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Now showing items 1 - 16 of 400

  • The noble gas isotope record of hydrocarbon field formation time scales

    Tolstikhin, Igor N.   Ballentine, Chris J.   Polyak, Boris G.   Prasolov, Edward M.   Kikvadze, Olga E.  

    Noble gases may be considered as the most prominent tracers of natural fluids, including hydrocarbons. The atmosphere is the only source of Ne-20, Ar-36, Kr-84, Xe-130 in subsurface environments, and their concentrations in pore waters after recharge are known from the solubility data. This allows modelling of noble gas partitioning between coexisting gas, oil and water phases in the course of hydrocarbon formation, migration, and storage. Radiogenic isotopes, He-4*, Ne-21*, Ar-40*, Xe-136*, after being released from source rocks, are mixed with air-derived noble gases already present in the pore space. Concentrations of radiogenic species in the pore space of "typical" hydrocarbon fields are generally so high, that they can hardly be accumulated in situ and thus indicate noble gas transfer from ground waters. The time bearing ratios He-4*/Ne-20, Ne-21*/Ne-20, He-4*/Ar-40(AIR) Ar-40*/Ar-40(AIR) in hydrocarbon fields are thus proportional to the time interval between the ground water recharge and noble gases partitioning into the hydrocarbon phase(s), the 'recharge - partition interval'. The largest available data set allows the recharge-partition intervals to be constrained for a large number of hydrocarbon fields, situated in different tectonic settings (ancient plates, young plates, mobile belts). These intervals increase systematically with the ages of hydrocarbon source and trap lithologies and are comparable with these ages. This important feature, valid in general for different hydrocarbon fields, implies: (i) local sources of radiogenic noble gas isotopes in ground waters; (ii) relatively recent formation of hydrocarbon fields and (iii) their short formation time scales. In some cases the duration of formation of a hydrocarbon field can be constrained. For example, nearly constant Ne-21*/Ne-20, Ar-40*/Ar-40(AIR) ratios, measured in samples from the Magnus oil field (North Sea), give an accumulation time scale approximate to 10 Ma. It should be emphasized that the above noble gas isotope ratios give the time estimates, which are independent of geological reconstructions. Sometimes the noble gas inventory in a hydrocarbon field and ground waters allows characterization of the source rock volume, involved in formation of the field; generally this volume exceeds that of the hydrocarbon field rocks by orders of magnitude.
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  • Geochemistry: A dash of deep nebula on the rocks

    Ballentine, Chris J.  

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  • End-Permian extinction amplified by plume-induced release of recycled lithospheric volatiles

    Broadley, Michael W.   Barry, Peter H.   Ballentine, Chris J.   Taylor, Lawrence A.   Burgess, Ray  

    Magmatic volatile release to the atmosphere can lead to climatic changes and substantial environmental degradation including the production of acid rain, ocean acidification and ozone depletion, potentially resulting in the collapse of the biosphere. The largest recorded mass extinction in Earth's history occurred at the end of the Permian, coinciding with the emplacement of the Siberian large igneous province, suggesting that large-scale magmatism is a key driver of global environmental change. However, the source and nature of volatiles in the Siberian large igneous province remain contentious. Here we present halogen compositions of sub-continental lithospheric mantle xenoliths emplaced before and after the eruption of the Siberian flood basalts. We show that the Siberian lithosphere is massively enriched in halogens from the infiltration of subducted seawater-derived volatiles and that a considerable amount (up to 70%) of lithospheric halogens are assimilated into the plume and released to the atmosphere during emplacement. Plume-lithosphere interaction is therefore a key process controlling the volatile content of large igneous provinces and thus the extent of environmental crises, leading to mass extinctions during their emplacement.
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  • Solubility trapping in formation water as dominant CO2 sink in natural gas fields

    Lollar, Barbara Sherwood   Holland, Greg   Blagburn, Dave   Stevens, Scott   Schoell, Martin   Cassidy, Martin   Ding, Zhenju   Zhou, Zheng   Lacrampe-Couloume, Georges   Ballentine, Chris J.  

