Yamato (Y)-74442 (LL4), and show characteristic fractionation patterns of alkaline elements. The K-Rb-Cs-rich fragments in Kr henberg, Bhola, and Y-74442 are very similar in mineralogy and petrography (olivine + pyroxene + glass), suggesting that they could have come from related precursor materials. We have undertaken Rb-Sr isotopic studies on alkali-rich fragments in Y-74442 to precisely determine their crystallization ages and the isotopic signatures of their precursor material(s).

  3. Uranium-lead isotope systematics and apparent ages of zircons and other minerals in precambrian granitic rocks, Granite Mountains, Wyoming

    Ludwig, K. R.; Stuckless, J.S.


    Zircon suites from the two main types of granite in the Granite Mountains, Wyoming, yielded concordia-intercept ages of 2,640??20 m.y. for a red, foliated granite (granite of Long Creek Mountain) and 2,595??40 m.y. for the much larger mass of the granite of Lankin Dome. These ages are statistically distinct (40??20 m.y. difference) and are consistent with observed chemical and textural differences. The lower intercepts of the zircon chords of 50??40 and 100+ 75 m.y. for the granite of Long Creek Mountain and granite of Lankin Dome, respectively, are not consistent with reasonable continuous diffusion lead-loss curves but do correspond well with the known (Laramide) time of uplift of the rocks. Epidote, zircon, and apatite from silicified and epidotized zones in the granites all record at least one postcrystallization disturbance in addition to the Laramide event and do not define a unique age of silicification and epidotization. The lower limit of ???2,500 m.y. provided by the least disturbed epidote, however, suggests that these rocks were probably formed by deuteric processes shortly after emplacement of the granite of the Lankin Dome. The earlier of the two disturbances that affected the minerals of the silicified-epidotized rock can be bracketed between 1,350 and 2,240 m.y. ago and is probably the same event that lowered mineral K-Ar and ages in the region. Zircon suites from both types of granite show well-defined linear correlations among U content, common-Pb content, and degree of discordance. One of the zircon suites has an extremely high common-Pb content (up to 180 ppm) and exhibits a component of radiogenic-Pb loss that is apparently unrelated to radiation damage. ?? 1978 Springer-Verlag.

  4. Shell Model Embedded in the Continuum for Binding Systematics in Neutron-Rich Isotopes of Oxygen and Fluor

    Luo, Y; Ploszajczak, M; Michel, N


    Continuum coupling correction to binding energies in the neutron rich oxygen and fluorine isotopes is studied using the Shell Model Embedded in the Continuum. We discuss the importance of different effects, such as the position of one-neutron emission threshold, the effective interaction or the number of valence particles on the magnitude of this correction.

  5. Sr-Nd-Pb-Hf isotope systematics of the Hugo Dummett Cu-Au porphyry deposit (Oyu Tolgoi, Mongolia)

    Dolgopolova, A.; Seltmann, R.; Armstrong, R.; Belousova, E.; Pankhurst, R. J.; Kavalieris, I.


    Major and trace element geochemistry including Sr-Nd-Pb-Hf isotopic data are presented for a representative sample suite of Late Devonian to Early Carboniferous plutonic and volcanic rocks from the Hugo Dummett deposit of the giant Oyu Tolgoi porphyry Cu-Au district in South Gobi, Mongolia. Sr and Nd isotopes (whole-rock) show restricted ranges of initial compositions, with positive ɛNdt mainly between + 3.4 and + 7.4 and (87Sr/86Sr)t predominantly between 0.7037 and 0.7045 reflecting magma generation from a relatively uniform juvenile lithophile-element depleted source. Previously dated zircons from the plutonic rocks exhibit a sample-averaged range of ɛHft values of + 11.6 to + 14.5. Depleted-mantle model ages of 420-830 (Nd) and 320-730 Ma (zircon Hf) limit the involvement of pre-Neoproterozoic crust in the petrogenesis of the intermediate to felsic calc-alkaline magmas to, at most, a minor role. Pb isotopes (whole-rock) show a narrow range of unradiogenic initial compositions: 206Pb/204Pb 17.40-17.94, 207Pb/204Pb 15.43-15.49 and 208Pb/204Pb 37.25-37.64, in agreement with Sr-Nd-Hf isotopes indicating the dominance of a mantle component. All four isotopic systems suggest that the magmas from which the large Oyu Tolgoi porphyry system was generated originated predominantly from juvenile material within the subduction-related setting of the Gurvansayhan terrane.

  6. Re-Os and Lu-Hf isotopic constraints on the formation and age of mantle pyroxenites from the Bohemian Massif

    Ackerman, Lukáš; Bizimis, Michael; Haluzová, Eva; Sláma, Jiří; Svojtka, Martin; Hirajima, Takao; Erban, Vojtěch


    We report on the Lu-Hf and Re-Os isotope systematics of a well-characterized suite of spinel and garnet pyroxenites from the Gföhl Unit of the Bohemian Massif (Czech Republic, Austria). Lu-Hf mineral isochrons of three pyroxenites yield undistinguishable values in the range of 336-338 Ma. Similarly, the slope of Re-Os regression for most samples yields an age of 327 ± 31 Ma. These values overlap previously reported Sm-Nd ages on pyroxenites, eclogites and associated peridotites from the Gföhl Unit, suggesting contemporaneous evolution of all these HT-HP rocks. The whole-rock Hf isotopic compositions are highly variable with initial εHf values ranging from - 6.4 to + 66. Most samples show a negative correlation between bulk rock Sm/Hf and εHf and, when taking into account other characteristics (e.g., high 87Sr/86Sr), this may be explained by the presence of recycled oceanic sediments in the source of the pyroxenite parental melts. A pyroxenite from Horní Kounice has decoupled Hf-Nd systematics with highly radiogenic initial εHf of + 66 for a given εNd of + 7.8. This decoupling is consistent with the presence of a melt derived from a depleted mantle component with high Lu/Hf. Finally, one sample from Bečváry plots close to the MORB field in Hf-Nd isotope space consistent with its previously proposed origin as metamorphosed oceanic gabbro. Some of the websterites and thin-layered pyroxenites have variable, but high Os concentrations paralleled by low initial γOs. This reflects the interaction of the parental pyroxenitic melts with a depleted peridotite wall rock. In turn, the radiogenic Os isotope compositions observed in most pyroxenite samples is best explained by mixing between unradiogenic Os derived from peridotites and a low-Os sedimentary precursor with highly radiogenic 187Os/188Os. Steep increase of 187Os/188Os at nearly uniform 187Re/188Os found in a few pyroxenites may be connected with the absence of primary sulfides, but the presence of minor

  7. Radiogenic heat production in sedimentary rocks of the Gulf of Mexico Basin, south Texas

    McKenna, T.E.; Sharp, J.M.


    Radiogenic heat production within the sedimentary section of the Gulf of Mexico basin is a significant source of heat. Radiogenic heat should be included in thermal models of this basin (and perhaps other sedimentary basins). We calculate that radiogenic heat may contribute up to 26% of the overall surface heat-flow density for an area in south Texas. Based on measurements of the radioactive decay rate of ??-particles, potassium concentration, and bulk density, we calculate radiogenic heat production for Stuart City (Lower Cretaceous) limestones, Wilcox (Eocene) sandstones and mudrocks, and Frio (Oligocene) sandstones and mudrocks from south Texas. Heat production rates range from a low of 0.07 ?? 0.01 ??W/m3 in clean Stuart City limestones to 2.21 ?? 0.24??W/m3 in Frio mudrocks. Mean heat production rates for Wilcox sandstones, Frio sandstones, Wilcox mudrocks, and Frio mudrocks are 0.88, 1.19, 1.50, and 1.72 ??W/m3, respectively. In general, the mudrocks produce about 30-40% more heat than stratigraphically equivalent sandstones. Frio rocks produce about 15% more heat than Wilcox rocks per unit volume of clastic rock (sandstone/mudrock). A one-dimensional heat-conduction model indicates that this radiogenic heat source has a significant effect on subsurface temperatures. If a thermal model were calibrated to observed temperatures by optimizing basal heat-flow density and ignoring sediment heat production, the extrapolated present-day temperature of a deeply buried source rock would be overestimated.Radiogenic heat production within the sedimentary section of the Gulf of Mexico basin is a significant source of heat. Radiogenic heat should be included in thermal models of this basin (and perhaps other sedimentary basins). We calculate that radiogenic heat may contribute up to 26% of the overall surface heat-flow density for an area in south Texas. Based on measurements of the radioactive decay rate of ??-particles, potassium concentration, and bulk density, we

  8. [Pooled Analysis of RET/PTC Gene Rearrangement Rate in Sporadic and Radiogenic Thyroid Papillary Carcinoma].

    Ushenkova, L N; Koterov, A N; Biryukov, A P


    The database of publications on molecular epidemiology of RET/PTC rearrangements in sporadic and radiogenic thyroid papillary carcinoma has been formed (197 sources at the end of 2014; coverage of 100%). Based on this database a pooled analysis of data on the rates of RET/PTC1, RET/PTC3 and RET/PTC in total was conducted. Statistical approach involves a simple pooling, as well as calculations on the models of random and fixed effects. Since almost all the strata were characterized by heterogeneity, simple pooling and random effect models were adequate. Calculations using both models led to almost identical results. For rates of RET/PTC1, RET/PTC3 and RET/PTC in total with respect to formed carcinoma striations the following values (pooling, in %) were obtained: sporadic, total--13.2; 8.9; 21.2; sporadic, adults--13.3; 9.9; 21.1; sporadic, children--22.4; 17.5; 44.5; radiogenic, total--20.9; 20.3; 40.4; radiotherapy (exposure in childhood)--31.1; 11.8; 42.5; children affected after the Chernobyl accident--19.9; 23.6; 46.1; radiological incidents (exposure in adulthood)--19.9; 7.7; 18.4. Statistically proven is the reliability of differences of carcinoma indicators for children compared with adults (both sporadic and radiogenic tumors) and for radiogenic cancer compared with sporadic. The greatest increase in rate after irradiation was found for RET/PTC1, previously characterized in vitro as one of radiogenic types of RET/PTC.

  9. Do foraminifera accurately record seawater neodymium isotope composition?

    Scrivner, Adam; Skinner, Luke; Vance, Derek


    Palaeoclimate studies involving the reconstruction of past Atlantic meridional overturning circulation increasingly employ isotopes of neodymium (Nd), measured on a variety of sample media (Frank, 2002). In the open ocean, Nd isotopes are a conservative tracer of water mass mixing and are unaffected by biological and low-temperature fractionation processes (Piepgras and Wasserburg, 1987; Lacan and Jeandel, 2005). For decades, benthic foraminifera have been widely utilised in stable isotope and geochemical studies, but have only recently begun to be exploited as a widely distributed, high-resolution Nd isotope archive (Klevenz et al., 2008), potentially circumventing the difficulties associated with other methods used to recover past deep-water Nd isotopes (Klevenz et al., 2008; Rutberg et al., 2000; Tachikawa et al., 2004). Thus far, a single pilot study (Klevenz et al., 2008) has indicated that core-top sedimentary benthic foraminifera record a Nd isotope composition in agreement with the nearest available bottom seawater data, and has suggested that this archive is potentially useful on both millennial and million-year timescales. Here we present seawater and proximal core-top foraminifer Nd isotope data for samples recovered during the 2008 "RETRO" cruise of the Marion Dufresne. The foraminifer samples comprise a depth-transect spanning 3000m of the water column in the Angola Basin and permit a direct comparison between high-resolution water column and core-top foraminiferal Nd isotope data. We use these data to assess the reliability of both planktonic and benthic foraminifera as recorders of water column neodymium isotope composition. Frank, M., 2002. Radiogenic isotopes: Tracers of past ocean circulation and erosional input, Rev. Geophys., 40 (1), 1001, doi:10.1029/2000RG000094. Klevenz, V., Vance, D., Schmidt, D.N., and Mezger, K., 2008. Neodymium isotopes in benthic foraminifera: Core-top systematics and a down-core record from the Neogene south Atlantic

  10. Halogen and Cl isotopic systematics in Martian phosphates: Implications for the Cl cycle and surface halogen reservoirs on Mars

    Bellucci, J. J.; Whitehouse, M. J.; John, T.; Nemchin, A. A.; Snape, J. F.; Bland, P. A.; Benedix, G. K.


    The Cl isotopic compositions and halogen (Cl, F, Br, and I) abundances in phosphates from eight Martian meteorites, spanning most rock types and ages currently available, have been measured in situ by Secondary Ion Mass Spectrometry (SIMS). Likewise, the distribution of halogens has been documented by x-ray mapping. Halogen concentrations range over several orders of magnitude up to some of the largest concentrations yet measured in Martian samples or on the Martian surface, and the inter-element ratios are highly variable. Similarly, Cl isotope compositions exhibit a larger range than all pristine terrestrial igneous rocks. Phosphates in ancient (>4 Ga) meteorites (orthopyroxenite ALH 84001 and breccia NWA 7533) have positive δ37Cl anomalies (+1.1 to + 2.5 ‰). These samples also exhibit explicit whole rock and grain scale evidence for hydrothermal or aqueous activity. In contrast, the phosphates in the younger basaltic Shergottite meteorites (<600 Ma) have negative δ37Cl anomalies (-0.2 to - 5.6 ‰). Phosphates with the largest negative δ37Cl anomalies display zonation in which the rims of the grains are enriched in all halogens and have significantly more negative δ37Cl anomalies suggestive of interaction with the surface of Mars during the latest stages of basalt crystallization. The phosphates with no textural, major element, or halogen enrichment evidence for mixing with this surface reservoir have an average δ37Cl of - 0.6 ‰, supporting a similar initial Cl isotope composition for Mars, the Earth, and the Moon. Oxidation and reduction of chlorine are the only processes known to strongly fractionate Cl isotopes, both positively and negatively, and perchlorate has been detected in weight percent concentrations on the Martian surface. The age range and obvious mixing history of the phosphates studied here suggest perchlorate formation and halogen cycling via brines, which have been documented on the Martian surface, has been active throughout Martian

  11. Lead isotope studies of the Guerrero composite terrane, west-central Mexico: implications for ore genesis

    Potra, Adriana; Macfarlane, Andrew W.


    New thermal ionization mass spectrometry and multi-collector inductively coupled plasma mass spectrometry Pb isotope analyses of three Cenozoic ores from the La Verde porphyry copper deposit located in the Zihuatanejo-Huetamo subterrane of the Guerrero composite terrane are presented and the metal sources are evaluated. Lead isotope ratios of 3 Cenozoic ores from the El Malacate and La Esmeralda porphyry copper deposits located in the Zihuatanejo-Huetamo subterrane and of 14 ores from the Zimapan and La Negra skarn deposits from the adjoining Sierra Madre terrane are also presented to look for systematic differences in the lead isotope trends and ore metal sources among the proposed exotic tectonostratigraphic terranes of southern Mexico. Comparison among the isotopic signatures of ores from the Sierra Madre terrane and distinct subterranes of the Guerrero terrane supports the idea that there is no direct correlation between the distinct suspect terranes of Mexico and the isotopic signatures of the associated Cenozoic ores. Rather, these Pb isotope patterns are interpreted to reflect increasing crustal contribution to mantle-derived magmas as the arc advanced eastward onto a progressively thicker continental crust. The lead isotope trend observed in Cenozoic ores is not recognized in the ores from Mesozoic volcanogenic massive sulfide and sedimentary exhalative deposits. The Mesozoic ores formed prior to the amalgamation of the Guerrero composite terrane to the continental margin, which took place during the Late Cretaceous, in intraoceanic island arc and intracontinental marginal basin settings, while the Tertiary deposits formed after this event in a continental arc setting. Lead isotope ratios of the Mesozoic and Cenozoic ores appear to reflect these differences in tectonic setting of ore formation. Most Pb isotope values of ores from the La Verde deposit (206Pb/204Pb = 18.674-18.719) are less radiogenic than those of the host igneous rocks, but plot within the

  12. Changes in erosion and ocean circulation recorded in the Hf isotopic compositions of North Atlantic and Indian Ocean ferromanganese crusts

    Piotrowski, Alexander M.; Lee, Der-Chuen; Christensen, John N.; Burton, Kevin W.; Halliday, Alex N.; Hein, James R.; Günther, Detlef


    High-resolution Hf isotopic records are presented for hydrogenetic Fe–Mn crusts from the North Atlantic and Indian Oceans. BM1969 from the western North Atlantic has previously been shown to record systematically decreasing Nd isotopic compositions from about 60 to ∼4 Ma, at which time both show a rapid decrease to unradiogenic Nd composition, thought to be related to the increasing influence of NADW or glaciation in the northern hemisphere. During the Oligocene, North Atlantic Hf became progressively less radiogenic until in the mid-Miocene (∼15 Ma) it reached +1. It then shifted gradually back to an ϵHf value of +3 at 4 Ma, since when it has decreased rapidly to about −1 at the present day. The observed shifts in the Hf isotopic composition were probably caused by variation in intensity of erosion as glaciation progressed in the northern hemisphere. Ferromanganese crusts SS663 and 109D are from about 5500 m depth in the Indian Ocean and are now separated by ∼2300 km across the Mid-Indian Ridge. They display similar trends in Hf isotopic composition from 20 to 5 Ma, with the more northern crust having a composition that is consistently more radiogenic (by ∼2 ϵHf units). Paradoxically, during the last 20 Ma the Hf isotopic compositions of the two crusts have converged despite increased separation and subsidence relative to the ridge. A correlatable negative excursion at ∼5 Ma in the two records may reflect a short-term increase in erosion caused by the activation of the Himalayan main central thrust. Changes to unradiogenic Hf in the central Indian Ocean after 5 Ma may alternatively have been caused by the expanding influence of NADW into the Mid-Indian Basin via circum-Antarctic deep water or a reduction of Pacific flow through the Indonesian gateway. In either case, these results illustrate the utility of the Hf isotope system as a tracer of paleoceanographic changes, capable of responding to subtle changes in erosional regime not readily resolved

  13. Carbon isotope systematics of a mantle 'hotspot': A comparison of Loihi Seamount and MORB glasses

    Exley, R.A.; Mattey, D.P.; Pillinger, C.T.; Clague, D.A.


    The carbon isotope geochemistry of glasses from Loihi Seamount has been compared with that of MORB glasses. Stepped heating shows two carbon components in both sample suites: 1. isotopically light carbon (avg. delta/sup 13/C=-26.3per mille) released <600/sup 0/C, ascribed to surficial contamination, and 2. isotopically heavy carbon released >600/sup 0/C, regarded as indigenous. The high-temperature component in MORB samples varied from 52 to 169 ppm C, average delta/sup 13/C=-6.6per mille, consistent with previous studies (overall MORB average delta/sup 13/C=-6.4 +- 0.9per mille), and new results for Indian Ocean glasses are similar to Atlantic and Pacific Ocean samples. Carbon release profiles produced by stepped heating may be typical of locality, but there are no significant differences in delta/sup 13/C values between MORB samples from different areas. Lower yields (17-110 ppm C) correlated with depth in the Loihi samples suggest that they are partially degassed. This degassing has not affected delta/sup 13/C values significantly (avg. -5.8per mille). Loihi tholeiites have higher delta/sup 13/C (avg. -5.6per mille) than the alkali basalts (avg. -7.1per mille). Carbon abundances correlate well with He concentration data. Comparison of the delta/sup 13/C values with trace element and He, Sr, Nd, and Pb isotope data from the literature suggests that the Loihi samples with highest delta/sup 13/C have high /sup 3/He//sup 4/He and possibly the least depleted /sup 143/Nd//sup 144/Nd and /sup 87/Sr//sup 86/Sr. The carbon isotope data are consistent with previous models for Loihi involving several mantle sources, lithospheric contamination, and mixing. The slightly higher delta/sup 13/C of Loihi tholeiites suggests that the undegassed ''plume'' component manifested by high /sup 3/He//sup 4/He values might have delta/sup 13/C about 1per mille higher than the MORB average.

  14. ReOs isotope systematics of NiCu sulfide ores, Sudbury Igneous Complex, Ontario: evidence for a major crustal component

    Walker, R.J.; Morgan, J.W.; Naldrett, A.J.; Li, C.; Fassett, J.D.


    Sudbury Igneous Complex sublayer ores from the Levack West, Falconbridge and Strathcona mines were analyzed for their Re and Os concentrations and Os isotopic compositions. The ReOs isotope systematics of three ores from the different mines give isochron ages of 1840 ?? 60 Ma, 1770 ?? 60 Ma and 1780 ?? 110 Ma, suggesting that the ReOs system became closed at the time of, or soon after the 1850 ?? 1 Ma crystallization age of the complex. The Os isotopic compositions of different portions of the complex at the time of crystallization varied considerably, with initial 187Os 186Os1850 ranging from 4.64 at Levack West to 7.55 at Strathcona. These heterogeneities require that the Os, and probably also the other platinum-group elements contained in the ores, were derived from at least two sources. In addition, the high initial 187Os 186Os ratios indicate that the Os was derived predominantly from ancient crust. Previous studies have suggested that the complex either crystallized from a mixture of mantle-derived basaltic melt and ancient continental crust, or was derived exclusively from the fusion of ancient continental crust resulting from a meteorite impact. Results of modelling suggest that if a contemporaneous mantle-derived basaltic melt was involved in the origin of the SIC, it likely contributed < 50% of the Os to all three ores. The large percentage of ancient crust involved in the production of the ores is most consistent with an interpretation of substantial crustal fusion resulting from meteorite impact. ?? 1991.

  15. Sm-Nd and Initial Sr-87/Sr-86 Isotopic Systematics of Asuka 881394 and Cumulate Eucrites Yamato 980318/433 Compared

    Nyquist, L. E.; Shih, C-Y; Young, Y. D.; Takeda, H.


    The Asuka 881394 achondrite contains fossil Al-26 and Mn-53 and has a Pb-206/Pb-207 age of 4566.5 +/- 0.2 Ma, the oldest for an achondrite. Recent re-investigation of A881394 yielded revised initial Sm-146/Sm-144 = (9.1 +/- 1.4) x 10(exp -3), a Sm-147-Nd-143 age of 4525 +/- 58 Ma, a Rb-87-Sr-87 age of 4490 +/- 130 Ma, and initial Sr-87/Sr-86 = 0.698991 +/- 19, respectively. The relatively large uncertainties in the Sm-Nd and Rb-Sr ages are due to disturbances of the isotopic systematics of tridymite and other minor phases. A preliminary value for the Sm-147-Nd-143 age of the Yamato 980318 cumulate eucrite of 4560 +/- 150 Ma was refined in later work to 4567 +/- 24 Ma as reported orally at LPSC 35. Similarly, a preliminary value for Sm-146/Sm-144 = (7.7 +/- 1.2) x 10 (exp -3) was refined to (6.0 +/- 0.3) x 10(exp -3). For Yamato 980433, a Sm-147-Nd-143 age of 4542 +/-42 Ma and Sm-146/Sm-144 = (5.7 +/- 0.5) x 10(exp -3) has been reported. Because these two cumulate eucrites are paired, we consider them to represent one igneous rock and present their combined isotopic data here.

  16. Re - Os isotopic constraints on the origin of volcanic rocks, Gorgona Island, Colombia: Os isotopic evidence for ancient heterogeneities in the mantle

    Walker, R.J.; Echeverria, L.M.; Shirey, S.B.; Horan, M.F.


    The Re - Os isotopic systematics of komatiites and spatially associated basalts from Gorgona Island, Colombia, indicate that they were produced at 155??43 Ma. Subsequent episodes of volcanism produced basalts at 88.1??3.8 Ma and picritic and basaltic lavas at ca. 58 Ma. The age for the ultramafic rocks is important because it coincides with the late-Jurassic, early-Cretaceous disassembly of Pangea, when the North- and South-American plates began to pull apart. Deep-seated mantle upwelling possibly precipitated the break-up of these continental plates and caused a tear in the subducting slab west of Gorgona, providing a rare, late-Phanerozoic conduit for the komatiitic melts. Mantle sources for the komatiites were heterogeneous with respect to Os and Pb isotopic compositions, but had homogeneous Nd isotopic compositions (??Nd+9??1). Initial 187Os/186Os normalized to carbonaceous chondrites at 155 Ma (??Os) ranged from 0 to +22, and model-initial ?? values ranged from 8.17 to 8.39. The excess radiogenic Os, compared with an assumed bulk-mantle evolution similar to carbonaceous chondrites, was likely produced in portions of the mantle with long-term elevated Re concentrations. The Os, Pb and Nd isotopic compositions, together with major-element constraints, suggest that the sources of the komatiites were enriched more than 1 Ga ago by low (<20%) and variable amounts of a basalt or komatiite component. This component was added as either subducted oceanic crust or melt derived from greater depths in the mantle. These results suggest that the Re - Os isotope system may be a highly sensitive indicator of the presence of ancient subducted oceanic crust in mantle-source regions. ?? 1991 Springer-Verlag.

  17. Sulfur and oxygen isotopic systematics of the 1982 eruptions of El Chichón Volcano, Chiapas, Mexico

    Rye, R.O.; Luhr, J.F.; Wasserman, M.D.


    Thermometers based on sulfur and oxygen isotopic compositions of anhydrite, pyrrhotite, titanomagnetite, and plagioclase crystals from fresh pumices of the 1982 eruptions of El Chichón Volcano indicate a pre-eruption temperature of 810 ± 40°C, confirming textural evidence that the anhydrite precipitated directly from the melt. The isotopic composition of sulfate leached from fresh ashfall samples shows it to be a mixture of anhydrite microphenocrysts and adsorbed sulfate derived from oxidized sulfur (SO2) in the eruption plume. The leachate data show no evidence for rapid oxidation of significant amounts of H2S in the eruption cloud even though the fugacity ratio of H2S/SO2 in the gas phase of the magma was >400. This may indicate kinetic inhibition of H2S to SO2 conversion in the eruption cloud. Prior to eruption, the magma contained an estimated 2.6 wt. % sulfur (as SO3). The estimated δ 34S of the bulk magma is 5.8‰. Such a high value may reflect assimilation of 34S-enriched evaporites or the prior loss of 34S-depleted H2S to a fluid or gas phase during formation of a small prophyry-type hydrothermal system or ore deposit. In either case, the original magma must have been very sulfur rich. It is likely that the initial high sulfur content of the magma and at least some of its 34S enrichment reflects involvement of subducted volcanogenic massive sulfides deposits during Benioff-zone partial melting. Isotopic data on mineralized, accidental lithic fragments support the possible development of a porphyry-type system at El Chichón.

  18. Sulfur and oxygen isotopic systematics of the 1982 eruptions of El Chichón Volcano, Chiapas, Mexico

    Rye, R. O.; Luhr, J. F.; Wasserman, M. D.


    Thermometers based on sulfur and oxygen isotopic compositions of anhydrite, pyrrhotite, titanomagnetite, and plagioclase crystals from fresh pumices of the 1982 eruptions of El Chichón Volcano indicate a pre-eruption temperature of 810 ± 40°C, confirming textural evidence that the anhydrite precipitated directly from the melt. The isotopic composition of sulfate leached from fresh ashfall samples shows it to be a mixture of anhydrite microphenocrysts and adsorbed sulfate derived from oxidized sulfur (SO 2) in the eruption plume. The leachate data show no evidence for rapid oxidation of significant amounts of H 2S in the eruption cloud even though the fugacity ratio of H 2S/SO 2 in the gas phase of the magma was >400. This may indicate kinetic inhibition of H 2S to SO 2 conversion in the eruption cloud. Prior to eruption, the magma contained an estimated 2.6 wt. % sulfur (as SO 3). The estimated δ 34S of the bulk magma is 5.8‰. Such a high value may reflect assimilation of 34S-enriched evaporites or the prior loss of 34S-depleted H 2S to a fluid or gas phase during formation of a small prophyry-type hydrothermal system or ore deposit. In either case, the original magma must have been very sulfur rich. It is likely that the initial high sulfur content of the magma and at least some of its 34S enrichment reflects involvement of subducted volcanogenic massive sulfides deposits during Benioff-zone partial melting. Isotopic data on mineralized, accidental lithic fragments support the possible development of a porphyry-type system at El Chichón.

  19. Carbon isotope systematics and CO2 sources in The Geysers-Clear Lake region, northern California, USA

    Bergfeld, D.; Goff, F.; Janik, C.J.


    Carbon isotope analyses of calcite veins, organic carbon, CO2 and CH4 from 96 rock and 46 gas samples show that metamorphic calcite veins and disseminated, organically-derived carbon from Franciscan Complex and Great Valley Sequence rocks have provided a primary carbon source for geothermal fluids during past and present hydrothermal activity across The Geysers-Clear Lake region. The stable isotope compositions of calcite veins vary widely on a regional scale, but overall they document the presence of 13C-poor fluids in early subduction-related vein-precipitating events. ??13C values of calcite veins from the SB-15-D corehole within The Geysers steam field indicate that carbon-bearing fluids in the recent geothermal system have caused the original diverse ??13C values of the veins to be reset. Across The Geysers-Clear Lake region the carbon isotope composition of CO2 gas associated with individual geothermal reservoirs shows a general increasing trend in ??13C values from west to east. In contrast, ??13C values of CH4 do not exhibit any spatial trends. The results from this study indicate that regional variations in ??13C-CO2 values result from differences in the underlying lithologies. Regional CO2 contains significant amounts of carbon related to degradation of organic carbon and dissolution of calcite veins and is not related to equilibrium reactions involving CH4. CO2 from degassing of underlying magma chambers is not recognizable in this region. Published by Elsevier Science Ltd on behalf of CNR.

  20. Strontium isotope systematics of mixing groundwater and oil-field brine at Goose Lake in northeastern Montana, USA

    Peterman, Zell E.; Thamke, Joanna N.; Futa, Kiyoto; Preston, Todd


    Groundwater, surface water, and soil in the Goose Lake oil field in northeastern Montana have been affected by Cl−-rich oil-field brines during long-term petroleum production. Ongoing multidisciplinary geochemical and geophysical studies have identified the degree and local extent of interaction between brine and groundwater. Fourteen samples representing groundwater, surface water, and brine were collected for Sr isotope analyses to evaluate the usefulness of 87Sr/86Sr in detecting small amounts of brine. Differences in Sr concentrations and 87Sr/86Sr are optimal at this site for the experiment. Strontium concentrations range from 0.13 to 36.9 mg/L, and corresponding 87Sr/86Sr values range from 0.71097 to 0.70828. The local brine has 168 mg/L Sr and a 87Sr/86Sr value of 0.70802. Mixing relationships are evident in the data set and illustrate the sensitivity of Sr in detecting small amounts of brine in groundwater. The location of data points on a Sr isotope-concentration plot is readily explained by an evaporation-mixing model. The model is supported by the variation in concentrations of most of the other solutes.

  1. Radiogenic and Muon-Induced Backgrounds in the LUX Dark Matter Detector

    Akerib, D S; Bai, X; Bailey, A J; Balajthy, J; Bernard, E; Bernstein, A; Bradley, A; Byram, D; Cahn, S B; Carmona-Benitez, M C; Chan, C; Chapman, J J; Chiller, A A; Chiller, C; Coffey, T; Currie, A; de Viveiros, L; Dobi, A; Dobson, J; Druszkiewicz, E; Edwards, B; Faham, C H; Fiorucci, S; Flores, C; Gaitskell, R J; Gehman, V M; Ghag, C; Gibson, K R; Gilchriese, M G D; Hall, C; Hertel, S A; Horn, M; Huang, D Q; Ihm, M; Jacobsen, R G; Kazkaz, K; Knoche, R; Larsen, N A; Lee, C; Lindote, A; Lopes, M I; Malling, D C; Mannino, R; McKinsey, D N; Mei, D -M; Mock, J; Moongweluwan, M; Morad, J; Murphy, A St J; Nehrkorn, C; Nelson, H; Neves, F; Ott, R A; Pangilinan, M; Parker, P D; Pease, E K; Pech, K; Phelps, P; Reichhart, L; Shutt, T; Silva, C; Solovov, V N; Sorensen, P; O'Sullivan, K; Sumner, T J; Szydagis, M; Taylor, D; Tennyson, B; Tiedt, D R; Tripathi, M; Uvarov, S; Verbus, J R; Walsh, N; Webb, R; White, J T; Witherell, M S; Wolfs, F L H; Woods, M; Zhang, C


    The Large Underground Xenon (LUX) dark matter experiment aims to detect rare low-energy interactions from Weakly Interacting Massive Particles (WIMPs). The radiogenic backgrounds in the LUX detector have been measured and compared with Monte Carlo simulation. Measurements of LUX high-energy data have provided direct constraints on all background sources contributing to the background model. The expected background rate from the background model for the 85.3 day WIMP search run is $(2.6\\pm0.2_{\\textrm{stat}}\\pm0.4_{\\textrm{sys}})\\times10^{-3}$~events~keV$_{ee}^{-1}$~kg$^{-1}$~day$^{-1}$ in a 118~kg fiducial volume. The observed background rate is $(3.6\\pm0.4_{\\textrm{stat}})\\times10^{-3}$~events~keV$_{ee}^{-1}$~kg$^{-1}$~day$^{-1}$, consistent with model projections. The expectation for the radiogenic background in a subsequent one-year run is presented.

  2. Radiogenic neoplasia in thyroid and mammary clonogens. Progress report, January 1, 1993--December 31, 1993

    Clifton, K.H.


    The induction of cancer by ionizing radiation is a matter of great practical importance to the nuclear industry, to national defense, to radiological medicine and to the general public. It is increasingly apparent that carcinogenesis is one of the leading dose-limiting effects of radiation exposure (Co90). Quantitative information at the cellular level is essential to an understanding of the mechanisms of radiogenic neoplastic initiation and the stages of promotion and progression to overt neoplasia. We have developed two experimental models, the rat thyroid and rat mammary clonogen transplant systems, for the quantitative study of radiation carcinogenesis at the cellular level in vivo (C185). The most important steps taken or completed during the current grant year include: (a) demonstration of the high age-dependent radiosensitivity of prepubertal rat mammary clonogens to radiogenic damage which may influence their susceptibility to neoplastic initiation, and (b) demonstration of the feasibility of using a molecular test for clonogenicity in which Simple Sequence Repeats in the DNA serve as identifying signals of the genotypic origin of the cells. We have also (c) set up a large carcinogenesis experiment to test the effect of close intercellular contact in thyroid glands in situ on promotion-progression of radiogenically initiated clonogens, (d) achieved considerable further concentration of thyroid clonogens, and (e) begun to explore whether thyroid cells can be induced to give rise to three dimensional multicellular structures in culture in reconstituted basement membrane. These are discussed in this report.

  3. Systematic study of the isotopic dependence of fusion dynamics for neutron- and proton-rich nuclei using a proximity formalism

    Ghodsi, O N; Lari, F


    The behaviors of barrier characteristics and fusion cross sections are analyzed by changing neutron over wide range of colliding systems. For this purpose, we have extended our previous study (Eur. Phys. J. A \\textbf{48}, 21 (2012), it is devoted to the colliding systems with neutron-rich nuclei) to 125 isotopic systems with condition of $0.5\\leq N/Z \\leq 1.6$ for their compound nuclei. The AW 95, Bass 80, Denisov DP and Prox. 2010 potentials are used to calculate the nuclear part of interacting potential. The obtained results show that the trend of barrier heights $V_B$ and positions $R_B$ as well as nuclear $V_N$ and Coulomb $V_C$ potentials (at $R=R_B$) as a function of ($N/Z-1$) quantity are non-linear (second-order) whereas the fusion cross sections follow a linear-dependence.

  4. Boron isotope systematics of tourmaline formation in the Sullivan Pb-Zn-Ag deposit, British Columbia, Canada

    Jiang, S.-Y.; Palmer, M.R.; Slack, J.F.; Shaw, D.R.


    We report here the results of 54 boron isotope analyses of tourmaline associated with the giant Sullivan Pb-Zn-Ag deposit in southeastern British Columbia, Canada. The ??11B values range from -11.1 to -2.9???, which is almost as great as the range found worldwide in tourmalines from 33 massive sulfide deposits and tourmalinites in dominantly clastic metasedimentary terranes. The major control on the overall ??11B values of the Sullivan tourmalinites is the boron source. Potential controls over the large range of the data also include: (1) differences in formation temperatures of the tourmalinites, (2) different stages of tourmaline formation, (3) variations in the proportions of dissolved boron incorporated into the tourmaline (Rayleigh fractionation), (4) seawater entrainment, and (5) post-depositional metamorphism. The boron isotope data at Sullivan are consistent with boron derivation from leaching of footwall clastic sediments. However, the great abundance of tourmaline in the Sullivan deposit suggests that the local clastic sediments were not the sole source of boron, and we argue that non-marine evaporites, buried deep below the orebody, are the most viable source of this additional boron. It is likely that some of the variation in tourmaline ??11B values reflect mixing of boron from these two sources. Comparison of the potential effects of these controls with geologic and other geochemical evidence suggests that major causes for the wide range of ??11B values measured at Sullivan are seawater entrainment and Rayleigh fractionation, although in places, post-depositional alteration and thermal metamorphism were important in determining ??11B values of some of the recrystallized tourmalinites.

  5. Using geoneutrinos to constrain the radiogenic power in the Earth's mantle

    Šrámek, Ondřej; Roskovec, Bedřich; Wipperfurth, Scott A.; Xi, Yufei; McDonough, William F.


    The Earth's engine is driven by unknown proportions of primordial energy and heat produced in radioactive decay. Unfortunately, competing models of Earth's composition reveal an order of magnitude uncertainty in the amount of radiogenic power driving mantle dynamics. Together with established geoscientific disciplines (seismology, geodynamics, petrology, mineral physics), experimental particle physics now brings additional constraints to our understanding of mantle energetics. Measurements of the Earth's flux of geoneutrinos, electron antineutrinos emitted in β- decays of naturally occurring radionuclides, reveal the amount of uranium and thorium in the Earth and set limits on the amount of radiogenic power in the planet. Comparison of the flux measured at large underground neutrino experiments with geologically informed predictions of geoneutrino emission from the crust provide the critical test needed to define the mantle's radiogenic power. Measuring geoneutrinos at oceanic locations, distant from nuclear reactors and continental crust, would best reveal the mantle flux and by performing a coarse scale geoneutrino tomography could even test the hypothesis of large heterogeneous structures in deep mantle enriched in heat-producing elements. The current geoneutrino detecting experiments, KamLAND in Japan and Borexino in Italy, will by year ˜ 2020 be supplemented with three more experiments: SNO+ in Canada, and JUNO and Jinping in China. We predict the geoneutrino flux at all experimental sites. Within ˜ 8 years from today, the combination of data from all experiments will exclude end-member compositional models of the silicate Earth at the 1σ level, reveal the radiogenic contribution to the global surface heat loss, and provide tight limits on radiogenic power in the Earth's mantle. Additionally, we discuss how the geoneutrino measurements at the three relatively near-lying (≤ 3000 km) detectors KamLAND, JUNO, and Jinping may be harnessed to improve the

  6. Simultaneous spectroscopy of $\\gamma$- rays and conversion electrons: Systematic study of EO transitions and intruder states in close vicinity of mid-shell point in odd-Au isotopes

    Venhart, M; Grant, A F; Petrik, K

    This proposal focuses on detailed systematic studies of the $\\beta$ /EC-decays of $^{179,181,183,185}$Hg leading to excited states in the neutron-deficient Au isotopes in the vicinity of the N=104 midshell. $\\gamma$-ray, X-ray and conversion electron de-excitations of odd-A Au isotopes will be studied simultaneously. These studies will address important structural questions such as the excitation energies of coexisting states, properties of multiple intruder states (i.e. intruder particles coupled to intruder cores) and mixing of coexisting structures. The unique combination of Hg beam purity and yields make ISOLDE a unique facility for these experiments.

  7. Coal fly ash interaction with environmental fluids: Geochemical and strontium isotope results from combined column and batch leaching experiments

    Brubaker, Tonya M; Stewart, Brian W; Capo, Rosemary C; Schroeder, Karl T; Chapman, Elizabeth C; Spivak-Birndorf, Lev J; Vesper, Dorothy J; Cardone, Carol R; Rohar, Paul C


    The major element and Sr isotope systematics and geochemistry of coal fly ash and its interactions with environmental waters were investigated using laboratory flow-through column leaching experiments (sodium carbonate, acetic acid, nitric acid) and sequential batch leaching experiments (water, acetic acid, hydrochloric acid). Column leaching of Class F fly ash samples shows rapid release of most major elements early in the leaching procedure, suggesting an association of these elements with soluble and surface bound phases. Delayed release of certain elements (e.g., Al, Fe, Si) signals gradual dissolution of more resistant silicate or glass phases as leaching continues. Strontium isotope results from both column and batch leaching experiments show a marked increase in {sup 87}Sr/{sup 86}Sr ratio with continued leaching, yielding a total range of values from 0.7107 to 0.7138. For comparison, the isotopic composition of fluid output from a fly ash impoundment in West Virginia falls in a narrow range around 0.7124. The experimental data suggest the presence of a more resistant, highly radiogenic silicate phase that survives the combustion process and is leached after the more soluble minerals are removed. Strontium isotopic homogenization of minerals in coal does not always occur during the combustion process, despite the high temperatures encountered in the boiler. Early-released Sr tends to be isotopically uniform; thus the Sr isotopic composition of fly ash could be distinguishable from other sources and is a useful tool for quantifying the possible contribution of fly ash leaching to the total dissolved load in natural surface and ground waters.

  8. Search for a meteoritic component in impact-melt rocks from the Lonar crater, India - Evidence from osmium isotope systematics

    Schulz, T.; Luguet, A.; Koeberl, C.


    Introduction: The Lonar crater in western India (Maharashtra) is a bowl-shaped simple impact structure of 1830 m diameter and a depth of 120 m below the rim crest. The crater formed 0.656 × 0.081 Ma ago on the 65 Ma old basaltic lava flows of the Deccan Traps (Jourdan et al. 2010) and is one of the few terrestrial impact structures to have formed in basaltic host-rocks. In the absence of actual meteorite fragments, the impact origin of this structure was supported by the identification of a variety of shock metamorphic features (e.g. Fredriksson et al. 1973). However, clear indications of an extraterrestrial component in impactites based on geochemical studies are absent or remained ambiguous so far (e.g. Osae et al. 2005). As the Os isotope tool has the potential to provide firm constraints on the presence or absence of even very small (meteoritic matter to impactite lithologies (e.g. Koeberl et al. 2002), we conduct a detailed Os isotope study of a variety of unshocked host-basalts (target rocks) and impactites (impact-melt rocks) from the Lonar crater. Samples and Method: All samples analyzed in this study were collected in 2000 and 2001 and were geochemically characterized by Osae et al. (2005). Osmium (and additional PGE) analyses were performed on about 2 g whole rock powders, which were spiked with a mixed 190Os,185Re,191Ir,194Pt tracer, and digested via high pressure Asher using inverse aqua regia. Osmium solvent extraction and microdistillation were performed as described by Cohen and Waters (1996). Osmium isotopic compositions were measured using a TRITON N-TIMS at the Department of Lithospheric Research in Vienna. Results and Discussion: Osmium data on seven target and nine impact melt rocks reveal 187Os/188Os ratios ranging from ~0.38 to ~2.23 for the target rocks and from ~0.22 to ~0.59 for the nine analyzed impact melt rocks, whereas Os concentrations range from ~7.1 to ~31.6 ppt and ~7.2 to ~134 ppt, respectively. Although in the typical range for

  9. Radiogenic Heat Production in the Gölcük Caldera and Direkli, Isparta Angle (Southwest Anatolia)

    Ayten Uyanık, Nurten; Öncü, Ziya; Akkurt, İskender


    The radiogenic heat is one of the important parameter due to the radioactivity has existed since beginning of universe as prediction of Big-Bang theory. In this study the radiogenic heat production of the Gölcük caldera and Direkli fields of the Isparta-Turkey, has been investigated. Total of 1390 data were obtained in the study area. The study area is included of the Gölcük volcanism and its around that is located in Isparta province of Turkey's Mediterranean region. The Gölcük volcanism is a young volcanism. Around this volcanism the andesite, trachy andesite, tuff, pumice and such a geological units is available. The data were collected using in-situ measurements with gamm-ray spectrometer. These measurements were covered natural radioactive elements (Uranium U, Thorium Th and Potassium K). Radiogenic heat production values were calculated using the literature relationships and in-situ measurement values of these radioactive elements. Radiogenic heat map of study area were obtained using radiogenic heat production values. In the map the red zone areas shows highest heat values while green zones areas of the map presents lowest heat values. Key words: Radioactive elements, radiogenic heat, map, Gölcük-Direkli(Isparta), Turkey

  10. Provenance and sedimentary environments of the Proterozoic São Roque Group, SE-Brazil: Contributions from petrography, geochemistry and Sm-Nd isotopic systematics of metasedimentary rocks

    Henrique-Pinto, R.; Janasi, V. A.; Tassinari, C. C. G.; Carvalho, B. B.; Cioffi, C. R.; Stríkis, N. M.


    The Proterozoic metasedimentary sequences exposed in the São Roque Domain (Apiaí Terrane, Ribeira Belt, southeast Brazil) consist of metasandstones and meta-felspathic wackes with some volcanic layers of within-plate geochemical signature (Boturuna Formation), a passive margin turbidite sequence of metawackes and metamudstones (Piragibu Formation), and volcano-sedimentary sequences with MORB-like basalts (Serra do Itaberaba Group; Pirapora do Bom Jesus Formation). A combination of zircon provenance studies in metasandstones, whole-rock geochemistry and Sm-Nd isotopic systematics in metamudstones was used to understand the provenance and tectonic significance of these sequences, and their implications to the evolution of the Precambrian crust in the region. Whole-rock geochemistry of metamudstones, dominantly from the Piragibu Formation, points to largely granitic sources (as indicated for instance by LREE-rich moderately fractionated REE patterns and subtle negative Eu anomalies) with some mafic contribution (responding for higher contents of Fe2O3, MgO, V, and Cr) and were subject to moderate weathering (CIA - 51 to 85). Sm-Nd isotope data show three main peaks of Nd TDM ages at ca. 1.9, 2.1 and 2.4 Ga; the younger ages define an upper limit for the deposition of the unit, and reflect greater contributions from sources younger than the >2.1 Ga basement. The coincident age peaks of Nd TDM and U-Pb detrital zircons at 2.1-2.2 Ga and 2.4-2.5 Ga, combined with the possible presence of a small amount of zircons derived from mafic (gabbroid) sources with the same ages, as indicated by a parallel LA-ICPMS U-Pb dating study in metapsammites, are suggestive that these were major periods of crustal growth in the sources involving not only crust recycling but also some juvenile addition. A derivation from similar older Proterozoic sources deposited in a passive margin basin is consistent with the main sedimentary sequences in the São Roque Domain being broadly coeval and

  11. Systematical study of high-spin rotational bands in neutron-deficient Kr isotopes by the extended projected shell model

    Wu, Xin-Yi; Ghorui, S. K.; Wang, Long-Jun; Kaneko, K.; Sun, Yang


    We analyze the high-spin structure of the even-even 72-80Kr isotopes using the Projected Shell Model (PSM). With the help of the Pfaffian formulas, we have vigorously extended the quasi-particle (qp) basis of the PSM code and applied in this mass region for the first time. We consider a sufficiently large multi-qp configuration space in order to describe high-spin rotational behavior. The results show that the calculation can reproduce most of the known rotational bands with positive- or negative-parity. Moreover, some side bands appearing in the near-yrast region are predicted. The main structure for each band is discussed in terms of multi-qp configurations. The variations in moment of inertia with spin are explained in terms of successive band crossings among the 2-qp, 4-qp, 6-qp, and 8-qp states. The B (E 2) transition probabilities in these bands are also calculated. To further understand the high-spin behavior of these neutron-deficient nuclei and to confirm predictions of the present work, good high-spin data, especially for B (E 2) transitions, are called for.

  12. Trace elements and Pb isotopes in soils and sediments impacted by uranium mining

    Cuvier, A., E-mail: [ECOLAB, Université de Toulouse, CNRS, INPT, UPS, Toulouse (France); IRSN/PRP-ENV/SESURE/Laboratoire d' études radioécologiques en milieu continental et marin, BP 1, 13108 Saint Paul Lez Durance Cedex (France); Pourcelot, L. [IRSN/PRP-ENV/SESURE/Laboratoire d' études radioécologiques en milieu continental et marin, BP 1, 13108 Saint Paul Lez Durance Cedex (France); Probst, A. [ECOLAB, Université de Toulouse, CNRS, INPT, UPS, Toulouse (France); Prunier, J. [Observatoire Midi-Pyrénées, laboratoire Géosciences Environnement Toulouse, CNRS/IRD/Université Paul Sabatier, 14 avenue Edouard Belin, 31400 Toulouse (France); Le Roux, G., E-mail: [ECOLAB, Université de Toulouse, CNRS, INPT, UPS, Toulouse (France)


    The purpose of this study is to evaluate the contamination in As, Ba, Co, Cu, Mn, Ni, Sr, V, Zn and REE, in a high uranium activity (up to 21,000 Bq ∙ kg{sup −1}) area, downstream of a former uranium mine. Different geochemical proxies like enrichment factor and fractions from a sequential extraction procedure are used to evaluate the level of contamination, the mobility and the availability of the potential contaminants. Pb isotope ratios are determined in the total samples and in the sequential leachates to identify the sources of the contaminants and to determine the mobility of radiogenic Pb in the context of uranium mining. In spite of the large uranium contamination measured in the soils and the sediments (EF ≫ 40), trace element contamination is low to moderate (2 < EF < 5), except for Ba (5 < EF < 15), due to the precipitation of barium sulfate resulting from mining activities. Most of the trace elements are associated with the most mobile fractions of the sediments/soils, implying an enhanced potential availability. Even if no Pb enrichment is highlighted, the Pb isotopic signature of the contaminated soils is strongly radiogenic. Measurements performed on the sequential leachates reveal inputs of radiogenic Pb in the most mobile fractions of the contaminated soil. Inputs of low-mobile radiogenic Pb from mining activities may also contribute to the Pb signature recorded in the residual phase of the contaminated samples. We demonstrate that Pb isotopes are efficient tools to trace the origin and the mobility of the contaminants in environments affected by uranium mining. - Highlights: • Contamination of soils is evidenced by a multiproxy approach. • Enrichment factors highlight a low contamination except for U, S and Ba. • Pb isotope ratios point out inputs of radiogenic Pb from the mine. • Radiogenic Pb is mainly in the acid-soluble and the reducible fractions.

  13. Reconciliation of the excess 176Hf conundrum in meteorites: Recent disturbances of the Lu-Hf and Sm-Nd isotope systematics

    Bast, Rebecca; Scherer, Erik E.; Sprung, Peter; Mezger, Klaus; Fischer-Gödde, Mario; Taetz, Stephan; Böhnke, Mischa; Schmid-Beurmann, Hinrich; Münker, Carsten; Kleine, Thorsten; Srinivasan, Gopalan


    The long-lived 176Lu-176Hf and 147Sm-143Nd radioisotope systems are commonly used chronometers, but when applied to meteorites, they can reveal disturbances. Specifically, Lu-Hf isochrons commonly yield dates up to ∼300 Myr older than the solar system and varying initial 176Hf/177Hf values. We investigated this problem by attempting to construct mineral and whole rock isochrons for eucrites and angrites. Meteorites from different parent bodies exhibit similar disturbance features suggesting that a common process is responsible. Minerals scatter away from isochron regressions for both meteorite classes, with low-Hf phases such as plagioclase and olivine typically being most displaced above (or left of) reference isochrons. Relatively Hf-rich pyroxene is less disturbed but still to the point of steepening Lu-Hf errorchrons. Using our Lu-Hf and Sm-Nd data, we tested various Hf and Lu redistribution scenarios and found that decoupling of Lu/Hf from 176Hf/177Hf must postdate the accumulation of significant radiogenic 176Hf. Therefore early irradiation or diffusion cannot explain the excess 176Hf. Instead, disturbed meteorite isochrons are more likely caused by terrestrial weathering, contamination, or common laboratory procedures. The partial dissolution of phosphate minerals may predominantly remove rare earth elements including Lu, leaving relatively immobile and radiogenic Hf behind. Robust Lu-Hf (and improved Sm-Nd) meteorite geochronology will require the development of chemical or physical methods for removing unsupported radiogenic Hf and silicate-hosted terrestrial contaminants without disturbing parent-daughter ratios.

