This study aims to uncover the evolving dynamics of element mobility in serpentinised ultramafic clasts within the Asùt Tesoru mud volcano in the Mariana forearc. By employing in situ analysis of trace elements and boron isotopes (δ11B), our findings document a progressive 11B depletion from lizardite- to antigorite-bearing serpentinites, accompanied by a reduction in the incompatible element inventory in some samples. This pattern aligns with either a chemical evolution linked to phase transitions along the slab interface of shallow forearc serpentinites dragged down to depth, or interaction with shallow vs. deep slab fluids. Our results support a scenario of complex fluid and mechanical mixing along the plate interface in the Mariana subduction system, with major implications for the B recycling in convergent margins.
本研究旨在揭示马里亚纳前弧区 Asùt Tesoru 泥质火山内蛇纹岩化超基性岩碎屑中元素流动的演变动态。通过对痕量元素和硼同位素（δ11B）的现场分析，我们的研究结果记录了从含蜥蜴石到含锑硼的蛇纹岩中 11B 的逐步消耗，同时在一些样品中不相容元素的库存也有所减少。这种模式与沿浅前弧蛇纹岩板块界面相变的化学演变相吻合，或者与浅板块流体和深板块流体的相互作用相吻合。我们的研究结果支持马里亚纳俯冲系统板块界面复杂的流体和机械混合情况，对汇聚边缘的 B 循环具有重要影响。
{"title":"Variable δ11B signatures reflect dynamic evolution of the Mariana serpentinite forearc","authors":"E. Cannaò, B. Debret","doi":"10.7185/geochemlet.2416","DOIUrl":"https://doi.org/10.7185/geochemlet.2416","url":null,"abstract":"This study aims to uncover the evolving dynamics of element mobility in serpentinised ultramafic clasts within the Asùt Tesoru mud volcano in the Mariana forearc. By employing <em>in situ</em> analysis of trace elements and boron isotopes (δ<sup>11</sup>B), our findings document a progressive <sup>11</sup>B depletion from lizardite- to antigorite-bearing serpentinites, accompanied by a reduction in the incompatible element inventory in some samples. This pattern aligns with either a chemical evolution linked to phase transitions along the slab interface of shallow forearc serpentinites dragged down to depth, or interaction with shallow <em>vs.</em> deep slab fluids. Our results support a scenario of complex fluid and mechanical mixing along the plate interface in the Mariana subduction system, with major implications for the B recycling in convergent margins.","PeriodicalId":12613,"journal":{"name":"Geochemical Perspectives Letters","volume":null,"pages":null},"PeriodicalIF":4.9,"publicationDate":"2024-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140835451","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}
P. Rochette, G. Di Vincenzo, J. Gattacceca, J.A. Barrat, B. Devouard, L. Folco, A. Musolino, Y. Quesnel
A new type of silica-rich glass has been discovered associated with the known impact glass strewn field of the Atacama Desert. Based on petrography, chemical composition and indistinguishable 40Ar/39Ar formation ages at circa 6.6 Ma, we infer that these two glasses were produced by the same impact event, which gave rise to two successive compositionally different melt batches in close succession. The first one is a silica-rich melt derived from a mixture of quartz sand and weathered magmatic rocks. It is reduced and devoid of extraterrestrial contamination. The second one, much more abundant and which corresponds to the normal glass, is oxidised, highly contaminated by the iron type impactor and derived from an underlying unweathered dacitic rock. This scheme sheds a new light on the first second of the interaction between the Earth surface and a large metallic asteroid.
