Pub Date : 2024-10-05DOI: 10.1016/j.gca.2024.10.003
Zvi Steiner, Alexandra V. Turchyn, Patrizia Ziveri, Alan M. Shiller, Phoebe J. Lam, Adina Paytan, Eric P. Achterberg
The water column distributions of the alkaline earth metals strontium (Sr) and barium (Ba) were studied along a transect from Hawaii to Alaska. Despite similarity in the chemical properties of Sr and Ba, we find that changes in their concentrations along the transect are governed by different chemical and biological processes, meaning that these elements can be treated as independent variables in modern and ancient environments. Alaskan margin sediments are a particularly important source of dissolved Ba to the North Pacific, likely through a combination of saline submarine groundwater discharge and reductive dissolution of manganese (Mn) oxides. Abyssal North Pacific sediments are also a source of Ba to the bottom waters but a sink for Sr. We find that over 90 % of the water column variability in Sr concentrations is driven by precipitation and dissolution of the celestine (SrSO4) skeletons of Acantharia. However, the high Ba content of Acantharia celestine accounts for only 5–8 % of the global ocean variability in Ba concentrations in the water column. Similarly, the effects of barite (BaSO4) precipitation and/or dissolution on the marine Sr cycle is negligible, accounting for <1 % of the water column concentration structure for Sr and ∼3 % of the sedimentary Sr burial. The Sr-Ba-PO4 concentration distributions in the North Pacific are inconsistent with significant export of barite to the deep ocean and sediment. This suggests most of the barite formed at intermediate depths dissolves at similar horizons to its formation. The Ba content of phytoplankton organic matter is too low to constitute a major source for particulate Ba in the mesopelagic North Pacific, which suggests Ba is concentrated in marine aggregates by heterotrophic micro-organisms.
我们沿着从夏威夷到阿拉斯加的一条横断面研究了碱土金属锶（Sr）和钡（Ba）在水体中的分布。尽管锶和钡的化学性质相似，但我们发现它们在横断面上的浓度变化受不同的化学和生物过程的控制，这意味着这些元素在现代和古代环境中可被视为独立变量。阿拉斯加边缘沉积物是北太平洋溶解钡的一个特别重要的来源，可能是通过含盐海底地下水排放和锰（Mn）氧化物的还原溶解共同作用产生的。我们发现，超过 90% 的水体 Sr 浓度变化是由 Acantharia 的天青石（SrSO4）骨架的沉淀和溶解引起的。然而，在全球海洋水体中钡浓度的变化中，刺芹中的高钡含量仅占5-8%。同样，重晶石（BaSO4）的沉淀和/或溶解对海洋锶循环的影响微乎其微，只占水柱锶浓度结构的1%和沉积锶埋藏量的∼3%。北太平洋的 Sr-Ba-PO4 浓度分布与重晶石大量出口到深海和沉积物的情况不符。这表明在中间深度形成的重晶石大多溶解在与其形成相似的地层中。浮游植物有机物中的钡含量太低，不足以构成中层北太平洋微粒钡的主要来源，这表明钡被异养微生物浓缩在海洋聚集体中。
{"title":"The roles of celestine and barite in modulating strontium and barium water column concentrations in the northeast Pacific Ocean","authors":"Zvi Steiner, Alexandra V. Turchyn, Patrizia Ziveri, Alan M. Shiller, Phoebe J. Lam, Adina Paytan, Eric P. Achterberg","doi":"10.1016/j.gca.2024.10.003","DOIUrl":"https://doi.org/10.1016/j.gca.2024.10.003","url":null,"abstract":"The water column distributions of the alkaline earth metals strontium (Sr) and barium (Ba) were studied along a transect from Hawaii to Alaska. Despite similarity in the chemical properties of Sr and Ba, we find that changes in their concentrations along the transect are governed by different chemical and biological processes, meaning that these elements can be treated as independent variables in modern and ancient environments. Alaskan margin sediments are a particularly important source of dissolved Ba to the North Pacific, likely through a combination of saline submarine groundwater discharge and reductive dissolution of manganese (Mn) oxides. Abyssal North Pacific sediments are also a source of Ba to the bottom waters but a sink for Sr. We find that over 90 % of the water column variability in Sr concentrations is driven by precipitation and dissolution of the celestine (SrSO<ce:inf loc=\"post\">4</ce:inf>) skeletons of Acantharia. However, the high Ba content of Acantharia celestine accounts for only 5–8 % of the global ocean variability in Ba concentrations in the water column. Similarly, the effects of barite (BaSO<ce:inf loc=\"post\">4</ce:inf>) precipitation and/or dissolution on the marine Sr cycle is negligible, accounting for <1 % of the water column concentration structure for Sr and ∼3 % of the sedimentary Sr burial. The Sr-Ba-PO<ce:inf loc=\"post\">4</ce:inf> concentration distributions in the North Pacific are inconsistent with significant export of barite to the deep ocean and sediment. This suggests most of the barite formed at intermediate depths dissolves at similar horizons to its formation. The Ba content of phytoplankton organic matter is too low to constitute a major source for particulate Ba in the mesopelagic North Pacific, which suggests Ba is concentrated in marine aggregates by heterotrophic micro-organisms.","PeriodicalId":327,"journal":{"name":"Geochimica et Cosmochimica Acta","volume":"33 1","pages":""},"PeriodicalIF":5.0,"publicationDate":"2024-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142673569","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}
Mantle xenoliths provide effective records of the metasomatic processes that affect continental lithosphere evolution, such as interaction with subducted components or modification via small-degree melts. Correlations between major/trace element geochemistry with stable and radiogenic isotope compositions can help constrain the source and timing of this metasomatism. We report new δ18O, δ44/40Ca, and δD values for twelve kimberlite-hosted mantle xenoliths from the Slave Craton (NWT, Canada), which show varying degrees of metasomatism. The δ18O values of olivine (δ18Ool = +5.33 ± 0.13‰; 1σ; n = 12) overlap average mantle values. Clinopyroxene and garnet δ18O values (δ18Ocpx = +5.31 ± 0.10‰; δ18Ogrt = +5.37 ± 0.23‰; 1σ) extend below those reported in most mantle peridotites and are strongly correlated with clinopyroxene δ44/40Ca (avg. = +1.00 ± 0.10‰; 1σ) and garnet δ44/40Ca (avg. = +1.18 ± 0.19‰; 1σ) respectively, extending from typical mantle values to low δ18O and high δ44/40Ca values. In general, Δ18Ocpx-ol and Δ18Ogrt-ol (ranging from −0.19‰ to +0.19‰ and from −0.56‰ to +0.35‰, respectively) are lower than expected equilibrium values at mantle temperatures. Strong negative correlations are found between δ18Ogrt and Δ18Ogrt-ol and garnet major and trace element composition (Na2O, H2O, La/YbN). Furthermore, phlogopite-bearing kelyphitic rims have δD values (avg. = −126 ± 13‰; 1σ) lower than typical mantle values. Whole rock Sm-Nd model ages and oxygen isotope diffusion modeling suggest that metasomatism occurred during the Mesozoic, shortly before kimberlite entrainment, consistent with indications from diamond-forming fluids from the Slave craton. The combined low δ18O, δD, and high δ44/40Ca signature of the mantle peridotite xenoliths, along with the age constraints, suggest the metasomatic fluid/melt is sourced from a recycled oceanic crust component related to Mesozoic subduction in western North America.
