Pub Date : 2024-11-01DOI: 10.1016/j.gca.2024.10.029
Timothy W. Lyons
{"title":"Citation for the 2024 Goldschmidt to Donald E. Canfield","authors":"Timothy W. Lyons","doi":"10.1016/j.gca.2024.10.029","DOIUrl":"https://doi.org/10.1016/j.gca.2024.10.029","url":null,"abstract":"","PeriodicalId":327,"journal":{"name":"Geochimica et Cosmochimica Acta","volume":"18 1","pages":""},"PeriodicalIF":5.0,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142673570","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 : 2024-11-01DOI: 10.1016/j.gca.2024.10.033
Rodney C. Ewing
{"title":"Citation for the 2024C. C. Patterson Award to Satoshi Utsunomiya","authors":"Rodney C. Ewing","doi":"10.1016/j.gca.2024.10.033","DOIUrl":"https://doi.org/10.1016/j.gca.2024.10.033","url":null,"abstract":"","PeriodicalId":327,"journal":{"name":"Geochimica et Cosmochimica Acta","volume":"149 1","pages":""},"PeriodicalIF":5.0,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142673616","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 : 2024-11-01DOI: 10.1016/j.gca.2024.10.032
Jihua Hao
{"title":"Acceptance for the 2024 F.W. Clarke Award to Jihua Hao","authors":"Jihua Hao","doi":"10.1016/j.gca.2024.10.032","DOIUrl":"https://doi.org/10.1016/j.gca.2024.10.032","url":null,"abstract":"","PeriodicalId":327,"journal":{"name":"Geochimica et Cosmochimica Acta","volume":"230 1","pages":""},"PeriodicalIF":5.0,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142673848","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 : 2024-11-01DOI: 10.1016/j.gca.2024.10.030
Donald E. Canfield
{"title":"Acceptance for the 2024 V.M. Goldschmidt Award to Donald E. Canfield","authors":"Donald E. Canfield","doi":"10.1016/j.gca.2024.10.030","DOIUrl":"https://doi.org/10.1016/j.gca.2024.10.030","url":null,"abstract":"","PeriodicalId":327,"journal":{"name":"Geochimica et Cosmochimica Acta","volume":"18 1","pages":""},"PeriodicalIF":5.0,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142673648","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 : 2024-11-01DOI: 10.1016/j.gca.2024.10.034
Satoshi Utsunomiya
{"title":"Acceptance for the 2024 C. C. Patterson Award to Satoshi Utsunomiya","authors":"Satoshi Utsunomiya","doi":"10.1016/j.gca.2024.10.034","DOIUrl":"https://doi.org/10.1016/j.gca.2024.10.034","url":null,"abstract":"","PeriodicalId":327,"journal":{"name":"Geochimica et Cosmochimica Acta","volume":"8 1","pages":""},"PeriodicalIF":5.0,"publicationDate":"2024-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142673615","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}
Fifteen elements, including most of the major elements, were quantified using neutron-induced prompt gamma-ray analysis for five Antarctic carbonaceous chondrites with CI affinities and seven with CM affinities. Common among the twelve meteorites is the depletion of volatile elements H and chlorine, showing a positive correlation and being depleted compared to non-Antarctic CI levels. This depletion is not thought to have occurred after the fall on Antarctica, but to have been caused by thermal metamorphism on the parent body. Among the meteorites analyzed in this study, six meteorites (Y-86029, Y 980115 and Y-82162 (with CI affinities), and Y-86720, Y-86789 and B-7904 (with CM affinities)) have previously been proposed to constitute a new meteorite group, the Yamato-type (CY), based on their oxygen isotopic compositions and petrological features. The elemental compositional characteristics of the remaining six meteorites analyzed in this study, Y-86737 and Y 980134 (with CI affinities), and Y-86770, Y-86771, Y-86772 and Y-86773 (with CM affinities), suggest that these meteorites are all classified into the same chemical group CY. Based on the abundance of moderately volatile elements Mn and S, the twelve meteorites can be divided into two groups: one with levels similar to non-Antarctic CI and the other with intermediate levels between CI and CM. These results suggest that CY chondrites originate from two distinct parent bodies. To facilitate further discussions on CY chondrites, we propose naming the groups with compositions close to CI and CM as CYi and CYm, respectively.
