{"title":"Earth Observation Applications and Global Policy Frameworks","authors":"","doi":"10.1002/9781119536789","DOIUrl":"https://doi.org/10.1002/9781119536789","url":null,"abstract":"","PeriodicalId":12504,"journal":{"name":"Geophysical Monograph Series","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-08-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77901087","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Watkins, J. Christensen, D. DePaolo, F. Ryerson
{"title":"Isotopic Constraints on Earth System Processes","authors":"J. Watkins, J. Christensen, D. DePaolo, F. Ryerson","doi":"10.1002/9781119595007","DOIUrl":"https://doi.org/10.1002/9781119595007","url":null,"abstract":"Laboratory experiments were used to investigate diffusive isotopic fractionation of calcium and potassium in phonoliterhyolite diffusion couples. The starting compositions have very different SiO2 and K2O, but similar CaO. These were juxtaposed and held in a completely molten state at 1450°C and 1.0 GPa for durations of 2.5 or 6 hours in a piston cylinder apparatus. The resulting majorelement diffusion profiles exhibit many complexities, including uphill diffusion of all major oxide components. The diffusive fluxes for SiO2, K2O, and CaO were modeled using a published modified effective binary diffusion model, whereby diffusion is driven by activity gradients that are solely a function of the timeevolving SiO2 concentration. Both Ca and K exhibit large diffusive isotope effects that can be explained by imposing a mass dependence on the diffusion coefficients used to model the majorelement profiles. The mass dependence is parameterized in terms of the inverse ratio of the isotope masses raised to an empirically determined exponent β (i.e., Di/Dj = [mj/mi] β). Our results confirm that β factors vary depending on the element as well as liquid composition, and that large diffusive isotope effects can arise even in the absence of a large initial concentration gradient. The retrieved β factor for Ca (0.10 ± 0.02) is typical of Ca in natural silicate liquids, whereas the β factor for K (0.25 ± 0.03) is the highest value yet reported, suggesting that large diffusive K isotope effects may yet be found in highT environments. 1 Department of Earth Sciences, University of Oregon, Eugene, Oregon, USA 2 Earth and Environmental Science Area, Energy Geosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA 3 Department of Earth and Planetary Science, University of California, Berkeley, California, USA 4 Atmospheric, Earth, and Energy Division, Lawrence Livermore National Laboratory, Livermore, California, USA melting and (re)crystallization. Experimental studies have shown that diffusion is capable of generating measurable (subpermil) to large (tens of permil) kinetic isotopic fractionations that can account for some of this variability, and detailed knowledge of these effects can yield unique insights into the molecular level controls on diffusive transport and the role of kinetics in the formation of minerals in high temperature settings (Antonelli et al., 2019b; Barrat et al., 2005; Beck et al., 2006; Chen et al., 2018; Chopra et al., 2012; Dauphas, 2007; Dauphas et al., 2010; Gallagher & Elliott, 2009; Gao et al., 2011; Jeffcoate et al., 2007; Kil et al., 2016; Lundstrom et al., 2005; Marschall et al., 2007; Mueller et al., 2014; Oeser et al., 2015; Parkinson et al., 2007; Richter et al., 2009, 2014, 2016, 2017; Roskosz et al., 2006; Rudnick & Ionov, 2007; Sio et al., 2013; 28 ISOTOPIC CONSTRAINTS ON EARTH SYSTEM PROCESSES Su et al., 2016; Teng et al., 2006, 2011; Wu et al., 2018; Zhao et al., 2017). Current knowledge of","PeriodicalId":12504,"journal":{"name":"Geophysical Monograph Series","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81242710","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Douglas Alsdorf, Merci Beaucoup, Raphael M. Tshimanga, G. D. M. N'kaya, Douglas Alsdorf
{"title":"Hydrologie, Climat et Biogéochimie du Bassin du Congo","authors":"Douglas Alsdorf, Merci Beaucoup, Raphael M. Tshimanga, G. D. M. N'kaya, Douglas Alsdorf","doi":"10.1002/9781119842125","DOIUrl":"https://doi.org/10.1002/9781119842125","url":null,"abstract":"","PeriodicalId":12504,"journal":{"name":"Geophysical Monograph Series","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2022-02-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89395049","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Magma Redox Geochemistry","authors":"M. Blanchard, N. Dauphas","doi":"10.1002/9781119473206","DOIUrl":"https://doi.org/10.1002/9781119473206","url":null,"abstract":"Isotopes provide valuable insights into the complex geochemical behavior of iron. To put the wealth of Fe isotopic data measured in natural samples into a quantitative framework, it is important to know how iron isotopes are fractionated at equilibrium between co-existing iron-bearing phases or species. These isotopic equilibrium fractionation factors can be derived from isotopic exchange experiments and the study of natural samples, but can also be calculated from partition functions, whose main contribution is the vibrational energy. This approach relies on first-principles calculations (atomistic modeling based on quantum mechanics) and vibrational spectroscopies (Mössbauer and Nuclear Resonant Inelastic X-ray Scattering – NRIXS). Comparison of the results obtained from these techniques provides confidence in their reliability and improves our understanding of the parameters controlling iron isotopic fractionation among coexisting phases. After an introduction to the theory and methods applied in this field, the chapter will review how NRIXS and first-principles calculations help interpret iron isotopic variations in natural rocks and minerals. At equilibrium, the heavy isotopes of iron will concentrate in the phases where the interatomic force constants are the greatest, meaning in the phases where iron bonds are the stiffest. Higher oxidation state, higher covalency, and lower coordination (shorter bond length) tend to be associated with stronger bonds and heavy iron isotope enrichments.","PeriodicalId":12504,"journal":{"name":"Geophysical Monograph Series","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-09-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87779597","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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