POEM-POligEnetic Mélanges: anatomy, significance and societal impact

Coordinatore: Prof. Michele Marroni, Dipartimento di Scienze della Terra, Università di Pisa.

Ente finanziatore: PRIN - Bando 2020

Budget: 457 080 €.

Partners: Prof.ssa Laura Crispini (responsabile unità ricerca Università di Genova), Prof. Andrea Festa (responsabile unità ricerca Università di Torino), Prof.ssa Iole Spala (responsabile unità ricerca Università di Milano)

Durata: marzo 2022- marzo 2025

Mélanges represent a significant component of most orogenic belts around the world. The distinction among processes, tectonic setting and depth of melanges formation represents a significant aspect to detail the tectonic evolution of these orogenic belts. However, during the multistage evolution of orogenic belts, the complex interaction and superposition of different processes, mechanisms and metamorphic recrystallization overprint and rework the primary (original) block-in-matrix fabric of tectonic, sedimentary and (mud and serpentinite) diapiric mélanges, forming the so-called “polygenetic mélanges”. Not surprinsingly, then, contrasting interpretations and models have been proposed for mélanges, their orgins, and consequently for the tectonic evolution of orogenic belts. For the first time, a multidisciplinary and multi-scale approach (geological mapping, structural, stratigraphic, sedimentological, paleontological, petrological, mineralogical and geochemical integrated investigations associeted to quantitative geodinamic modelling) will be adopted to improve significantly the understanding of “polygenetic melanges” formed in different tectonic settings and at different depths and P-T-t conditions during a complete orogenic cycle (from rifting to subduction, collision and exhumation). We will focus on the mélanges of the Alps and Apennines belts where notable examples of different types of mélange originated at different structural levels and depths are well preserved. Expected results are aimed at providing a modern view on the (i) the mode and significance of “polygenetic melange” formation, (ii) the nature of the continuum of their disruption and mixing from shallower to deeper structural levels (i.e., from non-metamorphic up to HP-UHP metamorphic conditions), and (iii) the criteria useful to differentiate their genetic processes. We will finally deliver a new methodological protocol for their distinction and interpretation as fundamental markers of tectonic events in global orogenic belts. Within this frame, the societal impact will be explored as well, regarding the role of the mélanges in geological hazards (e.g., earthquakes and landslides) and their environmental impact in the production of raw material and in their bearing on human health hazard (as asbestos dispersion and potentially toxic elements bioavailability).