Pub Date : 2022-08-01DOI: 10.7185/geochemlet.2132cor
T.A. Halamka, J. McFarlin, A. Younkin, J. Depoy, N. Dildar, S. Kopf
{"title":"Corrigendum to “Oxygen limitation can trigger the production of branched GDGTs in culture” by Halamka et al., 2021","authors":"T.A. Halamka, J. McFarlin, A. Younkin, J. Depoy, N. Dildar, S. Kopf","doi":"10.7185/geochemlet.2132cor","DOIUrl":"https://doi.org/10.7185/geochemlet.2132cor","url":null,"abstract":"","PeriodicalId":12613,"journal":{"name":"Geochemical Perspectives Letters","volume":null,"pages":null},"PeriodicalIF":4.9,"publicationDate":"2022-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47937298","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Carbonaceous chondrites are pristine witnesses of the formation of the solar system. Among them, the carbon-rich Tarda and Tagish Lake meteorites are thought to have sampled very distant regions of the outer circumsolar disk (Hiroi et al ., 2001). Here, we show that their noble gas isotopic compositions (especially 129 Xe excesses) are similar, implying their formation in comparable environments. Combined with literature data, we show that the radiogenic excesses of 129 Xe relative to solar wind in carbonaceous chondrites define anti-correlations with their respective iodine and carbon contents. These trends do not result from the heterogeneous distribution of 129 I in the disk but rather evidence a xenon dilution effect; the radiogenic 129 Xe excesses being dominated by trapped xenon in the most carbon-rich carbonaceous chondrites. Our data also suggest that both Tarda and Tagish Lake accreted beyond 10 astronomical units, in regions of the disk that were cold enough for CO 2 to condense.
{"title":"Origin of radiogenic 129Xe variations in carbonaceous chondrites","authors":"G. Avice, M. Meier, Y. Marrocchi","doi":"10.7185/geochemlet.2228","DOIUrl":"https://doi.org/10.7185/geochemlet.2228","url":null,"abstract":"Carbonaceous chondrites are pristine witnesses of the formation of the solar system. Among them, the carbon-rich Tarda and Tagish Lake meteorites are thought to have sampled very distant regions of the outer circumsolar disk (Hiroi et al ., 2001). Here, we show that their noble gas isotopic compositions (especially 129 Xe excesses) are similar, implying their formation in comparable environments. Combined with literature data, we show that the radiogenic excesses of 129 Xe relative to solar wind in carbonaceous chondrites define anti-correlations with their respective iodine and carbon contents. These trends do not result from the heterogeneous distribution of 129 I in the disk but rather evidence a xenon dilution effect; the radiogenic 129 Xe excesses being dominated by trapped xenon in the most carbon-rich carbonaceous chondrites. Our data also suggest that both Tarda and Tagish Lake accreted beyond 10 astronomical units, in regions of the disk that were cold enough for CO 2 to condense.","PeriodicalId":12613,"journal":{"name":"Geochemical Perspectives Letters","volume":null,"pages":null},"PeriodicalIF":4.9,"publicationDate":"2022-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41778478","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Siderophores and the formation of cerium anomalies in anoxic environments","authors":"D. Kraemer, M. Bau","doi":"10.7185/geochemlet.2227","DOIUrl":"https://doi.org/10.7185/geochemlet.2227","url":null,"abstract":"","PeriodicalId":12613,"journal":{"name":"Geochemical Perspectives Letters","volume":null,"pages":null},"PeriodicalIF":4.9,"publicationDate":"2022-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43321961","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
B. Laurent, J. Maillard, C. Afonso, G. Danger, P. Giusti, L. Remusat
Primitive carbonaceous chondrites exhibit an unparalleled diversity in terms of their organic content, in addition to a variable degree of hydrothermal alteration. Whether this diversity results from the circulation of fluids or from a multiplicity of precursors remains an open question of prime interest to understand the formation of carbonaceous asteroids. We applied laser desorption ionization Fourier transform ion cyclotron resonance mass spectrometry (LDI-FTICR-MS) on the macromolecular carbon of recent CM carbonaceous chondrite falls, as well as Orgueil (CI) and Tarda (C2). We probed the diversity of molecular fragments released under low power laser beam. The abundance of the chemical families is correlated to the extent of aqueous alteration, which promotes a structural aromatisation. The weakly altered Paris has retained the largest chemical heterogeneity, whilst it is lost in more altered chondrites. Orgueil and Tarda insoluble organic matter share similarities; this is consistent with Tarda and Orgueil originating from the outer belt region. Applied to returned asteroidal samples, FTICR-MS may help unravelling the origin and evolution of organic compounds during the early stages of the solar system.