{"title":"Tracking subduction-related metasomatism of the subcontinental lithospheric mantle using Ca-, O-, and H-isotopes","authors":"S.E. Brooker , J.D. Barnes , J.C. Lassiter , A. Satkoski , D.G. Pearson","doi":"10.1016/j.gca.2024.09.036","DOIUrl":"10.1016/j.gca.2024.09.036","url":null,"abstract":"<div><div>Mantle xenoliths provide effective records of the metasomatic processes that affect continental lithosphere evolution, such as interaction with subducted components or modification via small-degree melts. Correlations between major/trace element geochemistry with stable and radiogenic isotope compositions can help constrain the source and timing of this metasomatism. We report new δ<sup>18</sup>O, δ<sup>44/40</sup>Ca, and δD values for twelve kimberlite-hosted mantle xenoliths from the Slave Craton (NWT, Canada), which show varying degrees of metasomatism. The δ<sup>18</sup>O values of olivine (δ<sup>18</sup>O<sub>ol</sub> = +5.33 ± 0.13‰; 1σ; n = 12) overlap average mantle values. Clinopyroxene and garnet δ<sup>18</sup>O values (δ<sup>18</sup>O<sub>cpx</sub> = +5.31 ± 0.10‰; δ<sup>18</sup>O<sub>grt</sub> = +5.37 ± 0.23‰; 1σ) extend below those reported in most mantle peridotites and are strongly correlated with clinopyroxene δ<sup>44/40</sup>Ca (avg. = +1.00 ± 0.10‰; 1σ) and garnet δ<sup>44/40</sup>Ca (avg. = +1.18 ± 0.19‰; 1σ) respectively, extending from typical mantle values to low δ<sup>18</sup>O and high δ<sup>44/40</sup>Ca values. In general, Δ<sup>18</sup>O<sub>cpx-ol</sub> and Δ<sup>18</sup>O<sub>grt-ol</sub> (ranging from −0.19‰ to +0.19‰ and from −0.56‰ to +0.35‰, respectively) are lower than expected equilibrium values at mantle temperatures. Strong negative correlations are found between δ<sup>18</sup>O<sub>grt</sub> and Δ<sup>18</sup>O<sub>grt-ol</sub> and garnet major and trace element composition (Na<sub>2</sub>O, H<sub>2</sub>O, La/Yb<sub>N</sub>). Furthermore, phlogopite-bearing kelyphitic rims have δD values (avg. = −126 ± 13‰; 1σ) lower than typical mantle values. Whole rock Sm-Nd model ages and oxygen isotope diffusion modeling suggest that metasomatism occurred during the Mesozoic, shortly before kimberlite entrainment, consistent with indications from diamond-forming fluids from the Slave craton. The combined low δ<sup>18</sup>O, δD, and high δ<sup>44/40</sup>Ca signature of the mantle peridotite xenoliths, along with the age constraints, suggest the metasomatic fluid/melt is sourced from a recycled oceanic crust component related to Mesozoic subduction in western North America.</div></div>","PeriodicalId":327,"journal":{"name":"Geochimica et Cosmochimica Acta","volume":"385 ","pages":"Pages 16-33"},"PeriodicalIF":4.5,"publicationDate":"2024-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142421785","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 : 2024-10-03DOI: 10.1016/j.gca.2024.09.035
Y.Y. He, S. Bernard, M. Lecasble, J.-C. Viennet, I. Criouet, D. Boulesteix, N. Khodorova, L. Delbes, M. Guillaumet, F. Baudin, B. Laurent, A. Buch, L. Remusat
Carbonaceous chondrites contain amino acids, with variable abundances and isotope compositions between and within carbonaceous chondrites. The parent body processes, and the presence of clay minerals may explain those differences. Here, we experimentally investigate the evolution of 6 amino acids (glycine, β-alanine, α-alanine, 2-aminoisobutyric acid, γ-aminobutyric acid, and isovaline) exposed to hydrothermal conditions in the presence or absence of silicates. We determined the chemical nature and isotopic composition of the organic compounds of the soluble and solid fractions of the residues using X-ray diffraction, spectroscopy, and mass-spectrometry methods. Glycine and α-alanine exhibit a rather high stability, which is consistent with the measured abundances of α-alanine and glycine in chondrites having experienced various degrees of aqueous alteration. In the meantime, the evolution of β-alanine under hydrothermal conditions leads to the formation of a new compound, which likely results from the decarboxylation and deamination of β-alanine followed by recombination. More than 95 % of γ-ABA was transformed into 2-pyrrolidione though self-cyclization during the aqueous alteration. The solid residues of the experiments conducted in the presence of clay minerals contain organic material, with abundances varying depending on the amino acid used for the experiments (TOC isovaline > 2-aminoisobutyric acid > γ-aminobutyric acid > glycine > α-alanine > β-alanine). Clay minerals thus preferentially trap branched amino acids over chained amino acids, likely within their interlayer spaces as suggested by XRD data. The δ13C values of amino acids have not changed significantly during the experiments, even with the presence of silicates. Thus, the δ13C values of amino acids reported in CR and CM chondrites likely relate to synthetic conditions or the origin of their precursors (i.e. inherited from the pre-accretion processes).
