M.A. Antonelli, G. Sartori, A. Giuliani, E.A. Schauble, J. Hoffmann, M.W. Schmidt
Stable calcium isotopes have been used to suggest that subducted marine carbonates are frequently involved in the formation of carbonatites. Significant Ca isotope fractionations during carbonatite petrogenesis, however, could lead to a dramatically different picture. We present Ca isotope data for (i) coexisting (immiscible) carbonatite and silicate melts from high temperature centrifuging piston cylinder experiments, (ii) primary apatite and calcite/dolomite from natural carbonatites, and (iii) ab initio estimates for equilibrium Ca isotope partitioning in calcite, dolomite, and ankerite. Carbonatitic melts have lower δ44Ca than their conjugate silicate melts, with an equilibrium fractionation factor [1000lnα(1000K)] of −0.21 ± 0.06 (tSE). We develop a quantitative four stage model for carbonatite petrogenesis (partial melting followed by fractional crystallisation, silicate-carbonatite melt immiscibility, and calcite/apatite accumulation) that fully explains our natural data (average δ44CaBSE of −0.30 ± 0.03 ‰) and those from recent studies, without requiring isotopic contributions from recycled marine carbonates. Our results suggest that lighter isotopes of similarly bound cations (e.g., Mg, Fe, Sr, Ba, Zn) should be preferentially incorporated into carbonatitic melts and that calciocarbonatite formation involves melt immiscibility after differentiation of mantle-derived alkaline CO2-bearing silicate melts.
{"title":"Calcium isotope fractionation during melt immiscibility and carbonatite petrogenesis","authors":"M.A. Antonelli, G. Sartori, A. Giuliani, E.A. Schauble, J. Hoffmann, M.W. Schmidt","doi":"10.7185/geochemlet.2338","DOIUrl":"https://doi.org/10.7185/geochemlet.2338","url":null,"abstract":"Stable calcium isotopes have been used to suggest that subducted marine carbonates are frequently involved in the formation of carbonatites. Significant Ca isotope fractionations during carbonatite petrogenesis, however, could lead to a dramatically different picture. We present Ca isotope data for (i) coexisting (immiscible) carbonatite and silicate melts from high temperature centrifuging piston cylinder experiments, (ii) primary apatite and calcite/dolomite from natural carbonatites, and (iii) <em>ab initio</em> estimates for equilibrium Ca isotope partitioning in calcite, dolomite, and ankerite. Carbonatitic melts have lower δ<sup>44</sup>Ca than their conjugate silicate melts, with an equilibrium fractionation factor [1000lnα(1000K)] of −0.21 ± 0.06 (tSE). We develop a quantitative four stage model for carbonatite petrogenesis (partial melting followed by fractional crystallisation, silicate-carbonatite melt immiscibility, and calcite/apatite accumulation) that fully explains our natural data (average δ<sup>44</sup>Ca<sub>BSE</sub> of −0.30 ± 0.03 ‰) and those from recent studies, without requiring isotopic contributions from recycled marine carbonates. Our results suggest that lighter isotopes of similarly bound cations (<em>e.g</em>., Mg, Fe, Sr, Ba, Zn) should be preferentially incorporated into carbonatitic melts and that calciocarbonatite formation involves melt immiscibility after differentiation of mantle-derived alkaline CO<sub>2</sub>-bearing silicate melts.","PeriodicalId":12613,"journal":{"name":"Geochemical Perspectives Letters","volume":"1 1","pages":""},"PeriodicalIF":4.9,"publicationDate":"2023-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138543170","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":"Rare evidence for the existence of a Hadean enriched mantle reservoir","authors":"V.B. Garcia, J. O’Neil, E.L. Dantas","doi":"10.7185/geochemlet.2336","DOIUrl":"https://doi.org/10.7185/geochemlet.2336","url":null,"abstract":"","PeriodicalId":12613,"journal":{"name":"Geochemical Perspectives Letters","volume":"92 4","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135456234","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}
