Séminaire / Seminar (Site Buffon) - Neha Mehta - Breathing new life into the origin of Banded Iron Formations (BIFs) by studying iron carbonate biogeochemistry

Jeudi 28 novembre 2024 à 11 h

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

Neha MEHTA - Université Libre de Bruxelles

Abstract

Earth’s redox conditions underwent a remarkable shift from an anoxic to an oxic state between 2.7 and 2.4 Ga, fundamentally reshaping its surface, atmosphere, and oceans. This transition was likely driven by a combination of geological and biological processes, but the exact triggers remain uncertain. Sedimentary archives provide the best evidence of these processes, with Banded Iron Formations (BIFs) standing out as key recorders of Earth's biogeochemical evolution. Deposited during the critical period of this redox transition, BIFs have played a prominent role in the debates about the onset of oxygenation of the Earth's atmosphere, the activity of early life on Earth, and constraining Archean seawater compositions. However, a crucial challenge in using the BIF record to interpret early Earth conditions is understanding the biogeochemical processes involved in their deposition.

In this talk, I will present my CNRS project, which focuses on understanding the formation of carbonate minerals, specifically siderite (FeCO₃), in Banded Iron Formations (BIFs). Siderite, a major phase in some BIFs, has been debated for its primary versus diagenetic origins. This mineral plays a crucial role in linking the Archean Fe and C cycles and is central to discussions about the role of life in BIF deposition. I will describe how studying the formation pathways of siderite in BIFs using advanced in situ and high-resolution analytical techniques can provide new insights into the processes behind BIF formation and their broader significance in Earth's biogeological history.