碳质软岩含有氨基酸，在碳质软岩之间和碳质软岩内部，氨基酸的丰度和同位素组成各不相同。母体过程和粘土矿物的存在可能是造成这些差异的原因。在这里，我们通过实验研究了6种氨基酸（甘氨酸、β-丙氨酸、α-丙氨酸、2-氨基异丁酸、γ-氨基丁酸和异戊酸）在存在或不存在硅酸盐的热液条件下的演变过程。我们使用 X 射线衍射、光谱和质谱方法测定了残留物可溶部分和固体部分有机化合物的化学性质和同位素组成。甘氨酸和α-丙氨酸表现出相当高的稳定性，这与在经历过不同程度水蚀变的软玉中测量到的α-丙氨酸和甘氨酸的丰度是一致的。与此同时，β-丙氨酸在热液条件下的演化导致了一种新化合物的形成，这种新化合物很可能是由β-丙氨酸脱羧和脱氨基后重组而成的。在水变化过程中，95% 以上的 γ-ABA 通过自我环化转化为 2-吡咯烷酮。在有粘土矿物存在的情况下进行的实验的固体残留物含有有机物质，其丰度随实验所用氨基酸的不同而变化（TOC 异戊酸；2-氨基异丁酸；γ-氨基丁酸；甘氨酸；α-丙氨酸）。因此，粘土矿物更倾向于捕获支链氨基酸，而不是链状氨基酸，这很可能与 XRD 数据所表明的那样，是在它们的层间空隙中。在实验过程中，即使存在硅酸盐，氨基酸的 δ13C 值也没有发生显著变化。因此，报告的 CR 和 CM 软骨中氨基酸的 δ13C 值很可能与合成条件或其前体的来源有关（即继承自生成前的过程）。
{"title":"The evolution of amino acids under asteroidal aqueous alteration","authors":"Y.Y. He, S. Bernard, M. Lecasble, J.-C. Viennet, I. Criouet, D. Boulesteix, N. Khodorova, L. Delbes, M. Guillaumet, F. Baudin, B. Laurent, A. Buch, L. Remusat","doi":"10.1016/j.gca.2024.09.035","DOIUrl":"https://doi.org/10.1016/j.gca.2024.09.035","url":null,"abstract":"Carbonaceous chondrites contain amino acids, with variable abundances and isotope compositions between and within carbonaceous chondrites. The parent body processes, and the presence of clay minerals may explain those differences. Here, we experimentally investigate the evolution of 6 amino acids (glycine, β-alanine, α-alanine, 2-aminoisobutyric acid, γ-aminobutyric acid, and isovaline) exposed to hydrothermal conditions in the presence or absence of silicates. We determined the chemical nature and isotopic composition of the organic compounds of the soluble and solid fractions of the residues using X-ray diffraction, spectroscopy, and mass-spectrometry methods. Glycine and α-alanine exhibit a rather high stability, which is consistent with the measured abundances of α-alanine and glycine in chondrites having experienced various degrees of aqueous alteration. In the meantime, the evolution of β-alanine under hydrothermal conditions leads to the formation of a new compound, which likely results from the decarboxylation and deamination of β-alanine followed by recombination. More than 95 % of γ-ABA was transformed into 2-pyrrolidione though self-cyclization during the aqueous alteration. The solid residues of the experiments conducted in the presence of clay minerals contain organic material, with abundances varying depending on the amino acid used for the experiments (TOC isovaline > 2-aminoisobutyric acid > γ-aminobutyric acid > glycine > α-alanine > β-alanine). Clay minerals thus preferentially trap branched amino acids over chained amino acids, likely within their interlayer spaces as suggested by XRD data. The δ<ce:sup loc=\"post\">13</ce:sup>C values of amino acids have not changed significantly during the experiments, even with the presence of silicates. Thus, the δ<ce:sup loc=\"post\">13</ce:sup>C values of amino acids reported in CR and CM chondrites likely relate to synthetic conditions or the origin of their precursors (i.e. inherited from the pre-accretion processes).","PeriodicalId":327,"journal":{"name":"Geochimica et Cosmochimica Acta","volume":"197 1","pages":""},"PeriodicalIF":5.0,"publicationDate":"2024-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142673657","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 : 2024-10-02DOI: 10.1016/j.gca.2024.09.034
Yixuan Yang, Qingze Chen, Jing Liu, Jieqi Xing, Yiping Yang, Runliang Zhu, Hongping He, Michael F. Hochella Jr.
The formation of nanominerals and mineral nanoparticles (NMMNs) has drawn broad attention due to their high reactivity and omnipresence in the environment. While the heterogeneous formation of NMMNs on surfaces of various minerals has been extensively studied, there is limited understanding of how mineral heteroaggregates influence this process. In this study, we investigated how heteroaggregates of iron (hydr)oxides and clay minerals affect the heterogeneous oxidation of aqueous Mn(II) and crystallization of manganese (hydr)oxides (MnOx). Our results revealed that iron (hydr)oxides (ferrihydrite) and clay minerals (kaolinite or montmorillonite) in heteroaggregates exerted coupled effects on these processes, dictating the distribution of Mn and the morphology of MnOx. Specifically, ferrihydrite catalyzed gradual oxidative removal of Mn(II) and triggered MnOx nucleation; in contrast, kaolinite/montmorillonite rapidly adsorbed Mn(II) but hardly catalyzed its oxidation. These reactions collectively resulted in fast adsorption and gradual oxidation of Mn(II) on the heteroaggregates. Further, MnOx nanoparticles formed on ferrihydrite surfaces migrated to kaolinite/montmorillonite surfaces, leading to interactions between MnOx and various component minerals within the heteroaggregates. This significantly altered the subsequent growth pathways and the eventual morphology of MnOx. Consequently, while MnOx nanoparticles in the ferrihydrite-only system aggregated freely and formed well-extended nanowires, those in the ferrihydrite-kaolinite system predominantly became short nanorods due to the immobilization by kaolinite surfaces; in the ferrihydrite-montmorillonite system, considerable MnOx nanoparticles attached to montmorillonite surfaces due to strong electrostatic attraction, and subsequently grew into blocky particles via particle attachment. These findings illustrate that surface reactivities of heteroaggregated ferrihydrite and kaolinite/montmorillonite are coupled when they interact with aqueous Mn(II) or MnOx. Our work exemplifies, for the first time, the cooperation between surfaces of various minerals during the heterogeneous formation of NMMNs. Findings from this study also enhance our understanding of MnOx formation on surfaces with diverse atomic structures, and contribute to the knowledge of Mn cycling in the environment.