{"title":"Diversity of chondritic organic matter probed by ultra-high resolution mass spectrometry","authors":"B. Laurent, J. Maillard, C. Afonso, G. Danger, P. Giusti, L. Remusat","doi":"10.7185/geochemlet.2224","DOIUrl":"https://doi.org/10.7185/geochemlet.2224","url":null,"abstract":"Primitive carbonaceous chondrites exhibit an unparalleled diversity in terms of their organic content, in addition to a variable degree of hydrothermal alteration. Whether this diversity results from the circulation of fluids or from a multiplicity of precursors remains an open question of prime interest to understand the formation of carbonaceous asteroids. We applied laser desorption ionization Fourier transform ion cyclotron resonance mass spectrometry (LDI-FTICR-MS) on the macromolecular carbon of recent CM carbonaceous chondrite falls, as well as Orgueil (CI) and Tarda (C2). We probed the diversity of molecular fragments released under low power laser beam. The abundance of the chemical families is correlated to the extent of aqueous alteration, which promotes a structural aromatisation. The weakly altered Paris has retained the largest chemical heterogeneity, whilst it is lost in more altered chondrites. Orgueil and Tarda insoluble organic matter share similarities; this is consistent with Tarda and Orgueil originating from the outer belt region. Applied to returned asteroidal samples, FTICR-MS may help unravelling the origin and evolution of organic compounds during the early stages of the solar system.","PeriodicalId":12613,"journal":{"name":"Geochemical Perspectives Letters","volume":null,"pages":null},"PeriodicalIF":4.9,"publicationDate":"2022-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43424031","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
X.-N. Liu, R. Hin, C. Coath, M. van Soest, E. Melekhova, T. Elliott
We determined equilibrium Mg isotope fractionation between olivine and melt ( Δ 26/24 Mg Ol/melt ) in five, naturally quenched, olivine-glass pairs that were selected to show clear textural and chemical evidence of equilibration. We employed a high-precision, critical mixture double-spiking approach to obtain a weighted mean of Δ 26/24 Mg Ol/melt = − 0.071 ± 0.010 ‰ , for values corrected to a common olivine-glass temperature of 1438 K. As function of temperature, the fractionation can be expressed as Δ 26/24 Mg Ol/melt = ( − 1.46 ± 0.26) × 10 5 / T 2 . The samples analysed have variable H 2 O content from 0.1 to ∼ 1.2 wt. %, yet no discernible difference in Δ 26/24 Mg Ol/melt was evident. We have used this Δ 26/24 Mg Ol/melt to revisit the puzzling issue of elevated Mg isotope ratios in arc lavas. In new Mg isotope data on sample suites from the Lesser Antilles and Mariana arcs, we show that primitive samples have MORB-like Mg isotope ratios while the evolved samples tend to have isotopically heavier compositions. The magnitude of this variability is well explained by olivine fractionation during magmatic differentiation as calculated with our new equilibrium Δ 26/24 Mg Ol/melt .
