Abstract:

Large carbonate or anhydrite inclusions are embedded in many salt bodies (so-called rafts, floaters or stringers) and these respond to the movements of the salt in a variety of ways, including displacement, folding and fracturing. The movement and deformation of those embedded carbonate or anhydrite bodies is a process which is not fully understand yet. We presented numerical models of the deformation of salt body with embedded stringers using a case study from the South Oman Salt Basin. We investigated by Abaqus package (finite element models) how differential displacement of the top salt surface induces salt flow and the associated deformation of brittle stringers (including both brittle and viscous material properties) in a compressive environment. The simplified model offers a practical method to investigate complex stringer motion and deformation. Models suggest that brittle stringers can break very soon after the onset of salt tectonics. The compression can make brittle stringer bending and thrusting. Models suggest that viscous stringers have folding and extension deformation. Results also show the internal structure of salt body and stringer fracturing or deformation is strongly dominated by the geometry or material properties of models.

Introduction

Large rock inclusions are embedded in many salt bodies and these inclusions have different ways of deformation and displacement. The process of salt tectonics has a strong impact on the deformations of the inclusions and there are different typical deformation styles such as displacement, folding, fracture and thrusting. It is of great importance to understand the deformation and displacement of inclusions because of some critical reasons (Li et al., 2012). In the past 30 years, a large number of numerical studies about the deformation of salt structures have been performed (Woidt and Neugebauer, 1980; Last, 1988; Schultz-Ela et al., 1993; Podladchikov, 1993; Poliakov et al., 1993; Van Keken et al., 1993; Daudré and Cloetingh, 1994; Koyi, 1996; Koyi, 1998; Kaus and Podladchikov, 2001; Ismail-Zadeh et al., 2001; Schultz-Ela and Walsh, 2002; Gemmer et al., 2004; Ings and Beaumont, 2010; Fuchs et al., 2011; Abe and Urai, 2012). A few numerical studies have been done regarding the deformation and displacement of inclusions embedded in salt as relatively homogeneous material. Koyi, (2001) and Chemia et al. (2008, 2009) modeled the whole range of the process. Koyi (2001) used physical models and Chemia et al. (2008, 2009) used numerical models to study the whole process of entrainment of anhydrite blocks by a salt structure and their later descent within the structure. Koyi (2001) also used numerical models to quantify the descent rate of entrained anhydrite blocks within a salt diapir. Chemia et al. (2008), Chemia and Koyi (2008) and Chemia et al. (2009) systematically studied the effects of viscosity (Newtonian and non-linear), position of the anhydrite layer, and different rising rate of salt diapirs in connection to entrainment and descent of anhydrite layers/blocks within a salt structure. Burchardt et al. (2011; 2012a, b) used extensive numerical modeling to study the influence of size/aspect ratio and orientation of the denser blocks on the sinking rate and mode.

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