Strain and crystallographic fabric pattern in a folded calcite vein: the dependence on initial fabric

  • Peter J. Hudleston
  • Hari B. Srivastava
Chapter

Abstract

Buckle folding of single competent rock layers is typically accommodated by tangential longitudinal strain (TLS), which involves layerparallel stretching in the outer arc of a fold and layer-parallel shortening in the inner arc, with a neutral surface separating the two. We describe a folded fibrous calcite vein in which the primary crystallographic fabric, with c-axes perpendicular to the vein walls, allows only for layer shortening by twinning on 0112; twinning cannot lead to layer stretching. As there are no other deformation mechanisms that allowed for stretching in the outer arc, the folding must have occurred without the development of a neutral surface in the layer. Intensity of twinning increases from the outer edge of the folded vein to the inner edge, suggesting that a neutral surface existed at the outer edge. This is supported by approximate measurements of twinning strain that show a strain gradient consistent with TLS, and that indicate also about 10% layer-parallel shortening prior to fold growth.

Keywords

Outer Edge Fold Axis Twin Plane Neutral Surface Vein Wall 
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Copyright information

© Springer Science+Business Media Dordrecht 1997

Authors and Affiliations

  • Peter J. Hudleston
    • 1
  • Hari B. Srivastava
    • 2
  1. 1.Department of Geology and GeophysicsUniversity of MinnesotaMinneapolisUSA
  2. 2.Department of GeologyBanaras Hindu UniversityVaranasiIndia

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