Geochemical Perspectives Letters最新文献

{"title":"Chondritic chlorine isotope composition of acapulcoites and lodranites","authors":"A. Stephant, M. Anand, C. Carli, X. Zhao, J. Davidson, T. Cuppone, G. Pratesi, I.A. Franchi","doi":"10.7185/geochemlet.2406","DOIUrl":"https://doi.org/10.7185/geochemlet.2406","url":null,"abstract":"Bulk rock chondrites and Earth’s reservoirs share a common chlorine isotopic value, while more differentiated bodies such as the Moon or Vesta record significant chlorine isotopic fractionation in their Ca phosphates. As such, an important but scarcely studied parameter is the effect of melting and differentiation processes on chlorine concentration and isotopic composition of a planetesimal. Here we report chlorine abundances and isotopic compositions for apatite in a range of primitive achondrites, acapulcoites and lodranites. These meteorites originated from a parent body that experienced some partial melting, allowing an assessment of chlorine behaviour during the early stages of planetary evolution in the inner Solar System. Overall, while bulk rock estimates of F and Cl abundances are indicative of degassing during the early stages of partial melting, no chlorine isotopic fractionation is recorded in apatite. Consequently, acapulcoites and lodranites retain their chondritic precursor isotopic signature for chlorine.","PeriodicalId":12613,"journal":{"name":"Geochemical Perspectives Letters","volume":"1 1","pages":""},"PeriodicalIF":4.9,"publicationDate":"2024-02-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139760978","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":"Reliability of Raman analyses of CO2-rich fluid inclusions as a geobarometer at Kīlauea","authors":"C.L. DeVitre, P.E. Wieser","doi":"10.7185/geochemlet.2404","DOIUrl":"https://doi.org/10.7185/geochemlet.2404","url":null,"abstract":"Interpreting signals of volcanic unrest requires knowledge of the architecture of the magmatic system, particularly the depths at which magmas are stored. Such information can be vital to help predict changes in eruptive style and vigour. However, popular petrological tools to assess magma storage depths (<em>e.g.</em>, melt inclusions) are costly, present large uncertainties, and are too slow for real time monitoring. Here, we evaluate the reliability of Raman Spectroscopy measurements of CO₂-dominated fluid inclusions as a geobarometer relative to microthermometry and melt inclusion barometry. We calculate storage pressures for 102 olivine-hosted fluid inclusions from the 2018 Lower East Rift Zone eruption of K&amp;imacr;lauea, which are statistically indistinguishable to those determined from melt inclusions. We show that calibrated Raman spectroscopy yields densities within 5–10 % of microthermometry for CO₂-dominated fluid inclusions (&lt;10 mol % H₂O) but is a far more suitable method for systems like K&amp;imacr;lauea dominated by shallow magma storage. Overall, pressures determined from fluid inclusions by Raman spectroscopy are robust and require only a fraction of the time and resources of melt inclusion studies.","PeriodicalId":12613,"journal":{"name":"Geochemical Perspectives Letters","volume":"317 1","pages":""},"PeriodicalIF":4.9,"publicationDate":"2024-01-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139663745","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":"The key role of bedrock composition in the formation of carbonates on Mars","authors":"C. Gil-Lozano, F. Baron, A. Gaudin, J.-P. Lorand, V. Fernandez, J. Hamon, N. Mangold","doi":"10.7185/geochemlet.2403","DOIUrl":"https://doi.org/10.7185/geochemlet.2403","url":null,"abstract":"Martian carbonates are fundamental minerals for understanding the geochemical and climatic evolution of the planet and the search for potential life, representing one of the key objectives for the Perseverance rover at Jezero Crater. However, the scarcity of carbonate reservoirs on the surface compared to the extent of terrestrial carbonates questions whether these carbonates are indicators of past surface conditions or products from deeper processes unrelated to martian climate. We investigate the formation of carbonates by surface weathering under a CO₂ atmosphere in a suite of individual minerals and martian simulants based on the early Mars crust composition. We identify the formation of magnesium