improvmenT of eaRth climAte understaNding from Signatures of calcIum and liThium Isotopes in carbONates

Description du projet

Comprendre les isotopes du lithium dans les carbonates pour reconstituer le climat

Le suivi et la mesure de la composition isotopique du lithium dans les carbonates marins jouent un rôle essentiel en tant qu’indicateur indirect de l’intensité de l’altération continentale et indicateur du paléoclimat et du cycle du carbone de notre planète. Malgré cela, l’ampleur de l’incorporation des isotopes du Li dans les carbonates n’a pas été entièrement déterminée, pas plus qu’elle ne l’a été pour les principales voies de précipitation des carbonates. Soutenu par le programme Actions Marie Skłodowska-Curie, le projet TRANSITION étudiera la manière dont différents paramètres abiotiques et biotiques influencent les archives sédimentaires carbonatées et leur évolution. Pour ce faire, il examinera l’évolution minéralogique et chimique de systèmes fluides de carbonate de calcium amorphe afin de mettre au jour de nouvelles informations essentielles.

Objectif

Lithium isotope compositions (δ7Li) of marine carbonates have been used as proxies of continental weathering intensity, and are viewed as major indicators of Earth’s paleoclimate and carbon cycle. A caveat, however, is that the extent of Li isotope incorporation in carbonates is poorly known, and has never been determined for a major carbonate precipitation pathway: non-classical crystallization via amorphous calcium carbonate (ACC) precursor phases. Calcium isotope compositions (δ44Ca) are another novel – yet under constrained regarding ACC – environmental proxy measured from sedimentary carbonates. δ44Ca may provide key insights into secondary diagenetic processes affecting carbonates. The original objective of the TRANSITION project is to define benchmark geochemical information on coupled Li and Ca isotopes in carbonates, offering a reliable paleoclimatic proxy to decipher primary environmental information (continental weathering intensity) and secondary alteration. Through pioneering laboratory experiments focusing on the formation and transformation of ACC into crystalline carbonates, TRANSITION aims to establish how different abiotic-biotic parameters influence sedimentary carbonates isotopic record and how they evolve over time. Investigating the chemical and mineralogical evolutions of the fluid-ACC-carbonate system for a full year will also improve our understanding of ACC stability and non-classical precipitation pathways (with potential outcomes to improve CO2-storing technologies efficiency). The fellowship will be achieved in two expert labs: Graz (Austria, Secondment) for ACC experiments and mineralogy characterization and Bern (Switzerland, Beneficiary) for novel isotopic proxies. Perfectly suited for the MSCA program, the project will bolster an international and multi-disciplinary scientific network from which the fellow will directly benefit, together with cutting-edge technical and theoretical training in isotope geochemistry and mineralogy.