{"title":"Equilibrium olivine-melt Mg isotopic fractionation explains high δ26Mg values in arc lavas","authors":"X.-N. Liu, R. Hin, C. Coath, M. van Soest, E. Melekhova, T. Elliott","doi":"10.7185/geochemlet.2226","DOIUrl":"https://doi.org/10.7185/geochemlet.2226","url":null,"abstract":"We determined equilibrium Mg isotope fractionation between olivine and melt ( Δ 26/24 Mg Ol/melt ) in five, naturally quenched, olivine-glass pairs that were selected to show clear textural and chemical evidence of equilibration. We employed a high-precision, critical mixture double-spiking approach to obtain a weighted mean of Δ 26/24 Mg Ol/melt = − 0.071 ± 0.010 ‰ , for values corrected to a common olivine-glass temperature of 1438 K. As function of temperature, the fractionation can be expressed as Δ 26/24 Mg Ol/melt = ( − 1.46 ± 0.26) × 10 5 / T 2 . The samples analysed have variable H 2 O content from 0.1 to ∼ 1.2 wt. %, yet no discernible difference in Δ 26/24 Mg Ol/melt was evident. We have used this Δ 26/24 Mg Ol/melt to revisit the puzzling issue of elevated Mg isotope ratios in arc lavas. In new Mg isotope data on sample suites from the Lesser Antilles and Mariana arcs, we show that primitive samples have MORB-like Mg isotope ratios while the evolved samples tend to have isotopically heavier compositions. The magnitude of this variability is well explained by olivine fractionation during magmatic differentiation as calculated with our new equilibrium Δ 26/24 Mg Ol/melt .","PeriodicalId":12613,"journal":{"name":"Geochemical Perspectives Letters","volume":null,"pages":null},"PeriodicalIF":4.9,"publicationDate":"2022-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41644095","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
G. Pokrovski, C. Sanchez‐Valle, S. Guillot, A. Borisova, M. Muñoz, A. Auzende, O. Proux, J. Roux, J. Hazemann, D. Testemale, Y. Shvarov
Redox dynamics of subduction processes remain poorly constrained owing to the lack of direct geochemical tracers. We studied, using X-ray absorption spectroscopy, the chemical and redox state of arsenic in the Tso Morari serpentinites that are witnesses of the Himalayan subduction. Our measurements reveal remarkably contrasting redox speciation, from arsenide (As – III ) to arsenite (As III ) and arsenate (As V ). Combined with physical-chemical constraints, these data enable reconstruction of the ‘ redox travel ’ of arsenic in the subduction process. Upon early serpentinisation of mantle peridotite, arsenic was scavenged from the fluid and dragged down as insoluble nickel arsenide. Partial deserpentinisation close to the peak metamorphism (550 – 650 °C) resulted in oxidative dissolution of arsenide to aqueous As III and As V and their non-specific intake by antigorite. The As V /As III ratios ( ∼ 0.1 – 10) analysed in the mineral are ∼ 10 4 times higher on average than predicted assuming bulk system thermodynamic equilibrium. These findings reflect a transient out-of-equilibrium release of highly oxidised fluids, with f O 2 reaching ∼ 10 log units above the fayalite-magnetite-quartz buffer (FMQ þ 10). Arsenic in serpentinite is thus a sensitive record of subduction redox dynamics inaccessible when using traditional equilibrium approaches applied to bulk fluid-mineral systems.
{"title":"Redox dynamics of subduction revealed by arsenic in serpentinite","authors":"G. Pokrovski, C. Sanchez‐Valle, S. Guillot, A. Borisova, M. Muñoz, A. Auzende, O. Proux, J. Roux, J. Hazemann, D. Testemale, Y. Shvarov","doi":"10.7185/geochemlet.2225","DOIUrl":"https://doi.org/10.7185/geochemlet.2225","url":null,"abstract":"Redox dynamics of subduction processes remain poorly constrained owing to the lack of direct geochemical tracers. We studied, using X-ray absorption spectroscopy, the chemical and redox state of arsenic in the Tso Morari serpentinites that are witnesses of the Himalayan subduction. Our measurements reveal remarkably contrasting redox speciation, from arsenide (As – III ) to arsenite (As III ) and arsenate (As V ). Combined with physical-chemical constraints, these data enable reconstruction of the ‘ redox travel ’ of arsenic in the subduction process. Upon early serpentinisation of mantle peridotite, arsenic was