    Injecting CO2 into deep geological strata is proposed as a safe and economically favourable means of storing CO2 captured from industrial point sources(1-3). It is difficult, however, to assess the long-term consequences of CO2 flooding in the subsurface from decadal observations of existing disposal sites(1,2). Both the site design and long-term safety modelling critically depend on how and where CO2 will be stored in the site over its lifetime(2-4). Within a geological storage site, the injected CO2 can dissolve in solution or precipitate as carbonate minerals. Here we identify and quantify the principal mechanism of CO2 fluid phase removal in nine natural gas fields in North America, China and Europe, using noble gas and carbon isotope tracers. The natural gas fields investigated in our study are dominated by a CO2 phase and provide a natural analogue for assessing the geological storage of anthropogenic CO2 over millennial timescales(1,2,5,6). We find that in seven gas fields with siliciclastic or carbonate-dominated reservoir lithologies, dissolution in formation water at a pH of 5-5.8 is the sole major sink for CO2. In two fields with siliciclastic reservoir lithologies, some CO2 loss through precipitation as carbonate minerals cannot be ruled out, but can account for a maximum of 18 per cent of the loss of emplaced CO2. In view of our findings that geological mineral fixation is a minor CO2 trapping mechanism in natural gas fields, we suggest that long-term anthropogenic CO2 storage models in similar geological systems should focus on the potential mobility of CO2 dissolved in water.
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  • Halogen behaviour in subduction zones:Eclogite facies rocks from the Western and Central Alps

    Hughes, Lewis   Burgess, Ray   Chavrit, Deborah   Pawley, Alison   Tartese, Romain   Droop, Giles   Ballentine, Chris J.   Lyon, Ian  

    We examined F, Cl, Br and I concentrations and distributions in eclogite facies rocks and minerals from the Western and Central Alpine ophiolitic zone to determine halogen behaviour in subduction zones, and to identify potential host phases that may be able to transport halogens to the deeper mantle. Analysis was carried out on a range of ophiolitic lithologies-peridotites, serpentinites, metagabbros, metabasalts and metasediments-to assess the distribution of halogens within deeply subducted oceanic crust. Halogen abundances in individual mineral phases range from below detection (similar to 100 ppm) to similar to 1900 ppm for F, similar to 1 to similar to 3000 ppm for Cl, similar to 1 to similar to 11,000 ppb for Br and from <1 to similar to 1300 ppb for I. Bulk rock estimates of Cl, Br and I abundances are variable, but are generally more than one order of magnitude lower than those in altered oceanic crust (AOC), suggesting major halogen loss prior to or during eclogite facies metamorphism. Fluorine, however, can be enriched within metabasalts and metasediments, relative to the heavy halogens, suggesting F can be retained at eclogite facies conditions within the upper layers of the subducting slab. Bulk rock estimates suggest that upon reaching eclogite facies, the subducting slab has lost over 90% Cl, Br and I. Bromine and iodine concentrations show positive correlation, suggesting that they exhibit similar behaviour at high pressure. A lack of any other correlations suggest that F and Cl behave differently to Br and I during subduction. Elevated F/Cl, Br/Cl and I/Cl ratios, relative to AOC, suggest the preferential loss of Cl during shallower depths of subduction. In situ analyses and chemical mapping using electron probe micro-analysis and time of flight secondary ion mass spectrometry indicate that measured halogen abundances are primarily hosted within the mineral structure. Overall, our dataset provides new constraints on the available inventory of halogens that can be transferred to the deeper mantle via the subduction of oceanic crust. (C) 2018 The Authors. Published by Elsevier Ltd.
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  • Meteorite Kr in Earth's Mantle Suggests a Late Accretionary Source for the Atmosphere

    Holland, Greg   Cassidy, Martin   Ballentine, Chris J.  