{"title":"A two stage impact melting process in an impact glass strewn field from the Atacama Desert","authors":"P. Rochette, G. Di Vincenzo, J. Gattacceca, J.A. Barrat, B. Devouard, L. Folco, A. Musolino, Y. Quesnel","doi":"10.7185/geochemlet.2418","DOIUrl":"https://doi.org/10.7185/geochemlet.2418","url":null,"abstract":"A new type of silica-rich glass has been discovered associated with the known impact glass strewn field of the Atacama Desert. Based on petrography, chemical composition and indistinguishable <sup>40</sup>Ar/<sup>39</sup>Ar formation ages at <em>circa</em> 6.6 Ma, we infer that these two glasses were produced by the same impact event, which gave rise to two successive compositionally different melt batches in close succession. The first one is a silica-rich melt derived from a mixture of quartz sand and weathered magmatic rocks. It is reduced and devoid of extraterrestrial contamination. The second one, much more abundant and which corresponds to the normal glass, is oxidised, highly contaminated by the iron type impactor and derived from an underlying unweathered dacitic rock. This scheme sheds a new light on the first second of the interaction between the Earth surface and a large metallic asteroid.","PeriodicalId":12613,"journal":{"name":"Geochemical Perspectives Letters","volume":null,"pages":null},"PeriodicalIF":4.9,"publicationDate":"2024-05-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140835697","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}
A. Grengs, G. Ledesma, Y. Xiong, S. Katsev, S.W. Poulton, E.D. Swanner, C. Wittkop
Siderite (FeCO3) is often assumed to precipitate from dissimilatory reduction of Fe-(oxyhydr)oxides, but geochemical and mineralogical analyses from ferruginous (anoxic, Fe-rich) Canyon Lake, USA, suggest Fe-carbonate represents a direct early precipitate unrelated to substantial oxide burial. X-ray absorption near edge structure (XANES) spectroscopy of sediment trap materials and an anoxic sediment core indicated a mixture of Fe(II) and Fe(III) in water column particulates and ferruginous surface sediments, while all Mn phases were reduced. About 60 cm below the sediment–water interface, Fe-Mn carbonates were detected by X-ray diffraction and XANES, while Fe extended X-ray absorption fine structure (EXAFS) spectra were best fit with combinations of a biogenic Fe-oxyhydroxide (“Bio Fe”), greigite, and siderite. Sediment Fe speciation indicates a large pool of reduced Fe with a minor component of oxides. Although we found no evidence of significant carbonate phases above or below the 60 cm horizon, equilibrium modelling indicates siderite supersaturation throughout surface sediment porewater, with pH as the primary control on supersaturation. We conclude that delivery of wildfire ash to sediments increased pH, initiating siderite precipitation from ferruginous porewater.
菱铁矿（FeCO3）通常被认为是由铁（氧氢）氧化物的异纤还原沉淀而成，但对美国峡谷湖（缺氧、富含铁）进行的地球化学和矿物学分析表明，碳酸铁是一种与大量氧化物埋藏无关的早期直接沉淀物。对沉积物捕集材料和缺氧沉积物岩芯进行的 X 射线吸收近缘结构（XANES）光谱分析表明，水柱颗粒和铁锈质表层沉积物中含有铁（II）和铁（III）的混合物，而所有锰相均被还原。在沉积物-水界面下约 60 厘米处，通过 X 射线衍射和 XANES 检测到了铁锰碳酸盐，而铁的扩展 X 射线吸收精细结构（EXAFS）光谱与生物成因的铁氧氢氧化物（"生物铁"）、绿泥石和菱铁矿的组合最为匹配。沉积物中铁的种类表明，沉积物中含有大量还原铁和少量氧化物。虽然我们在 60 厘米地层上下没有发现明显的碳酸盐相，但平衡建模表明菱铁矿在整个表层沉积物孔隙水中处于过饱和状态，pH 值是过饱和的主要控制因素。我们的结论是，野火灰烬向沉积物的输送增加了 pH 值，启动了铁锈色孔隙水的菱铁矿沉淀。
{"title":"Direct precipitation of siderite in ferruginous environments","authors":"A. Grengs, G. Ledesma, Y. Xiong, S. Katsev, S.W. Poulton, E.D. Swanner, C. Wittkop","doi":"10.7185/geochemlet.2414","DOIUrl":"https://doi.org/10.7185/geochemlet.2414","url":null,"abstract":"Siderite (FeCO<sub>3</sub>) is often assumed to precipitate from dissimilatory reduction of Fe-(oxyhydr)oxides, but geochemical and mineralogical analyses from ferruginous (anoxic, Fe-rich) Canyon Lake, USA, suggest Fe-carbonate represents a direct early precipitate unrelated to substantial oxide burial. X-ray absorption near edge structure (XANES) spectroscopy of sediment trap materials and an anoxic sediment core indicated a mixture of Fe(II) and Fe(III) in water column particulates