  14. Constructing a model of 3D radiogenic heat production in Ireland

    Willmot Noller, N. M.; Daly, J. S.


    Heat production values in the crust and mantle rock inform heat flow density data to provide crucial information about the structure of the Earth's lithosphere. In addition, accurate models of horizontal and vertical distribution of heat production can help to define geothermal exploration targets. Low-enthalpy district scale space heating and Enhanced Geothermal Systems (EGS) using hot, dry rock may provide sustainable energy resources in regions currently perceived as having low geothermal energy potential. Ireland is located within stable lithosphere, unaffected by recent tectonism and volcanism, and has an estimated heat flow range below the measured global continental average. Nevertheless, borehole data indicate that heat production is variable across the island, with anomalously high rates observed, for example, in Cavan, Meath and Antrim. Data coverage is, however, poor. Radioactive isotopic decay generates heat in rock. By using established heat production constants and known concentrations of unstable isotopes of uranium, thorium and potassium, along with rock density values, a heat production rate in μW m -3 is obtained. With the objective of compiling the first comprehensive database of information about the Irish lithosphere, in three dimensions, the authors present here initial results obtained from published and unpublished whole-rock major and trace element analyses. The presence of systematic trends correlating heat production to properties such as age and lithology are also investigated. Offering insight into the vertical component of heat production distribution, Irish xenoliths emplaced in Lower Carboniferous volcanics are regarded as a reliable proxy for the present-day lower crust. Their geochemical composition gives heat production values that are higher than expected for the depths indicated by their thermobarometric data, suggesting that heat production rates do not simply reduce with depth.

  15. He and Ne isotopic ratios along the Terceira Rift: implications for the Azores mantle source

    Madureira, P.; Moreira, M. A.; Nunes, J.; Lourenco, N.; Carvalho, M.; Mata, J.; Pinto de Abreu, M.


    Noble gas data (He and Ne) on olivine phenocrysts obtained from Azores’ lavas sampled along the Terceira Rift will be presented in this work. The Terceira Rift is considered as one of the slowest spreading system in the world (Vogt & Jung, 2004). Lava samples were collected inland at S. Miguel, Terceira, Graciosa, Pico and Faial Islands as well at sea at D. João de Castro Bank and south Hirondelle basin, the latter being sampled by the ROV cruises in 2008 and 2009. Noble gas data were analyzed in the Noblesse mass spectrometer housed at the IPGP. The most primitive He isotopic ratios were obtained from Pico, Terceira and Hirondelle olivines. Most Ne isotopic ratios are similar to the present-day atmosphere, but distinct 20Ne/22Ne ratios were found for the majority of submarine samples and also Pico and Faial Islands, defining mixing lines with the atmospheric end-member with slopes greater than that defined from MORB lavas. The He-Ne systematics shows that most of the new noble gas data fit in a mixing model between a dominant MORB-type mantle source and a relatively primitive mantle source related with the regional Azores component. However, data from the D. João de Castro Bank argue for the presence of a radiogenic He end-member distinct from MORB. References: Vogt, P. & Jung W. (2004). Earth Planet. Sci. Lett., 218: 77 90.

  16. The Late Devonian Frasnian-Famennian (F/F) biotic crisis: Insights from δ13C carb, δ13C org and 87Sr / 86Sr isotopic systematics

    Chen, Daizhao; Qing, Hairuo; Li, Renwei


    A severe biotic crisis occurred during the Late Devonian Frasnian-Famennian (F/F) transition (± 367 Myr). Here we present δ13C carb, δ13C org and 87Sr / 86Sr isotopic systematics, from identical samples of two sections across F/F boundary in South China, which directly demonstrate large and frequent climatic fluctuations (˜200 kyr) from warming to cooling during the F/F transition. These climate fluctuations are interpreted to have been induced initially by increased volcanic outgassing, and subsequent enhanced chemical weathering linked to the rapid expansion of vascular plants on land, which would have increased riverine delivery to oceans and primary bioproductivity, and subsequent burial of organic matter, thereby resulting in climate cooling. Such large and frequent climatic fluctuations, together with volcanic-induced increases in nutrient (e.g., biolimiting Fe), toxin (sulfide) and anoxic water supply, and subsequent enhanced riverine fluxes and microbial bloom, were likely responsible for the stepwise faunal demise of F/F biotic crisis.

  17. Saltpan impact crater, South Africa: Geochemistry of target rocks, breccias, and impact glasses, and osmium isotope systematics

    Koeberl, Christian; Reimold, Wolf Uwe; Shirey, Steven B.


    The Pretoria Saltpan crater is a well-preserved 220,000 year-old, 1.13 km-diameter, simple impact crater. The crater was formed in Nebo granites of the Bushveld Complex. Some minor intrusions thought to be younger than the Nebo granite are present at the crater and have earlier been believed to support a volcanic origin of the structure, but recent geological studies showed them to be part of the regional geology and of Proterozoic age. We studied the petrology and geochemistry of fourteen target granite samples, three suevitic breccias, nine intrusive rocks, as well as melt agglutinates, handpicked impact glass fragments and sulfide spherules from the Saltpan impact crater. Unconsolidated suevitic breccias recovered from different depths in the crater were found to contain abundant evidence of shock metamorphism. The target rock granites show only limited compositional variability. The major and trace element composition of the bulk breccia is very similar to that of average basement granite. Impact glass fragments recovered from the unconsolidated suevitic breccia have a CIPW normative composition similar to that of the basement granites. No evidence for admixture from any of the minor intrusions was found. The similarity of trace element abundances and ratios, and REE patterns between impact glasses and granites favors derivation of the glasses from the granites. The impact glass fragments show considerable enrichments of Mg, Cr, Fe, Co, Ni, and Ir, compared to the basement granites. The abundances of these elements in the glasses (after correction for indigenous concentrations) can be explained by admixture of about ≤ 10% of a chondritic component. High Ir concentrations (≈ 100 ppb) have been found in sulfide spherule samples, which may complement the (lower) Ir abundances in the glasses and could indicate some fractionation during impact. Re-Os isotopic studies were applied to further investigate the presence of a meteoritic component in the suevitic

  18. Constraining the amount of radiogenic elements in the interior of Mars from the HP3 heat flow measurement

    Grott, Matthias; Plesa, Ana-Catalina; Tosi, Nicola; Breuer, Doris


    The InSight mission (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) to be launched in 2016 will carry a seismometer (SEIS) and heat flow probe (HP3) to the martian surface, and address questions related to the size, physical state, and composition of the core and mantle, the thickness of the crust, and the thermal state of the interior. The heat flow measured at the surface depends on the amount of heat producing elements (HPE) present in the interior and offers a measurable quantity that can help to constrain the planetary heat budget. If the Urey ratio - the ratio between internal heat production and surface heat loss - is known, the heat production rate in the interior can be determined. We run thermal evolution models of increasing complexity and compared the obtained present-day Urey ratio for a set of different models/parameters. To this end, we used the 2D-3D mantle convection code Gaia [1], as well as 1D parameterized models [2]. We varied the initial amount of HPE [3, 4,5,6], used various viscosity formulations (temperature-, temperature- and depth-dependent viscosity, viscosity jump in the mid mantle), varied the size of the core, and considered models with and without phase transitions in the mantle. Additionally, we tested the effects of different partitioning of HPE between mantle and a fixed crust, different initial conditions (temperatures and boundary layer thicknesses) and reference viscosities. Our simulations show that, for a one-plate planet like Mars, the Urey ratio is mainly sensitive to the efficiency of mantle cooling, i.e. the mantle viscosity, and to the mean half-life of long-lived radiogenic isotopes. Given that models of the thermo-chemical evolution of Mars generally indicate reference viscosities below 1021 Pa s [3, 7], the martian Urey ratio is likely only a function of the Thorium concentration in the planetary interior. Surface radiogenic abundances determined from gamma-ray spectroscopy [8] are best

  19. Oxygen isotope systematics in the aragonite-CO2-H2O-NaCl system up to 0.7 mol/kg ionic strength at 25 °C

    Kim, Sang-Tae; Gebbinck, Christa Klein; Mucci, Alfonso; Coplen, Tyler B.


    To investigate the oxygen isotope systematics in the aragonite-CO2-H2O-NaCl system, witherite (BaCO3) was precipitated quasi-instantaneously and quantitatively from Na-Cl-Ba-CO2 solutions of seawater-like ionic strength (I = 0.7 mol/kg) at two pH values (~7.9 and ~10.6) at 25 °C. The oxygen isotope composition of the witherite and the dissolved inorganic carbon speciation in the starting solution were used to estimate the oxygen isotope fractionations between HCO3¯ and H2O as well as between CO3 2 and H2O. Given the analytical error on the oxygen isotope composition of the witherite and uncertainties of the parent solution pH and speciation, oxygen isotope fractionation between NaHCO3° and HCO3¯, as well as between NaCO3¯ and CO3 2, is negligible under the experimental conditions investigated. The influence of dissolved NaCl concentration on the oxygen isotope fractionation in the aragonite-CO2-H2O-NaCl system also was investigated at 25 °C. Aragonite was precipitated from Na-Cl-Ca-Mg-(B)-CO2 solutions of seawater-like ionic strength using passive CO2 degassing or constant addition methods. Based upon our new experimental observations and published experimental data from lower ionic strength solutions by Kim et al. (2007b), the equilibrium aragonite-water oxygen isotope fractionation factor is independent of the ionic strength of the parent solution up to 0.7 mol/kg. Hence, our study also suggests that the aragonite precipitation mechanism is not affected by the presence of sodium and chloride ions in the parent solution over the range of concentrations investigated.

  20. The estuarine chemistry and isotope systematics of 234,238U in the Amazon and Fly Rivers

    Swarzenski, P.; Campbell, P.; Porcelli, D.; McKee, B.


    Natural concentrations of 238U and ??234U values were determined in estuarine surface waters and pore waters of the Amazon and Fly (Papua New Guinea) Rivers to investigate U transport phenomena across river-dominated land-sea margins. Discharge from large, tropical rivers is a major source of dissolved and solid materials transported to the oceans, and are important in defining not only oceanic mass budgets, but also terrestrial weathering rates. On the Amazon shelf, salinity-property plots of dissolved organic carbon, pH and total suspended matter revealed two vastly contrasting water masses that were energetically mixed. In this mixing zone, the distribution of uranium was highly non-conservative and exhibited extensive removal from the water column. Uranium removal was most pronounced within a salinity range of 0-16.6, and likely the result of scavenging and flocculation reactions with inorganic (i.e., Fe/Mn oxides) and organic colloids/particles. Removal of uranium may also be closely coupled to exchange and resuspension processes at the sediment/water interface. An inner-shelf pore water profile indicated the following diagenetic processes: extensive (???1 m) zones of Fe(III) - and, to a lesser degree, Mn(IV) - reduction in the absence of significant S(II) concentrations appeared to facilitate the formation of various authigenic minerals (e.g., siderite, rhodocrosite and uraninite). The pore water dissolved 238U profile co-varied closely with Mn(II). Isotopic variations as evidenced in ??234U pore waters values from this site revealed information on the origin and history of particulate uranium. Only after a depth of about 1 m did the ??234U value approach unity (secular equilibrium), denoting a residual lattice bound uranium complex that is likely an upper-drainage basin weathering product. This suggests that the enriched ??234U values represent a riverine surface complexation product that is actively involved in Mn-Fe diagenetic cycles and surface

  1. Iron and copper isotope fractionation during filtration and ultrafiltration of boreal organic-rich waters

    Ilina, Svetlana M.; Viers, Jerome; Pokrovsky, Oleg S.; Poitrasson, Franck; Lapitsky, Sergey A.; Alekhin, Yuriy V.


    Typical feature of all boreal surface waters is high concentration of dissolved (complexes. Organic and organo-mineral colloids are the most likely carriers of trace metals such as Cu in rivers of the boreal zone. This work addresses colloidal speciation of Cu and Fe using conventional size separation technique, on-site frontal ultrafiltration. Specifically, we aimed to test the possibility of the presence of different pools of metal having specific isotopic signatures in different colloidal fractions using stable isotope measurements. We have chosen Cu for its high affinity to colloidal DOM and Fe for its tendency to form stable organo-mineral colloids of various size. Samples of natural waters were collected from small rivers, lakes, bogs, groundwater and soil environments in the Northern Karelia (NW Russia) during summer baseflow period. Large volumes (20-40 L) of water were filtered in the field through progressively decreasing pore size filters: 20, 10, 5, 0.8, 0.45, 0.22, 0.1 µm and 100, 10 and 1 kDa (1 kDa ~ 1 nm) using nylon and regenerated cellulose membranes and frontal ultrafiltration (Millipore, Amicon) devises. The homogeneity of the sample was verified by tracing radiogenic Sr isotopes in each fraction. In all filtrates and ultrafiltrates (permeates), and in selected retentates, stable isotopic composition of Cu and Fe was measured using double focusing high resolution MC-ICP MS (Neptune). We observe rather constant Cu isotopic ratio in all filtrate series and a systematic enrichment of heavy isotope of Fe with decreasing poresize. These preliminary results can be explained by strong complexation of Cu with small-size organic ligands of fulvic nature and its partial association with organo-mineral colloids. Both Fe(III) - OM complxeation and Fe(III) oxyhydroxides precipitation can be invoked to explain Fe isotope fractionation. This work allows, for the first, time, multi-isotopic approach to trace the origin of colloids in surficial waters and it

  2. Hafnium and iron isotopes in early Archean komatiites record a plume-driven convection cycle in the Hadean Earth

    Nebel, Oliver; Campbell, Ian H.; Sossi, Paolo A.; Van Kranendonk, Martin J.


    Archean (>2.5 billion years) komatiites are considered expressions of mantle plumes that originate from and thereby sample the lowermost mantle overlying the Earth's core. Some komatiites have reported Hf isotope signatures that require a mantle source with a time-integrated Lu/Hf that is appreciably higher than average modern depleted mantle. The systematic study of the time and locus of parent-daughter fractionation of the mantle sources of these komatiites potentially constrains differentiation processes in the early Earth, and subsequent distribution and storage of early mantle reservoirs. We present radiogenic Hf and stable Fe isotopes for a series of komatiites from the Pilbara craton in Western Australia (aged 3.5 to 2.9 Ga). After careful evaluation of the effects of alteration, we find that pristine samples are characterised by a light Fe isotope mantle source and initial 176Hf/177Hf well above the age-corrected depleted mantle. Taken together these observations require a component of an old, melt-depleted reservoir in their mantle source. The Hf isotope signature of this component appears to be complementary to the first terrestrial crust, as preserved in Hadean (i.e., >4 Ga) detrital zircon cores, suggesting a causal relationship and a Hadean age for this depletion event. We propose that this Early Refractory Reservoir (ERR) is the residue formed by deep melting in hot Hadean mantle plumes, which then accumulated at the base of the first crust. Parts of this primordial lithosphere were destabilised and sank to the core-mantle boundary in cold drips and subsequently returned in hot mantle plumes, whose thermal capacity allows melting of such refractory mantle with its archetype isotope signature. The cycling of this material via cold drips and hot plumes suggests a plume-dominated convection prior to ∼3.9 Ga, which is then replaced by Archean-style plate tectonics.

  3. Use of radiogenic heat for demarcation of hydrothermal alteration zones in the Pernambuco-Brazil

    Cunha, Leandro O.; Dutra, Alanna C.; Costa, Alexandre B.


    In this paper, we identify hydrothermal alteration zones that are located at the eastern extreme of Borborema Province, Pernambuco State, using radiogenic heat, in combination with magnetic and radioelement data collected both from the air and on the ground. The use of these methods enabled the mapping of geological lineaments based on total magnetic intensity maps, radioelement concentration maps, ternary maps and the F factor, as well as physical properties provided by ground data (thermal conductivity, density, and magnetic susceptibility). The data integration was based on low values of radiogenic heat and high K concentrations, as well as high F factors, amplitudes of the analytic signal, and K/eTh and eU/eTh values. These characteristics occur within the Pernambuco lineament and within other features to the southeast, a short distance south of the lineaments, which are made up of units including a migmatitic gneiss complex, as well as the Modern, Itaporanga and Sierra Passira Intrusive Suites. In these areas, elongated sources that are consistent with lineaments were identified. These sources were assigned depths of up to 3 km and are 5-10 km long, with the most significant extending SE-NW. These areas are favorable for the mineralization of iron, titanium and nickel. As the results are satisfactory, such areas can be studied in detail in the future.


    Riccardo Petrini


    Full Text Available O, H, B and Sr isotopes were identified from surface-waters, ground-waters and waters percolating in soils at the Pialassa Baiona lagoon and nearby inland areas. The preliminary data demonstrate the occurrence of both conservative mixtures between seawater and freshwaters and cation exchange at the salt/fresh water interface during the intrusion. The O and H isotopes indicate that the freshwater component in the binary mixing had the isotopic features of the rainwater from Apennine catchments. Coupled O-H-B isotopes also show that the major contribution of the moving seawater was confined to the deeper aquifers and some of the soil waters. The Sr isotopes highlight the role of cation exchanges when seawater flushes freshwater aquifers, and allow the recognition of the different components of the solute. Deviations from these processes as revealed by B isotopes are interpreted as the evidence of possible anthropogenic inputs.

  5. Resilience of cold-water scleractinian corals to ocean acidification: Boron isotopic systematics of pH and saturation state up-regulation

    McCulloch, Malcolm; Trotter, Julie; Montagna, Paolo; Falter, Jim; Dunbar, Robert; Freiwald, André; Försterra, Günter; López Correa, Matthias; Maier, Cornelia; Rüggeberg, Andres; Taviani, Marco


    The boron isotope systematics has been determined for azooxanthellate scleractinian corals from a wide range of both deep-sea and shallow-water environments. The aragonitic coral species, Caryophyllia smithii, Desmophyllum dianthus, Enallopsammia rostrata, Lophelia pertusa, and Madrepora oculata, are all found to have relatively high δ11B compositions ranging from 23.2‰ to 28.7‰. These values lie substantially above the pH-dependent inorganic seawater borate equilibrium curve, indicative of strong up-regulation of pH of the internal calcifying fluid (pHcf), being elevated by ˜0.6-0.8 units (ΔpH) relative to ambient seawater. In contrast, the deep-sea calcitic coral Corallium sp. has a significantly lower δ11B composition of 15.5‰, with a corresponding lower ΔpH value of ˜0.3 units, reflecting the importance of mineralogical control on biological pH up-regulation. The solitary coral D. dianthus was sampled over a wide range of seawater pHT and shows an approximate linear correlation with ΔpHDesmo = 6.43 - 0.71pHT (r2 = 0.79). An improved correlation is however found with the closely related parameter of seawater aragonite saturation state, where ΔpHDesmo = 1.09 - 0.14Ωarag (r2 = 0.95), indicating the important control that carbonate saturation state has on calcification. The ability to up-regulate internal pHcf, and consequently Ωcf, of the calcifying fluid is therefore a process present in both azooxanthellate and zooxanthellate aragonitic corals, and is attributed to the action of Ca2+-ATPase in modulating the proton gradient between seawater and the site of calcification. These findings also show that the boron isotopic compositions (δ11Bcarb) of aragonitic corals are highly systematic and consistent with direct uptake of the borate species within the biologically controlled extracellular calcifying medium. We also show that the relatively strong up-regulation of pH and consequent elevation of the internal carbonate saturation state (Ωcf ˜8

  6. Predicting the Isotopic Composition of Subduction-Filtered Subducted Oceanic Crust and Sediment

    White, W. M.


    The chemical and isotopic character of mantle plumes, which produce oceanic island volcanoes, are widely thought to reflect the presence of recycled oceanic crust and sediment. Isotopic systematics suggest the “cycle time” for this process is 1 Ga or longer, but it should be possible to use a simple mass balance approach to discern how the presently operating subduction zone filter affects the ratios of radioactive parent to radiogenic daughter isotopes. Simple uniformitarian assumptions can then be used to predict the present isotopic composition of anciently subducted lithosphere. Our underlying assumption in deciphering the subduction zone filter is that the flux of an element into the deep mantle is simply equal to the flux of element into the subduction zone less the flux of that element into subduction zone magmas. The former is readily calculated from published data. The latter can be calculated by estimating parental magma compositions, arc accretion rates, and the assumption that arc magma compositions differ from MORB only because of material derived from subducting crust and sediment. Using this approach for 8 intra-oceanic subduction zones, we find 73% of Th and Pb, 79% of U, 80% of Rb and Sr, 93% of Nd and 98% of Sm survive the subduction zone filter. The subduction zone filter systematically increases Sm/Nd ratios in all subduction zones, but the effect is small, with a weighted mean increase of 1.5%. The effect of subduction is to decrease the Sm/Nd of the mantle, but only slightly. The effect of subduction is to increase the Rb/Sr of the mantle, but the subduction zone filter does not have a systematic effect on Rb/Sr ratios: it significantly increases in Rb/Sr in 3 subduction zones and significantly decreases it in one; the weighted mean shows no significant change. The effect of the subduction zone filter on U/Pb is also not systematic. U/Pb ratios in the mantle fluxes are bimodal, with values equal to or lower than the bulk Earth value in 4

  7. Constraining the role of iron in environmental nitrogen transformations. Dual stable isotope systematics of abiotic NO2- reduction by Fe(II) and its production of N2O

    Johnston, David [Harvard Univ., Cambridge, MA (United States); Wankel, Scott David [Woods Hole Oceanographic Inst., MA (United States); Buchwald, Carolyn [Woods Hole Oceanographic Inst., MA (United States); Hansel, Colleen [Woods Hole Oceanographic Inst., MA (United States)


    Redox reactions involving nitrogen and iron have been shown to have important implications for mobilization of priority contaminants. Thus, an understanding of the linkages between their biogeochemical cycling is critical for predicting subsurface mobilization of radionuclides such as uranium. Despite mounting evidence for biogeochemical interactions between iron and nitrogen, our understanding of their environmental importance remains limited. Here we present an investigation of abiotic nitrite (NO2-) reduction by Fe(II) or ‘chemodenitrification,’ and its relevance to the production of nitrous oxide (N2O), specifically focusing on dual (N and O) isotope systematics under a variety of environmentally relevant conditions. We observe a range of kinetic isotope effects that are regulated by reaction rates, with faster rates at higher pH (~8), higher concentrations of Fe(II) and in the presence of mineral surfaces. A clear non-linear relationship between rate constant and kinetic isotope effects of NO2- reduction was evident (with larger isotope effects at slower rates) and is interpreted as reflecting the dynamics of Fe(II)-N reaction intermediates. N and O isotopic composition of product N2O also suggests a complex network of parallel and/or competing pathways. Our findings suggest that NO2- reduction by Fe(II) may represent an important abiotic source of environmental N2O, especially in iron-rich environments experiencing dynamic redox variations. This study provides a multi-compound, multi-isotope framework for evaluating the environmental occurrence of abiotic NO2- reduction and N2O formation, helping future studies constrain the relative roles of abiotic and biological N2O production pathways.

  8. Melt evolution beneath a rifted craton edge: 40Ar/39Ar geochronology and Sr-Nd-Hf-Pb isotope systematics of primitive alkaline basalts and lamprophyres from the SW Baltic Shield

    Tappe, Sebastian; Smart, Katie A.; Stracke, Andreas; Romer, Rolf L.; Prelević, Dejan; van den Bogaard, Paul


    A new high-precision 40Ar/39Ar anorthoclase feldspar age of 176.7 ± 0.5 Ma (2-sigma) reveals that small-volume alkaline basaltic magmatism occurred at the rifted SW margin of the Baltic Shield in Scania (southern Sweden), at a time of global plate reorganization associated with the inception of Pangea supercontinent break-up. Our combined elemental and Sr-Nd-Hf-Pb isotope dataset for representative basanite and nephelinite samples (>8 wt.% MgO) from 16 subvolcanic necks of the 30 by 40 km large Jurassic volcanic field suggests magma derivation from a moderately depleted mantle source (87Sr/86Sri = 0.7034-0.7048; εNdi = +4.4 to +5.2; εHfi = +4.7 to +8.1; 206Pb/204Pbi = 18.8-19.5). The mafic alkaline melts segregated from mixed peridotite-pyroxenite mantle with a potential temperature of ∼1400 °C at 2.7-4.2 GPa (∼90-120 km depths), which places ultimate melt generation within the convecting upper mantle, provided that the lithosphere-asthenosphere boundary beneath the southern Baltic Shield margin was at ⩽100 km depth during Mesozoic-Cenozoic rifting. Isotopic shifts and incompatible element enrichment relative to Depleted Mantle reflect involvement of at least 20% recycled oceanic lithosphere component (i.e., pyroxenite) with some minor continent-derived sediment during partial melting of well-stirred convecting upper mantle peridotite. Although pargasitic amphibole-rich metasomatized lithospheric mantle is excluded as the main source of the Jurassic magmas from Scania, hydrous ultramafic veins (i.e., hornblendite) may have caused subtle modifications to the compositions of passing sublithospheric melts. For example, modeling suggests that the more radiogenic Hf (εHfi = +6.3 to +8.1) and Pb (206Pb/204Pbi = 18.9-19.5) isotopic compositions of the more sodic and H2O-rich nephelinites, compared with relatively homogenous basanites (εHfi = +4.7 to +6.1; 206Pb/204Pbi = 18.8-18.9), originate from minor interactions between rising asthenospheric melts and

  9. Crustal radiogenic heat production and the selective survival of ancient continental crust

    Morgan, P.


    It is pointed out that the oldest terrestrial rocks have so far revealed no evidence of the impact phase of earth evolution. This observation suggests that processes other than impact were dominant at the time of stabilization of these units. However, a use of the oldest terrestrial rocks as a sample of the early terrestrial crust makes it necessary to consider the possibility that these rocks may represent a biased sample. In the present study, the global continental heat flow data set is used to provide further evidence that potassium, uranium, and thorium abundances are, on the average, low in surviving Archean crust relative to younger continental crust. An investigation is conducted of the implications of relatively low crustal radiogenic heat production to the stabilization of early continental crust, and possible Archean crustal stabilization models are discussed.

  10. Radiogenic neoplasia in thyroid and mammary clonogens. Progress report, January 1, 1990--December 31, 1992

    Clifton, K.H.


    We have developed rat thyroid and mammary clonogen transplantation systems for the study of radiogenic cancer induction at the target cell level in vivo. The epithelial cell populations of both glands contain small subpopulations of cells which are capable of giving rise to monoclonal glandular structures when transplanted and stimulated with appropriate hormones. Previous results indicated that these clonogens are the precursor cells of radiogenic cancer, and that initiation, is common event at the clonegenic cell level. Detailed information on the physiologic control of clonogen proliferation, differentiation, and total numbers is thus essential to an understanding of the carcinogenic process. We report here studies on investigations on the relationships between grafted thyroid cell number and the rapidity and degree of reestablishment of the thyroid-hypothalamus-pituitary feedback axis in thyroidectomized rats maintained on a normal diet or an iodine deficient diet; studies of the persistence of, and the differentiation potential and functional characteristics of, the TSH-(thyrotropin-) responsive sub- population of clonogens during goitrogenesis, the plateau-phase of goiter growth, and goiter involution; studies of changes in the size of the clonogen sub-population during goitrogenesis, goiter involution and the response to goitrogen rechallenge; and a large carcinogenesis experiment on the nature of the grafted thyroid cell number-dependent suppression of promotion/progression to neoplasia in grafts of radiation-initiated thyroid cells. Data from these studies will be used in the design of future carcinogenesis experiments on neoplastic initiation by high and low LET radiations and on cell interactions during the neoplastic process.

  11. Lead isotopic studies of lunar soils - Their bearing on the time scale of agglutinate formation

    Church, S. E.; Tilton, G. R.; Chen, J. H.


    Fines (smaller than 75 microns) and bulk soil were studied to analyze loss of volatile lead; losses of the order of 10% to 30% radiogenic lead during the production of agglutinates are assessed. Lead isotope data from fine-agglutinate pairs are analyzed for information on the time scale of micrometeorite bombardment, from the chords generated by the data in concordia diagrams. Resulting mean lead loss ages were compared to spallogenic gas exposure ages for all samples. Labile parentless radiogenic Pb residing preferentially on or in the fines is viewed as possibly responsible for aberrant lead loss ages. Bulk soils plot above the concordia curve (in a field of excess radiogenic Pb) for all samples with anomalous ages.

  12. Sulfur Isotope Systematics and the Link Between Fluctuating Sulfate Levels and P Recycling in a Low Sulfate, Permanently Anoxic Lake (Lake McCarrons, MN): Implications for the Precambrian Rise of Oxygen

    Gomes, M. L.; Hurtgen, M. T.


    Seawater sulfate concentrations have been used to track the rise of oxygen in the Precambrian ocean-atmosphere system because the primary mode of sulfate delivery to the ocean is the oxidative weathering of sulfides on land. Ancient seawater sulfate concentrations have been inferred from the extent of sulfur (S) isotope fractionation incurred during bacterial sulfate reduction (BSR) where organisms preferentially utilize 32S (over 34S) in the process of reducing of sulfate to sulfide. Within this context, increased variability in δ34Spyrite values in Proterozoic (~2.3 Ga) sediments—along with a corresponding increase in the isotopic difference between sulfate and pyrite (Δ34S)—has been attributed to an increase in seawater sulfate concentrations (from 1 mM) and inferentially Earth-surface oxygen levels. However, most S isotope studies have been calibrated using modern marine sediments that contain sulfate-reducing bacteria that are adapted to the high concentration of sulfate in the modern ocean (~28mM). In order to better understand S isotope systematics within a low sulfate system and to improve our interpretive construct for S isotope results generated from ancient strata, we explore the magnitude of S isotope fractionations associated with microbial activity in the water column and sediments of a low sulfate (isotope difference between surface water sulfate and bottom water sulfide is ~5‰ (Δ34S) while in situ S isotope fractionations associated with BSR at the sediment-water interface approach 35‰; (3) sulfate reduction rates in the upper 3 cm of organic carbon rich sediment are ~0.1 µM cm-3 d-1, an order of magnitude lower than those recorded under higher (modern marine) sulfate concentrations; and (4) sulfate concentrations influence the efficiency of P recycling (as determined via bag incubation experiments). Here, we suggest that an increase in sulfate levels at ~2.3 Ga, as indicated by larger Δ34S values recorded in strata of this age

  13. 76 FR 31329 - EPA Radiogenic Cancer Risk Models and Projections for the U.S. Population (Blue Book)


    ... AGENCY EPA Radiogenic Cancer Risk Models and Projections for the U.S. Population (Blue Book) AGENCY.... Population (EPA 402-R-11-001, April 2011), also known as the Blue Book, which provides radiation risk... Projections for the U.S. Population, also known as the Blue Book, is a revision to EPA's methodology for...

  14. Estimate of influence of U-Th-K radiogenic heat on cooling process of granitic melt and its geological implications


    The U-Th-40K concentrations of granite are on 1―2 orders of magnitude greater than those of basal- tic-ultrabasic rocks. Radiogenic heat of a granitic melt has significant influence on the cool- ing-crystallization period of the melt. In this paper we derived a formula to calculate prolongation period (tA) of cooling-crystallization of a granitic melt caused by radiogenic heat. Calculation using this for- mula and radioactive element concentrations (U=5.31×10-6; Th=23.1×10-6; K=4.55%) for the biotite adamellite of the Jinjiling batholith shows that the tA of the adamellite is 1.4 times of the cooling period of the granitic melt without considering radiogenic heat from the initial temperature (Tm=960℃) to crystallization temperature (Tc=600℃) of the melt. It has been demonstrated that the radiogenic heat produced in a granitic melt is a key factor influencing the cooling-crystallization process of the granitic melt, and is likely one of the reasons for inconsistence between emplacement ages and crystallization ages of many Meso-Cenozoic granitoids.

  15. Nd and Pb isotope variability in the Indus River System: implications for sediment provenance and crustal heterogeneity in the Western Himalaya

    Clift, Peter D.; Lee, Jae Il; Hildebrand, Peter; Shimizu, Nobumichi; Layne, Graham D.; Blusztajn, Jerzy; Blum, Joel D.; Garzanti, Eduardo; Khan, Athar Ali


    The Indus River system is the only major drainage system in the western Himalaya, and erodes not only the High Himalaya, but also topographically high regions within and north of the Indus Suture Zone, most notably the Karakoram. Ion microprobe analysis of Pb isotopes in detrital K-feldspar grains taken from the tributaries of the Indus, together with bulk Nd isotope analysis of those same sediments, is here used to identify distinct sediment source regions. These span the very radiogenic Nanga Parbat and associated Lesser Himalaya, the relatively radiogenic-intermediate High Himalaya, the unradiogenic Ladakh and Kohistan Batholiths and intermediate values in the Hindu Kush, Karakoram and Lhasa Block. The range of compositions reflects differing degrees of recycling of older continental crust during petrogenesis. K-feldspars from the Ladakh and Kohistan Batholiths are less radiogenic than the laterally equivalent Gangdese granite of Tibet, interpreted to reflect the preferential recycling of accreted oceanic arc units within the western Transhimalaya prior to India-Asia collision. Similarly the Zanskar High Himalaya are less radiogenic than their equivalents in Nepal. Isotope values from Pleistocene Indus Fan sediment are compatible with a dominant source in the Karakoram, with additional important contributions from the arc batholiths and High Himalaya, reflecting both the area and modern rates of tectonic uplift within the drainage basin. In contrast, radiogenic grains are common in the lower reaches of the modern Indus River, possibly as a result of the damming of the main river channel where it reaches the foreland.

  16. Carbon and Noble Gas Isotopes in the Tengchong Volcanic Geothermal Area, Yunnan, Southwestern China

    XU Sheng; Shun'ich NAKAI; Hiroshi WAKITA; WANG Xianbin


    Carbon and noble gas isotope analyses are reported for bubbling gas samples from the Tengchong volcanic geothermal area near the Indo-Eurasian suture zone. All samples contain a resolvable component of mantle-derived 3He.Occurrence of mantle-derived 3He coincides with surface volcanism. However, 3He occurs over a larger geographic area than do surface volcanics. δ13C values for CO2 and CH4 vary from -33.4 ‰ to 1.6 ‰ and from -52.8 ‰ to -2.8 ‰,respectively. He and C isotope systematics indicate that CO2 and CH4 in the CO2-rich gases originated predominantly from magmatic component mixed with crustal CO2 produced from carbonate. However, breakdown of organic matter and nearsurface processes accounts for the CH4 and CO2 in N2-rich gases. 3He/4He ratio distribution pattern suggests that mantlederived He and heat sources of high-temperature system in central Tengchong originate from a hidden magma reservoir at subsurface. CO2-rich gases with the highest 3He/4He ratio (5.2 Ra) may be representative of the Tengchong magmatic component. Compared with MORB, this relative low 3He/4He ratio could be fully attributed to either deep crustal contamination, or radioactive aging, or past contamination of the local mantle by U- and Th-rich subducted crustal material.However, a combination of low 3He/4He, high radiogenic 4He/40Ar ratio and identical CO2/3He and δ13Cco2 relative to MORB may suggest addition of prior subductedd crsustal material (ca 1%-2%) to the MORB reservoir around 1.3 Ga ago,which is essentially compatible with the LIL-elements, and Sr-Nd-Pb isotopes of volcanic rocks.

  17. Resolving high precision U-Pb ages from Tertiary plutons with complex zircon systematics

    Mcclelland, William C.; Mattinson, James M.


    Success in establishing high precision crystallization ages with the U/Pb zircon method is highly dependent on the ability to isolate or remove the effects of inherited xenocrystic components or secondary lead-loss, or the combined effects of both. Current "conventional" single crystal and ion probe (SHRIMP) methods are successfully applied to Paleozoic and older samples but typically suffer from imprecision when applied to younger (Mesozoic-Cenozoic) samples due to generally reduced radiogenic lead concentrations. Here we apply a series of intense partial dissolution steps to multigrain zircon fractions from a series of Paleocene tonalitic to granodioritic intrusive rocks from southeastern Alaska. The zircon systematics are complicated by both minor inheritance and postcrystallization lead-loss. Physical and isotopic evidence demonstrate that the partial dissolution steps preferentially remove outer layers susceptible to lead loss, as well as core regions containing inherited components. The final residues are often hollow shells of low-U primary igneous zircon that yield highly precise, reproducible, and concordant ages. The resulting age determinations commonly statistically differ at the 95% confidence level from ages based on apparently concordant, but less precise conventional isotope dilution analyses, the uncertainties of which masked minor, subtle isotopic complexities. This observation strongly cautions against basing age assignments of samples yielding slightly discordant data on (1) single "concordant" analyses accompanied by an array of discordant data or (2) the mean of several 206Pb/ 238U or 207Pb/ 206Pb ages. The step-wise dissolution technique allows age determinations on young, relatively low U and Pb zircons at a resolution not currently possible with techniques such as single-grain conventional or spot ion probe analyses. Widespread application of the technique will likely prove instrumental in resolving detailed magmatic histories of igneous

  18. Deformation of C isotopes

    Kanada-Enyo, Y


    Systematic analysis of the deformations of proton and neutron densities in even-even C isotopes was done based on the method of antisymmetrized molecular dynamics. The $E2$ transition strength was discussed in relation to the deformation. We analyze the $B(E2;2^+_1\\to 0^+_1)$ in $^{16}$C, which has been recently measured to be abnormally small. The results suggest the difference of the deformations between proton and neutron densities in the neutron-rich C isotopes. It was found that stable proton structure in C isotopes plays an important role in the enhancement the neutron skin structure as well as in the systematics of $B(E2)$ in the neutron-rich C.

  19. Perchlorate isotope forensics

    Böhlke, J.K.; Sturchio, N.C.; Gu, B.; Horita, J.; Brown, G.M.; Jackson, W.A.; Batista, J.; Hatzinger, P.B.


    Perchlorate has been detected recently in a variety of soils, waters, plants, and food products at levels that may be detrimental to human health. These discoveries have generated considerable interest in perchlorate source identification. In this study, comprehensive stable isotope analyses ( 37Cl/35Cl and 18O/17O/ 16O) of perchlorate from known synthetic and natural sources reveal systematic differences in isotopic characteristics that are related to the formation mechanisms. In addition, isotopic analyses of perchlorate extracted from groundwater and surface water demonstrate the feasibility of identifying perchlorate sources in contaminated environments on the basis of this technique. Both natural and synthetic sources of perchlorate have been identified in water samples from some perchlorate occurrences in the United States by the isotopic method. ?? 2005 American Chemical Society.

  20. Low-Mass Dark Matter Search Results and Radiogenic Backgrounds for the Cryogenic Dark Matter Search

    Pepin, Mark David [Univ. of Minnesota, Minneapolis, MN (United States)


    An ever-increasing amount of evidence suggests that approximately one quarter of the energy in the universe is composed of some non-luminous, and hitherto unknown, “dark matter”. Physicists from numerous sub-fields have been working on and trying to solve the dark matter problem for decades. The common solution is the existence of some new type of elementary particle with particular focus on weakly interacting massive particles (WIMPs). One avenue of dark matter research is to create an extremely sensitive particle detector with the goal of directly observing the interaction of WIMPs with standard matter. The Cryogenic Dark Matter Search (CDMS) project operated at the Soudan Underground Laboratory from 2003–2015, under the CDMS II and SuperCDMS Soudan experiments, with this goal of directly detecting dark matter. The next installation, SuperCDMS SNOLAB, is planned for near-future operation. The reason the dark-matter particle has not yet been observed in traditional particle physics experiments is that it must have very small cross sections, thus making such interactions extremely rare. In order to identify these rare events in the presence of a background of known particles and interactions, direct detection experiments employ various types and amounts of shielding to prevent known backgrounds from reaching the instrumented detector(s). CDMS utilized various gamma and neutron shielding to such an effect that the shielding, and other experimental components, themselves were sources of background. These radiogenic backgrounds must be understood to have confidence in any WIMP-search result. For this dissertation, radiogenic background studies and estimates were performed for various analyses covering CDMS II, SuperCDMS Soudan, and SuperCDMS SNOLAB. Lower-mass dark matter t c2 inent in the past few years. The CDMS detectors can be operated in an alternative, higher-biased, mode v to decrease their energy thresholds and correspondingly increase their sensitivity

  1. Combined Whole-Rock to Nano-Scale Investigations Reveal Contrasting Response of Pt-Os and Re-Os Isotope Systematics During Magmatic and Post-Magmatic Processes

    Coggon, J. A.; Luguet, A.; Lorand, J. P.; Fonseca, R.; Wainwright, A.; Appel, P.; Hoffmann, J. E.; Nowell, G. M.


    Advances in single-grain and micro- and nano-analytical techniques in recent years have been particularly important to the study of highly siderophile elements (HSE) and have contributed significantly to our knowledge and understanding of their host phases and behaviour. Furthermore, whole-rock- to nano-scale studies provide new perspectives for investigation of HSE isotope systematics. Recent multi-scale 187Re-187Os and 190Pt-186Os studies facilitate comparison, to a previously unattainable degree, of the differing responses of these two decay systems to magmatic and post-magmatic processes. It is well established that mafic-ultramafic melts are sensitive to disturbance of their Re-Os isotope systematics by crustal assimilation, due to the incompatibility and resulting enrichment of Re in crustal lithologies. In contrast the very long half-life and extremely low atomic abundance of 190Pt, combined with relatively low Pt concentrations in crustal rocks, generally render the Pt-Os isotope system insensitive to modification during assimilation. However, using new single chromite grain data (Coggon et al., 2015) from the >3.811 Ga Ujaragssuit nunât layered ultramafic body, Greenland, we show that it is possible to distinguish two distinct episodes of 187Os/188Os modification; Country rock contamination of the parent melt was followed by later metamorphic disturbance of the isotope system. The Pt-Os data (Coggon et al., 2013) from the same samples show no evidence of crustal assimilation, but preserve signatures of mantle melting at ~4.1 Ga as well as disturbance during metamorphism. Macro- to micro-petrographic study clearly demonstrates that Pt, Re and Os are hosted by different mineral phases, of different origins, in these samples. This, together with the physical parameters of the decay systems reported above, leads to the dissimilar behaviour and response of the 187Re-187Os and 190Pt-186Os isotope systems during both magmatic and post-magmatic processes and

  2. The role of impact and radiogenic heating in the early thermal evolution of Mars

    S Sahijpal; G K Bhatia


    The planetary differentiation models of Mars are proposed that take into account core–mantle and coremantle–crust differentiation. The numerical simulations are presented for the early thermal evolution of Mars spanning up to the initial 25 million years (Ma) of the early solar system, probably for the first time, by taking into account the radiogenic heating due to the short-lived nuclides, 26Al and 60Fe. The influence of impact heating during the accretion of Mars is also incorporated in the simulations. The early accretion of Mars would necessitate a substantial role played by the short-lived nuclides in its heating. 26Al along with impact heating could have provided sufficient thermal energy to the entire body to substantially melt and trigger planetary scale differentiation. This is contrary to the thermal models based exclusively on the impact heating that could not produce widespread melting and planetary differentiation. The early onset of the accretion of Mars perhaps within the initial ∼1.5 Ma in the early solar system could have resulted in substantial differentiation of Mars, provided, it accreted over the timescale of ∼1 Ma. This seems to be consistent with the chronological records of the Martian meteorites.

  3. The role of impact and radiogenic heating in the early thermal evolution of Mars

    Sahijpal, S


    The planetary differentiation models of Mars are proposed that take into account core-mantle and core-mantle-crust differentiation. The numerical simulations are presented for the early thermal evolution of Mars spanning up to the initial 25 million years (Ma) of the early solar system, probably for the first time, by taking into account the radiogenic heating due to the short-lived nuclides, 26Al and 60Fe. The influence of impact heating during the accretion of Mars is also incorporated in the simulations. The early accretion of Mars would necessitate a substantial role played by the short-lived nuclides in its heating. 26Al along with impact heating could have provided sufficient thermal energy to the entire body to substantially melt and trigger planetary scale differentiation. This is contrary to the thermal models based exclusively on the impact heating that could not produce widespread melting and planetary differentiation. The early onset of the accretion of Mars perhaps within the initial ~1.5 Ma in t...

  4. Deciphering petrogenic processes using Pb isotope ratios from time-series samples at Bezymianny and Klyuchevskoy volcanoes, Central Kamchatka Depression

    Kayzar, Theresa M.; Nelson, Bruce K.; Bachmann, Olivier; Bauer, Ann M.; Izbekov, Pavel E.


    The Klyuchevskoy group of volcanoes in the Kamchatka arc erupts compositionally diverse magmas (high-Mg basalts to dacites) over small spatial scales. New high-precision Pb isotope data from modern juvenile (1956-present) erupted products and hosted enclaves and xenoliths from Bezymianny volcano reveal that Bezymianny and Klyuchevskoy volcanoes, separated by only 9 km, undergo varying degrees of crustal processing through independent crustal columns. Lead isotope compositions of Klyuchevskoy basalts-basaltic andesites are more radiogenic than Bezymianny andesites (208Pb/204Pb = 37.850-37.903, 207Pb/204Pb = 15.468-15.480, and 206Pb/204Pb = 18.249-18.278 at Bezymianny; 208Pb/204Pb = 37.907-37.949, 207Pb/204Pb = 15.478-15.487, and 206Pb/204Pb = 18.289-18.305 at Klyuchevskoy). A mid-crustal xenolith with a crystallization pressure of 5.2 ± 0.6 kbars inferred from two-pyroxene geobarometry and basaltic andesite enclaves from Bezymianny record less radiogenic Pb isotope compositions than their host magmas. Hence, assimilation of such lithologies in the middle or lower crust can explain the Pb isotope data in Bezymianny andesites, although a component of magma mixing with less radiogenic mafic recharge magmas and possible mantle heterogeneity cannot be excluded. Lead isotope compositions for the Klyuchevskoy Group are less radiogenic than other arc segments (Karymsky—Eastern Volcanic Zone; Shiveluch—Northern Central Kamchatka Depression), which indicate increased lower-crustal assimilation beneath the Klyuchevskoy Group. Decadal timescale Pb isotope variations at Klyuchevskoy demonstrate rapid changes in the magnitude of assimilation at a volcanic center. Lead isotope data coupled with trace element data reflect the influence of crustal processes on magma compositions even in thin mafic volcanic arcs.

  5. Systematics of a Clumped Isotope-Based Reconstruction of Temperature and Precipitation Water δ18O from Late Pleistocene and Holocene Archives of the Chinese Loess Plateau

    Bricker, H. L.; Mitsunaga, B.; Mering, J. A.; Eagle, R.; Li, G.; Tripati, A. K.


    The Chinese Loess Plateau lies at the terminus of the East Asian Monsoon, a massive meteorological phenomenon that provides water to up to a quarter of the world's population. This event has been hypothesized to exhibit shifts in intensity and location over geologic time in response to changes in glaciation and climate forcing, including associated abrupt events, during glacial-interglacial cycles, and over longer (>106) year timescales. We propose to reconstruct and evaluate processes that affect carbonate δ18O and carbonate "clumped" isotope thermometry signatures of archives from the Loess Plateau. We will examine modern and Holocene (5,000-10,000 year old) snail specimens (Sp. Cathaica) from four locations within the Plateau: Yichuan, Xifeng, Mangshan, and Lingtai. We will additionally employ the evaporative flux balance model of Balakrishnan (2005) to analyze snail aragonite crystallization in oxygen isotope equilibrium as a proxy measurement for δ18O evaporation. We will then compare these measurements with empirical, modern-day meteoric δ18O and temperature data from local weather stations and the Global Network of Isotopes in Precipitation (GNIP), as well as data from in situ carbonate nodular loess concretions. These comparisons will allow us to assess the seasonality of growth and determine if non-climatological parameters (e.g., kinetic effects) dominate isotopic signatures, in order to assess if these proxies represent. If the clumped isotope data conforms to these independently-derived measurements, clumped isotope thermometry may be a valid and robust method for characterizing past environmental changes, and we can extend this procedure to proxy materials.

  6. Evaluating crustal contributions to enriched shergottites from the petrology, trace elements, and Rb-Sr and Sm-Nd isotope systematics of Northwest Africa 856

    Ferdous, J.; Brandon, A. D.; Peslier, A. H.; Pirotte, Z.


    The origin of the incompatible trace element (ITE) characteristics of enriched shergottites has been critical for examining two contradicting scenarios to explain how these Martian meteorites form. The first scenario is that it reflects ITE enrichment in an early-formed mantle reservoir whereas the second scenario attributes it to assimilation of ancient Martian crust (∼4-4.5 Ga) by ITE-depleted magmas. Strongly differentiated shergottite magmas may yield added constraints for determining which scenario can best explain this signature in enriched shergottites. The meteorite Northwest Africa (NWA) 856 is a basaltic shergottite that, unlike many enriched shergottites, lacks olivine and has undergone extensive differentiation from more primitive parent magma. In similarity to other basaltic shergottites, NWA 856 is comprised primarily of compositionally zoned clinopyroxenes (45% pigeonite and 23% augite), maskelynite (23%) and accessory minerals such as ulvöspinel, merrillite, Cl-apatite, ilmenite, pyrrhotite, baddeleyite and silica polymorph. The CI-chondrite normalized rare earth element (REE) abundance patterns for its maskelynite, phosphates, and its whole rock are flat with corresponding light-REE depletions in clinopyroxenes. The 87Rb-87Sr and 147Sm-143Nd internal isochron ages are 162 ± 14 (all errors are ±2σ) Ma and 162.7 ± 5.5 Ma, respectively, with an initial εNdI = -6.6 ± 0.2. The Rb-Sr isotope systematics are affected by terrestrial alteration resulting in larger scatter and a less precise internal isochron age. The whole rock composition is used in MELTS simulations to model equilibrium and fractional crystallization sequences to compare with the crystallization sequence from textural observations and to the mineral compositions. These models constrain the depth of initial crystallization to a pressure range of 0.4-0.5 GPa (equivalent to 34-42 km) in anhydrous conditions at the Fayalite-Magnetite-Quartz buffer, and consistently reproduce the

  7. Chlorine isotopes potential as geo-chemical tracers

    Shirodkar, P.V.; Pradhan, U.K.; Banerjee, R.

    The potential of chlorine isotopes as tracers of geo-chemical processes of earth and the oceans is highlighted based on systematic studies carried out in understanding the chlorine isotope fractionation mechanism, its constancy in seawater and its...

  8. Isotopic (Pb, Sr, Nd, C, O) evidence for plume-related sampling of an ancient, depleted mantle reservoir

    Chen, Wei; Simonetti, Antonio


    The exact mantle source for carbonatite melts remains highly controversial. Despite their predominant occurrence within continental (lithospheric) domains, the radiogenic isotope data from young (oceanic island basalts (OIBs). This feature suggests an intimate petrogenetic relationship with asthenospheric mantle. New Pb, Sr, C, and O isotopic data are reported here for constituent minerals from the Oka carbonatite complex, which is associated with the Cretaceous Monteregian Igneous Province (MIP), northeastern North America. The Pb isotope data define linear arrays in Pb-Pb isotope diagrams, with the corresponding Sr isotope ratios being highly variable (0.70314-0.70343); both these features are consistent with open system behavior involving at least three distinct mantle reservoirs. Compared to the isotope composition of known mantle sources for OIBs and carbonatite occurrences worldwide, the least radiogenic 207Pb/204Pb (14.96 ± 0.07) and 208Pb/204Pb (37.29 ± 0.15) isotopic compositions relative to their corresponding 206Pb/204Pb ratios (18.86 ± 0.08) reported here are distinct, and indicate the involvement of an ancient depleted mantle (ADM) source. The extremely unradiogenic Pb isotope compositions necessitate U/Pb fractionation early in Earth's history (prior to 4.0 Ga ago) and growth via a multi-stage Pb evolution model. The combined stable (C and O) and radiogenic isotopic compositions effectively rule out crustal/lithosphere contamination during the petrogenetic history of the Oka complex. Instead, the isotopic variations reported here most likely result from the mixing of discrete, small volume partial melts derived from a heterogeneous plume source characterized by a mixed HIMU-EM1-ADM signature.

