000124024 001__ 124024
000124024 005__ 20230330095440.0
000124024 0247_ $$2doi$$a10.1016/j.chemgeo.2022.121213
000124024 0248_ $$2sideral$$a132667
000124024 037__ $$aART-2023-132667
000124024 041__ $$aeng
000124024 100__ $$0(orcid)0000-0002-1954-6180$$aLaita, Elisa
000124024 245__ $$aNanoSIMS as an analytical tool for measuring oxygen and hydrogen isotopes in clay minerals from palaeosols: Analytical procedure and preliminary results
000124024 260__ $$c2023
000124024 5060_ $$aAccess copy available to the general public$$fUnrestricted
000124024 5203_ $$aOxygen and hydrogen isotope composition of neoformed clay minerals is commonly used as a palaeoclimatic proxy. Usually, sediments and rocks (including palaeosols) contain not only neoformed clay minerals, but also detrital and/or diagenetic ones. Together with the usually small size (micro- or nanometric) of the clay minerals in these materials, this can generate difficulties during isotopic analyses by conventional spectrometry. To avoid this problem, we used nanoscale secondary ion mass spectrometry (NanoSIMS) to analyse neoformed clay minerals included in palaeosol levels in early Barremian continental profiles located in NE Spain. The bottom levels of the profiles are rich in kaolinite, whereas the top levels contain smectite (beidellite-type). The isotopic compositions of pure powder standards of kaolinite and beidellite were measured in bulk by conventional mass spectrometry to obtain reference values for calibrating the instrumental mass fractionation. Two common preparation techniques for geological samples were tested (thin sections and thick polished sections), revealing that thin sections are more suitable for NanoSIMS analysis due to their lower resin content. The high spatial resolution of the instrument allowed the elemental mapping of the samples, permitting the localization of the minerals of interest and the measurement of isotopic ratios at selected points (1 x 1 μm2) within the samples. The preliminary isotopic results allowed to distinguish a decrease in the average 18O/16O and D/H ratios from the kaolinite in the bottom levels to the smectite in the top levels, reflecting a change in the climatic conditions. The average δ18O and δD values obtained for kaolinite (δ18OSMOW=18±15‰; δDSMOW=-82±36‰ and δ18OSMOW=14±4‰; δDSMOW=-97±37‰) and smectite (δ18OSMOW=13±14‰; δDSMOW=-167±87‰ and δ18OSMOW=11±6‰; δDSMOW=-180±40‰;), respectively, are consistent with the crystallization of the clays in weathering conditions. Despite the uncertainties of these preliminary isotopic measures, the results obtained allowed to estimate an average temperature for kaolinite formation of 21-22°C, and of 16-17°C for smectite. Given suitable calibration using pure isotopic standards and adequate sample preparation, NanoSIMS can thus have a great applicability in palaeoclimatic studies involving the oxygen and hydrogen isotopic composition of nanometre-sized clay minerals from palaeosols samples.
000124024 536__ $$9info:eu-repo/grantAgreement/ES/DGA-FEDER/E18-20R-Aragosaurus-Recursos Geológicos y Paleoambientes$$9info:eu-repo/grantAgreement/ES/MCIU/PID2021-123127OB-I00$$9info:eu-repo/grantAgreement/ES/MCIU/RTI2018-093419-B-100
000124024 540__ $$9info:eu-repo/semantics/openAccess$$aby-nc-nd$$uhttp://creativecommons.org/licenses/by-nc-nd/3.0/es/
000124024 655_4 $$ainfo:eu-repo/semantics/article$$vinfo:eu-repo/semantics/publishedVersion
000124024 700__ $$aSubirana, Maria Angels
000124024 700__ $$aSchaumlöffel, Dirk
000124024 700__ $$0(orcid)0000-0002-2169-4561$$aYuste, Alfonso$$uUniversidad de Zaragoza
000124024 700__ $$0(orcid)0000-0002-4970-6333$$aBauluz, Blanca$$uUniversidad de Zaragoza
000124024 7102_ $$12000$$2120$$aUniversidad de Zaragoza$$bDpto. Ciencias de la Tierra$$cÁrea Cristalografía Mineralog.
000124024 773__ $$g615 (2023), 121213 [14 pp.]$$pChem. geol.$$tCHEMICAL GEOLOGY$$x0009-2541
000124024 8564_ $$s5690966$$uhttps://zaguan.unizar.es/record/124024/files/texto_completo.pdf$$yVersión publicada
000124024 8564_ $$s2331167$$uhttps://zaguan.unizar.es/record/124024/files/texto_completo.jpg?subformat=icon$$xicon$$yVersión publicada
000124024 909CO $$ooai:zaguan.unizar.es:124024$$particulos$$pdriver
000124024 951__ $$a2023-03-30-09:42:30
000124024 980__ $$aARTICLE