J. Kaare-Rasmussen, D. Peters, H. Rizo, R.W. Carlson, S.G. Nielsen, F. Horton
{"title":"Tungsten isotopes in Baffin Island lavas: Evidence of Iceland plume evolution","authors":"J. Kaare-Rasmussen, D. Peters, H. Rizo, R.W. Carlson, S.G. Nielsen, F. Horton","doi":"10.7185/geochemlet.2337","DOIUrl":"https://doi.org/10.7185/geochemlet.2337","url":null,"abstract":"","PeriodicalId":12613,"journal":{"name":"Geochemical Perspectives Letters","volume":"20 2","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135456369","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}
M.A. Stow, J. Prytulak, K.W. Burton, G.M. Nowell, E.W. Marshall, S.A. Halldórsson, S. Matthews, M.B. Rasmussen, E. Ranta, A. Caracciolo
{"title":"No V-Fe-Zn isotopic variation in basalts from the 2021 Fagradalsfjall eruption","authors":"M.A. Stow, J. Prytulak, K.W. Burton, G.M. Nowell, E.W. Marshall, S.A. Halldórsson, S. Matthews, M.B. Rasmussen, E. Ranta, A. Caracciolo","doi":"10.7185/geochemlet.2335","DOIUrl":"https://doi.org/10.7185/geochemlet.2335","url":null,"abstract":"","PeriodicalId":12613,"journal":{"name":"Geochemical Perspectives Letters","volume":"49 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136153890","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":"Primordial noble gas isotopes from immoderate crushing of an Icelandic basalt glass","authors":"R. Parai","doi":"10.7185/geochemlet.2331","DOIUrl":"https://doi.org/10.7185/geochemlet.2331","url":null,"abstract":"","PeriodicalId":12613,"journal":{"name":"Geochemical Perspectives Letters","volume":"87 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134976795","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 : 2023-10-01DOI: 10.7185/geochemlet.2318cor
J.M. Domingos, E. Runge, C. Dreher, T.-H. Chiu, J. Shuster, S. Fischer, A. Kappler, J.-P. Duda, J. Xu, M. Mansor
{"title":"Corrigendum to “Inferred pyrite growth via the particle attachment pathway in the presence of trace metals” by Domingos et al., 2023","authors":"J.M. Domingos, E. Runge, C. Dreher, T.-H. Chiu, J. Shuster, S. Fischer, A. Kappler, J.-P. Duda, J. Xu, M. Mansor","doi":"10.7185/geochemlet.2318cor","DOIUrl":"https://doi.org/10.7185/geochemlet.2318cor","url":null,"abstract":"","PeriodicalId":12613,"journal":{"name":"Geochemical Perspectives Letters","volume":"47 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135811091","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}
C.L. Kirkland, T.E. Johnson, J. Gillespie, L. Martin
Analytical methods SIMS U–Pb Sample AC13 was collected by Stephen Moorbath from the University of Oxford in July 1995, from 500 metres NNW of the Acasta camp. Zircon crystals from sample AC13 were analysed for U–Th–Pb isotopes using the SHRIMP II ion probe at Curtin University following standard operating procedures (Wingate and Kirkland, 2014). The zircon surface was sputtered with a primary, mass-filtered (O2) − beam with ~ 2 nA current, focused to a ~ 15 μm spot. The mass resolution, M/ΔM, was better than 5000. Twenty-two analyses of the 91500 zircon reference material (Wiedenbeck et al., 1995) were obtained during the session, all of which indicate an external spot-to-spot (reproducibility) uncertainty of 1.33% (1σ) and a U/Pb calibration uncertainty of 0.45% (1σ). These calibration uncertainties are included in the calculated uncertainties on U/Pb* ratios and dates listed in Table S1. The OG1 zircon reference material was analysed as an unknown and yielded a weighted mean Pb/Pb age of 3458 ± 7 Ma (MSWD = 0.51, n = 5), within accepted values (Stern et al., 2009). No fractionation correction on Pb/Pb was deemed necessary. Common-Pb corrections were applied to all analyses using contemporaneous common Pb determined according to the model of Stacey and Kramers (1975) based on Pb counts. The Excel-based program Squid 2 (Ludwig, 2001) was used for data processing and data were plotted using Isoplot (Ludwig, 2003).
