3D geometrical modelling of field data applied to regional-scale analysis of post-metamorphic deformations in the Syros blueschists (Cyclades, Greece).

Mélody Philippon and Christian Le Carlier de Veslud and Frederic Gueydan and Jean-Pierre Brun and Guillaume Caumon. ( 2011 )
in: Proc. 31st Gocad Meeting, Nancy

Abstract

3D geometrical modelling of field data is a way to quantitatively define the structural relationships between neighbouring units at regional-scale. In HP metamorphic units, it is a powerful tool that complements structural geology and classical mapping to study the processes of exhumation. For that purpose, we investigated Syros Island’s blueschists (Aegean Sea) coupling extensive fieldwork and 3D modelling. A workflow for 3D modelling structurally complex areas is proposed. This workflow uses a combination of fast draft models (interpolation of orientation data), with more complex ones when the structural context has been more documented (implicit modelling). Two kinds of geometrical relationships between a flat lying fault, so called the “Kastri basal fault”, and the foliation of the underlying units are highlighted. In the north, foliations, contacts and the Kastri basal fault are parallel (“concordant”). In the south, the Kastri basal fault contact is oblique to the underlying units (“discordant”). These flat lying faults are associated with high angle normal faults. The evolution of relationships between the units, from North to South, corresponds to a ramp-flat extensional system. In the centre of the island, sigmoid shape of the foliation reveals a kilometre-scale antiform with a N30° trending axis. Furthermore, the stretching lineations display an arcuate pattern perpendicular to the foliation-bedding trend. A 2D restoration shows that by unfolding the antiform, the stretching lineations take a mean N30° orientation, parallel to the regional stretching lineation trend. This result suggests that the arcuate stretching lineations distribution reflects a passive reorientation occurred in post metamorphic conditions. It is therefore argued that two exhumation-related deformations modes were active: (1) a distributed ductile deformation (foliation and stretching lineations pattern), (2) localized ductile to brittle deformation (ramp-flat geometry).

Download / Links

BibTeX Reference

@INPROCEEDINGS{PhilipponGM2011,
    author = { Philippon, Mélody and Le Carlier de Veslud, Christian and Gueydan, Frederic and Brun, Jean-Pierre and Caumon, Guillaume },
     title = { 3D geometrical modelling of field data applied to regional-scale analysis of post-metamorphic deformations in the Syros blueschists (Cyclades, Greece). },
 booktitle = { Proc. 31st Gocad Meeting, Nancy },
      year = { 2011 },
  abstract = { 3D geometrical modelling of field data is a way to quantitatively define the structural relationships between neighbouring units at regional-scale. In HP metamorphic units, it is a powerful tool that complements structural geology and classical mapping to study the processes of exhumation. For that purpose, we investigated Syros Island’s blueschists (Aegean Sea) coupling extensive fieldwork and 3D modelling.
A workflow for 3D modelling structurally complex areas is proposed. This workflow uses a combination of fast draft models (interpolation of orientation data), with more complex ones when the structural context has been more documented (implicit modelling). Two kinds of geometrical relationships between a flat lying fault, so called the “Kastri basal fault”, and the foliation of the underlying units are highlighted. In the north, foliations, contacts and the Kastri basal fault are parallel (“concordant”). In the south, the Kastri basal fault contact is oblique to the underlying units (“discordant”). These flat lying faults are associated with high angle normal faults. The evolution of relationships between the units, from North to South, corresponds to a ramp-flat extensional system. In the centre of the island, sigmoid shape of the foliation reveals a kilometre-scale antiform with a N30° trending axis. Furthermore, the stretching lineations display an arcuate pattern perpendicular to the foliation-bedding trend. A 2D restoration shows that by unfolding the antiform, the stretching lineations take a mean N30° orientation, parallel to the regional stretching lineation trend. This result suggests that the arcuate stretching lineations distribution reflects a passive reorientation occurred in post metamorphic conditions. It is therefore argued that two exhumation-related deformations modes were active: (1) a distributed ductile deformation (foliation and stretching lineations pattern), (2) localized ductile to brittle deformation (ramp-flat geometry). }
}