Investigating the role of pre-orogenic divergent template in exhumation of High-Pressure rocks within orogens

5-7 month : Febr - June 2022 (possible ext. for the summer)

Nowadays is widely accepted that High-Pressure (HP) rocks outcropping within internal units of orogens correspond to relics of former hyper-extended rifted domains and/or oceanic crust. HP rocks are first subducted within the lower plate of a subduction while they get exhumed in an orogenic system during subduction to collision (this is exemplified by the PTt evolution, and especially the retrograde paths, of HP rocks in the Alps). This indicates that the occurrence of exhumed HP rocks results from the way that shortening processes from subduction to collision interact with a pre-orogenic divergent template in time and space (lithospheric architecture of an oceanic basin and its surrounding continental margins). Indeed, it has been shown that the architecture of this template strongly varies and that the HP rocks are not present in all orogens worldwide. It is important to note that how these two may be genetically linked is still little understood.

The aim of this M2 project is addressed by the following two question :

–  Q1 : How the variations of the pre-orogenic divergence maturities (from aborted rifts to wide oceans) may control the development of internal orogenic units as well as the occurrence and dynamics of HP rocks ?

–  Q2 : How micro-continents as the pre-orogenic template interplay with subduction to collision processes and determine the destiny of internal units of mountain belts ?

We expect the candidate to first make a literature review of the potential link between the pre-orogenic divergent maturity template and the presence of HP rocks within mountain belts. Following this and through a modelling approach (RIFTER, a kinematic forward model, will be used), the orogenic evolution of different synthetic divergent templates will be developed (i.e. variations within the archetypal “Wilson Cycle”). Lastly, the modelling learnings will be applied to chosen analogue case-studies (e.g. Pyrenees, Alps and/or Zagros-Oman alpine-systems) which each of them shows evidence of variable divergence maturities.

The candidate will spend most of the time at the M&U office (Grenoble), a research company, in collaboration with ISTerre where will benefit from the interaction with different scientists specialized in geodynamics, structural geology, modelling and field geology.

Please do not hesitate to contact us with any question that you may have.