scavenged from the fluid and dragged down as insoluble nickel arsenide. Partial deserpentinisation close to the peak metamorphism (550 – 650 °C) resulted in oxidative dissolution of arsenide to aqueous As III and As V and their non-specific intake by antigorite. The As V /As III ratios ( ∼ 0.1 – 10) analysed in the mineral are ∼ 10 4 times higher on average than predicted assuming bulk system thermodynamic equilibrium. These findings reflect a transient out-of-equilibrium release of highly oxidised fluids, with f O 2 reaching ∼ 10 log units above the fayalite-magnetite-quartz buffer (FMQ þ 10). Arsenic in serpentinite is thus a sensitive record of subduction redox dynamics inaccessible when using traditional equilibrium approaches applied to bulk fluid-mineral systems.","PeriodicalId":12613,"journal":{"name":"Geochemical Perspectives Letters","volume":null,"pages":null},"PeriodicalIF":4.9,"publicationDate":"2022-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42925128","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2022-07-01DOI: 10.7185/geochemlet.2222cor
X. Zhang, X. Peng
{"title":"Corrigendum to “How long for plastics to decompose in the deep sea?” by Zhang and Peng, 2022","authors":"X. Zhang, X. Peng","doi":"10.7185/geochemlet.2222cor","DOIUrl":"https://doi.org/10.7185/geochemlet.2222cor","url":null,"abstract":"","PeriodicalId":12613,"journal":{"name":"Geochemical Perspectives Letters","volume":null,"pages":null},"PeriodicalIF":4.9,"publicationDate":"2022-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44658557","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
G. Laukert, I. Peeken, D. Bauch, T. Krumpen, E. Hathorne, K. Werner, M. Gutjahr, M. Frank
https://doi.org/10.7185/geochemlet.2220 Radiogenic neodymium (Nd) isotopes (εNd) have the potential to serve as a geochemical tracer of the marine origin of Arctic sea ice. This capability results from pronounced εNd differences between the distinct marine and riverine sources, which feed the surface waters from which the ice forms. The first dissolved Nd isotope and rare earth element (REE) concentration data obtained from Arctic sea ice collected across the Fram Strait during RV Polarstern cruise PS85 in 2014 confirm the incorporation and preservation of the parental surface seawater εNd signatures despite efficient REE rejection. The large εNd variability between ice floes and within sea ice cores (−32 to −10) reflects changes in water mass distribution during ice growth and drift from the central Arctic Ocean to Fram Strait. In addition to the parental seawater composition, our new approach facilitates the reconstruction of the transfer of matter between the atmosphere, the sea ice and the ocean. In conjunction with satellite-derived drift trajectories, we enable a more accurate assessment of sea ice origin and spatiotemporal evolution, benefiting studies of sea ice biology, biodiversity, and biogeochemistry. Received 6 January 2022 | Accepted 5 May 2022 | Published 10 June 2022
{"title":"Neodymium isotopes trace marine provenance of Arctic sea ice","authors":"G. Laukert, I. Peeken, D. Bauch, T. Krumpen, E. Hathorne, K. Werner, M. Gutjahr, M. Frank","doi":"10.7185/geochemlet.2220","DOIUrl":"https://doi.org/10.7185/geochemlet.2220","url":null,"abstract":"https://doi.org/10.7185/geochemlet.2220 Radiogenic neodymium (Nd) isotopes (εNd) have the potential to serve as a geochemical tracer of the marine origin of Arctic sea ice. This capability results from pronounced εNd differences between the distinct marine and riverine sources, which feed the surface waters from which the ice forms. The first dissolved Nd isotope and rare earth element (REE) concentration data obtained from Arctic sea ice collected across the Fram Strait during RV Polarstern cruise PS85 in 2014 confirm the incorporation and preservation of the parental surface seawater εNd signatures despite efficient REE rejection. The large εNd variability between ice floes and within sea ice cores (−32 to −10) reflects changes in water mass distribution during ice growth and drift from the central Arctic Ocean to Fram Strait. In addition to the parental seawater composition, our new approach facilitates the reconstruction of the transfer of matter between the atmosphere, the sea ice and the ocean. In conjunction with satellite-derived drift trajectories, we enable a more accurate assessment of sea ice origin and spatiotemporal evolution, benefiting studies of sea ice biology, biodiversity, and biogeochemistry. Received 6 January 2022 | Accepted 5 May 2022 | Published 10 June 2022","PeriodicalId":12613,"journal":{"name":"Geochemical Perspectives Letters","volume":null,"pages":null},"PeriodicalIF":4.9,"publicationDate":"2022-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44448685","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
