Meghívó
Tisztelettel hívunk minden érdeklődőt a Litoszféra Fluidum Kutató Laboratórium (LRG) online szeminárium sorozatának keretében

Sendula Eszter, a Pécsi Tudományegyetem kutatójának előadására:

Redox-sensitive trace elements in fluid inclusions in halite – a proxy for redox conditions in paleoseawater?

Helyszín: Zoom (online)
Regisztráció: https://forms.gle/YUuHMCyRxR3byQnb8
Időpont: 2021. november 15. 1700

Minden érdeklődőt szeretettel várunk!

További információért:  aradi.laszloelod@ttk.elte.hu, csaba.szabo@ttk.elte.hu

Abstract

Redox-sensitive trace elements in fluid inclusions in halite – a proxy for redox conditions in paleoseawater?
Eszter Sendula
Department of Geology and Meteorology, Institute of Geography and Earth Sciences, University of Pécs

Marine anoxia has been invoked as a driver of mass extinction events and the delayed post-extinction recovery of ecosystems throughout Earth history. The evidence for Oceanic Anoxic Events (OAE) comes from the sedimentary record by combining sedimentological (pyrite framboid size distribution, preserved lamination), palaeoecological (decrease in biodiversity and fossil abundance, lack of bioturbation, presence of specialized dysaerobic fauna), and geochemical data. Geochemists who study OAEs often use minor and trace elements as paleo-redox proxies for seawater that show variations of valence state, solubility and isotope fractionation as a function of redox conditions. The concentrations of trace elements in sedimentary rocks, however, are indirect indicators of the redox state of seawater and can be subject to changes due to post-depositional remobilization during diagenesis. Primary fluid inclusions (FI) in evaporite minerals record and preserve information concerning the chemistry of evaporating seawater at the time of entrapment, and therefore provide direct information related to ancient seawater chemistry. Recent developments in microanalytical techniques, such as Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS), have made it possible to conduct quantitative multi-elemental analysis of individual FI with detection limits on the order of ng·g-1 to µg·g-1, opening a new era for the study of redox sensitive trace elements in FIs.
In this seminar, I will discuss our current knowledge about the chemical evolution of seawater throughout the Phanerozoic and during seawater evaporation, and some of the analytical challenges when it comes to determining the chemical composition of paleoseawater. I will also present a case study from the Polish Zechstein Basin, where redox sensitive trace element concentrations were successfully analyzed for the first time in individual FIs in halite. Changes in redox sensitive trace element concentrations (e.g., Fe, Mn, U, V, Mo) in the fluid inclusions point toward the development of anoxic conditions in the basin roughly coinciding with the greatest biotic crisis in Earth’s history, the End-Permian Mass Extinction event.