and ferruginous surface sediments, while all Mn phases were reduced. About 60 cm below the sediment–water interface, Fe-Mn carbonates were detected by X-ray diffraction and XANES, while Fe extended X-ray absorption fine structure (EXAFS) spectra were best fit with combinations of a biogenic Fe-oxyhydroxide (“Bio Fe”), greigite, and siderite. Sediment Fe speciation indicates a large pool of reduced Fe with a minor component of oxides. Although we found no evidence of significant carbonate phases above or below the 60 cm horizon, equilibrium modelling indicates siderite supersaturation throughout surface sediment porewater, with pH as the primary control on supersaturation. We conclude that delivery of wildfire ash to sediments increased pH, initiating siderite precipitation from ferruginous porewater.","PeriodicalId":12613,"journal":{"name":"Geochemical Perspectives Letters","volume":null,"pages":null},"PeriodicalIF":4.9,"publicationDate":"2024-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140835689","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}
T. Linke, E.H. Oelkers, S.C. Möckel, S.R. Gislason
The ability of engineered enhanced weathering to impact atmospheric CO2 has been challenging to demonstrate due to the many processes occurring in soils and the short time span of current projects. Here we report the carbon balance in an Icelandic Histic/Gleyic Andosol that has received large quantities of basaltic dust over 3300 years, providing opportunity to quantify the rates and long term consequences of enhanced weathering. The added basaltic dust has dissolved continuously since its deposition. The alkalinity of the soil waters is more than 10 times higher than in equivalent basalt dust-free soils. After accounting for oxidation and degassing when the soil waters are exposed to the atmosphere, the annual CO2 drawdown due to alkalinity generation is 0.17 t C ha−1 yr−1. This study validates the ability of fine grained mafic mineral addition to soils to attenuate increasing atmospheric CO2 by alkalinity export. Induced changes in soil organic carbon storage, however, likely dominate the net CO2 drawdown of enhanced weathering efforts.
{"title":"Direct evidence of CO2 drawdown through enhanced weathering in soils","authors":"T. Linke, E.H. Oelkers, S.C. Möckel, S.R. Gislason","doi":"10.7185/geochemlet.2415","DOIUrl":"https://doi.org/10.7185/geochemlet.2415","url":null,"abstract":"The ability of engineered enhanced weathering to impact atmospheric CO<sub>2</sub> has been challenging to demonstrate due to the many processes occurring in soils and the short time span of current projects. Here we report the carbon balance in an Icelandic Histic/Gleyic Andosol that has received large quantities of basaltic dust over 3300 years, providing opportunity to quantify the rates and long term consequences of enhanced weathering. The added basaltic dust has dissolved continuously since its deposition. The alkalinity of the soil waters is more than 10 times higher than in equivalent basalt dust-free soils. After accounting for oxidation and degassing when the soil waters are exposed to the atmosphere, the annual CO<sub>2</sub> drawdown due to alkalinity generation is 0.17 t C ha<sup>−1</sup> yr<sup>−1</sup>. This study validates the ability of fine grained mafic mineral addition to soils to attenuate increasing atmospheric CO<sub>2</sub> by alkalinity export. Induced changes in soil organic carbon storage, however, likely dominate the net CO<sub>2</sub> drawdown of enhanced weathering efforts.","PeriodicalId":12613,"journal":{"name":"Geochemical Perspectives Letters","volume":null,"pages":null},"PeriodicalIF":4.9,"publicationDate":"2024-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140835757","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}