利用中子诱导瞬时伽马射线分析，对五块具有 CI 亲缘关系的南极碳质陨石和七块具有 CM 亲缘关系的南极碳质陨石的十五种元素（包括大多数主要元素）进行了定量分析。这十二块陨石的共同点是挥发性元素 H 和氯的消耗，与非南极 CI 水平相比，这两种元素的消耗呈正相关。这种损耗被认为不是在陨落到南极洲之后发生的，而是由母体的热变质作用引起的。在这项研究分析的陨石中，有六块陨石（Y-86029、Y 980115 和 Y-82162（具有 CI 亲缘关系），以及 Y-86720、Y-86789 和 B-7904（具有 CM 亲缘关系））曾被根据它们的氧同位素组成和岩石学特征而提议构成一个新的陨石群--大和类型（CY）。本研究分析的其余六块陨石，即 Y-86737 和 Y 980134（具有 CI 亲缘关系），以及 Y-86770、Y-86771、Y-86772 和 Y-86773（具有 CM 亲缘关系）的元素组成特征表明，这些陨石都被归入同一化学组 CY。根据中等挥发性元素 Mn 和 S 的丰度，这 12 块陨石可分为两组：一组的含量与非南极 CI 相似，另一组的含量介于 CI 和 CM 之间。这些结果表明，CY 陨石起源于两个不同的母体。为了便于进一步讨论CY软玉，我们建议将成分接近CI和CM的组别分别命名为CYi和CYm。
{"title":"Chemical characteristics of the Yamato-type (CY) carbonaceous chondrites","authors":"Mitsuru Ebihara, Naoki Shirai, Takahito Osawa, Akira Yamaguchi","doi":"10.1016/j.gca.2024.10.026","DOIUrl":"https://doi.org/10.1016/j.gca.2024.10.026","url":null,"abstract":"Fifteen elements, including most of the major elements, were quantified using neutron-induced prompt gamma-ray analysis for five Antarctic carbonaceous chondrites with CI affinities and seven with CM affinities. Common among the twelve meteorites is the depletion of volatile elements H and chlorine, showing a positive correlation and being depleted compared to non-Antarctic CI levels. This depletion is not thought to have occurred after the fall on Antarctica, but to have been caused by thermal metamorphism on the parent body. Among the meteorites analyzed in this study, six meteorites (Y-86029, Y 980115 and Y-82162 (with CI affinities), and Y-86720, Y-86789 and B-7904 (with CM affinities)) have previously been proposed to constitute a new meteorite group, the Yamato-type (CY), based on their oxygen isotopic compositions and petrological features. The elemental compositional characteristics of the remaining six meteorites analyzed in this study, Y-86737 and Y 980134 (with CI affinities), and Y-86770, Y-86771, Y-86772 and Y-86773 (with CM affinities), suggest that these meteorites are all classified into the same chemical group CY. Based on the abundance of moderately volatile elements Mn and S, the twelve meteorites can be divided into two groups: one with levels similar to non-Antarctic CI and the other with intermediate levels between CI and CM. These results suggest that CY chondrites originate from two distinct parent bodies. To facilitate further discussions on CY chondrites, we propose naming the groups with compositions close to CI and CM as CYi and CYm, respectively.","PeriodicalId":327,"journal":{"name":"Geochimica et Cosmochimica Acta","volume":"251 1","pages":""},"PeriodicalIF":5.0,"publicationDate":"2024-10-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142673645","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 : 2024-10-28DOI: 10.1016/j.gca.2024.10.025
Kai Deng, Gregory F. de Souza, Jianghui Du
Beryllium isotopes (stable <ce:sup loc="post">9</ce:sup>Be and cosmogenic meteoric <ce:sup loc="post">10</ce:sup>Be) enter the oceans through distinct pathways – i.e., from the continents and the atmosphere respectively – and display non-conservative behaviour in seawater. This isotope system has served as a powerful tool for quantifying a variety of processes, including geomagnetism, sedimentation, continental input, and ocean circulation. However, processes at land–ocean boundaries and within the ocean interior may either amplify or buffer the seawater isotope response to environmental changes. In the last decade, substantial effort has been invested in understanding external sources and internal cycling of Be isotopes, offering an excellent opportunity to revisit their modern oceanic cycle. Here, we investigate the controls on the modern