  9. Radiogenic neoplasia in thyroid and mammary clonogens. Progress report, January 1, 1991--December 31, 1991

    Clifton, K.H.


    We have developed rat thyroid and mammary clonogen transplantation systems for the study of radiogenic cancer induction at the target cell level in vivo. The epithelial cell populations of both glands contain small subpopulations of cells which are capable of giving rise to monoclonal glandular structures when transplanted and stimulated with appropriate hormones. During the end of the last grant year and the first half of the current grant year, we have completed analyses and summarized for publication: investigations on the relationship between grafted thyroid cell number and the rapidity and degree of reestablishment of the thyroid-hypothalamicpituitary axis in thyroidectomized rats maintained on a normal diet or an iodine deficient diet; studies of the persistence of, and the differentiation potential and functional characteristics of, the TSH- (thyrotropin-) responsive sub-population of clonogens during goitrogenesis, the plateau-phase of goiter growth, and goiter involution; studies of changes in the size of the clonogen sub-population during goitrogenesis, goiter involution and the response to goitrogen rechallenge; and the results of the large carcinogenesis experiment on the nature of the grafted thyroid cell number-dependent suppression of promotion/progression to neoplasia in grafts of radiation-initiated thyroid cells. We are testing new techniques for the culture, cytofluorescent analysis and characterization mammary epithelial cells and of clonogens in a parallel project, and plan to apply similar technology to the thyroid epithelial cells and clonogen population. Data from these studies will be used in the design of future carcinogenesis experiments on neoplastic initiation by high and low LET radiations and on cells interactions during the neoplastic process.

  10. Carbon dioxide and helium dissolved gases in groundwater at central Tenerife Island, Canary Islands: chemical and isotopic characterization

    Marrero-Diaz, Rayco; López, Dina; Perez, Nemesio M.; Custodio, Emilio; Sumino, Hirochika; Melián, Gladys V.; Padrón, Eleazar; Hernandez, Pedro A.; Calvo, David; Barrancos, José; Padilla, Germán; Sortino, Francesco


    Seismic-volcanic unrest was detected between 2004 and 2005 in the central and northwest zones of Tenerife Island (Canary Islands, Spain). With the aim of strengthening the program of geochemical and seismic-volcanic surveillance, a study of the origin, characteristics, and spatial distribution of dissolved carbon dioxide (CO2) and helium (He) gases in the volcanic aquifer of central Tenerife Island and around Teide volcano was carried out. This work also improves the hydrogeological and hydrogeochemical conceptual model of groundwater flow. Dissolved CO2 concentrations in sampled groundwater are several orders of magnitude higher than that of air-saturated water (ASW) suggesting a significant contribution of non-atmospheric CO2, mainly magmatic, confirmed through measurement of isotopic compositions (δ13CTDIC) and total dissolved inorganic carbon (TDIC) concentrations. A vertical stratification of dissolved CO2 and δ13CTDIC values was observed in the volcanic aquifer at the eastern region of Las Cañadas Caldera. Stratification seems to be controlled by both degree of magmatic CO2-water interaction and CO2 degassing and the original δ13Cco2(g) isotopic composition. The highest dissolved helium (4He) concentrations in groundwater seem to be related to radiogenic contributions resulting from water-rock interactions, and increase with residence time, instead of with endogenous magmatic inputs. Isotopic systematics show that the dissolved gases in groundwater of central Tenerife are variable mixtures of CO2-3He-rich fluids of volcanic-hydrothermal origin with both organic and atmospheric components. The results suggest that the eastern area of Las Cañadas Caldera, the South Volcanic Ridge, and the Teide summit cone are the areas most affected by degassing of the volcanic-hydrothermal system, and they are therefore the most suitable zones for future geochemical monitoring.

  11. Re-Os isotope evidence from Mesozoic and Cenozoic basalts for secular evolution of the mantle beneath the North China Craton

    Huang, Feng; Xu, Ji-Feng; Liu, Yong-Sheng; Li, Jie; Chen, Jian-Lin; Li, Xi-Yao


    The mechanism and process of lithospheric thinning beneath the North China Craton (NCC) are still debated. A key criterion in distinguishing among the proposed mechanisms is whether associated continental basalts were derived from the thinning lithospheric mantle or upwelling asthenosphere. Herein, we investigate the possible mechanisms of lithospheric thinning based on a systematic Re-Os isotopic study of Mesozoic to Cenozoic basalts from the NCC. Our whole-rock Re-Os isotopic results indicate that the Mesozoic basalts generally have high Re and Os concentrations that vary widely from 97.2 to 839.4 ppt and 74.4 to 519.6 ppt, respectively. They have high initial 187Os/188Os ratios ranging from 0.1513 to 0.3805, with corresponding variable γOs(t) values (+20 to +202). In contrast, the Re-Os concentrations and radiogenic Os isotope compositions of the Cenozoic basalts are typically lower than those of the Mesozoic basalts. The lowest initial 187Os/188Os ratios of the Cenozoic basalts are 0.1465 and 0.1479, with corresponding γOs(t) values of +15 and +16, which are within the range of ocean island basalts. These new Re-Os isotopic results, combined with the findings of previous studies, indicate that the Mesozoic basalts were a hybrid product of the melting of pyroxenite and peridotite in ancient lithospheric mantle beneath the NCC. The Cenozoic basalts were derived mainly from upwelling asthenosphere mixed with small amounts of lithospheric materials. The marked differences in geochemistry between the Mesozoic and Cenozoic basalts suggest a greatly reduced involvement of lithospheric mantle as the magma source from the Mesozoic to the Cenozoic. The subsequent lithospheric thinning of the NCC and replacement by upwelling asthenospheric mantle resulted in a change to asthenosphere-derived Cenozoic basalts.

  12. Sr, Nd, Pb Isotope geochemistry and magma evolution of the potassic volcanic rocks, Wudalianchi, Northeast China

    Junwen, W.; Guanghong, X.; Tatsumoto, M.; Basu, A.R.


    Wudalianchi volcanic rocks are the most typical Cenozoic potassic volcanic rocks in eastern China. Compositional comparisons between whole rocks and glasses of various occurrences indicate that the magma tends to become rich in silica and alkalis as a result of crystal differentiation in the course of evolution. They are unique in isotopic composition with more radiogenic Sr but less radiogenic Pb.87Sr /86 Sr is higher and143Nd/144Nd is lower than the undifferentiated global values. In comparison to continental potash volcanic rocks, Pb isotopes are apparently lower. These various threads of evidence indicate that the rocks were derived from a primary enriched mantle which had not been subjected to reworking and shows no sign of incorporation of crustal material. The correlation between Pb and Sr suggests the regional heterogeneity in the upper mantle in terms of chemical composition. ?? 1989 Institute of Geochemistry, Chinese Academy of Sciences.

  13. Isotope evolution in the HIMU reservoir beneath St. Helena: Implications for the mantle recycling of U and Th

    Hanyu, Takeshi; Kawabata, Hiroshi; Tatsumi, Yoshiyuki; Kimura, Jun-Ichi; Hyodo, Hironobu; Sato, Keiko; Miyazaki, Takashi; Chang, Qing; Hirahara, Yuka; Takahashi, Toshiro; Senda, Ryoko; Nakai, Shun'ichi


    HIMU (high-μ; 238U/204Pb) is a mantle reservoir that has been thought to form by subduction and subsequent storage of ancient oceanic crust and lithosphere in the mantle. In order to constrain the processes that acted on subducted materials over several billion years, we present precise Pb-Sr-Nd-Hf-He isotopic data together with 40Ar/39Ar and K/Ar ages of HIMU lavas from St. Helena in the Atlantic. Clinopyroxene separates were analyzed together with whole-rock samples to better describe the geochemical characteristics of the HIMU component. Although isotopic variations are small in the St. Helena lavas (20.6-21.0 for 206Pb/204Pb) between 12 and 8 Ma, the younger lavas have more HIMU-like isotopic compositions than the older lavas. The mixing arrays defined by these lavas are remarkably similar to those observed in HIMU lavas from Austral Islands in the Pacific, suggesting that the two HIMU reservoirs located in different mantle domains are characterized by similar isotopic compositions with radiogenic 206Pb/204Pb and 208Pb/204Pb, enriched Nd and Hf isotopes, depleted Sr isotopes, and radiogenic 3He/4He. However, there is a significant difference between the St. Helena and Austral Islands lavas in 207Pb/204Pb. The St. Helena lavas show systematically higher 207Pb/204Pb for a given 206Pb/204Pb. Lead isotope evolution models suggest that both HIMU reservoirs formed around 2 Ga; however, the HIMU reservoir for St. Helena is about 0.3 Ga older than that for Austral Islands. The relation between 206Pb/204Pb and 208Pb/204Pb could reflect the time-integrated κ (232Th/238U) in the components. The HIMU components for St. Helena and Austral Islands have κ values between 3.3 and 3.7, which are intermediate between the present-day fresh mid-ocean ridge basalts (MORB; 2.6-3.2) and the chondritic silicate Earth (∼4). This is consistent with the model that the HIMU precursor is subducted oceanic crust created around 2 Ga from depleted upper mantle, in which κ monotonously

  14. Geochemical and isotopic insights into the assembly, evolution and disruption of a magmatic plumbing system before and after a cataclysmic caldera-collapse eruption at Ischia volcano (Italy)

    Brown, R. J.; Civetta, L.; Arienzo, I.; D'Antonio, M.; Moretti, R.; Orsi, G.; Tomlinson, E. L.; Albert, P. G.; Menzies, M. A.


    New geochemical and isotopic data on volcanic rocks spanning the period ~75-50 ka BP on Ischia volcano, Italy, shed light on the evolution of the magmatic system before and after the catastrophic, caldera-forming Monte Epomeo Green Tuff (MEGT) eruption. Volcanic activity during this period was influenced by a large, composite and differentiating magmatic system, replenished several times with isotopically distinct magmas of deep provenance. Chemical and isotopic variations highlight that the pre-MEGT eruptions were fed by trachytic/phonolitic magmas from an isotopically zoned reservoir that were poorly enriched in radiogenic Sr and became progressively less radiogenic with time. Just prior to the MEGT eruption, the magmatic system was recharged by an isotopically distinct magma, relatively more enriched in radiogenic Sr with respect to the previously erupted magmas. This second magma initially fed several SubPlinian explosive eruptions and later supplied the climactic, phonolitic-to-trachytic MEGT eruption(s). Isotopic data, together with erupted volume estimations obtained for MEGT eruption(s), indicate that >5-10 km3 of this relatively enriched magma had accumulated in the Ischia plumbing system. Geochemical modelling indicates that it accumulated at shallow depths (4-6 km), over a period of ca. 20 ka. After the MEGT eruption, volcanic activity was fed by a new batch of less differentiated (trachyte-latite) magma that was slightly less enriched in radiogenic Sr. The geochemical and Sr-Nd-isotopic variations through time reflect the upward flux of isotopically distinct magma batches, variably contaminated by Hercynian crust at 8-12 km depth. The deep-sourced latitic to trachytic magmas stalled at shallow depths (4-6 km depth), differentiated to phonolite through crystal fractionation and assimilation of a feldspar-rich mush, or ascended directly to the surface and erupted.

  15. Small scale heterogeneity of Phanerozoic lower crust: evidence from isotopic and geochemical systematics of mid-Cretaceous granulite gneisses, San Gabriel Mountains, southern California

    Barth, A.P.; Wooden, J.L.; May, D.J.


    An elongate belt of mid-Cretaceous, compositionally banded gneisses and granulites is exposed in Cucamonga terrane, in the southeastern foothills of the San Gabriel Mountains of southern California. Banded gneisses include mafic granulites of two geochemical types: type 1 rocks are similar to high Al arc basalts and andesites but have higher HFSE (high-field-strength-element) abundances and extremely variable LILE (largeion-lithophile-element) abundances, while type 2 rocks are relatively low in Al and similar to alkali rich MOR (midocean-ridge) or intraplate basalts. Intercalated with mafic granulites are paragneisses which include felsic granulites, aluminous gneisses, marble, and calc-silicate gneisses. Type 1 mafic granulites and calcic trondhjemitic pegmatites also oceur as cross-cutting, synmetamorphic dikes or small plutons. Small-scale heterogeneity of deep continental crust is indicated by the lithologic and isotopic diversity of intercalated ortho-and paragneisses exposed in Cucamonga terrane. Geochemical and isotopic data indicate that K, Rb, and U depletion and Sm/Nd fractionation were associated with biotite +/- muscovite dehydration reactions in type 1 mafic granulites and aluminous gneisses during high-grade metamorphism. Field relations and model initial isotopic ratios imply a wide range of protolith ages, ranging from Early Proterozoic to Phanerozoic. ?? 1992 Springer-Verlag.

  16. Systematic decay studies of even-even $132-138$^Nd, $144-158$^Gd, $176-196$^Hg and $192-198$^Pb isotopes

    Santhosh, K P


    The alpha and cluster decay properties of the $132-138$^Nd, $144-158$^Gd, $176-196$^Hg and $192-198$^Pb even-even isotopes in the two mass regions A = 130-158 and A = 180-198 are analysed using the Coulomb and Proximity Potential Model. On examining the clusters at corresponding points in the cold valleys (points with same A_2) of the various isotopes of a particular nucleus we find that at certain mass numbers of the parent nuclei, the clusters emitted are getting shifted to the next lower atomic number. It is interesting to see that the change in clusters appears at those isotopes where a change in shape is occurring correspondingly. Such a change of clusters with shape change is studied for the first time in cluster decay. The alpha decay half lives of these nuclei are computed and these are compared with the available experimental alpha decay data. It is seen that the two are in good agreement. On making a comparison of the alpha half lives of the normal deformed and super deformed nuclei, it can be seen ...

  17. He-Ar Isotopic Systematics of Fluid Inclusions in Pyrites from PGE-polymetallic Deposits in Lower Cambrian Black Rock Series, South China

    SUN Xiaoming; WANG Min; XUE Ting; MA Mingyang; LI Yinhe


    He-Ar isotopic compositions of fluid inclusions trapped in pyrites from some representative PGEpolymetallic deposits in Lower Cambrian black rock series in South China were analyzed by using an inert gas isotopic mass spectrometer. The results show that the ore-forming fluids possess a low 3He/4He ratio, varying from 0.43x10-8 to 26.39×10-8, with corresponding R/Ra value of 0.003-0.189. The 40Ar/36Ar ratios are 258-287, close to those of airsaturated water (ASW). He-Ar isotopic indicator studies show that the ore-forming fluids were mainly derived from the formation water or basinal hot brine and sea water, while the content of mantle-derived fluid or deep-derived magmatic water might be negligible. The PGE-polymetallic mineralization might be related to the evolution of the Caledonian miogeosynclines distributed along the southern margin of the Yangtze Craton. During the Early Cambrian, the formation water or basinal hot brine trapped in Caledonian basins which accumulated giant thick sediments was expelled and migrated laterally along strata because of the pressure generated by overlying sediments. The basinal hot brine ascended along faults, mixed with sea water and finally deposited ore minerals.

  18. Stable isotope analysis of the human body. What isotopes in our tissue can reveal and what not; Stabilisotopenanalysen am Menschen. Was die Isotopie unseres Koerpergewebes ueber uns verraet- und was nicht

    Goerger, Marlene [Technische Univ. Darmstadt (Germany)


    Most isotopes in the natural environment are stable but there are radioactive isotopes. Premordial radionuclides are nuclides that exist since the development of the earth crust. Cosmogenic radionuclides are generated due to cosmic radiation (protons, electrons, ionized atoms) - for instance C-14. Radiogenic nuclides are daughter products of radioactive nuclei. Anthropogenic radionuclides are generated due to human activities. Deviations from a ''normal'' isotope distribution are used for environmental impact analysis and forensic purposes. The human provenance project was stopped.

  19. Holocene Provenance Identification and Climate Control of Indus Basin By Using Radiogenic Techniques and Clay Mineralogy



    Two commonly used isotopic methods (Zircon U-Pb dating and K-feldspar Pb dating) were employed for the Holocene provenance identification within the Indus basin. Zircon grains from the upper Indus are generally younger than 200 Ma in contrast with the eastern tributaries, which show varying inputs from Greater and Lesser Himalayan sources. The Sutlej river is very rich in Lesser Himalayan-sourced sediments, while the Chenab is mostly eroded from the Greater Himalaya. Grains younger than 200 M...

  20. Uranium-Lead Zircon Ages and Sr, Nd, and Pb Isotope Geochemistry of Selected Plutonic Rocks from Western Idaho

    Unruh, Daniel M.; Lund, Karen; Kuntz, Mel A.; Snee, Lawrence W.


    Across the Salmon River suture in western Idaho, where allochthonous Permian to Cretaceous oceanic rocks are juxtaposed against Proterozoic North American rocks, a wide variety of plutonic rocks are exposed. Available data indicate much variation in composition, source, and structural state of these plutons. The plutonic rocks were long described as the western border zone of the Cretaceous Idaho batholith but limited pre-existing age data indicate more complicated origins. Because the affinity and age of the plutonic rocks cannot be reliably determined from field relations, TIMS U-Pb dating in conjunction with Sr, Nd, and Pb isotopic studies of selected plutons across the suture in western Idaho were undertaken. The data indicate three general groups of plutons including (1) those that intruded the island arc terranes during the Triassic and Jurassic, those that intruded near the western edge of oceanic rocks along the suture in the Early Cretaceous, and the plutons of the Idaho batholith that intruded Proterozoic North American rocks in the Late Cretaceous. Plutons that intruded Proterozoic North American rocks commonly include xenocrystic zircons and in several cases, ages could not be determined. The least radiogenic Sr and most radiogenic Nd are found among the Blue Mountains superterrane island arc samples. Suture-zone plutons have isotopic characteristics that span the range between Idaho batholith and island arc samples but mostly follow island arc signatures. Plutons of the Idaho batholith have the most radiogenic initial Pb and Sr ratios and the least radiogenic Nd of the samples analyzed.

  1. Ediacaran Palaeozoic tectonic evolution of the Ossa Morena and Central Iberian zones (SW Iberia) as revealed by Sm Nd isotope systematics

    López-Guijarro, Rafael; Armendáriz, Maider; Quesada, Cecilio; Fernández-Suárez, Javier; Murphy, J. Brendan; Pin, Christian; Bellido, Felix


    Sm-Nd isotopic analyses of Palaeozoic sedimentary and igneous rocks in the southwest Iberian Massif (western end of the European Variscan Belt) are presented in order to unravel its complex poly-orogenic evolution during the closure of the Rheic Ocean and the amalgamation of Pangea. The Gondwanan margin in southwest Iberia SW Iberia is subdivided into the Ossa Morena and Central Iberian zones, separated by the Badajoz-Córdoba Shear Zone which represents a cryptic suture zone between these terranes. The relationships between these terranes, and between units preserved within the suture zone (e.g. the Sierra Albarrana Group) during the Palaeozoic and Neoproterozoic are controversial. Sm-Nd isotopic studies of representative sedimentary sequences covering the entire pre-Variscan record of the Ossa Morena and Central Iberian zones show very similar characteristics from the uppermost Ediacaran onwards. These data indicate that their accretion to one another must have been completed by the Late Neoproterozoic-Ediacarin that time (an event assigned to Cadomian orogeny) and that they never separated substantially from each other since that time. The Sm-Nd isotopic composition of the Sierra Albarrana Group metasedimentary rocks is similar to that of the pre-Cadomian sequences of the Ossa Morena Zone (Serie Negra), suggesting derivation from a common source. The common provenance of the Palaeozoic sequences in the two zones is identical to that of the pre-Cadomian Serie Negra of the Ossa Morena Zone, which in accordance with the data presented herein and published U-Pb zircon data indicates a West African affinity.

  2. Genesis and open-system evolution of Quaternary magmas beneath southeastern margin of Tibet: Constraints from Sr-Nd-Pb-Hf isotope systematics

    Zou, Haibo; Ma, Mingjia; Fan, Qicheng; Xu, Bei; Li, Shuang-Qing; Zhao, Yongwei; King, David T.


    Post-collisional volcanic rocks on the Tibetan Plateau and its margins contain valuable information about the geodynamic processes associated with this Cenozoic continent-continent collision. The Quaternary Tengchong volcanic field at the southeastern margin of the Tibetan Plateau formed high-potassium calc-alkaline volcanic rocks. Herein, we present comprehensive Nd-Sr-Pb-Hf isotopic and elemental data for trachybasalts, basaltic trachyandesites, and trachyandesites from four Quaternary Tengchong volcanoes (Maanshan, Dayingshan, Heikongshan, and Laoguipo) in order to understand their magma genesis and evolution as well as tectonic significance. Good correlations between SiO2 content and the ratios 87Sr/86Sr, 143Nd/144Nd, 206Pb/204Pb, and 177Hf/176Hf for these Quaternary volcanics strongly suggest that the combined assimilation and fractional crystallization (AFC) was an important process in the origin of basaltic trachyandesites and trachyandesites. High Y and Yb contents and low Sr/Y ratios of these basaltic trachyandesites and trachyandesites are uncharacteristic of adakites that formed by partial melting of eclogitic lower crust or partial melting of basaltic oceanic crust with eclogite as a restite. A combined assimilation-fractional crystallization model is proposed for these basaltic trachyandesites and trachyandesites. Nd-Sr-Pb-Hf isotopes for the uncontaminated Tengchong magma (trachybasalts with SiO2 5.5% wt.%) reflect a heterogeneous enriched mantle source. High Th/U, Th/Ta, and Rb/Nb ratios and Nd-Sr-Pb-Hf isotope characteristics of the uncontaminated magmas suggest that the enriched mantle beneath Tengchong formed as a result of subduction of clay-rich sediments, which probably came from the Indian continental plate. Partial melting of the enriched mantle was generated by deep continental subduction coupled with recent regional extension in the Tengchong area.

  3. PGE, Re-Os, and Mo isotope systematics in Archean and early Proterozoic sedimentary systems as proxies for redox conditions of the early Earth

    Siebert, C.; Kramers, J. D.; Meisel, Th.; Morel, Ph.; Nägler, Th. F.


    Re-Os data and PGE concentrations as well as Mo concentrations and isotope data are reported for suites of fine clastic sediments and black shales from the Barberton Greenstone Belt, South Africa (Fig Tree and Moodies Groups, 3.25-3.15 Ga), the Belingwe Greenstone Belt, Zimbabwe (Manjeri Formation, ca. 2.7 Ga) and shales from the Witwatersrand, Ventersdorp and Transvaal Supergroups, South Africa ranging from 2.95 to 2.2 Ga. Moderately oxidizing conditions are required to mobilize Re and Mo in the environment, Mo fractionation only occurs in solution, and these parameters thus have potential use as paleoredox proxies for the early Earth. PGE + Re abundance patterns of Barberton Greenstone Belt sediments are uniform and very similar in shape to those of komatiites. This indicates (1) that the PGE came from a source of predominantly ultramafic composition and, (2) that PGE were transported and deposited essentially in particulate form. Sediments from the younger Belingwe Greenstone Belt show more fractionated PGE + Re patterns and have Re/Os ratios 10 to 100× higher than those of Barberton sediments. Their PGE abundance patterns and Re/Os ratios are intermediate between those of the mid-Archean shales and Neoproterozoic to Recent black shales. They reflect scavenging of Re from solution in the sedimentary environment. δ 98/95Mo values of black shales of all ages correlate with their concentrations. The Barberton Greenstone Belt samples have ˜1-3 ppm Mo, similar to a granitoid-basaltic source. This Mo has δ 98/95Mo between -1.9 and -2.4‰ relative to present day mean ocean water molybdenum, MOMO and is thus not isotopically fractionated relative to such a source. Similar to the PGE this indicates transport in solid form. Sediments from the Belingwe Greenstone Belt show in part enhanced Mo concentrations (up to 6 ppm) and Mo isotope fractionation (δ 98/95Mo up to -1.4‰ relative to MOMO). The combined PGE + Re and Mo data show mainly reducing conditions in the

  4. The reliability of ∼2.9 Ga old Witwatersrand banded iron formations (South Africa) as archives for Mesoarchean seawater: Evidence from REE and Nd isotope systematics

    Viehmann, Sebastian; Bau, Michael; Smith, Albertus J. B.; Beukes, Nicolas J.; Dantas, Elton L.; Bühn, Bernhard


    Pure marine chemical sediments, such as (Banded) Iron Formations, (B)IFs, are archives of geochemical proxies for the composition of Precambrian seawater and may provide information about the ancient hydrosphere-atmosphere system. We here present rare earths and yttrium (REY) and high precision Sm-Nd isotope data of ∼2.90 Ga old Superior-type BIFs from the Witwatersrand Supergroup, South Africa, and compare those with data for near-contemporaneous BIFs from the correlative Pongola Supergroup (Superior-type BIF) and from the Pietersburg Greenstone Belt (Algoma-type IF), respectively. All Witwatersrand samples studied display the typical general REY distribution of Archean seawater, but their REY anomalies are less pronounced and their immobile element concentrations are higher than those of other pure (B)IFs. These observations indicate the presence of significant amounts of detrital aluminosilicates in the Witwatersrand BIFs and question the reliability of the Contorted Bed and Water Tower BIFs (Parktown Formation, West Rand Group) as archives of Mesoarchean seawater. Significant post-depositional alteration of the REY budget and the Sm-Nd isotope system is not observed. The Nd isotopic compositions of the purest BIF samples, i.e. the most reliable archives for Witwatersrand seawater, show initial εNd values between -3.95 and -2.25. This range is more negative than what is observed in ambient shales, indicating a decoupling of suspended and dissolved loads in the "near-shore" Witwatersrand Basin seawater. However, εNd range overlaps with that of the correlative Pongola BIF (Alexander et al., 2008). The deeper-water Algoma-type Pietersburg BIF shows more positive (i.e. more mantle-like) εNd2.9Ga values, supporting the hypothesis that a significant amount of its REY inventory was derived from black smoker-style, high-temperature hydrothermal fluids that had altered seafloor basalts. In marked contrast, the dissolved REY budgets (including the Nd isotopic

  5. Isotopic and trace element characteristics of rhyolites from the Valles Caldera, New Mexico. Final technical report

    Self, S.; Sykes, M.L. [Hawaii Univ., Honolulu, HI (United States). Dept. of Geology and Geophysics; Wolff, J.A. [Texas Univ., Arlington, TX (United States). Dept. of Geology; Skuba, C.E. [McMaster Univ., Hamilton, ON (Canada). Dept. of Geology


    This report is a summary of work supported by DOE grant No. DE-FGO5-87ER13795 that was completed or is still in progress. The stated purpose of this grant was to collect geochemical information (trace element, radiogenic isotope and stable oxygen and hydrogen isotope) on samples from core holes VC-I and VC-2a in the Valles caldera in order to establish a consistent detailed intracaldera stratigraphy and relate this to extracaldera volcanic rock units of the Jemez Mountains. Careful stratigraphic control of the intracaldera units is necessary to evaluate models of caldera formation, ignimbrite deposition, and resurgence. Combined stable and radiogenic isotope and trace element data will also provide major insights to petrogenesis of the Bandelier magma system. The composition of non-hydrothermally altered samples from outflow units of the Bandelier Tuff and related volcanics must be known to assess isotopic variations of intracaldera ignimbrite samples. On detailed examination of the VC-2a core samples, it became apparent that hydrothermal alteration is so extensive that no geochemical information useful for stratigraphic fingerprinting or petrogenesis could be obtained, and that correlation with other intracaldera units and extracaldera units must be made on the basis of stratigraphic position and gross lithologic characteristics. Accordingly, we emphasize geochemical data from the extracaldera Bandelier Tuffs and related units which will be useful for comparison with proposed drill hole VC-4 and for any future studies of the region. The stable isotope, radiogenic isotope and trace element data obtained from this project, combined with existing major and trace element data for volcanic rocks from this area, provide an extensive data base essential to future Continental Scientific Drilling Program projects in the Jemez Mountains of New Mexico.

  6. Variation in the terrestrial isotopic composition and atomic weight of argon

    Böhlke, John Karl


    The isotopic composition and atomic weight of argon (Ar) are variable in terrestrial materials. Those variations are a source of uncertainty in the assignment of standard properties for Ar, but they provide useful information in many areas of science. Variations in the stable isotopic composition and atomic weight of Ar are caused by several different processes, including (1) isotope production from other elements by radioactive decay (radiogenic isotopes) or other nuclear transformations (e.g., nucleogenic isotopes), and (2) isotopic fractionation by physical-chemical processes such as diffusion or phase equilibria. Physical-chemical processes cause correlated mass-dependent variations in the Ar isotope-amount ratios (40Ar/36Ar, 38Ar/36Ar), whereas nuclear transformation processes cause non-mass-dependent variations. While atmospheric Ar can serve as an abundant and homogeneous isotopic reference, deviations from the atmospheric isotopic ratios in other Ar occurrences limit the precision with which a standard atomic weight can be given for Ar. Published data indicate variation of Ar atomic weights in normal terrestrial materials between about 39.7931 and 39.9624. The upper bound of this interval is given by the atomic mass of 40Ar, as some samples contain almost pure radiogenic 40Ar. The lower bound is derived from analyses of pitchblende (uranium mineral) containing large amounts of nucleogenic 36Ar and 38Ar. Within this interval, measurements of different isotope ratios (40Ar/36Ar or 38Ar/36Ar) at various levels of precision are widely used for studies in geochronology, water–rock interaction, atmospheric evolution, and other fields.

  7. Trace elements and Pb isotopes in soils and sediments impacted by uranium mining.

    Cuvier, A; Pourcelot, L; Probst, A; Prunier, J; Le Roux, G


    The purpose of this study is to evaluate the contamination in As, Ba, Co, Cu, Mn, Ni, Sr, V, Zn and REE, in a high uranium activity (up to 21,000Bq∙kg(-1)) area, downstream of a former uranium mine. Different geochemical proxies like enrichment factor and fractions from a sequential extraction procedure are used to evaluate the level of contamination, the mobility and the availability of the potential contaminants. Pb isotope ratios are determined in the total samples and in the sequential leachates to identify the sources of the contaminants and to determine the mobility of radiogenic Pb in the context of uranium mining. In spite of the large uranium contamination measured in the soils and the sediments (EF≫40), trace element contamination is low to moderate (2isotopic signature of the contaminated soils is strongly radiogenic. Measurements performed on the sequential leachates reveal inputs of radiogenic Pb in the most mobile fractions of the contaminated soil. Inputs of low-mobile radiogenic Pb from mining activities may also contribute to the Pb signature recorded in the residual phase of the contaminated samples. We demonstrate that Pb isotopes are efficient tools to trace the origin and the mobility of the contaminants in environments affected by uranium mining.

  8. A "Tail" Of Two Mines: Determining The Sources Of Lead In Mine Waters Using Pb Isotopes

    Cousens, B. L.; Allen, D. M.; Lepitre, M. E.; Mortensen, J. K.; Gabites, J. E.; Nugent, M.; Fortin, D.


    Acid mine drainage can be a significant environmental problem in regions where mine tailings are exposed to surface water and shallow groundwater flow. Whereas high metal concentrations in surface waters and groundwaters indicate that metals are being mobilized, these data do not uniquely identify the source of the contamination. The isotopic composition of Pb in mine waters is a superb tracer of Pb sources, because the isotopic composition of ore Pb is usually significantly different from that of host rocks, other surficial deposits, and aerosols. We have investigated metal mobility at two abandoned Pb-Zn mines in different geological settings: the sediment-hosted Sullivan Mine in southeastern British Columbia, and the New Calumet Mine of western Quebec that is hosted in metamorphic rocks of the Grenville Province. Ores from both mines have homogeneous Pb isotopic compositions that are much less radiogenic than surrounding host rocks. At Sullivan, the Pb isotopic compositions of water samples define a mixing line between Sullivan ore and at least one other more radiogenic end-member. Water samples with high Pb concentrations (0.002 to 0.3 mg/L) generally are acidic and have Pb isotope ratios equal to Sullivan ore, whereas waters with low Pb contents have near-neutral pH and have variably more radiogenic Pb isotope ratios. Thus not all the waters collected in the study area originate from Sullivan ore or mining operations, as previously thought. The dominant source of ore Pb in mine waters are the waste rock dumps. Based on their isotopic compositions, host shales or aerosols from the local Pb smelter are potential sources of non-Sullivan ore Pb; local glacial tills are an unlikely source due to their heterogeneous Pb isotopic composition. Similarly, at the New Calumet mine, water samples collected in direct contact with either ore at the surface or tailings have high Pb concentrations (up to 0.02 mg/L) and Pb isotope ratios equal to New Calumet Pb-Zn ore. However

  9. Confirmation of a meteoritic component in impact-melt rocks of the Chesapeake Bay impact structure, Virginia, USA - Evidence from osmium isotopic and PGE systematics

    Lee, Seung Ryeol; Horton, J. Wright; Walker, Richard J.


    The osmium isotope ratios and platinum-group element (PGE) concentrations of impact-melt rocks in the Chesapeake Bay impact structure were determined. The impact-melt rocks come from the cored part of a lower-crater section of suevitic crystalline-clast breccia in an 823 m scientific test hole over the central uplift at Cape Charles, Virginia. The 187Os/188Os ratios of impact-melt rocks range from 0.151 to 0.518. The rhenium and platinum-group element (PGE) concentrations of these rocks are 30-270× higher than concentrations in basement gneiss, and together with the osmium isotopes indicate a substantial meteoritic component in some impact-melt rocks. Because the PGE abundances in the impact-melt rocks are dominated by the target materials, interelemental ratios of the impact-melt rocks are highly variable and nonchondritic. The chemical nature of the projectile for the Chesapeake Bay impact structure cannot be constrained at this time. Model mixing calculations between chondritic and crustal components suggest that most impact-melt rocks include a bulk meteoritic component of 0.01-0.1% by mass. Several impact-melt rocks with lowest initial 187Os/188Os ratios and the highest osmium concentrations could have been produced by additions of 0.1%-0.2% of a meteoritic component. In these samples, as much as 70% of the total Os may be of meteoritic origin. At the calculated proportions of a meteoritic component (0.01-0.1% by mass), no mixtures of the investigated target rocks and sediments can reproduce the observed PGE abundances of the impact-melt rocks, suggesting that other PGE enrichment processes operated along with the meteoritic contamination. Possible explanations are 1) participation of unsampled target materials with high PGE abundances in the impact-melt rocks, and 2) variable fractionations of PGE during syn- to post-impact events.

  10. U-Pb zircon geochronology and Nd-Hf-O isotopic systematics of the Neoproterozoic Hadb adh Dayheen ring complex, Central Arabian Shield, Saudi Arabia

    Ali, Kamal A.; Jeon, Heejin; Andresen, Arild; Li, Shuang-Qing; Harbi, Hesham M.; Hegner, Ernst


    A combined study of single zircon U-Pb dating, Hf-O zircon isotopic analyses and whole-rock Nd isotopic compositions was carried out to infer the magma sources of Neoproterozoic post-collisional A-type granitoids in Saudi Arabia. U-Pb zircon dating of magmatic zircons of two samples from the Hadb adh Dayheen ring complex yielded ages of 625 ± 11 Ma for a hornblende-biotite granite sample, and 613 ± 4 Ma for a monzogranite sample. The granitic rocks show initial εNd values of + 4.1 to + 5.3 and εHf of + 4.5 to + 8.4 that are lower than those of a model depleted mantle (εHf ~+ 14 and εNd ~+ 6.5) and consistent with melting of subduction-related crustal protoliths that were formed during the Neoproterozoic assembly of the Arabian-Nubian Shield (ANS). Crustal-model ages (Hf-tNC) of 0.81 to 1.1 Ga are inconsistent with depleted-mantle Nd model ages of 0.71 to 0.81 Ga and indicate that the post-collisional Hadb adh Dayheen granites were derived mostly from juvenile crust formed in Neoproterozoic time. Single zircons data show a wide range in δ18O values from + 3.2‰ to + 6.4‰, possibly indicating crystallization of zircon from magma derived from magmatic rocks altered by meteoric water in a magma chamber-caldera system.

  11. Late Archaean mantle metasomatism below eastern Indian craton: Evidence from trace elements, REE geochemistry and Sr-Nd-O isotope systematics of ultramafic dykes

    Abhijit Roy; A Sarkar; S Jeyakumar; S K Aggrawal; M Ebihara; H Satoh


    Trace, rare earth elements (REE), Rb-Sr, Sm-Nd and O isotope studies have been carried out on ultramafic (harzburgite and lherzolite) dykes belonging to the newer dolerite dyke swarms of eastern Indian craton. The dyke swarms were earlier considered to be the youngest mafic magmatic activity in this region having ages not older than middle to late Proterozoic. The study indicates that the ultramafic members of these swarms are in fact of late Archaean age (Rb-Sr isochron age 2613 ± 177 Ma, Sri ∼0.702 ± 0.004) which attests that out of all the cratonic blocks of India, eastern Indian craton experienced earliest stabilization event. Primitive mantle normalized trace element plots of these dykes display enrichment in large ion lithophile elements (LILE), pronounced Ba, Nb and Sr depletions but very high concentrations of Cr and Ni. Chondrite normalised REE plots exhibit light REE (LREE) enrichment with nearly flat heavy REE (HREE; ( HREE)N ∼ 2-3 times chondrite, (Gd/Yb)N∼1). The Nd(t) values vary from +1.23 to −3.27 whereas 18O values vary from +3.16‰ to +5.29‰ (average +3.97‰ ± 0.75‰) which is lighter than the average mantle value. Isotopic, trace and REE data together indicate that during 2.6 Ga the nearly primitive mantle below the eastern Indian Craton was metasomatised by the fluid (±silicate melt) coming out from the subducting early crust resulting in LILE and LREE enriched, Nb depleted, variable Nd, low Sri(0.702) and low 18O bearing EMI type mantle. Magmatic blobs of this metasomatised mantle were subsequently emplaced in deeper levels of the granitic crust which possibly originated due to the same thermal pulse.

  12. Target rocks, impact glasses, and melt rocks from the Lonar crater, India: Highly siderophile element systematics and Sr-Nd-Os isotopic signatures

    Schulz, Toni; Luguet, Ambre; Wegner, Wencke; Acken, David; Koeberl, Christian


    The Lonar crater is a ~0.57-Myr-old impact structure located in the Deccan Traps of the Indian peninsula. It probably represents the best-preserved impact structure hosted in continental flood basalts, providing unique opportunities to study processes of impact cratering in basaltic targets. Here we present highly siderophile element (HSE) abundances and Sr-Nd and Os isotope data for target basalts and impactites (impact glasses and impact melt rocks) from the Lonar area. These tools may enable us to better constrain the interplay of a variety of impact-related processes such as mixing, volatilization, and contamination. Strontium and Nd isotopic compositions of impactites confirm and extend earlier suggestions about the incorporation of ancient basement rocks in Lonar impactites. In the Re-Os isochron plot, target basalts exhibit considerable scatter around a 65.6 Myr Re-Os reference isochron, most likely reflecting weathering and/or magma replenishment processes. Most impactites plot at distinctly lower 187Re/188Os and 187Os/188Os ratios compared to the target rocks and exhibit up to two orders of magnitude higher abundances of Ir, Os, and Ru. Moreover, the impactites show near-chondritic interelement ratios of HSE. We interpret our results in terms of an addition of up to 0.03% of a chondritc component to most impact glasses and impact melt rocks. The magnitude of the admixture is significantly lower than the earlier reported 12-20 wt% of extraterrestrial component for Lonar impact spherules, reflecting the typical difference in the distribution of projectile component between impact glass spherules and bulk impactites.

  13. Sm-Nd and Rb-Sr Isotopic Systematics of a Heavily Shocked Martian Meteorite Tissint and Petrogenesis of Depleted Shergottites

    Shih, C.-Y.; Nyquist, L. E.; Park, J.; Agee, Carl B.


    Tissint is a very fresh Martian meteorite that fell near the town of Tissint in Morocco on July 18, 2011. It contains abundant olivine megacrysts (23%) in a fine-grained matrix of pyroxene (55%), maskelynitized plagioclase (15%), opaques (4%) and melt pockets (3%) and is petrographically similar to lithologies A and C of picritic shergottite EETA 79001 [1,2]. The presence of 2 types of shock-induced glasses and all 7 high-pressure mineral phases that were ever found in melt pockets of Martian meteorites suggests it underwent an intensive shock metamorphism of 25 GPa and 2000 C localized in melt pockets [2]. Mineral textures suggest that olivines, pyroxenes and plagioclases probably did not experience such hightemperature. Earlier determinations of its age yielded 596+/-23 Ma [3] and 616+/-67 Ma [4], respectively, for the Sm-Nd system and 583+/-86 Ma for the Lu-Hf system [4], in agreement with the 575+/-18 Ma age of the oldest olivine-phyric depleted shergottite Dho 019 [5]. However, the exposure ages of Tissint (1 Ma [1, 6, 7]) and Dho 019 (20 Ma [8]) are very different requiring two separate ejection events. These previously determined Sm-Nd and Lu-Hf ages are older than the Ar-Ar maskelynite plateau age of 524+/-15 Ma [9], reversing the pattern usually observed for Martian meteorites. In order to clarify these age issues and place models for Tissint's petrogenesis on a firm basis, we present new Rb-Sr and Sm- Nd isotopic results for Tissint, and discuss (a) the shock effects on them and the Ar-Ar chronometer, (b) correlation of the determined ages with those of other depleted shergottites, and (c) the petrogenesis of depleted shergottites. Since the meteorite is a recent fall, terrestrial contamination is expected to be minimal, but, the strong shock metamorphism might be expected to compromise the equilibrium of the isotopic systems.

  14. Screening of microbial radiation-inducible promoter and study of its expression; Development of basic technique of radiogenic therapy

    Lim, Sangyong; Kim Dongho; Yang, Jaeseung


    In the search for new therapeutic modalities for cancer, gene therapy has attracted enormous interest over the last few years. Recently, the use of bacteria as a tumor specific protein transfer system has attracted interest. Attenuated Salmonella has been shown to provide selective colonization in tumors. This strategy to apply gene therapy for cancer has been defined as 'Radiogenic Therapy'. In this research, firstly, we screened a radiation inducible promoter of Salmonella responding to clinically relevant low dose of 10 Gy using microarray analysis. Of all genes showing a expression ratio of at least 2-fold changes relative to wild type, 168 genes were induced. To confirm the findings of the microarray by an alternative method, we investigated the transcriptional changes of radio-inducible genes using real time PCR analysis. To verify the ability of screened genes (fadB, narK, cyoA, STM1011, STM2617, and STM2632) to produce a downstream protein by irradiation, the reporter plasmids were constructed. Finally, we found that the promoter of fadB, cyoA, and STM2617 can be activated by irradiation within cancer cells. These results suggest that these genes may be the most probable candidate used in radiogenic therapy.

  15. Mineral dissolution in the Cape Cod aquifer, Massachusetts, USA: I . Reaction stoichiometry and impact of accessory feldspar and glauconite on strontium isotopes, solute concentrations, and REY distribution

    Bau, Michael; Alexander, Brian; Chesley, John T.; Dulski, Peter; Brantley, Susan L.


    To compare relative reaction rates of mineral dissolution in a mineralogically simple groundwater aquifer, we studied the controls on solute concentrations, Sr isotopes, and rare earth element and yttrium (REY) systematics in the Cape Cod aquifer. This aquifer comprises mostly carbonate-free Pleistocene sediments that are about 90% quartz with minor K-feldspar, plagioclase, glauconite, and Fe-oxides. Silica concentrations and pH in the groundwater increase systematically with increasing depth, while Sr isotopic ratios decrease. No clear relationship between 87Sr/ 86Sr and Sr concentration is observed. At all depths, the 87Sr/ 86Sr ratio of the groundwater is considerably lower than the Sr isotopic ratio of the bulk sediment or its K-feldspar component, but similar to that of a plagioclase-rich accessory separate obtained from the sediment. The Si- 87Sr/ 86Sr-depth relationships are consistent with dissolution of accessory plagioclase. In addition, solutes such as Sr, Ca, and particularly K show concentration spikes superimposed on their respective general trends. The K-Sr- 87Sr/ 86Sr systematics suggests that accessory glauconite is another major solute source to Cape Cod groundwater. Although the authigenic glauconite in the Cape Cod sediment is rich in Rb, it is low in in-grown radiogenic 87Sr because of its young Pleistocene age. The low 87Sr/ 86Sr ratios are consistent with equilibration of glauconite with seawater. The impact of glauconite is inferred to vary due to its variable abundance in the sediments. In the Cape Cod groundwater, the variation of REY concentrations with sampling depth resembles that of K and Rb, but differs from that of Ca and Sr. Shale-normalized REY patterns are light REY depleted, show negative Ce anomalies and super-chondritic Y/Ho ratios, but no Eu anomalies. REY input from feldspar, therefore, is insignificant compared to input from a K-Rb-bearing phase, inferred to be glauconite. These results emphasize that interpretation of

  16. SHRIMP-RG U-Pb isotopic systematics of zircon from the Angel Lake orthogneiss, East Humboldt Range, Nevada: Is this really archean crust?

    Premo, Wayne R.; Castineiras, Pedro; Wooden, Joseph L.


    New SHRIMP-RG (sensitive high-resolution ion microprobe-reverse geometry) data confirm the existence of Archean components within zircon grains of a sample from the orthogneiss of Angel Lake, Nevada, United States, previously interpreted as a nappe of Archean crust. However, the combined evidence strongly suggests that this orthogneiss is a highly deformed, Late Cretaceous monzogranite derived from melting of a sedimentary source dominated by Archean detritus. Zircon grains from the same sample used previously for isotope dilution-thermal ionization mass spectrometry (ID-TIMS) isotopic work were analyzed using the SHRIMP-RG to better define the age and origin of the orthogneiss. Prior to analysis, imaging revealed a morphological variability and intragrain, polyphase nature of the zircon population. The SHRIMP-RG yielded 207Pb/206Pb ages between ca. 2430 and 2580 Ma (a best-fit mean 207Pb/206Pb age of 2531 ± 19 Ma; 95% confidence) from mostly rounded to subrounded zircons and zircon components (cores). In addition, several analyses from rounded to subrounded cores or grains yielded discordant 207Pb/206Pb ages between ca. 1460 and ca. 2170 Ma, consistent with known regional magmatic events. All cores of Proterozoic to latest Archean age were encased within clear, typically low Th/U (206Pb/238U ages between 72 and 91 Ma, consistent with magmatic ages from Lamoille Canyon to the south. An age of ca. 90 Ma is suggested, the younger 206Pb/238U ages resulting from Pb loss. The Cretaceous and Precambrian zircon components also have distinct trace element characteristics, indicating that these age groups are not related to the same igneous source. These results support recent geophysical interpretations and negate the contention that the Archean-Proterozoic boundary extends into the central Great Basin area. They further suggest that the world-class gold deposits along the Carlin Trend are not underlain by Archean cratonal crust, but rather by the Proterozoic Mojave

  17. Subduction erosion of forearc mantle wedge implicated in the genesis of the South Sandwich Island (SSI) arc: Evidence from boron isotope systematics

    Tonarini, Sonia; Leeman, William P.; Leat, Phil T.


    The South Sandwich volcanic arc is sited on a young oceanic crust, erupts low-K tholeiitic rocks, is characterized by unexotic pelagic and volcanogenic sediments on the down-going slab, and simple tectonic setting, and is ideal for assessing element transport through subduction zones. As a means of quantifying processes attending transfer of subduction-related fluids from the slab to the mantle wedge, boron concentrations and isotopic compositions were determined for representative lavas from along the arc. The samples show variable fluid-mobile/fluid-immobile element ratios and high enrichments of B/Nb (2.7 to 55) and B/Zr (0.12 to 0.57), similar to those observed in western Pacific arcs. δ11B values are among the highest so far reported for mantle-derived lavas; these are highest in the central part of the arc (+ 15 to + 18‰) and decrease toward the southern and northern ends (+ 12 to + 14‰). δ11B is roughly positively correlated with B concentrations and with 87Sr/86Sr ratios, but poorly coupled with other fluid-mobile elements such as Rb, Ba, Sr and U. Peridotites dredged from the forearc trench also have high δ11B (ca. + 10‰) and elevated B contents (38-140 ppm). Incoming pelagic sediments sampled at ODP Site 701 display a wide range in δ11B (+ 5 to - 13‰; average = - 4.1‰), with negative values most common. The unusually high δ11B values inferred for the South Sandwich mantle wedge cannot easily be attributed to direct incorporation of subducting slab materials or fluids derived directly therefrom. Rather, the heavy B isotopic signature of the magma sources is more plausibly explained by ingress of fluids derived from subduction erosion of altered frontal arc mantle wedge materials similar to those in the Marianas forearc. We propose that multi-stage recycling of high-δ11B and high-B serpentinite (possibly embellished by arc crust and volcaniclastic sediments) can produce extremely 11B-rich fluids at slab depths beneath the volcanic arc

  18. Holocene Provenance Identification and Climate Control of Indus Basin By Using Radiogenic Techniques and Clay Mineralogy



    Full Text Available Two commonly used isotopic methods (Zircon U-Pb dating and K-feldspar Pb dating were employed for the Holocene provenance identification within the Indus basin. Zircon grains from the upper Indus are generally younger than 200 Ma in contrast with the eastern tributaries, which show varying inputs from Greater and Lesser Himalayan sources. The Sutlej river is very rich in Lesser Himalayan-sourced sediments, while the Chenab is mostly eroded from the Greater Himalaya. Grains younger than 200 Ma in the sands of the Thar desert indicate preferential aeolian transport from the Indus lower reaches. K-feldspar Pb dating of silt and sand-sized grains from the modern Sutlej and Chenab rivers show a clear Himalayan provenance, contrasting with grains from the Indus Suture Zone, but are overlapping with Karakoram compositions. The desert dunes commonly show 207Pb/204Pb and 206Pb/204Pb values that are much higher than those seen in the rivers, most consistent with erosion from Nanga Parbat. This implies at least some origin from the trunk Indus, probably reworked by summer monsoon winds from the SW, a hypothesis supported by U-Pb zircon dating. Further, data collected from Holocene and Pleistocene buried sands on the western edge of the Thar desert were sourced from Himalayan rivers before and at 6–8 ka, but after that time the proportion of high isotopic ratio grains rose, indicating increased contribution from the Thar Desert dunes prior to ~4.5 ka when flow ceased entirely. Clay mineral assemblages are dominated by smectite and illite, with minor chlorite and kaolinite. Deltaic sediments integrate clay minerals across the basin with increased smectite input between 13 and 7.5 ka, indicating stronger chemical weathering when the summer monsoon intensified and correlating with similar trends in peninsular India.

  19. Helium and argon isotopes of the Tertiary basic igneous rocks from Shandong Peninsula and implications for the magma origin


    Helium (He) and Argon (Ar) isotopic compositions of the Tertiary basic igneous rocks were determined by the high temperature melting extraction method. The selected samples for the studies included al-kaline basalts and diabases from the Jiyang basin,and the surrounding Shanwang and Qixia outcrops in the Shandong Peninsula,eastern China. The results show that the Paleogene basalts and diabases from the Jiyang basin yielded a wide range of P4 PHe abundance of (73.70-804.16)×10 P-8 Pcm P3 P STP·g P-1 P,with P3 PHe/ P4 PHe ratios of 0.374-2.959 Ra,which was lower than the MORB but evidently higher than the con-tinental crust value. The Neogene alkaline basalts from the Jiyang basin,Shanwang and Qixia outcrops have variable P4 PHe abundances ((42.34-286.72)×10-8 Pcm P3 P STP·g-1 P),and "continental crust-like" P3 PHe/ P4 PHe ratios (0.013-0.074 Ra). All of them contain atmospheric-like P40 PAr/ P36 PAr ratio (395.4-1312.7),reflecting the mantle sources with air components. Their low P3 PHe/ P4 PHe ratios are interpreted as the enrichment of the radiogenic P4 PHe mainly inherited from the mantle. He and Ar systematics show the mixing of MORB-type,air and a P4 PHe enriched member in the mantle source,suggesting that these igneous rocks originated from the depleted asthenospheric mantle mixed with an EMI component. Therefore,the present He and Ar isotopes do not support the viewpoints that the Cenozoic igneous rocks of Eastern North China were the products of mantle plume(s) activities.

