Sr-isotope microsampling of feldspar phenocrysts: application to magma system analysis

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Project objective

The aim of the project is to reconstruct magma chamber processes such as magma recharge and assimilation by using Sr-isotopes in-site analysis in zoned feldspar phenocrysts. The study will involve high-precision micro drilling combined with Thermal Ionization Mass Spectrometry. Chemical zoning patterns in the crystals to be investigated have been well documented using the electron microprobe during the PhD of the applicant. Using the micro-drill allows to control zone sampling width and shape, and thus the best possible spatial (and thus time-) resolution. Furthermore, the Sr isotopic compositions in crystals directly reflect the melt composition, whereas the chemical composition also depends on temperature, pressure, crystal chemistry , etc. This complementary information will be combined for the interpretation in terms of magmatic processes. The Parinacota volcano (north Chile) represents a long-lived calco-alkaline magmatic system. Sr isotope compositions of individual plagioclase zones in various samples should confirm the role of two mafic end-members suggested by the trace element study. In samples without evidence for recharge, it should show also the extent of assimilation. The Laacher See Volcano (Germany) is an inverted zoned phonolitic magma chamber. Sr isotope should help specifying more precisely the origin of the recognized different types of zoned sanidine phenocrysts and the assimilation processes. Possible cyclic basanitic magma recharge can also be tested.

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Participants

• UNIVERSITY OF DURHAM · DURHAMCoordinatorUnited Kingdom

Links

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