oceanic cycling of Be isotopes using a three-dimensional ocean model, constrained by observational data on input fluxes and water-column distributions of <ce:sup loc="post">9</ce:sup>Be and <ce:sup loc="post">10</ce:sup>Be. In addition to modelling the previously known controls, we highlight the key role of marine benthic fluxes and scavenging onto particulate organic matter and opal in determining the mass balance and spatial distribution of Be isotopes. Inter-basin Be transport by the circulation is less important than external inputs at continent/atmosphere–ocean boundaries, except in the South Pacific. Therefore, the distribution of seawater <ce:sup loc="post">10</ce:sup>Be/<ce:sup loc="post">9</ce:sup>Be ratios largely reflects that of the external inputs in most basins in the modern ocean. Finally, we apply our data-constrained mechanistic model to test the sensitivity of basin-wide <ce:sup loc="post">10</ce:sup>Be/<ce:sup loc="post">9</ce:sup>Be ratios to changes of external sources and internal cycling. This analysis shows that seawater <ce:sup loc="post">10</ce:sup>Be/<ce:sup loc="post">9</ce:sup>Be ratios are to some extent buffered against changes in continental denudation. For example, a 50 % decrease in denudation rates results in a 13–48 % increase in ocean-wide <ce:sup loc="post">10</ce:sup>Be/<ce:sup loc="post">9</ce:sup>Be ratios. Moreover, the interplay between particle scavenging and ocean circulation can cause divergent responses in <ce:sup loc="post">10</ce:sup>Be/<ce:sup loc="post">9</ce:sup>Be ratios in different basins. Weaker scavenging (e.g., 50 % decrease in intensity) would increase the homogenising effect of ocean circulation, making North Atlantic and North Pacific <ce:sup loc="post">10</ce:sup>Be/<ce:sup loc="post">9</ce:sup>Be ratios converge (∼20 % change in isotope ratios). The mechanistic understanding developed from this Be cycling model provides important insights into the various applications of marine Be isotopes, and offers additional tools to assess the causes of spatio-temporal Be isotope variations. We also identify the key oceanic processes that require further const
铍同位素（稳定铍 9Be 和宇宙陨变铍 10Be）通过不同的途径进入海洋，即分别从大陆和大气中进入，并在海水中表现出非保守行为。这一同位素系统是量化地磁、沉积、大陆输入和海洋环流等各种过程的有力工具。然而，陆地-海洋边界和海洋内部的过程可能会放大或缓冲海水同位素对环境变化的反应。在过去十年中，人们投入了大量精力来了解 Be 同位素的外部来源和内部循环，这为重新审视其现代海洋循环提供了绝佳机会。在此，我们利用一个三维海洋模型，在 9Be 和 10Be 输入通量和水柱分布观测数据的约束下，研究了 Be 同位素现代海洋循环的控制因素。除了模拟以前已知的控制因素外，我们还强调了海洋底栖通量以及颗粒有机物和蛋白石的清扫在决定 Be 同位素的质量平衡和空间分布方面的关键作用。除南太平洋外，在大陆/大气-海洋边界，环流造成的盆地间 Be 迁移不如外部输入重要。因此，海水 10Be/9Be 比率的分布在很大程度上反映了现代海洋中大多数盆地的外部输入。最后，我们应用数据约束机理模型检验了全海盆 10Be/9Be 比率对外部来源和内部循环变化的敏感性。分析表明，海水 10Be/9Be 比率在一定程度上可以缓冲大陆剥蚀的变化。例如，剥蚀率降低 50%，整个海洋的 10Be/9Be 比率就会增加 13-48%。此外，粒子清除和大洋环流之间的相互作用会导致不同海盆中 10Be/9Be 比率的不同反应。较弱的粒子清除（例如强度下降 50%）会增加海洋环流的同质化效应，使北大西洋和北太平洋的 10Be/9Be 比率趋同（同位素比率变化 ∼ 20%）。从这一 Be 循环模型中获得的机理认识为海洋 Be 同位素的各种应用提供了重要启示，并为评估 Be 同位素时空变化的原因提供了更多工具。我们还确定了需要进一步制约的关键海洋过程，以便全面了解 Be 在现代海洋中的循环情况和时间回溯。
{"title":"Modern oceanic cycle of beryllium isotopes assessed using a data-constrained biogeochemical model","authors":"Kai Deng, Gregory F. de Souza, Jianghui Du","doi":"10.1016/j.gca.2024.10.025","DOIUrl":"https://doi.org/10.1016/j.gca.2024.10.025","url":null,"abstract":"Beryllium isotopes (stable <ce:sup loc=\"post\">9</ce:sup>Be and cosmogenic meteoric <ce:sup loc=\"post\">10</ce:sup>Be) enter the oceans through distinct pathways – i.e., from the continents and the atmosphere respectively – and display non-conservative behaviour in seawater. This isotope system has served as a powerful tool for quantifying a variety of processes, including geomagnetism, sedimentation, continental input, and ocean