Xenon (Xe) behaviour in petrological processes, albeit essential to constrain mantle ingassing and degassing models, is elusive due to its volatile nature, and lack of direct investigation at the pressures (P) and temperatures (T) relevant to magma formation and crystallisation at depth. Xenon stands out amongst noble gases due to its unique reactivity with silicates of the lower crust and upper mantle, which could at least partially explain that published mineral/melt partitioning coefficients span up to six orders of magnitude. We report partition coefficients of Xe using in situ X-ray fluorescence at high P and T, and mass spectrometry analyses. Xenon is found to be moderately incompatible in anorthite-clinopyroxene mix in equilibrium with basalt (partition coefficient value of 0.16 ± 0.06), and compatible in olivine in equilibrium with basalt (partition coefficients in the range 88 ± 22 to 302 ± 46). While Xe is, thus, concentrated in basaltic melts coexisting with crystallising pyroxenes and feldspars, it is strongly retained in olivine at depth. Consequently, Xe originally contained in solid Earth has been preferentially retained at depth throughout Earth’s history, from the magma ocean stages to present day partial mantle melting processes.
氙（Xe）在岩石学过程中的行为，尽管对制约地幔吸气和脱气模型至关重要，但由于其易挥发的性质，以及缺乏在与岩浆形成和深部结晶相关的压力（P）和温度（T）下的直接研究，因此难以捉摸。氙在惰性气体中脱颖而出，是因为它与下地壳和上地幔的硅酸盐具有独特的反应性，这至少可以部分解释为什么已公布的矿物/熔体分配系数高达六个数量级。我们利用高 P 和高 T 原位 X 射线荧光和质谱分析，报告了氙的分配系数。研究发现，氙在与玄武岩平衡的正长石-辉石混合物中是中度不相容的（分配系数值为 0.16 ± 0.06），而在与玄武岩平衡的橄榄石中则是相容的（分配系数范围为 88 ± 22 至 302 ± 46）。因此，Xe主要集中在与结晶辉石和长石共存的玄武岩熔体中，而在深部则主要保留在橄榄石中。因此，从岩浆海洋阶段到今天的部分地幔熔化过程，在整个地球历史中，最初包含在固体地球中的 Xe 被优先保留在深层。
{"title":"Xenon compatibility in magmatic processes: Hadean to current contexts","authors":"Q. Chen, C. Sanloup, D. Horlait, G. Shen","doi":"10.7185/geochemlet.2413","DOIUrl":"https://doi.org/10.7185/geochemlet.2413","url":null,"abstract":"Xenon (Xe) behaviour in petrological processes, albeit essential to constrain mantle ingassing and degassing models, is elusive due to its volatile nature, and lack of direct investigation at the pressures (<em>P</em>) and temperatures (<em>T</em>) relevant to magma formation and crystallisation at depth. Xenon stands out amongst noble gases due to its unique reactivity with silicates of the lower crust and upper mantle, which could at least partially explain that published mineral/melt partitioning coefficients span up to six orders of magnitude. We report partition coefficients of Xe using <em>in situ</em> X-ray fluorescence at high <em>P</em> and <em>T</em>, and mass spectrometry analyses. Xenon is found to be moderately incompatible in anorthite-clinopyroxene mix in equilibrium with basalt (partition coefficient value of 0.16 ± 0.06), and compatible in olivine in equilibrium with basalt (partition coefficients in the range 88 ± 22 to 302 ± 46). While Xe is, thus, concentrated in basaltic melts coexisting with crystallising pyroxenes and feldspars, it is strongly retained in olivine at depth. Consequently, Xe originally contained in solid Earth has been preferentially retained at depth throughout Earth’s history, from the magma ocean stages to present day partial mantle melting processes.","PeriodicalId":12613,"journal":{"name":"Geochemical Perspectives Letters","volume":null,"pages":null},"PeriodicalIF":4.9,"publicationDate":"2024-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140635077","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}
D. Peters, H. Rizo, J. O’Neil, C. Hamelin, S.B. Shirey
New high precision Nd and W isotopic compositions were obtained on the same basalt samples from the Pacific-Antarctic Ridge. These provide the best estimate so far for the μ142Nd and μ182W values of the depleted mantle source of mid-ocean ridge basalts known as DMM. The PAR basalts yield a mean μ142Nd = −1.6 ± 5.0 (2 s.d.) and μ182W = −1.9 ± 3.5 (2 s.d.), which together with the literature data allow the isotope composition of the DMM to be constrained. The present-day DMM μ182W is 10–20 ppm lower than that of the Archean mantle. This decrease could be related to the broad incorporation of mantle plume material into the upper mantle, starting between 2.4 and 3 billion years ago, due to the onset of deep cold slab subduction, and its attendant return mantle flow.