carbonates in olivine-bearing samples, but not in the early martian crust simulants. These findings are consistent with the association of carbonates with olivine-rich substrate detected on Mars and highlight the role of the substratum composition in the distribution of carbonates formed by surface processes. Hence, we conclude that the limited surface reservoirs of carbonate are reconcilable with the existence of a CO₂-rich atmosphere on early Mars.","PeriodicalId":12613,"journal":{"name":"Geochemical Perspectives Letters","volume":"190 1","pages":""},"PeriodicalIF":4.9,"publicationDate":"2024-01-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139577823","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 elemental and isotopic variations at magmatic temperatures","authors":"W. Wang, A.J. Dickson, M.A. Stow, M. Dellinger, K.W. Burton, P.S. Savage, R.G. Hilton, J. Prytulak","doi":"10.7185/geochemlet.2402","DOIUrl":"https://doi.org/10.7185/geochemlet.2402","url":null,"abstract":"Recent analytical advances in the measurement of rhenium (Re) isotope ratios allow its potential as a palaeoredox and chemical weathering proxy to be explored. However, a successful isotopic proxy must be grounded by an understanding of its composition and behaviour in the solid Earth. Here, we present Re concentrations and Re isotopic (δ¹⁸⁷Re) compositions for a well-characterised sequence of lavas from Hekla volcano, Iceland. The concentration of Re varies from 0.02 to 1.4 ng/g, decreasing from basalt to more evolved lavas. We show that the crystallisation and removal of magnetite is responsible for the Re decrease in this system. By contrast, δ¹⁸⁷Re values for the same suite of samples show a relatively narrow range (−0.45 to −0.22 ‰), suggesting minimal resolvable Re isotope fractionation between magnetite and the silicate melt. Together with other samples, including mid-ocean ridge basalts, these first igneous data can be used to estimate a baseline for terrestrial materials (δ¹⁸⁷Re = −0.33 ± 0.15 ‰, 2 s.d., <em>n</em> = 14), from which low-temperature Re isotope variations in Earth’s surficial environments can be assessed, alongside the global isotope mass balance of Re.","PeriodicalId":12613,"journal":{"name":"Geochemical Perspectives Letters","volume":"50 1","pages":""},"PeriodicalIF":4.9,"publicationDate":"2024-01-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139414518","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":"Magnesiowüstite as a major nitrogen reservoir in Earth’s lowermost mantle","authors":"G. Rustioni, M. Wiedenbeck, N. Miyajima, A. Chanyshev, H. Keppler","doi":"10.7185/geochemlet.2401","DOIUrl":"https://doi.org/10.7185/geochemlet.2401","url":null,"abstract":"Ferropericlase (Mg,Fe)O is after bridgmanite the most abundant phase in the lower mantle. The ultralow velocity zones above the core-mantle boundary may contain very Fe-rich magnesiowüstite (Fe,Mg)O, possibly as result of the fractional crystallisation of a basal magma ocean. We have experimentally studied the solubility of nitrogen in the ferropericlase-magnesiowüstite solid solution series as function of iron content. Multi-anvil experiments were performed at 20–33 GPa and 1600–1800 °C in equilibrium with Fe metal. Nitrogen solubility increases from a few tens ppm (μg/g) for Mg-rich ferropericlase to more than 10 wt. % for nearly pure wüstite. Such high solubilities appear to be due to solid solution with NiAs-type FeN. Our data suggest that during fractional crystallisation of a magma ocean, the core-mantle boundary would have become extremely enriched with nitrogen, such that the deep mantle today could be the largest nitrogen reservoir on Earth. The often discussed “subchondritic N/C” ratio of the bulk silicate Earth may be an artefact of insufficient sampling of this deep reservoir.","PeriodicalId":12613,"journal":{"name":"Geochemical Perspectives Letters","volume":"14 1","pages":""},"PeriodicalIF":4.9,"publicationDate":"2024-01-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139105594","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":"Titanium isotope constraints on the mafic sources and geodynamic origins of Archean crust","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.2342","DOIUrl":"https://doi.org/10.7185/geochemlet.2342","url":null,"abstract":"The timing and formation of Earth’s first continents