Geochimica et Cosmochimica Acta最新文献

{"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}

{"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}

{"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}

{"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}

{"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}

{"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}

{"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 &lt; 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}

{"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}

{"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}

{"title":"Molecular H2 in silicate melts","authors":"Dionysis I. Foustoukos","doi":"10.1016/j.gca.2024.10.020","DOIUrl":"https://doi.org/10.1016/j.gca.2024.10.020","url":null,"abstract":"A series of hydrothermal diamond anvil cell experiments was conducted to constrain the equilibrium distribution of molecular H<ce:inf loc=\"post\">2</ce:inf> between H<ce:inf loc=\"post\">2</ce:inf>O-saturated sodium aluminosilicate melts and H<ce:inf loc=\"post\">2</ce:inf>O at elevated temperatures (600–800 °C) and pressures (317–1265 MPa). The distribution of H<ce:inf loc=\"post\">2</ce:inf> between the silicate liquid and the aqueous fluid was achieved through real-time monitoring of the H-H stretching vibration under in situ conditions using Raman vibrational spectroscopy. Results show that the solubility of H<ce:inf loc=\"post\">2</ce:inf> in silicate melts saturated with H<ce:inf loc=\"post\">2</ce:inf>O decreases as the temperature increases, with control exerted by the mole fraction of H<ce:inf loc=\"post\">2</ce:inf>O in the melt. The dissolution of H<ce:inf loc=\"post\">2</ce:inf> in the hydrous silicate melts appears to follow Henrian behavior, resembling that of an inert, neutral non-polar species. To express species solubility as a function of temperature (T in K) an empirical equation was developed:","PeriodicalId":327,"journal":{"name":"Geochimica et Cosmochimica Acta","volume":"257 1","pages":""},"PeriodicalIF":5.0,"publicationDate":"2024-10-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142718839","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}