{"title":"Comparative 142Nd and 182W study of MORBs and the 4.5 Gyr evolution of the upper mantle","authors":"D. Peters, H. Rizo, J. O’Neil, C. Hamelin, S.B. Shirey","doi":"10.7185/geochemlet.2412","DOIUrl":"https://doi.org/10.7185/geochemlet.2412","url":null,"abstract":"New high precision Nd and W isotopic compositions were obtained on the same basalt samples from the Pacific-Antarctic Ridge. These provide the best estimate so far for the μ<sup>142</sup>Nd and μ<sup>182</sup>W values of the depleted mantle source of mid-ocean ridge basalts known as DMM. The PAR basalts yield a mean μ<sup>142</sup>Nd = −1.6 ± 5.0 (2 s.d.) and μ<sup>182</sup>W = −1.9 ± 3.5 (2 s.d.), which together with the literature data allow the isotope composition of the DMM to be constrained. The present-day DMM μ<sup>182</sup>W is 10–20 ppm lower than that of the Archean mantle. This decrease could be related to the broad incorporation of mantle plume material into the upper mantle, starting between 2.4 and 3 billion years ago, due to the onset of deep cold slab subduction, and its attendant return mantle flow.","PeriodicalId":12613,"journal":{"name":"Geochemical Perspectives Letters","volume":null,"pages":null},"PeriodicalIF":4.9,"publicationDate":"2024-04-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140570493","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}
A.R. Brown, M. Molinas, Y. Roebbert, R. Faizova, T. Vitova, A. Sato, M. Hada, M. Abe, M. Mazzanti, S. Weyer, R. Bernier-Latmani
The two step electron transfer during bacterial reduction of UVI to UIV is typically accompanied by mass-independent fractionation of the 238U and 235U isotopes, whereby the heavy isotope accumulates in the reduced product. However, the role of the UV intermediate in the fractionation mechanism is unresolved due to the challenges associated with its chemical stability. Here, we employed the UV stabilising ligand, dpaea2-, to trap aqueous UV during UVI reduction by Shewanella oneidensis. Whilst the first reduction step from UVI to UV displayed negligible fractionation, reduction of UV to UIV revealed mass-dependent isotope fractionation (preferential reduction of the 235U), contrary to most previous observations. This surprising behaviour highlights the control that the U-coordinating ligand exerts over the balance between reactant U supply, electron transfer rate, and UIV product sequestration, suggesting that UV speciation should be considered when using U isotope ratios to reconstruct environmental redox conditions.