  20. Helium and argon isotopes of the Tertiary basic igneous rocks from Shandong Peninsula and implications for the magma origin

    TANG HuaYun; ZHENG JianPing; CHEN HongHan; YE XianRen


    Helium (He) and Argon (Ar) isotopic compositions of the Tertiary basic igneous rocks were determined by the high temperature melting extraction method. The selected samples for the studies included alkaline basalts and diabases from the Jiyang basin, and the surrounding Shanwang and Qixia outcrops in the Shandong Peninsula, eastern China. The results show that the Paleogene basalts and diabases from the Jiyang basin yielded a wide range of 4 He abundance of (73.70-804.16)×10-8 cm3 STP·Gp-1, with 3He/4He ratios of 0.374-2.959 Ra, which was lower than the MORB but evidently higher than the continental crust value. The Neogene alkaline basalts from the Jiyang basin, Shanwang and Qixia outcrops have variable 4He abundances ((42.34-286.72)×10-8 cm3 STP·g-1), and "continental crust-like" 3He/4He ratios (0.013-0.074 Ra). All of them contain atmospheric-like 40Ar/36Ar ratio (395.4-1312.7), reflecting the mantle sources with air components. Their low 3He/4He ratios are interpreted as the enrichment of the radiogenic 4He mainly inherited from the mantle. He and Ar systematics show the mixing of MORB-type, air and a 4He enriched member in the mantle source, suggesting that these igneous rocks originated from the depleted asthenospheric mantle mixed with an EMI component. Therefore, the present He and Ar isotopes do not support the viewpoints that the Cenozoic igneous rocks of Eastern North China were the products of mantle plume(s) activities.

  1. Isotopic Studies of the Guerrero Composite Terrane, West-Central Mexico: Implications for Provenance of Crustal Rocks and Ore Metals

    Potra, A.; Macfarlane, A. W.; Salters, V. J.; Sachi-Kocher, A.


    New Pb, Sr, and Nd isotope analyses of various crustal units and ores from the Guerrero terrane are presented in order to gain insight into their provenance. Mesozoic basement rocks from the Arteaga Complex and Tejupilco metamorphic suite contain radiogenic Pb relative to bulk earth models (206Pb/204Pb between 18.701 and 19.256, 207Pb/204Pb between 15.623 and 15.693, and 208Pb/204Pb between 38.694 and 39.216), plotting to the right of the average Pb crust evolution curve of Stacey and Kramers (1975). The isotopic compositions of Pb in these rocks are substantially more radiogenic than published data on high-grade metamorphic rocks from the Grenvillian-age Oaxaca terrane, but are similar to Paleozoic basement rocks of the Mixteca terrane. Sr and Nd isotope data suggest that the basement rocks of the Guerrero terrane partly originated from ocean-floor rocks which were overlain by sediments derived from a cratonic terrane, possibly represented by the metamorphic complexes of the Oaxaca or Mixteca terranes. Lead isotope ratios of Cretaceous sedimentary rocks of the Zihuatanejo and Huetamo Sequences define two different clusters, with the Zihuatanejo Sequence units shifted to more radiogenic values (206Pb/204 between 18.763 and 19.437, 207Pb/204Pb between 15.580 and 15.643, and 208Pb/204Pb between 38.510 and 38.892). Samples from the Huetamo Sequence are less radiogenic than the metamorphic basement, with Pb isotope ratios between 18.630 and 18.998 for 206Pb/204, 15.563 and 15.641 for 207Pb/204Pb, and 38.369 and 38.610 for 208Pb/204Pb. They plot close to the radiogenic end of the MORB field, suggesting a possible mixing line between the basement rocks and the MORB component. Lead isotope ratios of Tertiary intrusive rocks from La Verde, El Malacate, and La Esmeralda resemble the orogene reservoir in the plumbotectonics model of Zartman and Doe (1981). Plutonic rocks from La Verde show the most radiogenic Pb compositions, suggesting a significant influence of old

  2. Systematic sulfur stable isotope and fluid inclusion studies on veinlet groups in the Sarcheshmeh porphyry copper deposit: based on new data

    Mohammad Maanijou


    Full Text Available Mineralization occurred by intrusion of granodioritic stock of middle Miocene in volcano–sedimenrary rocks in Sarcheshmeh of early Tertiary age. This research is based on samples of new drilled boreholes and benches of 2500m elevation. Based on mineralogy and crosscutting relationships, at least four groups of veinlets pertaining to four stages of mineralization were recognized. Sulfur isotope studies in the Sarcheshmeh porphyry copper deposit were conducted on pyrite, chalcopyrite, molybdenite and anhydrites of four groups of veinlets. The δ34S values in the sulfides and sulfates range from -2.2 to 1.27‰ and from 10.2 to 14.5 ‰, respectively. The average δ34S value in the sulfides is 1‰ and that for the sulfates is about 13‰. Considering these results, it can be concluded that the sulfides made up of a fluid that its sulfur has a magmatic origin. Also, fluid inclusions of different veinlet groups were studied, showing high temperature, high salinity and the occurrence of boiling in the mineralizing fluids. Moreover, these studies indicate presence of three types of fluids including magmatic, meteoritic and mixture of these two fluids in alteration and mineralizion processes.

  3. Leatherback Isotopes

    National Oceanic and Atmospheric Administration, Department of Commerce — SWFSC is currently working on a project identifying global marine isotopes using leatherback turtles (Dermochelys coriacea) as the indicator species. We currently...

  4. Rare gas isotopes and parent trace elements in ultrabasic-alkaline-carbonatite complexes, Kola Peninsula: identification of lower mantle plume component

    Tolstikhin, I. N.; Kamensky, I. L.; Marty, B.; Nivin, V. A.; Vetrin, V. R.; Balaganskaya, E. G.; Ikorsky, S. V.; Gannibal, M. A.; Weiss, D.; Verhulst, A.; Demaiffe, D.


    ones, allowing to infer a source 40Ar/36Ar ratio of about 4000 for the mantle end-member, which is 10 times lower than that of the MORB source end-member. In (3He/22Ne)PRIM versus (4He/21Ne)RAD plot the Kola samples are within array established for plume and MORB samples; almost constant production ratio of (4He/21Ne)RAD ≅ 2 × 107 is translated via this array into (3He/22Ne)PRIM ∼ 10. The latter value approaches the solar ratio implying the non-fractionated solar-like rare gas pattern in a plume source. The Kola UACC show systematic variations in the respective contributions of in situ-produced radiogenic isotopes and mantle-derived isotopes. Since these complexes were essentially plutonic, we propose that the depth of emplacement exerted a primary control on the retention of both trapped and radiogenic species, which is consistent with geological observations. The available data allow to infer the following sequence of processes for the emplacement and evolution of Kola Devonian UACC: 1) Ascent of the plume from the lower mantle to the subcontinental lithosphere; the plume triggered mantle metasomatism not later than ∼700 to 400 Ma ago. 2) Metasomatism of the lithosphere (beneath the central part of the Kola Peninsula), including enrichment in volatile (e.g., He, Ne) and in incompatible (e.g., U, Th) elements. 3) Multistage intrusions of parental melts, their degassing, and crystallisation differentiation ∼370 Ma ago. 4) Postcrystallisation migration of fluids, including loss of radiogenic and of trapped helium. Based on model compositions of the principle terrestrial reservoirs we estimate the contributions (by mass) of the plume material, the upper mantle material, and the atmosphere (air-saturated groundwater), into the source of parent melt at ∼2%, 97.95%, and ∼0.05%, respectively.

  5. Genesis of Sr Isotopes in Groundwater of Hebei Plain


    To analyze the genesis of Sr isotopes in groundwater of Hebei plain, time-accumulative effect of 87Sr/86Sr ratio was studied. It is shown that 87Sr/86Sr ratio increases with the increasing age and depth of groundwater and has a positive correlation to 4Heexc and a negative correlation to δ18O and δD.The groundwater is divided into three groups to discuss the relation between 87Sr/86Sr ratio and Sr2+ content: ① moderate Sr2+ content and higher 87Sr/86Sr ratio (water Ⅰ); ② lower Sr2+ content and higher 87Sr/86Sr ratio (water Ⅱ); and ③ higher Sr2+ content and lower 87Sr/86Sr ratio (water Ⅲ), that is hot water. On the basis of integrated analysis, it was considered that ① the radiogenic Sr in the Quaternary groundwater (Q4-Q1) originates from weathering of silicate rich in Na and Rb, mainly from plagioclase; ② the radiogenic Sr of hot water in Huanghua port is attributed to carbonate dissolution, with lower 87Sr/86Sr ratio and higher Sr/Na ratio; ③ the recharge area is laterally recharged by the groundwater flowing through igneous and metamorphic rocks, with moderate 87Sr/86Sr ratio. However, the formation mechanism of Sr isotopes in Tertiary groundwater needs further studies.

  6. Isotopic chirality

    Floss, H.G. [Univ. of Washington, Seattle, WA (United States)


    This paper deals with compounds that are chiral-at least in part, due to isotope substitution-and their use in tracing the steric course of enzyme reaction in vitro and in vivo. There are other applications of isotopically chiral compounds (for example, in analyzing the steric course of nonenzymatic reactions and in probing the conformation of biomolecules) that are important but they will not be discussed in this context.

  7. Isotopic Paleoclimatology

    Bowen, R.

    Paleotemperature scales were calculated by H. C. Urey and others in the 1950s to assess past temperatures, and later work using the stable isotopes of oxygen, hydrogen, and carbon employed standards such as Peedee belemnite (PDB) and Standard Mean Ocean Water (SMOW). Subsequently, subjects as diverse as ice volume and paleotemperatures, oceanic ice and sediment cores, Pleistocene/Holocene climatic changes, and isotope chronostratigraphy extending back to the Precambrian were investigated.

  8. DEGRO practical guidelines for radiotherapy of non-malignant disorders. Part I: physical principles, radiobiological mechanisms, and radiogenic risk

    Reichl, Berthold [Hospital Weiden, Department of Radiotherapy and Radiation Oncology, Weiden (Germany); Block, Andreas [Hospital Dortmund, Institute for Medical Radiation Physics and Radiation Protection, Dortmund (Germany); Schaefer, Ulrich [Lippe Hospital, Dept. of Radiotherapy, Lemgo (Germany); Bert, Christoph; Mueller, Reinhold [University Hospitals Erlangen, Dept. of Radiation Oncology, Erlangen (Germany); Jung, Horst [University Hospital Hamburg-Eppendorf, Dept. of Radiotherapy and Radiation Oncology, Hamburg (Germany); Roedel, Franz [University Hospital Goethe-University, Dept. of Radiotherapy and Oncology, Frankfurt am Main (Germany); Collaboration: the German Cooperative Group on Radiotherapy for Benign Diseases (GCG-BD)


    Synopsis of the introductory paragraph of the DEGRO consensus S2e-guideline recommendations for the radiotherapy of benign disorders, including physical principles, radiobiological mechanisms, and radiogenic risk. This work is based on the S2e-guideline recommendations published November 14, 2013. The basic principles of radiation physics and treatment delivery, evaluation of putative underlying radiobiological mechanisms, and the assessment of genetic and cancer risk following low-dose irradiation will be presented. Radiation therapy of benign diseases is performed according to similar physical principles as those governing treatment of malignant diseases in radiation oncology, using the same techniques and workflows. These methods comprise usage of orthovoltage X-ray units, gamma irradiation facilities, linear accelerators (LINACs), and brachytherapy. Experimental in vitro and in vivo models recently confirmed the clinically observed anti-inflammatory effect of low-dose X-irradiation, and implicated a multitude of radiobiological mechanisms. These include modulation of different immunological pathways, as well as the activities of endothelial cells, mono- and polymorphonuclear leukocytes, and macrophages. The use of effective dose for radiogenic risk assessment and the corresponding tumor incidence rate of 5.5 %/Sv are currently controversially discussed. Some authors argue that the risk of radiation-induced cancers should be estimated on the basis of epidemiological data. However, such data are rarely available at present and associated with high variability. Current radiobiological studies clearly demonstrate a therapeutic effectiveness of radiation therapy used to treat benign diseases and implicate various molecular mechanisms. Radiogenic risks should be taken into account when applying radiation treatment for benign diseases. (orig.) [German] Zusammenfassung des einfuehrenden Kapitels der DEGRO-S2e-Leitlinie zur Strahlentherapie gutartiger Erkrankungen

  9. Thermodynamic stability of radiogenic Ba in CsAlSi2O6 pollucite

    Jaffe, John; van Ginhoven, Renée; Jiang, Weilin


    Pollucite, a zeolite-like nanoporous aluminosilicate structure with nominal composition CsAlSi2O6, has been suggested as a nuclear waste storage form for fission-product radioactive isotopes of cesium, especially 137Cs. One factor affecting the long-term stability of this waste form is the valence change associated with the beta decay that converts Cs into barium. We have used first-principles density functional total energy calculations to evaluate the thermodynamic stability of pollucite with Ba replacing Cs at regular lattice sites with respect to the precipitation of Ba, Cs or their oxides. We included small clusters of substitutional BaCs as well as localized complexes of BaCs with compensating electron donor defects, specifically Cs vacancies and interstitial oxygen. We conclude that Cs-Ba pollucite is thermodynamically stable against precipitation of Cs or its oxide, but that partial precipitation of Ba or BaO may be thermodynamically favored under some conditions. Even this change may be kinetically limited, however. Fuel Cycle Research and Development, U.S. Department of Energy Waste Form Campaign

  10. Mixing the mantle marble-cake: timescale constraints from Os isotopes

    Parman, S.; Pearson, G.; Nowell, G.; van Hunen, J.


    In their seminal paper, Allegre and Turcotte (1986) presented a model in which the upper mantle is a mixture of depleted, harzburgitic mantle and subducted basalt that has been mechanically mixed together, the mantle marble-cake. Since their publication, most studies of mantle heterogeneity have focused on the enriched components, which are equated with subducted basalt and/or sediments, and successfully explain OIB Sr-Nd-Pb isotopic systematics. In this talk, we will focus on a different part of the marble-cake, depleted (harzburgitic) heterogeneities. Though abundant in abyssal peridotites and ophiolites, these have been difficult to study geochemically because they have very low concentrations of typical trace elements and radiogenic isotopes, and are overprinted by any mixing with enriched mantle or melts. However, Os is compatible during mantle melting, is enriched in depleted mantle and thus is robust with respect to mixing with enriched components or metasomatism. Somewhat surprisingly, Os isotope studies of the convecting mantle show clear evidence for depleted heterogeities up to 2 billion years old, but the relative paucity of data (less than 100 analyses), makes it difficult to extract meaningful mixing information. Rapid analysis of osmiridium grains by laser-ablation inductively coupled multi-collector plasma mass spectrometry now allows large Os datasets to be acquired (100s of datapoints), which are suitable for statistical analyses (Meibom, 2002). Here we present new and published laser-ablation analyses of osmiridiums from a global collection. The data generally show an exponential decrease in heterogeneities with age, such that over 90% of heterogeneities are destroyed within 2 billion years, though rare heterogeneities as old as 2.7 Ga survive. The exponential decrease in survivorship is generally consistent with the mechanical mixing model of Allegre & Turcotte (1986). Subsequent 2-dimensional mixing models suggest that high-viscosity blobs can

  11. Osmium isotope and highly siderophile element systematics of lunar impact melt breccias: Implications for the late accretion history of the Moon and Earth

    Puchtel, Igor S.; Walker, Richard J.; James, Odette B.; Kring, David A.


    To characterize the compositions of materials accreted to the Earth-Moon system between about 4.5 and 3.8 Ga, we have determined Os isotopic compositions and some highly siderophile element (HSE: Re, Os, Ir, Ru, Pt, and Pd) abundances in 48 subsamples of six lunar breccias. These are: Apollo 17 poikilitic melt breccias 72395 and 76215; Apollo 17 aphanitic melt breccias 73215 and 73255; Apollo 14 polymict breccia 14321; and lunar meteorite NWA482, a crystallized impact melt. Plots of Ir versus other HSE define excellent linear correlations, indicating that all data sets likely represent dominantly two-component mixtures of a low-HSE target, presumably endogenous component, and a high-HSE, presumably exogenous component. Linear regressions of these trends yield intercepts that are statistically indistinguishable from zero for all HSE, except for Ru and Pd in two samples. The slopes of the linear regressions are insensitive to target rock contributions of Ru and Pd of the magnitude observed; thus, the trendline slopes approximate the elemental ratios present in the impactor components contributed to these rocks. The 187Os/188Os and regression-derived elemental ratios for the Apollo 17 aphanitic melt breccias and the lunar meteorite indicate that the impactor components in these samples have close affinities to chondritic meteorites. The HSE in the Apollo 17 aphanitic melt breccias, however, might partially or entirely reflect the HSE characteristics of HSE-rich granulitic breccia clasts that were incorporated in the impact melt at the time of its creation. In this case, the HSE characteristics of these rocks may reflect those of an impactor that predated the impact event that led to the creation of the melt breccias. The impactor components in the Apollo 17 poikilitic melt breccias and in the Apollo 14 breccia have higher 187Os/188Os, Pt/Ir, and Ru/Ir and lower Os/Ir than most chondrites. These compositions suggest that the impactors they represent were chemically

  12. Lead isotope and trace element composition of urban soils in Mongolia

    Tserenpil, Sh.; Sapkota, A.; Liu, C.-Q.; Peng, J.-H.; Liu, B.; Segebade, P. Chr.


    Lead (Pb) pollution in and around Ulaanbaatar is of national concern, given that the Mongolian capital is home to nearly half of the country's entire population. By comparison, Mongolian countryside is a pristine environment because of its sparse population and low industrial activity. The concentration of Pb in urban soils (average of 39.1 mg kg-1) was twice the values found (average 18.6 mg kg-1) in background territories (i.e., Mongolian rural sites). Furthermore, Pb contamination was examined by using Pb stable isotopic composition, and covariance of Pb isotopic ratios showed two groups between rural and urban soils as pristine and disturbed sites. The 206Pb/207Pb ratio, the most prominent fingerprint for Pb pollution, was 1.163-1.185 for the urban whereas values for rural soils (1.186-1.207) were analogue to the regional Pb isotopic signatures. Local coal sources and their combustion products, one of the potential Pb pollution sources in Ulaanbaatar, have significant radiogenic properties in terms of Pb isotopic composition and revealed an average of 1.25 for 206Pb/207Pb and 19.551 for 206Pb/204Pb ratios. Thus, contributions from coal firing activity to Pb pollution lower than it was assumed, and smaller range of these values measured in urban soils may be attributed to the mixing of less radiogenic Pb as a constituent of the leaded gasolines.

  13. Diamond growth history from in situ measurement of Pb and S isotopic compositions of sulfide inclusions

    Rudnick, Roberta L.; Eldridge, C. Stewart; Bulanova, Galina P.


    In a continuing effort to understand crust-mantle dynamics, we have determined the S and Pb isotopic compositions of mantle sulfides encapsulated within diamonds from under the Siberian craton and compared these results to those of previously investigated African counterparts. Because diamond inclusions are isolated from exchange with surrounding mantle, they may preserve the history of diamond growth and act as direct tracers of the origins of mantle materials. Study of these inclusions may thus offer the best chance of recognizing global-scale interaction between Earth's crust and mantle. Although δ34S values of the Siberian sulfides do not deviate significantly from the mantle value of 0‰ ± 3‰, Pb isotopic compositions are highly variable. Pb isotopic compositions of sulfides from peridotitic suite diamonds generally plot near the terrestrial Pb growth curve, with model ages ranging between 0 and 2 Ga, whereas sulfides from eclogitic suite diamonds have radiogenic compositions, plotting beyond the growth curve. These results, which are similar to those for sulfides in African diamonds, suggest that the sulfides from eclogitic suite diamonds were derived from a source with an unusually high U/Pb ratio and may indicate a common process (such as subduction of crystal materials into the mantle) operating beneath Africa and Siberia. The absence of extremely radiogenic Pb in sulfides from eclogite xenoliths suggests that the radiogenic material from which eclogitic suite diamonds grew was a transient feature of the mantle, associated with diamond growth. The ultimate origin of this high U/Pb signature, however, remains enigmatic. Large variations in Pb isotopic composition of sulfides from different zones in a single peridotitic suite diamond document (1) crystallization of the diamond's core near 2.0 Ga, (2) growth of its outer zone in an environment with a high U/Pb ratio similar to the growth environment of eclogitic suite diamonds, and (3) growth of the

  14. Dissolved Neodymium Isotopes and Concentrations in the South Pacific

    Basak, C.; Pahnke, K.


    The isotopic composition of dissolved Neodymium (expressed as ɛNd) in seawater is becoming increasingly established as a tracer for present and past water mass structure and flow paths. The South Pacific represents the largest sector of the Southern Ocean and harbors major areas of bottom and intermediate water mass formation and is therefore a key area for understanding present and past deep ocean circulation. While more dissolved Nd data are becoming available from different ocean basins, the South Pacific is still understudied with respect to the distribution of Nd isotopes and concentrations. In this study we have analyzed dissolved Nd isotopes and concentrations from 11 water column profiles across the South Pacific between 46°S and 69°S that sample all water masses. Our data show that the bottom water in the vicinity of the Ross Sea (Ross Sea Bottom water, RSBW) is represented by an ɛNd value of ~ -7, while the overlying Circumpolar Deep Water (CDW) carries a signature of ɛNd = -8 to -9. The characteristic Nd isotopic signal of RSBW can be tracked along its flow path into the southeast Pacific where it progressively looses its signal through interaction with ambient CDW. The easternmost stations, closer to South America, exhibit an excursion towards radiogenic ɛNd at ≤2000 m water depth. This change towards more positive ɛNd coincides with low oxygen and high phosphate concentrations representing Pacific Deep Water (PDW) and possibly indicates water mass mixing of CDW with more radiogenic PDW. While the Nd isotopic composition shows apparent variations between stations and different water masses, the concentration profiles show a rather uniform and gradual increase with depth, a pattern typical for open ocean settings. Spatial and vertical contrasts in Nd isotopic values throughout the South Pacific indicate that Nd isotopes can be used as a water mass tracer in this region. It is reasonable to infer that local lithology in the Ross Sea influenced

  15. Metallogeny and lead isotope data from the Oslo Paleorift

    Bjørlykke, A.; Ihlen, P. M.; Olerud, S.


    The Permian Oslo Paleorift, situated at the southwestern margin of the Baltic shield, includes the Oslo Region and its southward extension under Skagerak. The exposed part of the paleorift comprises two half-grabens (Vestfold and Akershus graben segments) filled with Permian sediments, volcanics and intrusive rocks as well as Cambrc-Silurian sedimentary rocks. The evolution of the Oslo Rift can be divided into a rifting stage, a caldera stage and a batholith stage. The rifting stage is characterized by weak mineralization of native copper in basalts. The caldera stage includes Fe-Ti cumulates in subvolcanic layered alkali gabbros, Nb-REE disseminations in aphyric trachytes, and epigenetic Mo-mineralizations. The batholith stage includes porphyry and intraplutonic vein deposits of Mo and contact metasomatic deposits of Fe, W, Mo, Be, Zn, Pb, Cu, Bi, As and F. Along the rift margin in Precambrian gneisses and amphibolites there are vein deposits of Fe-oxides, base metals and native silver. The relationship between the rift margin deposits and the evolution of the rift is still unclear, but many deposits are spatially related to Permian dolerite dykes. Lead isotope data from hydrothermal deposits in the Oslo Rift fall into two main groups. The first group comprises the rift margin deposits. They are very radiogenic and reflect an upper crustal source for the metals. The source of the silver deposits generally has a lower μ-value and a higher w- value than the base metal deposits. The rift margin deposits are therefore not a product of metal zonation from a single hydrothermal solution. The second group comprises deposits associated with granitic intrusions in the Oslo Graben and reflects a lower to intermediate crustal source for the metals. Deposits in the Vestfold graben segment are generally more radiogenic than deposits in the Akershus graben segment and this difference may be explained by a small contribution of highly radiogenic lead from underlying Precambrian

  16. Hafnium at subduction zones: isotopic budget of input and output fluxes; L'hafnium dans les zones de subduction: bilan isotopique des flux entrant et sortant

    Marini, J.Ch


    Subduction zones are the primary regions of mass exchanges between continental crust and mantle of Earth through sediment subduction toward the earth's mantle and by supply of mantellic magmas to volcanic arcs. We analyze these mass exchanges using Hafnium and Neodymium isotopes. At the Izu-Mariana subduction zone, subducting sediments have Hf and Nd isotopes equivalent to Pacific seawater. Altered oceanic crust has Hf and Nd isotopic compositions equivalent to the isotopic budget of unaltered Pacific oceanic crust. At Luzon and Java subduction zones, arc lavas present Hf isotopic ratios highly radiogenic in comparison to their Nd isotopic ratios. Such compositions of the Luzon and Java arc lavas are controlled by a contamination of their sources by the subducted oceanic sediments. (author)

  17. Sr-Nd-Pb-C-O isotope systematics of carbonated ultramafic xenoliths from Mafu, Taiwan: Evidence for an extremely enriched lithospheric mantle source beneath the extended margin of the South China block

    Smith, A. D.; Wen, D.; Chung, S.; Wang, K.; Chiang, H.; Tsai, C.


    Deep-seated carbonate melt is widely proposed as an effective agent to metasomatize the lithospheric mantle. However, such carbonate melts may have a great diversity of composition and a mantle or recycled origin remains unclear. Here we present the evidence for unique carbonate metasomatism of the continental lithospheric mantle (CLM) beneath the extended southeast margin of the South China block from severely replaced spinel peridotite xenoliths from Mafu, northwestern Taiwan. The metasomatic calcitic carbonates and whole carbonated xenoliths from Mafu have unusually low trace element abundances (total REE abundance residue (86Sr/87Sr = 0.7041; ɛ Nd = +4.9, one residual sample up to +12; 206Pb/204Pb = 18.3), the Sr-Nd-Pb-C-O isotope systematics of the carbonates (86Sr/87Sr = 0.7044-0.7045; ɛ Nd = -6.9 to -7.7; 206Pb/204Pb = 18.5; δ13C = -4.5 to -5.7; δ18O = +21.8 to +22.9) reveal an extremely enriched and heterogeneous CLM. According to the Nd model age, the enriched component evolved for at least 1 Gyrs after isolation from the depleted CLM, before the Late Miocene entrapment. Coupled with high Sr/Nd, Ba/Th, La/Yb, Zr/Hf, and low Nb/U, Ce/Pb, Th/U, Ti/Eu ratios, this EM1-like metasomatic agent may be one of the most efficient percolating melt to cause disequlibrium interaction or Sr-Nd isotope decoupling. To a broader interpretation, it offers an alternative to account for some enriched signatures in mantle lithosphere, such as the extreme components of the Hawaiian plume. Instead of the "ghost plagioclase" (Sobolev et al., 2000), melting of depleted lithosphere which was metasomatized by this kind of enriched carbonate melt with high Sr, Ba, Pb but low Al and REE contents, may even better explain the geochemical features observed from the melt inclusions in Mauna Loa olivines.

  18. Worldwide lead-isotope ratio in bivalves and sediments

    Larsen, Martin Mørk; Jacobsen, Gitte; Strand, Jakob

    The lead-isotope ratio have been used to assess and identify impact of leaded gasoline, coal combustion and  mineral activities[ref 1] due to the difference in 206Pb (~52%), 207Pb (~24%) and 208Pb (~23%) isotope ratios. The source of these differences is the decaying of the parent isotopes of 238U...... to 206Pb, 235U to 207Pb and 232Th to 208Pb. 204Pb is the only stable Pb isotope usually contributing 1% of the total Pb. Differences in 206Pb/207Pb ratio ranges from 1.06 to 1.10 in old Pb ores (e.g. the time of the roman empire), whereas recent mining from radiogenic (high U and Th contents) ores can.......35% with recoveries of  98.50 to 100.03%. Geographical differences and comparison with literature values for the different regions will be presented, together with a discussion on the suitability of ICP-quadropole-MS for isotope ratio determinations. ...

  19. Insights from Pb and O isotopes into along-arc variations in subduction inputs and crustal assimilation for volcanic rocks in Java, Sunda arc, Indonesia

    Handley, Heather K.; Blichert-Toft, Janne; Gertisser, Ralf; Macpherson, Colin G.; Turner, Simon P.; Zaennudin, Akhmad; Abdurrachman, Mirzam


    New Pb isotope data are presented for Gede Volcanic Complex, Salak and Galunggung volcanoes in West Java, Merbabu and Merapi volcanoes in Central Java and Ijen Volcanic Complex in East Java of the Sunda arc, Indonesia. New O isotope data for Merbabu and new geochemical and radiogenic isotope data (Sr-Nd-Hf-Pb) for three West Javanese, upper crustal, Tertiary sedimentary rocks are also presented. The data are combined with published geochemical and isotopic data to constrain the relative importance of crustal assimilation and subducted input of crustal material in petrogenesis in Java. Also discussed are the significance of limestone assimilation in controlling the geochemical and isotopic characteristics of erupted Javanese rocks and the geochemical impact upon central and eastern Javanese arc rocks due to the subduction of Roo Rise between 105 and 109°E. The negative correlation between Pb isotopes and SiO2, combined with mantle-like δ18O values in Gede Volcanic Complex rocks, West Java, are most likely explained by assimilation of more isotopically-primitive arc rocks and/or ophiolitic crust known to outcrop in West Java. The negative Pb isotope-SiO2 trend cannot be explained by assimilation of the known compositions of the upper crustal rocks. A peak in δ18O whole-rock and mineral values in Central Javanese volcanic rocks (Merbabu and Merapi) combined with along-arc trends in Sr isotope ratios suggest that a different or additional crustal assimilant exerts control on the isotopic composition of Central Javanese volcanic rocks. This assimilant (likely carbonate material) is characterised by high δ18O and high Sr isotope ratio but is not particularly elevated in its Pb isotopic ratio. Once the effects of crustal assimilation are accounted for, strong East to West Java regional variations in Ba concentration, Ba/Hf ratio and Pb isotopic composition are evident. These differences are attributed to heterogeneity in the subducted source input component along the

  20. Lead and its isotopes in the sediment of three sites on the Lebanese coast: Identification of contamination sources and mobility

    Abi-Ghanem, C., E-mail: [Centre National des Sciences Marines, CNRSL, P.O. Box 534, Batroun (Lebanon); Chiffoleau, J.F. [Ifremer, LBCM, Centre de Nantes, BP 21105, F.44311 Nantes cedex 3 (France); Bermond, A. [Agro-ParisTech, 16, rue C. Bernard, F.75231 Paris cedex 5 (France); Nakhle, K.; Khalaf, G. [Centre National des Sciences Marines, CNRSL, P.O. Box 534, Batroun (Lebanon); Borschneck, D. [CEREGE CNRS, Aix-Marseille University, Europole Mediterraneen de l' Arbois, BP 80, 13545 Aix-en-Provence (France); Cossa, D. [Ifremer, LBCM, Centre de Nantes, BP 21105, F.44311 Nantes cedex 3 (France)


    Lead concentrations and isotopic composition of sediment samples collected from three sites within the Lebanese coastal zones were measured: at Akkar, Dora and Selaata. Akkar is located far from any direct source of contamination, while Dora and Selaata receive urban and industrial wastes, respectively. Low Pb concentrations (6-16 {mu}g g{sup -1}) were detected in the Akkar sediments, and high concentrations of Pb (70-101 {mu}g g{sup -1}) were detected in the Dora sediments. Measuring stable isotope ratios of Pb makes it possible to identify the principal sources of Pb in the Akkar sediments as Pb emitted from gasoline combustion and Pb originating from natural sources. On the other hand, Pb stable isotopic ratios in Dora sediments indicate that they are more highly influenced by anthropogenic sources. Isotopic Pb ratios in the Selaata deposits, where Pb concentrations range between 5 and 35 {mu}g g{sup -1}, have an exceptional radiogenic signature for marine sediments 1.25 < {sup 206}Pb/{sup 207}Pb < 1.6 and 0.5 < {sup 206}Pb/{sup 208}Pb < 0.67, which shows the impact of the phosphogypsum discharged by Selaata's chemical plant. Isotopic Pb analysis applied to EDTA extracts, to test the mobility of Pb, shows that that this mobility is high (>60%) after 24 h of extraction, and that the extracted Pb is less radiogenic than the residual Pb.

  1. Multiconfiguration calculations of electronic isotope shift factors in Al I

    Filippin, Livio; Ekman, Jörgen; Fritzsche, Stephan; Godefroid, Michel; Jönsson, Per


    The present work reports results from systematic multiconfiguration Dirac-Hartree-Fock calculations of electronic isotope shift factors for a set of transitions between low-lying states in neutral aluminium. These electronic quantities together with observed isotope shifts between different pairs of isotopes provide the changes in mean-square charge radii of the atomic nuclei. Two computational approaches are adopted for the estimation of the mass- and field shift factors. Within these approaches, different models for electron correlation are explored in a systematic way to determine a reliable computational strategy and estimate theoretical uncertainties of the isotope shift factors.

  2. Differentiating sources of dissolved lead in mine waters using lead isotope techniques, Sullivan Mine, British Columbia

    Lepitre, M. E.; Allen, D. M.; Mortensen, J. K.; Gabites, J. E.


    This study investigates the use of Pb isotopes in acid rock drainage studies and outlines a protocol for sampling and analysis of dissolved Pb in mine waters. Groundwaters and surface waters were sampled at the Sullivan Mine, British Columbia, to quantify Pb isotope ratios and to identify possible sources of Pb in mine effluent and back groundwaters, respectively. The Sullivan Deposit is a sediment-hosted Fe-Pb-Zn massive sulphide deposit with a well-defined homogeneous Pb isotopic composition, which provided a suitable end-member for the isotopic study. The Pb isotopic compositions of water samples define a mixing line between the homogeneous Pb isotopic signature of the Sullivan Ore and at least one other more radiogenic end-member. This end-member may correspond to Pb in the host rocks (Aldridge Formation), Pb from aerosols that have infiltrated the local surficial deposits with recharge, or Pb from the surficial deposits themselves. Further study is needed to more completely characterize the composition of potential isotopic end-members in the study area. The study demonstrates that different source regions for Pb have distinct and measurable isotopic compositions, which enable "fingerprinting" sources of Pb contamination that result from ore deposits or from other sources.

  3. Isotopic data for Late Cretaceous intrusions and associated altered and mineralized rocks in the Big Belt Mountains, Montana

    du Bray, Edward A.; Unruh, Daniel M.; Hofstra, Albert H.


    The quartz monzodiorite of Mount Edith and the concentrically zoned intrusive suite of Boulder Baldy constitute the principal Late Cretaceous igneous intrusions hosted by Mesoproterozoic sedimentary rocks of the Newland Formation in the Big Belt Mountains, Montana. These calc-alkaline plutonic masses are manifestations of subduction-related magmatism that prevailed along the western edge of North America during the Cretaceous. Radiogenic isotope data for neodymium, strontium, and lead indicate that the petrogenesis of the associated magmas involved a combination of (1) sources that were compositionally heterogeneous at the scale of the geographically restricted intrusive rocks in the Big Belt Mountains and (2) variable contamination by crustal assimilants also having diverse isotopic compositions. Altered and mineralized rocks temporally, spatially, and genetically related to these intrusions manifest at least two isotopically distinct mineralizing events, both of which involve major inputs from spatially associated Late Cretaceous igneous rocks. Alteration and mineralization of rock associated with the intrusive suite of Boulder Baldy requires a component characterized by significantly more radiogenic strontium than that characteristic of the associated igneous rocks. However, the source of such a component was not identified in the Big Belt Mountains. Similarly, altered and mineralized rocks associated with the quartz monzodiorite of Mount Edith include a component characterized by significantly more radiogenic strontium and lead, particularly as defined by 207Pb/204Pb values. The source of this component appears to be fluids that equilibrated with proximal Newland Formation rocks. Oxygen isotope data for rocks of the intrusive suite of Boulder Baldy are similar to those of subduction-related magmatism that include mantle-derived components; oxygen isotope data for altered and mineralized equivalents are slightly lighter.

  4. Exploring the isotopic niche: isotopic variance, physiological incorporation, and the temporal dynamics of foraging

    Justin Douglas Yeakel


    Full Text Available Consumer foraging behaviors are dynamic, changing in response to prey availability, seasonality, competition, and even the consumer's physiological state. The isotopic composition of a consumer is a product of these factors as well as the isotopic `landscape' of its prey, i.e. the isotopic mixing space. Stable isotope mixing models are used to back-calculate the most likely proportional contribution of a set of prey to a consumer's diet based on their respective isotopic distributions, however they are disconnected from ecological process. Here we build a mechanistic framework that links the ecological and physiological processes of an individual consumer to the isotopic distribution that describes its diet, and ultimately to the isotopic composition of its own tissues, defined as its `isotopic niche’. By coupling these processes, we systematically investigate under what conditions the isotopic niche of a consumer changes as a function of both the geometric properties of its mixing space and foraging strategies that may be static or dynamic over time. Results of our derivations reveal general insight into the conditions impacting isotopic niche width as a function of consumer specialization on prey, as well as the consumer's ability to transition between diets over time. We show analytically that moderate specialization on isotopically unique prey can serve to maximize a consumer's isotopic niche width, while temporally dynamic diets will tend to result in peak isotopic variance during dietary transitions. We demonstrate the relevance of our theoretical findings by examining a marine system composed of nine invertebrate species commonly consumed by sea otters. In general, our analytical framework highlights the complex interplay of mixing space geometry and consumer dietary behavior in driving expansion and contraction of the isotopic niche. Because this approach is established on ecological mechanism, it is well-suited for enhancing the

  5. Radiogenic neoplasia in thyroid and mammary clonogens. Final progress report, 1 January 1987--31 December 1997

    Clifton, K.H.


    The induction of cancer by ionizing radiation is a matter of great practical importance to the nuclear industry, to national defense, to radiological medicine and to the general public. It is increasingly apparent that carcinogenesis is a leading dose-limiting effect of radiation exposure. The thyroid and mammary glands are among the most sensitive human tissues to radiogenic initiation of cancer, and there is a profoundly higher risk of neoplastic initiation in these glands among individuals irradiated before or during puberty than among those exposed in later life. The authors developed unique quantitative experimental models to investigate and characterize the cells of origin of thyroid and mammary cancers and the effects of radiation on them (C185). To study these progenitor cells in vivo it is necessary to have a system by which their concentrations, total numbers and responses to radiation and other factors can be measured. It is a truism that not all cells in a tissue are equally sensitive to neoplastic initiation. They reasoned that the progenitor cells are most likely members of that subpopulation that is necessary to maintenance of normal tissue cell numbers and to repair and replacement after tissue damage. They further reasoned that such cells would likely be responsive to specific mitogenic stimulation by hormones. On the basis of these considerations, they developed quantitative rat thyroid and mammary epithelial cell transplantation systems.

  6. Detection of plutonium isotopes at lowest quantities using in-source resonance ionization mass spectrometry.

    Raeder, S; Hakimi, A; Stöbener, N; Trautmann, N; Wendt, K


    The in-source resonance ionization mass spectrometry technique was applied for quantification of ultratrace amounts of plutonium isotopes as a proof of principle study. In addition to an overall detection limit of 10(4) to 10(5) atoms, this method enables the unambiguous identification and individual quantification of the plutonium isotopes (238)Pu and (241)Pu which are of relevance for dating of radiogenic samples. Due to the element-selective ionization process, these isotopes can be measured even under a high surplus of isobaric contaminations from (238)U or (241)Am, which considerably simplifies chemical preparation. The technique was developed, tested, and characterized on a variety of synthetic and calibration samples and is presently applied to analyze environmental samples.

  7. Modeling the distribution of Nd isotopes in the oceans using an offline Ocean General Circulation Model

    Jones, K. M.; Khatiwala, S. P.; Goldstein, S. L.; Hemming, S. R.; van de Flierdt, T.


    The authigenic (seawater-derived) Nd isotopic composition of marine archives is increasingly used to study changes in ocean circulation on tectonic to millennial time-scales. Such applications for Nd isotopes assume that water masses are "tagged" with distinct Nd isotopic compositions in source regions and mix quasi- conservatively thereafter. However, there are a number of possible sources and sinks of Nd within the ocean that may complicate quasi-conservative behavior, including input from rivers, dissolution of dust, exchange at continental margin boundaries, and fluxes from the ocean-sediment interface. We use an offline ocean general circulation model (OGCM) to model the distribution of Nd isotope variability in seawater. A major obstacle to a thorough understanding of the marine Nd cycle is the lack of a truly global dataset of Nd isotopes in the modern oceans--most data are focused in only a few regions of the ocean. However, even within the constraints of sparse data, a better understanding of sources, sinks, and internal cycling of Nd and its isotopes can be reached through ocean modeling. We take a simple approach, treating the Nd isotopic composition of seawater as a conservative tracer, neglecting the effect of variable Nd concentrations on mixing. Nd isotope data from modern surface waters are used to generate a map of Nd isotope compositions for the entire surface ocean. This map is treated as a fixed boundary condition, and Nd isotope compositions of the surface are transported and mixed according to the flow characteristics of the OGCM until the interior ocean reaches a steady state. This simple approach produces Nd isotope estimates for North Atlantic Deep Water that are consistent with the observations, but produces values lower than observed in the deep Pacific and Southern Oceans. However, by introducing an additional source of Nd in the deep Pacific with higher Nd isotope ratios, the model output agrees well with the data. With the addition of

  8. Strontium Isotopes and the Reconstruction of the Chaco Regional System: Evaluating Uncertainty with Bayesian Mixing Models

    Drake, Brandon Lee; Wills, Wirt H.; Hamilton, Marian I.; Dorshow, Wetherbee


    Strontium isotope sourcing has become a common and useful method for assigning sources to archaeological artifacts. In Chaco Canyon, an Ancestral Pueblo regional center in New Mexico, previous studies using these methods have suggested that significant portion of maize and wood originate in the Chuska Mountains region, 75 km to the East. In the present manuscript, these results were tested using both frequentist methods (to determine if geochemical sources can truly be differentiated) and Bayesian methods (to address uncertainty in geochemical source attribution). It was found that Chaco Canyon and the Chuska Mountain region are not easily distinguishable based on radiogenic strontium isotope values. The strontium profiles of many geochemical sources in the region overlap, making it difficult to definitively identify any one particular geochemical source for the canyon's pre-historic maize. Bayesian mixing models support the argument that some spruce and fir wood originated in the San Mateo Mountains, but that this cannot explain all 87Sr/86Sr values in Chaco timber. Overall radiogenic strontium isotope data do not clearly identify a single major geochemical source for maize, ponderosa, and most spruce/fir timber. As such, the degree to which Chaco Canyon relied upon outside support for both food and construction material is still ambiguous. PMID:24854352

  9. Strontium isotopes and the reconstruction of the Chaco regional system: evaluating uncertainty with Bayesian mixing models.

    Brandon Lee Drake

    Full Text Available Strontium isotope sourcing has become a common and useful method for assigning sources to archaeological artifacts.In Chaco Canyon, an Ancestral Pueblo regional center in New Mexico, previous studiesusing these methods have suggested that significant portion of maize and wood originate in the Chuska Mountains region, 75 km to the West [corrected]. In the present manuscript, these results were tested using both frequentist methods (to determine if geochemical sources can truly be differentiated and Bayesian methods (to address uncertainty in geochemical source attribution. It was found that Chaco Canyon and the Chuska Mountain region are not easily distinguishable based on radiogenic strontium isotope values. The strontium profiles of many geochemical sources in the region overlap, making it difficult to definitively identify any one particular geochemical source for the canyon's pre-historic maize. Bayesian mixing models support the argument that some spruce and fir wood originated in the San Mateo Mountains, but that this cannot explain all 87Sr/86Sr values in Chaco timber. Overall radiogenic strontium isotope data do not clearly identify a single major geochemical source for maize, ponderosa, and most spruce/fir timber. As such, the degree to which Chaco Canyon relied upon outside support for both food and construction material is still ambiguous.

  10. Pb isotopic geochemical study on the crustal structure of Tongbaishan


    Pb isotopic composition of the Tongbai complex, distributed in the Tongbaishan to the west of the Dabieshan, ranges between the Dabie core complex and the Dabie ultral-high pressure (UHP) metamorphic complex, the latter having more radiogenic Pb isotopic composition than the former. Granites from the Jigongshan pluton, which intruded mainly into the Tongbai complex, are distinct from the Tongbai complex but similar to the Dabie core complex in Pb isotopic composition, showing that the magma of the Jigongshan granites was derived from the partial melting of the Dabie core complex. According to Pb isotopic compositional variation model in the vertical crustal section and magma source from the Jigongshan pluton, it is suggested that the Tongbai complex was an upper rock serial of the Dabie core complex, which is beneath the Dabie UHP metamorphic complex in the crustal structure of the Tongbai-Dabie orogenic belt. The Tongbai complex was not well preserved in the Dabie area due to the high exhumed crustal section. However, the crustal section in the Tongbai area was exhumed less than that in the Dabie area, and the deep crust in the Tongbai area still contains the basement composition similar to the Dabie core complex. Therefore, the crustal basements from the Dabie to Tongbai areas are united. The present distribution of the basement blocks in different locations of the Tongbai-Dabie orogenic belt reflects different exposure of the crustal section.

  11. Isotopic constraints of mantle derived carbonatitic melts from Calatrava, Spain

    Humphreys, E. R.; Bailey, K.; Hawkesworth, C. J.; Wall, F.; Avanzinelli, R.


    Carbonatite volcanism is typically associated both spatially and temporally with alkaline, ultramafic volcanism (Woolley & Church, 2005). Recent discoveries in Calatrava, Spain illustrate the activity of carbonatite in the source melts of leucitite volcanism. Melilitite pyroclastic lapilli tuffs also show a clear association with volcanic carbonate. Carbonatitic activity has been shown to initiate at depths greater than 100km (Humphreys et al., 2010) despite a maximum estimate of lithospheric thickness of 80km. The presence of aragonite and abundant mantle xenoliths in many deposits are clear indication of the rapid emplacement rates of such magmas. Carbonatitic activity in the source of the leucitite melts is indicated by carbonate inclusions within olivine xenocrysts and the presence of occasional carbonatite lenses. The composition of lead and strontium isotope ratios in the bulk rock, and spatially resolved analysis of carbonate from the groundmass and from inclusions demonstrates a genetic affinity between the inclusions and the related bulk rock composition. Lead and strontium isotopic analysis suggest that such melts do not represent the composition of convecting asthenospheric mantle. 87Sr/86Sr (0.7055-0.7068) values are higher than those of MORB and most OIB. Lead isotope ratios show a trend displaced to higher 207Pb/204Pb relative to MORB and OIB. Carbonate inclusions have less radiogenic lead values than the more radiogenic bulk rocks. Our data indicate that carbonatitic activity in the mantle is intrinsic in the generation of the leucitite lava. However, petrographic and isotopic evidence suggest a complex melt history. Olivine xenocrysts are not in equilibrium with the host leucitite, despite inclusions within olivine showing an isotopic affinity to the bulk rock. We suggest that in this example, alkaline magmatism was induced by the presence of CO2 in the mantle source. Isotopic evidence shows that the mantle producing such melts was not

  12. Isotopic characterisation of the sub-continental lithospheric mantle beneath Zealandia, a rifted fragment of Gondwana

    Waight, Tod Earle; Scott, James M.; van der Meer, Quinten Har Adriaan


    and that contained a HIMU component. The volcanics have tapped two adjacent but chemically contrasting upper mantle domains: a fertile eastern domain and an extremely depleted western domain. Both domains underlie Mesozoic metasedimentary crust. Radiogenic isotope compositions of the clinopyroxene have 87Sr/86Sr......The greater New Zealand region, known as Zealandia, represents an amalgamation of crustal fragments accreted to the paleo-Pacific Gondwana margin and which underwent significant thinning during the subsequent split from Australia and Antarctica in the mid-Cretaceous following opening of the Tasman...

  13. Carbon isotopes as indicators of peatland growth?

    Alewell, Christine; Krüger, Jan Paul; von Sengbusch, Pascal; Szidat, Sönke; Leifeld, Jens


    As undisturbed and/or growing peatlands store considerable amounts of carbon and are unique in their biodiversity and species assemblage, the knowledge of the current status of peatlands (growing with carbon sequestration, stagnating or degrading with carbon emissions) is crucial for landscape management and nature conservation. However, monitoring of peatland status requires long term measurements and is only feasible with expert knowledge. The latter determination is increasingly impeded in a scientific world, where taxonomic expert knowledge and funding of long term monitoring is rare. Stable carbon and nitrogen isotopes depth profiles in peatland soils have been shown to be a useful tool to monitor the degradation of peatlands due to permafrost thawing in Northern Sweden (Alewell et al., 2011; Krüger et al., 2014), drainage in Southern Finland (Krüger et al., 2016) as well as land use intensification in Northern Germany (Krüger et al., 2015). Here, we tackle the questions if we are able to differentiate between growing and degrading peats with the use of a combination of carbon stable (δ13C) and radiogenic isotope data (14C) with peat stratification information (degree of humification and macroscopic plant remains). Results indicate that isotope data are a useful tool to approximate peatland status, but that expert taxonomic knowledge will be needed for the final conclusion on peatland growth. Thus, isotope tools might be used for landscape screening to pin point sites for detailed taxonomic monitoring. As the method remains qualitative future research at these sites will need to integrate quantitative approaches to determine carbon loss or gain (soil C balances by ash content or C accumulation methods by radiocarbon data; Krüger et al., 2016). Alewell, C., R. Giesler, J. Klaminder, J. Leifeld, and M. Rollog. 2011. Stable carbon isotopes as indicators for micro-geomorphic changes in palsa peats. Biogeosciences, 8, 1769-1778. Krüger, J. P., Leifeld, J

  14. Assessment of pollution aerosols sources above the Straits of Dover using lead isotope geochemistry.

    Deboudt, K; Flament, P; Weis, D; Mennessier, J P; Maquinghen, P


    We assess the capability of lead isotopes to study the transport of pollution aerosols above the Straits of Dover by collecting atmospheric aerosols above the Eastern Channel and the Southern Bight of the North Sea. During the same period, we characterized the lead isotopic signature of the main industrial sources on the French coast near the Straits of Dover. Urban and automobile-derived aerosols were also collected. Due to the phasing out of lead in gasoline, the urban isotopic composition (206Pb/207Pb = 1.158 +/- 0.003) has become more radiogenic, although it is highly variable. On a regional scale, major industrial emissions have a well-defined isotopic composition (1.13 isotopic compositions, it can be shown that lead aerosols originating from eastern Europe have an isotopic signature (1.145 isotopic composition of west-European lead aerosols (1.111 < 206Pb/207Pb < 1.142). The influence of remote North American sources is suggested, with caution, due to uncertainties in meteorological calculations.

  15. Ar Ar dating of authigenic K-feldspar: Quantitative modelling of radiogenic argon-loss through subgrain boundary networks

    Mark, D. F.; Kelley, S. P.; Lee, M. R.; Parnell, J.; Sherlock, S. C.; Brown, D. J.


    We have analysed two distinct generations of authigenic K-feldspar in Fucoid Bed sandstones from An-t-Sron and Skiag Bridge, NW Highlands, Scotland, which have experienced post-growth heating to levels in excess of the predicted Ar-closure temperature. Authigenic K-feldspars show microtextural similarities to patch perthites; that is subgrains separated by dislocation-rich boundary networks that potentially act as fast diffusion pathways for radiogenic argon. The two generations of authigenic K-feldspar in the Fucoid Bed sandstones can be distinguished by different microtextural zones, bulk mineral compositions, fluid-inclusion populations, and inferred temperatures and chemistries of parent fluids. Ar-Ar age data obtained using high-resolution ultraviolet laser ablation, show that the first cementing generation is Ordovician and the second cementing generation is Silurian. Modelling of Ar diffusion using subgrain size as the effective diffusion dimension and a simplified tectono-thermal thrust model assuming transient heating of the Fucoid Beds is inconsistent with observed data. Removal of heat from the thrust zone through rapid flushing of heated fluids rather than transient heating can be invoked to explain the observed Ar-Ar ages for both generations of cement. Alternatively, Ar-diffusion modelling using overgrowth thickness as the effective diffusion dimension instead of subgrain size also yields models that are consistent with both the Fucoid Bed palaeothermal maxima and determined Ar-Ar age ages for the two generations of K-feldspar cement. Based on this alternate explanation, we propose a theoretical microtextural model that highlights fundamental differences between the microtextures of deuterically formed patch perthites and authigenic K-feldspars, explaining the apparent robustness of authigenic K-feldspar with respect to Ar-retention.