{"title":"Coupled effects of iron (hydr)oxides and clay minerals on the heterogeneous oxidation of aqueous Mn(II) and crystallization of manganese (hydr)oxides","authors":"Yixuan Yang, Qingze Chen, Jing Liu, Jieqi Xing, Yiping Yang, Runliang Zhu, Hongping He, Michael F. Hochella Jr.","doi":"10.1016/j.gca.2024.09.034","DOIUrl":"https://doi.org/10.1016/j.gca.2024.09.034","url":null,"abstract":"The formation of nanominerals and mineral nanoparticles (NMMNs) has drawn broad attention due to their high reactivity and omnipresence in the environment. While the heterogeneous formation of NMMNs on surfaces of various minerals has been extensively studied, there is limited understanding of how mineral heteroaggregates influence this process. In this study, we investigated how heteroaggregates of iron (hydr)oxides and clay minerals affect the heterogeneous oxidation of aqueous Mn(II) and crystallization of manganese (hydr)oxides (MnO<ce:inf loc=\"post\">x</ce:inf>). Our results revealed that iron (hydr)oxides (ferrihydrite) and clay minerals (kaolinite or montmorillonite) in heteroaggregates exerted coupled effects on these processes, dictating the distribution of Mn and the morphology of MnO<ce:inf loc=\"post\">x</ce:inf>. Specifically, ferrihydrite catalyzed gradual oxidative removal of Mn(II) and triggered MnO<ce:inf loc=\"post\">x</ce:inf> nucleation; in contrast, kaolinite/montmorillonite rapidly adsorbed Mn(II) but hardly catalyzed its oxidation. These reactions collectively resulted in fast adsorption and gradual oxidation of Mn(II) on the heteroaggregates. Further, MnO<ce:inf loc=\"post\">x</ce:inf> nanoparticles formed on ferrihydrite surfaces migrated to kaolinite/montmorillonite surfaces, leading to interactions between MnO<ce:inf loc=\"post\">x</ce:inf> and various component minerals within the heteroaggregates. This significantly altered the subsequent growth pathways and the eventual morphology of MnO<ce:inf loc=\"post\">x</ce:inf>. Consequently, while MnO<ce:inf loc=\"post\">x</ce:inf> nanoparticles in the ferrihydrite-only system aggregated freely and formed well-extended nanowires, those in the ferrihydrite-kaolinite system predominantly became short nanorods due to the immobilization by kaolinite surfaces; in the ferrihydrite-montmorillonite system, considerable MnO<ce:inf loc=\"post\">x</ce:inf> nanoparticles attached to montmorillonite surfaces due to strong electrostatic attraction, and subsequently grew into blocky particles via particle attachment. These findings illustrate that surface reactivities of heteroaggregated ferrihydrite and kaolinite/montmorillonite are coupled when they interact with aqueous Mn(II) or MnO<ce:inf loc=\"post\">x</ce:inf>. Our work exemplifies, for the first time, the cooperation between surfaces of various minerals during the heterogeneous formation of NMMNs. Findings from this study also enhance our understanding of MnO<ce:inf loc=\"post\">x</ce:inf> formation on surfaces with diverse atomic structures, and contribute to the knowledge of Mn cycling in the environment.","PeriodicalId":327,"journal":{"name":"Geochimica et Cosmochimica Acta","volume":"46 1","pages":""},"PeriodicalIF":5.0,"publicationDate":"2024-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142673693","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 : 2024-10-02DOI: 10.1016/j.gca.2024.09.024
L. Nicole Arellano , Emily J. Beverly , Ny Riavo G. Voarintsoa , Christopher B. Skinner , Andrew J. Schauer , Eric J. Steig
We present one year of δD, δ18O, d-excess, and Δʹ17O data from monthly precipitation at a Caribbean coastal site in Panama and from tap waters across the country to constrain geographic, climate, and moisture source controls on isotopic variability and better understand the sources and mechanisms of precipitation in Central America, a region facing significant modifications to the annual rainfall cycle due to climate change. Monthly precipitation δD ranged from –52.2 to +14.3 ‰, δ18O from –7.6 to +0.4 ‰, d-excess from +7.1 to +11.6 ‰, and Δ′17O from +11 to +29 per meg. Rainy season precipitation samples were found to have lower δD, δ18O, and d-excess due to Rayleigh distillation during the condensation and rainout of Pacific moisture over the central cordilleras, which results in decoupling between d-excess and Δ′17O. Outlier Δ′17O values during peak dry and rainy months may reflect seasonal changes in water vapor sourcing, from Caribbean to Pacific and/or locally recycled moisture, or may be a result of organic contamination. Tap water δD ranged from –82.3 to –14.3 ‰, δ18O from –11.6 to –2.4 ‰, d-excess from +4.3 to +12.2 ‰ and Δ′17O from –2 to +84 per meg. Tap water δD and δ18O values increase eastward due to lower orographic effects and Pacific and locally recycled moisture contributions to rainfall and greater secondary evaporation. Tap water d-excess and Δ′17O values are also de-coupled but lack clear spatial trends and controls. The results of this study indicate the promise of adding Δ′17O to the isotopic toolkit in tropical mountainous regions with complicated water cycling dynamics and provide a baseline for future triple oxygen isotope investigations.
{"title":"Triple oxygen isotope variability of precipitation in a tropical mountainous region","authors":"L. Nicole Arellano , Emily J. Beverly , Ny Riavo G. Voarintsoa , Christopher B. Skinner , Andrew J. Schauer , Eric J. Steig","doi":"10.1016/j.gca.2024.09.024","DOIUrl":"10.1016/j.gca.2024.09.024","url":null,"abstract":"<div><div>We present one year of δD, δ<sup>18</sup>O, d-excess, and Δʹ<sup>17</sup>O data from monthly precipitation at a Caribbean coastal site in Panama and from tap waters across the country to constrain geographic, climate, and moisture source controls on isotopic variability and better understand the sources and mechanisms of precipitation in Central America, a region facing significant modifications to the annual rainfall cycle due to climate change. Monthly precipitation δD ranged from –52.2 to +14.3 ‰, δ<sup>18</sup>O from –7.6 to +0.4 ‰, d-excess from +7.1 to +11.6 ‰, and Δ′<sup>17</sup>O from +11 to +29 per meg. Rainy season precipitation samples were found to have lower δD, δ<sup>18</sup>O, and d-excess due to Rayleigh distillation during the condensation and rainout of Pacific moisture over the central cordilleras, which results in decoupling between d-excess and Δ′<sup>17</sup>O. Outlier Δ′<sup>17</sup>O values during peak dry and rainy months may reflect seasonal changes in water vapor sourcing, from Caribbean to Pacific and/or locally recycled moisture, or may be a result of organic contamination. Tap water δD ranged from –82.3 to –14.3 ‰, δ<sup>18</sup>O from –11.6 to –2.4 ‰, d-excess from +4.3 to +12.2 ‰ and Δ′<sup>17</sup>O from –2 to +84 per meg. Tap water δD and δ<sup>18</sup>O values increase eastward due to lower orographic effects and Pacific and locally recycled moisture contributions to rainfall and greater secondary evaporation. Tap water d-excess and Δ′<sup>17</sup>O values are also de-coupled but lack clear spatial trends and controls. The results of this study indicate the promise of adding Δ′<sup>17</sup>O to the isotopic toolkit in tropical mountainous regions with complicated water cycling dynamics and provide a baseline for future triple oxygen isotope investigations.</div></div>","PeriodicalId":327,"journal":{"name":"Geochimica et Cosmochimica Acta","volume":"385 ","pages":"Pages 1-15"},"PeriodicalIF":4.5,"publicationDate":"2024-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142421784","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 : 2024-09-29DOI: 10.1016/j.gca.2024.09.032
Jeemin H. Rhim , Sebastian Kopf , Jamie McFarlin , Ashley E. Maloney , Harpreet Batther , Carolynn M. Harris , Alice Zhou , Xiahong Feng , Yuki Weber , Shelley Hoeft-McCann , Ann Pearson , William D. Leavitt
