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Mathieu Dellinger - One of the best experts on this subject based on the ideXlab platform.

  • tracing weathering regimes using the Lithium Isotope composition of detrital sediments
    Geology, 2017
    Co-Authors: Mathieu Dellinger, Julien Bouchez, Jérôme Gaillardet, Laëtitia Faure, Julien Moureau
    Abstract:

    Lithium (Li) Isotopes are a promising tracer of chemical weathering processes for both modern and ancient times. In order to improve the use of Li Isotopes in the sedimentary record, here we calibrate the relationship between weathering intensity and detrital Li Isotope composition (δ7Li) using the fine fraction of modern large river sediments. Through independent estimates for sediment provenance to calculate the Li Isotope signature of the rock from which the sediments derive through weathering, we show that source rock variability (in particular the relative contribution of sedimentary versus igneous rocks) must be corrected for before using Li Isotopes as a weathering proxy. We also show that for rivers draining mountain ranges, the contribution to river sediments of particles derived from sedimentary rocks is correlated to their Li/Al ratio, making it possible to use Li contents to estimate the average source rock composition. Once corrected for bedrock variability, the Li Isotope signature defines a negative relationship with the weathering intensity (ratio between silicate weathering rate and total denudation rate), with highest Li Isotope fractionation for the highest weathering intensity. Altogether, we propose a set of new relationships between weathering, erosion, provenance, and Li Isotopes that can be used to quantify present-day and paleo-weathering using detrital sediment.

  • Tracing weathering regimes using the Lithium Isotope composition of detrital sediments
    Geology, 2017
    Co-Authors: Mathieu Dellinger, Julien Bouchez, Jérôme Gaillardet, Laëtitia Faure, Julien Moureau
    Abstract:

    hellingerD wthieu nd fouhezD tulien nd qillrdetD t¡ er¢ ome nd pureD vetiti nd woureuD tulien @PHIUA 9ring wethering regimes using the Lithium Isotope omposition of detritl sedimentsF9D qeologyFD RS @SAF ppF RIIERIRF Further information on publisher's website: httpsXGGdoiForgGIHFIIQHGqQVTUIFI Publisher's copyright statement: Additional information: Use policy The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that: • a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.

Julien Moureau - One of the best experts on this subject based on the ideXlab platform.

  • tracing weathering regimes using the Lithium Isotope composition of detrital sediments
    Geology, 2017
    Co-Authors: Mathieu Dellinger, Julien Bouchez, Jérôme Gaillardet, Laëtitia Faure, Julien Moureau
    Abstract:

    Lithium (Li) Isotopes are a promising tracer of chemical weathering processes for both modern and ancient times. In order to improve the use of Li Isotopes in the sedimentary record, here we calibrate the relationship between weathering intensity and detrital Li Isotope composition (δ7Li) using the fine fraction of modern large river sediments. Through independent estimates for sediment provenance to calculate the Li Isotope signature of the rock from which the sediments derive through weathering, we show that source rock variability (in particular the relative contribution of sedimentary versus igneous rocks) must be corrected for before using Li Isotopes as a weathering proxy. We also show that for rivers draining mountain ranges, the contribution to river sediments of particles derived from sedimentary rocks is correlated to their Li/Al ratio, making it possible to use Li contents to estimate the average source rock composition. Once corrected for bedrock variability, the Li Isotope signature defines a negative relationship with the weathering intensity (ratio between silicate weathering rate and total denudation rate), with highest Li Isotope fractionation for the highest weathering intensity. Altogether, we propose a set of new relationships between weathering, erosion, provenance, and Li Isotopes that can be used to quantify present-day and paleo-weathering using detrital sediment.

  • Tracing weathering regimes using the Lithium Isotope composition of detrital sediments
    Geology, 2017
    Co-Authors: Mathieu Dellinger, Julien Bouchez, Jérôme Gaillardet, Laëtitia Faure, Julien Moureau
    Abstract:

    hellingerD wthieu nd fouhezD tulien nd qillrdetD t¡ er¢ ome nd pureD vetiti nd woureuD tulien @PHIUA 9ring wethering regimes using the Lithium Isotope omposition of detritl sedimentsF9D qeologyFD RS @SAF ppF RIIERIRF Further information on publisher's website: httpsXGGdoiForgGIHFIIQHGqQVTUIFI Publisher's copyright statement: Additional information: Use policy The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that: • a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.