during the Archean are subjects of significant debate. By examining titanium isotope variations in Archean Tonalite-Trondhjemite-Granodiorite (TTG) rocks and using advanced thermodynamic modelling, we can narrow down the processes involved and emphasise the role of mafic precursor compositions. In our study of Eoarchean Isua metabasalts and Itsaq tonalites in southern West Greenland, we observed a pattern of increasing Ti isotope enrichment with higher SiO₂ content, resembling the compositions found in modern subduction zone rocks. Our modelling suggests that the Ti isotope variations in TTGs can be best explained by a combination of partial melting of low TiO₂ metabasalts and subsequent crystallisation of tonalitic magmas, resulting in heavier Ti isotopes. This means that Ti isotopes help us distinguish the contributions of various mafic sources and fractional crystallisation during TTG formation. In the case of Itsaq tonalites and many other Eoarchean TTGs, low TiO₂ tholeiitic metabasalts with arc-like characteristics likely represent the mafic source rocks, suggesting the formation of some of Earth’s earliest continental crust within a proto-subduction zone setting.","PeriodicalId":12613,"journal":{"name":"Geochemical Perspectives Letters","volume":"9 1","pages":""},"PeriodicalIF":4.9,"publicationDate":"2023-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139022542","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":"Nucleosynthetic s-Process Depletion in Mo from Ryugu samples returned by Hayabusa2","authors":"N. Nakanishi, T. Yokoyama, A. Ishikawa, R.J. Walker, Y. Abe, J. Aléon, C.M.O'D Alexander, S. Amari, Y. Amelin, K.-I. Bajo, M. Bizzarro, A. Bouvier, R.W. Carlson, M. Chaussidon, B.-G. Choi, N. Dauphas, A.M. Davis, T. Di Rocco, W. Fujiya, R. Fukai, I. Gautam, M.K. Haba, Y. Hibiya, H. Hidaka, H. Homma, P. Hoppe, G.R. Huss, K. Ichida, T. Iizuka, T.R. Ireland, S. Itoh, N. Kawasaki, N.T. Kita, K. Kitajima, T. Kleine, S. Komatani, A.N. Krot, M.-C. Liu, Y. Masuda, M. Morita, K. Motomura, F. Moynier, I. Nakai, K. Nagashima, A. Nguyen, L. Nittler, M. Onose, A. Pack, C. Park, L. Piani, L. Qin, S.S. Russell, N. Sakamoto, M. Schönbächler, L. Tafla, H. Tang, K. Terada, Y. Terada, T. Usui, S. Wada, M. Wadhwa, K. Yamashita, Q.-Z. Yin, S. Yoneda, E.D. Young, H. Yui, A.-C. Zhang, T. Nakamura, H. Naraoka, T. Noguchi, R. Okazaki, K. Sakamoto, H. Yabuta, M. Abe, A. Miyazaki, A. Nakato, M. Nishimura, T. Okada, T. Yada, K. Yogata, S. Nakazawa, T. Saiki, S. Tanaka, F. Terui, Y. Tsuda, S.-I. Watanabe, M. Yoshikawa, S. Tachibana, H. Yurimoto","doi":"10.7185/geochemlet.2341","DOIUrl":"https://doi.org/10.7185/geochemlet.2341","url":null,"abstract":"Initial analyses of samples collected from two locations on the asteroid Ryugu indicated that the mineralogical, chemical, and isotopic characteristics of the Ryugu samples show similarities to carbonaceous chondrites, particularly the Ivuna-type (CI) group. In this study, we analysed a composite sample of four bulk Ryugu samples (A0106, A0106-A0107, C0107, and C0108) collected from both sampling locations that were combined in order to determine its mass independent Mo isotopic composition and reveal contributions from diverse nucleosynthetic sources. The ɛ⁹⁴Mo and ɛ⁹⁵Mo values for the Ryugu sample are characterised by the carbonaceous chondrite (CC)-type, which is consistent with the nucleosynthetic isotope compositions observed for other elements (Cr, Ti, Fe, and Zn). The Ryugu composite sample, however, is characterised by greater <em>s</em>-process depletion of Mo isotopes compared with any known bulk carbonaceous chondrite, even including CI chondrites. The observed Mo isotopic signature in the Ryugu composite was most likely caused by either incomplete digestion of <em>s</em>-process-rich presolar SiC, or biased sampling of materials enriched in aqueously-formed secondary minerals characterised by <em>s</em>-process-poor Mo isotopes, resulting from the physicochemical separation between <em>s</em>-process-rich presolar grains and a complementary <em>s</em>-process-poor aqueous fluid in the Ryugu parent body.","PeriodicalId":12613,"journal":{"name":"Geochemical Perspectives Letters","volume":"32 1","pages":""},"PeriodicalIF":4.9,"publicationDate":"2023-12-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138824962","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":"Stable