A Numerical Kinematic Model for Deformation Near a Ridge-Transform Intersection in the Troodos ophiolite, Cyprus Based on Gabbro Paleomagnetic Rotations and Sheeted Dike Orientations

The Troodos ophiolite in Cyprus provides a unique opportunity to examine spatially varying patterns of deformation near a ridge-transform intersection. The paleo-inner corner is confined by the EW-striking Arakapas transform fault and the NS-striking Solea graben. Rocks within the inner corner are primarily sheeted dikes and gabbros from the midcrust. Motion along the transform fault is generally agreed to be dextral, based on two datasets: (1) clockwise rotations determined from paleomagnetic data primarily from the gabbroic complex, and (2) the changing orientation of sheeted dikes from NS-striking and parallel to the ridge, to E-striking and perpendicular to the ridge, with increasing proximity to the transform fault. Both datasets are consistent with the progressive rotation of material due to drag along the Arakapas fault. We augment the existing paleomagnetic data with our own analyses from ~25 sites in the gabbroic complex. Our results, combined with those from other local paleomagnetic studies, are compared to the Troodos mean vector to determine vertical axis rotations from each site. These data demonstrate that rotations vary throughout the inner corner; in general, rotation magnitudes increase from 5° to 40° with distance from the Solea Graben and rotations are larger near the transform. We develop numerical kinematic models for the inner corner by fitting a variety of elementary functions to the vertical axis rotation data. These functions approximate how structural features evolve over time in a spatially heterogeneous simple shear field. This field of rotations is then used to predict the original orientation of sheeted dikes; we find that in most cases sheeted dikes return to a NNW strike. This consistent initial strike can be interpreted as reflecting: (1) heterogeneous stress directions near the ridge-transform intersection, which are consistent with dynamic modeling results, or (2) a non-orthogonal ridge-transform intersection between the Solea Graben and the Arakapas fault. Although other workers often call upon the latter interpretation, we favor the former based on sheeted dike orientations in the ophiolite. On the outer corner side of the Solea Graben, dikes are consistently N-striking, as opposed to NNW-striking, a pattern that is also predicted by many dynamic model results. Our results highlight the importance of linking insights from dynamic modeling with those from field data.