circulation. However, processes at land–ocean boundaries and within the ocean interior may either amplify or buffer the seawater isotope response to environmental changes. In the last decade, substantial effort has been invested in understanding external sources and internal cycling of Be isotopes, offering an excellent opportunity to revisit their modern oceanic cycle. Here, we investigate the controls on the modern oceanic cycling of Be isotopes using a three-dimensional ocean model, constrained by observational data on input fluxes and water-column distributions of <ce:sup loc=\"post\">9</ce:sup>Be and <ce:sup loc=\"post\">10</ce:sup>Be. In addition to modelling the previously known controls, we highlight the key role of marine benthic fluxes and scavenging onto particulate organic matter and opal in determining the mass balance and spatial distribution of Be isotopes. Inter-basin Be transport by the circulation is less important than external inputs at continent/atmosphere–ocean boundaries, except in the South Pacific. Therefore, the distribution of seawater <ce:sup loc=\"post\">10</ce:sup>Be/<ce:sup loc=\"post\">9</ce:sup>Be ratios largely reflects that of the external inputs in most basins in the modern ocean. Finally, we apply our data-constrained mechanistic model to test the sensitivity of basin-wide <ce:sup loc=\"post\">10</ce:sup>Be/<ce:sup loc=\"post\">9</ce:sup>Be ratios to changes of external sources and internal cycling. This analysis shows that seawater <ce:sup loc=\"post\">10</ce:sup>Be/<ce:sup loc=\"post\">9</ce:sup>Be ratios are to some extent buffered against changes in continental denudation. For example, a 50 % decrease in denudation rates results in a 13–48 % increase in ocean-wide <ce:sup loc=\"post\">10</ce:sup>Be/<ce:sup loc=\"post\">9</ce:sup>Be ratios. Moreover, the interplay between particle scavenging and ocean circulation can cause divergent responses in <ce:sup loc=\"post\">10</ce:sup>Be/<ce:sup loc=\"post\">9</ce:sup>Be ratios in different basins. Weaker scavenging (e.g., 50 % decrease in intensity) would increase the homogenising effect of ocean circulation, making North Atlantic and North Pacific <ce:sup loc=\"post\">10</ce:sup>Be/<ce:sup loc=\"post\">9</ce:sup>Be ratios converge (∼20 % change in isotope ratios). The mechanistic understanding developed from this Be cycling model provides important insights into the various applications of marine Be isotopes, and offers additional tools to assess the causes of spatio-temporal Be isotope variations. We also identify the key oceanic processes that require further const","PeriodicalId":327,"journal":{"name":"Geochimica et Cosmochimica Acta","volume":"6 1","pages":""},"PeriodicalIF":5.0,"publicationDate":"2024-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142673646","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 : 2024-10-28DOI: 10.1016/j.gca.2024.10.021
Dorrit E. Jacob, Richard A. Stern, Janina Czas, Magnus Reutter, Sandra Piazolo, Thomas Stachel
Polycrystalline diamond aggregates (PDAs) are small rocks composed mostly of diamond grains, but often containing also peridotitic, eclogitic and/or websteritic minerals as accessory phases. PDAs are formed rapidly in Earth’s mantle, and the diamonds preserve heterogeneity not often seen in monocrystalline diamond. Here, diamond grains from forty-three PDAs from the Venetia diamond mine (RSA) with grain-sizes < 1 mm are presented. They have heterogeneous and complex cathodoluminescence signatures that are best explained by multiple, separate diamond growth episodes from compositionally distinct COH fluids/melts. The diamonds show a large range