Descripción del proyecto
Análisis de la variabilidad de los isótopos del azufre en rocas sedimentarias orgánicas
El valor delta 34S (δ34S) es un método normalizado para informar sobre la proporción de dos isótopos estables del azufre, 34S:32S, en una muestra a fin de comparar la proporción equivalente con una referencia estándar conocida. El método ha sido ampliamente utilizado para reconstruir las condiciones paleoredox de los entornos primigenios de la Tierra. Las datos actuales de δ34S para isótopos del azufre en rocas de pirita posiblemente no reflejan la composición exacta del isótopo depositado en la roca. El proyecto MicroS, financiado con fondos europeos, utilizará métodos analíticos «in situ» de alta resolución (espectrometría de masa de iones secundarios y espectroscopia de rayos X) para investigar la variabilidad de δ34S a microescala en rocas sedimentarias ricas en materia orgánica. El proyecto trabajará para ayudar a aumentar nuestro conocimiento de los procesos que rigen el fraccionamiento isotópico del azufre, la transferencia de δ34S al registro de la roca y su conservación a lo largo de la escala temporal geológica.
Objetivo
Sedimentary sulfur (S) isotope systematics (δ34S) has been widely used in paleoredox reconstruction of early Earth’s environments. Large-scale variations in the δ34S record are typically interpreted to reflect fluctuations in the global S cycle. However, the expression of S isotope fractionation is sensitive to open- vs. closed-system conditions and heterogeneous micro-scale δ34S patterns can form in S-bearing phases that precipitate over time in evolving pore-water conditions. Such intra-sample δ34S variability is undetectable in traditional bulk analyses, which has been the conventional approach in time-series δ34S compilations. Moreover, early- and late-stage interactions between organic matter and inorganic sulfide (thermochemical sulfate reduction) can impact δ34S signatures at different stages of sulfide formation leading to sulfide species with distinct δ34S compositions. Therefore, the existing stratigraphic bulk-rock pyrite δ34S compilations possibly integrate a whole spectrum of δ34S variability that may not reflect the depositional isotope composition. MicroS project will take advantage of high-resolution in situ analytical methods (SIMS, synchrotron-based X-ray spectroscopy) to investigate the micro-scale variability in organic-rich sedimentary rocks and its applicability to key intervals of Earth’s history. The project focuses on three organic-rich sedimentary basins: ~2.0 Ga Onega, ~2.1 Ga Francevillian and the modern Guaymas Basins, that share several characteristics, such as a semi-restricted rift environment, syndepositional magmatism and hydrocarbon seepage. By examining the δ34S composition of the co-existing sulfide species (e.g. pyrite, pyrrhotite, organic sulfur) and placing them into the geologic context of the individual basins, the project aims to decipher the current gap in understanding processes that govern S isotope fractionations, the transfer of δ34S to the rock record and its preservation over geologic time.
Ámbito científico
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Programa(s)
Régimen de financiación
MSCA-IF - Marie Skłodowska-Curie Individual Fellowships (IF)Coordinador
51005 Tartu
Estonia