<div><div>The stable hydrogen isotope composition of archaeal lipids is emerging as a potential paleoenvironmental proxy, adding to the well-established application of plant leaf wax-derived <em>n</em>-alkanes in paleohydrological reconstruction. A handful of studies reported relatively invariant and depleted hydrogen isotope compositions for archaeal lipids despite the range of different organisms and growth conditions explored. However, how modes of metabolism and physiological state (growth phase) affect the hydrogen isotope signatures of archaeal lipids remains poorly understood, limiting our ability to interpret archaeal lipid biomarker records from the environment. Here we conducted water isotope label experiments with a metabolically flexible and well-studied model archaeon <em>Archaeoglobus fulgidus</em> and quantified the hydrogen isotope fractionation between lipids and water in response to different carbon substrates and electron donor–acceptor pairs at different growth phases. The <sup>2</sup>H/<sup>1</sup>H fractionation between lipids and water (ε<sub>L/W</sub>) was overall negative. Both carbon metabolism and growth phase affected the magnitude of isotope fractionation in <em>A. fulgidus</em>; however, the changes in ε<sub>L/W</sub> values were relatively subtle where they ranged from –283 to –229 ‰ across all tested conditions, overlapping with the ranges observed for other archaea in previous studies. Isotope flux-balance model results suggest that ≥ 80 % and ≥ 50 % of lipid-bound H in <em>A. fulgidus</em> cultures directly reflect water isotope compositions (i.e., not via organic substrate or H<sub>2</sub>) during autotrophy and heterotrophy, respectively. The model results also suggest two main mechanisms of consistent <sup>2</sup>H depletion observed in <em>A. fulgidus</em> tetraethers as well as other archaeal lipids reported in previous studies: 1) isotopic re-equilibration via upstream isomerization reactions involving C<sub>5</sub> units and 2) downstream double bond reduction catalyzed by a flavoenzyme geranylgeranyl reductase. These results are consistent with previous isotope flux-balance model results for a different archaeon. Finally, we synthesized available data to compare ε<sub>L/W</sub> patterns across all three domains of life: Eukarya, Archaea and Bacteria. Because they vary fundamentally in lipid biosynthesis pathways, we present comparative discussions in pairs, focusing on the shared biochemical mechanisms among isoprenoid lipids and potential signals of metabolic adaptations across prokaryotic lipids. Emerging patterns between diverse archaeal and eukaryotic isoprenoid lipids are consistent with the two proposed mechanisms for <sup>2</sup>H depletion identified (isomerization and final saturation). The patterns between archaeal isoprenoids and bacterial fatty acids suggest that the general state of energy limitation may also contribute to large, negative values of ε<sub>L/W</sub> observed in prokaryotic lipi
{"title":"Metabolic imprints in the hydrogen isotopes of Archaeoglobus fulgidus tetraether lipids","authors":"Jeemin H. Rhim , Sebastian Kopf , Jamie McFarlin , Ashley E. Maloney , Harpreet Batther , Carolynn M. Harris , Alice Zhou , Xiahong Feng , Yuki Weber , Shelley Hoeft-McCann , Ann Pearson , William D. Leavitt","doi":"10.1016/j.gca.2024.09.032","DOIUrl":"10.1016/j.gca.2024.09.032","url":null,"abstract":"<div><div>The stable hydrogen isotope composition of archaeal lipids is emerging as a potential paleoenvironmental proxy, adding to the well-established application of plant leaf wax-derived <em>n</em>-alkanes in paleohydrological reconstruction. A handful of studies reported relatively invariant and depleted hydrogen isotope compositions for archaeal lipids despite the range of different organisms and growth conditions explored. However, how modes of metabolism and physiological state (growth phase) affect the hydrogen isotope signatures of archaeal lipids remains poorly understood, limiting our ability to interpret archaeal lipid biomarker records from the environment. Here we conducted water isotope label experiments with a metabolically flexible and well-studied model archaeon <em>Archaeoglobus fulgidus</em> and quantified the hydrogen isotope fractionation between lipids and water in response to different carbon substrates and electron donor–acceptor pairs at different growth phases. The <sup>2</sup>H/<sup>1</sup>H fractionation between lipids and water (ε<sub>L/W</sub>) was overall negative. Both carbon metabolism and growth phase affected the magnitude of isotope fractionation in <em>A. fulgidus</em>; however, the changes in ε<sub>L/W</sub> values were relatively subtle where they ranged from –283 to –229 ‰ across all tested conditions, overlapping with the ranges observed for other archaea in previous studies. Isotope flux-balance model results suggest that ≥ 80 % and ≥ 50 % of lipid-bound H in <em>A. fulgidus</em> cultures directly reflect water isotope compositions (i.e., not via organic substrate or H<sub>2</sub>) during autotrophy and heterotrophy, respectively. The model results also suggest two main mechanisms of consistent <sup>2</sup>H depletion observed in <em>A. fulgidus</em> tetraethers as well as other archaeal lipids reported in previous studies: 1) isotopic re-equilibration via upstream isomerization reactions involving C<sub>5</sub> units and 2) downstream double bond reduction catalyzed by a flavoenzyme geranylgeranyl reductase. These results are consistent with previous isotope flux-balance model results for a different archaeon. Finally, we synthesized available data to compare ε<sub>L/W</sub> patterns across all three domains of life: Eukarya, Archaea and Bacteria. Because they vary fundamentally in lipid biosynthesis pathways, we present comparative discussions in pairs, focusing on the shared biochemical mechanisms among isoprenoid lipids and potential signals of metabolic adaptations across prokaryotic lipids. Emerging patterns between diverse archaeal and eukaryotic isoprenoid lipids are consistent with the two proposed mechanisms for <sup>2</sup>H depletion identified (isomerization and final saturation). The patterns between archaeal isoprenoids and bacterial fatty acids suggest that the general state of energy limitation may also contribute to large, negative values of ε<sub>L/W</sub> observed in prokaryotic lipi","PeriodicalId":327,"journal":{"name":"Geochimica et Cosmochimica Acta","volume":"386 ","pages":"Pages 196-212"},"PeriodicalIF":4.5,"publicationDate":"2024-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142662968","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2024-09-27DOI: 10.1016/j.gca.2024.09.028
Ziyi Zhou , Guangyi Sun , Weiqing Zhou , Jianwei Zhou , Xinbin Feng , Y. Zou Finfrock , Peng Liu
Sorption of antimony (Sb) onto birnessite significantly influences the fate of Sb in oceanic and terrestrial environments and fractionates Sb isotopes. Nevertheless, little is known about Sb isotopic fractionation during its adsorption on birnessite. Here, we show the value of Δ123Sbadsorbed-aqueous increases from −0.398 to −0.332 ‰ in 1 h and then decreases and stabilizes at −0.384 ‰ in 72 h. The enrichment of the light Sb isotope is predominantly due to the distortion of the octahedral symmetry. X-ray absorption spectroscopy results indicate Sb first forms a double-corner-sharing complex on birnessite and then transforms to a double-edge-sharing complex during adsorption. The optimized bond distances for double-corner-sharing (3.37 Å) and double-edge-sharing (2.90 Å) complexes calculated using density functional theory (DFT) fits well with the structure (3.41 and 3.00 Å) revealed by X-ray absorption spectroscopy, respectively. The fractionation derived from reduced partition function ratios calculated using DFT aligns well with the experimental results. Therefore, the variation in Sb isotopic fractionation during adsorption is attributed to the evolving structure of Sb complexes on birnessite. Our results demonstrate the isotopic fractionation of Sb during adsorption on birnessite and provide a molecular-scale understanding of Sb behavior, contributing to the correct reconstruction of the Sb isotope composition of ancient seawater using ferromanganese crusts and nodules, and efforts to trace Sb migration in epigenetic mining environments.
