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":"43 1","pages":""},"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":"39 1","pages":""},"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":"19 1","pages":""},"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":"19 1","pages":""},"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":"85 1","pages":""},"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":"136 1","pages":""},"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":"43 1","pages":""},"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}
W. Carlin, B. Malvoisin, F. Brunet, B. Lanson, N. Findling, M. Lanson, T. Fargetton, L. Jeannin, O. Lhote
Ferroan brucite, (Mg,Fe)(OH)2, is among the potential mineral candidates for low temperature (<423 K) abiotic H2 production in ultramafic rocks. To verify this assumption, synthetic ferroan brucite with grain size similar to that observed in natural samples (40–100 nm) was reacted with pure water at temperatures ranging from 348 to 573 K. Experimental products are consistent with the reaction 3 Fe(OH)2brucite = Fe3O4 + H2 + 2 H2O. This reaction reached completion in ∼2 months at 378 K and is thermally activated with an activation energy of 145 ± 1 kJ/mol. The standard state formation enthalpy and the third law entropy of amakinite, Fe(OH)2, were refined from the experimental dataset. The new thermodynamic parameters imply that ferroan brucite is stable at significantly lower hydrogen activity than previously calculated. The alteration of Fe-brucite produces H2 at rates compatible with present day observations of H2 emissions in natural settings (ophiolite and mid-oceanic ridges). However, efficient fluid renewal is required, as opposed to H2 production through olivine serpentinisation, which can proceed in static hydraulic conditions.
{"title":"Kinetics of low-temperature H2 production in ultramafic rocks by ferroan brucite oxidation","authors":"W. Carlin, B. Malvoisin, F. Brunet, B. Lanson, N. Findling, M. Lanson, T. Fargetton, L. Jeannin, O. Lhote","doi":"10.7185/geochemlet.2408","DOIUrl":"https://doi.org/10.7185/geochemlet.2408","url":null,"abstract":"Ferroan brucite, (Mg,Fe)(OH)<sub>2</sub>, is among the potential mineral candidates for low temperature (<423 K) abiotic H<sub>2</sub> production in ultramafic rocks. To verify this assumption, synthetic ferroan brucite with grain size similar to that observed in natural samples (40–100 nm) was reacted with pure water at temperatures ranging from 348 to 573 K. Experimental products are consistent with the reaction 3 Fe(OH)<sub>2</sub><sup>brucite</sup> = Fe<sub>3</sub>O<sub>4</sub> + H<sub>2</sub> + 2 H<sub>2</sub>O. This reaction reached completion in ∼2 months at 378 K and is thermally activated with an activation energy of 145 ± 1 kJ/mol. The standard state formation enthalpy and the third law entropy of amakinite, Fe(OH)<sub>2</sub>, were refined from the experimental dataset. The new thermodynamic parameters imply that ferroan brucite is stable at significantly lower hydrogen activity than previously calculated. The alteration of Fe-brucite produces H<sub>2</sub> at rates compatible with present day observations of H<sub>2</sub> emissions in natural settings (ophiolite and mid-oceanic ridges). However, efficient fluid renewal is required, as opposed to H<sub>2</sub> production through olivine serpentinisation, which can proceed in static hydraulic conditions.","PeriodicalId":12613,"journal":{"name":"Geochemical Perspectives Letters","volume":"23 1","pages":""},"PeriodicalIF":4.9,"publicationDate":"2024-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140071343","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 : 2024-02-26DOI: 10.7185/geochemlet.2342cor
L. Hoare, L.J.A. Rzehak, S. Kommescher, M. Jansen, M.T. Rosing, T. Nagel, M.-A. Millet, J.E. Hoffmann, R.O.C. Fonseca
Abstract not available
无摘要