{"title":"Ion imaging of ancient zircon","authors":"C.L. Kirkland, T.E. Johnson, J. Gillespie, L. Martin","doi":"10.7185/geochemlet.2332","DOIUrl":"https://doi.org/10.7185/geochemlet.2332","url":null,"abstract":"Analytical methods SIMS U–Pb Sample AC13 was collected by Stephen Moorbath from the University of Oxford in July 1995, from 500 metres NNW of the Acasta camp. Zircon crystals from sample AC13 were analysed for U–Th–Pb isotopes using the SHRIMP II ion probe at Curtin University following standard operating procedures (Wingate and Kirkland, 2014). The zircon surface was sputtered with a primary, mass-filtered (O2) − beam with ~ 2 nA current, focused to a ~ 15 μm spot. The mass resolution, M/ΔM, was better than 5000. Twenty-two analyses of the 91500 zircon reference material (Wiedenbeck et al., 1995) were obtained during the session, all of which indicate an external spot-to-spot (reproducibility) uncertainty of 1.33% (1σ) and a U/Pb calibration uncertainty of 0.45% (1σ). These calibration uncertainties are included in the calculated uncertainties on U/Pb* ratios and dates listed in Table S1. The OG1 zircon reference material was analysed as an unknown and yielded a weighted mean Pb/Pb age of 3458 ± 7 Ma (MSWD = 0.51, n = 5), within accepted values (Stern et al., 2009). No fractionation correction on Pb/Pb was deemed necessary. Common-Pb corrections were applied to all analyses using contemporaneous common Pb determined according to the model of Stacey and Kramers (1975) based on Pb counts. The Excel-based program Squid 2 (Ludwig, 2001) was used for data processing and data were plotted using Isoplot (Ludwig, 2003).","PeriodicalId":12613,"journal":{"name":"Geochemical Perspectives Letters","volume":"73 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134978019","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, Y. Roebbert, A. Sato, M. Hada, M. Abe, S. Weyer, R. Bernier-Latmani
{"title":"Contribution of the nuclear field shift to kinetic uranium isotope fractionation","authors":"A.R. Brown, Y. Roebbert, A. Sato, M. Hada, M. Abe, S. Weyer, R. Bernier-Latmani","doi":"10.7185/geochemlet.2333","DOIUrl":"https://doi.org/10.7185/geochemlet.2333","url":null,"abstract":"","PeriodicalId":12613,"journal":{"name":"Geochemical Perspectives Letters","volume":"64 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135607201","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}
J Greer, B Zhang, D Isheim, D.N. Seidman, A. Bouvier, P.R. Heck
{"title":"4.46 Ga zircons anchor chronology of lunar magma ocean","authors":"J Greer, B Zhang, D Isheim, D.N. Seidman, A. Bouvier, P.R. Heck","doi":"10.7185/geochemlet.2334","DOIUrl":"https://doi.org/10.7185/geochemlet.2334","url":null,"abstract":"","PeriodicalId":12613,"journal":{"name":"Geochemical Perspectives Letters","volume":"36 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136054349","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 direct observation and interpretation of gas hydrate decomposition with ocean depth","authors":"L. Ma, Z. Luan, Z. Du, X. Zhang, Y. Zhang","doi":"10.7185/geochemlet.2327","DOIUrl":"https://doi.org/10.7185/geochemlet.2327","url":null,"abstract":"Abstract","PeriodicalId":12613,"journal":{"name":"Geochemical Perspectives Letters","volume":" ","pages":""},"PeriodicalIF":4.9,"publicationDate":"2023-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45023083","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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