锑（Sb）在白腊石上的吸附作用极大地影响了锑在海洋和陆地环境中的归宿，并使锑的同位素发生分馏。然而，人们对锑在桦锑酸盐吸附过程中的同位素分馏知之甚少。在这里，我们展示了吸附在水体中的Δ123Sb的值在1小时内从-0.398 ‰增加到-0.332 ‰，然后在72小时内降低并稳定在-0.384 ‰。X 射线吸收光谱结果表明，锑首先在比尔奈斯特上形成双角共享复合物，然后在吸附过程中转变为双边共享复合物。用密度泛函理论（DFT）计算出的双角共享复合物（3.37 Å）和双边共享复合物（2.90 Å）的优化键距分别与 X 射线吸收光谱显示的结构（3.41 Å 和 3.00 Å）非常吻合。使用 DFT 计算的还原分配函数比得出的分馏结果与实验结果非常吻合。因此，吸附过程中锑同位素分馏的变化归因于硼锰铁矿上锑络合物结构的演变。我们的研究结果证明了锑在桦锰矿上吸附过程中的同位素分馏，并提供了对锑行为的分子尺度理解，有助于利用铁锰结壳和结核正确重建古海水的锑同位素组成，并努力追踪锑在表生采矿环境中的迁移。
{"title":"Antimony stable isotope fractionation during adsorption onto birnessite: A molecular perspective from X-ray absorption spectroscopy and density functional theory","authors":"Ziyi Zhou , Guangyi Sun , Weiqing Zhou , Jianwei Zhou , Xinbin Feng , Y. Zou Finfrock , Peng Liu","doi":"10.1016/j.gca.2024.09.028","DOIUrl":"10.1016/j.gca.2024.09.028","url":null,"abstract":"<div><div>Sorption of antimony (Sb) onto birnessite significantly influences the fate of Sb in oceanic and terrestrial environments and fractionates Sb isotopes. Nevertheless, little is known about Sb isotopic fractionation during its adsorption on birnessite. Here, we show the value of Δ<sup>123</sup>Sb<sub>adsorbed-aqueous</sub> increases from −0.398 to −0.332 ‰ in 1 h and then decreases and stabilizes at −0.384 ‰ in 72 h. The enrichment of the light Sb isotope is predominantly due to the distortion of the octahedral symmetry. X-ray absorption spectroscopy results indicate Sb first forms a double-corner-sharing complex on birnessite and then transforms to a double-edge-sharing complex during adsorption. The optimized bond distances for double-corner-sharing (3.37 Å) and double-edge-sharing (2.90 Å) complexes calculated using density functional theory (DFT) fits well with the structure (3.41 and 3.00 Å) revealed by X-ray absorption spectroscopy, respectively. The fractionation derived from reduced partition function ratios calculated using DFT aligns well with the experimental results. Therefore, the variation in Sb isotopic fractionation during adsorption is attributed to the evolving structure of Sb complexes on birnessite. Our results demonstrate the isotopic fractionation of Sb during adsorption on birnessite and provide a molecular-scale understanding of Sb behavior, contributing to the correct reconstruction of the Sb isotope composition of ancient seawater using ferromanganese crusts and nodules, and efforts to trace Sb migration in epigenetic mining environments.</div></div>","PeriodicalId":327,"journal":{"name":"Geochimica et Cosmochimica Acta","volume":"386 ","pages":"Pages 173-184"},"PeriodicalIF":4.5,"publicationDate":"2024-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142662977","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 : 2024-09-27DOI: 10.1016/j.gca.2024.09.029
Yingchun Zhang, Xiandong Liu, Xiancai Lu, Rucheng Wang
Deep-sea mud shows tremendous resource potential for rare earth elements (REEs) and its formation is closely associated with sea-floor hydrothermal activities. Iron (oxyhydr)oxides link the sources and sinks of REEs in sea-floor hydrothermal systems. However, the complexation mechanisms of REEs on iron (oxyhydr)oxides have not been well understood yet. In this study, by using the first principles molecular dynamics technique, we first calculated the pKa’s of surface groups on goethite (1 1 0) surface at elevated temperatures relevant to sea-floor hydrothermal systems and then evaluated the complexation structures and free energies of REEs on goethite (1 1 0) and (0 1 0) surfaces using the method of constraint by taking Sc3+, Y3+, and La3+ as model REE cations. The results show that REE complexation occurs in mildly acidic to neutral conditions. The most thermodynamically stable complexes of REEs are bidentate complexes on two neighboring FeOH sites on goethite (1 1 0) surface and tridentate complexes on two neighboring FeOH sites plus one Fe2OH site on goethite (0 1 0) surface. Sc3+ complexes match the goethite lattice and can be incorporated into the lattice. The stabilities of REE complexes increase with the distance from hydrothermal vents. Complexation of Y3+ is less favored on goethite compared to other REEs whereas Sc3+ prefers complexation on goethite (0 1 0) surface and La3+ exhibits similar stabilities on both (0 1 0) and (1 1 0) surfaces. The derived atomic level complexation mechanisms would be helpful for the interpretation of experimental data and the prediction of REEs’ behavior in the sea-floor. The findings presented here provide valuable insights into REEs fractionation and enrichment in deep-sea muds.
