Fission track and numerical thermal modeling of differential exhumation of the Glarus thrust plane (Switzerland)

M. K. Rahn, B. Grasemann

    Veröffentlichungen: Beitrag in FachzeitschriftArtikelPeer Reviewed

    Abstract

    Geometry and differences in metamorphic grade along the Glarus thrust (external European Alps) can be explained by a restoration of the hanging wall some 10 km toward the south, and back rotation of the thrust plane into a ramp-flat-ramp geometry. The apatite fission track (FT) age pattern from the area suggests that isotherms were parallel to the thrust plane during cooling of the rocks along the thrust plane below the apatite closure temperature. Two forward modeling programs that both produce time-temperature paths are used to constrain the thermal and structural evolution of differential exhumation along the Glarus thrust. (a) A two-dimensional finite-difference thermal model is used to examine differential exhumation of the thrust plane, starting from an assumed horizontal position of the middle part of the Glarus thrust at some 10 Ma when parallel to the paleo-isotherms. Five locations in the crustal section corresponding to locations on a final horizontal and vertical sampling traverse record their time-temperature (t-T) history during exhumation along particle paths. The near-surface temperature distribution is strongly influenced by the development of a simplified step-like topographic relief, which causes all modeled samples to reach the surface at the end of the modeled time period. (b) The calculated t-T paths of these five modeled samples were used to forward model apatite FT data based on an existing annealing model. By comparison between synthetically generated FT data and actual measured FT samples, the exhumation history of the Glarus Alps was evaluated with respect to its thermal and temporal brackets. Several parameters such as the location of the rotation point, the thermal gradient, and the topography have significant influence on model results. Best-fit models produce results that are consistent with independent geological and geophysical information.

    OriginalspracheEnglisch
    Seiten (von - bis)245-259
    Seitenumfang15
    FachzeitschriftEarth and Planetary Science Letters
    Jahrgang169
    Ausgabenummer3-4
    DOIs
    PublikationsstatusVeröffentlicht - 15 Juni 1999

    ÖFOS 2012

    • 105106 Geodynamik

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