Structural Interpretation of Fractures and Veins in the Jabal Akhdar Dome, Oman Mountains

Gomez-Rivas, Enrique ¹; Bons, Paul D.¹; Koehn, Daniel ²; Urai, Janos ³; Virgo, Simon ³; Arndt, Max ³; Laurich, Ben ³; Zeeb, Conny ⁴; Stark, Lena ¹; Blum, Philipp ⁴
(1)Department of Geosciences, Eberhard Karls University of Tübingen, Tübingen, Germany. (2) Tectonophysics, University of Mainz, Mainz, Germany. (3) Structural Geology, Tectonics and Geomechanics, RWTH Aachen University, Aachen, Germany. (4) Institute for Applied Geosciences (AGW), Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany.

Fracture and vein networks in the Mesozoic succession of the Oman Mountains are a clear example of dynamic fracture opening and sealing. As some of the Early Cretaceous formations in neighbouring areas host large oil reserves, unravelling the evolution of fracture and vein networks in Jabal Akhdar is important to understand fracture distributions in these oil fields.

Hence, we carried out a detailed structural study of fractures and veins in the exhumed carbonates of the Jabal Akhdar dome to identify all tectonic events that took place in this area. We have collected many 3D measurements of fracture and vein orientations, opening directions, striations on exposed planes, stretched crystals and fibres in veins, as well as stylolite orientations. Overprinting relationships between the various structures enabled us to better constrain the tectonic evolution of the area.

Building on previous studies (e.g. Hilgers et al., 2006) our new data show that strike-slip deformation played an important role in the area, more than hitherto recognised. The strike-slip movement is recorded by subhorizontal striations on oblique slip and dip-slip normal faults and by abundant sets of conjugate en-echelon veins and steep stylolites. Many of these veins are confined to particular layers, which indicates the importance of mechanical stratigraphy in the limestone succession. In particular the E-W to NW-SE compression that can be observed throughout the Jabal Akhdar dome is compatible with fault patterns observed in seismic profiles through oil fields in Oman and Abu Dhabi (e.g. Filbrandt, 2006). This compression event can be correlated with an oblique collision related to the the passage of the Indian continent along the Arabian Plate during the Santonian-Campanian. This means that the Jabal Akhdar dome forms an excellent natural laboratory to investigate the small to medium scale structures that cannot be observed in seismic profiles.

AAPG Search and Discovery Article #90135©2011 AAPG International Conference and Exhibition, Milan, Italy, 23-26 October 2011.