    Noble gas isotopes are key tracers of both the origin of volatiles found within planets and the processes that control their eventual distribution between planetary interiors and atmospheres. Here, we report the discovery of primordial Kr in samples derived from Earth's mantle and show it to be consistent with a meteorite or fractionated solar nebula source. The high-precision Kr and Xe isotope data together suggest that Earth's interior acquired its volatiles from accretionary material similar to average carbonaceous chondrites and that the noble gases in Earth's atmosphere and oceans are dominantly derived from later volatile capture rather than impact degassing or outgassing of the solid Earth during its main accretionary stage.
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  • Neon isotopes constrain convection and volatile origin in the Earth\"s mantle

    Ballentine, Chris J.   Marty, Bernard   Sherwood Lollar, Barbara   Cassidy, Martin  

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  • Selected isotope applications in cosmochemistry and geochemistry

    Ballentine, Chris J.   Lyon, Ian  

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  • Noble gases fingerprint a metasedimentary fluid source in the Macraes orogenic gold deposit,New Zealand

    Goodwin, Nicholas R. J.   Burgess, Ray   Craw, Dave   Teagle, Damon A. H.   Ballentine, Chris J.  

    The world-class Macraes orogenic gold deposit (similar to 10 Moz resource) formed during the late metamorphic uplift of a metasedimentary schist belt in southern New Zealand. Mineralising fluids, metals and metalloids were derived from within the metasedimentary host. Helium and argon extracted from fluid inclusions in sulphide mineral grains (three crush extractions from one sample) have crustal signatures, with no evidence for mantle input (R/Ra =3D 0.03). Xenon extracted from mineralised quartz samples provides evidence for extensive interaction between fluid and maturing organic material within the metasedimentary host rocks, with Xe-132/Ar-36 ratios up to 200 times greater than air. Similarly, I/Cl ratios for fluids extracted from mineralised quartz are similar to those of brines from marine sediments that have interacted with organic matter and are ten times higher than typical magmatic/mantle fluids. The Macraes mineralising fluids were compositionally variable, reflecting either mixing of two different crustal fluids in the metasedimentary pile or a single fluid type that has had varying degrees of interaction with the host metasediments. Evidence for additional input of meteoric water is equivocal, but minor meteoric incursion cannot be discounted. The Macraes deposit formed in a metasedimentary belt without associated coeval magmatism, and therefore represents a purely crustal metamorphogenic end member in a spectrum of orogenic hydrothermal processes that can include magmatic and/or mantle fluid input elsewhere in the world. There is no evidence for involvement of minor intercalated metabasic rocks in the Macraes mineralising system. Hydrothermal fluids that formed other, smaller, orogenic deposits in the same metamorphic belt have less pronounced noble gas and halogen evidence for crustal fluid-rock interaction than at Macraes, but these deposits also formed from broadly similar metamorphogenic processes.
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  • The origin of air-like noble gases in MORB and OIB

    Ballentine, Chris J.   Barfod, Dan N.  