  16. Radiogenic Side Effects After Hypofractionated Stereotactic Photon Radiotherapy of Choroidal Melanoma in 212 Patients Treated Between 1997 and 2007

    Dunavoelgyi, Roman [Department of Ophthalmology, Medical University of Vienna, Vienna (Austria); Dieckmann, Karin [Department of Radiology, Medical University of Vienna, Vienna (Austria); Gleiss, Andreas [Section of Clinical Biometrics, Medical University of Vienna, Vienna (Austria); Sacu, Stefan; Kircher, Karl; Georgopoulos, Michael [Department of Ophthalmology, Medical University of Vienna, Vienna (Austria); Georg, Dietmar [Department of Radiology, Medical University of Vienna, Vienna (Austria); Zehetmayer, Martin, E-mail: [Department of Ophthalmology, Medical University of Vienna, Vienna (Austria); Poetter, Richard [Department of Radiology, Medical University of Vienna, Vienna (Austria)


    Purpose: To evaluate side effects of hypofractionated stereotactic photon radiotherapy for patients with choroidal melanoma. Patients and Methods: Two hundred and twelve patients with choroidal melanoma unsuitable for ruthenium-106 brachytherapy or local resection were treated stereotactically at the Medical University of Vienna between 1997 and 2007 with a Linac with 6-MV photon beams in five fractions with 10, 12, or 14 Gy per fraction. Examinations for radiogenic side effects were performed at baseline and every 3 months in the first 2 years, then every 6 months until 5 years and then once a year thereafter until 10 years after radiotherapy. Adverse side effects were assessed using slit-lamp examination, funduscopy, gonioscopy, tonometry, and, if necessary, fundus photography and fluorescein angiography. Evaluations of incidence of side effects are based on an actuarial analysis. Results: One hundred and eighty-nine (89.2%) and 168 (79.2%) of the tumors were within 3 mm of the macula and the optic disc, respectively. The five most common radiotherapy side effects were retinopathy and optic neuropathy (114 cases and 107 cases, respectively), cataract development (87 cases), neovascular glaucoma (46 cases), and corneal epithelium defects (41 cases). In total, 33.6%, 38.5%, 51.2%, 75.5%, and 77.6% of the patients were free of any radiation retinopathy, optic neuropathy, cataract, neovascular glaucoma, or corneal epithelium defects 5 years after radiotherapy, respectively. Conclusion: In centrally located choroidal melanoma hypofractionated stereotactic photon radiotherapy shows a low to moderate rate of adverse long-term side effects comparable with those after proton beam radiotherapy. Future fractionation schemes should seek to further reduce adverse side effects rate while maintaining excellent local tumor control.

  17. [RET/PTC Gene Rearrangements in the Sporadic and Radiogenic Thyroid Tumors: Molecular Genetics, Radiobiology and Molecular Epidemiology].

    Ushenkova, L N; Koterov, A N; Biryukov, A P


    A review of molecular genetic, radiobiological and molecular epidemiological studies of gene (chromosome) rearrangements RET/PTC in the cells of the thyroid gland as well as the laws in relation to radiation exposure in vitro, in vivo and human populations identified with them are submitted. The data on the c-RET gene and its chimeric constructs with the gene-donors (RET/PTC rearrangements) are considered. The information about the history of the RET/PTC discovery, their types, carcinogenic potential and specificity both to tumor and non-tumor thyroid disease especially for papillary thyroid carcinoma are provided. The data (seven studies) on the induction of RET/PTC after irradiation of tumor and normal thyroid cells in vitro and mice are reviewed. The mechanisms of RET/PTC induction may be associated with DNA double strand breaks and oxidative stress. Some information (three publications) about the possibility of RET/PTC induction by low doses of radiation with low LET (to 0.1 Gy) is given and it is concluded that their potential evidentiary is generally weak. The achievements in the molecular epidemiology of RET/PTC frequency for exposed and unexposed cohorts are stated. At the same time it is noted that, despite the vast array. of data accumulated from 30 countries of the world and more than 20 years of research, the formed provisions are weakly confirmed statistically and have no base corresponding to the canons of evidence-based medicine. The possibility of use of the RET/PTC presence or their frequencies as markers of the papillary thyroid carcinomas and, specifically, their radiogenic forms, is considered. In the first case the answer may be positive, while in the second, the situation is characterized by uncertainty. Based to the above mentioned we came to a conclusion about the need of a pooled or meta-analysis of the totality of the published data.

  18. Lead isotope ratios in tree bark pockets: An indicator of past air pollution in the Czech Republic

    Conkova, M. [Charles University, Faculty of Natural Sciences, Benatska 8, Prague 1 (Czech Republic)], E-mail:; Kubiznakova, J. [Czech Hydrometeorogical Institute, Na Sabatce 17, Prague 4 (Czech Republic)], E-mail:


    Tree bark pockets were collected at four sites in the Czech Republic with differing levels of lead (Pb) pollution. The samples, spanning 1923-2005, were separated from beech (Fagus sylvatica) and spruce (Picea abies). Elevated Pb content (0.1-42.4 {mu}g g{sup -1}) reflected air pollution in the city of Prague. The lowest Pb content (0.3-2.6 {mu}g g{sup -1}) was found at the Kosetice EMEP 'background pollution' site. Changes in {sup 206}Pb/{sup 207}Pb and {sup 208}Pb/{sup 206}Pb isotope ratios were in agreement with operation times of the Czech main anthropogenic Pb sources. Shortly after the Second World War, the {sup 206}Pb/{sup 207}Pb isotope ratio in bark pockets decreased from 1.17 to 1.14 and the {sup 208}Pb/{sup 206}Pb isotope ratio increased from 2.12 to 2.16. Two dominant emission sources responsible for these changes, lignite and leaded petrol combustion, contributed to the shifts in Pb isotope ratios. Low-radiogenic petrol Pb ({sup 206}Pb/{sup 207}Pb of 1.11) lead to lower {sup 206}Pb/{sup 207}Pb in bark pockets over time. High-radiogenic lignite-derived Pb ({sup 206}Pb/{sup 207}Pb of 1.18 to 1.19) was detected in areas affected by coal combustion rather than by traffic.

  19. Isotopic signatures for natural versus anthropogenic Pb in high-altitude Mt. Everest ice cores during the past 800 years.

    Lee, Khanghyun; Hur, Soon Do; Hou, Shugui; Burn-Nunes, Laurie J; Hong, Sungmin; Barbante, Carlo; Boutron, Claude F; Rosman, Kevin J R


    A long-term record, extending back 800 years (1205 to 2002 AD), of the Pb isotopic composition ((206)Pb/(207)Pb and (208)Pb/(207)Pb) as well as Pb concentrations from high altitude Mt. Everest ice cores has the potential to identify sources and source regions affecting natural and anthropogenic Pb deposition in central Asia. The results show that the regional natural background Pb isotope signature (~1.20 for (206)Pb/(207)Pb and ~2.50 for (208)Pb/(207)Pb) in the central Himalayas was dominated by mineral dust over the last ~750 years from 1205 to 1960s, mostly originating from local sources with occasional contributions of long-range transported dust probably from Sahara desert and northwestern India. Since the 1970s, the Pb isotope ratios are characterized by a continuous decline toward less radiogenic ratios with the least mean ratios of 1.178 for (206)Pb/(207)Pb and 2.471 for (208)Pb/(207)Pb in the period 1990-1996. The depression of the (206)Pb/(207)Pb and (208)Pb/(207)Pb values during the corresponding periods is most likely due to an increasing influence of less radiogenic Pb of anthropogenic origin mainly from leaded gasoline used in South Asia (India as well as possibly Bangladesh and Nepal). From 1997 to 2002, isotopic composition tends to show a shift to slightly more radiogenic signature. This is likely attributed to reducing Pb emissions from leaded gasoline in source regions, coinciding with the nationwide reduction of Pb in gasoline and subsequent phase-out of leaded gasoline in South Asia since 1997. An interesting feature is the relatively high levels of Pb concentrations and enrichment factors (EF) between 1997 and 2002. Although the reason for this feature remains uncertain, it would be probably linked with an increasing influence of anthropogenic Pb emitted from other sources such as fossil fuel combustion and non-ferrous metal production.

  20. I-Xe systematics of the impact plume produced chondrules from the CB carbonaceous chondrites: Implications for the half-life value of 129I and absolute age normalization of 129I-129Xe chronometer

    Pravdivtseva, O.; Meshik, A.; Hohenberg, C. M.; Krot, A. N.


    It is inferred that magnesian non-porphyritic chondrules in the CB (Bencubbin-type) carbonaceous chondrites formed in an impact generated plume of gas and melt at 4562.49 ± 0.21 Ma (Bollard et al., 2015) and could be suitable for the absolute age normalization of relative chronometers. Here xenon isotopic compositions of neutron irradiated chondrules from the CB chondrites Gujba and Hammadah al Hamra (HH) 237 have been analyzed in an attempt to determine closure time of their I-Xe isotope systematics. One of the HH 237 chondrules, #1, yielded a well-defined I-Xe isochron that corresponds to a closure time of 0.29 ± 0.16 Ma after the Shallowater aubrite standard. Release profiles and diffusion properties of radiogenic 129*Xe and 128*Xe, extracted from this chondrule by step-wise pyrolysis, indicate presence of two iodine host phases with distinct activation energies of 73 and 120 kcal/mol. In spite of the activation energy differences, the I-Xe isotope systematics of these two phases closed simultaneously, suggesting rapid heating and cooling (possibly quenching) of the CB chondrules. The release profiles of U-fission Xe and I-derived Xe correlate in the high temperature host phase supporting simultaneous closure of 129I-129Xe and 207Pb-206Pb systematics. The absolute I-Xe age of Shallowater standard is derived from the observed correlation between I-Xe and Pb-Pb ages in a number of samples. It is re-evaluated here using Pb-Pb ages adjusted for an updated 238U/235U ratio of 137.794 and meteorite specific U-isotope ratios. With the addition of the new data for HH 237 chondrule #1, the re-evaluated absolute I-Xe age of Shallowater is 4562.4 ± 0.2 Ma. The absolute I-Xe age of the HH 237 chondrule #1 is 4562.1 ± 0.3 Ma, in good agreement with U-corrected Pb-Pb ages of the Gujba chondrules (Bollard et al., 2015) and HH 237 silicates (Krot et al., 2005). All I-Xe data used here, and in previous estimates of the absolute age of Shallowater, are calculated using 15.7

  1. Differences between boninite and tholeiite primary magmas in Izu-Bonin-Mariana arc: constraints from an Os isotope perspective

    Senda, R.; Shimizu, K.; Suzuki, K.


    Geochemical data of arc primary magmas provide information on how elements behave in the subduction system. In order to constrain Os behavior in a subduction system, Os isotope ratios of whole rock and chromium spinels (Cr-spinels) in boninites, a type of high-Mg andesite, and tholeiites from Izu-Bonin-Mariana (IBM) arc, have been determined. Cr-spinel crystallizes at an early stage of fractional crystallization and therefore can preserve primary information of its magma source. Furthermore Os is highly compatible in Cr-spinels, and thus Os isotope ratios determined from Cr-spinel in volcanic rocks provide information on the magmatic history and origin. We investigated the difference in Os isotopic compositions between the primary boninite and primary tholeiite in IBM arc to understand the behavior of Os during arc magma generation. The whole rock Os isotope ratios of both boninites (187Os/188Os = 0.1240-0.1828) and tholeiites (187Os/188Os = 0.1658-0.2832) are higher and more variable than those of Cr-spinels (from boninites: 187Os/188Os = 0.1229-0.1242, from tholeiites: 187Os/188Os = 0.1429-0.1512). In both cases, this is likely to be due to the rock assimilating crustal materials with more radiogenic Os isotope ratios than the mantle during magma ascent after Cr-spinel crystallization. The initial Os isotope ratios of Cr-spinel from boninites (187Os/188Os(i) = 0.1206-0.1242) are similar to those of abyssal peridotites from the forearc region of IBM [1]. This suggests that the Os in the boninite primary magma originates from unradiogenic depleted mantle, not from radiogenic fertile mantle or subducted materials. On the other hand, Os isotope ratios of Cr-spinels from tholeiites are higher than those from boninites. Crustal contamination possibly contributed to the more radiogenic Os isotopic composition of the tholeiite magma. The difference in Os isotope ratios between boninite and tholeiites indicate that they have a different origin and evolutionary history

  2. Osmium isotopes and the Upper Devonian "Kellwasser" event

    Brauns, M.


    The Upper Devonian "Kellwasser" horizon at the Frasnian/Famennian boundary (~367 Ma) records one of the most severe world-wide catastrophic bio-events in Earth's history. Current theories for the causes of mass extinction include (e.g. Schindler 1990) (i) meteoritic impact, (ii) sea-level changes, shifts of the sedimentary realm and generation of anoxic milieus, (iii) enhanced clastic input and modification of sea water chemistry, and, possibly, (iv) a combination of (ii) and (iii). The time-integrated Os isotopic composition of Kellwasser limestones appears to be a suitable tool to shed light on these options and possibly place constraints on the Os isotopic evolution of Upper Devonian sea water. We present complete Re-Os analyses of limestone and shale whole rock samples, and some biogenic/diagenetic constituents (conodonts, Fe oxides). The results indicate extreme Re and Os compositional variations between different limestone and shale sublayers (Re = 0.1 - 40 ppb, Os 26 - 830 ppt, Re/Os = 4 - 240). The present Os isotopic ratios of the rocks were found to be very radiogenic (187Os/186Os = 9,865 - 388,35). For the first time, conodont samples extracted from the Kellwasser sequence were tested as potential tracers for the Os isotopic composition of Upper Devonian sea water. Their Os contents are in the range of 210 - 112 ppt, which required analysis of about 15.000 specimens per sample to obtain sufficient Os for mass spectrometry. The Os of the conodonts (187Os/186Os = 14,35 - 67,89) is significantly less radiogenic compared to their complementary host rocks. Their 187Re/186Os, however, exceed the 187Re/186Os ratios of the host limestones by at least 1-2 orders of magnitude. Recalculation of the 187Re/186Os ratios of all rock and conodont samples for an age of 367 Ma yielded in all cases unrealistic and very contrasting values with respect to any hypothetical Os isotopic composition of Upper Devonian sea water. Our Re-Os isotopic data do establish several points

  3. Isotope geology of the bakircay porphyry copper prospect, northern turkey

    Taylor, R. P.


    Isotopic data for the Bakircay granodiorite porphyry, MediaObjects/126_2005_BF01798964_f1.tif give a Late Eocene age for the development of the porphyry copper system. They suggest a close temporal and genetic relationship between igneous and hydrothermal activity, and indicate that magmatic-hydrothermal fluids produced potassic alteration and that meteoric fluids enriched in radiogenic87Sr were responsible for propylitic alteration. The granodiorite porphyry is petrologically similar to porphyry copper-related intrusions from island arc and continental margin settings, which form a group with initial87Sr/86Sr ratios of less than 0. 7043, representing magmas produced in tectonic environments lacking any important component of old (i. e. Precambrian) continental material.

  4. Isotopic and geochemical signatures of Late Quaternary sediments in the Fram Strait area

    Maccali, J.; Hillaire-Marcel, C.; Carignan, J.; Reisberg, L. C.


    Arctic freshwater/sea-ice export through Fram Strait contributes to the Atlantic Meridional Overturning Circulation (AMOC) and acts as a trigger or feedback mechanism in the climate/ocean system. Here, geochemical and isotopic analyses of cores raised along a transect through the Strait are used to document changes in sediment sources and sea-ice transport since the LGM. Radiogenic isotope and elemental data in leachable fractions vs residues are used as proxies for water mass vs sediment source signatures, respectively. Unequivocal linkage between leachates and water-mass properties are illustrated by the anthropogenic-lead overprint in leachates from core-top sediments. Below this polluted layer, leachates and residues from late Holocene sediments carry distinct geochemical signatures E and W of the Strait. Eastward, below the North Atlantic Water (NAW) mass flowing northward, Th/Zr and Th/Pb concentration ratios ranging 0.040-0.041 and 0.85-0.90, respectively, label GIN seas and western Spitzbergen sediment-sources. Westward, below outflowing Arctic waters and sea-ice routes, these ratios range 0.032-0.035 and 0.72-0.75, respectively, and label NE Greenland and Arctic sediment sources. Pb-isotopes exhibit a similar pattern with sediment carrying a mixed Variscan-Pan-African signature below the NAW route, and a mixture of less radiogenic sources in sediments deposited below the outflowing Arctic waters and sea-ice route. Back in time, divergent trends in some radiogenic isotope values are recorded westward, below the outflowing Arctic waters and sea-ice route. Whereas isotopic properties of residues suggest sedimentary supplies originating from the Canadian Arctic and/or the NW Greenland margin, lead data from leachates bear an "Arctic Ocean" signature illustrating variable relative contributions from the Russian vs Canadian ice-margins and/or rivers. During deglacial times, a significant change in sedimentary supplies is recorded at ~ 14 ka along with some

  5. Barite mineralization in Kalana speleothems, Central Estonia: Sr, S and O isotope characterization

    Mikk Gaškov


    Full Text Available Barite mineralization in association with calcitic speleothem precipitates in cave structures in Silurian Aeronian carbonate rocks in Kalana quarry, Central Estonia, was studied. Barite mineralization in Kalana occurs in two generations – euhedral bladed-tabular barite zonal crystals from a few to 10 cm in size, growing on the limestone-dolomite wall-rock (generation I, and sparsely placed thin tabular crystals a few millimetres thick and up to 1 cm in size, growing on calcitic crusts (generation II. The barite crystals of generation I are frequently found embedded by paragenetically later calcitic botryoidal crusts. The Sr and S isotopic composition of barite crystals shows a trend of increasing Sr isotope ratios (from 0.7114 to 0.7120 and δ34S values (from 13‰ to 33‰ from the central parts towards the edges of zonal crystals. This suggests barite precipitation by mixing of two endmember fluids at varying ratios during barite formation: warm (up to 70 °C reducing fluid bearing Ba, characterized by an elevated radiogenic Sr- and 34S-enriched isotopic signal, and a cooler ambient fluid bearing an isotopically lighter dissolved sulphate, characterized by lower Sr isotope ratios. The excess of radiogenic 87Sr in barite compared to Phanerozoic seawater values suggests Sr derived from a continental source, whereas sulphate was derived either from oxidized H2S or a modified seawater source. Gradual increase in δ34S values towards the outer zones could also indicate the 34S enrichment due to bacterial sulphate reduction, even though there is no paired 34S and 18O enrichment of sulphate, characteristic of bacterial reworking. This can be interpreted as indicating an open system with limited sulphate resupply where the δ18O composition of sulphate was equilibrated with warm ascending hydrothermal fluid.

  6. The terrestrial uranium isotope cycle.

    Andersen, Morten B; Elliott, Tim; Freymuth, Heye; Sims, Kenneth W W; Niu, Yaoling; Kelley, Katherine A


    Changing conditions on the Earth's surface can have a remarkable influence on the composition of its overwhelmingly more massive interior. The global distribution of uranium is a notable example. In early Earth history, the continental crust was enriched in uranium. Yet after the initial rise in atmospheric oxygen, about 2.4 billion years ago, the aqueous mobility of oxidized uranium resulted in its significant transport to the oceans and, ultimately, by means of subduction, back to the mantle. Here we explore the isotopic characteristics of this global uranium cycle. We show that the subducted flux of uranium is isotopically distinct, with high (238)U/(235)U ratios, as a result of alteration processes at the bottom of an oxic ocean. We also find that mid-ocean-ridge basalts (MORBs) have (238)U/(235)U ratios higher than does the bulk Earth, confirming the widespread pollution of the upper mantle with this recycled uranium. Although many ocean island basalts (OIBs) are argued to contain a recycled component, their uranium isotopic compositions do not differ from those of the bulk Earth. Because subducted uranium was probably isotopically unfractionated before full oceanic oxidation, about 600 million years ago, this observation reflects the greater antiquity of OIB sources. Elemental and isotope systematics of uranium in OIBs are strikingly consistent with previous OIB lead model ages, indicating that these mantle reservoirs formed between 2.4 and 1.8 billion years ago. In contrast, the uranium isotopic composition of MORB requires the convective stirring of recycled uranium throughout the upper mantle within the past 600 million years.

  7. Laser Spectroscopy of Neutron Rich Bismuth Isotopes


    %IS344 :\\\\ \\\\ The aim of the experiment is to measure the optical isotope shifts and hyperfine structures of bismuth isotopes across the N=126 shell closure in order to extract the change in mean square charge radii ($\\delta\\langle r^{2}\\rangle$) and static moments. These include the first isotones of lead to be measured directly above the shell closure and will provide new information on the systematics of the kink ($\\delta\\langle r^{2}\\rangle)$ seen in the lead isotopic chain. After two very successful runs the programme has been extended to include the neutron deficient isotopes below $^{201}$Bi to study the systematics across the $i_{13/2}$ neutron sub-shell closure at N=118.\\\\ \\\\ During the initial 2 runs (9 shifts) the isotope shifts and hyperfine structures of three new isotopes, $ ^{210,212,213}$Bi and the 9$^{-}$ isomer of $^{210}$Bi have been measured. The accuracy of the previous measurements of $^{205,206,208}$Bi have been greatly improved. The samples of $ ^{208,210,210^{m}}$Bi were prepared by c...

  8. Out-of-field organ doses and associated radiogenic risks from para-aortic radiotherapy for testicular seminoma

    Mazonakis, Michalis, E-mail:; Berris, Theocharis; Damilakis, John [Department of Medical Physics, Faculty of Medicine, University of Crete, P. O. Box 2208, 71003 Iraklion, Crete (Greece); Varveris, Charalambos; Lyraraki, Efrossyni [Department of Radiotherapy and Oncology, University Hospital of Iraklion, 71110 Iraklion, Crete (Greece)


    Purpose: The aims of this study were to (a) calculate the radiation dose to out-of-field organs from radiotherapy for stage I testicular seminoma and (b) estimate the associated radiogenic risks. Methods: Monte Carlo methodology was employed to model radiation therapy with typical anteroposterior and posteroanterior para-aortic fields on an anthropomorphic phantom simulating an average adult. The radiation dose received by all main and remaining organs that defined by the ICRP publication 103 and excluded from the treatment volume was calculated. The effect of field dimensions on each organ dose was determined. Additional therapy simulations were generated by introducing shielding blocks to protect the kidneys from primary radiation. The gonadal dose was employed to assess the risk of heritable effects for irradiated male patients of reproductive potential. The lifetime attributable risks (LAR) of radiotherapy-induced cancer were estimated using gender- and organ-specific risk coefficients for patient ages of 20, 30, 40, and 50 years old. The risk values were compared with the respective nominal risks. Results: Para-aortic irradiation to 20 Gy resulted in out-of-field organ doses of 5.0–538.6 mGy. Blocked field treatment led to a dose change up to 28%. The mean organ dose variation by increasing or decreasing the applied field dimensions was 18.7% ± 3.9% and 20.8% ± 4.5%, respectively. The out-of-field photon doses increased the lifetime intrinsic risk of developing thyroid, lung, bladder, prostate, and esophageal cancer by (0.1–1.4)%, (0.4–1.1)%, (2.5–5.4)%, (0.2–0.4)%, and (6.4–9.2)%, respectively, depending upon the patient age at exposure and the field size employed. A low risk for heritable effects of less than 0.029% was found compared with the natural incidence of these defects. Conclusions: Testicular cancer survivors are subjected to an increased risk for the induction of bladder and esophageal cancer following para-aortic radiotherapy. The

  9. Seawater osmium isotope evidence for a middle Miocene flood basalt event in ferromanganese crust records

    Klemm, Veronika; Frank, Martin; Levasseur, Sylvain; Halliday, Alex N.; Hein, James R.


    Three ferromanganese crusts from the northeast, northwest and central Atlantic were re-dated using osmium (Os) isotope stratigraphy and yield ages from middle Miocene to the present. The three Os isotope records do not show evidence for growth hiatuses. The reconstructed Os isotope-based growth rates for the sections older than 10 Ma are higher than those determined previously by the combined beryllium isotope (10Be/9Be) and cobalt (Co) constant-flux methods, which results in a decrease in the maximum age of each crust. This re-dating does not lead to significant changes to the interpretation of previously determined radiogenic isotope neodymium, lead (Nd, Pb) time series because the variability of these isotopes was very small in the records of the three crusts prior to 10 Ma. The Os isotope record of the central Atlantic crust shows a pronounced minimum during the middle Miocene between 15 and 12 Ma, similar to a minimum previously observed in two ferromanganese crusts from the central Pacific. For the other two Atlantic crusts, the Os isotope records and their calibration to the global seawater curve for the middle Miocene are either more uncertain or too short and thus do not allow for a reliable identification of an isotopic minimum. Similar to pronounced minima reported previously for the Cretaceous/Tertiary and Eocene/Oligocene boundaries, possible interpretations for the newly identified middle Miocene Os isotope minimum include changes in weathering intensity and/or a meteorite impact coinciding with the formation of the Nördlinger Ries Crater. It is suggested that the eruption and weathering of the Columbia River flood basalts provided a significant amount of the unradiogenic Os required to produce the middle Miocene minimum.

  10. Atmospheric Pb isotopic composition and trace metal concentration as revealed by epiphytic lichens:. an investigation related to two altitudinal sections in Eastern France

    Doucet, F. J.; Carignan, J.

    During Fall 1996, epiphytic lichens were collected along altitudinal sections in two areas of France (the Vosges mountains in the North-East, and the Alps, in Haute-Savoie) in order to verify any geographic distribution of atmospheric metals on a small scale. These lichens have various Pb isotopic compositions ( 206Pb/ 207Pb=1.126-1.147) which are correlated with the altitude of sampling. Lichens sampled near valleys display isotopic ratios significantly less radiogenic than those sampled at several hundred to thousand meters of altitude. In the Vosges sections, Pb concentrations and isotopic compositions of lichens may be used to define three zones: (1) valley: Pb-rich and non-radiogenic ratios, (2) transition: low-Pb and intermediate isotopic compositions, (3) mountain: heterogeneous Pb concentrations but more radiogenic and homogeneous Pb isotopic composition. Other metals (Zn, Cu, Cd, As), when normalised one to another, are not fractionated between these zones and display homogeneous relative abundance along the altitudinal sections of both sites. Variation of 206Pb/ 207Pb ratios with altitude is interpreted in terms of mixing of at least two pollution sources: one being the petrol (leaded and/or unleaded) combustion, and the other being of industrial origin. The latter is characterised by a more radiogenic isotopic composition. The Pb isotopic composition of flue gas residues from different municipal solid waste combustors in the Rhine valley and in other areas of France would suggest that these plants might be an important source of industrial Pb in the atmosphere. If the average industrial Pb in France has a 206Pb/ 207Pb close to 1.15, between 60 and 80% of the total Pb in lichens from the Rhine valley would come from gasoline combustion, whereas 85-90% of the Pb would have an industrial origin in lichens from higher altitude in the Vosges mountains. Although lichens from the Alps were collected at higher altitude, the percentage of industrial Pb for these

  11. Heavy ion isotope resolution with polymer detectors

    Vidal-Quadras Roca, Alejo; Ortega Girón, Manuel; Fernández Moreno, Francisco; Font Garcia, Josep Lluís; Casas Ametller, Montserrat; Baixeras Divar, Carmen; Gonzalo Cestero, Miguel


    The heavy ion mass resolution power of polymer detectors Lexan and cellulose nitrate is systematically studied both for accelerator and for cosmic ions. It is concluded that a satisfactory isotopic discrimination, better than 1 u, is hardly attainable with these detectors. Peer Reviewed

  12. Stable isotope studies

    Ishida, T.


    The research has been in four general areas: (1) correlation of isotope effects with molecular forces and molecular structures, (2) correlation of zero-point energy and its isotope effects with molecular structure and molecular forces, (3) vapor pressure isotope effects, and (4) fractionation of stable isotopes. 73 refs, 38 figs, 29 tabs.

  13. Application of lead and strontium isotope ratio measurements for the origin assessment of uranium ore concentrates.

    Varga, Zsolt; Wallenius, Maria; Mayer, Klaus; Keegan, Elizabeth; Millet, Sylvain


    Lead and strontium isotope ratios were used for the origin assessment of uranium ore concentrates (yellow cakes) for nuclear forensic purposes. A simple and low-background sample preparation method was developed for the simultaneous separation of the analytes followed by the measurement of the isotope ratios by multicollector inductively coupled plasma mass spectrometry (MC-ICPMS). The lead isotopic composition of the ore concentrates suggests applicability for the verification of the source of the nuclear material and by the use of the radiogenic (207)Pb/(206)Pb ratio the age of the raw ore material can be calculated. However, during data interpretation, the relatively high variation of the lead isotopic composition within the mine site and the generally high contribution of natural lead as technological contamination have to be carefully taken into account. The (87)Sr/(86)Sr isotope ratio is less prone to the variation within one mine site and less affected by the production process, thus it was found to be a more purposeful indicator for the origin assessment and source verification than the lead. The lead and strontium isotope ratios measured and the methodology developed provide information on the initial raw uranium ore used, and thus they can be used for source attribution of the uranium ore concentrates.

  14. Geochemical and Strontium Isotope Characterization of Produced Waters from Marcellus Shale Natural Gas Extraction

    Elizabeth C. Chapman,† Rosemary C. Capo,† Brian W. Stewart,*,† Carl S. Kirby,‡ Richard W. Hammack,§


    Extraction of natural gas by hydraulic fracturing of the Middle Devonian Marcellus Shale, a major gas-bearing unit in the Appalachian Basin, results in significant quantities of produced water containing high total dissolved solids (TDS). We carried out a strontium (Sr) isotope investigation to determine the utility of Sr isotopes in identifying and quantifying the interaction of Marcellus Formation produced waters with other waters in the Appalachian Basin in the event of an accidental release, and to provide information about the source of the dissolved solids. Strontium isotopic ratios of Marcellus produced waters collected over a geographic range of ∼375 km from southwestern to northeastern Pennsylvania define a relatively narrow set of values (εSr SW = +13.8 to +41.6, where εSr SW is the deviation of the 87Sr/86Sr ratio from that of seawater in parts per 104); this isotopic range falls above that of Middle Devonian seawater, and is distinct from most western Pennsylvania acid mine drainage and Upper Devonian Venango Group oil and gas brines. The uniformity of the isotope ratios suggests a basin-wide source of dissolved solids with a component that is more radiogenic than seawater. Mixing models indicate that Sr isotope ratios can be used to sensitively differentiate between Marcellus Formation produced water and other potential sources of TDS into ground or surface waters.

  15. Barren Miocene granitoids in the Central Andean metallogenic belt, Chile: Geochemistry and Nd-Hf and U-Pb isotope systematics Granitoides estériles del Mioceno en la franja metalogénica de los Andes Centrales, Chile: geoquímica e isotopía de Nd-Hf y U-Pb

    Katja Deckart


    Full Text Available Four Middle-to-Late Miocene barren plutonic complexes that occur between the giant porphyry copper deposits of the central Chilean Andes were selected for U-Pb LA-ICPMS geochronology and Hf-isotope systematics on single zircon grains. Major and trace elements and Sr-Nd-Hf isotope whole rock geochemical studies were under-taken to compare with slightly younger or coeval barren and fertile intrusive rocks between 32° and 34°S. The studied granitoids yield resolvable crystallization ages of 11.3±0.1 Ma (Cerro Mesón Alto massif, 10.3±0.2 Ma (La Gloria pluton, 14.9±0.2 Ma/14.9±0.1 Ma (Yerba Loca stock and 11.2±0.1 Ma/14.7±0.1 Ma (San Francisco Batholith. Major and trace elements discard an adakitic signature as suggested for coeval porphyric intrusions at 32°S, slightly younger mineralized porphyries at Río Blanco-Los Bronces deposit and other Cenozoic adakites. Volcanic host rocks are less fractionated than the intrusive rock units. The same observation can be made for the unmineralized northern plutons compared to the southern ones. Initial Sr-Nd isotope data show insignificant variation (0.703761-0.704118 and 0.512758-0.512882, plotting in the mantle array. Trace element enrichment can be explained by addition of subducted-slab fluids and/or terrigenous sediments to the mantle wedge prior to and/or slight crustal input during magma ascent. Zircon grains separated from these barren intrusives share a similar initial εHf i-data variation for the younger age group (10-12 Ma; 7.04-9.54 and show a more scattered range for the older one (14-15 Ma; 8.50-15.34; both sets plot between the DM and CLTUR evolution lines. There is evidence that magma evolution was slightly distinct through time from older to younger barren magmatism, compared to a few fertile porphyritic rocks from Río Blanco-Los Bronces porphyry copper deposit. It is suggested that chronological inconsistencies within these complexes might be related to differential shortening

  16. Stable C, O and clumped isotope systematics and 14C geochronology of carbonates from the Quaternary Chewaucan closed-basin lake system, Great Basin, USA: Implications for paleoenvironmental reconstructions using carbonates

    Hudson, Adam M.; Quade, Jay; Ali, Guleed; Boyle, Douglas; Bassett, Scott; Huntington, Katharine W.; De los Santos, Marie G.; Cohen, Andrew S.; Lin, Ke; Wang, Xiangfeng


    Isotopic compositions of lacustrine carbonates are commonly used for dating and paleoenvironmental reconstructions. Here we use carbonate δ13C and δ18O, clumped (Δ47), and 14C compositions to better understand the carbonate isotope system in closed-basin lakes and trace the paleohydrologic and temperature evolution in the Chewaucan closed-basin lake system, northern Great Basin, USA, over the Last Glacial/Holocene transition. We focus on shorezone tufas to establish that they form in isotopic equilibrium with lake water and DIC, they can be dated reliably using 14C, and their clumped isotope composition can be used to reconstruct past lake temperature. Calculations of the DIC budget and reservoir age for the lake indicate residence time is short, and dominated by exchange with atmospheric CO2 at all past lake levels. Modern lake DIC and shorezone tufas yield δ13C and 14C values consistent with isotopic equilibrium with recent fossil fuel and bomb-influenced atmospheric CO2, supporting these calculations. δ13C values of fossil tufas are also consistent with isotopic equilibrium with pre-industrial atmospheric CO2 at all shoreline elevations. This indicates that the 14C reservoir effect for this material is negligible. Clumped isotope (Δ47) results indicate shorezone tufas record mean annual lake temperature. Modern (average 13 ± 2 °C) and 18 ka BP-age tufas (average 6 ± 2 °C) have significantly different temperatures consistent with mean annual temperature lowering of 7 ± 3 °C (1 SE) under full glacial conditions. For shorezone tufas and other lake carbonates, including spring mounds, mollusk shells, and ostracod tests, overall δ13C and δ18O values co-vary according to the relative contribution of spring and lacustrine end member DIC and water compositions in the drainage system, but specific isotope values depend strongly upon sample context and are not well correlated with past lake depth. This contrasts with the interpretation that carbonate

  17. Stable C, O and clumped isotope systematics and 14C geochronology of carbonates from the Quaternary Chewaucan closed-basin lake system, Great Basin, USA: Implications for paleoenvironmental reconstructions using carbonates

    Hudson, Adam; Quade, Jay; Ali, Guleed; Boyle, Douglas P.; Bassett, Scott; Huntington, Katharine W.; De los Santos, Marie G.; Cohen, Andrew S.; Lin, Ke; Wang, Xiangfeng


    Isotopic compositions of lacustrine carbonates are commonly used for dating and paleoenvironmental reconstructions. Here we use carbonate δ13C and δ18O, clumped (Δ47), and 14C compositions to better understand the carbonate isotope system in closed-basin lakes and trace the paleohydrologic and temperature evolution in the Chewaucan closed-basin lake system, northern Great Basin, USA, over the Last Glacial/Holocene transition. We focus on shorezone tufas to establish that they form in isotopic equilibrium with lake water and DIC, they can be dated reliably using 14C, and their clumped isotope composition can be used to reconstruct past lake temperature. Calculations of the DIC budget and reservoir age for the lake indicate residence time is short, and dominated by exchange with atmospheric CO2 at all past lake levels. Modern lake DIC and shorezone tufas yield δ13C and 14C values consistent with isotopic equilibrium with recent fossil fuel and bomb-influenced atmospheric CO2, supporting these calculations. δ13C values of fossil tufas are also consistent with isotopic equilibrium with pre-industrial atmospheric CO2 at all shoreline elevations. This indicates that the 14C reservoir effect for this material is negligible. Clumped isotope (Δ47) results indicate shorezone tufas record mean annual lake temperature. Modern (average 13 ± 2 °C) and 18 ka BP-age tufas (average 6 ± 2 °C) have significantly different temperatures consistent with mean annual temperature lowering of 7 ± 3 °C (1 SE) under full glacial conditions. For shorezone tufas and other lake carbonates, including spring mounds, mollusk shells, and ostracod tests, overall δ13C and δ18O values co-vary according to the relative contribution of spring and lacustrine end member DIC and water compositions in the drainage system, but specific isotope values depend strongly upon sample context and are not well correlated with past lake depth. This contrasts with the interpretation that carbonate

  18. The anomalous quadrupole collectivity in Te isotopes

    Qi, Chong


    We present systematic calculations on the spectroscopy and transition properties of even-even Te isotopes by using the large-scale configuration interaction shell model approach with a realistic interaction. These nuclei are of particular interest since their yrast spectra show a vibrational-like equally-spaced pattern but the few known E2 transitions show anomalous rotational-like behavior, which cannot be reproduced by collective models. Our calculations reproduce well the equally-spaced spectra of those isotopes as well as the constant behavior of the $B(E2)$ values in $^{114}$Te. The calculated $B(E2)$ values for neutron-deficient and heavier Te isotopes show contrasting different behaviors along the yrast line. The $B(E2)$ of light isotopes can exhibit a nearly constant bevavior upto high spins. We show that this is related to the enhanced neutron-proton correlation when approaching $N=50$.

  19. Development of proliferation resistant isotope separation technology

    Jeong, Doyoung; Ko, Kwanghoon; Kim, Taeksoo; Park, Hyunmin; Lim, Gwon; Cha, Yongho; Han, Jaemin; Baik, Sunghoon; Cha, Hyungki


    This project was accomplished with an aim of establishing the industrial facilities for isotope separation in Korea. The experiment for the measurement of neutrino mass that has been an issue in physics, needs very much of enriched calcium-48 isotope. However, calcium-48 isotope can be produced only by the electro-magnetic method and, thus, its price is very expensive. Therefore, we expect that ALSIS can replace the electro-magnetic method for calcium-48 isotope production. In this research stage, the research was advanced systematically with core technologies, such as atomic vapor production, the measurement of vapor characteristics and stable and powerful laser development. These researches will be the basis of the next research stages. In addition, the international research trends and cooperation results are reported in this report.

  20. 231Pa systematics in postglacial volcanic rocks from Iceland

    Turner, Simon; Kokfelt, Thomas; Hoernle, Kaj; Lundstrom, Craig; Hauff, Folkmar


    Several recent studies have highlighted the potential of combined 238U-230Th and 235U-231Pa systematics to constrain upwelling rates and the role of recycled mafic lithologies in mantle plume-derived basalts. Accordingly, we present measurements of the 231Pa concentrations from 26 mafic volcanic rocks from Iceland, including off-axis basalts from the Snaefellsnes Peninsula, to complement previously published 238U-230Th-226Ra data. 231Pa concentrations vary from 27 to 624 fg/g and (231Pa/235U) ratios from 1.12 to 2.11 with the exception of one anomalous sample from the Southeast Rift which has a 231Pa deficit with (231Pa/235U) = 0.86. An important new result is that basalts from the Southeast Rift and the Snaefellsnes Peninsula define a trend at relatively low (231Pa/235U) for a given (230Th/238U) ratio. Many of the remaining samples fall in or around the global field for ocean island basalts but those from the Mid-Iceland Belt and the Southwest Rift/Reykjanes Peninsula extend to higher (231Pa/235U) ratios at a given (230Th/238U), similar to mid-ocean ridge basalts. In principle, these lavas could result from melting of peridotite at lower pressures. However, there is no reason to suspect that the Mid-Iceland Belt and the Southwest Rift lavas reflect shallower melting than elsewhere in Iceland. In our preferred model, these lavas reflect melting of garnet peridotite whereas those from the Southeast Rift and the Snaefellsnes Peninsula contain a significant contribution (up to 20%) of melt from garnet pyroxenite. This is consistent with incompatible trace element and radiogenic isotope evidence for recycled oceanic crust in these lavas. There is increasing agreement that the displacement of ocean island basalts to lower (231Pa/235U) ratios at a given (230Th/238U), compared to mid-ocean ridge basalts, reflects the role of recycled mafic lithologies such as garnet pyroxenite as well as higher average pressures of melting. It now seems likely that this interpretation may

  1. New evaluation of alpha decay half-life of {sup 190}Pt isotope for the Pt-Os dating system

    Tavares, O.A.P.; Medeiros, E.L. [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil); Terranova, M.L. [Universita degli Studi di Roma Tor Vergata (Italy). Dipt. di Scienze e Tecnologie Chimiche; Istituto Nazionale di Fisica Nucleare (INFN), Rome (Italy)


    A semiempirical model based on the quantum mechanical tunnelling mechanism of alpha emission from nuclei has been used to evaluate the half-life of the Pt isotopes. For the important naturally occurring {sup 190}Pt isotope, the radiogenic parent in the {sup 190} Pt {yields} {sup 186}Os dating system, the model yielded a half-life value of (3.7{+-} 0.3) versus 10{sup 11} y. This is comparable to (3.2{+-}0.1) versus 10{sup 11} y which was obtained in the last direct counting experiment to measure the alpha activity of {sup 190}Pt (Tavares and Terranova, Rad. Measurem. 27 (1997) 19). A literature survey of available alpha decay half-life values for {sup 190}Pt isotope is also reported. The significant discrepancies found between data obtained by direct counting, indirect geological methods and different calculation models are analysed and discussed. (author)

  2. Lead and neodymium isotopic results from metabasalts of the Haveri Formation, southern Finland: evidence for Palaeoproterozoic enriched mantle

    Vaasjoki, M.


    Full Text Available Tholeiitic metabasalts and coexisting sulphides have been analysed for their Pb and Nd isotopic compositions from the Proterozoic Haveri Formation, which forms the basal unit of the Tampere Schist Belt in southern Finland. Ten whole rock samples analysed for Pb isotopes form a sublinear array which yields rather uncertain age estimates in the 1900-2000 Ma range and lies on the 207Pb/204Pb vs. 206Pb/204Pb diagram well below the average global lead evolution curve. The initial lead isotopic composition inferred from the whole rock data and measured on chalcopyrite is the least radiogenic obtained from the Svecofennian domain, and precludes involvement of old upper crustal material in basalt genesis. This together with the geochemical composition and initial eNd (1900 of +0.5±0.6 suggest that the Haveri mafic metavolcanic rocks were not derived from convective MORB-type mantle. The source was rather a mantle, which had been enriched in LREE for a considerable time period. Some chalcopyrite trace leads plot close to the whole rock array while others lie above it. This is interpreted as indicating two distinct mineralisation processes. The primary and major process involved lead which was cogenetic with the basalts, while the second mineralising fluid introduced radiogenic (high 207Pb upper crustal lead scavenged from the adjacent sedimentary rocks. The least radiogenic leads at Haveri and in the Outokumpu ophiolite complex some 300 km NE are similar and the two occurrences can be coeval. The preservation of original mantle material at Haveri may be interpreted as suggesting that continental crust had formed in the Tampere area 1900-2000 Ma ago.

  3. High-spin study of {sup 128}Ce and systematics of quasiparticle pair alignment[21.10.Re; 27.60+q; 23.20.Lv.; Nuclear reactions: 32S+100Mo at 155, 160 MeV; Enriched targets; Euroball spectrometer of Compton-suppressed HPGe detectors; Measured E{gamma}, I{gamma}; Comparison of alignment properties with neighbouring isotopes and isotones; Comparison with Woods-Saxon cranking calculations

    Paul, E.S.; Bednarczyk, P.; Boston, A.J.; Chiara, C.J.; Foin, C.; Fossan, D.B.; Genevey, J.; Gizon, A.; Gizon, J.; Jenkins, D.G.; Kelsall, N.; Kintz, N.; Koike, T.; LaFosse, D.R.; Nolan, P.J.; Nyako, B.M.; Parry, C.M.; Sampson, J.A.; Semple, A.T.; Starosta, K.; Timar, J.; Wadsworth, R.; Wilson, A.N.; Zolnai, L


    High-spin states have been studied in {sup 128}Ce, produced in the {sup 100}Mo({sup 32}S,4n) reaction, using the EUROBALL {gamma}-ray spectrometer. A quadruples analysis ({gamma}{sup 4}) of the data has extended several bands to high spin. Systematics of quasiparticle alignments in cerium isotopes and relevant isotonic chains are discussed and compared to Woods-Saxon cranking calculations.

  4. High-spin study of sup 1 sup 2 sup 8 Ce and systematics of quasiparticle pair alignment 21.10.Re; 27.60+q; 23.20.Lv.; Nuclear reactions: 32S+100Mo at 155, 160 MeV; Enriched targets; Euroball spectrometer of Compton-suppressed HPGe detectors; Measured E gamma, I gamma; Comparison of alignment properties with neighbouring isotopes and isotones; Comparison with Woods-Saxon cranking calculations

    Paul, E S; Boston, A J; Chiara, C J; Foin, C; Fossan, D B; Genevey, J; Gizon, A; Gizon, J; Jenkins, D G; Kelsall, N; Kintz, N; Koike, T; Lafosse, D R; Nolan, P J; Nyakó, B M; Parry, C M; Sampson, J A; Semple, A T; Starosta, K; Timar, J; Wadsworth, R; Wilson, A N; Zolnai, L


    High-spin states have been studied in sup 1 sup 2 sup 8 Ce, produced in the sup 1 sup 0 sup 0 Mo( sup 3 sup 2 S,4n) reaction, using the EUROBALL gamma-ray spectrometer. A quadruples analysis (gamma sup 4) of the data has extended several bands to high spin. Systematics of quasiparticle alignments in cerium isotopes and relevant isotonic chains are discussed and compared to Woods-Saxon cranking calculations.

  5. Anthropogenic influences on Pb/Al and lead isotope signature in annually layered Holocene Maar lake sediments

    Schettler, G.; Romer, R.L. [GeoForschungsZentrum Potsdam, Telegrafenberg, D-14473 Potsdam (Germany)


    Annually laminated sediments from two Maar lakes in the West Eifel volcanic field (Germany) show anomalously high Pb within sections deposited during the first centuries A.D. exceeding the local geological background 8.5-fold in Lake Meerfelder Maar (MFM) and 4-fold in Lake Schalkenmehrener Maar (SMM). These Pb anomalies are associated with a distinct shift in the Pb isotope signature to less radiogenic compositions. The excess Pb causing the anomaly has the same isotopic composition as galena deposits 60 km to the NW of the Maar lakes. It is suggested that this component was transported airborne into the Maar lakes and originates from regional Roman Pb refinement and cupellation of argentiferous Pb. Varve chronostratigraphy of correlated cores indicates that significant Roman Pb input lasted for about 230 a. SMM does not get fluviatile input. Its sedimentary record is more sensitive to variations in airborne input than that of MFM, which had an inflow. SMM sediment sections deposited during periods of low soil erosion (early Holocene, Dark Ages) with comparably high Pb/Al values also show little radiogenic Pb. This is caused by airborne minerogenic matter from a geochemically and isotopically distinct remote source that becomes apparent only in sedimentation periods of very restricted local allochthonous input. (Copyright (c) 1998 Elsevier Science B.V., Amsterdam. All rights reserved.)

  6. Early Solar System Alkali Fractionation Events Recorded by K-Ca Isotopes in the Yamato-74442 LL-Chondritic Breccia

    Tatsunori, T.; Misawa, K.; Okano, O.; Shih, C.-Y.; Nyquist, L. E.; Simon, J. I.; Tappa, M. J.; Yoneda, S.


    Radiogenic ingrowth of Ca-40 due to decay of K-40 occurred early in the solar system history causing the Ca-40 abundance to vary within different early-former reservoirs. Marshall and DePaolo ] demonstrated that the K-40/Ca-40 decay system could be a useful radiogenic tracer for studies of terrestrial rocks. Shih et al. [3,4] determined 40K/40Ca ages of lunar granitic rock fragments and discussed the chemical characteristics of their source materials. Recently, Yokoyama et al. [5] showed the application of the K-40/Ca-40 chronometer for high K/Ca materials in ordinary chondrites (OCs). High-precision calcium isotopic data are needed to constrain mixing processes among early solar system materials and the time of planetesimal formation. To better constrain the solar system calcium isotopic compositions among astromaterials, we have determined the calcium isotopic compositions of OCs and an angrite. We further estimated a source K/Ca ratio for alkali-rich fragments in a chondritic breccia using the estimated solar system initial Ca-40/Ca-44.

  7. Sr isotopes in the Orgueil CI meteorite: Chronology of early solar system hydrothermal activity

    J D Macdougall


    New Sr isotopic analyses and calculated formation ages of carbonates from the Orgueil CI meteorite are reported. Among the samples analyzed in this work, dolomites give the youngest formation ages and may have been deposited intermittently starting near the time of parent body formation and continuing for at least 30 Ma. The Sr isotope data also suggest that breunnerites (Fe-Mn-Mg carbonates) crystallized after dolomite formation. Leaching experiments on bulk meteorite samples provide evidence for a very mobile, water soluble Sr reservoir in Orgueil that is characterized by extremely radiogenic Sr (87Sr/86Sr ≈ 0.81- 0.82). This unsupported Sr reflects recent element redistribution, possibly at the time of parent body breakup recorded by the ∼10 Ma exposure age of Orgueil. The carbonate data in particular corroborate earlier indications that hydrothermal processes were among the earliest events to affect the CI parent body.

  8. Iron isotope tracing of mantle heterogeneity within the source regions of oceanic basalts

    Williams, Helen M.; Bizimis, Michael


    Mineralogical variations in the Earth's mantle and the relative proportions of peridotitic versus enriched and potentially crustally-derived pyroxenitic domains within the mantle have important implications for mantle dynamics, magma generation, and the recycling of surface material back into the mantle. Here we present iron (Fe) stable isotope data (δ57Fe, deviation in 57Fe/54Fe from the IRMM-014 standard in parts per thousand) for peridotite and garnet-pyroxenite xenoliths from Oahu, Hawaii and explore Fe isotopes as tracer of both peridotitic and pyroxenitic components in the source regions of oceanic basalts. The pyroxenites have δ57Fe values that are heavy (0.10 to 0.27‰) relative to values for mid-ocean ridge and ocean island basalts (MORB; OIB; δFe57∼0.16‰) and the primitive mantle (PM; δFe57∼0.04‰). Pyroxenite δ57Fe values are positively correlated with bulk pyroxenite titanium and heavy rare earth element (REE) abundances, which can be interpreted in terms of stable isotope fractionation during magmatic differentiation and pyroxene cumulate formation. In contrast, the peridotites have light δ57Fe values (-0.34 to 0.14‰) that correlate negatively with degree of melt depletion and radiogenic hafnium isotopes, with the most depleted samples possessing the most radiogenic Hf isotope compositions and lightest δ57Fe values. While these correlations are broadly consistent with a scenario of Fe isotope fractionation during partial melting, where isotopically heavy Fe is extracted into the melt phase, leaving behind low-δ57Fe peridotite residues, the extent of isotopic variation is far greater than predicted by partial melting models. One possibility is derivation of the samples from a heterogeneous source containing both light-δ57Fe (relative to PM) and heavy-δ57Fe components. While pyroxenite is a viable explanation for the heavy-δ57Fe component, the origin of the depleted light-δ57Fe component is more difficult to explain, as melting

  9. Rb–Sr and Sm–Nd isotope systematics and geochemical studies on metavolcanic rocks from Peddavura greenstone belt: Evidence for presence of Mesoarchean continental crust in easternmost part of Dharwar Craton, India

    M Rajamanickam; S Balakrishnan; R Bhutani


    Linear, north–south trending Peddavura greenstone belt occurs in easternmost part of the Dharwar Craton. It consists of pillowed basalts, basaltic andesites, andesites (BBA) and rhyolites interlayered with ferruginous chert that were formed under submarine condition. Rhyolites were divided into type-I and II based on their REE abundances and HREE fractionation. Rb–Sr and Sm–Nd isotope studies were carried out on the rock types to understand the evolution of the Dharwar Craton. Due to source heterogeneity Sm–Nd isotope system has not yielded any precise age. Rb–Sr whole-rock isochron age of 2551 ± 19 (MSWD = 1.16) Ma for BBA group could represent time of seafloor metamorphism after the formation of basaltic rocks. Magmas representing BBA group of samples do not show evidence for crustal contamination while magmas representing type-II rhyolites had undergone variable extents of assimilation of Mesoarchean continental crust (< 3.3 Ga) as evident from their initial Nd isotope values. Trace element and Nd isotope characteristics of type I rhyolites are consistent with model of generation of their magmas by partial melting of mixed sources consisting of basalt and oceanic sediments with continental crustal components. Thus this study shows evidence for presence of Mesoarchean continental crust in Peddavura area in eastern part of Dharwar Craton.

