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      In situ Sr isotope analyses by LA-MC-ICP-MS of igneous apatite and plagioclase from magmatic rocks at the CPGeo-USP Translated title: Microanálises isotópicas de Sr de plagioclásio e apatita magmáticos via LA-MC-ICP-MS no CPGeo-USP

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          Abstract

          ABSTRACT: This contribution describes the successful implementation of in situ Sr isotope analyses by LA-MC-ICP-MS at the CPGeo-USP. The choice for an analytical configuration using measurements of half-masses allows the accurate assessment of lanthanide interferences, permitting the determination of Sr isotopes in important REE-rich accessory phases, such as apatite. Likewise, the on-peak-zero method effectively corrects the background contribution (both from Kr and residual Sr contributions from previous ablations) to the signals of the unknown samples. The analytical campaigns resulted in an accuracy, in respect to reference TIMS values, better than 57 ppm (~ ±0.000057 2σ SD) for a modern coral and the Batjberg clinopyroxene which impart significant quality to our data. Similarly, the majority of the stable Sr isotope ratios are close to the accepted values, which also confirms the effectiveness of the method. The achieved accuracy allows the identification and investigation of spatially-controlled isotopic heterogeneities on the micrometric scale in several Sr-rich minerals (apatite, carbonates, plagioclase, and clinopyroxene) with important implications to the understanding of relevant geochemical processes, particularly AFC, source geochemical heterogeneities and magma-mixing.

          Translated abstract

          RESUMO: A presente contribuição descreve a implementação da rotina de microanálises isotópicas de Sr via LA-MC-ICP-MS no CPGeo-USP. A escolha por uma rotina analítica envolvendo a medição de meias-massas (p.ex. 171Yb2+) possibilitou a adequada correção das interferências de lantanídeos, permitindo a determinação precisa de isotopos de Sr em fases minerais acessórias ricas em REE, como a apatita. O método de medições on-peak-zero permitiu a correção efetiva das contribuições de níveis de branco (Kr + Sr residual na linha de gás) aos sinais de amostras desconhecidas. As razões 87Sr/86Sr obtidas em diferentes materiais de referência (e.g. coral moderno e o clinopiroxênio Batjberg) alcançaram precisão menor que 57 ppm ( ±0.000057 2σ SD) em comparação com os valores certificados via TIMS. A qualidade da rotina implementada é também atestada pela proximidade dos valores aceitos e obtidos para razões isotópicas estáveis. O grau de exatidão atigindo permite a identificação e o estudo de heterogeneidades isotópicas em escala micrométricas em variados minerais ricos em Sr (apatita, carbonatos, plagioclásio e clinopiroxênio) com importantes implicações para a comprensão de processos geoquímicos relevantes, particulamente processos de assimilação-fraccionamento-contaminação, heterogeneidades químicas e mistura de magmas.

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          Magma recharge, contamination and residence times revealed by in situ laser ablation isotopic analysis of feldspar in volcanic rocks

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            In situ Sr isotopic analysis by laser ablation

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              Analytical Methods for Non-Traditional Isotopes

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                Author and article information

                Contributors
                Role: ND
                Role: ND
                Role: ND
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                Journal
                bjgeo
                Brazilian Journal of Geology
                Braz. J. Geol.
                Sociedade Brasileira de Geologia
                2317-4692
                June 2016
                : 46
                : suppl 1
                : 227-243
                Affiliations
                [1 ] Universidade de São Paulo Brazil
                [2 ] Universidad de Buenos Aires Argentina
                [3 ] SENS Representações Comerciais Brazil
                Article
                S2317-48892016000700227
                10.1590/2317-488920160032093
                4905b52d-b120-4d2b-8320-2348f1bd92ff

                This work is licensed under a Creative Commons Attribution 4.0 International License.

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                SciELO Brazil

                Self URI (journal page): http://www.scielo.br/scielo.php?script=sci_serial&pid=2317-4889&lng=en
                Categories
                GEOLOGY
                GEOSCIENCES, MULTIDISCIPLINARY

                General geosciences,Geology & Mineralogy
                Laser ablation,Multiple collector inductively coupled plasma mass spectrometry,Isobaric interferences,Sr isotopic tracing,Ablação a laser,Spectrometria de massa acoplada a ICP,Interferências isobáricas,Determinações isotópicas de Sr

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