Spreading structure of the Troodos ophiolite, Cyprus: Some paleomagnetic constraints

It has been suggested that grabens on the northern flank of the Troodos ophiolite formed by listric faulting in an oceanic environment and represent axial valleys fossilized by ridge-jumping. This paleomagnetic survey of the Solea graben was carried out to constrain the structural interpretation.

An analysis was devised which restores both the dikes sampled to vertical and the primary remanent magnetizations to a previously derived, structurally corrected, remanent magnetization direction. Typically, two solutions for the original dike orientation and the pole and angle of net rotation are obtained for each dike sampled. These solutions can be separated if a locally consistent original dike strike is assumed. Reasons are discussed for the selection of the solution that gives an original northwesterly dike strike.

Results are consistent with a graben: rotations are up to 78° at the sites studied. Rotation vectors are subhorizontal and subparallel to the original dike strike, suggestive of an axial process for the development of the structure. However, on the basis of field observations, an alternative mode of origin is proposed, invoking ephemeral extreme upper crustal extension by listric faulting on the west flank of an intermediate- to fast-spreading axis, the grabens being formed by antithetic faulting.