Journal article
Vanadium Speciation in Ancient Shales Revealed through Synchrotron-Based X‑ray Spectroscopy
ACS earth and space chemistry, Vol.7(2), pp.416-426
16/02/2023
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Source: InCites
Abstract
Redox-sensitive trace elements, such as vanadium, are frequently used as paleoredox proxies to infer the redox status of ancient marine depositional environments. When applied to vanadium, this approach relies on an accurate understanding of vanadium geochemistry in marine sediments. This, in turn, requires the application of analytical techniques capable of providing reliable chemical information on vanadium host phases of vanadium and thus the ability to distinguish authigenic from detrital phases. The increasing availability of synchrotron-based X-ray spectroscopic techniques capable of providing chemical speciation information at both the bulk and micro-scale presents an opportunity to refine our understanding of vanadium geochemistry in ancient marine sediments. Here, we show the utility of synchrotron-based X-ray absorption near-edge structure (XANES) spectroscopy and scanning X-ray fluorescence microscopy (SXFM) for investigating vanadium host phases in ancient marine sediments. The studied samples from the 1400 Ma Xiamaling Formation came from strongly contrasting depositional settings (ranging from oxic to euxinic) with a wide range of vanadium enrichments (enrichment factors from 0.7 to 9.6), yet vanadium speciation determined by XANES was consistently found to be phyllosilicate-hosted vanadium (III). High-resolution elemental imaging by SXFM coupled with global statistical colocalization analyses revealed strong associations between vanadium and potassium, consistent with vanadium hosted by potassium-rich clay minerals. These findings, while demonstrating the power of synchrotron-based X-ray methods, imply that differentiating authigenic and detrital vanadium in ancient marine sediments is unlikely to be possible given that post-depositional processes result in similar chemical speciation for both fractions. This will also limit the reliability of vanadium isotope system studies that depend on differentiating authigenic and detrital fractions using selective extraction procedures.
Details
- Title
- Vanadium Speciation in Ancient Shales Revealed through Synchrotron-Based X‑ray Spectroscopy
- Creators
- William W. Bennett - University of Southern DenmarkEnzo Lombi - University of South AustraliaKirk G. Scheckel - Environmental Protection AgencyRyo Sekine - Griffith UniversityScott G. Johnston - Southern Cross UniversityEdward D. Burton - Southern Cross UniversityDaryl L. Howard - Australian SynchrotronPeter Kappen - Australian SynchrotronDonald E. Canfield - University of Southern Denmark
- Publication Details
- ACS earth and space chemistry, Vol.7(2), pp.416-426
- Publisher
- American Chemical Society
- Identifiers
- 991013089140002368
- Copyright
- © 2023 American Chemical Society.
- Academic Unit
- Faculty of Science and Engineering; Science
- Language
- English
- Resource Type
- Journal article