0000000000667099
AUTHOR
Sven Erik Meyer
A strike-slip core complex from the Najd fault system, Arabian shield
Metamorphic core complexes are usually thought to be associated with regional crustal extension and crustal thinning, where deep crustal material is exhumed along gently dipping normal shear zones oblique to the regional extension direction. We present a new mechanism whereby metamorphic core complexes can be exhumed along crustal-scale strike-slip fault systems that accommodated crustal shortening. The Qazaz metamorphic dome in Saudi Arabia was exhumed along a gently dipping jog in a crustal-scale vertical strike-slip fault zone that caused more than 25 km of exhumation of lower crustal rocks by 30 km of lateral motion. Subsequently, the complex was transected by a branch of the strike-sli…
Multistage Tectonism and Metamorphism During Gondwana Collision: Baladiyah Complex, Saudi Arabia
Field evidence from the Baladiyah complex in the northern part of the Arabian^Nubian Shield of Saudi Arabia indicates several erosional unconformities separating different high- and medium-grade metasedimentary sequences. This suggests that the collision between East and West Gondwana involved several cycles of exhumation and burial, providing a unique opportunity to study the multiple stages of this orogeny. A mineral equilibria approach and thermodynamic modeling are used to place constraints on the formation conditions of each of these cycles. It is shown that the complex is characterized by three regional metamorphic events followed by a fourth metamorphic event related to shear heating…
Mimicking shear zones: An example from Wadi Filk, Jordan
Abstract Ductile shear zones can develop in at least two ways: (1) a nucleus can grow laterally by free propagation into undeformed host rock, like most faults or joints; (2) the zone may nucleate and grow on or in a planar discontinuity and mimick its orientation. Most small-scale ductile shear zones are mimicking zones, but large-scale ductile shear zones could be free-propagating. The Wadi Filk mylonite zone in Jordan is a two km long, ten meter wide mylonite zone flanked by ultramylonite zones, developed in undeformed Neoproterozoic porphyritic monzogranite. Since mineral and major element composition of mylonite and monzogranite are identical, the structure seems to have formed by free…
Development of branching brittle and ductile shear zones: A numerical study
Continental collision zones are usually associated with large-scale strike-slip shear zones. In most cases these shear zones are complex and consist of multiple strands, varying in width, length, and total displacement. Here we present 2-D numerical models to simulate the formation of such shear zones at different depth levels within the crust, under either brittle (frictional/plastic) or ductile conditions. Localization of shear zones is initiated by a material contrast (heterogeneity) of the material parameters. We systematically test the rate of strain-weakening in brittle and in ductile regimes to understand its influence on the development of shear zone networks. Our simulations sugges…