of nitrogen concentrations (0.5 to 2,891 at. ppm), δ15N (−4.3 to + 16.8 ‰) and δ13C values (−27.8 to −7.6 ‰). The positive δ15N median of + 6.4 ‰ and negative δ13C median of −21.2 ‰ indicate derivation of the diamond-forming fluid from organic materials in subducted oceanic crust and lithosphere. Two PDAs have δ13C and δ15N values typical for Earth’s mantle. Thirty-three PDAs contain websteritic garnets, or peridotitic garnets and clinopyroxenes and/or micas. Unradiogenic εNdi values in the garnets (−15.9 to −29.7) and clinopyroxene (−8.3) and δ18O values of 6.49 to 8.09 ‰ in websteritic garnets are consistent with an origin from subducted altered oceanic crust and support the findings from N and C systematics in the diamonds. Nitrogen aggregation data for the diamonds range from 25 % to 100 %B and vary by as much as 60 % within some individual PDAs. We explain the geochemical and isotopic heterogeneity of diamonds and silicates as well as the complex cathodoluminescence features with a model of episodic melt/fluid −rock interaction involving a reducing asthenospheric melt in the cratonic roots or the thermal boundary layer. We suggest that large volumes of PDA are formed in the cratonic roots and thermal boundary layer by this mechanism, making them an important reservoir for carbon storage, which is corroborated with their locally high abundance (ca. 20 %) in some kimberlites.
{"title":"Polycrystalline diamond aggregates and their role in Earth’s deep carbon cycle","authors":"Dorrit E. Jacob, Richard A. Stern, Janina Czas, Magnus Reutter, Sandra Piazolo, Thomas Stachel","doi":"10.1016/j.gca.2024.10.021","DOIUrl":"https://doi.org/10.1016/j.gca.2024.10.021","url":null,"abstract":"Polycrystalline diamond aggregates (PDAs) are small rocks composed mostly of diamond grains, but often containing also peridotitic, eclogitic and/or websteritic minerals as accessory phases. PDAs are formed rapidly in Earth’s mantle, and the diamonds preserve heterogeneity not often seen in monocrystalline diamond. Here, diamond grains from forty-three PDAs from the Venetia diamond mine (RSA) with grain-sizes < 1 mm are presented. They have heterogeneous and complex cathodoluminescence signatures that are best explained by multiple, separate diamond growth episodes from compositionally distinct COH fluids/melts. The diamonds show a large range of nitrogen concentrations (0.5 to 2,891 at. ppm), δ<ce:sup loc=\"post\">15</ce:sup>N (−4.3 to + 16.8 ‰) and δ<ce:sup loc=\"post\">13</ce:sup>C values (−27.8 to −7.6 ‰). The positive δ<ce:sup loc=\"post\">15</ce:sup>N median of + 6.4 ‰ and negative δ<ce:sup loc=\"post\">13</ce:sup>C median of −21.2 ‰ indicate derivation of the diamond-forming fluid from organic materials in subducted oceanic crust and lithosphere. Two PDAs have δ<ce:sup loc=\"post\">13</ce:sup>C and δ<ce:sup loc=\"post\">15</ce:sup>N values typical for Earth’s mantle. Thirty-three PDAs contain websteritic garnets, or peridotitic garnets and clinopyroxenes and/or micas. Unradiogenic εNd<ce:inf loc=\"post\">i</ce:inf> values in the garnets (−15.9 to −29.7) and clinopyroxene (−8.3) and δ<ce:sup loc=\"post\">18</ce:sup>O values of 6.49 to 8.09 ‰ in websteritic garnets are consistent with an origin from subducted altered oceanic crust and support the findings from N and C systematics in the diamonds. Nitrogen aggregation data for the diamonds range from 25 % to 100 %B and vary by as much as 60 % within some individual PDAs. We explain the geochemical and isotopic heterogeneity of diamonds and silicates as well as the complex cathodoluminescence features with a model of episodic melt/fluid −rock