cerium isotopes as a tracer of oxidation reactions","authors":"P. Bonnand, M. Boyet, C. Bosq","doi":"10.7185/geochemlet.2340","DOIUrl":"https://doi.org/10.7185/geochemlet.2340","url":null,"abstract":"Redox conditions in past oceans have attracted significant interest and many proxies have been used to probe redox changes through time. For example, the redox dependent behaviour of Ce, resulting in negative or positive elemental Ce anomalies, has been widely used. More recently, mass dependent Ce isotopic variations have been proposed as a powerful tool to study Ce oxidation in natural environments. In this study, we demonstrate, for the first time, that Ce isotopes are fractionated during oxidation reaction, confirming the utility of Ce isotopes to study redox reactions. This result suggests that seawater Ce isotopic composition should be fractionated toward heavy values relative to the continental crust. Measured natural rock samples (carbonates, banded iron formations and Mn nodules) have variable Ce isotopic compositions, ranging from −0.055 ± 0.045 ‰ to +0.280 ± 0.045 ‰. The relation between Ce elemental anomalies and Ce isotopic composition in carbonate rocks suggest that mass dependent Ce isotopes can be used to distinguish elemental anomalies produced by oxidation reactions from those produced by other processes. Coupled with La-Ce chronology, mass dependent Ce isotope analysis is a very powerful tool to study redox reactions in past oceans.","PeriodicalId":12613,"journal":{"name":"Geochemical Perspectives Letters","volume":"9 1","pages":""},"PeriodicalIF":4.9,"publicationDate":"2023-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138743596","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":"Authigenic minerals reflect microbial control on pore waters in a ferruginous analogue","authors":"A. Vuillemin, M. Morlock, A. Paskin, L.G. Benning, C. Henny, J. Kallmeyer, J.M. Russell, H. Vogel","doi":"10.7185/geochemlet.2339","DOIUrl":"https://doi.org/10.7185/geochemlet.2339","url":null,"abstract":"Ferruginous conditions prevailed in the oceans through much of Earth’s history. However, minerals recording these conditions remain difficult to interpret in terms of biogeochemical processes prior to lithification. In Lake Towuti, Indonesia, ferruginous sediments are deposited under anoxic sulfate-poor conditions similar to the Proterozoic oceans, allowing the study of mineralogical (trans)formations during microbial diagenesis.<br/>Comprehensive pore water geochemistry, high resolution geochemical core profiles, and electron microscopy of authigenic minerals revealed <em>in situ</em> formation of magnetite, millerite, and abundant siderite and vivianite along a 100 m long sequence. Framboidal magnetites represent primary pelagic precipitates, whereas millerite, a sulfide mineral often overlooked under sulfate-poor conditions, shows acicular aggregates entangled with siderite and vivianite resulting from saturated pore waters and continuous growth during burial. These phases act as biosignatures of microbial iron and sulfate reduction, fermentation and methanogenesis, processes clearly traceable in pore water profiles.<br/>Variability in metal and organic substrates attests to environment driven processes, differentially sustaining microbial processes along the stratigraphy. Geochemical profiles resulting from microbial activity over 200 kyr after deposition provide constraints on the depth and age of mineral formation within ferruginous records.","PeriodicalId":12613,"journal":{"name":"Geochemical Perspectives Letters","volume":"6 1","pages":""},"PeriodicalIF":4.9,"publicationDate":"2023-12-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138554897","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":"Titanium isotope constraints on the mafic sources and geodynamic origins of Archean crust","authors":"L. Hoare, L. Rzehak, S. Kommescher, Moritz Jansen, M. Rosing, Thorsten Nagel, M. Millet, J. E. Hoffmann, R. Fonseca","doi":"10.7185/geochemlet.2342","DOIUrl":"https://doi.org/10.7185/geochemlet.2342","url":null,"abstract":"Abstract","PeriodicalId":12613,"journal":{"name":"Geochemical Perspectives Letters","volume":"74 ","pages":""},"PeriodicalIF":4.9,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"139026011","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}