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Raman spectroscopy of laser-induced oxidation of titanomagnetites

Authors

  • Michael Bauer,

    1. Department of Earth and Environmental Sciences, Ludwig-Maximilians-Universität München, 80333 Munich, Germany
    2. Center for NanoScience (CeNS), 80799 Munich, Germany
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  • Polina Davydovskaya,

    1. Department of Earth and Environmental Sciences, Ludwig-Maximilians-Universität München, 80333 Munich, Germany
    2. Center for NanoScience (CeNS), 80799 Munich, Germany
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  • Marek Janko,

    1. Department of Earth and Environmental Sciences, Ludwig-Maximilians-Universität München, 80333 Munich, Germany
    2. Center for NanoScience (CeNS), 80799 Munich, Germany
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  • Melanie Kaliwoda,

    1. Mineralogical State Collection, LMU, 80333 Munich, Germany
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  • Nikolai Petersen,

    1. Department of Earth and Environmental Sciences, Ludwig-Maximilians-Universität München, 80333 Munich, Germany
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  • Stuart Gilder,

    1. Department of Earth and Environmental Sciences, Ludwig-Maximilians-Universität München, 80333 Munich, Germany
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  • Robert W. Stark

    Corresponding author
    1. Center for NanoScience (CeNS), 80799 Munich, Germany
    2. FB Material-und Geowissenschaften, TU Darmstadt, 64287 Darmstadt, Germany
    3. Center of Smart Interfaces, TU Darmstadt, 64287 Darmstadt, Germany
    • Center of Smart Interfaces, Petersenstraße 32, 64287 Darmstadt, Germany.
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Abstract

Titanomagnetites are important carriers of magnetic remanence in nature and can track redox conditions in magma. The titanium concentration in magnetite bears heavily on its magnetic properties, such as saturation moment and Curie temperature. On land and in the deep ocean, however, these minerals are prone to alteration which can mask the primary magnetic signals they once recorded. Thus, it is essential to characterize the cation composition and oxidation state of titanomagnetites that record the paleomagnetic field. Raman spectroscopy provides a unique tool for both purposes. Nonetheless, the heat generated by the excitation laser can itself induce oxidation. We show that the laser power threshold to produce oxidation decreases with increasing titanium content. With confocal Raman spectroscopy and magnetic force microscopy (MFM) on natural and synthetic titanomagnetites, a non-destructive Raman imaging protocol was established. We applied this protocol to map out the composition and magnetization state within a single ex-solved titanomagnetite grain in a deep-sea basalt. Copyright © 2011 John Wiley & Sons, Ltd.

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