OSL-thermochronometry of feldspar from the KTB borehole, Germany

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

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

56 Scopus citations

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°Ckm-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 (<0.3 Ma, 40-70°C range), or for studying equally recent and rapid transient cooling in active orogens (<0.3 Ma, >200°CMa-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 (<0.3 Ma) information on the thermal structure and history of hydrothermal fields, nuclear waste repositories and hydrocarbon reservoirs.

Original languageEnglish
Pages (from-to)232-243
Number of pages12
JournalEarth and Planetary Science Letters
Volume423
DOIs
StatePublished - 1 Aug 2015

Funding

FundersFunder number
ETH-Zürich
Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung200021-127127, PZ00P2-148191/1
Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung
Nederlandse Organisatie voor Wetenschappelijk OnderzoekVENI-863.13.023
Nederlandse Organisatie voor Wetenschappelijk Onderzoek

    Keywords

    • Feldspar IRSL
    • Geothermal gradient
    • In-situ palaeothermometry
    • KTB drillhole
    • Low-temperature thermochronology
    • OSL-thermochronology

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