• Andrea Festa, Dipartimento di Scienze della Terra, Università di Torino, Italy
  • Date: October, 21, 2014 12:00 am
  • Place: Sala d'Actes del Institut de Ciències de la Terra Jaume Almera(ICTJA)
  • Location: C/ Solé i Sabarís s/n, Barcelona

Mélanges represent disrupted and chaotic rock units including sedimentary, magmatic and metamorphic rocks (often as exotic blocks) mixed by stratal disruption and tectonic, diapiric and/or sedimentary processes. Although mélanges may characterize diverse geodynamic environments of formation, they are commonly associated with subduction and obduction of oceanic crust, continental collision, and intra-continental deformation. In these cases, mélanges are cogenetic with deformation and uplift of ophiolites, emplacement of thrust and nappe sheets, onset and evolution of foreland basins, and submarine landslides (olistostromes). They are also involved in the general dynamics and mechanical stability of the accretionary and orogenic wedges, participating in (or being the product of) the redistribution of earth materials through the processes of offscraping, underplating, mass-transport movements, subduction channels (flow mélanges), and mud diapirism. In this complex scenario, it is not uncommon that a mélange in any region may be identified and described with different names, and varying interpretations may be developed for its evolution as a result of different backgrounds of the investigating geoscientists and different tools of investigation.

This short seminar proposes a discussion on: (i) the evolving mélange concept and the relationships between mélange types and their geodynamic setting of formation, (ii) the contribution of mass-transport versus tectonic deformation processes at the onset of mélange formation and throughout the evolution of different mélange types, (iii) the nature of the continuum and transition from broken formations to tectonic mélanges, and (iv) criteria helpful for distinguishing mélanges formed by different processes and their superposition (polygenetic mélanges).

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