{"title":"Surface complexation of rare earth elements on goethite in sea-floor hydrothermal environment: Insight from first principles simulations","authors":"Yingchun Zhang, Xiandong Liu, Xiancai Lu, Rucheng Wang","doi":"10.1016/j.gca.2024.09.029","DOIUrl":"10.1016/j.gca.2024.09.029","url":null,"abstract":"<div><div>Deep-sea mud shows tremendous resource potential for rare earth elements (REEs) and its formation is closely associated with sea-floor hydrothermal activities. Iron (oxyhydr)oxides link the sources and sinks of REEs in sea-floor hydrothermal systems. However, the complexation mechanisms of REEs on iron (oxyhydr)oxides have not been well understood yet. In this study, by using the first principles molecular dynamics technique, we first calculated the pK<sub>a</sub>’s of surface groups on goethite (1<!--> <!-->1<!--> <!-->0) surface at elevated temperatures relevant to sea-floor hydrothermal systems and then evaluated the complexation structures and free energies of REEs on goethite (1<!--> <!-->1<!--> <!-->0) and (0<!--> <!-->1<!--> <!-->0) surfaces using the method of constraint by taking Sc<sup>3+</sup>, Y<sup>3+</sup>, and La<sup>3+</sup> as model REE cations. The results show that REE complexation occurs in mildly acidic to neutral conditions. The most thermodynamically stable complexes of REEs are bidentate complexes on two neighboring <img>FeOH sites on goethite (1<!--> <!-->1<!--> <!-->0) surface and tridentate complexes on two neighboring <img>FeOH sites plus one <img>Fe<sub>2</sub>OH site on goethite (0<!--> <!-->1<!--> <!-->0) surface. Sc<sup>3+</sup> complexes match the goethite lattice and can be incorporated into the lattice. The stabilities of REE complexes increase with the distance from hydrothermal vents. Complexation of Y<sup>3+</sup> is less favored on goethite compared to other REEs whereas Sc<sup>3+</sup> prefers complexation on goethite (0<!--> <!-->1<!--> <!-->0) surface and La<sup>3+</sup> exhibits similar stabilities on both (0<!--> <!-->1<!--> <!-->0) and (1<!--> <!-->1<!--> <!-->0) surfaces. The derived atomic level complexation mechanisms would be helpful for the interpretation of experimental data and the prediction of REEs’ behavior in the sea-floor. The findings presented here provide valuable insights into REEs fractionation and enrichment in deep-sea muds.</div></div>","PeriodicalId":327,"journal":{"name":"Geochimica et Cosmochimica Acta","volume":"386 ","pages":"Pages 185-195"},"PeriodicalIF":4.5,"publicationDate":"2024-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142662979","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 : 2024-09-27DOI: 10.1016/j.gca.2024.09.031
Zheng Qin , Jingao Liu , Huan Cui , Kurt O. Konhauser , He Huang , Dongtao Xu , Yuan Gao , Huaichun Wu , Chengshan Wang
Organic carbon burial in ancient lacustrine settings is a crucial source of petroleum resources. Unlike the marine environment, the dynamics of organic carbon burial in the terrestrial realm are more complex due to the interplay of global and regional climate-tectonic factors. There appears to be a potential linkage between seawater incursion events (SWIEs) and the generation of lacustrine source rocks. However, reliable proxies to reconstruct the frequency and extent of SWIEs are currently lacking. Here, we explore the potential of rhenium-platinum group elements (Re-PGE) system as a novel proxy for determining SWIEs in the Nenjiang Formation of the lacustrine Songliao Basin in China that is noted for its high-quality source rock. By comparing marine and non-marine intervals, we validate the utility of Re-PGE fractionation patterns and osmium (Os) isotope compositions. Moreover, the Re/Ir ratios demonstrate two main episodes of quantitative seawater-lake water exchange. The comparison of variable indicators shows that the Re-PGE system is more sensitive to the changes in water sources, thus providing detailed information of frequency and exchange amount. The inverse variation between seawater contribution and total organic carbon content further implies that the massive sulfate influx from SWIEs facilitated bacterial sulfate reduction in the sediment pile, which had the effect of recycling nutrients (e.g., phosphorous) back into the water column. The SWIEs-triggered eutrophication induced a positive feedback loop between productivity and hypoxia, creating ideal conditions for the preservation of organic carbon. Our data reveals the detailed mechanism of SWIEs-triggered organic carbon burial and emphasizes the significant role of SWIEs in generating economically important hydrocarbon reservoirs.
{"title":"Rhenium-platinum group elements reveal seawater incursion induced massive lacustrine organic carbon burial","authors":"Zheng Qin , Jingao Liu , Huan Cui , Kurt O. Konhauser , He Huang , Dongtao Xu , Yuan Gao , Huaichun Wu , Chengshan Wang","doi":"10.1016/j.gca.2024.09.031","DOIUrl":"10.1016/j.gca.2024.09.031","url":null,"abstract":"<div><div>Organic carbon burial in ancient lacustrine settings is a crucial source of petroleum resources. Unlike the marine environment, the dynamics of organic carbon burial in the terrestrial realm are more complex due to the interplay of global and regional climate-tectonic factors. There appears to be a potential linkage between seawater incursion events (SWIEs) and the generation of lacustrine source rocks. However, reliable proxies to reconstruct the frequency and extent of SWIEs are currently lacking. Here, we explore the potential of rhenium-platinum group elements (Re-PGE) system as a novel proxy for determining SWIEs in the Nenjiang Formation of the lacustrine Songliao Basin in China that is noted for its high-quality source rock. By comparing marine and non-marine intervals, we validate the utility of Re-PGE fractionation patterns and osmium (Os) isotope compositions. Moreover, the Re/Ir ratios demonstrate two main episodes of quantitative seawater-lake water exchange. The comparison of variable indicators shows that the Re-PGE system is more sensitive to the changes in water sources, thus providing detailed information of frequency and exchange amount. The inverse variation between seawater contribution and total organic carbon content further implies that the massive sulfate influx from SWIEs facilitated bacterial sulfate reduction in the sediment pile, which had the effect of recycling nutrients (e.g., phosphorous) back into the water column. The SWIEs-triggered eutrophication induced a positive feedback loop between productivity and hypoxia, creating ideal conditions for the preservation of organic carbon. Our data reveals the detailed mechanism of SWIEs-triggered organic carbon burial and emphasizes the significant role of SWIEs in generating economically important hydrocarbon reservoirs.</div></div>","PeriodicalId":327,"journal":{"name":"Geochimica et Cosmochimica Acta","volume":"384 ","pages":"Pages 168-177"},"PeriodicalIF":4.5,"publicationDate":"2024-09-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142426520","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 : 2024-09-26DOI: 10.1016/j.gca.2024.09.026
