Two dimensional finite strain analysis of boudin bearing marble in Khalaj region using Mohr circle, south of Mashhad

The marbles of the Khalaj area constitute a part of the Mashhad metamorphic complex which was affected by three stages of deformation. Stretches of the boudins, which occurred during the first stage of the regional deformation, are measured in seven stations. The data are used for two dimensional finite strain analyses by Mohr circle. The results indicate the ellipticity of the strain ellipsoids vary between 1.05 to 1.36, and the maximum shear angle is between 4 to 20 degrees. These results are in agreement with field observations indicating dominant pure shear deformation during the first stage. This deformation is marked by generation of continuous folds and chocolate box boudins. These types of boudins were formed due to the stretching in two directions. Results of two dimensional strain analyses also show half to one time positive volume change during first stage of deformation.