{"title":"The isotopic signature of UV during bacterial reduction","authors":"A.R. Brown, M. Molinas, Y. Roebbert, R. Faizova, T. Vitova, A. Sato, M. Hada, M. Abe, M. Mazzanti, S. Weyer, R. Bernier-Latmani","doi":"10.7185/geochemlet.2411","DOIUrl":"https://doi.org/10.7185/geochemlet.2411","url":null,"abstract":"The two step electron transfer during bacterial reduction of U<sup>VI</sup> to U<sup>IV</sup> is typically accompanied by mass-independent fractionation of the <sup>238</sup>U and <sup>235</sup>U isotopes, whereby the heavy isotope accumulates in the reduced product. However, the role of the U<sup>V</sup> intermediate in the fractionation mechanism is unresolved due to the challenges associated with its chemical stability. Here, we employed the U<sup>V</sup> stabilising ligand, dpaea<sup>2-</sup>, to trap aqueous U<sup>V</sup> during U<sup>VI</sup> reduction by <em>Shewanella oneidensis</em>. Whilst the first reduction step from U<sup>VI</sup> to U<sup>V</sup> displayed negligible fractionation, reduction of U<sup>V</sup> to U<sup>IV</sup> revealed mass-dependent isotope fractionation (preferential reduction of the <sup>235</sup>U), contrary to most previous observations. This surprising behaviour highlights the control that the U-coordinating ligand exerts over the balance between reactant U supply, electron transfer rate, and U<sup>IV</sup> product sequestration, suggesting that U<sup>V</sup> speciation should be considered when using U isotope ratios to reconstruct environmental redox conditions.","PeriodicalId":12613,"journal":{"name":"Geochemical Perspectives Letters","volume":null,"pages":null},"PeriodicalIF":4.9,"publicationDate":"2024-04-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140570494","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 : 2024-03-19DOI: 10.7185/geochemlet.2209cor
J. Marin-Carbonne, M.-N. Decraene, R. Havas, L. Remusat, V. Pasquier, J. Alléon, N. Zeyen, A. Bouton, S. Bernard, S. Escrig, N. Olivier, E. Vennin, A. Meibom, K. Benzerara, C. Thomazo
Abstract not available
无摘要
{"title":"Corrigendum to “Early precipitated micropyrite in microbialites: A capsule of microbial sulfur cycling” by Marin-Carbonne et al., 2022","authors":"J. Marin-Carbonne, M.-N. Decraene, R. Havas, L. Remusat, V. Pasquier, J. Alléon, N. Zeyen, A. Bouton, S. Bernard, S. Escrig, N. Olivier, E. Vennin, A. Meibom, K. Benzerara, C. Thomazo","doi":"10.7185/geochemlet.2209cor","DOIUrl":"https://doi.org/10.7185/geochemlet.2209cor","url":null,"abstract":"Abstract not available","PeriodicalId":12613,"journal":{"name":"Geochemical Perspectives Letters","volume":null,"pages":null},"PeriodicalIF":4.9,"publicationDate":"2024-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140167308","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}
A. Bragagni, R. Avanzinelli, C. Münker, F. Mastroianni, S. Conticelli
We report high precision high field strength element (HFSE) concentrations of Italian Plio-Quaternary mafic magmas. Silica-undersaturated rocks of the Roman magmatic province show high Nb/Ta. Instead, earlier silica-oversaturated rocks of the Tuscan magmatic province have unfractionated Nb/Ta. We show evidence that the high Nb/Ta of Roman magmas reflects subduction-derived, carbonate-rich melts. Similar melts may also account for high Nb/Ta in other silica-undersaturated magmas from the circum-Mediterranean (e.g., Macedonia, Bulgaria, Turkey) and the Sunda arc, previously interpreted to reflect residual rutile. We propose a genetic link between high Nb/Ta, silica-undersaturated magmas and recycling of carbonate-rich lithologies via subduction. As such, Nb/Ta can be used to trace the recycling of subducting carbonates.