{"title":"Corrigendum to “Titanium isotope constraints on the mafic sources and geodynamic origins of Archean crust” by Hoare et al., 2023","authors":"L. Hoare, L.J.A. Rzehak, S. Kommescher, M. Jansen, M.T. Rosing, T. Nagel, M.-A. Millet, J.E. Hoffmann, R.O.C. Fonseca","doi":"10.7185/geochemlet.2342cor","DOIUrl":"https://doi.org/10.7185/geochemlet.2342cor","url":null,"abstract":"Abstract not available","PeriodicalId":12613,"journal":{"name":"Geochemical Perspectives Letters","volume":"30 1","pages":""},"PeriodicalIF":4.9,"publicationDate":"2024-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139978920","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.D. Evans, C.D. Standish, J.A. Milton, A.G. Robbins, D. Craw, G.L. Foster, D.A.H. Teagle
Serpentinised mantle rocks reflect the cumulative sum of multiple alteration events, but to date, identifying distinct serpentinisation episodes has remained challenging due to limited knowledge of the spatial distribution of tracers of fluid-rock exchange. Here we present novel high spatial resolution (∼10 μm) boron, nickel, calcium, and lithium concentration maps combined with in situ boron isotope analyses of strongly serpentinised mantle peridotites from the Troodos ophiolite, Cyprus. Our maps indicate strongly heterogenous boron concentrations with high boron concentrations in early formed serpentine replacing olivine but much lower boron contents in mesh-textured serpentine and bastitic pyroxene. Late stage crosscutting serpentine veins have very low boron concentrations. In contrast, boron isotope measurements, made at coarser scales, are remarkably uniform (mean value +11.9 ± 3.2 ‰, 1σ, n = 49). We interpret the high boron serpentine as reflecting the partial preservation of an early pervasive serpentinisation episode by fluids with high boron concentrations sourced from the dehydration of the subducting Cyprus slab. Subsequent serpentine phases with moderate to low boron reflect progressive recrystallisation and leaching by low boron concentration meteoric waters.
蛇绿岩化地幔岩石反映了多种蚀变事件的累积总和,但迄今为止,由于对流体-岩石交换示踪剂空间分布的了解有限,识别不同的蛇绿岩化事件仍然具有挑战性。在这里,我们展示了新的高空间分辨率(∼10 μm)硼、镍、钙和锂浓度图,并结合对塞浦路斯特罗多斯蛇绿岩强烈蛇绿岩化地幔橄榄岩的原位硼同位素分析。我们绘制的地图显示,硼的浓度具有强烈的异质性,早期形成的蛇纹石替代橄榄石中的硼浓度较高,而网纹蛇纹石和韧皮辉石中的硼含量则低得多。晚期横切蛇纹石矿脉中的硼含量非常低。相比之下,在较粗尺度上进行的硼同位素测量结果却非常一致(平均值+11.9 ± 3.2 ‰, 1σ, n = 49)。我们认为,高硼蛇纹石反映了塞浦路斯俯冲板块脱水过程中产生的高硼浓度流体对早期普遍蛇纹石化过程的部分保存。随后的中低硼蛇纹石相则反映了低硼浓度陨石水的逐步再结晶和沥滤作用。
{"title":"Imaging of boron in altered mantle rocks illuminates progressive serpentinisation episodes","authors":"A.D. Evans, C.D. Standish, J.A. Milton, A.G. Robbins, D. Craw, G.L. Foster, D.A.H. Teagle","doi":"10.7185/geochemlet.2407","DOIUrl":"https://doi.org/10.7185/geochemlet.2407","url":null,"abstract":"Serpentinised mantle rocks reflect the cumulative sum of multiple alteration events, but to date, identifying distinct serpentinisation episodes has remained challenging due to limited knowledge of the spatial distribution of tracers of fluid-rock exchange. Here we present novel high spatial resolution (∼10 μm) boron, nickel, calcium, and lithium concentration maps combined with <em>in situ</em> boron isotope analyses of strongly serpentinised mantle peridotites from the Troodos ophiolite, Cyprus. Our maps indicate strongly heterogenous boron concentrations with high boron concentrations in early formed serpentine replacing olivine but much lower boron contents in mesh-textured serpentine and bastitic pyroxene. Late stage crosscutting serpentine veins have very low boron concentrations. In contrast, boron isotope measurements, made at coarser scales, are remarkably uniform (mean value +11.9 ± 3.2 ‰, 1σ, n = 49). We interpret the high boron serpentine as reflecting the partial preservation of an early pervasive serpentinisation episode by fluids with high boron concentrations sourced from the dehydration of the subducting Cyprus slab. Subsequent serpentine phases with moderate to low boron reflect progressive recrystallisation and leaching by low boron concentration meteoric waters.","PeriodicalId":12613,"journal":{"name":"Geochemical Perspectives Letters","volume":"49 1","pages":""},"PeriodicalIF":4.9,"publicationDate":"2024-02-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139957000","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}