Pure shear to simple shear-dominated transpression during the Eburnean major D2 deformation, Daléma sedimentary basin, eastern Senegal - Archive ouverte HAL Access content directly
Journal Articles International Geology Review Year : 2013

Pure shear to simple shear-dominated transpression during the Eburnean major D2 deformation, Daléma sedimentary basin, eastern Senegal

(1) , (2)
1
2
Tahar Aifa
  • Function : Author
  • PersonId : 840707

Abstract

Field studies in the Palaeoproterozoïc Daléma basin, Kédougou-Kéniéba Inlier, reveal that the main tectonic feature comprises alternating large shear zones relatively well-separated by weakly deformed surrounding rock domains. Analysis of the various structures in relation to this major D2 phase of Eburnean deformation indicates partitioning of sinistral transpressive deformation between domains of dominant transcurrent and dominant compressive deformation. Foliation is mostly oblique to subvertical and trending 0-30◦ N, but locally is subhorizontal in some thrust-motion shear zones. Foliation planes of shear zones contain a superimposed subhorizontal stretching lineation which in places cross-cuts a steeply plunging stretching lineation which is clearly expressed in the metasedimentary rocks of weakly deformed surrounding domains. In the weakly deformed domains, the subhorizontal lineation is absent, whereas the oblique to subvertical lineation is more fully developed. Finite strain analyses of samples from surrounding both weakly deformed and shearing domains, using finite strain ratio and the Fry method, indicate flattened ellipsoid fabrics. However, the orientation of the long axis (X) of the finite strain ellipsoid is horizontal in the shear zones and oblique within the weakly deformed domains. Exceptionally, samples from some thrust zones indicate a finite strain ellipsoid in triaxial constriction fabrics with a subhorizontal long axis (X). In addition, the analysis of the strain orientation starting from semi-ductile and brittle structures indicates that a WNE-ESE (130◦ N to 110◦ N) orientation of strain shortening axis occurred during the Eburnean D2 deformation.
Not file

Dates and versions

insu-00841000 , version 1 (03-07-2013)

Identifiers

Cite

Moussa Dabo, Tahar Aifa. Pure shear to simple shear-dominated transpression during the Eburnean major D2 deformation, Daléma sedimentary basin, eastern Senegal. International Geology Review, 2013, 55 (9), pp.1073-1086. ⟨10.1080/00206814.2012.760711⟩. ⟨insu-00841000⟩
99 View
0 Download

Altmetric

Share

Gmail Facebook Twitter LinkedIn More