X.‐M. Liu, R. Gaschnig, R. Rudnick, R. Hazen, A. Shahar
https://doi.org/10.7185/geochemlet.2221 The Fe isotopic composition of twenty four glacial diamictite composites with depositional ages ranging from theMesoarchean to the Palaeozoic serve as proxies of the average upper continental crust (UCC) and can be used to track how δ56Fe may have changed in the continental crust through time. The diamictites have elevated chemical index of alteration (CIA) values and other characteristics of weathered regoliths (e.g., strong depletion in soluble elements such as Sr), which they inherited from their upper crustal source regions. The δ56Fe values in the diamictite composites range from −0.59 ‰ to þ0.23 ‰. Excluding three samples impacted by the incorporation of materials from Fe formations, the diamictites have an average δ56Fe of 0.12 ± 0.13 ‰ (2σ), overlapping the recent estimated average δ56Fe of 0.09 ± 0.03 ‰ (2 s.d.) in the upper continental crust (Dauphas et al., 2017, and references therein). There is no obvious correlation between δ56Fe of the glacial diamictites and the CIA. Our data suggest that the Fe isotope composition of the upper continental crust has been relatively constant throughout Earth history and that chemical weathering is not important in producing Fe isotope variations in the upper continental crust. Pre-Great Oxidation Event (GOE) anoxic weathering, when iron was soluble in its divalent state, did not generate different Fe isotopic signatures from the post-GOE oxidative weathering environment in the upper continental crust. Therefore, the large Fe isotopic fractionations observed in various marine sedimentary records are likely due to processes occurring in the oceans (e.g., biological activity) rather than abiotic redox reactions on the continents. Received 4 March 2021 | Accepted 28 April 2022 | Published 10 June 2022
https://doi.org/10.7185/geochemlet.2221沉积年龄从中太古代到古生代的24种冰川杂岩复合物的Fe同位素组成是平均上大陆地壳（UCC）的代表，可用于跟踪δ56Fe在大陆地壳中随时间的变化。杂岩具有较高的化学蚀变指数（CIA）值和风化风化层的其他特征（例如，可溶性元素（如Sr）的强烈贫化），这些特征是从其上部地壳源区继承的。杂岩复合物中的δ56Fe值范围为-0.59‰至0.23‰。不包括三个受Fe地层物质结合影响的样品，杂岩的平均δ56Fe为0.12±0.13‰（2σ），与最近估计的上大陆地壳的平均δ56 Fe 0.09±0.03‰（2 s.d.）重叠（Dauphas et al.，2017，及其参考文献）。δ56Fe与CIA无明显相关性。我们的数据表明，在整个地球历史上，上大陆地壳的Fe同位素组成一直相对恒定，化学风化在上大陆地壳中产生Fe同位素变化并不重要。大氧化事件前缺氧风化，当铁以二价状态溶解时，在上部大陆地壳中，没有产生与大氧化事件后氧化风化环境不同的铁同位素特征。因此，在各种海洋沉积记录中观察到的大量铁同位素分馏可能是由于海洋中发生的过程（例如生物活动），而不是大陆上的非生物氧化还原反应。2021年3月4日收到| 2022年4月28日接受| 2022年6月10日发布
{"title":"Constant iron isotope composition of the upper continental crust over the past 3 Gyr","authors":"X.‐M. Liu, R. Gaschnig, R. Rudnick, R. Hazen, A. Shahar","doi":"10.7185/geochemlet.2221","DOIUrl":"https://doi.org/10.7185/geochemlet.2221","url":null,"abstract":"https://doi.org/10.7185/geochemlet.2221 The Fe isotopic composition of twenty four glacial diamictite composites with depositional ages ranging from theMesoarchean to the Palaeozoic serve as proxies of the average upper continental crust (UCC) and can be used to track how δ56Fe may have changed in the continental crust through time. The diamictites have elevated chemical index of alteration (CIA) values and other characteristics of weathered regoliths (e.g., strong depletion in soluble elements such as Sr), which they inherited from their upper crustal source regions. The δ56Fe values in the diamictite composites range from −0.59 ‰ to þ0.23 ‰. Excluding three samples impacted by the incorporation of materials from Fe formations, the diamictites have an average δ56Fe of 0.12 ± 0.13 ‰ (2σ), overlapping the recent estimated average δ56Fe of 0.09 ± 0.03 ‰ (2 s.d.) in the upper continental crust (Dauphas