  10. Helium isotope data from the Goldfield epithermal system, Nevada: Evidence for volatile input from a primitive mantle source during ore formation

    Hofstra, A. H.; Manning, A. H.


    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

  11. Origin and fate of sulfide liquids in hotspot volcanism (La Réunion): Pb isotope constraints from residual Fe-Cu oxides

    Vlastélic, I.; Gannoun, A.; Di Muro, A.; Gurioli, L.; Bachèlery, P.; Henot, J. M.


    Immiscible sulfide liquids in basaltic magmas play an important role in trace metal transport and the sulfur budget of volcanic eruptions. However, sulfides are transient phases, whose origin and fate are poorly constrained. We address these issues by analyzing sulfide destabilization products preserved in lavas from La Réunion Island. Iron oxide globules and coatings, typically 20-80 μm in size, were found to occur in vesicles of differentiated lavas from Piton des Neiges, and recent pumice samples from Piton de la Fournaise. Field and mineralogical evidence indicates that the iron oxides are syn-eruptive phases not resulting from hydrothermal processes. Samples were first studied by Scanning Electron Microscopy. The globules were separated, whereas the smaller spherules and coatings were concentrated by magnetic sorting and acid leaching, and samples were processed through wet chemistry. The Fe oxide phases comprise 49-74 wt.% Fe, 26-40 wt.% O, and up to 6 wt.% Cu, 811 ppm Ni, 140 ppm Bi, and 8.5 ppm Pb. Compared to the host lava, Cu, Ni, and Bi are enriched by a factor of 101-103. Systematic Pb isotope disequilibrium (between 500 ppm and 2.9% for 206Pb/204Pb) exists between Fe oxides and host rocks, with Fe oxides generally displaying less radiogenic ratios. Unradiogenic Pb is a typical signature of sulfide, which tends to concentrate Pb, but not its parent elements U and Th. Thus, both the chemical and isotopic compositions of the vesicle-hosted Fe oxides suggest that they are more or less direct products of the destabilization of immiscible sulfide liquids. Although Pb dominantly partitions into the gas phase during sulfide breakdown, the original Pb isotope signature of sulfide is preserved in the residual oxide. The composition estimated for the parent sulfides (206Pb/204Pb = 18.20-18.77, 207Pb/204Pb = 15.575, and 208Pb/204Pb = 38.2-38.8) precludes a genetic link with the La Réunion plume, and suggests a lithospheric or crustal origin. It is estimated

  12. Palaeoproterozoic continental arc magmatism, and Neoproterozoic metamorphism in the Aravalli-Delhi orogenic belt, NW India: New constraints from in situ zircon U-Pb-Hf isotope systematics, monazite dating and whole-rock geochemistry

    Kaur, Parampreet; Zeh, Armin; Chaudhri, Naveen


    Presently, the extent, origin and petrogenesis of late Palaeoproterozoic (ca. 1.85 Ga) magmatism in the north-central Aravalli-Delhi orogenic belt, NW India and subsequent metamorphic overprints are poorly constrained. Results of new in situ zircon U-Pb-Hf isotope analyses in combination with whole-rock elemental and isotopic data provide the first hard evidence that granitoid magmatism occurred in a continental magmatic arc setting between 1.86 and 1.81 Ga. The Hf-Nd model ages of 3.0-2.6 Ga and inherited zircon grains of 3.3-2.5 Ga indicate abundant reworking of Archaean crust. Flat HREE patterns with negative Eu anomalies furthermore reveal that the granitoids were generated from garnet-free and plagioclase-rich sources at shallow depths. Significant isotope variation among granitoid samples (εHft = -3.7 to -9.0; εNdt = -4.8 to -7.9) indicate that the reworked Archaean crust was not completely homogenised during the Palaeoproterozoic. This is best reflected by zircon Hf-isotope variation of ca. 9.5 epsilon units within the oldest granitoid sample. Zircon grains from this sample define three discrete Hf-isotope groups at εHf1.86Ga = -8.9, -4.8 and -1.6. These are interpreted to result from mixing of zircon-saturated magmas derived from three distinct sources within the crust prior to solidification. A monazite U-Pb isochron age of 868 ± 4 Ma from one of the granitoid samples furthermore indicates that the Aravalli fold belt was affected by an important post-magmatic overprint, perhaps related to the widespread metasomatic, granulite metamorphic and/or magmatic events during the same time span.

  13. Os and U-Th isotope signatures of arc magmatism near Mount Mazama, Crater Lake, Oregon

    Ankney, Meagan E.; Shirey, Steven B.; Hart, Garret L.; Bacon, Charles R.; Johnson, Clark M.


    Interaction of mantle melts with the continental crust can have significant effects on the composition of the resulting melts as well as on the crust itself, and tracing this interaction is key to our understanding of arc magmatism. Lava flows and pyroclastic deposits erupted from ∼50 to 7.7 ka at Mt. Mazama (Crater Lake, Oregon) were analyzed for their Re/Os and U-Th isotopic compositions. Mafic lavas from monogenetic vents around Mt. Mazama that erupted during the buildup to its climactic eruption have lower 187Os/188Os ratios (0.1394 to 0.1956) and high 230Th excess ((230Th/238U)0 of 1.180 to 1.302), whereas dacites and rhyodacites tend to have higher 187Os/188Os ratios (0.2292 to 0.2788) and significant 238U excess ((230Th/238U)0 of 0.975 to 0.989). The less radiogenic Os isotope compositions of the mafic lavas can be modeled by assimilation of young (∼2.5 to 7 Ma), mafic lower crust that was modified during regional extension, whereas the more radiogenic Os isotope compositions of the dacites and rhyodacites can be attributed to assimilation of older (∼10 to 16 Ma), mid to upper crust that acquired its composition during an earlier period of Cascade magmatism. Production of Th excesses in the lower crust requires very young garnet formation accompanying dehydration melting in the lower crust at less than a few 100 ka by heat from recent basaltic magma injection. The results from this study suggest that the combination of Os and Th isotopes may be used to provide insights into the timescales of evolution of the continental crust in arc settings, as well as the influence of the crust on erupted magmas, and suggest a link between the age and composition of the lower and upper crust to regional tectonic extension and/or earlier Cascade magmatism.

  14. Nd-isotope evidence for the distal provenance of the historical (c. Gabon (Western Africa)

    Thiéblemont, D.; Guerrot, C.; Négrel, Ph.; Braucher, R.; Bourlès, D. L.; Thiéblemont, R.


    Surficial formations in Gabon, as well as in other places of western Central Africa include a ubiquitous, homogeneous and 1-3 m-thick clayey to sandy lateritic surface cover known as the 'Cover Horizon'. From 14C radiometric dating it has been concluded that the emplacement of this unit was correlative with a major environmental crisis which affected Central Africa c. 3000-2000 years ago. 10Be and Nd-isotopic analyses have been performed to provide new constraints on the age and origin of this layer. Six samples from two depth profiles investigated for 10Be exhibit an almost constant concentration consistent with a very recent deposition age. Nd-isotopic analyses performed on the silt to clay fraction of eleven samples from widely spaced locations over Gabon attest for mildly radiogenic signatures (εNd = -23 to -17) in ten of them, and a slightly radiogenic signature (εNd = -9) in one sample. TDM model ages range from 1.6 to 2.6 Ga, and a perfect discrimination is observed between the Nd-isotopic signature of the Cover Horizon and that of the underlying Congo Craton. This makes an aeolian origin as the most probable for the Cover Horizon. The average εNd (c. -20) is however rather unusual for aeolian sediments or aerosols. A possible source of particles is therefore tested by considering the present-day atmospheric flux over Gabon and adjacent regions. Combined atmospheric modeling and Nd-isotopes leads to the conclusion that the fine fraction of the Cover Horizon could have originated from the northern part of the Namib desert.

  15. Radioactivity and radiogenic heat production in the oil field of the Reconcavo Basin; Radioatividade e geracao de calor radiogenico em pocos petroliferos na Bacia do Reconcavo

    Alves Junior, Paulo B.; Argollo, Roberto M. de [Universidade Federal da Bahia (UFBA), Salvador, BA (Brazil). Centro de Pesquisa em Geofisica e Geologia


    The production of radiogenic heat in the terrestrial crust is due mainly to U, Th and K presents in the rocks. In this work, we use the gamma-ray spectrometry technique to determine the contents of these elements in drill cuttings and obtaining profiles of heat production rates in oils wells of the Reconcavo basin. In the total, we measure 640 samples of drill cuttings from wells FFL-1 and MGP-34 ceded by PETROBRAS. The thorium contents vary from 1.6 to 25.5 ppm, the uranium contents varied from 0.5 to 5.82 ppm, the potassium samples varied from 0.05 to 2.25 % and the production rates of radiogenic heat varied among 0.50 to 10.85 10{sup -4} {mu}W kg{sup -1}. With the profiles heat production rates obtained, a correlation was verified among these rates and the lithologies at wells FFL-1 and MGP-34. These values will be used in the correlation between these samples at wells and the sample collected at blooming. (author)

  16. Calcium isotopes in wine

    Holmden, C. E.


    The δ 44/40Ca values of bottled wine vary between -0.76% to -1.55% on the seawater scale and correlate weakly with inverse Ca concentration and Mg/Ca ratio, such that the lowest δ 44/40Ca values have the highest Ca concentrations and lowest Mg/Ca ratios. The correlation is notable in the sense that the measured wines include both whites and reds sampled from different wine growing regions of the world, and cover a wide range of quality. Trends among the data yield clues regarding the cause of the observed isotopic fractionation. White wines, and wines generally perceived to be of lower quality, have lower δ 44/40Ca values compared to red wines and wines of generally perceived higher quality. Quality was assessed qualitatively through sensory evaluation, price, and scores assigned by critics. The relationship between δ 44/40Ca and wine quality was most apparent when comparing wines of one varietal from one producer from the same growing region. In the vineyard, wine quality is related to factors such as the tonnage of the crop and the ripeness of the grapes at the time of harvesting, the thickness of the skins for reds, the age of the vines, as well as the place where the grapes were grown (terroir). Quality is also influenced by winemaking practices such as fermentation temperature, duration of skin contact, and barrel ageing. Accordingly, the relationship between δ 44/40Ca and wine quality may originate during grape ripening in the vineyard or during winemaking in the cellar. We tested the grape ripening hypothesis using Merlot grapes sampled from a vineyard in the Okanagan, British Columbia, using sugar content (degrees Brix) as an indicator of ripeness. The grapes were separated into pulp, skin, and pip fractions and were analyzed separately. Thus far, there is no clear evidence for a systematic change in δ 44/40Ca values associated with progressive ripening of grapes in the vineyard. On the day of harvesting, the δ 44/40Ca value of juice squeezed from

  17. Helium Isotopic Ratios of Core Samples from IODP Exp. 319 (NanTroSEIZE Stage 2)

    Horiguchi, K.; Matsuda, J.; Wiersberg, T.; Shimo, Y.; Tamura, H.; Kumagai, H.; Suzuki, K.; Saito, S.; Kinoshita, M.; Araki, E.; Byrne, T.; McNeill, L. C.; Saffer, D.; Takahashi, K.; Eguchi, N. O.; Toczko, S.


    IODP Exp.319 of Nankai Trough Seismogenic Zone Drilling Program Stage 2 started at May 2009. Various advanced technologies including first riser-based scientific ocean drilling were carried out at this cruise. The Hole C0009A (Site C0009/ Hole A) recovered cutting and partly core samples from 703.9-1604 mbsf by riser-drilling. The core samples were collected between the depth of 1510.5 and 1593.9 mbsf. Here we report preliminary helium isotopic ratios of these cores. We collected three types of samples for our study: (1) gas of cores, (2) whole round cores (100 cc) and (3) small whole round cores (10 cc). The gas samples were taken immediately after the core recovery. The gas samples were collected from each core section by using a syringe, and it was transferred to the glass bottle using the water displacement method. The glass bottle was made by Pyrex glass with vacuum valve at each end. We collected two sizes of whole round core samples (100 cc and 10 cc) The 100 cc cores were collected from the bottom and top sections of coring. The 10 cc cores were taken from the other sections. The outer parts of these samples were carefully removed to avoid contaminations from drilling fluid. After the removal of contamination, we immediately stored the 100 cc samples into vacuum container and 10 cc samples into plastic bag under a dry condition, respectively. The gas samples were measured for helium isotopic ratios. The noble gas measurement was carried out at Osaka University by using VG5400 mass spectrometer. We measured helium isotopic ratio and 4He/20Ne ratio. The latter is useful for making correction of the air contamination. The obtained result of helium isotopic ratios shows that the radiogenic helium is prominent in all samples. In addition, the helium isotope ratios show a trend that the ratio at shallower part is slightly higher than that at deeper part. It is conceivable that this trend is due to the larger radiogenic ingrowths at the deeper part. However, the

  18. Major, trace element and isotope geochemistry (Sr-Nd-Pb) of interplinian magmas from Mt. Somma-Vesuvius (Southern Italy)

    Somma, R.; Ayuso, R.A.; de Vivo, B.; Rolandi, G.


    Major, trace element and isotopic (Sr, Nd, Pb) data are reported for representative samples of interplinian (Protohistoric, Ancient Historic and Medieval Formations) activity of Mt. Somma-Vesuvius volcano during the last 3500 years. Tephra and lavas exhibit significant major, trace element and isotopic variations. Integration of these data with those obtained by previous studies on the older Somma suites and on the latest activity, allows to better trace a complete petrological and geochemical evolution of the Mt. Somma-Vesuvius magmatism. Three main groups of rocks are recognized. A first group is older than 12.000 yrs, and includes effusive-explosive activity of Mt. Somma. The second group (8000-2700 yrs B.P.) includes the products emitted by the Ottaviano (8000 yrs. B.P.) and Avellino (3550 yrs B.P.) plinian eruptions and the interplinian activity associated with the Protohistoric Formation. Ancient Historic Formation (79-472 A.D.), Medieval Formation (472-1139 A.D.) and Recent interplinian activity (1631-1944 A.D.) belong to the third group of activity (79-1944 A.D.). The three groups of rocks display distinct positive trends of alkalis vs. silica, which become increasingly steeper with age. In the first group there is an increase in silica and alkalis with time, whereas an opposite tendency is observed in the two younger groups. Systematic variations are also evident among the incompatible (Pb, Zr, Hf, Ta, Th, U, Nb, Rb, Cs, Ba) and compatible elements (Sr, Co, Cr). REE document variable degrees of fractionation, with recent activity displaying higher La/Yb ratios than Medieval and Ancient Historic products with the same degree of evolution. N-MORB normalized multi-element diagrams for interplinian rocks show enrichment in Rb, Th, Nb, Zr and Sm (> *10 N-MORB). Sr isotope ratios are variable, with Protohistoric rocks displaying 87Sr/86Sr= 0.70711-0.70810, Ancient Historic 87Sr/86Sr=0.70665-0.70729, and Medieval 87Sr/86Sr=0.70685-0.70803. Neodymium isotopic

  19. Ocean circulation and freshwater pathways in the Arctic Mediterranean based on a combined Nd isotope, REE and oxygen isotope section across Fram Strait

    Laukert, Georgi; Frank, Martin; Bauch, Dorothea; Hathorne, Ed C.; Rabe, Benjamin; von Appen, Wilken-Jon; Wegner, Carolyn; Zieringer, Moritz; Kassens, Heidemarie


    The water masses passing the Fram Strait are mainly responsible for the exchange of heat and freshwater between the Nordic Seas and the Arctic Ocean (the Arctic Mediterranean, AM). Disentangling their exact sources, distribution and mixing, however, is complex. This work provides new insights based on a detailed geochemical tracer inventory including dissolved Nd isotope (εNd), rare earth element (REE) and stable oxygen isotope (δ18O) data along a full water depth section across Fram Strait. We find that Nd isotope and REE distributions in the open AM primarily reflect lateral advection of water masses and their mixing. Seawater-particle interactions exert important control only above the shelf regions, as observed above the NE Greenland Shelf. Advection of northward flowing warm Atlantic Water (AW) is clearly reflected by an εNd signature of -11.7 and a Nd concentration ([Nd]) of 16 pmol/kg in the upper ∼500 m of the eastern and central Fram Strait. Freshening and cooling of the AW on its way trough the AM are accompanied by a continuous change towards more radiogenic εNd signatures (e.g. -10.4 of dense Arctic Atlantic Water). This mainly reflects mixing with intermediate waters but also admixture of dense Kara Sea waters and Pacific-derived waters. The more radiogenic εNd signatures of the intermediate and deep waters (reaching -9.5) are mainly acquired in the SW Nordic Seas through exchange with basaltic formations of Iceland and CE Greenland. Inputs of Nd from Svalbard are not observed and surface waters and Nd on the Svalbard shelf originate from the Barents Sea. Shallow southward flowing Arctic-derived waters (freshwater of up to ∼6%. In addition to these observations, this study shows that the pronounced gradients in εNd signatures and REE characteristics in the upper water column provide a reliable basis for assessments of shallow hydrological changes within the AM.

  20. Lead Isotope Constraints on the Sources of Ore Metals in SW Mexican Deposits

    Potra, A.; Macfarlane, A. W.


    Lead isotope ratios from mineral deposits in southern Mexico increase with distance from the trench from 206Pb/204Pb values between 18.597 and 18.650 in the coastal area to values between 18.712 and 19.069 approximately 800 km east from the trench. This variation has been attributed to increasing assimilation of radiogenic lead from the crust with increasing distance from the trench. New sampling was undertaken in this area to provide a clearer picture of the potential sources of ore metals in this arc system, and also, if possible, to examine whether ore metal sources differ among the proposed tectonostratigraphic exotic terranes of southern Mexico. New TIMS lead isotope analyses are presented for samples from the metamorphic basement rocks of the Guerrero Terrane, the Late Cretaceous clastic sedimentary rocks from the Upper Mesozoic Assemblage, and for mid-Cretaceous igneous rocks, as well as for samples from the Oligocene La Verde, Esmeralda, and El Malacate copper prospects. Whole rock samples of schist from the Jurassic-Cretaceous Arteaga Complex and phyllite and slate from the Tierra Caliente Complex contain radiogenic lead relative to bulk earth models, with 206Pb/204Pb ranging from 18.981-19.256. These values are substantially more radiogenic than published values of analyses of metagabbro and charnockite from the Grenvillian-age Oaxaca Terrane. Sedimentary rocks (sandstones, siltstones, and marls) belonging to the Huetamo Sequence have 206Pb/204Pb values ranging between 18.630 to 18.998, close to the published data for the sediments from IPOD-DSDP Sites 487 and 488, Cocos Plate. Whole rock analyses of igneous rocks (granodiorite) collected from La Verde and El Malacate have 206Pb/204Pb ranging from 18.764 to 18.989, clustering between the fields represented by the sedimentary and the metamorphic rocks, suggesting assimilation of lead from these components. Ore samples from La Verde and Esmeralda have 206Pb/204Pb between 18.685 and 18.731 and plot within

  1. Modes of planetary-scale Fe isotope fractionation

    Schoenberg, Ronny; Blanckenburg, Friedhelm von


    Fe isotope composition of lithospheric mantle xenoliths are representative for an undisturbed melt source, and second, HED and SNC meteorites, representing melting products of 4Vesta and Mars silicate mantles would be expected to show a similar fractionation towards heavy isotope compositions. This is not observed. Four international granitoid standards with SiO 2 contents between 60 and 70 wt.% yield δ56Fe/ 54Fe values between 0.118‰ and 0.132‰. An investigation of the alpine Bergell igneous rock suite revealed a positive correlation between Fe isotope compositions and SiO 2 contents — from gabbros and tonalites ( δ56Fe/ 54Fe ≈ 0.03 to 0.09‰) to granodiorites and silicic dykes ( δ56Fe/ 54Fe ≈ 0.14 to 0.23‰). Although in this suite δ56Fe/ 54Fe correlates with δ18O values and radiogenic isotopes, open-system behavior to explain the heavy iron is not undisputed. This is because an obvious assimilant with the required heavy Fe isotope composition has so far not been identified. Alternatively, the relatively heavy granite compositions might be obtained by fractional crystallisation of the melt. Ultimately, further detailed studies on natural rocks and the experimental determination of mineral/melt fractionation factors at magmatic conditions are required to unravel whether or not iron isotope fractionation takes place during partial mantle melting and crystal fractionation.

  2. S Isotope Ratios of Central Italy Waters to Assess Their Origin

    Castorina, Francesca; Masi, Umberto


    Sr isotopes have so far applied only occasionally to the study of the waters from central Italy. Therefore, we have analyzed more than 30 water samples from thermal and cold springs, and from the lakes located in the Quaternary K-alkaline volcanic districts of Latium, aimed at providing significant information on the sources of Sr and the hydrologic circulation. The 87Sr/86Sr composition of the waters shows a general correlation with the aquifer rocks, resulting in the waters from older carbonatic rocks having a less radiogenic signature than those from younger K-alkaline volcanic rocks. The Sr-isotope ratios of most thermal waters range narrowly by 0.708, indicating a common source of Sr, likely represented by the Upper Triassic Burano Anhydrites, i.e. the lowermost permeable formation in the study area. Moreover, the positive correlation between Sr and Ca suggests that bulk Ca was also supplied from that source. A minor number of thermal waters as well as all the waters from the lakes and cold springs display a larger Sr isotopic range (0.7085-0.7115), suggesting a relative large spectrum of sources for Sr. In particular, some waters derive their Sr from a singular source, but the most show isotopic signatures suggestive of mixed contributions from different aquifers. As a whole, the results from this study confirm that Sr isotopes are a useful tool contributing to explain the geochemical characteristics of surficial and groundwaters.

  3. Helium isotope studies of the mantle xenoliths and megac-rysts from the Cenozoic basalts in the eastern China

    LI; Yanhe


    ., 1983, 66: 388-399.[12]Rion, W., Craig, H., Helium isotope and mantle volatiles in Loihi Seamount and Hawaiian Islands basalts and xenoliths, Earth Planet Sci. Lett., 1983, 66: 407-426.[13]Dunai, T. J., Baur, H., Helium, Neon, and argon systematics of the European subcontinental mantle: Implications for its geochemical evolution, Geochim. Cosmochim. Acta, 1995, 59(13): 2767-2783.[14]Patterson, D. B., Honda, M., Dcdougall, I., Noble gases in mafic phenocrysts and xenoliths from New Zealand, Geochimi. Cosmochim. Acta, 1994, 58(20): 4411-4427.[15]Xu Sheng, Liu Congqiang, The helium isotope compositions of the mantle xenoliths and their significance in the mantle geochemical evolution, Chinese Science Bulletin (in Chinese), 1997, 42(11): 1190-193.[16]Li Yanhe, Song Hebin, Li Jincheng, et al., Relationship between polymetallic nodules and submarine hydrothermalism in the Central Pacific Ocean, Chinese Science Bulletin, 1997, 42(23): 1980-1982.[17]Irving, A. J., Frey, F. A., Trace element abundances in megacrysts and their host basalts: Constraints on megacryst genesis, Geochim. Cosmochim. Acta, 1984, 48:1201-1221.[18]Guo Lihe, Lin Xingyuan, Water from the mantle xenoliths in Hannuoba basalt, Hebei, Geological Sinica (in Chinese), 1998, 72(2): 138-143.[19]Niedermann, S., Bach, W., Erzinger, J., Noble gas evidence for a lower mantle component in MORBs from the southern East Pacific Rise: Decoupling of helium and neon isotope systematics, Geochim. Cosmochim. Acta, 1997, 61(13): 2697-2715.[20]White, W. M., Sources of oceanic basalts: Radiogenic isotope evidence, Geology, 1985, 13: 115-118.[21]Hofman, A. W., Chemical differentiation of the Earth: The relationship between mantle,continental crust, and oceanic crust, Earth Planet. Sci. Lett., 1988, 90: 297-314.[22]Matsumoto, T., Hoda, M., Mcdougall, I., Plume-like neon in metasomatic apatite from the Australian lithospheric mantle, Nature, 1997, 388: 162-164.[23]Sun, S. S., Mcdonough


    Spevack, J.S.


    An isotope concentration process is described which consists of exchanging, at two or more different temperature stages, two isotopes of an element between substances that are physically separate from each other and each of which is capable of containing either of the isotopes, and withdrawing from a point between at least two of the temperatare stages one of the substances containing an increased concentration of the desired isotope.

  5. Regional variations in the lead isotopic composition of galena from southern Korea with implications for the discrimination of lead provenance

    Jeong, Youn-Joong; Cheong, Chang-sik; Shin, Dongbok; Lee, Kwang-Sik; Jo, Hui Je; Gautam, Mukesh Kumar; Lee, Insung


    This study presents a comprehensive database (n = 215) of lead isotopes in galena from the southern Korean peninsula using new and published data. Of the 69 metal mines examined, predominantly skarn- and hydrothermal-type Pb-Zn-Au-Ag-Cu deposits were observed and were associated with Mesozoic magmatic activities. Galena samples from each geotectonic unit showed discrete lead isotopic signatures. The Gyeongsang basin samples were characteristically unradiogenic and had restricted variations in lead isotopic composition (206Pb/204Pb = 18.16-18.59, 207Pb/204Pb = 15.48-15.64, 208Pb/204Pb = 37.87-38.77). Their 208Pb/204Pb range indicated an involvement of source materials less thorogenic than the associated granites. The galena samples from Cambro-Ordovician carbonate rocks of the northeastern Yeongnam massif and eastern Taebaeksan basin had the most radiogenic 206Pb/204Pb (19.28 ± 0.14) and 207Pb/204Pb (15.833 ± 0.027) ratios. Their lead isotopic trend indicated a combined contribution of ore lead from granitic magmas, Precambrian basements, and overlain host rocks. Less radiogenic galena samples from the middle to southwestern parts of the Yeongnam massif and Okcheon belt showed limited lead isotopic variations (206Pb/204Pb = 18.332 ± 0.065, 207Pb/204Pb = 15.693 ± 0.012, 208Pb/204Pb = 38.93 ± 0.07 on average), probably resulted from mixing with a common crustal basement. The differences in lead isotopes between the radiogenic and unradiogenic groups from the Yeongnam massif and Okcheon belt may reflect the spatial dissimilarity of involved crustal rocks. The old crust appears to have significantly contributed ore lead to galenas from the western Gyeonggi massif, but the geochronological meaning of their steep 207Pb/204Pb-206Pb/204Pb trend is not clear. The comprehensive database constructed by the present study suggests that lead province in the southern Korean peninsula may be subdivided into four discrete zones. Linear discriminant analysis showed that more

  6. Statistical clumped isotope signatures

    Röckmann, T.; Popa, M. E.; Krol, M. C.; Hofmann, M. E. G.


    High precision measurements of molecules containing more than one heavy isotope may provide novel constraints on element cycles in nature. These so-called clumped isotope signatures are reported relative to the random (stochastic) distribution of heavy isotopes over all available isotopocules of a m

  7. Re-Os Isotopes Distinguish Crust vs. Slab Inputs to Northern Cascade Arc Basalts

    Mullen, E.; Gannoun, A.; Nauret, F.; Schiano, P.; Weis, D.


    Delineating the relative contributions of mantle, slab, and crust to arc magmas is particularly challenging in the Cascades where the continental crust is juvenile and contrasts little with magmas in traditional radiogenic isotope systems (Sr-Nd-Hf-Pb). The Re-Os isotope system offers a sensitive technique for evaluating these contributions because even young crust has significantly higher Os ratios than the mantle. We analyzed Re-Os isotope ratios in 33 primitive basalts from 9 volcanic centers of the northern Cascade Arc (Garibaldi Volcanic Belt, GVB). Although GVB basalts have mantle-like Sr-Pb-Nd-Hf ratios (Mullen & Weis, 2015, EPSL), the range in 187Os/188Os is very large (0.13-0.99) with [Os] of Cinder Cone/Mt. Garibaldi, Salal Glacier, Mt. Meager, Indian Pass/Glacier Peak) has low Os isotopic ratios (0.13-0.19), only slightly elevated relative to global mantle wedge peridotites (≤0.16), indicating minimal crustal contamination. Group 1 samples lie on Os-Sr isotope mixing curves indicating variable sediment input to the mantle. Os ratios of Group 2 basalts (Silverthrone, Bridge River, Elaho, Cheakamus, Mt. Baker, Glacier Peak) extend to extremely high values, up to 0.99, and lie on different Os-Sr mixing curves indicating addition of a crustal contaminant. Sr-Nd-Hf-Pb isotopic ratios cannot be used to identify this crustal input because Groups 1 and 2 are identical in these isotope systems. Interaction with a mafic underplate from older Cenozoic or accreted Mesozoic arcs is likely, and Re-Os analyses of basement samples (in progress) will provide a test of this hypothesis. This study reveals that most primitive magmas in the Cascades have suffered variable crustal contamination, but only the Re-Os isotope system has the potential to delineate the extent of this involvement.

  8. Systematic of dipole excitations in the stable sup 1 sup 3 sup 4 sup , sup 1 sup 3 sup 5 sup , sup 1 sup 3 sup 6 sup , sup 1 sup 3 sup 7 sup , sup 1 sup 3 sup 8 Ba isotopes

    Scheck, M; Brentano, P V


    In this contribution the focus is on the systematic study of [2 sup + x3 sup -] sub 1 -two-phonon excitations around the Z = 50 and N = 82 shell closures. The results for the Sn and Ba isotope chains will be shown in a general framework of all available data obtained by nuclear resonance fluorescence experiments. The photon scattering experiments referred to in this work were performed at the Bremsstrahlung facility of the 4.3 MV Stuttgart Dynamitron accelerator. NRF experiments are suitable for the determination of excitation energies, spins, lifetimes and transition strengths of low-spin states. The even-even isotopes show strong 1 sup - excitations close to the sum energy of the 2 sup + and 3 sup - phonons, interpreted as [2 sup + x3 sup -] sub 1 -two phonon excitations. The behaviour of these [2 sup + x 3 sup -] sub 1 -states in even-even nuclei can be explained by the so-called DCP effect. Furthermore, the coupling of a single nucleon to this collective excitation in the neighbouring odd-mass nuclei is i...

  9. Serpentinization Changes Nd, but not Hf Isotopes of Abyssal Peridotites

    Bizimis, M.; Frisby, C. P.; Mallick, S.


    Serpentinization of the oceanic lithosphere is a known sink for fluid mobile elements (B, Cl, Li, Sr, etc.), while high field strength elements (HFSE: e.g., Hf, Zr, Ti, Nb) are thought to be unaffected by it. In contrast, the fate of REE during serpentinization is equivocal. Correlations between REE and HFSE concentrations in abyssal peridotites suggest control by magmatic processes (Niu, 2004, J. Pet), while some LREE enrichments in serpentinized peridotites compared to their clinopyroxene (cpx) and Nd, Sr isotope data (Delacour et al., 2008, Chem. Geol.) imply seawater-derived REE addition to the mantle protolith (Paulick et al., 2006, Chem. Geol). To further constrain peridotite-seawater interaction during serpentinization we compare bulk rock and cpx Hf and Nd isotope data in partially (up to ~70%) serpentinized abyssal peridotites (9-16°E South West Indian Ridge). We also present a new method that improves yields in Hf, Nd and Pb separations from depleted (90% of Hf, Zr, Ti are retained in the residue. LA-ICPMS data shows that serpentine after olivine typically has higher LREE/HREE ratios than cpx, pronounced negative Ce anomalies, high U, Sr concentrations and low HFSE, unlike the coexisting cpx. These data are consistent with some seawater-derived LREE addition to peridotite during serpentinization, localized in the serpentine and other secondary phases, while cpx retains the magmatic value. This process will lower the Sm/Nd relative to Lu/Hf ratio in the peridotite and can lead to decoupled radiogenic Hf and unradiogenic Nd isotopes upon recycling and aging. Our data further testifies to the fidelity of Hf isotopes in tracing mantle processes, even in serpentinized rocks.

  10. The influence of intruder states in even-even Po isotopes

    García-Ramos, J. E., E-mail: [Departamento de Física Aplicada, Universidad de Huelva, 21071 Huelva (Spain); Heyde, K., E-mail: [Department of Physics and Astronomy, Ghent University, Proeftuinstraat 86, B-9000 Gent (Belgium)


    We study the role of intruder states and shape coexistence in the even-even {sup 190–206}Po isotopes, through an interacting boson model with configuration mixing calculation. We analyzed the results in the light of known systematics on various observable in the Pb region, paying special attention to the unperturbed energy systematics and quadrupole deformation. We find that shape coexistence in the Po isotopes behaves in very much the same way as in the Pt isotopes, i.e., it is somehow hidden, contrary to the situation in the Pb and the Hg isotopes.

  11. Generation of Radixenon Isotopes

    McIntyre, Justin I.; Bowyer, Ted W.; Hayes, James C.; Heimbigner, Tom R.; Morris, Scott J.; Panisko, Mark E.; Pitts, W. K.; Pratt, Sharon L.; Reeder, Paul L.; Thomas, Charles W.


    Pacific Northwest National Laboratory has developed an automated system for separating Xe from air and can detect the following radioxenon isotopes, 131mXe, 133mXe, 133Xe, and 135Xe. This report details the techniques used to generate the various radioxenon isotopes that are used for the calibration of the detector as well as other isotopes that have the potential to interfere with the fission produced radioxenon isotopes. Fission production is covered first using highly enriched uranium followed by a description and results from an experiment to produce radioxenon isotopes from neutron activation of ambient xenon.

  12. Isotopes in heterogeneous catalysis

    Hargreaves, Justin SJ


    The purpose of this book is to review the current, state-of-the-art application of isotopic methods to the field of heterogeneous catalysis. Isotopic studies are arguably the ultimate technique in in situ methods for heterogeneous catalysis. In this review volume, chapters have been contributed by experts in the field and the coverage includes both the application of specific isotopes - Deuterium, Tritium, Carbon-14, Sulfur-35 and Oxygen-18 - as well as isotopic techniques - determination of surface mobility, steady state transient isotope kinetic analysis, and positron emission profiling.

  13. Radiation-related caries. Etiology and possible preventive strategies. What should the radiotherapist know?; Radiogene Karies. Aetiologie und Moeglichkeiten der Praevention. Was sollte der Strahlentherapeut wissen?

    Schweyen, R.; Hey, J. [Martin-Luther-Univ., Halle-Wittenberg (Germany). Universitaetspoliklinik fuer Prothetik; Fraenzel, W. [Martin-Luther-Univ., Halle-Wittenberg (Germany). Inst. fuer Physik; Vordermark, D. [Martin-Luther-Univ., Halle-Wittenberg (Germany). Universitaetsklinik und Poliklinik fuer Strahlentherapie; Hildebrandt, G.; Kuhnt, T. [Universitaetsklinikum Rostock (Germany). Universitaetsklinik und Poliklinik fuer Strahlentherapie


    After radiation treatment of head-and-neck cancer, the impairment of patient's quality of life still remains an issue. After completion of the treatment course, a substantial number of patients develop so-called radiation caries. In addition, almost 50% of all cases of infectious osteoradionecrosis (iORN) of the jaws are directly associated with radiation caries. This review addresses our current knowledge on the etiology and pathogenesis of radiation caries including possible preventive strategies. Materials and methods A PubMed search using the terms ''radiation caries'' (''radiation related caries'', ''radiation related damage to dentition'') and ''radiogenic caries'' (''postradiation caries'', ''dental complications and radiotherapy'') was performed. The analysis of its content focused on the etiology, the pathogenesis, and the available knowledge on prophylaxis as well as treatment of radiation caries. Results For this review, 60 publications were selected. As main causal factors for radiogenic caries, either indirect impairment, resulting from alterations in the oral environment (e.g., radiation-induced xerostomia) or direct radiation-induced damage in teeth hard tissues are discussed. Radiation caries remains a lifelong threat and, therefore, requires permanent prevention programs. Conclusion To enable optimal medical care of the patients during the time course of radiotherapy as well as afterwards, close interdisciplinary cooperation between radiotherapists, oral surgeons, otorhinolaryngologists, and dentists is absolutely essential. (orig.)

  14. Sr isotope tracing of aquifer interactions in an area of accelerating coal-bed methane production, Powder River Basin, Wyoming

    Frost, C.D.; Pearson, B.N.; Ogle, K.M.; Heffern, E.L.; Lyman, R.M. [University of Wyoming, Laramie, WY (United States). Dept. of Geology & Geophysics


    Sr isotope data on groundwater samples from coal and overlying sandstone aquifers in the eastern Powder River Basin, Wyoming, demonstrate that the Sr isotope ratio effectively identifies groundwater from different aquifers where major ion geochemistry and 0 and H stable isotope data fail. Groundwaters from sandstone aquifers have a uniform Sr-87/Sr-86 ratio of 0.7126-0.7127. Waters from coal seams vary from Sr-87/Sr-86 ratio = 0.7127 near the recharge area to 0.7151 farther into the basin. The distinct Sr isotope signatures of sandstone and coal aquifers may reflect different sources of Sr in these two rock types: Sr in sandstones is held primarily in carbonate cement, whereas coals contain more radiogenic Sr in organic matter. The Sr isotope ratio is useful in identifying wells that contain mixed waters, whether due to well construction or to incomplete aquifer isolation. Measurement and continued monitoring of the Sr isotope ratio in groundwaters should provide a powerful tool for characterizing the impact of the burgeoning coal-bed methane industry on the hydrology of the Powder River Basin.

  15. Sourcing explosives: a multi-isotope approach.

    Widory, David; Minet, Jean-Jacques; Barbe-Leborgne, Martine


    Although explosives are easily identified with current instrumental techniques, it is generally impossible to distinguish between sources of the same substance. To alleviate this difficulty, we present a multi-stable isotope (delta13C, delta15N, delta18O, deltaD) approach for appraising the possibility of discriminating explosives. The results from 30 distinct PETN, TNT and ANFO samples show that the different families of explosives are clearly differentiated by both their specific isotope signatures and their combination with corresponding element concentrations. Coupling two or more of the studied isotope systematics yields an even more precise differentiation on the basis of their raw-material origin and/or manufacturing process.

  16. Modeling the Nd isotopic composition in the North Atlantic basin using an eddy-permitting model

    Arsouze, T.; Treguier, A. M.; Peronne, S.; Dutay, J.-C.; Lacan, F.; Jeandel, C.


    Boundary Exchange (BE - exchange of elements between continental margins and the open ocean) has been emphasized as a key process in the oceanic cycle of neodymium (Nd) (Lacan and Jeandel, 2005a). Here, we use a regional eddy-permitting resolution Ocean General Circulation Model (1/4°) of the North Atlantic basin to simulate the distribution of the Nd isotopic composition, considering BE as the only source. Results show good agreement with the data, confirming previous results obtained using the same parameterization of the source in a coarse resolution global model (Arsouze et al., 2007), and therefore the major control played by the BE processes in the Nd cycle on the regional scale. We quantified the exchange rate of the BE, and found that the time needed for the continental margins to significantly imprint the chemical composition of the surrounding seawater (further referred as characteristic exchange time) is of the order of 0.2 years. However, the timescale of the BE may be subject to large variations as a very short exchange time (a few days) is needed to reproduce the highly negative values of surface waters in the Labrador Sea, whereas a longer one (up to 0.5 years) is required to simulate the radiogenic influence of basaltic margins and distinguish the negative isotopic signatures of North Atlantic Deep Water from the more radiogenic southern origin water masses. This likely represents geographical variations in erosion fluxes and the subsequent particle load onto the continental margins. Although the parameterization of the BE is the same in both configurations of the model, the characteristic exchange time in the eddy-permitting configuration is significantly lower than the previous evaluations using a low resolution configuration (6 months to 10 years), but however in agreement with the available seawater Nd isotope data. This results highlights the importance of the model dynamics in simulating the BE process.

  17. Osmium Isotopic Evidence Against an Impact at the Frasnian-Famennian Boundary

    Gordon, G. W.; Turekian, K. K.; Rockman, M.; Over, J.


    Two sections across the Frasnian-Famennian boundary were analyzed for Re and Os concentrations and 187Os/188Os ratios to evaluate evidence for a meteoritic input coincident with this boundary and its associated mass extinction. These sections are from a siltstone and shale sequence at Irish Gulf in New York, US and a calcareous shale and ferromanganese oxide sequence at La Serre in France. The Irish Gulf section, with an initial 187Os/188Os of ~0.49, does not show the characteristic meteoritic Os imprint with a 187Os/188Os value of about 0.13. Both Re and Os are retained in this section, as indicated by the construction of an isochron with an age of 388 ±41 Ma, consistent with independently determined ages for the Frasnian-Famennian boundary. Although the La Serre section, with Os concentrations as high as 33 ppb and Re concentrations ranging from 1.4 to 7.4 ppb, might be expected to show excellent evidence for a meteoritic contribution, the highly radiogenic isotopic composition (187Os/188Os ranges from 2.42-3.61) instead suggests recent massive Re loss or addition of radiogenic Os. This open system behavior prevents the reconstruction of an initial 187Os/188Os value for the boundary at La Serre. Assuming reasonable Re concentrations prior to loss, however, the Os isotopic value is inconsistent with a large meteoritic component. In addition, this study reinforces the need for Os isotopic evidence, not only enriched PGE concentrations, as substantiation for a meteoritic impact.

  18. Stable water isotope patterns in a climate change hotspot: the isotope hydrology framework of Corsica (western Mediterranean).

    van Geldern, Robert; Kuhlemann, Joachim; Schiebel, Ralf; Taubald, Heinrich; Barth, Johannes A C


    The Mediterranean is regarded as a region of intense climate change. To better understand future climate change, this area has been the target of several palaeoclimate studies which also studied stable isotope proxies that are directly linked to the stable isotope composition of water, such as tree rings, tooth enamel or speleothems. For such work, it is also essential to establish an isotope hydrology framework of the region of interest. Surface waters from streams and lakes as well as groundwater from springs on the island of Corsica were sampled between 2003 and 2009 for their oxygen and hydrogen isotope compositions. Isotope values from lake waters were enriched in heavier isotopes and define a local evaporation line (LEL). On the other hand, stream and spring waters reflect the isotope composition of local precipitation in the catchment. The intersection of the LEL and the linear fit of the spring and stream waters reflect the mean isotope composition of the annual precipitation (δP) with values of-8.6(± 0.2) ‰ for δ(18)O and-58(± 2) ‰ for δ(2)H. This value is also a good indicator of the average isotope composition of the local groundwater in the island. Surface water samples reflect the altitude isotope effect with a value of-0.17(± 0.02) ‰ per 100 m elevation for oxygen isotopes. At Vizzavona Pass in central Corsica, water samples from two catchments within a lateral distance of only a few hundred metres showed unexpected but systematic differences in their stable isotope composition. At this specific location, the direction of exposure seems to be an important factor. The differences were likely caused by isotopic enrichment during recharge in warm weather conditions in south-exposed valley flanks compared to the opposite, north-exposed valley flanks.

  19. Recovery of radiogenic lead-208 from a residue of thorium and rare earths obtained during the operation of a thorium purification pilot plant; Separacao e recuperacao de chumbo-208 dos residuos de torio terras raras gerados na unidade piloto de purificacao de nitrato de torio

    Seneda, Jose Antonio


    Brazil has a long tradition in thorium technology, from mineral dressing (monazite) to the nuclear grade thorium compounds. The estimate reserves are 1200,000. ton of ThO{sub 2}. As a consequence from the work of thorium purification pilot plant at Instituto de Pesquisas Energeticas e Nucleares-CNEN/IPEN-SP, about 25 ton of a sludge containing thorium and rare earths was accumulated. It comes as a raffinate and washing solutions from thorium solvent extraction. This sludge, a crude hydroxide named RETOTER contains thorium, rare earths and minor impurities including the radiogenic lead-208, with abundance 88.34 %. This work discusses the results of the studies and main parameters for its recovery by anionic ion exchange technique in the hydrochloric system. The isotope abundance of this lead was analyzed by high resolution mass spectrometer (ICPMS) and thermoionic mass spectrometer (TIMS) and the data was used to calculate the thermal neutron capture cross section. The value of {sigma}{gamma}{sup 0} = 14.6{+-}0.7 mb was found, quite different from the {sigma}{gamma}{sup 0} = 174.2 {+-} 7.0 mb measure cross section for the natural lead. Preliminary study for the thorium and rare earths separation and recovery was discussed as well. (author)

  20. Hafnium and neodymium isotopes and REY distribution in the truly dissolved, nanoparticulate/colloidal and suspended loads of rivers in the Amazon Basin, Brazil

    Merschel, Gila; Bau, Michael; Schmidt, Katja; Münker, Carsten; Dantas, Elton L.


    Radiogenic isotopes in river sediments and river waters have been widely used in provenance studies, as these samples naturally integrate the geology/chemistry of the entire catchment. While the Hf and Nd isotope systems are coupled during igneous processes, they are decoupled during supergene processes at the Earth's surface, which is reflected by the isotope composition of riverine sediments. We present the first data for both Hf and Nd isotope compositions of the dissolved (0.2 μm-filtrates rich in nanoparticles and colloids, NPCs) and the truly dissolved (1 kDa-ultrafiltrates) load of rivers. Hafnium and Nd isotope compositions and concentrations of the Rare Earths and Yttrium (REY) and Hf were determined for suspended particles (>0.2 μm) as well as for the dissolved and the truly dissolved load of the Rio Solimões, the Amazon's largest tributary draining the Andes, and of the Rio Negro, an organic NPC- and particle-rich river draining the rainforest of northern Amazonia. We also analyzed the Nd isotope compositions of suspended sediments and 0.2 μm-filtered water samples from the Amazon River and its tributaries Rio Tapajos, Rio Xingu and Rio Jari. Our novel results clearly show that the decoupling of the Hf and Nd isotope systems is related to incongruent weathering processes on the continent, as this decoupling can already be observed in the different Hf and Nd pools, i.e. in the particulate, the NPC-dominated dissolved and the truly dissolved load of rivers. In the Rio Negro and Rio Solimões, a strong particle size-dependent difference in Hf isotope composition is observed. Values of εHf become more radiogenic as filter poresize decreases, which can be related to the density- and size-dependent distribution of Hf-rich minerals, e.g. zircons, and their absence from the truly dissolved pool. In contrast, the Nd isotope composition of Amazonian river waters reflects that of their catchment geology. Tributaries draining the Precambrian Brazilian and

  1. Strong Input and Removal of Rare Earth Elements (REEs) Affect Dissolved Nd Isotope Composition of Seawater in the Panama Basin and the Eastern Equatorial Pacific

    Frank, M.; Bosse, L. M.; Grasse, P.; Pahnke, K.; Hathorne, E. C.


    The distributions of dissolved REEs and Nd isotopes are controlled by inputs from land and water mass mixing. We present new data from the Panama Basin in the Eastern Equatorial Pacific (EEP) extending previous studies in the frame of the German SFB 754 project. The samples were taken following GEOTRACES protocols along a section from close to the Panamanian coast into the deep Panama Basin during FS Meteor cruise M90 in October/November 2012. Elevated Nd concentrations near 13 pmol/kg are found at the surface, which rapidly decrease to a subsurface minimum of 8 pmol/kg near 100m depth and then increase with water depth reaching maximum values of 18 pmol/kg at 3000 m water depth. However, these deep water concentrations are more than a factor of 2 lower than observed for North Pacific Deep Water (NPDW), which is the prevailing Pacific deep water mass at the sampling locations. All the REEs are depleted compared to NPDW suggesting that efficient uptake and scavenging dominate compared to release from remineralized particles. The surface waters show the most radiogenic Nd isotope values (ɛNd = +4.3) so far obtained globally. In combination with the Nd concentration maxima at the surface this suggests riverine dissolved and fine grained particulate inputs from southern Panama and Colombia where highly radiogenic volcanic rocks are exposed. Elevated ɛNd values above -1 in the entire water column are more radiogenic than in NPDW in the Central Pacific and in waters further south in the EEP, which confirms that release of REEs from the sinking volcanogenic material affects the entire water column. These data clearly document that significant inputs from land combined with efficient scavenging and removal in surface and deep waters control the distribution of REEs and Nd isotopes in the Panama Basin and the adjacent EEP (Grasse et al., 2012), which also has important implications for the distribution of other trace metals.

  2. Strontium Isotope Study of Coal Untilization By-products Interacting with Environmental Waters

    Spivak-Birndorf, Lev J; Stewart, Brian W; Capo, Rosemary C; Chapman, Elizabeth C; Schroeder, Karl T; Brubaker, Tonya M


    Sequential leaching experiments on coal utilization by-products (CUB) were coupled with chemical and strontium (Sr) isotopic analyses to better understand the influence of coal type and combustion processes on CUB properties and the release of elements during interaction with environmental waters during disposal. Class C fly ash tended to release the highest quantity of minor and trace elements—including alkaline earth elements, sodium, chromium, copper, manganese, lead, titanium, and zinc—during sequential extraction, with bottom ash yielding the lowest. Strontium isotope ratios ({sup 87}Sr/{sup 86}Sr) in bulk-CUB samples (total dissolution of CUB) are generally higher in class F ash than in class C ash. Bulk-CUB ratios appear to be controlled by the geologic source of the mineral matter in the feed coal, and by Sr added during desulfurization treatments. Leachates of the CUB generally have Sr isotope ratios that are different than the bulk value, demonstrating that Sr was not isotopically homogenized during combustion. Variations in the Sr isotopic composition of CUB leachates were correlated with mobility of several major and trace elements; the data suggest that arsenic and lead are held in phases that contain the more radiogenic (high-{sup 87}Sr/{sup 86}Sr) component. A changing Sr isotope ratio of CUB-interacting waters in a disposal environment could forecast the release of certain strongly bound elements of environmental concern. This study lays the groundwork for the application of Sr isotopes as an environmental tracer for CUB–water interaction.

  3. Strontium isotope geochemistry of groundwater affected by human activities in Nandong underground river system, China

    Jiang Yongjun, E-mail: [School of Geographical Sciences, Southwest University, Chongqing 400715 (China)] [Institute of Karst Environment and Rock Desertification Rehabilitation, Chongqing 400715 (China)


    Research highlights: {yields} Spatio-temporal variations of Sr concentrations and Sr isotopic composition of groundwater were investigated in a karst underground river system. {yields} Agricultural fertilizers and sewage effluents significantly modified the natural Sr isotopic signature of karst groundwater. {yields} Sr in the carbonate aquifers was relatively non-radiogenic, with low Sr concentrations, while anthropogenic Sr correlated with agricultural fertilizers and sewage effluents was relatively radiogenic, with higher Sr concentrations. {yields} {sup 87}Sr/{sup 86}Sr ratios can provide key information for natural and anthropogenic sources in karst groundwater. - Abstract: The Nandong Underground River System (NURS) is located in a typical karst area dominated by agriculture in SE Yunnan Province, China. Groundwater plays an important role in the social and economical development in the area. The effects of human activities (agriculture and sewage effluents) on the Sr isotope geochemistry were investigated in the NURS. Seventy-two representative groundwater samples, which were collected from different aquifers (calcite and dolomite), under varying land-use types, both in summer and winter, showed significant spatial differences and slight seasonal variations in Sr concentrations and {sup 87}Sr/{sup 86}Sr ratios. Agricultural fertilizers and sewage effluents significantly modified the natural {sup 87}Sr/{sup 86}Sr ratios signature of groundwater that was otherwise dominated by water-rock interaction. Three major sources of Sr could be distinguished by {sup 87}Sr/{sup 86}Sr ratios and Sr concentrations in karst groundwater. Two sources of Sr are the Triassic calcite and dolomite aquifers, where waters have low Sr concentrations (0.1-0.2 mg/L) and low {sup 87}Sr/{sup 86}Sr ratios (0.7075-0.7080 and 0.7080-0.7100, respectively); the third source is anthropogenic Sr from agricultural fertilizers and sewage effluents with waters affected having radiogenic {sup 87

  4. Fractionation of Oxygen Isotopes by Thermal Ionization Mass Spectrometry Inferred from Simultaneous Measurement of (17)O/(16)O and (18)O/(16)O Ratios and Implications for the (182)Hf-(182)W Systematics.