{"title":"Fractionation of Nb/Ta during subduction of carbonate-rich sediments","authors":"A. Bragagni, R. Avanzinelli, C. Münker, F. Mastroianni, S. Conticelli","doi":"10.7185/geochemlet.2410","DOIUrl":"https://doi.org/10.7185/geochemlet.2410","url":null,"abstract":"We report high precision high field strength element (HFSE) concentrations of Italian Plio-Quaternary mafic magmas. Silica-undersaturated rocks of the Roman magmatic province show high Nb/Ta. Instead, earlier silica-oversaturated rocks of the Tuscan magmatic province have unfractionated Nb/Ta. We show evidence that the high Nb/Ta of Roman magmas reflects subduction-derived, carbonate-rich melts. Similar melts may also account for high Nb/Ta in other silica-undersaturated magmas from the circum-Mediterranean (<em>e.g.</em>, Macedonia, Bulgaria, Turkey) and the Sunda arc, previously interpreted to reflect residual rutile. We propose a genetic link between high Nb/Ta, silica-undersaturated magmas and recycling of carbonate-rich lithologies via subduction. As such, Nb/Ta can be used to trace the recycling of subducting carbonates.","PeriodicalId":12613,"journal":{"name":"Geochemical Perspectives Letters","volume":null,"pages":null},"PeriodicalIF":4.9,"publicationDate":"2024-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140046067","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}
D. Smrzka, Z. Lin, P. Monien, T. Chen, W. Bach, J. Peckmann, G. Bohrmann
Pyrite forms at marine hydrocarbon seeps as the result of the microbial oxidation of methane, organic matter, and crude oil coupled to sulphate reduction. Redox sensitive and nutrient trace elements in pyrite may hold valuable information on present and past seepage events, the evolution of fluid composition, as well as the presence of heavy hydrocarbon compounds from crude oil. This study uses the trace element compositions of pyrite that formed at methane seeps and crude oil-dominated seeps to constrain element mobilities during the sulphate reduction processes, and examine the degree to which specific trace elements are captured by pyrite. Pyrite forming at oil seeps shows high Mn/Fe ratios and high Mo content compared to pyrite from methane seeps. These patterns suggest either more intense or persistent sulphidic conditions, or an intensified manganese (oxy)hydroxide shuttle process at oil seeps. Copper and Zn are enriched in oil seepage-derived pyrite while Ni and V enrichment is less pronounced, suggesting either a selective uptake of specific elements by pyrite, or varying trace element compositions of organic compounds oxidised via microbial reduction.
{"title":"Pyrite-based trace element fingerprints for methane and oil seepage","authors":"D. Smrzka, Z. Lin, P. Monien, T. Chen, W. Bach, J. Peckmann, G. Bohrmann","doi":"10.7185/geochemlet.2409","DOIUrl":"https://doi.org/10.7185/geochemlet.2409","url":null,"abstract":"Pyrite forms at marine hydrocarbon seeps as the result of the microbial oxidation of methane, organic matter, and crude oil coupled to sulphate reduction. Redox sensitive and nutrient trace elements in pyrite may hold valuable information on present and past seepage events, the evolution of fluid composition, as well as the presence of heavy hydrocarbon compounds from crude oil. This study uses the trace element compositions of pyrite that formed at methane seeps and crude oil-dominated seeps to constrain element mobilities during the sulphate reduction processes, and examine the degree to which specific trace elements are captured by pyrite. Pyrite forming at oil seeps shows high Mn/Fe ratios and high Mo content compared to pyrite from methane seeps. These patterns suggest either more intense or persistent sulphidic conditions, or an intensified manganese (oxy)hydroxide shuttle process at oil seeps. Copper and Zn are enriched in oil seepage-derived pyrite while Ni and V enrichment is less pronounced, suggesting either a selective uptake of specific elements by pyrite, or varying trace element compositions of organic compounds oxidised <em>via</em> microbial reduction.","PeriodicalId":12613,"journal":{"name":"Geochemical Perspectives Letters","volume":null,"pages":null},"PeriodicalIF":4.9,"publicationDate":"2024-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140046188","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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