Development of shear zone-related lozenges in foliated rocks

Carlos Ponce, Elena Druguet, Jordi Carreras

Research output: Contribution to journalArticleResearchpeer-review

27 Citations (Scopus)

Abstract

Tectonic lozenges are elongate bodies bounded by relatively more deformed rocks. The focus of this study is on the 2-D structure of tectonic lozenges developed during ductile shear in rocks with a pre-existing mechanical anisotropy. On the basis of a detailed analysis of shear zones in foliated rocks from the Cap de Creus area (Variscan of the eastern Pyrenees), five mechanisms to explain the development of different types of lozenges in foliated rocks are suggested. These mechanisms are explained on the basis of the orientation of the previous foliation relative to the bulk shearing direction. It is shown that the prevailing mechanism does not majorly depend on the bulk kinematics but on the angular relationship between the pre-existing foliation and the bulk kinematic axes, and on shear zone interaction. This has implications on the use of lozenge shapes in tectonic interpretations. The fact that there is a wide range of initial orientations, propagation modes and coalescence types implies that the final lozenge geometry is not univocally related neither to the type of strain nor to the kinematic regime. © 2012.
Original languageEnglish
Pages (from-to)176-186
JournalJournal of Structural Geology
Volume50
DOIs
Publication statusPublished - 1 May 2013

Keywords

  • Anastomosing shear zones
  • Cap de Creus
  • Lozenge
  • Planar anisotropy
  • Shear zone interaction

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