Adkins, J. F.

Bagard, M.-L.

Corsetti, F.

Dellinger, M.

Eagle, R.

Freitas, P. S.

Paris, G.

Ries, J.

West, A. J.

English

Open Research Online (The Open University)

Open Research OnlineThe Open University’s repository of research publicationsand other research outputsThe vital aspects of reconstructing seawater Li isotopecomposition: insights from modern shells and culturedorganismsConference or Workshop ItemHow to cite:Dellinger, M.; West, A. J.; Adkins, J. F.; Paris, G.; Freitas, P. S.; Bagard, M.-L.; Eagle, R.; Ries, J. andCorsetti, F. (2015). The vital aspects of reconstructing seawater Li isotope composition: insights from modern shellsand cultured organisms. In: Goldschmidt Abstracts, article no. 706.For guidance on citations see FAQs.c© 2015 Cambridge Publications LimitedVersion: Version of RecordCopyright and Moral Rights for the articles on this site are retained by the individual authors and/or other copyrightowners. For more information on Open Research Online’s data policy on reuse of materials please consult the policiespage.oro.open.ac.uk Goldschmidt2015 Abstracts   706 The vital aspects of reconstructing seawater Li isotope composition: insights from modern shells and cultured organisms M. DELLINGER1*, A. J. WEST1, J. F. ADKINS2, G. PARIS2,  P. FREITAS3, M. L. BAGARD4, R. EAGLE5, J. RIES6 AND  F. CORSETTI1 1University of Southern California, Los Angeles, USA (*correspondence: mdelling@usc.edu)  2California Institute of Technology, Pasadena, USA 3Instituto Português do Mar e da Atmosfera, Lisboa, Portugal  4The Open University, Milton Keynes, United Kingdom 5University of California Los Angeles, Los Angeles, USA 6Northeastern University, Nahant, USA  In this study, we constrain the fractionation of Lithium (Li) isotopes between calcite or aragonite and seawater (Δ7Licarbonate–seawater) during the precipitation of carbonate shells. There is currently a growing interest in measuring Li isotopes in sedimentary carbonates to determine paleo-weathering conditions, with implications for understanding the carbon cycle over geologic time. While the incorporation of Li isotopes in foraminifera is now better understood, these are absent from most of the geologic record, and little is known about the preservation of seawater Li isotope compositions (δ7Li) in other types of biogenic carbonates. Here, we investigate the δ7Li of various organisms (mollusc, echinoderms and corals) abundant in Phanerozoic carbonates, in order to understand which geologic archives might allow us to reconstruct past seawater composition. The range of measured samples includes (i) modern calcite and aragonite shells from variable natural environments, and (ii) shells from organisms grown under controlled conditions (temperature, salinity, pCO2). This dataset will make it possible to evaluate the influence of environmental parameters on Li isotope fractionation during biogenic calcification and to determine the magnitude of inter-species variability. To separate the carbonate fraction, we use a leaching protocol that includes removal of the exchangeable Li and weak HCl leach to avoid potential silicate contamination. Our initial results show a preferential incorporation of 7Li in calcitic shells compared to seawater. The measured values of Δ7Licalcite–seawater for bivalve species range from +2 to +15‰ with some interspecies variability. These values are higher than inorganic calcite fractionation (Δ7Licalcite–seawater = −2 to −5‰) [1], suggesting a strong influence of vital effects on Li isotopes during bio-calcification of bivalve shells. Cultured experiments of Pecten Maximum (bivalve) show little change of Δ7Licalcite–seawater as a function of temperature. On the contrary, the Δ7Liaragonite–seawater measured in aragonitic bivalves range from −8 to −13‰ and is close to but slightly more positive than the Δ7Liaragonite–seawater determined from abiogenic aragonite precipitation experiments (Δ7Liaragonite–seawater ≈ −12‰) [1] suggesting less fractionation due to vital effects for aragonite than for calcite. This work has important implications for using Li isotopes in carbonates to quantify paleo-weathering in the geological record.  [1] Marriott at al., (2004) Chemical Geology, 212(1), 5-15 706

The vital aspects of reconstructing seawater Li isotope composition: insights from modern shells and cultured organisms

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The vital aspects of reconstructing seawater Li isotope composition: insights from modern shells and cultured organisms

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