et al., 2017, and references therein). There is no obvious correlation between δ56Fe of the glacial diamictites and the CIA. Our data suggest that the Fe isotope composition of the upper continental crust has been relatively constant throughout Earth history and that chemical weathering is not important in producing Fe isotope variations in the upper continental crust. Pre-Great Oxidation Event (GOE) anoxic weathering, when iron was soluble in its divalent state, did not generate different Fe isotopic signatures from the post-GOE oxidative weathering environment in the upper continental crust. Therefore, the large Fe isotopic fractionations observed in various marine sedimentary records are likely due to processes occurring in the oceans (e.g., biological activity) rather than abiotic redox reactions on the continents. Received 4 March 2021 | Accepted 28 April 2022 | Published 10 June 2022","PeriodicalId":12613,"journal":{"name":"Geochemical Perspectives Letters","volume":null,"pages":null},"PeriodicalIF":4.9,"publicationDate":"2022-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42033429","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Rare earth elements (REEs) are powerful tools to track oceanic biogeochemical processes. However, our understanding of REE sources is incomplete, leading to contro-versial interpretations regarding their oceanic cycling. Continental margin sediments are often assumed to be a major source, but the sediment pore water data required to understand the processes controlling that potential source are scarce. Here, we mea-sure and compile pore water and estuarine REE data from the Changjiang (Yangtze) estuary – East China Sea shelf. We show that release of REEs, from shallow pore water to overlying seawater, is coupled to Mn reduction. In contrast, REEs are removed in deep pore water, perhaps via formation of an authigenic REE-bearing phase. This sedimentary source can potentially explain REE addition in the estuary at mid-high salinity. Our calculations suggest that the benthic flux is the largest Nd source ( ∼ 40 %) on the East China Sea shelf. Globally, however, despite a higher benthic Nd flux on the advection-dominated shelf, the much more extensive deep ocean still domi-nates the total area-integrated benthic flux. Our results call for a more extensive investigation of the magnitude of the benthic flux of REEs to the oceans.
{"title":"Dominance of benthic flux of REEs on continental shelves: implications for oceanic budgets","authors":"K. Deng, S. Yang, J. Du, E. Lian, D. Vance","doi":"10.7185/geochemlet.2223","DOIUrl":"https://doi.org/10.7185/geochemlet.2223","url":null,"abstract":"Rare earth elements (REEs) are powerful tools to track oceanic biogeochemical processes. However, our understanding of REE sources is incomplete, leading to contro-versial interpretations regarding their oceanic cycling. Continental margin sediments are often assumed to be a major source, but the sediment pore water data required to understand the processes controlling that potential source are scarce. Here, we mea-sure and compile pore water and estuarine REE data from the Changjiang (Yangtze) estuary – East China Sea shelf. We show that release of REEs, from shallow pore water to overlying seawater, is coupled to Mn reduction. In contrast, REEs are removed in deep pore water, perhaps via formation of an authigenic REE-bearing phase. This sedimentary source can potentially explain REE addition in the estuary at mid-high salinity. Our calculations suggest that the benthic flux is the largest Nd source ( ∼ 40 %) on the East China Sea shelf. Globally, however, despite a higher benthic Nd flux on the advection-dominated shelf, the much more extensive deep ocean still domi-nates the total area-integrated benthic flux. Our results call for a more extensive investigation of the magnitude of the benthic flux of REEs to the oceans.","PeriodicalId":12613,"journal":{"name":"Geochemical Perspectives Letters","volume":null,"pages":null},"PeriodicalIF":4.9,"publicationDate":"2022-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47378416","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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