Deciphering the Tectono-Metamorphic Evolution of the Monte Rosa Nappe : a Combined Petrological, Structural and Numerical Modelling Study

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Joshua Vaughan-Hammon, 1st October 2021, Institute of Earth Sciences (ISTE)

Mountain building processes have shaped the present-day European Alps. Here, tectonic processes such as collision, subduction and exhumation of the Earth’s crust has resulted in changes in both the structure and chemistry of the rocks involved. Chemical changes in rocks are largely due to changes in temperature and pressure (metamorphism), whereby pressure is commonly assumed to be a function of the depth of burial, e.g. during subduction. Tectono-metamorphic observations from the Monte Rosa nappe (European Alps) have challenged the assumption that metamorphic pressure is solely due to depth of burial.

Variable pressures are recorded in the Monte Rosa nappe (for the same metamorphic event), and we propose that these disparities are a consequence of local pressure variations during:

  1. periods of high differential stresses, and/or
  2. volumetric changes due to metamorphism.

A multi-disciplinary approach is presented in this thesis, that combines chemical and structural analysis from portions of the Monte Rosa nappe that are now exposed due to recent climate change, as well as state-of-the-art numerical modelling that simulates the large-scale geological evolution of the European Alps.

The results of these investigations continue to highlight that local pressure variations likely existed during the Alpine evolution within the Monte Rosa nappe, and that a better understanding of the interplay between metamorphic and tectonic processes is essential to ultimately unravel the tectono-metamorphic history of the Alps.

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