Quantitative microstructural analysis of mylonites formed during Alpine tectonics in the western Mediterranean realm

Gaetano Ortolano* (Corresponding Author), Eugionio Fazio, Roberto Visalli, G. Ian Alsop, Mario Pagano, R Cirrincione

*Corresponding author for this work

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

Quantitative microstructural investigations involving new GIS-based tools are applied to three different types of mylonitic rocks. These techniques enable mineral shape distribution maps to be produced, thereby allowing the nature and relative percentage of the weakening vs. hardening layers, as well as their kinematics, to be obtained within a statistically meaningful dataset. Selected rock-types are derived from shearing associated with the meso-Alpine strike-slip tectonics of the western Mediterranean realm, which since the Paleocene has involved, skarn, migmatitic paragneiss and tonalites. These rocks belong to a deep-seated portion of the original southern European Variscan chain known as the Calabrian Pelortani Orogen. Microstructural maps reveal porphyroclastic domains, represented alternatively by feldspar, amphibole, pyroxene or scapolite, that can be distinguished from weakening phase areas, characterised by quartz, biotite plus quartz, or alternatively by calcite when the weakening layer is controlled predominantly by skarns. Image elaboration of porphyroclastic domains was employed to estimate the dominant shear-type, with Rigid Grain Analysis, indicating a pure shear component of 66–68% for the mylonitic tonalites; 62–66% for the mylonitic paragneisses; and 58–62% for the mylonitic skarn. Grain boundary mapping of the quartz-rich domains also permits an estimate of shear strain rate, which ranges from 1.14*10−12 (1/s) for mylonitic paragneiss to 5.91*10−12 (1/s), for mylonitic tonalite, and is in accord with high strain zones in natural settings. Finally, our results opened up new perspectives in the interpretation of the kinematics and rheology of this exhumed sector of the southern European Variscan chain reflecting the deep-seated meso-Alpine strike-slip tectonics of the western Mediterranean realm.

Original languageEnglish
Article number103956
JournalJournal of Structural Geology
Volume131
Early online date12 Dec 2019
DOIs
Publication statusPublished - Feb 2020

Keywords

  • strike slip tectonics
  • geomatics
  • Gis-based tools
  • Calabrian peloritani orogen
  • Palmi shear zone
  • Strike slip tectonics
  • Geomatics
  • METAMORPHIC EVOLUTION
  • RAY MAP ANALYZER
  • SHEAR ZONE
  • THIN-SECTION
  • ASPROMONTE MASSIF
  • SOUTHERN CALABRIA
  • VORTICITY ANALYSIS
  • RHODOPE CORE COMPLEX
  • FLOW LAWS
  • CALABRIA-PELORITANI TERRANE

ASJC Scopus subject areas

  • Geology

Fingerprint Dive into the research topics of 'Quantitative microstructural analysis of mylonites formed during Alpine tectonics in the western Mediterranean realm'. Together they form a unique fingerprint.

  • Cite this