OSL-thermochronometry of feldspar from the KTB borehole, Germany

Benny Guralnik, Mayank Jain, Frédéric Herman, Christina Ankjærgaard, Andrew Sean Murray, Pierre G. Valla, Frank Preusser, Georgina E. King, Reuven Chen, Sally E. Lowick, Myung Ho Kook, Edward J. Rhodes

    Research output: Contribution to journalJournal articleResearchpeer-review

    Abstract

    The reconstruction of thermal histories of rocks (thermochronometry) is a fundamental tool both in Earth science and in geological exploration. However, few methods are currently capable of resolving the low-temperature thermal evolution of the upper ∼2 km of the Earth's crust. Here we introduce a new thermochronometer based on the infrared stimulated luminescence (IRSL) from feldspar, and validate the extrapolation of its response to artificial radiation and heat in the laboratory to natural environmental conditions. Specifically, we present a new detailed Na-feldspar IRSL thermochronology from a well-documented thermally-stable crustal environment at the German Continental Deep Drilling Program (KTB). There, the natural luminescence of Na-feldspar extracted from twelve borehole samples (0.1–2.3 km depth, corresponding to 10–70 °C) can be either (i) predicted within uncertainties from the current geothermal gradient, or (ii) inverted into a geothermal palaeogradient of 29±2 °C km−1, integrating natural thermal conditions over the last ∼65 ka. The demonstrated ability to invert a depth–luminescence dataset into a meaningful geothermal palaeogradient opens new venues for reconstructing recent ambient temperatures of the shallow crust (200 °C Ma−1 range). Although Na-feldspar IRSL is prone to field saturation in colder or slower environments, the method's primary relevance appears to be for borehole and tunnel studies, where it may offer remarkably recent (
    Original languageEnglish
    JournalEarth and Planetary Science Letters
    Volume423
    Pages (from-to)232-243
    Number of pages12
    ISSN0012-821X
    DOIs
    Publication statusPublished - 2015

    Keywords

    • low-temperature thermochronology
    • OSL-thermochronology
    • feldspar IRSL
    • KTB drillhole
    • geothermal gradient
    • in-situ palaeothermometry

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