    Trinquier, Anne


    Accurate (182)Hf-(182)W chronology of early planetary differentiation relies on highly precise and accurate tungsten isotope measurements. WO3(-) analysis by negative thermal ionization mass spectrometry requires W(17)O(16)O2(-), W(17)O2(16)O(-), W(18)O(16)O2(-), W(17)O3(-), W(17)O(18)O(16)O(-), and W(18)O2(16)O(-) isotopologue interference corrections on W(16)O3(-) species ( Harper et al. Geochim. Cosmochim. Acta 1996 , 60 , 1131 ; Quitté et al. Geostandard. Newslett. 2002 , 26 , 149 ; Trinquier et al. Anal. Chem. 2016 , 88 , 1542 ; Touboul et al. Nature 2015 , 520 , 530 ; Touboul et al. Int. J. Mass Spectrom. 2012 , 309 , 109 ). In addition, low ion beam intensity counting statistics combined with Faraday cup detection noise limit the precision on the determination of (18)O/(16)O and (17)O/(16)O relative abundances. Mass dependent variability of (18)O/(16)O over the course of an analysis and between different analyses calls for oxide interference correction on a per integration basis, based on the in-run monitoring of the (18)O/(16)O ratio ( Harper et al. Geochim. Cosmochim. Acta 1996 , 60 , 1131 ; Quitté et al. Geostandard. Newslett. 2002 , 26 , 149 ; Trinquier et al. Anal. Chem. 2016 , 88 , 1542 ). Yet, the (17)O/(16)O variation is normally not being monitored and, instead, inferred from the measured (18)O/(16)O variation, assuming a δ(17)O-δ(18)O Terrestrial Fractionation Line ( Trinquier et al. Anal. Chem. 2016 , 88 , 1542 ). The purpose of the present study is to verify the validity of this assumption. Using high resistivity amplifiers, (238)U(17)O2 and (238)U(18)O2 ion beams down to 1.6 fA have been monitored simultaneously with (235,238)U(16)O2 species in a uranium certified reference material. This leads to a characterization of O isotope fractionation by thermal ionization mass spectrometry in variable loading and running conditions (additive-to-sample ratio, PO2 pressure, presence of ionized metal and oxide species). Proper determination of O

  5. Systematic decay studies of even-even {sup 132-138}Nd, {sup 144-158}Gd, {sup 176-196}Hg and {sup 192-198}Pb isotopes

    Santhosh, K.P., E-mail: [School of Pure and Applied Physics, Kannur University, Payyanur Campus, Payyanur 670 327 (India); Sahadevan, Sabina [School of Pure and Applied Physics, Kannur University, Payyanur Campus, Payyanur 670 327 (India)


    The alpha and cluster decay properties of the {sup 132-138}Nd, {sup 144-158}Gd, {sup 176-196}Hg and {sup 192-198}Pb even-even isotopes in the two mass regions A=130-158 and A=180-198 are analyzed using the Coulomb and Proximity Potential Model. On examining the clusters at corresponding points in the cold valleys (points with same A{sub 2}) of the various isotopes of a particular nucleus we find that at certain mass numbers of the parent nuclei, the clusters emitted are getting shifted to the next lower atomic number. It is interesting to see that the change in clusters appears at those isotopes where a change in shape is occurring correspondingly. Such a change of clusters with shape change is studied for the first time in cluster decay. The alpha decay half lives of these nuclei are computed and these are compared with the available experimental alpha decay data. It is seen that the two are in good agreement. On making a comparison of the alpha half lives of the normal deformed and superdeformed nuclei, it can be seen that the normal deformed {sup 132}Nd, {sup 176-188}Hg and {sup 192}Pb nuclei are found to be better alpha emitters than the superdeformed (in excited state) {sup 134,136}Nd, {sup 190-196}Hg and {sup 194}Pb nuclei. The cluster decay studies reveal that as the atomic number of the parent nuclei increases the N{ne}Z cluster emissions become equally or more probable than the N=Z emissions. On the whole the alpha and cluster emissions are more probable from the parents in the heavier mass region (A=180-198) than from the parents in the lighter mass region (A=130-158). The effect of quadrupole ({beta}{sub 2}) and hexadecapole ({beta}{sub 4}) deformations of parent and fragments on half life times are also studied.

  6. Historical changes of the anthropogenic impact in a coastal lagoon: Pb isotopes and trace elements on mussel`s fleshes and shells

    Labonne, M.; Othman, D.B.; Luck, J.M. [Universite Montpellier II, Laboratoire Geofluides, Bassins, Eaux, Montpellier (France)


    Molluscs are known to concentrate metals and are used as bioindicators in many programs of coastal survey. The aims of this study were: (1) to better understand the spatial and temporal variations of metals in a greatly anthropized lagoon (Thau, S France) by using concentrations and Pb isotopes in mussel flesh; (2) to compare present and past environment and the different sources of local Pb in recent mussel shells and ones from the Roman empire. Young mussels (Mytilus galloprovincialis) from the sea were introduced at various locations in the lagoon. The ancient shells came from a Roman villa on the lagoon coast. We compare their isotopic compositions to different sources present on the watershed such as rocks, road, harbour, ancient lead castings or Spanish and English ingots. Concentrations of trace metals were determined directly by ICP-MS after proper dilution and the isotopic compositions was determined on a VG Sector mass spectrometer. The Pb concentration variations are difficult to separate from weight variations so we use isotopic compositions for determination of lead sources. The Pb isotopic composition of the flesh define nice alignments in {sup 207}Pb/{sup 204}Pb vs {sup 206}Pb/{sup 204}Pb diagram with season, which can be explained by two-component mixtures. However, while one end-member remains quite stable and influenced by road network, the other one shifts to more radiogenic values indicating either a variable origin, or varying proportions of a third component. The ancient shells have more radiogenic isotopes than the current shells but shift towards ancient lead castings and ingots signature. Variations of Pb ratios in the ancient shells can be roughly correlated with age and the evolution of population density around the lagoon over the centuries

  7. Lead isotope study of Zn-Pb ore deposits associated with the Basque-Cantabrian basin and Paleozoic basement, Northern Spain

    Velasco, F.; Pesquera, A.; Herrero, J. M.


    A total of forty-three galena samples from syngenetic and epigenetic Pb-Zn mineralizations emplaced in the Lower Cretaceous Basque-Cantabrian basin and Paleozoic basement of the Cinco Villas massif in the western Pyrenees, have been analyzed for Pb-isotopic composition. Galena from sedex mineralizations hosted in Carboniferous clastic rocks in the Cinco Villas massif display an homogeneous lead isotopic signature (206Pb/2044Pb ≈ 18.43, 207Pb/204Pb ≈ 15.66, 208Pb/ 204Pb ≈ 38.69) suggesting a single lead reservoir. These values are slightly more radiogenic than lead from other European Hercynian deposits, possibly reflecting the influence of a more evolved upper crustal source. Underlying Paleozoic sediments are proposed as lead source for the Cinco Villas massif ores. Analyses from twenty-six galena samples from the four strata-bound ore districts hosted in Mesozoic rocks reveal the existence of two populations regarding their lead isotopic composition. Galena from the western Santander districts (e.g., Reocin) is characterized by more radiogenic isotope values (206Pb/204Pb ≈ 18.74, 207Pb/204Pb ≈ 15.67, 208Pb/ 204Pb ≈ 38.73) than those from the central and eastern districts (Troya-Legorreta, Central and Western Vizcaya, 206Pb/204Pb ≈ 18.59, 207Pb/204Pb ≈ 15.66, 208Pb/ 204Pb ≈ 38.73). In all districts, the most likely source for these mineralizations was the thick sequence of Lower Cretaceous clastic sediments. The existence of two separate lead isotopic populations could be the result of regional difference in the composition of the basement rocks and the clastic sediments derived of it or different evolution histories. In both sub-basins, isotopic ratios indicate an increase in crustal influence as the age of the ores decreases.

  8. Constraints on the development of the early continental crust from isotopic data

    Jacobson, S. B.


    Aspects of the origin and development of the early (AE) continential crust are addressed by radiogenic isotope and trace element studies. The most important ones are: (1) at what time did the earliest continental crust form; (2) what was its composition; (3) by what processes did it grow and by what processes was it destroyed; (4) what were the rates of production and destruction as a function of time during this time period? Nd is isotopic data on the oldest terrestrial rocks indicate that the mantle at this time had already suffered substantial depletion in incompatible elements due to earlier continent forming events. Isotopic data on young volcanic rocks derived from the depleted mantle show no evidence of this early history. The observed isotopic patterns of Nd, Sr, Hf and Pb through time together with the presently observed age spectrum of crustal rocks are considered. These patterns can be modelled by a transport model in which the continental growth and destruction rates are allowed to vary as a function of time. It is suggest that the mass of the continents at 3.8 AE ago was about 25% of the current continental mass. However, due to the very high recycling rates obtained in the early Archean only a few percent of this crust has been preserved up to the present.

  9. Geochronological and isotopic records of crustal storage and assimilation in the Wolverine Creek-Conant Creek system, Heise eruptive centre, Snake River Plain

    Szymanowski, D.; Ellis, B. S.; Wotzlaw, J. F.; Buret, Y.; von Quadt, A.; Peytcheva, I.; Bindeman, I. N.; Bachmann, O.


    Understanding the processes of differentiation of the Yellowstone-Snake River Plain (YSRP) rhyolites is typically impeded by the apparent lack of erupted intermediate compositions as well as the complex nature of their shallow interaction with the surrounding crust responsible for their typically low O isotopic ratios. A pair of normal-δ18O rhyolitic eruptions from the Heise eruptive centre in eastern Idaho, the Wolverine Creek Tuff and the Conant Creek Tuff, represent unique magmatic products of the Yellowstone hotspot preserving abundant vestiges of the intermediate differentiation steps leading to rhyolite generation. We address both shallow and deep processes of magma generation and storage in the two units by combining high-precision ID-TIMS U-Pb zircon geochronology, trace element, O and Hf isotopic studies of zircon, and Sr isotopic analyses of individual high-Mg# pyroxenes inherited from lower- to mid-crustal differentiation stages. The zircon geochronology confirms the derivation of both tuffs from the same rhyolitic magma reservoir erupted at 5.5941 ± 0.0097 Ma, preceded by at least 92 ± 14 ky of continuous or intermittent zircon saturation approximating the length of pre-eruptive magma accumulation in the upper crust. Some low-Mg# pyroxenes enclosing zircons predate the eruption by at least 45 ± 27 ky, illustrating the co-crystallisation of major and accessory phases in the near-liquidus rhyolitic melts of the YSRP over a significant period of time. Coeval zircon crystals are isotopically heterogeneous (two populations at ɛHf -5 and -13), requiring the assembly of isotopically distinct melt pockets directly prior to, or during, the eruption. The primitive Mg# 60-90 pyroxenes are out of isotopic equilibrium with the host rhyolitic melt (87Sr/86Sri = 0.70889), covering a range of 87Sr/86Sri = 0.70705-0.70883 corresponding to ratios typical of the most radiogenic YSRP basalts to the least radiogenic YSRP rhyolites. Together with the low ɛHf in zircon

  10. Modelling of stable water isotopes in Central Europe with COSMOiso

    Christner, Emanuel; Pfahl, Stephan; Schädler, Gerd


    Atmospheric water in form of vapor or clouds is responsible for ˜75 % of the natural greenhouse effect and carries huge amounts of latent heat. For this reason, a best possible description of the hydrological cycle is a prerequisite for reliable climate modelling. As the stable isotopes H216O, H218O and HDO differ in vapor pressure, they are fractionated during phase changes and contain information about the formation of precipitation, evaporation from the ground, etc. Therefore, the isotopic composition of atmospheric water is an useful tracer to test and improve our understanding of the extremely complex and variable hydrological cycle in Earth's atmosphere. Within the project PalMod the isotope-enabled limited-area model COSMOiso will be used for high-resolution isotope simulations of paleo-climates. For validation with modern observations we compare 12 years of modelled isotope ratios from Central Europe to observations of the Global Network of Isotopes in Precipitation (GNIP) and to observations of isotope ratios of water vapor at different locations in Germany. We find a good agreement of modelled and observed isotope ratios in summer. In winter, we observe a systematic overestimation of modelled isotope ratios in precipitation and low-level water vapor. We relate those differences to specific circulation regimes with predominantly easterly moisture transport and the corresponding strong dependence of modelled isotope ratios on lateral boundary data. Furthermore, we investigate the dependence of modelled isotope ratios in winter on the type of isotope fractionation during surface evaporation at skin temperatures close to the freezing point.

  11. Tracing source pollution in soils using cadmium and lead isotopes.

    Cloquet, C; Carignan, J; Libourel, G; Sterckeman, T; Perdrix, E


    Tracing the source of heavy metals in the environment is of key importance for our understanding of their pollution and natural cycles in the surface Earth reservoirs. Up to now, most exclusively Pb isotopes were used to effectively trace metal pollution sources in the environment. Here we report systematic variations of Cd isotope ratios measured in polluted topsoils surrounding a Pb-Zn refinery plant in northern France. Fractionated Cd was measured in soil samples surrounding the refinery, and this fractionation can be attributed to the refining processes. Despite the Cd isotopic ratios being precisely measured, the obtained uncertainties are still large compared to the total isotopic variation. Nevertheless, for the first time, Cd isotopically fractionated by industrial processes may be traced in the environment. On the same samples, Pb isotope systematics suggested that materials actually used by the refinery were not the major source of Pb in soils, probably because refined ore origins changed over the 100 years of operation. On the other hand, Cd isotopes and concentrations measured in topsoils allowed identification of three main origins (industrial dust and slag and agriculture), assuming that all Cd ores are not fractionated, as suggested by terrestrial rocks so far analyzed, and calculation of their relative contributions for each sampling point. Understanding that this refinery context was an ideal situation for such a study, our results lead to the possibility of tracing sources of anthropogenic Cd and better constrain mixing processes, fluxes, transport, and phasing out of industrial input in nature.

  12. Triple oxygen isotope composition of the Campi Flegrei magma systems

    Iovine, Raffaella Silvia; Wörner, Gerhard; Pack, Andreas; Sengupta, Sukanya; Carmine Mazzeo, Fabio; Arienzo, Ilenia; D'Antonio, Massimo


    Sr-O isotope relationships in igneous rocks are a powerful tool to distinguish magma sources and quantify assimilation processes in magmatic rocks. Isotopic (87Sr/86Sr and 18O/16O-17O/16O) data have been acquired on whole rocks and separated minerals (feldspar, Fe-cpx, Mg-cpx, olivine phenocrysts) from pyroclastic products of the Campi Flegrei volcanic complex (Gulf of Naples, Southern Italy). Oxygen isotope ratios were measured by infrared laser fluorination using a Thermo MAT253 gas source isotope ratio mass spectrometer in dual inlet mode, on ˜2 mg of hand-picked phenocrysts. Variations in triple oxygen isotope ratios (17O/16O, 18O/16O) are expressed as the δ notation relative to VSMOW. Sr isotopic compositions were determined by thermal ionization mass spectrometry after standard cation-exchange methods on separated hand-picked phenocrysts (˜300 mg), and on whole rocks, in case of insufficient sample size to separate crystals. Sr-isotopes in Campi Flegrei minerals range from 0.707305 to 0.707605 and δ18O varies from 6.5 to 8.3‰ . Recalculated δ18Omelt values accordingly show a large range between 7.2 and 8.6‰ . Our data, compared with published δ18O-isotope data from other Italian volcanic centers (Alban Hills, Mts. Ernici, Ischia, Mt. Vesuvius, Aeolian Islands, Tuscany and Sardinia) and from subduction zones worldwide (Kamchatka, Lesser Antilles, Indonesia and Central Andean ignimbrites), show compositions that are very different from typical mantle values. Distinct trends and sources are recognized in our compilation from global data: (1) serpentinized mantle (Kamchatka), (2) sediment-enrichment in the mantle source (Indonesia, Lesser Antilles, Eolian arc), (3) assimilation of old radiogenic continental crust affecting magmas derived from sediment-modified mantle sources (Tuscany, Sardinia), (4) assimilation of lower crustal lithologies (Central Andes, Alban Hills, Mts. Ernici, Ischia). Sr-O-isotope values of Campi Flegrei and Vesuvius magmas

  13. Les terres rares et les isotopes radiogéniques comme traceurs d'échange et de transfert dans les cycles géochimiques externes

    Steinmann, Marc


    This habilitation thesis is entitled "tracing of exchange and transfer processes in surface geochemistry by rare earth elements (REE) and radiogenic isotopes". It presents a summary of my research realized since 1995 as post-doctoral fellow at the "Centre de Géochimie de la Surface" in Strasbourg and since 1998 as lecturer ("Maître de conférences") at the university of Franche-Comté in Besançon. The common topic of all these studies are chemical exchange and transfer processes in surface envi...

  14. Comprehensive Pb-Sr-Nd-Hf isotopic, trace element, and mineralogical characterization of mafic to ultramafic rock reference materials

    Fourny, Anaïs.; Weis, Dominique; Scoates, James S.


    Controlling the accuracy and precision of geochemical analyses requires the use of characterized reference materials with matrices similar to those of the unknown samples being analyzed. We report a comprehensive Pb-Sr-Nd-Hf isotopic and trace element concentration data set, combined with quantitative phase analysis by XRD Rietveld refinement, for a wide range of mafic to ultramafic rock reference materials analyzed at the Pacific Centre for Isotopic and Geochemical Research, University of British Columbia. The samples include a pyroxenite (NIM-P), five basalts (BHVO-2, BIR-1a, JB-3, BE-N, GSR-3), a diabase (W-2), a dolerite (DNC-1), a norite (NIM-N), and an anorthosite (AN-G); results from a leucogabbro (Stillwater) are also reported. Individual isotopic ratios determined by MC-ICP-MS and TIMS, and multielement analyses by HR-ICP-MS are reported with 4-12 complete analytical duplicates for each sample. The basaltic reference materials have coherent Sr and Nd isotopic ratios with external precision below 50 ppm (2SD) and below 100 ppm for Hf isotopes (except BIR-1a). For Pb isotopic reproducibility, several of the basalts (JB-3, BHVO-2) require acid leaching prior to dissolution. The plutonic reference materials also have coherent Sr and Nd isotopic ratios (<50 ppm), however, obtaining good reproducibility for Pb and Hf isotopic ratios is more challenging for NIM-P, NIM-N, and AN-G due to a variety of factors, including postcrystallization Pb mobility and the presence of accessory zircon. Collectively, these results form a comprehensive new database that can be used by the geochemical community for evaluating the radiogenic isotope and trace element compositions of volcanic and plutonic mafic-ultramafic rocks.

  15. Chemical and Isotopic Heterogeneities in the Deep Earth:Importance of Lower Mantle Carbonate-rich Melts

    Collerson, K. D.; Williams, Q.; Murphy, D.


    Evolution of mantle chemical heterogeneity reflects a spectrum of processes. Nature of reservoirs has been inferred from radiogenic isotope and trace element systematics of mid-ocean ridge basalts (MORB) and ocean island basalts (OIB) [1]. Carbonatites, kimberlites and lamproites [2-4] also sample depleted and enriched reservoirs, however, their origin remains equivocal. Secular decrease in Th/U ratio in MORB mantle (DMM), homogeneity of Th/U inferred from Pb-isotopic data, and systematic variation in Nb/Th and Nb/U ratios in MORBs [5], show that recycled components in DMM are well mixed. Thus isotopically hererogeneous domains in DMM must be transient features and are unlikely to yield HIMU and EM chemistries. Explanations for HIMU and EM OIB chemistries include involvement of: (1) subcontinental lithospheric mantle; (2) subducted oceanic lithosphere; (3) subducted sediment; or (4) an enigmatic lower mantle (LM) "plume component". Elevated 3He/4He in OIBs and kimberlites [6] and excess 129Xe and high 40Ar/39Ar [e.g., 7-8] and solar 20Ne/22Ne [9] in carbonatites indicate that they were derived from a primitive, isolated, and less degassed source than MORB. Primordial compositions show that this reservoir escaped atmospheric contamination by Ar, Xe, and Ne and pollution by 4He-rich material (from recycled 238U) during subduction. This primitive reservoir likely exists below the depth subducted slabs obviously penetrate (ca. 1700 km) e.g., [10]. That kimberlites are deeply sourced is also shown by lower mantle inclusions in diamond, e.g., [11]. Importantly, Gp. 1 and 2 kimberlites are isotopically similar to HIMU and EM-1 OIBs [4]. We interpret Gp 1 kimberlites as mixtures of HIMU and EM sources, while Gp. 2 kimberlites (close to EM-1) are interpreted as melts of a Ca perovskite-rich reservoir, possibly from slabs in the LM. We model melting of LM phases to simulate evolution of EM1 and HIMU 87Sr/86Sr, 143Nd/144Nd, 176Hf/177Hf, 207Pb/204Pb, 206Pb/204Pb and 208Pb/204

  16. The Incredible, Embryological Egg: Calcium and Strontium Isotopes Recapitulate Ontogeny

    Gordon, G. W.; Skulan, J. L.


    Embryological development reflects evolutionary history. Understanding the processes of fetal growth is important for curing human birth defects and predicting damage to ecosystems from environmental insults. Tracing enzymatic and hormonal gradients during development, and correlating them to genetic cues dominate modern embryology. Previous work done tracing the mass transfer of elements has generally been limited to isotope spikes in vitro. Natural mass-dependent Ca and Sr isotopic ratios and radiogenic Sr isotopes have the potential to reveal both source and biochemical mechanism information about processes in vivo, but have not previously been extensively explored. The process when a hen lays a fertilized egg that becomes a chick includes formation and dissolution of calcium phosphate (bone) and calcium carbonate (shell). Skulan and DePaolo (1999) showed that chickens have 2% δ44/42Ca between a hen's bones and an egg white; this span represents more than 80% of the entire range of natural Ca isotope variation and illustrates there is significant variation to investigate. A striking feature of archosaurian development that also occurs in many mammals, including humans, is mass transfer of calcium from mother to embryo. The yolk of the domestic hen matures over 7-9 days, but the albumen, shell membranes and shell form in less than 20 hours. Domestic laying hens are at the physiological limit of egg production and selective breeding is no longer an effective method of increasing egg production. 60-75% of the shell's ~1.5 g of calcium comes from dietary sources, while 25-40% comes from the hen's medullary bone. Medullary bone is spicules formed in the marrow of long bones, and is a store of dietary calcium rapidly available for eggshell secretion. During in ovo development, the embryo's skeleton is formed from calcium in the yolk and by bulk dissolution of the eggshell's inner aspect via carbonic anhydrase in a process that has an effect on bone density similar to

  17. Topology in isotopic multispace and origin of mantle chemical heterogeneities

    Allegre, C.J.; Hamelin, B.; Provost, A.; Dupre, B.


    In this paper we present a simple technique for multidimensional treatment of isotopic data, which allows a global and rigorous correlation between the various radiogenic tracers. This technique is based on the determination of eigenvectors of the data matrix, allowing a geometric description of the inertia ellipsoid corresponding to the cluster of experimental data points. The relationships between the various sets of samples can be analyzed using the projections on the main elongation planes. When processing the Pb-Sr-Nd data for the oceanic mantle (OIB+MORB) with this technique we find that at least four different end-members are needed to define the 'mantle array' which thus cannot be a plane surface. Samples from island arcs (IAB) show the contribution of a component clearly out of the oceanic domain and very similar to terrigenous sediments. Continental tholeiites (CFB) also show some sort of contamination (but distinct from that of IAB) by the continental crust. They also show a domain overlapping with that of the oceanic islands corresponding to the compositions of the 'Dupal anomaly'. Multispace analysis also permits a rigorous comparison of relationships between the various isotopic tracers. In particular, we demonstrate that a U-Pb fractionation independent from the correlated Sr-Nd, Th-U and Th-Sr ones does exist. Consequently, a three-dimensional analysis performed only with lead isotopes yields by itself the main information that can be inferred from the five Pb-Sr-Nd dimensions. Helium also yields independent information decoupled with respect to the other tracers, adding one fifth end-member (Loihi, Hawaii islands) to the OIB+MORB array.

  18. Discovery of the Cobalt Isotopes

    Szymanski, T.; Thoennessen, M.


    Twenty-six cobalt isotopes have so far been observed; the discovery of these isotopes is discussed. For each isotope a brief summary of the first refereed publication, including the production and identification method, is presented.

  19. Discovery of the Arsenic Isotopes

    Shore, A; Heim, M; Schuh, A; Thoennessen, M


    Twenty-nine arsenic isotopes have so far been observed; the discovery of these isotopes is discussed. For each isotope a brief summary of the first refereed publication, including the production and identification method, is presented.

  20. Intracellular Cadmium Isotope Fractionation

    Horner, T. J.; Lee, R. B.; Henderson, G. M.; Rickaby, R. E.


    Recent stable isotope studies into the biological utilization of transition metals (e.g. Cu, Fe, Zn, Cd) suggest several stepwise cellular processes can fractionate isotopes in both culture and nature. However, the determination of fractionation factors is often unsatisfactory, as significant variability can exist - even between different organisms with the same cellular functions. Thus, it has not been possible to adequately understand the source and mechanisms of metal isotopic fractionation. In order to address this problem, we investigated the biological fractionation of Cd isotopes within genetically-modified bacteria (E. coli). There is currently only one known biological use or requirement of Cd, a Cd/Zn carbonic anhydrase (CdCA, from the marine diatom T. weissfloggii), which we introduce into the E. coli genome. We have also developed a cleaning procedure that allows for the treating of bacteria so as to study the isotopic composition of different cellular components. We find that whole cells always exhibit a preference for uptake of the lighter isotopes of Cd. Notably, whole cells appear to have a similar Cd isotopic composition regardless of the expression of CdCA within the E. coli. However, isotopic fractionation can occur within the genetically modified E. coli during Cd use, such that Cd bound in CdCA can display a distinct isotopic composition compared to the cell as a whole. Thus, the externally observed fractionation is independent of the internal uses of Cd, with the largest Cd isotope fractionation occurring during cross-membrane transport. A general implication of these experiments is that trace metal isotopic fractionation most likely reflects metal transport into biological cells (either actively or passively), rather than relating to expression of specific physiological function and genetic expression of different metalloenzymes.

  1. Geo-neutrinos: A systematic approach to uncertainties and correlations

    Fogli, G L; Palazzo, A; Rotunno, A M


    Geo-neutrinos emitted by heat-producing elements (U, Th and K) represent a unique probe of the Earth interior. The characterization of their fluxes is subject, however, to rather large and highly correlated uncertainties. The geochemical covariance of the U, Th and K abundances in various Earth reservoirs induces positive correlations among the associated geo-neutrino fluxes, and between these and the radiogenic heat. Mass-balance constraints in the Bulk Silicate Earth (BSE) tend instead to anti-correlate the radiogenic element abundances in complementary reservoirs. Experimental geo-neutrino observables may be further (anti)correlated by instrumental effects. In this context, we propose a systematic approach to covariance matrices, based on the fact that all the relevant geo-neutrino observables and constraints can be expressed as linear functions of the U, Th and K abundances in the Earth's reservoirs (with relatively well-known coefficients). We briefly discuss here the construction of a tentative "geo-neu...

  2. Impact of mineral fertility and bedrock erosion on single-mineral detrital studies: insights from trace-element and Nd-isotope systematics of detrital apatite from the Po River catchment

    Malusa', Marco Giovanni; Wang, Jiangang; Garzanti, Eduardo; Villa, Igor M.; Wittman, Hella


    The detrital record provides an archive of mountain erosion that preserves key information for paleotectonic and paleoclimatic reconstructions. Detrital studies are often based on single-mineral analyses (e.g., geo/thermochronologic analyses on apatite and zircon). Their geologic interpretation can be challenging, because the impact of each eroding source on the detrital record is controlled by a range of factors including the rate of erosion and the fertility of chosen minerals in eroded bedrock. Here, we combine (i) a state-of-the art dataset of trace element and Nd isotope fingerprints of detrital apatite, (ii) a comprehensive dataset of apatite-fertility measurements (Malusà et al. 2016), (iii) fission-track data, and (iv) cosmogenic-derived erosion rates from the Po River catchment (Wittmann et al. 2016), to test the impact of mineral fertility and bedrock erosion on the single-mineral detrital signal preserved in the final sediment sink. Our results show that the information provided by accessory minerals, when complemented with accurate mineral fertility measurements, are fully consistent with information provided by the analysis of more abundant framework minerals. We found that trace element and Nd isotope analyses provide a reliable tool to disentangle the complex single-mineral record of orogenic erosion, and demonstrate that such a record is largely determined by high-fertility source rocks exposed within the drainage. Detrital thermochronology studies based on the lag-time approach should thus preferably include independent provenance discriminations and a full mineral fertility characterization of the potential source areas, in order to ensure a correct identification of the sediment sources and of the exogenic and endogenic processes monitored in the stratigraphic archive. Malusà M.G., Resentini A., Garzanti E., 2016. Hydraulic sorting and mineral fertility bias in detrital geochronology. Gondwana Res., 31, 1-19 Wittmann H., Malusà M.G., Resentini

  3. Osmium isotope evidence for a crustal origin of platinum group elements in the Sudbury nickel ore, Ontario, Canada

    Dickin, A. P.; Richardson, J. M.; Crocket, J. H.; McNutt, R. H.; Peredery, W. V.


    Sulphide ores from the International Nickel Company's (INCO) Creighton Mine, Sudbury, were analysed for osmium isotope ratios by ICP-MS. Rhenium and osmium abundances were determined by isotope dilution using a mixed spike in solid solution in a nickel sulphide matrix. Calculated initial 187Os /188Os ratios at 1.85 Ga (the emplacement age of the Sudbury complex) cluster around 0.60. The occurrence of less radiogenic compositions is attributed to post-emplacement, open-system behaviour of the Re/Os system. The Creighton results strongly overlap the initial ratios of published osmium data from two other Sudbury mines, suggesting a narrow range of isotope ratio in the original ore, within the range of estimated osmium isotope compositions in the country rock at 1.85 Ga, using published and new data. Therefore, the sulphide ores of the Sudbury complex can have an entirely crustal source without a mantle-derived contribution. This conclusion is consistent with published neodymium isotope data for the complex and supports the meteorite impact hypothesis, since this is the most effective means of fusing the large quantity of crustal rocks necessary to generate the complex. The extraction of platinum group elements (PGE) from this silicate melt by a nickel sulphide liquid was probably analogous to the laboratory fire assay procedure.

  4. A Robust and Fully-Automated Chromatographic Method for the Quantitative Purification of Ca and Sr for Isotopic Analysis

    Smith, H. B.; Kim, H.; Romaniello, S. J.; Field, P.; Anbar, A. D.


    High throughput methods for sample purification are required to effectively exploit new opportunities in the study of non-traditional stable isotopes. Many geochemical isotopic studies would benefit from larger data sets, but these are often impractical with manual drip chromatography techniques, which can be time-consuming and demand the attention of skilled laboratory staff. Here we present a new, fully-automated single-column method suitable for the purification of both Ca and Sr for stable and radiogenic isotopic analysis. The method can accommodate a wide variety of sample types, including carbonates, bones, and teeth; silicate rocks and sediments; fresh and marine waters; and biological samples such as blood and urine. Protocols for these isotopic analyses are being developed for use on the new prepFAST-MCTM system from Elemental Scientific (ESI). The system is highly adaptable and processes up to 24-60 samples per day by reusing a single chromatographic column. Efficient column cleaning between samples and an all Teflon flow path ensures that sample carryover is maintained at the level of background laboratory blanks typical for manual drip chromatography. This method is part of a family of new fully-automated chromatographic methods being developed to address many different isotopic systems including B, Ca, Fe, Cu, Zn, Sr, Cd, Pb, and U. These methods are designed to be rugged and transferrable, and to allow the preparation of large, diverse sample sets via a highly repeatable process with minimal effort.

  5. Contrasting origins of the upper mantle revealed by hafnium and lead isotopes from the Southeast Indian Ridge.

    Hanan, Barry B; Blichert-Toft, Janne; Pyle, Douglas G; Christie, David M


    The origin of the isotopic signature of Indian mid-ocean ridge basalts has remained enigmatic, because the geochemical composition of these basalts is consistent either with pollution from recycled, ancient altered oceanic crust and sediments, or with ancient continental crust or lithosphere. The radiogenic isotopic signature may therefore be the result of contamination of the upper mantle by plumes containing recycled altered ancient oceanic crust and sediments, detachment and dispersal of continental material into the shallow mantle during rifting and breakup of Gondwana, or contamination of the upper mantle by ancient subduction processes. The identification of a process operating on a scale large enough to affect major portions of the Indian mid-ocean ridge basalt source region has been a long-standing problem. Here we present hafnium and lead isotope data from across the Indian-Pacific mantle boundary at the Australian-Antarctic discordance region of the Southeast Indian Ridge, which demonstrate that the Pacific and Indian upper mantle basalt source domains were each affected by different mechanisms. We infer that the Indian upper-mantle isotope signature in this region is affected mainly by lower continental crust entrained during Gondwana rifting, whereas the isotope signature of the Pacific upper mantle is influenced predominantly by ocean floor subduction-related processes.

  6. Mass-dependent fractionation of nickel isotopes in meteoritic metal

    Cook, David L.; Wadhwa, Meenakshi; Clayton, Robert N.; Dauphas, Nicolas; Janney, Philip E.; Davis, Andrew M.

    We measured nickel isotopes via multicollector inductively coupled plasma mass spectrometry (MC-ICPMS) in the bulk metal from 36 meteorites, including chondrites, pallasites, and irons (magmatic and non-magmatic). The Ni isotopes in these meteorites are mass fractionated; the fractionation spans an overall range of ≈0.4‰ amu-1. The ranges of Ni isotopic compositions (relative to the SRM 986 Ni isotopic standard) in metal from iron meteorites (≈0.0 to ≈0.3‰ amu-1) and chondrites (≈0.0 to ≈0.2‰ amu-1) are similar, whereas the range in pallasite metal (≈-0.1 to 0.0‰ amu-1) appears distinct. The fractionation of Ni isotopes within a suite of fourteen IIIAB irons (≈0.0 to ≈0.3‰ amu-1) spans the entire range measured in all magmatic irons. However, the degree of Ni isotopic fractionation in these samples does not correlate with their Ni content, suggesting that core crystallization did not fractionate Ni isotopes in a systematic way. We also measured the Ni and Fe isotopes in adjacent kamacite and taenite from the Toluca IAB iron meteorite. Nickel isotopes show clearly resolvable fractionation between these two phases; kamacite is heavier relative to taenite by ≈0.4‰ amu-1. In contrast, the Fe isotopes do not show a resolvable fractionation between kamacite and taenite. The observed isotopic compositions of kamacite and taenite can be understood in terms of kinetic fractionation due to diffusion of Ni during cooling of the Fe-Ni alloy and the development of the Widmanstätten pattern.

  7. Isotopic signatures for natural versus anthropogenic Pb in high-altitude Mt. Everest ice cores during the past 800 years

    Lee, Khanghyun; Hur, Soon Do [Korea Polar Research Institute, Songdo Techno Park, 7-50, Songdo-dong, Yeonsu-gu, Incheon 406-840 (Korea, Republic of); Hou, Shugui [State Key Laboratory of Cryospheric Science, Cold and Arid Regions Environmental and Engineering Research Institute, Chinese Academy of Science, Lanzhou 730000 (China); School of Geographic and Oceanographic Sciences, Nanjing University, Nanjing 210093 (China); Burn-Nunes, Laurie J. [Department of Imaging and Applied Physics, Curtin University of Technology, GPO Box U1987, Perth, WA 6845 (Australia); Hong, Sungmin, E-mail: [Department of Ocean Sciences, Inha University, 253 Yonghyun-dong, Nam-gu, Incheon, 402-751 (Korea, Republic of); Barbante, Carlo [Department of Environmental Sciences, University Ca' Foscari of Venice, Dorsoduro 2137, 30 123 Venice (Italy); Institute for the Dynamics of Environmental Processes-CNR, University Ca' Foscari of Venice, Dorsoduro 2137, 30 123 Venice (Italy); Boutron, Claude F. [Laboratoire de Glaciologie et Geophysique de l' Environnement (UMR Universite Joseph Fourier/CNRS 5183 ), 54 rue Moliere, BP 96, 38402 Saint Martin d' Heres Cedex (France); Unite de Formation et de Recherche ' Physique, Ingenierie, Terre, Environnement, Mecanique' , Universite Joseph Fourier de Grenoble ( Institut Universitaire de France ), 715 rue de la Houille Blanche, BP 53, 38041 Grenoble Cedex 9 (France); Rosman, Kevin J.R. [Department of Imaging and Applied Physics, Curtin University of Technology, GPO Box U1987, Perth, WA 6845 (Australia)


    A long-term record, extending back 800 years (1205 to 2002 AD), of the Pb isotopic composition ({sup 206}Pb/{sup 207}Pb and {sup 208}Pb/{sup 207}Pb) as well as Pb concentrations from high altitude Mt. Everest ice cores has the potential to identify sources and source regions affecting natural and anthropogenic Pb deposition in central Asia. The results show that the regional natural background Pb isotope signature ({approx} 1.20 for {sup 206}Pb/{sup 207}Pb and {approx} 2.50 for {sup 208}Pb/{sup 207}Pb) in the central Himalayas was dominated by mineral dust over the last {approx} 750 years from 1205 to 1960s, mostly originating from local sources with occasional contributions of long-range transported dust probably from Sahara desert and northwestern India. Since the 1970s, the Pb isotope ratios are characterized by a continuous decline toward less radiogenic ratios with the least mean ratios of 1.178 for {sup 206}Pb/{sup 207}Pb and 2.471 for {sup 208}Pb/{sup 207}Pb in the period 1990-1996. The depression of the {sup 206}Pb/{sup 207}Pb and {sup 208}Pb/{sup 207}Pb values during the corresponding periods is most likely due to an increasing influence of less radiogenic Pb of anthropogenic origin mainly from leaded gasoline used in South Asia (India as well as possibly Bangladesh and Nepal). From 1997 to 2002, isotopic composition tends to show a shift to slightly more radiogenic signature. This is likely attributed to reducing Pb emissions from leaded gasoline in source regions, coinciding with the nationwide reduction of Pb in gasoline and subsequent phase-out of leaded gasoline in South Asia since 1997. An interesting feature is the relatively high levels of Pb concentrations and enrichment factors (EF) between 1997 and 2002. Although the reason for this feature remains uncertain, it would be probably linked with an increasing influence of anthropogenic Pb emitted from other sources such as fossil fuel combustion and non-ferrous metal production.

  8. $^{110,116}$Cd($\\alpha,\\alpha$)$^{110,116}$Cd elastic scattering and systematic investigation of elastic $\\alpha$ scattering cross sections along the $Z$ = 48 isotopic and $N$ = 62 isotonic chains

    Kiss, G G; Fülöp, Zs; Gyürky, Gy; Elekes, Z; Farkas, J; Somorjai, E; Yalcin, C; Galaviz, D; Güray, R T; Özkan, N; Görres, J


    The elastic scattering cross sections for the reactions $^{110,116}$Cd($\\alpha,\\alpha$)$^{110,116}$Cd at energies above and below the Coulomb barrier are presented to provide a sensitive test for the alpha-nucleus optical potential parameter sets. Additional constraints for the optical potential are taken from the analysis of elastic scattering excitation functions at backward angles which are available in literature. Moreover, the variation of the elastic alpha scattering cross sections along the $Z = 48$ isotopic and $N = 62$ isotonic chain is investigated by the study of the ratios of the of $^{106,110,116}$Cd($\\alpha,\\alpha$)$^{106,110,116}$Cd scattering cross sections at E$_{c.m.} \\approx$ 15.6 and 18.8 MeV and the ratio of the $^{110}$Cd($\\alpha,\\alpha$)$^{110}$Cd and $^{112}$Sn($\\alpha,\\alpha$)$^{112}$Sn reaction cross sections at E$_{c.m.} \\approx$ 18.8 MeV, respectively. These ratios are sensitive probes for the alpha-nucleus optical potential parameterizations. The potentials under study are a basic...

  9. Chromium isotope variations

    D'Arcy, Joan Mary

    is incorporated into carbonates. Hence, ancient carbonates can potentially record the Cr isotopic composition (δ53Cr ‰) of seawater in the geological past. Reliable application and interpretation of this proxy requires a detailed knowledge about processes that fractionate Cr on the Earth’s surface...... deposited during the Early Ordovician — a time of known redox instability in ancient oceans – exhibit a significant positive Cr isotope excursion of +0.5‰. This excursion is interpreted as the reductive drawn down of dissolved Cr in seawater in response to the development of a proximal anoxic sink......, and the quantification the Cr isotope composition of major Cr fluxes into and out of ocean. This thesis adds to the current knowledge of the Cr isotope system and is divided into two studies. The focus of the first study was to determine what processes control the Cr isotopic compositionof river water and to quantify...

  10. Isotopes in Greenland Precipitation

    Faber, Anne-Katrine

    Greenland ice cores offer a unique opportunity to investigate the climate system behaviour. The objective of this PhD project is to investigate isotope modelling of present- day conditions and conduct model-data comparison using Greenland ice cores. Thus this thesis investigates how the integration...... of model and data can be used to improve the understanding of climate changes. This is done through analysis of isotope modelling, observations and ice core measurements. This dissertation comprises three projects: (1) Modelling the isotopic response to changes in Arctic sea surface conditions, (2......) Constructing a new Greenland database of observations and present-day ice core measurements, and (3) Performance test of isotope-enabled CAM5 for Greenland. The recent decades of rapid Arctic sea ice decline are used as a basis for an observational-based model experiment using the isotope-enabled CAM model 3...

  11. Refinement of the supercontinent cycle with Hf, Nd and Sr isotopes

    Kent C. Condie


    External and internal orogens show similar patterns in ɛNd and ɛHf with age suggesting that both juvenile and reworked crustal components are produced in both types of orogens with similar proportions. However, both types of orogens clearly produce more juvenile isotopic signatures in retreating mode than in advancing mode. Many secular changes in ɛHf and ɛNd distributions correlate with the supercontinent cycle. Although supercontinent breakup is correlated with short-lived decreasing ɛHf and ɛNd (≤100 Myr for most supercontinents, there is no isotopic evidence for the breakup of the Paleoproterozoic supercontinent Nuna. Assembly of supercontinents by extroversion is recorded by decreasing ɛNd in granitoids and metasediments and decreasing ɛHf in zircons, attesting to the role of crustal reworking in external orogens in advancing mode. As expected, seawater Sr isotopes increase and seawater Nd isotopes decrease during supercontinent assembly by extroversion. Pangea is the only supercontinent that has a clear isotopic record of introversion assembly, during which median ɛNd and ɛHf rise rapidly for ≤100 Myr. Although expected to increase, radiogenic seawater Sr decreases (and seawater Nd increases during assembly of Pangea, a feature that may be caused by juvenile input into the oceans from new ocean ridges and external orogens in retreating mode. The fact that a probable onset of plate tectonics around 3 Ga is not recorded in isotopic distributions may be due the existence of widespread felsic crust formed prior to the onset of plate tectonics in a stagnant lid tectonic regime, as supported by Nd and Hf model ages.

  12. A search for nickel isotopic anomalies in iron meteorites and chondrites

    Chen, J. H.; Papanastassiou, D. A.; Wasserburg, G. J.


    We report Ni isotopic data, for 58,60-62Ni, on (1) FeNi metal and sulfides in different groups of iron meteorites, (2) sulfides and a whole rock sample of the St. Séverin chondrite, and (3) chondrules from the Chainpur chondrite. We have developed improved, Multiple-Collector, Positive ion Thermal Ionization Mass Spectrometric (MC-PTIMS) techniques, with Ni + ionization efficiency at 1‰, and chemical separation techniques for Ni which reduce mass interferences to the 1 ppm level, so that no mass interference corrections need be applied, except for 64Ni (from 64Zn, at the 0.1‰ level), for which we do not report results. We normalize the data to 62Ni/ 58Ni to correct for mass dependent isotope fractionation. No evidence was found for resolved radiogenic or general Ni isotope anomalies at the resolution levels of 0.2 and 0.5 ɛu (ɛu = 0.01%) for 60Ni/ 58Ni and 61Ni/ 58Ni, respectively. From the 56Fe/ 58Ni ratios and ɛ( 60Ni/ 58Ni) values, we calculate upper limits for the initial value of ( 60Fe/ 56Fe) 0 of (a) Toluca and Odessa by Quitté et al. [Quitté G., Meier M., Latkoczy C., Halliday A. N., and Gunther D., (2006). Nickel isotopes in iron meteorites-nucleosynthetic anomalies in sulfides with no effects in metals and no trace of 60Fe. Earth Planet. Sci. Lett. 242, 16-25]. Hence, we find no need for specialized physical-chemical planetary processes for the preservation of different Ni isotope compositions, between FeNi metal and sulfides in the same iron meteorites, as proposed by the above reports nor for complex astrophysical scenarios to provide the very peculiar Ni isotope anomalies reported by these workers for sulfides.

  13. Sr Isotopes at the Onset of the Ice Ages at the Northern Apennines

    Fuchs, Rita; Lazar, Boaz; Angiolini, Lucia; Crippa, Gaia; Stein, Mordechai


    Sr isotopes can be used to constrain the marine Sr budget. The temporal variations in the 87Sr/86Sr ratios (radiogenic Sr) have been reconstructed over the past few decades based on marine macro and micro fossils data (e.g. brachiopods and foraminifera). It is used to constrain the sources and amounts of strontium that dictate the temporal variations in oceanic Sr throughout the Phanerozoic. On the other hand, the study of processes controlling the composition stable Sr isotopes (δ88/86Sr) is very new and only limited research was conducted on this topic during the past few years. Up to date, no δ88/86Sr data are available for considerable parts of Earth's history and the contribution of the potential Sr sources to the oceans is poorly constrained. Here, we set to examine the behavior of radiogenic and stable Sr isotopes in the marine environment of the northern Apennines (Italy) during the time interval of the late Pliocene to early-Middle Pleistocene - upon the onset of ice ages in the northern latitudes. We collected fossil mollusks from outcrops of the Arda and Stirone Rivers that are rich in bivalves, brachiopods, foraminifera (that were used for establishing the chronostratigraphy of the sections) and other genera. Ecological and sedimentological analysis of the section suggest a normal marine environment of depth range of several tens of meters that existed on the southern flanks of the large Po embayment. In order to evaluate the potential of the fossil assemblages in the Arda and Stirone sections to serve as reliable recorders of the marine δ88/86Sr of seawater during the desired period, we examined mineralogical and chemical properties of the fossils (e.g. distribution of trace elements like Sr and Mg in the skeletons, microstructures like secondary fillings of punctate shells in brachiopod) and measured the 87Sr/86Sr ratios. Among the species analyzed, Aequipecten opercularis (bivalve) and Glycymeris inflata (bivalve) have aragonite skeletons that

  14. Systematic review

    Enggaard, Helle


    Title: Systematic review a method to promote nursing students skills in Evidence Based Practice Background: Department of nursing educate students to practice Evidence Based Practice (EBP), where clinical decisions is based on the best available evidence, patient preference, clinical experience...... with systematic review is used to develop didactic practice end evidence based teaching in different part of the education. Findings: The poster will present how teacher’s training and experiences with systematic review contribute to the nursing education in relation to didactic, research methodology and patient...... sources of evidence influence EBP. Furthermore teachers skills in systematic review will be used to develop systematic reviews on topics in the education where there aren’t any in order to promote Evidence Based Teaching....

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

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


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

  16. Hydrogen isotope systematics in C3 and C4 saltmarsh plants: the importance of biochemical processes in controlling interspecies variation in n-alkane 2H/1H composition

    Eley, Y.; Pedentchouk, N.


    Palaeohydrological studies have increasingly utilised the 2H/1H composition of leaf wax n-alkyl lipids to extract information from the geological record. Interpretation of the sedimentary biomarker δ2H signal, however, requires detailed understanding of the mechanisms controlling hydrogen isotope fractionation between source water and n-alkyl lipids (ɛl/w). The existence of large ranges in published n-alkyl δ2H and ɛl/w among modern plant species growing at a single location suggests that the lipid signal incorporated into the sedimentary record could be sensitive to relatively small-scale changes in vegetation assemblages. The mechanisms responsible for these interspecies differences are currently poorly constrained. Previous research has had limited success explaining n-alkyl δ2H by reference to physical processes controlling the movement of water inside/outside and within the leaf, while the relative importance of biochemical processes remains largely unexplored. This project aims to identify the mechanisms controlling interspecies variation in n-alkane 2H/1H among a range of C3 and C4 plants from a Norfolk saltmarsh in the UK. To distinguish between environmental, physical and biochemical controls, we conducted 2H/1H analysis of soil, xylem, and leaf waters and n-alkanes (i) across multiple sampling sites within the marsh, (ii) throughout the 2012 growth season, and (iii) at different times of the day. We also measured the 2H/1H of chloroplast phytol in 7 samples collected at the end of 2012. Leaf wax n-alkane δ2H varied among the sampled species by over 100‰ throughout the 2012 growth season. Environmental processes that could influence control source water 2H/1H did not fully account for this interspecies variation - soil water 2H/1H varied by only 35‰ with marsh sub-environment and exhibited site-specific seasonal shifts by no more than 31‰. Maximum interspecies variation in xylem water was 38‰, while leaf waters differed by only 29‰. We

  17. Shergottite Lead Isotope Signature in Chassigny and the Nakhlites

    Jones, J. H.; Simon, J. I.