    Interpretation of the noble gas (Ne, Ar, Kr and Xe) isotopic composition of Ocean Island and Mid Ocean Ridge basalt (OIB and MORB) glass is complicated by the near surface addition of atmosphere-derived noble gases. Although the noble gas elemental composition in these samples is often similar to modern air, equilibration between a seawater vapor phase and a basalt melt can produce similar values in the melt phase [Patterson et al., Geophys. Res. Lett. 17 (1990) 705–708]. With the assumption that laboratory handling must reverse any surficial modern air contamination, it has often been concluded that the measured ‘air-like’ noble gases are introduced into MORB and OIB glass by variable interaction of the magma with seawater, either before or during eruption. Harrison et al.[Earth Planet. Sci. Lett. 171 (1999) 199–207] have recently demonstrated that both MORB popping rock and subglacially erupted Iceland OIB glass contain a component with 130Xe/22Ne indistinguishable from modern air. 84Kr/22Ne and 36Ar/22Ne are also indistinguishable from modern air for air values of 20Ne/22Ne. Assuming that the mode of this ‘air-like’ component addition is the same in both systems we show that calculated fractionation values for melt/seawater and melt/freshwater–glacier systems respectively cannot produce the observed elemental abundance pattern. We argue that the dominant source of ‘air-like’ noble gases in both the MORB and OIB is contamination by unfractionated modern air during sampling or sample preparation within the laboratory. We show that this is related to vesicularity and does not appear to be fully removed by current laboratory techniques. Because vesicularity is related to eruption depth and volatile content [J.G. Moore, Nature 282 (1979) 250–253], recently observed correlations between atmosphere-derived noble gases with radiogenic Pb, water content or other trace element pairs [Sarda et al., Science 283 (1999) 666–668; Bach and Niedermann, Earth Planet. Sci. Lett. 160 (1998) 297–309] may not reflect a relationship between these species in the magmatic source. Similarly, the conclusion from the existing MORB and OIB data set that the terrestrial mantle heavy noble gases have many similar features to modern air [Ozima and Igarashi, Earth Planet. Sci. Lett. 176 (2000) 219–232] is premature. These observations can be equally well accounted for by eruption style related vesicularity and related air contamination.
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  • Origins of the terrestrial Hf-Nd mantle array:Evidence from a combined geodynamical-geochemical approach

    Jones, Rosemary E.   van Keken, Peter E.   Hauri, Erik H.   Tucker, Jonathan M.   Vervoort, Jeffrey   Ballentine, Chris J.  

    The formation and segregation of oceanic and continental crust from the mantle, and its return to the mantle via subduction and/or delamination, leads to the development of distinct geochemical reservoirs in the terrestrial mantle. Fundamental questions remain regarding the location, nature, and residence time of these reservoirs, as well as the respective roles of oceanic and continental crust in the development of the mantle's geochemical endmembers. The Lu-Hf and Sm-Nd isotope systems behave similarly in magmatic systems and together form the terrestrial mantle Hf-Nd isotopic array. Here we combine a geodynamic model of mantle convection with isotope and trace element (TE) geochemistry to investigate the evolution of the Hf-Nd mantle array. This study examines the sensitivity to: TE partition coefficients used in the formation of oceanic crust; density contrasts between subducting oceanic crust and the mantle; and the formation and recycling of continental crust. We show that the fractionation between the parent (Lu and Sm) and daughter (Hf and Nd) species needs to be higher than is indicated by partition coefficients determined from the present-day melting environment. This is consistent with the suggestion of deeper mantle melting earlier in Earth history and an increased role for residual garnet. Subduction and accumulation of dense oceanic crust produces a large mass of incompatible TE enriched material in the deep mantle. This deep mantle enrichment appears to play a more significant role than the extraction and recycling of continental crust in developing the Hf and Nd isotope and TE compositions of the mid-ocean ridge mantle source. The corollary of this result is that the formation of the continental crust plays a secondary role, contrary to the currently accepted paradigm. Nevertheless, the inclusion of continental crust formation and recycling produces a broader model mantle array, which better reproduces the spread in the natural data set. This model also produces the Hf and Nd isotope and TE compositions of the upper mantle and continental crust, as well as deep mantle compositions similar to those of plume-fed ocean island basalts. Our model is consistent with continental growth models based on the Lu-Hf isotopic composition of zircon, which suggest that 50-70% of the present-day mass of the continental crust is produced prior to 3 Ga, and that the recycling of continental crust becomes more prevalent after this time. (C) 2019 Elsevier B.V. All rights reserved.
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  • Author Correction: End-Permian extinction amplified by plume-induced release of recycled lithospheric volatiles

    Broadley, Michael W.   Barry, Peter H.   Ballentine, Chris J.   Taylor, Lawrence A.   Burgess, Ray  