Taryn Linzmeyer , James M.D. Day , Raquel Alonso-Perez , Theo Phahla , Anton Wolmarans , Andrew Rogers
<div><div>The ∼ 1.15-billion-year-old (Ga) Premier kimberlite pipe (Cullinan diamond mine), South Africa, is composed of several distinct kimberlite facies (Grey, Brown, Pale Piebald, Dark Piebald, Black Coherent [Type 3C], Blue/Brown Transitional, and Fawn). We report bulk rock Re-Os isotope data for Premier kimberlite facies, as well as for a suite of entrained peridotite and mafic xenoliths. These data are complemented by bulk rock highly siderophile element (HSE: Re, Pd, Pt, Ru, Ir, Os), major- and trace-element abundances. Measured <sup>187</sup>Os/<sup>188</sup>Os for the kimberlite facies range from 0.1223 to 0.1672 (γOs<sub>i</sub> of −2.5 to + 17.4), peridotite xenoliths range from 0.1096 to 0.1244 (γOs<sub>i</sub> of −13.3 to −1.1), and pyroxenite xenoliths range from 0.1796 to 0.938 (γOs<sub>i</sub> of + 27 to + 419). A single measured amphibolite xenolith has the most radiogenic measured <sup>187</sup>Os/<sup>188</sup>Os of 2.86 (γOs<sub>i</sub> of + 43). Harzburgite xenoliths yield time of rhenium depletion model ages (T<sub>RD</sub>) of ∼ 1.5 to 2.8 Ga, consistent with average T<sub>RD</sub> ages for Premier peridotites (2.4 ± 0.4 Ga). With these and published data, we considered the relationships between kimberlite and mantle xenoliths, compare estimates of relative peridotite incorporation to sampled diamond grade, and explore recratonization versus refertilization arguments with regards to T<sub>RD</sub> model ages. Kimberlite melt infiltration into Premier peridotite xenoliths is evident from melt veins accounting for ∼ 2 and ∼ 14 modal % of samples, and has led to incompatible element enrichment, including elevated Re. In turn, kimberlites show geochemical evidence for addition of peridotite xenolith fragments, with Type 3C having > 30 % more peridotite contribution than the Brown volcaniclastic facies. Kimberlites and peridotites plot on a <sup>187</sup>Re/<sup>188</sup>Os versus <sup>187</sup>Os/<sup>188</sup>Os mixing line (R<sup>2</sup> = 0.92), with kimberlites having older apparent ages than the true age of crystallization. This mixing line provides estimates of lithospheric incorporation into the kimberlites, where the units with higher peridotite incorporation do not correlate with diamond grade. This is likely due to lithological and post-emplacement alteration heterogeneity within the kimberlite units, perhaps also reflecting the eclogitic paragenesis of many Premier diamonds. The peridotites provide evidence for the nature of the lithosphere beneath Premier prior to ∼ 1.15 Ga. Metasomatism of the peridotites is possibly linked to the Bushveld Igneous Event at ∼ 2 Ga, as well as to other magmatic events that affected the Kaapvaal craton from the Archean to the Mesoproterozoic. Premier peridotites do not suggest that the cratonic lithosphere beneath the region was completely replaced. Samples with Proterozoic T<sub>RD</sub> eruption model ages may represent Archean lithosphere that experienced alteration by metasoma
{"title":"A 187Re-187Os and highly siderophile element study of diamondiferous kimberlite melt-mantle interactions and the inferred age of continental lithosphere","authors":"Taryn Linzmeyer , James M.D. Day , Raquel Alonso-Perez , Theo Phahla , Anton Wolmarans , Andrew Rogers","doi":"10.1016/j.gca.2024.09.026","DOIUrl":"10.1016/j.gca.2024.09.026","url":null,"abstract":"<div><div>The ∼ 1.15-billion-year-old (Ga) Premier kimberlite pipe (Cullinan diamond mine), South Africa, is composed of several distinct kimberlite facies (Grey, Brown, Pale Piebald, Dark Piebald, Black Coherent [Type 3C], Blue/Brown Transitional, and Fawn). We report bulk rock Re-Os isotope data for Premier kimberlite facies, as well as for a suite of entrained peridotite and mafic xenoliths. These data are complemented by bulk rock highly siderophile element (HSE: Re, Pd, Pt, Ru, Ir, Os), major- and trace-element abundances. Measured <sup>187</sup>Os/<sup>188</sup>Os for the kimberlite facies range from 0.1223 to 0.1672 (γOs<sub>i</sub> of −2.5 to + 17.4), peridotite xenoliths range from 0.1096 to 0.1244 (γOs<sub>i</sub> of −13.3 to −1.1), and pyroxenite xenoliths range from 0.1796 to 0.938 (γOs<sub>i</sub> of + 27 to + 419). A single measured amphibolite xenolith has the most radiogenic measured <sup>187</sup>Os/<sup>188</sup>Os of 2.86 (γOs<sub>i</sub> of + 43). Harzburgite xenoliths yield time of rhenium depletion model ages (T<sub>RD</sub>) of ∼ 1.5 to 2.8 Ga, consistent with average T<sub>RD</sub> ages for Premier peridotites (2.4 ± 0.4 Ga). With these and published data, we considered the relationships between kimberlite and mantle xenoliths, compare estimates of relative peridotite incorporation to sampled diamond grade, and explore recratonization versus refertilization arguments with regards to T<sub>RD</sub> model ages. Kimberlite melt infiltration into Premier peridotite xenoliths is evident from melt veins accounting for ∼ 2 and ∼ 14 modal % of samples, and has led to incompatible element enrichment, including elevated Re. In turn, kimberlites show geochemical evidence for addition of peridotite xenolith fragments, with Type 3C having > 30 % more peridotite contribution than the Brown volcaniclastic facies. Kimberlites and peridotites plot on a <sup>187</sup>Re/<sup>188</sup>Os versus <sup>187</sup>Os/<sup>188</sup>Os mixing line (R<sup>2</sup> = 0.92), with kimberlites having older apparent ages than the true age of crystallization. This mixing line provides estimates of lithospheric incorporation into the kimberlites, where the units with higher peridotite incorporation do not correlate with diamond grade. This is likely due to lithological and post-emplacement alteration heterogeneity within the kimberlite units, perhaps also reflecting the eclogitic paragenesis of many Premier diamonds. The peridotites provide evidence for the nature of the lithosphere beneath Premier prior to ∼ 1.15 Ga. Metasomatism of the peridotites is possibly linked to the Bushveld Igneous Event at ∼ 2 Ga, as well as to other magmatic events that affected the Kaapvaal craton from the Archean to the Mesoproterozoic. Premier peridotites do not suggest that the cratonic lithosphere beneath the region was completely replaced. Samples with Proterozoic T<sub>RD</sub> eruption model ages may represent Archean lithosphere that experienced alteration by metasoma","PeriodicalId":327,"journal":{"name":"Geochimica et Cosmochimica Acta","volume":"386 ","pages":"Pages 157-172"},"PeriodicalIF":4.5,"publicationDate":"2024-09-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142662976","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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