    The nakhlites/chassignites and the shergottites represent two differing suites of basaltic martian meteorites. The shergottites have ages less than or equal to 0.6 Ga and a large range of initial Sr-/Sr-86 and epsilon (Nd-143) ratios. Conversely, the nakhlites and chassignites cluster at 1.3-1.4 Ga and have a limited range of initial Sr-87/Sr-86 and epsilon (Nd-143). More importantly, the shergottites have epsilon (W-182) less than 1, whereas the nakhlites and chassignites have epsilon (W-182) approximately 3. This latter observation precludes the extraction of both meteorite groups from a single source region. However, recent Pb isotopic analyses indicate that there may have been interaction between shergottite and nakhlite/chassignite Pb reservoirs.Pb Analyses of Chassigny: Two different studies haveinvestigated 207Pb/204Pb vs. 206Pb/204Pb in Chassigny: (i)TIMS bulk-rock analyses of successive leaches and theirresidue [3]; and (ii) SIMS analysis of individual minerals[4]. The bulk-rock analyses fall along a regression of SIMSplagioclase analyses that define an errorchron that is olderthan the Solar System (4.61±0.1 Ga); i.e., these define amixing line between Chassigny’s principal Pb isotopic components(Fig. 1). Augites and olivines in Chassingy (notshown) also fall along or near the plagioclase regression [4].This agreement indicates that the whole-rock leachateslikely measure indigenous, martian Pb, not terrestrial contamination[5]. SIMS analyses of K-spars and sulfides definea separate, sub-parallel trend having higher 207Pb/206Pbvalues ([4]; Fig. 1). The good agreement between the bulkrockanalyses and the SIMS analyses of plagioclases alsoindicates that the Pb in the K-spars and sulfides cannot be amajor component of Chassigny.The depleted reservoir sampled by Chassigny plagioclaseis not the same as the solar system initial (PAT) andrequires a multi-stage origin. Here we show a two-stagemodel (Fig. 1) with a 238U/204Pb (µ) of 0.5 for 4.5-2.4 Gaand a µ of

  18. The origin of Cenozoic continental basalts in east-central China: Constrained by linking Pb isotopes to other geochemical variables

    Xu, Zheng; Zheng, Yong-Fei; Zhao, Zi-Fu


    Cenozoic continental basalts in east-central China are characterized by OIB-like trace element patterns with more depleted to less enriched Sr-Nd isotope compositions. Such geochemical signatures are attributable to variable contributions to their mantle sources from crustal components in the oceanic subduction zone. A combined study of basalt Pb isotope variations with other geochemical variables indicates that four mantle and crustal components were involved in the basalt petrogenesis. Model calculations verify the geochemical transfer from the subducted crustal components to the mantle sources. The depleted MORB mantle component is indicated by the depleted Sr-Nd isotope compositions of basalts. Relatively high 206Pb/204Pb and low Δ8/4 ratios are ascribed to contributions from the igneous oceanic crust with high U/Pb and low Th/U ratios, low 206Pb/204Pb and high Δ8/4 ratios are ascribed to the lower continental crust, and high 206Pb/204Pb and high Δ8/4 ratios are linked to the seafloor sediment. This generates different compositions of mantle sources for these OIB-like continental basalts. The basalts with the most depleted Sr-Nd isotope compositions show Pb isotope compositions distinct from Pacific MORB but similar to Indian MORB, suggesting the occurrence of Indian type asthenospheric mantle beneath the continental lithosphere of eastern China. The depleted MORB mantle would be metasomatized by the three crustal components at the slab-mantle interface in oceanic subduction channel, generating the mantle sources that are enriched in melt-mobile incompatible trace elements and their pertinent radiogenic isotopes. Nevertheless, the crustal components were not directly incorporated in the forms of crustal rocks into the mantle sources, but underwent partial melting to produce the felsic melts that predominate the composition of those trace elements and their pertinent radiogenic isotopes in the basalts. As such, the depleted MORB mantle component was

  19. Iron and Zinc isotope fractionation during magmatism in the continental crust: Evidence from bimodal volcanic rocks from Hailar basin, NE China

    Xia, Ying; Li, Shuangqing; Huang, Fang


    This study presents Fe-Zn isotope data for a suite of well-characterized bimodal volcanic rocks from Hailar Basin, northeast China to understand the mechanism of Fe isotope fractionation in highly differentiated igneous rocks. The samples range from basaltic trachyandesites to trachytes-rhyodacites, and rhyolites. The δ56Fe values increase with increasing SiO2 contents with the rhyolites having the highest δ56Fe (up to 0.64 ± 0.02‰) among the previously reported data for igneous rocks at a similar SiO2. The lack of correlation between δ56Fe and Rb/La argues against the effect of fluid exsolution on Fe isotopes. The δ56Fe do not show a clear correlation with δ66Zn and radiogenic isotopes, suggesting that thermal diffusion or crustal contamination cannot produce the high δ56Fe in Hailar volcanic rocks. Fe isotopic variation in Hailar volcanic rocks can be explained by two steps of magmatism. During the first step, partial melting of basaltic trachyandesites with an average δ56Fe of 0.09 ± 0.14‰ produced trachytes-rhyodacites with an average δ56Fe of 0.24 ± 0.27‰. Modelling using rhyolite-MELTS shows that Fe isotopes can be fractionated by preferential partitioning of isotopically different Fe3+ and Fe2+ between the solid residue and partial melt. The second step involves formation of rhyolites with significantly high δ56Fe through partial melting or extensive crystallization of crust materials, during which isotopically heavy Fe preferentially partition into the rhyolitic melt. Therefore, fractionation of Fe isotopes between melts and minerals can result in high δ56Fe in SiO2-rich igneous rocks and apparent Fe isotope heterogeneity within the continental crust.

  20. Shape of Te isotopes in mean-field formalism

    T Bayram; A H Yilmaz


    The systematic investigation of ground-state shape evolution from -unstable (6) to spherical (5) for even−even 112-134Te has been presented by using the quadrupole momentconstrained Hartree–Fock–Bogoliubov (HFB) method. By examining potential energy curves of Te isotopes, it has been suggested that 124Te nucleus may hold (5) symmetry.

  1. The 1998-2001 submarine lava balloon eruption at the Serreta ridge (Azores archipelago): Constraints from volcanic facies architecture, isotope geochemistry and magnetic data

    Madureira, Pedro; Rosa, Carlos; Marques, Ana Filipa; Silva, Pedro; Moreira, Manuel; Hamelin, Cédric; Relvas, Jorge; Lourenço, Nuno; Conceição, Patrícia; Pinto de Abreu, Manuel; Barriga, Fernando J. A. S.


    The most recent submarine eruption observed offshore the Azores archipelago occurred between 1998 and 2001 along the submarine Serreta ridge (SSR), 4-5 nautical miles WNW of Terceira Island. This submarine eruption delivered abundant basaltic lava balloons floating at the sea surface and significantly changed the bathymetry around the eruption area. Our work combines bathymetry, volcanic facies cartography, petrography, rock magnetism and geochemistry in order to (1) track the possible vent source at seabed, (2) better constrain the Azores magma source(s) sampled through the Serreta submarine volcanic event, and (3) interpret the data within the small-scale mantle source heterogeneity framework that has been demonstrated for the Azores archipelago. Lava balloons sampled at sea surface display a radiogenic signature, which is also correlated with relatively primitive (low) 4He/3He isotopic ratios. Conversely, SSR lavas are characterized by significantly lower radiogenic 87Sr/86Sr, 206Pb/204Pb and 208Pb/204Pb ratios than the lava balloons and the onshore lavas from the Terceira Island. SSR lavas are primitive, but incompatible trace-enriched. Apparent decoupling between the enriched incompatible trace element abundances and depleted radiogenic isotope ratios is best explained by binary mixing of a depleted MORB source and a HIMU­type component into magma batches that evolved by similar shallower processes in their travel to the surface. The collected data suggest that the freshest samples collected in the SSR may correspond to volcanic products of an unnoticed and more recent eruption than the 1998-2001 episode.

  2. Measurement system analysis (MSA) of the isotopic ratio for uranium isotope enrichment process control

    Medeiros, Josue C. de; Barbosa, Rodrigo A.; Carnaval, Joao Paulo R., E-mail:, E-mail:, E-mail: [Industrias Nucleares do Brasil (INB), Rezende, RJ (Brazil)


    Currently, one of the stages in nuclear fuel cycle development is the process of uranium isotope enrichment, which will provide the amount of low enriched uranium for the nuclear fuel production to supply 100% Angra 1 and 20% Angra 2 demands. Determination of isotopic ration n({sup 235}U)/n({sup 238}U) in uranium hexafluoride (UF{sub 6} - used as process gas) is essential in order to control of enrichment process of isotopic separation by gaseous centrifugation cascades. The uranium hexafluoride process is performed by gas continuous feeding in separation unit which uses the centrifuge force principle, establishing a density gradient in a gas containing components of different molecular weights. The elemental separation effect occurs in a single ultracentrifuge that results in a partial separation of the feed in two fractions: an enriched on (product) and another depleted (waste) in the desired isotope ({sup 235}UF{sub 6}). Industrias Nucleares do Brasil (INB) has used quadrupole mass spectrometry (QMS) by electron impact (EI) to perform isotopic ratio n({sup 235}U)/n({sup 238}U) analysis in the process. The decision of adjustments and change te input variables are based on the results presented in these analysis. A study of stability, bias and linearity determination has been performed in order to evaluate the applied method, variations and systematic errors in the measurement system. The software used to analyze the techniques above was the Minitab 15. (author)

  3. Source and magmatic evolution inferred from geochemical and Sr-O-isotope data on hybrid lavas of Arso, the last eruption at Ischia island (Italy; 1302 AD)

    Iovine, Raffaella Silvia; Mazzeo, Fabio Carmine; Arienzo, Ilenia; D'Antonio, Massimo; Wörner, Gerhard; Civetta, Lucia; Pastore, Zeudia; Orsi, Giovanni


    Geochemical and isotopic (87Sr/86Sr and 18O/16O) data have been acquired on whole rock and separated mineral samples from volcanic products of the 1302 AD Arso eruption, Ischia volcanic island (Gulf of Naples, Southern Italy), to investigate magmatic processes. Our results highlight petrographic and isotopic disequilibria between phenocrysts and their host rocks. Similar disequilibria are observed also for more mafic volcanic rocks from Ischia and in the Phlegraean Volcanic District in general. Moreover, 87Sr/86Sr and 18O/16O values suggest mixing between chemically and isotopically distinct batches of magma, and crystals cargo from an earlier magmatic phase. The radiogenic Sr isotope composition suggests that the mantle source was enriched by subduction-derived sediments. Furthermore, magmas extruded during the Arso eruption were affected by crustal contamination as suggested by high oxygen isotope ratios. Assimilation and fractional crystallization modelling of the Sr-O isotope compositions indicates that not more than 7% of granodioritic rocks from the continental crust have been assimilated by a mantle-derived mafic magma. Hence the recent volcanic activity of Ischia has been fed by distinct batches of magma, variably contaminated by continental crust, that mixed during their ascent towards the surface and remobilized phenocrysts left from earlier magmatic phases.

  4. An isotopic perspective on growth and differentiation of Proterozoic orogenic crust: From subduction magmatism to cratonization

    Johnson, Simon P.; Korhonen, Fawna J.; Kirkland, Christopher L.; Cliff, John B.; Belousova, Elena A.; Sheppard, Stephen


    The in situ chemical differentiation of continental crust ultimately leads to the long-term stability of the continents. This process, more commonly known as 'cratonization', is driven by deep crustal melting with the transfer of those melts to shallower regions resulting in a strongly chemically stratified crust, with a refractory, dehydrated lower portion overlain by a complementary enriched upper portion. Since the lower to mid portions of continental crust are rarely exposed, investigation of the cratonization process must be through indirect methods. In this study we use in situ Hf and O isotope compositions of both magmatic and inherited zircons from several felsic magmatic suites in the Capricorn Orogen of Western Australia to highlight the differentiation history (i.e. cratonization) of this portion of late Archean to Proterozoic orogenic crust. The Capricorn Orogen shows a distinct tectonomagmatic history that evolves from an active continental margin through to intracratonic reworking, ultimately leading to thermally stable crust that responds similarly to the bounding Archean Pilbara and Yilgarn Cratons. The majority of magmatic zircons from the main magmatic cycles have Hf isotopic compositions that are generally more evolved than CHUR, forming vertical arrays that extend to moderately radiogenic compositions. Complimentary O isotope data, also show a significant variation in composition. However, combined, these data define not only the source components from which the magmas were derived, but also a range of physio-chemical processes that operated during magma transport and emplacement. These data also identify a previously unknown crustal reservoir in the Capricorn Orogen.

  5. Major element composition of an Early Enriched Reservoir: constraints from 142Nd/144Nd isotope systematics in the early Earth and high-pressure melting experiments of a primitive peridotite

    Kondo, Nozomi; Yoshino, Takashi; Matsukage, Kyoko N.; Kogiso, Tetsu


    The Accessible Silicate Earth (ASE) has a higher 142Nd/144Nd ratio than most chondrites. Thus, if the Earth is assumed to have formed from these chondrites, a complement low-142Nd/144Nd reservoir is needed. Such a low-142Nd/144Nd reservoir is believed to have been derived from a melt in the early Earth and is called the Early Enriched Reservoir (EER). Although the major element composition of the EER is crucial for estimating its chemical and physical properties (e.g., density) and is also essential for understanding the origin and fate of the EER, which are both major factors that determine the present composition of the Earth, it has not yet been robustly established. In order to determine the major element composition of the EER, we estimated the age and pressure-temperature conditions to form the EER that would best explain its Nd isotopic characteristics, based on Sm-Nd partitioning and its dependence on pressure, temperature, and melting phase relations. Our estimate indicates that the EER formed within 33.5 Myr of Solar System formation and at near-solidus temperatures and shallow upper-mantle pressures. We then performed high-pressure melting experiments on primitive peridotite to determine the major element composition of the EER at estimated temperature at 7 GPa and calculated the density of the EER. The result of our experiments indicates that the near-solidus melt is iron-rich komatiite. The estimated density of the near-solidus melt is lower than that of the primitive peridotite, suggesting that the EER melt would have ascended in the mantle to form an early crust. Given that high mantle potential temperatures are assumed to have existed in the Hadean, it follows that the EER melt was generated at high pressure and, therefore, its composition would have been picritic to komatiitic. As the formation age of the EER estimated in our study precedes the last giant, lunar-forming impact, the picritic to komatiitic crust (EER) would most likely have been

  6. Stable isotopic signature of Australian monsoon controlled by regional convection

    Zwart, C.; Munksgaard, N. C.; Kurita, N.; Bird, M. I.


    The aim of this study was to identify the main meteorological drivers of rainfall isotopic variation in north Australia in order to improve the interpretation of isotopic proxy records in this region. An intense monitoring program was conducted during two monsoonal events that showed significant and systematic isotopic change over time. The results showed a close link between isotopic variation in precipitation and variability in monsoon conditions, associated with the presence of large convective envelopes propagating through the study site. The largest negative amplitudes in the isotopic signal were observed when eastward and westward moving precipitation systems within the convective envelope merged over the measurement site. This suggests that the amplitude of the isotopic signal is related to the size and activity of the convective envelope. The strong correlation between rainfall isotopic variation, regional outgoing longwave radiation and regional rainfall amount supports this conclusion. This is further strengthened by the strong relationship between isotopic variation and the integrated rainfall history of air masses prior to arriving at the measurement locations. A local amount effect was not significant and these findings support the interpretation of δ18O as proxy for regional climatic conditions rather than local rainfall amount. Meteorological parameters that characterize intra-seasonal variability of monsoon conditions were also found to be strongly linked to inter-seasonal variability of the monthly based δ18O values in the Global Network of Isotopes in Precipitation (GNIP) database. This leads to the conclusion that information about the Australian monsoon variability can likely be inferred from the isotopic proxy record in North Australia on short (intra seasonal) and long (inter seasonal or longer) timescales.

  7. Isotopes in Greenland Precipitation

    Faber, Anne-Katrine

    the Arctic Ocean. A comprehensive database is created based on ice core and weather station data from Greenland within the period 1890-2014. Present day annual and seasonal mean values are computed for 326 locations in Greenland. Parameterization of the spatial distribution of temperature and δ18O are used...... of model and data can be used to improve the understanding of climate changes. This is done through analysis of isotope modelling, observations and ice core measurements. This dissertation comprises three projects: (1) Modelling the isotopic response to changes in Arctic sea surface conditions, (2......) Constructing a new Greenland database of observations and present-day ice core measurements, and (3) Performance test of isotope-enabled CAM5 for Greenland. The recent decades of rapid Arctic sea ice decline are used as a basis for an observational-based model experiment using the isotope-enabled CAM model 3...

  8. Isotope Production Facility (IPF)

    Federal Laboratory Consortium — The Los Alamos National Laboratory has produced radioactive isotopes for medicine and research since the mid 1970s, when targets were first irradiated using the 800...

  9. Calcium stable isotope geochemistry

    Gausonne, Nikolaus [Muenster Univ. (Germany). Inst. fuer Mineralogie; Schmitt, Anne-Desiree [Strasbourg Univ. (France). LHyGeS/EOST; Heuser, Alexander [Bonn Univ. (Germany). Steinmann-Inst. fuer Geologie, Mineralogie und Palaeontologie; Wombacher, Frank [Koeln Univ. (Germany). Inst. fuer Geologie und Mineralogie; Dietzel, Martin [Technische Univ. Graz (Austria). Inst. fuer Angewandte Geowissenschaften; Tipper, Edward [Cambridge Univ. (United Kingdom). Dept. of Earth Sciences; Schiller, Martin [Copenhagen Univ. (Denmark). Natural History Museum of Denmark


    This book provides an overview of the fundamentals and reference values for Ca stable isotope research, as well as current analytical methodologies including detailed instructions for sample preparation and isotope analysis. As such, it introduces readers to the different fields of application, including low-temperature mineral precipitation and biomineralisation, Earth surface processes and global cycling, high-temperature processes and cosmochemistry, and lastly human studies and biomedical applications. The current state of the art in these major areas is discussed, and open questions and possible future directions are identified. In terms of its depth and coverage, the current work extends and complements the previous reviews of Ca stable isotope geochemistry, addressing the needs of graduate students and advanced researchers who want to familiarize themselves with Ca stable isotope research.

  10. Isotopically controlled semiconductors

    Haller, E.E.


    A review of recent research involving isotopically controlled semiconductors is presented. Studies with isotopically enriched semiconductor structures experienced a dramatic expansion at the end of the Cold War when significant quantities of enriched isotopes of elements forming semiconductors became available for worldwide collaborations. Isotopes of an element differ in nuclear mass, may have different nuclear spins and undergo different nuclear reactions. Among the latter, the capture of thermal neutrons which can lead to neutron transmutation doping, can be considered the most important one for semiconductors. Experimental and theoretical research exploiting the differences in all the properties has been conducted and will be illustrated with selected examples. Manuel Cardona, the longtime editor-in-chief of Solid State Communications has been and continues to be one of the major contributors to this field of solid state physics and it is a great pleasure to dedicate this review to him.

  11. Isotopes through the looking glass

    Mårtensson Pendrill, Ann Marie


    Nuclear distributions affect many aspects of atomic spectra. As an example, recent experimental results for the hyperfine anomaly in Fr isotopes are considered. These depend on nuclear charge and magnetization distributions. The variations in charge radii for these isotopes were studied earlier by measuring optical isotope shifts. The hyperfine anomalies for the odd-odd isotopes involve the neutron distributions, of interest for studies of parity nonconserving effects along a chain of isotopes.

  12. Boron and strontium isotope ratios and major/trace elements concentrations in tea leaves at four major tea growing gardens in Taiwan.

    Chang, Cheng-Ta; You, Chen-Feng; Aggarwal, Suresh Kumar; Chung, Chuan-Hsiung; Chao, Hung-Chun; Liu, Hou-Chun


    Isotopic compositions of B and Sr in rocks and sediments can be used as tracers for plant provincial sources. This study aims to test whether tea leaf origin can be discriminated using (10)B/(11)B and Sr isotopic composition data, along with concentrations of major/trace elements, in tea specimens collected from major plantation gardens in Taiwan. The tea leaves were digested by microwave and analyzed by multi-collector inductively coupled plasma mass spectrometry (MC-ICPMS). The data showed significant variations in (87)Sr/(86)Sr ratios (from 0.70482 to 0.71462), which reflect changes in soil, groundwater or irrigation conditions. The most radiogenic tea leaves were found at the Taitung garden and the least radiogenic ones were from the Hualien garden. The δ (11)B was found to change appreciably (δ (11)B = 0.38-23.73 ‰) which could be due to fertilizers. The maximum δ (11)B was also observed in tea samples from the Hualien garden. Principal component analysis combining (87)Sr/(86)Sr, δ (11)B and major/trace elements results successfully discriminated different sources of major tea gardens in Taiwan, except the Hualien gardens, and this may be due to rather complicated local geological settings.

  13. Methods of isotopic geochronology

    Gorokhov, I. M.; Levchenkov, O. A.

    Papers are presented on such topics as the age of the chemical elements; the age of meteorites, the moon, and the earth; isotopic ages of the most ancient terrestrial formations; and the Archean evolution of Enderby Land in the Antarctic as evidenced by isotopic dating. Consideration is also given to a uranium-lead geochronology technique for investigating Precambrian ore deposits, a Pb-Pb technique of zircon dating, and the potentials and limitations of Sm-Nd geochronology.

  14. 40Ar/ 39Ar systematics and argon diffusion in amber: implications for ancient earth atmospheres

    Landis, G. P.; Snee, L. W.


    Argon isotope data indicate retained argon in bulk amber (matrix gas) is radiogenic [ 40Ar/ 39Ar ≃32o] than the much more abundant surface absorbed argon [ 40Ar/ 39Ar ≃295.5]. Neutron-induced 39Ar is retained in amber during heating experiments to 150° -250°C, with no evidence of recoiled 39Ar found after irradiation. A maximum permissible volume diffusion coefficient of argon in amber (at ambient temperature) D≤1.5 x 10 -17 cm 2S -1 is calculated from 39Ar retention. 40Ar/ 39Ar age calculations indicate Dominican Republic amber is ≃ 45 Ma and North Dakota amber is ≃ 89 Ma, both at least reasonable ages for the amber based upon stratigraphic and paleontological constraints and upon the small amount of radiogenic 40Ar. To date, over 300 gas analyses of ambers and resins of Cretaceous to Recent age that are geographically distributed among fifteen noted world locations identify mixtures of gases in different sites within amber (Berner and Landis, 1988). The presence of multiple mixing trends between compositionally distinct end-members gases within the same sample and evidence for retained radiogenic argon within the amber argue persuasivley against rapid exchange by diffusion of amber-contained gases with moder air. Only gas in primary bubbles entrapped between successive flows of tree resin has been interpreted as original "ancient air", which is an O 2-rich end-member gas with air-like N 2/Ar ratios. Gas analyses of these primary bubbles indicate atmospheric O 2 levels in the Late Cretaceous of ≃ 35%, and that atmospheric O 2 dropped by early Tertiary time to near a present atmospheric level of 21% O 2. A very low argon diffusion coefficient in amber persuasively argues for a gas in primary bubbles trapped in amber being ancient air (possibly modified only by O 2 reaction with amber).

  15. Geochemical and Sr-Nd-Pb isotopic evidence for ancient lower continental crust beneath the Xi Ujimqin area of NE China

    Gao, Xiaofeng; Guo, Feng; Xiao, Peixi; Kang, Lei; Xi, Rengang


    The Central Asian Orogenic Belt (CAOB) is the largest Phanerozoic accretionary orogen on Earth. The role that Precambrian continental microblocks played in its formation, however, remains a highly controversial topic. New zircon U-Pb age data and whole-rock geochemical and Sr-Nd-Pb isotopic studies on Permian (253-251 Ma) andesites from the Xi Ujimqin area provide the first evidence for the existence of a continental lower mafic crust in the eastern segment of the CAOB. These Permian lavas generally have chemical compositions similar to experimental melts of garnet pyroxenites. Based on Sr-Nd-Pb isotopic compositional differences, they can be further subdivided into two groups. Group 1 has moderately radiogenic Sr (87Sr/86Sr(i) = 0.7060-0.7062) and nonradiogenic Nd (εNd(t) = - 9.0-8.3) and Pb (e.g., 206Pb/204Pb = 17.18-17.23) isotopic compositions similar to the ancient lower mafic crust beneath the North China Craton (NCC). Compared with Group 1, Group 2 has less radiogenic Sr (87Sr/86Sr(i) = 0.7051-0.7055), and more radiogenic Nd (εNd(t) = - 0.2-+1.4) and Pb (e.g., 206Pb/204Pb = 18.04-18.20) isotopic compositions as observed in the Phanerozoic granitoids and felsic lavas of the CAOB. The combined geochemical and isotopic data indicate that Group 1 was derived from ancient lower mafic crust of the NCC affinity, with a residual assemblage of pyroxene + plagioclase + amphibole. The source for Group 2 was a mixture of ancient lower mafic crust and a juvenile crustal component, and melting left a residue of orthopyroxene + clinopyroxene + plagioclase + garnet + amphibole. Generation of these two types of late Permian andesites favors a model whereby breakoff of a subducted slab and subsequent lithospheric extension triggered extensive asthenospheric upwelling and melting of the continental mafic lower crust of the eastern CAOB. The discovery of ancient lower continental crust of the NCC affinity in the CAOB implies that the NCC experienced continental breakup during

  16. Oxygen Isotopes in Meteorites

    Clayton, R. N.


    Oxygen isotope abundance variations in meteorites are very useful in elucidating chemical and physical processes that occurred during the formation of the solar system (Clayton, 1993). On Earth, the mean abundances of the three stable isotopes are 16O: 99.76%, 17O: 0.039%, and 18O: 0.202%. It is conventional to express variations in abundances of the isotopes in terms of isotopic ratios, relative to an arbitrary standard, called SMOW (for standard mean ocean water), as follows:The isotopic composition of any sample can then be represented by one point on a "three-isotope plot," a graph of δ17O versus δ18O. It will be seen that such plots are invaluable in interpreting meteoritic data. Figure 1 shows schematically the effect of various processes on an initial composition at the center of the diagram. Almost all terrestrial materials lie along a "fractionation" trend; most meteoritic materials lie near a line of "16O addition" (or subtraction). (4K)Figure 1. Schematic representation of various isotopic processes shown on an oxygen three-isotope plot. Almost all terrestrial materials plot along a line of "fractionation"; most primitive meteoritic materials plot near a line of "16O addition." The three isotopes of oxygen are produced by nucleosynthesis in stars, but by different nuclear processes in different stellar environments. The principal isotope, 16O, is a primary isotope (capable of being produced from hydrogen and helium alone), formed in massive stars (>10 solar masses), and ejected by supernova explosions. The two rare isotopes are secondary nuclei (produced in stars from nuclei formed in an earlier generation of stars), with 17O coming primarily from low- and intermediate-mass stars (shielding in the UV photodissociation of CO (van Dishoeck and Black, 1988). This process results from the large differences in abundance between C16O, on the one hand, and C17O and C18O on the other. Photolysis of CO occurs by absorption of stellar UV radiation in the

  17. Zircon ages, geochemistry and Nd isotopic systematics for the Palaeoproterozoic 2.3-1.8 Ga Kuilyu Complex, East Kyrgyzstan - The oldest continental basement fragment in the Tianshan orogenic belt

    Kröner, A.; Alexeiev, D. V.; Kovach, V. P.; Rojas-Agramonte, Y.; Tretyakov, A. A.; Mikolaichuk, A. V.; Xie, H.; Sobel, E. R.


    Precambrian microcontinents represent key tectonic units in the accretionary collages of the western Central Asian Orogenic Belt (CAOB), and their geological history is reasonably well established since the Mesoproterozoic but remains weakly constrained for older epochs due to a scarcity of exposed Palaeoproterozoic and Archaean rocks. Early Precambrian rocks were previously reported from several metamorphic complexes in the Kyrgyz Tianshan orogenic belt, mainly based on multigrain conventional zircon dating, but the present study only confirmed such rocks at one site, namely in the Kuilyu Complex of eastern Kyrgyzstan. New single grain SHRIMP II zircon ages, geochemical data, and whole-rock Nd isotopic compositions for granitoid gneisses of the Kuilyu Complex elucidate the age, origin and tectonic settings of this oldest continental fragment in the Tianshan. The Kuilyu Complex is part of the basement in the Ishim - Middle Tianshan microcontinent. It consist of a strongly deformed and metamorphosed supracrustal assemblage of paragneisses and schists which are tectonically interlayered with amphibolites, migmatites and granitoid gneisses. Our zircon dating indicates that the Kuilyu Complex contains two suites of Palaeoproterozoic granitoid gneisses with magmatic protolith ages of ca. 2.32-2.33 Ga and 1.85 Ga. Granitoid magmatism at 1.85 Ga was almost immediately followed by amphibolite-facies metamorphism at ca 1.83 Ga, evidenced by growth of metamorphic zircon rims. The older, ca 2.3 Ga granitoid gneisses chemically correspond to calc-alkaline, metaluminous, I-type magnesian quartz diorite and granodiorite. The protolith of the younger, ca. 1.85 Ga granite-gneiss is an alkalic-calcic, metaluminous to peraluminous, ferroan medium-grained porphyric granite with chemical features resembling A-type granites. The 2.3 Ga and 1.85 Ga granitoid gneisses have slightly to distinctly negative initial εNd values of -1.2 and -6.6, and similar depleted mantle Nd model ages of 2

  18. The effects of magmatic processes and crustal recycling on the molybdenum stable isotopic composition of Mid-Ocean Ridge Basalts

    Bezard, Rachel; Fischer-Gödde, Mario; Hamelin, Cédric; Brennecka, Gregory A.; Kleine, Thorsten


    Molybdenum (Mo) stable isotopes hold great potential to investigate the processes involved in planetary formation and differentiation. However their use is currently hampered by the lack of understanding of the dominant controls driving mass-dependent fractionations at high temperature. Here we investigate the role of magmatic processes and mantle source heterogeneities on the Mo isotope composition of Mid-Ocean Ridges Basalts (MORBs) using samples from two contrasting ridge segments: (1) the extremely fast spreading Pacific-Antarctic (66-41°S) section devoid of plume influence and; (2) the slow spreading Mohns-Knipovich segment (77-71°N) intercepted by the Jan Mayen Plume (71°N). We show that significant variations in Mo stable isotope composition exist in MORBs with δ98/95Mo ranging from - 0.24 ‰ to + 0.15 ‰ (relative to NIST SRM3134). The absence of correlation between δ98/95Mo and indices of magma differentiation or partial melting suggests a negligible impact of these processes on the isotopic variations observed. On the other hand, the δ98/95Mo variations seem to be associated with changes in radiogenic isotope signatures and rare earth element ratios (e.g., (La/Sm)N), suggesting mantle source heterogeneities as a dominant factor for the δ98/95Mo variations amongst MORBs. The heaviest Mo isotope compositions correspond to the most enriched signatures, suggesting that recycled crustal components are isotopically heavy compared to the uncontaminated depleted mantle. The uncontaminated depleted mantle shows slightly sub-chondritic δ98/95Mo, which cannot be produced by core formation and, therefore, more likely result from extensive anterior partial melting of the mantle. Consequently, the primitive δ98/95Mo composition of the depleted mantle appears overprinted by the effects of both partial melting and crustal recycling.

  19. Isotopic evidence for Last Glacial climatic impacts on Neanderthal gazelle hunting territories at Amud Cave, Israel.

    Hartman, Gideon; Hovers, Erella; Hublin, Jean-Jacques; Richards, Michael


    The Middle Paleolithic site of Amud Cave, Israel, was occupied by Neanderthals at two different time periods, evidenced by two chronologically and stratigraphically distinct depositional sub-units (B4 and B2/B1) during MIS 4 and MIS 3, respectively. The composition of both hunted large fauna and naturally-deposited micromammalian taxa is stable at the site over time, despite a ∼ 10 ky gap between the two occupation phases. However, while gazelle is the most ubiquitous hunted species throughout the occupation, isotopic analysis showed that there is a marked change in Neanderthal hunting ranges between the early (B4) and late (B2/B1) phases. Hunting ranges were reconstructed by comparing oxygen, carbon, and strontium isotopes from gazelle tooth enamel with modern isotope data from the Amud Cave region. This region is characterized by extensive topographic, lithological, and pedological heterogeneity. During the early occupation phase negative oxygen isotope values, low radiogenic (87)Sr/(86)Sr ratios, and low Sr concentrations reveal restricted gazelle hunting in the high elevations west of Amud Cave. In the late occupation phase, hunting ranges became more diverse, but concentrate at low elevations closer to the site. Climatic proxies indicate that conditions were drier in the early occupation phase, which may have pushed gazelle populations into higher, more productive foraging areas. This study showed that Neanderthals adjusted their hunting territories considerably in relation to varying environmental conditions over the course of occupation in Amud Cave. It highlights the utility of multiple isotope analysis in enhancing the resolution of behavioral interpretations based on faunal remains and in reconstructing past hunting behaviors of Paleolithic hominins.

  20. A Review of Mg Isotope Analytical Methods by MC-ICP-MS

    Yajun An; Fang Huang


    Application of multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) has led to big breakthrough of analytical methods for metal stable isotopes, resulting in rapid progresses in non-traditional stable isotope geochemistry. As a new geological tracer, Mg isotopes have been widely applied in studies of almost all important disciplines of geochemistry. High precision Mg isotope data measured by MC-ICP-MS are now available with precision about 0.05‰ amu-1 (2SD) or better. Because mass bias caused by chemical procedure and instrument can easily cause significant analytical error, it is still a challenge to obtain accurate Mg isotope data for natural samples. In this paper, we systematically review the development of analytical technique of Mg isotopes, with a detailed description of a series of important techniques used in the measurement process, including calibration of instrumental mass-bias, chemical purification process, matrix effect, and pitfalls for high precision isotope analyses. We compare standard data from different labs and establish a guideline for Mg iso-tope analysis procedure. Additionally, we briefly discuss the behaviors of Mg isotopes during geological processes including equilibrium and kinetic Mg isotope fractionations, such as magma differentiation, chemical and thermal diffusion, and continental weathering. Finally, we propose some future prospects for Mg isotope geochemistry in both high and low temperature geological processes.

  1. Ground water recharge and flow characterization using multiple isotopes.

    Chowdhury, Ali H; Uliana, Matthew; Wade, Shirley


    Stable isotopes of delta(18)O, delta(2)H, and (13)C, radiogenic isotopes of (14)C and (3)H, and ground water chemical compositions were used to distinguish ground water, recharge areas, and possible recharge processes in an arid zone, fault-bounded alluvial aquifer. Recharge mainly occurs through exposed stream channel beds as opposed to subsurface inflow along mountain fronts. This recharge distribution pattern may also occur in other fault-bounded aquifers, with important implications for conceptualization of ground water flow systems, development of ground water models, and ground water resource management. Ground water along the mountain front near the basin margins contains low delta(18)O, (14)C (percent modern carbon [pmC]), and (3)H (tritium units [TU]), suggesting older recharge. In addition, water levels lie at greater depths, and basin-bounding faults that locally act as a flow barrier may further reduce subsurface inflow into the aquifer along the mountain front. Chemical differences in ground water composition, attributed to varying aquifer mineralogy and recharge processes, further discriminate the basin-margin and the basin-center water. Direct recharge through the indurated sandstones and mudstones in the basin center is minimal. Modern recharge in the aquifer is mainly through the broad, exposed stream channel beds containing coarse sand and gravel where ground water contains higher delta(18)O, (14)C (pmC), and (3)H (TU). Spatial differences in delta(18)O, (14)C (pmC), and (3)H (TU) and occurrences of extensive mudstones in the basin center suggest sluggish ground water movement, including local compartmentalization of the flow system.

  2. Isotope geochemistry reveals ontogeny of dispersal and exchange between main-river and tributary habitats in smallmouth bass Micropterus dolomieu.

    Humston, R; Doss, S S; Wass, C; Hollenbeck, C; Thorrold, S R; Smith, S; Bataille, C P


    Radiogenic strontium isotope ratios ((87) Sr:(86) Sr) in otoliths were compared with isotope ratios predicted from models and observed in water sampling to reconstruct the movement histories of smallmouth bass Micropterus dolomieu between main-river and adjacent tributary habitats. A mechanistic model incorporating isotope geochemistry, weathering processes and basin accumulation reasonably predicted observed river (87) Sr:(86) Sr across the study area and provided the foundations for experimental design and inferring fish provenance. Exchange between rivers occurred frequently, with nearly half (48%) of the 209 individuals displaying changes in otolith (87) Sr:(86) Sr reflecting movement between isotopically distinct rivers. The majority of between-river movements occurred in the first year and often within the first few months of life. Although more individuals were observed moving from the main river into tributaries, this pattern did not necessarily reflect asymmetry in exchange. Several individuals made multiple movements between rivers over their lifetimes; no patterns were found, however, that suggest seasonal or migratory movement. The main-river sport fishery is strongly supported by recruitment from tributary spawning, as 26% of stock size individuals in the main river were spawned in tributaries. The prevailing pattern of early juvenile dispersal documented in this study has not been observed previously for this species and suggests that the process of establishing seasonal home-range areas occurs up to 2 years earlier than originally hypothesized. Extensive exchange between rivers would have substantial implications for management of M. dolomieu populations in river-tributary networks.

  3. Isotope and elemental geochemistry of Cretaceous fossiliferous concretions (Santana Formation, Brazil)

    Heimhofer, Ulrich; Meister, Patrick; Bernasconi, Stefano M.; Ariztegui, Daniel; Martill, David M.; Schwark, Lorenz


    Exceptional three-dimensional fossil preservation (incl. phosphatization of soft-tissues) within organic carbon-rich mudstones is often associated with the formation of a protective carbonate shell surrounding the fossil specimen. Examples for this type of preservation are the Early Cretaceous fishes, turtles and pterosaurs from the Brazilian Santana Formation. Numerous studies proposed different conceptual models for concretion formation. Having new state-of-the-art geochemical tools at hand we revisited these models for the Santana Formation as an exemplary case. Differential compaction clearly indicates early precipitation of micritic calcite surrounding a central cavity containing the still decomposing fossil. The presence of pyrite forming a circular rim around the fossil and carbonate with negative carbon isotope compositions suggest intense sulphate reduction whereby the production of ammonium from the decay of proteins led to an increased alkalinity, which induced early carbonate precipitation. By means of micro-XRF scanning we found that pyrite is absent from the interior part of the concretions and that total iron content is very low, which indicate absence of sulphate reduction at the center of the concretions and possibly local onset of methanogenesis. We postulate that the central cavity may even have been filled with methane gas that evolved from the decaying animal. Methane diffusing outward was anaerobically oxidized in the surrounding sulphate reduction zone. Carbonate clumped isotopes revealed that micritic calcite formed early, but that these early precipitates are overprinted by two different late diagenetic cements precipitated at elevated temperatures. The occurrence of an outermost "cone-in-cone" calcite rim can be associated with burial showing temperatures of up to 60°C. Strontium-isotope ratios of matrix calcite and cement phases show radiogenic values (0.710416 to 0.712465), which are significantly higher than typical marine Cretaceous

  4. Molybdenum isotope fractionation in the mantle

    Liang, Yu-Hsuan; Halliday, Alex N.; Siebert, Chris; Fitton, J. Godfrey; Burton, Kevin W.; Wang, Kuo-Lung; Harvey, Jason


    concentrations of all the ultramafic xenoliths of 40-400 ppb, similar to or, significantly higher than, current estimates for the BSE (39 ppb). On this basis a revised best estimate of the Mo content in the BSE based on these concentrations would be in the range 113-180 ppb, significantly higher than previously assumed. These values are similar to the levels of depletion in the other refractory moderately siderophile elements W, Ni and Co. A simpler explanation may be that the subcontinental lithospheric mantle has been selectively enriched in Mo leading to the higher concentrations observed. Cryptic melt metasomatism would be difficult to reconcile with the high Mo/Ce of the most LREE depleted xenoliths. Ancient Mo-enriched subducted components would be expected to have heavy δ98/95Mo, which is not observed. The Mo isotope composition of the BSE, cannot be reliably resolved from that of chondrites at this time despite experimental evidence for metal-silicate fractionation. An identical isotopic composition might result from core-mantle differentiation under very high temperatures such as were associated with the Moon-forming Giant Impact, or from the BSE inventory reflecting addition of moderately siderophile elements from an oxidised Moon-forming impactor (O'Neill, 1991). However, the latter would be inconsistent with the non-chondritic radiogenic W isotopic composition of the BSE. Based on mantle fertility arguments, Mo in the BSE could even be lighter (lower 98/95Mo) than that in chondrites, which might be explained by loss of S rich liquids from the BSE during core formation (Wade et al., 2012). Such a late removal model is no longer required to explain the Mo concentration of the BSE if its abundance is in fact much higher, and similar to the values for ultramafic xenoliths.

  5. Isotopic disequilibrium and lower crustal contamination in slowly ascending magmas: Insights from Proterozoic anorthosites

    Bybee, G. M.; Ashwal, L. D.


    disequilibrium geometries cannot be explained by melting of the lower crust. Assimilation of crust with distinctive Sr, Nd and Pb isotopic compositions does, however, explain the origin of decoupling in internal mineral isotopic compositions. We also find unexpected patterns of internal isotopic disequilibrium, such as isotopically radiogenic orthopyroxene relative to plagioclase and differences in plagioclase isotopic disequilibrium between orthopyroxene- and olivine-bearing samples. These various lines of evidence provide strong support for the generation of crustal isotopic signatures through assimilation, and not anatexis, of the lower crust. These isotopic data show that anorthosite petrogenesis likely involves significant differentiation and solidification at lower crustal depths, followed by ascent of high-crystallinity bodies (⩾50% crystallinity) to mid- or upper crustal levels. We show that protracted lower crustal differentiation imparts a clear chemical and isotopic signature on mantle-derived magmas of Proterozoic anorthosites and that this process is central in the development of such slowly ascending, plagioclase-rich magmas.

  6. Phanerozoic and Neoproterozoic Negative Carbon Isotope Excursions, Diagenesis and Terrestrialization

    Paul, K.; Kennedy, M. J.


    Comprehensive data sets of Phanerozoic and late Precambrian carbon isotope data derived from carbonate rocks show a similar positive relation when cross-plotted with oxygen isotope values. The range and slope between the time periods is identical and the processes responsible for the relation have been well documented in Quaternary sediments. These processes include the stabilization of isotope values to ambient meteoric water values during shallow burial and flushing of carbonate sediments. Both data sets show strongly depleted carbon (-9 per mil PDB) and oxygen isotope values that retain seemingly systematic stratigraphic patterns with the Quaternary and Phanerozoic examples that demonstrably record meteroric water values. Similar values and patterns in the Precambrian are interpreted as primary marine in origin with significant implications for an ocean carbon mass balance not possible in the Phanerozoic carbon cycle. A similar compilation of carbonates older than one billion years do not show a relation between carbon and oxygen isotopes, lacking the negative carbon values evident in the younger record. We hypothesize that this difference records the onset of significant organic carbon on the land surface and the alteration of meteoric waters toward Phanerozoic values. We demonstrate the meteoric affinities of Neoproterozoic carbonates containing prominent negative isotope excursions recorded in the Shuram and Wonoka Formations of Oman and South Australia commonly attributed to whole ocean isotope variation. The conspicuous absence of negative carbon isotope values with normal marine oxygenisotope values in the Phanerozoic and Neoproterozic identifies a consistent relation between these time intervals and suggests that, as well accepted in the Phanerozoic, negative carbon isotope excursions less than -3 per mil are not a record of marine processes, but rather the later terrestrial biotic influence on meteoric water values.

  7. Systematic measurements of the Bohr-Weisskopf effect at ISOLDE

    Nojiri, Y; Matsuki, S; Ragnarsson, I; Neugart, R; Redi, O; Stroke, H H; Duong, H T; Marescaux, D; Pinard, J; Juncar, P; Ekstrom, C; Pellarin, M; Vialle, J-L; Inamura, T


    The " Bohr-Weisskopf " effect, or " hyperfine structure (hfs) anomaly ", which results from the effect of the distribution of nuclear magnetization on the electro-nuclear interaction, will be measured systematically at the PS Booster ISOLDE, first for a long chain of radioactive cesium isotopes, analogously to previous isotope shift and hfs studies. In addition to the direct measurement of magnetic moment values, the results are expected to provide independent data for testing nuclear wavefunctions, these will be of importance for interpreting systematic parity non-conservation experiments, complementary to the single isotope study which requires a high precision knowledge of the electron wavefunction. Substantial progress in these calculations has been achieved recently. Precision measurements of the hfs splittings and nuclear magnetic moments are required, with sensitivity adequate for the radioactive isotopes produced. A triple resonance atomic beam magnetic resonance apparatus with optical pumping state s...

  8. Clumped Isotope Composition of Cold-Water Corals: A Role for Vital Effects?

    Spooner, P.; Guo, W.; Robinson, L. F.


    Measurements on a set of cold-water corals (mainly Desmophyllum dianthus) have suggested that their clumped isotope composition could serve as a promising proxy for reconstructing paleocean temperatures. Such measurements have also offered support for certain isotope models of coral calcification. However, there are differences in the clumped isotope compositions between warm-water and cold-water corals, suggesting that different kinds of corals could have differences in their biocalcification processes. In order to understand the systematics of clumped isotope variations in cold-water corals more fully, we present clumped isotope data from a range of cold-water coral species from the tropical Atlantic and the Southern Ocean.Our samples were either collected live or recently dead (14C ages biocalcification may not apply equally well to all corals. Clumped isotope vital effects may be present in certain cold-water corals as they are in warm-water corals, complicating the use of this paleoclimate proxy.

  9. Evidence of fissiogenic Cs estimated from Ba isotopic deviations in an Oklo natural reactor zone

    Hidaka, Hiroshi; Holliger, Philippe; Masuda, Akimasa


    Isotopic studies of many elements from the uranium ore natural nuclear reactors at Oklo provide useful information on the migration of radioactive nuclides. The fissiogenic isotopic composition of Ba is particularly interesting, as it is an important indication in the search for fissiogenic Cs. In this report we detail the detection of remarkable isotopic deviations of Ba in the Oklo samples and estimate the geochemical behaviour of fissiogenic Cs from excess Ba isotopes. Six samples systematically collected from borehole SF84 (zone 10) at the Oklo uranium mine have been analyzed. Isotopic deviations of Ba indicate the existence of fissiogenic Cs and Ba. A good correlation between the elemental abundance of Cs and isotopic abundances of excess 135Ba and 137Ba suggests that fissiogenic 135Ba and 137Ba behaved as Cs rather than Ba.

  10. Carbon isotopes of graphite: Implications on fluid history

    F.J. Luque


    Full Text Available Stable carbon isotope geochemistry provides important information for the recognition of fundamental isotope exchange processes related to the movement of carbon in the lithosphere and permits the elaboration of models for the global carbon cycle. Carbon isotope ratios in fluid-deposited graphite are powerful tools for unravelling the ultimate origin of carbon (organic matter, mantle, or carbonates and help to constrain the fluid history and the mechanisms involved in graphite deposition. Graphite precipitation in fluid-deposited occurrences results from CO2- and/or CH4-bearing aqueous fluids. Fluid flow can be considered as both a closed (without replenishment of the fluid or an open system (with renewal of the fluid by successive fluid batches. In closed systems, carbon isotope systematics in graphite is mainly governed by Rayleigh precipitation and/or by changes in temperature affecting the fractionation factor between fluid and graphite. Such processes result in zoned graphite crystals or in successive graphite generations showing, in both cases, isotopic variation towards progressive 13C or 12C enrichment (depending upon the dominant carbon phase in the fluid, CO2 or CH4, respectively. In open systems, in which carbon is episodically introduced along the fracture systems, the carbon systematics is more complex and individual graphite crystals may display oscillatory zoning because of Rayleigh precipitation or heterogeneous variations of δ13C values when mixing of fluids or changes in the composition of the fluids are the mechanisms responsible for graphite precipitation.

  11. Isotope geochemistry. Biological signatures in clumped isotopes of O₂.

    Yeung, Laurence Y; Ash, Jeanine L; Young, Edward D


    The abundances of molecules containing more than one rare isotope have been applied broadly to determine formation temperatures of natural materials. These applications of "clumped" isotopes rely on the assumption that isotope-exchange equilibrium is reached, or at least approached, during the formation of those materials. In a closed-system terrarium experiment, we demonstrate that biological oxygen (O2) cycling drives the clumped-isotope composition of O2 away from isotopic equilibrium. Our model of the system suggests that unique biological signatures are present in clumped isotopes of O2—and not formation temperatures. Photosynthetic O2 is depleted in (18)O(18)O and (17)O(18)O relative to a stochastic distribution of isotopes, unlike at equilibrium, where heavy-isotope pairs are enriched. Similar signatures may be widespread in nature, offering new tracers of biological and geochemical cycling.

  12. Improvements in Precise and Accurate Isotope Ratio Determination via LA-MC-ICP-MS by Application of an Alternative Data Reduction Protocol

    Fietzke, J.; Liebetrau, V.; Guenther, D.; Frische, M.; Zumholz, K.; Hansteen, T. H.; Eisenhauer, A.


    An alternative approach for the evaluation of isotope ratio data using LA-MC-ICP-MS will be presented. In contrast to previously applied methods it is based on the simultaneous responses of all analyte isotopes of interest and the relevant interferences without performing a conventional background correction. Significant improvements in precision and accuracy can be achieved when applying this new method and will be discussed based on the results of two first methodical applications: a) radiogenic and stable Sr isotopes in carbonates b) stable chlorine isotopes of pyrohydrolytic extracts. In carbonates an external reproducibility of the 87Sr/86Sr ratios of about 19 ppm (RSD) was achieved, an improvement of about a factor of 5. For recent and sub-recent marine carbonates a mean radiogenic strontium isotope ratio 87Sr/86Sr of 0.709170±0.000007 (2SE) was determined, which agrees well with the value of 0.7091741±0.0000024 (2SE) reported for modern sea water [1,2]. Stable chlorine isotope ratios were determined ablating pyrohydrolytic extracts with a reproducibility of about 0.05‰ (RSD). For basaltic reference material JB1a and JB2 chlorine isotope ratios were determined relative to SMOC (standard mean ocean chlorinity) δ37ClJB-1a = (-0.99±0.06) ‰ and δ37ClJB-1a = (-0.60±0.03) ‰ (SD), respectively, in accordance with published data [3]. The described strategies for data reduction are considered to be generally applicable for all isotope ratio measurements using LA-MC-ICP-MS. [1] J.M. McArthur, D. Rio, F. Massari, D. Castradori, T.R. Bailey, M. Thirlwall, S. Houghton, Palaeogeo. Palaeoclim. Palaeoeco., 2006, 242 (126), doi: 10.1016/j.palaeo.2006.06.004 [2] J. Fietzke, V. Liebetrau, D. Guenther, K. Guers, K. Hametner, K. Zumholz, T.H. Hansteen and A. Eisenhauer, J. Anal. At. Spectrom., 2008, 23, 955-961, doi:10.1039/B717706B [3] J. Fietzke, M. Frische, T.H. Hansteen and A. Eisenhauer, J. Anal. At. Spectrom., 2008, 23, 769-772, doi:10.1039/B718597A

  13. Systematic review

    Lødrup, Anders Bergh; Reimer, Christina; Bytzer, Peter


    in getting off acid-suppressive medication and partly explain the increase in long-term use of PPI. A number of studies addressing this issue have been published recently. The authors aimed to systematically review the existing evidence of clinically relevant symptoms caused by acid rebound following PPI...

  14. Stable isotopes. Applications and production; Les isotopes stables. Applications - production

    Goldstein, S.; Louvet, P.; Soulie, E. [eds.


    This conference presents 46 communications concerning stable isotope production, utilization and application, grouped in 6 sessions and posters. The various themes are: biological applications (pharmacology, medical diagnosis, metabolism and protein studies, toxicity and response studies, labelled compounds), analysis procedures (NMR analysis for macromolecules, tracer studies), nuclear applications (utilization of stable isotopes in nuclear reactors), biological, physical and chemical applications (mass transfer, mobility, crystallography, isotopic exchange), stable isotope production (ion chromatography, ion cyclotron resonance, cryogenic distillation).

  15. Radiogenic Ingrowth of 40CA from Decay of 40K Provides a Powerful Tracer for Understanding the Origins of Felsic Magmas

    Mills, Ryan D.; Simon, Justin I.; Depaolo, Donald J.; Bachmann, Olivier


    Over time high K/Ca continental crust produces a unique Ca isotopic reservoir, with measurable 40Ca excesses compared to Earth's mantle (?Ca=0). Thus, values of ?Cai > 1 indicate a significant crustal contribution to a magma. Values of ?Cai (<1) indistinguishable from mantle Ca indicate that the Ca in those magmas is either directly from the mantle, or is from partial melting of newly formed crust. So, whereas 40Ca excesses clearly define crustal contributions, mantle-like 40Ca/44Ca ratios are not as definitive. Here we present Ca isotopic measurements of intermediate to felsic igneous rocks from the western United States, and two crustal xenoliths found within the Fish Canyon Tuff (FCT). The two crustal xenoliths found within the 28.2 Ma FCT of the southern Rocky Mountain volcanic field (SRMVF) yield ?Ca values of 4 and 7.5, respectively. The 40Ca excesses of these possible source rocks are due to long-term in situ 40K decay and suggest that they are Precambrian in age. However, the FCT (?Cai 0.3) is within uncertainty of the mantle 40Ca/44Ca. Together, these data indicate that little Precambrian crust was involved in the petrogenesis of the FCT. Nd isotopic analyses of the FCT imply that it was generated from 1