Philip Pogge A E Von Strandmann - One of the best experts on this subject based on the ideXlab platform.

  • Lithium Isotope behaviour during weathering in the ganges alluvial plain
    Geochimica et Cosmochimica Acta, 2017
    Co-Authors: Philip Pogge A E Von Strandmann, Patrick J Frings, Melissa J Murphy
    Abstract:

    The Ganges river system is responsible for the transportation of a large flux of dissolved materials derived from Himalayan weathering to the oceans. Silicate weathering-driven cooling resulting from uplift of the Himalayas has been proposed to be a key player in Cenozoic climate variation. This study has analysed Li Isotope (δ7Li) ratios from over 50 Ganges river waters and sediments, in order to trace silicate weathering processes. Sediments have δ7Li of ∼0‰, identical to bulk continental crust, however suspended sediment depth profiles do not display variations associated with grain size that have been observed in other large river systems. Dissolved δ7Li are low (∼11‰) in the Ganges headwaters, but reach a constant value of 21 ± 1.6‰ within a relatively short distance downstream, which is then maintained for almost 2000 km to the Ganges mouth. Given that Li Isotopes are controlled by the ratio of primary mineral dissolution to secondary mineral formation, this suggests that the Ganges floodplain is at steady-state in terms of these processes for most of its length. Low δ7Li in the mountainous regions suggest silicate weathering is therefore at its most congruent where uplift and fresh silicate exposure rates are high. However, there is no correlation between δ7Li and the silicate weathering rate in these rivers, suggesting that Li Isotopes cannot be used as a weathering-rate tracer, although they do inform on weathering congruency and intensity. The close-to-constant δ7Li values for the final 2000 km of Ganges flow also suggest that once the size of the alluvial plain reached more than ∼500 km (the flow distance after which riverine δ7Li stops varying), the Ganges exerted little influence on the changing Cenozoic seawater δ7Li, because riverine δ7Li attained a near steady-state composition.

  • Lithium Isotope evidence for enhanced weathering during oceanic anoxic event 2
    Nature Geoscience, 2013
    Co-Authors: Philip Pogge A E Von Strandmann, Hugh C Jenkyns, Richard G Woodfine
    Abstract:

    The Ocean Anoxic Event 2 (OAE2) about 93.5 million years ago was marked by high atmospheric CO2 concentration, rapid global warming and marine anoxia and euxinia. The event lasted for about 440,000 years and led to habitat loss and mass extinction. The marine anoxia is thought to be linked to enhanced biological productivity, but it is unclear what triggered the increased production and what allowed the subsequent rapid climate recovery. Here we use Lithium Isotope measurements from carbonates spanning the interval including OAE2 to assess the role of silicate weathering. We find the lightest values of the Li Isotope ratio (δ7Li) during OAE2, indicating high levels of weathering—and therefore atmospheric CO2 removal—which we attribute to an enhanced hydrological cycle. We use a geochemical model to simulate the evolution of δ7Li and the Ca, Sr and Os Isotope tracers. Our simulations suggest a scenario in which the eruption of a large igneous province led to high atmospheric CO2 concentrations and rapid global warming, which initiated OAE2. The simulated warming was accompanied by a roughly 200,000 year pulse of accelerated weathering of mafic silicate rocks, which removed CO2 from the atmosphere. The weathering also delivered nutrients to the oceans that stimulated primary productivity. We suggest that this process, together with the burial of organic carbon, allowed the rapid recovery and stabilization from the greenhouse state.

  • assessing the role of climate on uranium and Lithium Isotope behaviour in rivers draining a basaltic terrain
    Chemical Geology, 2010
    Co-Authors: Philip Pogge A E Von Strandmann, Kevin W Burton, Rachael H James, Peter Van Calsteren, Sigurður R Gislason
    Abstract:

    This study presents uranium (U) and Lithium (Li) Isotope and major and trace element data for the dissolved load, suspended particles and bedload from rivers draining dominantly basaltic catchments on the island of Sao Miguel in the Azores Archipelago. Uranium activity ratios are at secular equilibrium in the bedload, but are higher for suspended material, suggesting sorption of uranium from the solution onto particle surfaces. The (234U/238U) of the riverine dissolved phase varies between 1.02 and 1.86, and lies on a mixing trend between the values expected from chemical weathering of basalt (high [U]; (234U/238U) at secular equilibrium) and an endmember with low [U] and high (234U/238U), which probably reflects α-recoil effects associated with physical weathering and/or soil formation. Lithium Isotope ratios are consistently lighter in suspended material than the corresponding bedload, suggesting preferential retention of 6Li in the suspended load. In turn, the δ7Li of the dissolved load is always isotopically heavier, ranging from 5.9 to 36.2‰, although the lightest values are affected by hydrothermal input. The Lithium isotopic composition of the dissolved load reflects the balance of primary mineral dissolution to secondary mineral formation. Comparison of the behaviour of U and Li Isotopes between Sao Miguel, Iceland, and other basaltic terrains suggests that whilst U Isotopes are dominated by weathering regimes dependent on factors such as weathering rates, temperature, runoff and climate, neither weathering intensity nor climate exerts a direct influence on Li Isotope behaviour; rather the formation of secondary minerals, which is indirectly controlled by climate, weathering, primary mineralogy and biology, appears to play the dominant role.

Jérôme Gaillardet - One of the best experts on this subject based on the ideXlab platform.

  • tracing weathering regimes using the Lithium Isotope composition of detrital sediments
    Geology, 2017
    Co-Authors: Mathieu Dellinger, Julien Bouchez, Jérôme Gaillardet, Laëtitia Faure, Julien Moureau
    Abstract:

    Lithium (Li) Isotopes are a promising tracer of chemical weathering processes for both modern and ancient times. In order to improve the use of Li Isotopes in the sedimentary record, here we calibrate the relationship between weathering intensity and detrital Li Isotope composition (δ7Li) using the fine fraction of modern large river sediments. Through independent estimates for sediment provenance to calculate the Li Isotope signature of the rock from which the sediments derive through weathering, we show that source rock variability (in particular the relative contribution of sedimentary versus igneous rocks) must be corrected for before using Li Isotopes as a weathering proxy. We also show that for rivers draining mountain ranges, the contribution to river sediments of particles derived from sedimentary rocks is correlated to their Li/Al ratio, making it possible to use Li contents to estimate the average source rock composition. Once corrected for bedrock variability, the Li Isotope signature defines a negative relationship with the weathering intensity (ratio between silicate weathering rate and total denudation rate), with highest Li Isotope fractionation for the highest weathering intensity. Altogether, we propose a set of new relationships between weathering, erosion, provenance, and Li Isotopes that can be used to quantify present-day and paleo-weathering using detrital sediment.

  • Tracing weathering regimes using the Lithium Isotope composition of detrital sediments
    Geology, 2017
    Co-Authors: Mathieu Dellinger, Julien Bouchez, Jérôme Gaillardet, Laëtitia Faure, Julien Moureau
    Abstract:

    hellingerD wthieu nd fouhezD tulien nd qillrdetD t¡ er¢ ome nd pureD vetiti nd woureuD tulien @PHIUA 9ring wethering regimes using the Lithium Isotope omposition of detritl sedimentsF9D qeologyFD RS @SAF ppF RIIERIRF Further information on publisher's website: httpsXGGdoiForgGIHFIIQHGqQVTUIFI Publisher's copyright statement: Additional information: Use policy The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that: • a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.

Rachael H James - One of the best experts on this subject based on the ideXlab platform.

  • assessing the role of climate on uranium and Lithium Isotope behaviour in rivers draining a basaltic terrain
    Chemical Geology, 2010
    Co-Authors: Philip Pogge A E Von Strandmann, Kevin W Burton, Rachael H James, Peter Van Calsteren, Sigurður R Gislason
    Abstract:

    This study presents uranium (U) and Lithium (Li) Isotope and major and trace element data for the dissolved load, suspended particles and bedload from rivers draining dominantly basaltic catchments on the island of Sao Miguel in the Azores Archipelago. Uranium activity ratios are at secular equilibrium in the bedload, but are higher for suspended material, suggesting sorption of uranium from the solution onto particle surfaces. The (234U/238U) of the riverine dissolved phase varies between 1.02 and 1.86, and lies on a mixing trend between the values expected from chemical weathering of basalt (high [U]; (234U/238U) at secular equilibrium) and an endmember with low [U] and high (234U/238U), which probably reflects α-recoil effects associated with physical weathering and/or soil formation. Lithium Isotope ratios are consistently lighter in suspended material than the corresponding bedload, suggesting preferential retention of 6Li in the suspended load. In turn, the δ7Li of the dissolved load is always isotopically heavier, ranging from 5.9 to 36.2‰, although the lightest values are affected by hydrothermal input. The Lithium isotopic composition of the dissolved load reflects the balance of primary mineral dissolution to secondary mineral formation. Comparison of the behaviour of U and Li Isotopes between Sao Miguel, Iceland, and other basaltic terrains suggests that whilst U Isotopes are dominated by weathering regimes dependent on factors such as weathering rates, temperature, runoff and climate, neither weathering intensity nor climate exerts a direct influence on Li Isotope behaviour; rather the formation of secondary minerals, which is indirectly controlled by climate, weathering, primary mineralogy and biology, appears to play the dominant role.

  • high temperature Lithium Isotope fractionation insights from Lithium Isotope diffusion in magmatic systems
    Earth and Planetary Science Letters, 2007
    Co-Authors: Ian J Parkinson, Rachael H James, Samantha J Hammond, N W Rogers
    Abstract:

    Ion-microprobe analyses of the Li concentration and Li isotopic composition of zoned clinopyroxene and olivine phenocrysts from within primitive arc lavas from the New Georgia Group in the Solomon Islands reveal that both Li and δ7Li vary widely from rim to core. The Li content of the rims is between 2 and 8 times that of the cores whereas Li Isotope profiles are characterised by a zone with low δ7Li (as low as − 20‰) and cores with δ7Li values of between − 4 and + 8‰; these over-print macroscopic major element zoning. With time, the low δ7Li zone broadens and migrates towards the centre of the crystal and the Li concentration gradient is reduced. These data are consistent with preferential diffusion of 6Li into the grain from a Li-enriched rim with 6Li diffusing ∼ 3% faster than 7Li. The profiles of δ7Li and Li concentration can be reproduced by numerical modelling which confirms that the size of the δ7Li trough is a function of the Li concentration gradient and the fractional difference in the diffusion rates of 6Li and 7Li. Both open and closed system models predict that a zone with low δ7Li will migrate through the mineral grain with time, eventually relaxing back to a flat profile. Modelling of Fe-Mg diffusion in olivine suggests that the crystals have a residence time of 13–150 days, which is in accordance with the observed Li Isotope profiles. This allows us to calibrate the rate of Li diffusion, which is 4–8 times slower in olivine and 20–30 times faster in clinopyroxene than Fe–Mg diffusion in olivine. The high speed of Li diffusion means that the δ7Li values of minerals that interact with Li-rich melts can rapidly decrease. Therefore, porphyritic lavas are unlikely to be suitable for Li Isotope studies of mantle processes and it may also explain why olivines generally have higher δ7Li than co-existing pyroxenes in some mantle samples. Modification of Li Isotope ratios, by interaction with the host lava, may occur in mantle xenoliths during transport to the Earth's surface in only a few days. Conversely, melts ascending through the mantle will rapidly exchange Li and this may erase the pristine δ7Li information that the melt carries. This may explain why many subduction zone lavas do not have an obvious slab signature. This study demonstrates that Li diffusion can overprint primary mineral compositions on very short timescales. This means that careful investigation of coexisting minerals is required, but it may also provide valuable information about the timescales of short duration events.

  • The Lithium Isotope composition of international rock standards
    Chemical Geology, 2000
    Co-Authors: Rachael H James, Martin R. Palmer
    Abstract:

    We present the results of analysis of the Li Isotope composition of open ocean seawater, nine international rock standards and a C1 chondrite. In addition, we suggest some modifications of the chemical preparation techniques for analysis of Lithium Isotopes in low concentration samples that give precise Isotope ratios by thermal ionisation mass spectrometry (TIMS). The aim of this study is to provide a benchmark for ensuring the reliability of Li Isotope data between different laboratories by TIMS and other Isotope ratio techniques, including multi collector-inductively coupled plasma-mass spectrometry and ion probe