Séminaire site Buffon - Stromatolites as geochemical archives--using stable metal isotopes and trace element systematics to study 3.4 billion years of microbial metal cycling - Simon Hohl

Mercredi 14 décembre 2022 à 11 h

IMPMC, Salle des élèves, 2^ème étage, bâtiment 52 (« 20 allée des crapauds »), 61 rue Buffon, Paris 5^e

Simon HOHL - State Key Laboratory of Marine Geology, Université Tongji de Shanghai

Abstract

Life evolved in microbial communities for the longest time in Earth’s history. It is, however, still incompletely understood how, when and where the first habitable environments formed and how microbial communities adapted to drastic changes in the atmosphere-hydrosphere-lithosphere systems through deep time. Stromatolites, i.e., lithified microbial mats that occur in sedimentary successions from at least 3.4 billion years ago and record direct interaction of microbial life with ambient fluids; thus, they hold the potential to record the first enzymatic cycling of bio-essential elements. In this seminar, I would like to show how microbial carbonates hold the geochemical key to our understanding of the evolution of microbial life on Earth and may also provide a blueprint for planetary studies. In the last two decades, trace elemental and traditional stable isotope research further broadened our understanding of microbial interactions with the environments they thrived in. Although the behaviour and fractionation processes of different isotope systems in stromatolites and microbial mats are incompletely understood, stable metal isotope systematics of Mo, Ni, Cd and Ba in combination with trace element systematics have a unique potential to further our understanding of redox conditions, metal availability and (biogenic) metal cycling processes in microbial habitats. I will provide some insights into some isotope applications and their future perspectives to bridge the gap between geochemistry and microbiology and better understand the evolution of microbial life on Earth and beyond.