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  • End-Permian extinction amplified by plume-induced release of recycled lithospheric volatiles (vol 11,pg 96,2018)

    Broadley, Michael W.   Barry, Peter H.   Ballentine, Chris J.   Taylor, Lawrence A.   Burgess, Ray  

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  • End-Permian extinction amplified by plume-induced release of recycled lithospheric volatiles (vol 11,pg 682,2018)

    Broadley, Michael W.   Barry, Peter H.   Ballentine, Chris J.   Taylor, Lawrence A.   Burgess, Ray  

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  • South African crustal fracture fluids preserve paleometeoric water signatures for up to tens of millions of years

    Heard, Andrew W.   Warr, Oliver   Borgonie, Gaetan   Linage, Borja   Kuloyo, Olukayode   Fellowes, Jonathan W.   Magnabosco, Cara   Lau, Maggie C. Y.   Erasmus, Mariana   Cason, Errol D.   van Heerden, Esta   Kieft, Thomas L.   Mabry, Jennifer C.   Onstott, Tullis C.   Lollar, Barbara Sherwood   Ballentine, Chris J.  

    Fracture fluids in Earth's crust may remain isolated for millions to billions of years, and contain information on paleohydrogeology, subsurface microbial life, and conservative components that help elucidate the atmospheric evolution of the early Earth. Examples include fluids in the South African Kaapvaal craton which host chemo-lithoautotrophic microbial communities that survive independent of the photosphere, and billion-year-old fluids in the Canadian Shield, which preserve the Xe isotopic signature of an evolving early atmosphere. Stable isotope analyses of the aqueous phase combined with isotopic analyses of the dissolved noble gases provide unrivalled insight into the time-alteration history of aqueous fracture fluids. Here we report stable isotope and noble gas data for fracture fluids in the Witwatersrand Basin and Bushveld Igneous Province systems, South Africa. We determine closed-system radiogenic noble gas residence times of 0.77-97 million years (Myr). Open-system residence times range between 6.0 kyr and 10.8 Myr. One sample from Masimong Mine has a mean closed-system residence time of 85 Myr, making it one of oldest paleometeoric waters ever recorded. The delta(2H) and delta O-18 of water in this sample, and in previously reported samples from the same mining district that are shown to have similar ages, require an isotopically depleted source of groundwater recharge. This could reflect a recharge regime at a higher paleolatitude, elevation, or with higher rainfall, established up to tens of Myr ago, and perhaps similar to the recharge regime in the modern Lesotho Highlands. These data suggest that groundwater isotopes can provide useful paleoclimatic information for many Myr.
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  • Regional groundwater focusing of nitrogen and noble gases into the Hugoton-Panhandle giant gas field, USA

    Ballentine, Chris J.   Sherwood Lollar, Barbara  

    The Hugoton-Panhandle giant gas field, located across SW Kansas and the Texas and Oklahoma panhandles in the USA, is the case type example of high nitrogen concentrations in a natural gas being linked with high helium concentrations. We collected 31 samples from producing wells in a north-south traverse of the 350-km-long field. The samples reflect the previously observed north-south change in 4He/N2, with values changing from 0.020 to 0.049 respectively. 3He/4He, 21Ne/22Ne, and 40Ar/36Ar vary between 0.14–0.25 Ra, 0.0373–0.0508, and 818–1156 respectively, and are caused by quantifiable contributions from mantle, crustal, and atmosphere-derived sources. The atmosphere-derived 20Ne/36Ar ratios are indistinguishable from groundwater values. The crustal 4He/21Ne* and 4He/40Ar* ratios show a 60%excess of 4He compared to predicted production ratios in the crust and are typical of noble gases released from the shallow crust. The mantle 3He/N2 and groundwater-recharge 36Ar/N2 ratios enable us to rule out significant magmatic or atmosphere contributions to the gas field N2, which is dominantly crustal in origin.
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