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Communication Dans Un Congrès Année : 2023

ESR and OSL variability in quartz extracted from magmatic, metamorphic or sedimentary rock

Résumé

Sediment routing systems in fluvial catchments are primarily governed by intertwined climatic, tectonic and man-induced drivers at the centennial/millennial timescales. Among the various geomor-phological and geochemical approaches developed to trace sediment dynamics, the scientific commu-nity has recently explored the potential of (palaeo-)dosimetric methods, which are extensively used to date e.g. Quaternary alluvial environments. Recently, Optically Stimulated Luminescence (OSL) and Electron Spin Resonance (ESR) signals have been successfully transposed to decipher sediment prove-nance and transport in fluvial catchments. In this context, the French ANR QUARTZ research project aims at using quartz grains as an ubiquitous marker of sediment dynamics to understand (i) how each quartz grain holds a source-specific signature, and (ii) how this signature evolves along sediment routing systems. This contribu-tion specifically focuses on the first research topic. Quartz-bearing rocks located upstream in catchments deliver the material that is usually dated by OSL and/or ESR in fluvial sequences/deposits for geological or archaeological purposes. Here, we ana-lyzed with ESR and OSL methods quartz grains originating from different source rocks in the Streng-bach and Séveraisse catchments (France), draining a low mountain range (Vosges Mountains) and the Alps (Ecrins Massif), respectively. These rocks comprise magmatic, metamorphic and sedimentary lithologies of distinct age and composition, and provide quartz minerals present in the transposed and deposited sediments. The quartz grains were analyzed with ESR and OSL methods on the quartz min-erals from different quartz-bearing rock formations in both catchments, i.e. mostly granites, gneisses and sandstones of distinct ages and/or compositions. The source-specific signature of the different ESR signals (Ti/Al ratio, signal shape, non-optically bleachable intensity of the Al centre) was investigated. The bleaching kinetics of the different ESR centres used in dating and present in these quartz from different rock types were also investigated. Depending on the history of the quartz-bearing rock and therefore of the quartz nature (magmatic, metamorphic or sedimentary), we suggest that the ESR re-sponse varies in terms of signal shapes and intensity ratios of the different centres measured. Similar-ly, quartz OSL characteristics have been investigated (OSL signal intensities, contributions of fast/medium/slow OSL components, dose-response curves and saturation behavior) between rocks of different origins, as well as the bleaching potential (residual doses) between different quartz origins. These analyses are currently complemented in a near future by quantified trace element analyses on quartz samples from the same sources. This will allow us not only to provide encouraging results in terms of tracing quartz in fluvial deposits, but also a better understanding of the processes at the origin of ESR and OSL signals variability. This will constitute a first step towards understanding the dosi-metric behaviour of the sediments to be dated, and towards even more reliable dating techniques.

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Dates et versions

hal-03957230 , version 1 (26-01-2023)

Identifiants

  • HAL Id : hal-03957230 , version 1

Citer

Hélène Tissoux, Magali Rizza, Claire Aupart, Gilles Rixhon, Pierre Valla, et al.. ESR and OSL variability in quartz extracted from magmatic, metamorphic or sedimentary rock. 17th International Luminescence and Electron Spin Resonance Dating conference (LED 2023), led2023@dtu.dk, Jun 2023, Copenhagen, Denmark. ⟨hal-03957230⟩
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