interaction involving a reducing asthenospheric melt in the cratonic roots or the thermal boundary layer. We suggest that large volumes of PDA are formed in the cratonic roots and thermal boundary layer by this mechanism, making them an important reservoir for carbon storage, which is corroborated with their locally high abundance (ca. 20 %) in some kimberlites.","PeriodicalId":327,"journal":{"name":"Geochimica et Cosmochimica Acta","volume":"39 1","pages":""},"PeriodicalIF":5.0,"publicationDate":"2024-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142673647","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 : 2024-10-28DOI: 10.1016/j.gca.2024.10.022
Andri Stefánsson, Samuel W. Scott, Anna B. Bjarkadóttir, Adolph Jr. Manadao Bravo, Sigríður M. Aðalsteinsdóttir, Erlend Straume, Kono H. Lemke
Silica solubility and molecular speciation in hydrothermal water vapor have been determined through quartz solubility experiments at 400–800 °C and 50–270 bar using a novel U-tube flow-through reactor system and theoretical calculations. The results demonstrate that silica concentrations are low in water vapor (mSi,tot = 0.11–4.56 mmol/kg or xSi,tot = 8.21 × 10−5–1.98 × 10−6 mol/mol) increase with both temperature and pressure, which is attributed to the dissolution of quartz according to the reaction:
在 400-800 °C 和 50-270 bar 温度条件下，利用新型 U 形管流过式反应器系统和理论计算，通过石英溶解度实验确定了热液水蒸汽中二氧化硅的溶解度和分子分级。结果表明，水蒸气中的二氧化硅浓度较低（mSi,tot = 0.11-4.56 mmol/kg 或 xSi,tot = 8.21 × 10-5-1.98 × 10-6 mol/mol），随着温度和压力的升高而增加，这归因于反应过程中石英的溶解：
{"title":"Silica solubility and molecular speciation in water vapor at 400–800 °C","authors":"Andri Stefánsson, Samuel W. Scott, Anna B. Bjarkadóttir, Adolph Jr. Manadao Bravo, Sigríður M. Aðalsteinsdóttir, Erlend Straume, Kono H. Lemke","doi":"10.1016/j.gca.2024.10.022","DOIUrl":"https://doi.org/10.1016/j.gca.2024.10.022","url":null,"abstract":"Silica solubility and molecular speciation in hydrothermal water vapor have been determined through quartz solubility experiments at 400–800 °C and 50–270 bar using a novel U-tube flow-through reactor system and theoretical calculations. The results demonstrate that silica concentrations are low in water vapor (<ce:italic>m</ce:italic><ce:inf loc=\"post\">Si,tot</ce:inf> = 0.11–4.56 mmol/kg or <ce:italic>x</ce:italic><ce:inf loc=\"post\">Si,tot</ce:inf> = 8.21 × 10<ce:sup loc=\"post\">−5</ce:sup>–1.98 × 10<ce:sup loc=\"post\">−6</ce:sup> mol/mol) increase with both temperature and pressure, which is attributed to the dissolution of quartz according to the reaction:","PeriodicalId":327,"journal":{"name":"Geochimica et Cosmochimica Acta","volume":"177 1","pages":""},"PeriodicalIF":5.0,"publicationDate":"2024-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142673651","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 : 2024-10-26DOI: 10.1016/j.gca.2024.10.023
Lucien Nana Yobo, Helen M. Williams, Alan D. Brandon, Chris Holmden, Kimberly V. Lau, Steven C. Bergman, James S. Eldrett, Daniel Minisini
Anomalously high metal concentrations including iron enrichments are recorded in marine carbonates deposited during Ocean Anoxic Event 2 (OAE 2). These metal enrichments have been attributed to massive submarine eruptions during the formation of one or more large igneous provinces, the proposed trigger for OAE 2 (hydrothermal hypothesis), or to the release of metals from the reoxidation of formerly anoxic marine sediment during a period of temporary cooling during OAE 2 (sediment release hypothesis). Here we use iron stable isotopes to help distinguish between the two hypotheses for a trace metal enriched interval during OAE 2 in the Iona-1 core