Geochimica et Cosmochimica Acta最新文献

{"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 &gt; 2-aminoisobutyric acid &gt; γ-aminobutyric acid &gt; glycine &gt; α-alanine &gt; 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}

{"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}

{"title":"Triple oxygen isotope variability of precipitation in a tropical mountainous region","authors":"L. Nicole Arellano ,&nbsp;Emily J. Beverly ,&nbsp;Ny Riavo G. Voarintsoa ,&nbsp;Christopher B. Skinner ,&nbsp;Andrew J. Schauer ,&nbsp;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, 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.</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}

{"title":"Metabolic imprints in the hydrogen isotopes of Archaeoglobus fulgidus tetraether lipids","authors":"Jeemin H. Rhim ,&nbsp;Sebastian Kopf ,&nbsp;Jamie McFarlin ,&nbsp;Ashley E. Maloney ,&nbsp;Harpreet Batther ,&nbsp;Carolynn M. Harris ,&nbsp;Alice Zhou ,&nbsp;Xiahong Feng ,&nbsp;Yuki Weber ,&nbsp;Shelley Hoeft-McCann ,&nbsp;Ann Pearson ,&nbsp;William D. Leavitt","doi":"10.1016/j.gca.2024.09.032","DOIUrl":"10.1016/j.gca.2024.09.032","url":null,"abstract":"&lt;div&gt;&lt;div&gt;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 &lt;em&gt;n&lt;/em&gt;-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 &lt;em&gt;Archaeoglobus fulgidus&lt;/em&gt; 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 &lt;sup&gt;2&lt;/sup&gt;H/&lt;sup&gt;1&lt;/sup&gt;H fractionation between lipids and water (ε&lt;sub&gt;L/W&lt;/sub&gt;) was overall negative. Both carbon metabolism and growth phase affected the magnitude of isotope fractionation in &lt;em&gt;A. fulgidus&lt;/em&gt;; however, the changes in ε&lt;sub&gt;L/W&lt;/sub&gt; 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 &lt;em&gt;A. fulgidus&lt;/em&gt; cultures directly reflect water isotope compositions (i.e., not via organic substrate or H&lt;sub&gt;2&lt;/sub&gt;) during autotrophy and heterotrophy, respectively. The model results also suggest two main mechanisms of consistent &lt;sup&gt;2&lt;/sup&gt;H depletion observed in &lt;em&gt;A. fulgidus&lt;/em&gt; tetraethers as well as other archaeal lipids reported in previous studies: 1) isotopic re-equilibration via upstream isomerization reactions involving C&lt;sub&gt;5&lt;/sub&gt; 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&lt;sub&gt;L/W&lt;/sub&gt; 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 &lt;sup&gt;2&lt;/sup&gt;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&lt;sub&gt;L/W&lt;/sub&gt; 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}

{"title":"Antimony stable isotope fractionation during adsorption onto birnessite: A molecular perspective from X-ray absorption spectroscopy and density functional theory","authors":"Ziyi Zhou ,&nbsp;Guangyi Sun ,&nbsp;Weiqing Zhou ,&nbsp;Jianwei Zhou ,&nbsp;Xinbin Feng ,&nbsp;Y. Zou Finfrock ,&nbsp;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 Δ¹²³Sb_{adsorbed-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.</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}

{"title":"Surface complexation of rare earth elements on goethite in sea-floor hydrothermal environment: Insight from first principles simulations","authors":"Yingchun Zhang,&nbsp;Xiandong Liu,&nbsp;Xiancai Lu,&nbsp;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_a’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 <img>FeOH sites on goethite (1<!--> <!-->1<!--> <!-->0) surface and tridentate complexes on two neighboring <img>FeOH sites plus one <img>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.</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}

{"title":"Rhenium-platinum group elements reveal seawater incursion induced massive lacustrine organic carbon burial","authors":"Zheng Qin ,&nbsp;Jingao Liu ,&nbsp;Huan Cui ,&nbsp;Kurt O. Konhauser ,&nbsp;He Huang ,&nbsp;Dongtao Xu ,&nbsp;Yuan Gao ,&nbsp;Huaichun Wu ,&nbsp;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}

