Oblique sinistral transpression in the Arabian shield: the timing and kinematics of a Neoproterozoic suture zone

The Hulayfah-Ad Dafinah-Ruwah fault zone is a belt of highly strained rocks that extends in a broad curve across the northeastern Arabian shield. It i s a subvertical shear zone, 5-30 km wide and over 600 km long, and is inter preted as a zone of oblique sinistral transpression that forms the suture b etween the Afif terrane and the Asir-Jiddah-Hijaz-Hulayfah superterrane. Av ailable data suggest that the terranes began to converge sometime after 720 Ma, were in active contact at about 680 Ma, and were in place, with suturi ng complete, by 630 Ma. The fault zone was affected by sinistral horizontal and local vertical shear, and simultaneous flattening and fault-zone-paral lel extension. Structures include sinistral sense-of-shear indicators, L-S tectonite, and coaxial stretching lineations and fold axes. The stretching lineations switch from subhorizontal to subvertical along the fault zone in dicating significant Variation in finite strain consistent with an origin b y oblique transpression. The sense of shear on the fault zone suggests sini stral trajectories for the converging terranes, although extrapolating the shear sense of the suture zone to infer far-held motion must be done with c aution. The amalgamation model derived from the chronologic and structural data for the fault zone modifies an existing model of terrane amalgamation and clarifies the definitions of two deformational events (the Nabitah orog eny and the Najd fault system) that are widely represented in the Arabian s hield. (C) 2001 Elsevier Science B.V. All rights reserved.