in the Western Interior Seaway, Texas. Our results show a two-step negative excursion during OAE 2 that is coincident with osmium isotope volcanic proxies measured in the same core, with peak negative values centered on a trace metal-enriched interval. After corrections for detrital and locally supplied iron to the study setting, the δ56Fe value of the remotely supplied iron is –0.28 ± 0.05 ‰, falling in the range of iron δ56Fe values observed in modern hydrothermal plumes (–0.1 to –0.5 ‰), thus supporting the hydrothermal hypothesis as the source of iron and other associated trace metals enriched in the study core during OAE 2. By contrast, the sediment release hypothesis predicts much lower δ56Fe values, between –1.0 ‰ to –3.3 ‰ predicted for benthic supplies of iron from anoxic marine sediment overlying re-oxygenated bottom waters. This study shows that combining iron with other proxies for environmental change, particularly submarine volcanism, can distinguish hydrothermally supplied iron from dust, rivers, and shelf sediment supplies of iron despite iron’s reputation for complicated cycling.
{"title":"Iron Isotopes reveal volcanogenic input during Oceanic Anoxic Event 2 (OAE 2 ∼ 94 Ma)","authors":"Lucien Nana Yobo, Helen M. Williams, Alan D. Brandon, Chris Holmden, Kimberly V. Lau, Steven C. Bergman, James S. Eldrett, Daniel Minisini","doi":"10.1016/j.gca.2024.10.023","DOIUrl":"https://doi.org/10.1016/j.gca.2024.10.023","url":null,"abstract":"Anomalously high metal concentrations including iron enrichments are recorded in marine carbonates deposited during Ocean Anoxic Event 2 (OAE 2). These metal enrichments have been attributed to massive submarine eruptions during the formation of one or more large igneous provinces, the proposed trigger for OAE 2 (hydrothermal hypothesis), or to the release of metals from the reoxidation of formerly anoxic marine sediment during a period of temporary cooling during OAE 2 (sediment release hypothesis). Here we use iron stable isotopes to help distinguish between the two hypotheses for a trace metal enriched interval during OAE 2 in the Iona-1 core in the Western Interior Seaway, Texas. Our results show a two-step negative excursion during OAE 2 that is coincident with osmium isotope volcanic proxies measured in the same core, with peak negative values centered on a trace metal-enriched interval. After corrections for detrital and locally supplied iron to the study setting, the δ<ce:sup loc=\"post\">56</ce:sup>Fe value of the remotely supplied iron is –0.28 ± 0.05 ‰, falling in the range of iron δ<ce:sup loc=\"post\">56</ce:sup>Fe values observed in modern hydrothermal plumes (–0.1 to –0.5 ‰), thus supporting the hydrothermal hypothesis as the source of iron and other associated trace metals enriched in the study core during OAE 2. By contrast, the sediment release hypothesis predicts much lower δ<ce:sup loc=\"post\">56</ce:sup>Fe values, between –1.0 ‰ to –3.3 ‰ predicted for benthic supplies of iron from anoxic marine sediment overlying re-oxygenated bottom waters. This study shows that combining iron with other proxies for environmental change, particularly submarine volcanism, can distinguish hydrothermally supplied iron from dust, rivers, and shelf sediment supplies of iron despite iron’s reputation for complicated cycling.","PeriodicalId":327,"journal":{"name":"Geochimica et Cosmochimica Acta","volume":"10 1","pages":""},"PeriodicalIF":5.0,"publicationDate":"2024-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142673649","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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