{"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 ,&nbsp;James M.D. Day ,&nbsp;Raquel Alonso-Perez ,&nbsp;Theo Phahla ,&nbsp;Anton Wolmarans ,&nbsp;Andrew Rogers","doi":"10.1016/j.gca.2024.09.026","DOIUrl":"10.1016/j.gca.2024.09.026","url":null,"abstract":"&lt;div&gt;&lt;div&gt;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 &lt;sup&gt;187&lt;/sup&gt;Os/&lt;sup&gt;188&lt;/sup&gt;Os for the kimberlite facies range from 0.1223 to 0.1672 (γOs&lt;sub&gt;i&lt;/sub&gt; of −2.5 to + 17.4), peridotite xenoliths range from 0.1096 to 0.1244 (γOs&lt;sub&gt;i&lt;/sub&gt; of −13.3 to −1.1), and pyroxenite xenoliths range from 0.1796 to 0.938 (γOs&lt;sub&gt;i&lt;/sub&gt; of + 27 to + 419). A single measured amphibolite xenolith has the most radiogenic measured &lt;sup&gt;187&lt;/sup&gt;Os/&lt;sup&gt;188&lt;/sup&gt;Os of 2.86 (γOs&lt;sub&gt;i&lt;/sub&gt; of + 43). Harzburgite xenoliths yield time of rhenium depletion model ages (T&lt;sub&gt;RD&lt;/sub&gt;) of ∼ 1.5 to 2.8 Ga, consistent with average T&lt;sub&gt;RD&lt;/sub&gt; 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&lt;sub&gt;RD&lt;/sub&gt; 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 &gt; 30 % more peridotite contribution than the Brown volcaniclastic facies. Kimberlites and peridotites plot on a &lt;sup&gt;187&lt;/sup&gt;Re/&lt;sup&gt;188&lt;/sup&gt;Os versus &lt;sup&gt;187&lt;/sup&gt;Os/&lt;sup&gt;188&lt;/sup&gt;Os mixing line (R&lt;sup&gt;2&lt;/sup&gt; = 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&lt;sub&gt;RD&lt;/sub&gt; 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}

