Chemical isolation and isotopic analysis of terrigenous sediments with emphasis on effective removal of contaminating marine phases including barite
Chemical isolation and isotopic analysis of terrigenous sediments with emphasis on effective removal of contaminating marine phases including barite
The radiogenic isotope composition (e.g.
87Sr/
86Sr and ε
Nd) of the terrigenous fraction is commonly used to determine the provenance and transport history of sediments. In ocean sediments, the terrigenous fraction must be isolated prior to analysis to avoid contamination by marine phases. While the removal of calcium carbonate, organic matter, biogenic opal, authigenic coatings and adsorbed cations is widely advised, steps to remove all these phases are not consistently employed, and there is no standard procedure for the effective removal of marine barite. Marine barite is found throughout the world's oceans, particularly in regions of high export production, is highly enriched in strontium (Sr) and therefore has the potential to bias measurements of terrigenous
87Sr/
86Sr towards seawater. Here we present results from sequential leaching experiments on marine sediments from the Atlantic and the Pacific Oceans to quantitatively determine the contaminating effect on
87Sr/
86Sr and ε
Nd exerted by the presence of barite and develop a protocol to successfully isolate the terrigenous fraction. Our results show that marine barite can skew measurements of terrigenous
87Sr/
86Sr by >0.01 towards the
87Sr/
86Sr value of seawater, and we highlight the importance of assessing the location-specific impact of barite contamination on terrigenous
87Sr/
86Sr. Our results show that marine barite can severely contaminate terrigenous
87Sr/
86Sr, even where marine barite accumulation rates are modest (< ~5 mg/m
3/yr and <~20 g C/m
2/yr, respectively). Barite contains Nd in very low concentrations so barite contamination of terrigenous ε
Nd is not a major concern but an important aspect of our protocol is that it has minimal effect on terrigenous ε
Nd, allowing
87Sr/
86Sr and ε
Nd to be analysed on identically cleaned aliquots. Our systematic graduated approach will help standardise
87Sr/
86Sr data, allow for robust comparisons between sites, and will contribute to an improved understanding of the provenance, transport and weathering histories of windblown continental dust and riverine sediments.
Marine barite, Sr/ Sr, Terrigenous fraction of sediment, ε
Jewell, Amy M.
3de1a5a3-b62c-4069-a06e-b2fedb6456e7
Cooper, Matthew J.
54f7bff0-1f8c-4835-8358-71eef8529e7a
Milton, J. Andrew
9e183221-d0d4-4ddb-aeba-0fdde9d31230
James, Rachael H.
79aa1d5c-675d-4ba3-85be-fb20798c02f4
Crocker, Anya J.
1215fbdd-ad43-408a-bd79-c54c6847e68c
Wilson, Paul A.
f940a9f0-fa5a-4a64-9061-f0794bfbf7c6
16 December 2021
Jewell, Amy M.
3de1a5a3-b62c-4069-a06e-b2fedb6456e7
Cooper, Matthew J.
54f7bff0-1f8c-4835-8358-71eef8529e7a
Milton, J. Andrew
9e183221-d0d4-4ddb-aeba-0fdde9d31230
James, Rachael H.
79aa1d5c-675d-4ba3-85be-fb20798c02f4
Crocker, Anya J.
1215fbdd-ad43-408a-bd79-c54c6847e68c
Wilson, Paul A.
f940a9f0-fa5a-4a64-9061-f0794bfbf7c6
Jewell, Amy M., Cooper, Matthew J., Milton, J. Andrew, James, Rachael H., Crocker, Anya J. and Wilson, Paul A.
(2021)
Chemical isolation and isotopic analysis of terrigenous sediments with emphasis on effective removal of contaminating marine phases including barite.
Chemical Geology, 589, [120673].
(doi:10.1016/j.chemgeo.2021.120673).
Abstract
The radiogenic isotope composition (e.g.
87Sr/
86Sr and ε
Nd) of the terrigenous fraction is commonly used to determine the provenance and transport history of sediments. In ocean sediments, the terrigenous fraction must be isolated prior to analysis to avoid contamination by marine phases. While the removal of calcium carbonate, organic matter, biogenic opal, authigenic coatings and adsorbed cations is widely advised, steps to remove all these phases are not consistently employed, and there is no standard procedure for the effective removal of marine barite. Marine barite is found throughout the world's oceans, particularly in regions of high export production, is highly enriched in strontium (Sr) and therefore has the potential to bias measurements of terrigenous
87Sr/
86Sr towards seawater. Here we present results from sequential leaching experiments on marine sediments from the Atlantic and the Pacific Oceans to quantitatively determine the contaminating effect on
87Sr/
86Sr and ε
Nd exerted by the presence of barite and develop a protocol to successfully isolate the terrigenous fraction. Our results show that marine barite can skew measurements of terrigenous
87Sr/
86Sr by >0.01 towards the
87Sr/
86Sr value of seawater, and we highlight the importance of assessing the location-specific impact of barite contamination on terrigenous
87Sr/
86Sr. Our results show that marine barite can severely contaminate terrigenous
87Sr/
86Sr, even where marine barite accumulation rates are modest (< ~5 mg/m
3/yr and <~20 g C/m
2/yr, respectively). Barite contains Nd in very low concentrations so barite contamination of terrigenous ε
Nd is not a major concern but an important aspect of our protocol is that it has minimal effect on terrigenous ε
Nd, allowing
87Sr/
86Sr and ε
Nd to be analysed on identically cleaned aliquots. Our systematic graduated approach will help standardise
87Sr/
86Sr data, allow for robust comparisons between sites, and will contribute to an improved understanding of the provenance, transport and weathering histories of windblown continental dust and riverine sediments.
Text
Chemical isolation and isotopic analysis of terrigenous sediments with emphasis on effective removal of contaminating marine phases including barite
- Accepted Manuscript
More information
Accepted/In Press date: 1 December 2021
e-pub ahead of print date: 9 December 2021
Published date: 16 December 2021
Additional Information:
Funding Information:
This work was supported by a PhD studentship from the Natural Environment Research Council [Grant number NE/L002531/1 ] to AMJ and Royal Society Challenge Grant CH160073 and Royal Society Wolfson Merit Award to PAW. Sediment core samples were provided by the IODP, funded by the U.S. National Science Foundation and participating countries. We are grateful to Gabriella Jardine and P. Sargent Bray for laboratory assistance. We thank Adina Paytan for useful discussions. We also thank Patrick Blaser and an anonymous reviewer for their helpful comments which improved this manuscript greatly. This contribution is dedicated to the memory of Harry Elderfield, who knew a thing or two about the chemistry of marine sediments and inspired so many of us to strive to unlock their secrets.
Keywords:
Marine barite, Sr/ Sr, Terrigenous fraction of sediment, ε
Identifiers
Local EPrints ID: 452841
URI: http://eprints.soton.ac.uk/id/eprint/452841
ISSN: 0009-2541
PURE UUID: e31cdada-fa82-4272-b7ad-33e4a8ca6a6a
Catalogue record
Date deposited: 21 Dec 2021 17:53
Last modified: 14 Jun 2024 01:53
Export record
Altmetrics
Download statistics
Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.
View more statistics