{"title":"On the origin and evolution of deuterium enrichment in type 1 and 2 chondritic organic solids","authors":"George D. Cody ,&nbsp;Conel M. O’D. Alexander ,&nbsp;Dionysis I. Foustoukos ,&nbsp;Yoko Kebukawa ,&nbsp;Ying Wang","doi":"10.1016/j.gca.2024.09.023","DOIUrl":"10.1016/j.gca.2024.09.023","url":null,"abstract":"<div><div>Rotationally resonant Deuterium Nuclear Magnetic Resonance spectroscopy (D MAS NMR) was applied to IOM isolated from a CR1 chondrite Grosvenor Mountains (GRO) 95577 and a CM2 chondrite (Murchison). It is shown that in IOM D strongly prefers the aliphatic hydrogen reservoir over the aromatic hydrogen reservoir. For GRO 95577, that has a bulk δD of 3303 ‰ (Alexander et al., 2010), the average δD value of the aromatic reservoir is 1740 ± 128 ‰ and the aliphatic reservoir is 4477 ± 105 ‰, i.e., D/H enrichments of 1.27 and 0.64, respectively, relative to the bulk. For Murchison IOM, that has a bulk δD of 811 ‰ (Alexander et al., 2010), the average δD of the aromatic reservoir is 512 ± 88 ‰ and the aliphatic reservoir is 1033 ± 64 ‰ i.e., D/H enrichments of 1.12 and 0.82, respectively, relative to the bulk. D-H exchange between D-enriched water and a type III kerogen reveals nearly equivalent D up take by both aromatics and aliphatics. Laboratory synthesis of IOM-like material in the presence of D₂O reveals a high degree of deuteration with a strong preferential deuteration of the aliphatic hydrogen reservoir indicating that the δD of the water during IOM synthesis is the primary determinant of syn-IOM’s δD. The IOM in GRO 95577 and Murchison (FA and H/C × 100) lie on the molecular evolution line as defined by the IOM of the Tagish Lake clasts and Murchison IOM has experienced more molecular evolution relative to that exhibited by GRO 95577 IOM. A forward prediction derived from the D/H ratios for the aliphatic and aromatic hydrogen reservoirs in Murchison and GRO 95577, relative to their bulk D/H ratios, derived from D MAS NMR, is applied to explain the origin of the Tagish Lake trend of δD vs molecular evolution (H/C × 100). The results of this forward prediction suggest that the Tagish Lake isotopic trend results from a combination of molecular evolution (loss of predominantly aliphatic H and D) and partial D-H exchange with D depleted chondritic water during a short-term hydrothermal alteration event. Such events may be faithfully identified in chondritic organic solids and be a common occurrence, but not necessarily revealed in the mineralogy of type 1 and 2 carbonaceous chondrites.</div></div>","PeriodicalId":327,"journal":{"name":"Geochimica et Cosmochimica Acta","volume":"386 ","pages":"Pages 139-156"},"PeriodicalIF":4.5,"publicationDate":"2024-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142662970","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":"Improved solid-state 13C and 15N NMR reveals fundamental compositional divide between refractory dissolved organic carbon and nitrogen in the sea","authors":"H.L. Ianiri ,&nbsp;H.E. Mason ,&nbsp;T.A.B. Broek ,&nbsp;M.D. McCarthy","doi":"10.1016/j.gca.2024.09.022","DOIUrl":"10.1016/j.gca.2024.09.022","url":null,"abstract":"<div><div>Marine dissolved organic matter (DOM) is one of the largest reservoirs of organic carbon and nitrogen in the world. Yet, despite its global importance, most DOM remains molecularly uncharacterized. Solid-state nuclear magnetic resonance (NMR) spectroscopy of isolated DOM fractions represents one of the most powerful techniques to understand overall structural composition. However, it is well known that standard cross polarization magic angle spinning (CP/MAS) NMR, the technique used for almost all past solid-state NMR studies of DOM, is at best “semi-quantitative,” and underestimates fully substituted NMR active nuclei. Additionally, almost all past solid-state NMR work analyzed high molecular weight (HMW) material isolated by ultrafiltration, which is now understood to represent mostly ¹⁴C-young, “semi-labile” compounds. In contrast, there is far less information regarding the composition of older, low molecular weight (LMW) DOM, which represents the vast majority of the ocean’s accumulated refractory DOM pool.</div><div>Here, we applied ¹³C and ¹⁵N solid-state multiCP/MAS NMR, improved NMR methods optimized to more quantitatively resolve fully substituted NMR nuclei, to both HMW and LMW DOM isolated from the surface and deep North Pacific Subtropical Gyre. These methods confirm past work indicating most nitrogen containing HMW DOM as amide compounds, but also demonstrate a modest heterocyclic N component not previously identified. In contrast, we found that LMW DON is almost entirely aromatic heterocyclic N, consistent with the hypothesis that heterocyclic N structures may be largely responsible for the accumulation of the ocean’s refractory DON pool. Surprisingly, however, we find DOC aromatic functionalities still represent only a very minor portion of either the HMW or the LMW refractory carbon pools, in marked contrast to refractory DON composition. Together, these more quantitative solid-state NMR techniques likely represent the most accurate picture of DON and DOC functional and compound-class makeup to date, and so have broad implications for our understanding of marine DOM structure and cycling. Specifically, our new data suggests that while chemical composition likely acts as a key control on DOM lability, the most refractory components of DOC and DON have very different compositions, sources, and cycling, supporting the idea that DOC and DON cycling in the ocean may be largely decoupled.</div></div>","PeriodicalId":327,"journal":{"name":"Geochimica et Cosmochimica Acta","volume":"384 ","pages":"Pages 155-167"},"PeriodicalIF":4.5,"publicationDate":"2024-09-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142319754","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}