Fossil ridge-transform intersection in the Troodos ophiolite: New perspectives from rock magnetism in the gabbro suite and fracture mechanics analysis

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Abstract

[1] The “missing link” in the comprehensive view of the ridge-transform intersection (RTI) frozen in Troodos is that portion of the extinct spreading axis between the Solea graben and the fossil Arakapas transform. Directional indicators of magma flow verified by paleomagnetic tests along with tectonic indicators permit tracing the extinct spreading axis through the gabbro suite at the continuation of the Solea graben axis. These indicators of axial deformation include measurements of the anisotropy of magnetic susceptibility (AMS) and petrofabric determinations in the gabbro, dikes, major normal faults, and fabric of mantle rocks. The inferred axis is curved as it approaches the fossil transform. The sense of curvature is in agreement with dextral slip along the fossil transform, assuming curvature has resulted from transform-induced shear stresses. Fracture mechanics analysis predicts the control on the axis shape by the ratio between driving stresses of spreading (SH) and resistance for sliding along the fossil transform (T). Accordingly, the curved shape of the spreading axis frozen in Troodos indicates T/SH ∼ 0.1–0.2, whereas for straight axis and orthogonal RTI, the analysis predicts T/SH < 0.01. These results suggest that the fossil curvature reflects a strong transform relative to curvature-free RTIs. A strong Arakapas transform is also in agreement with previous evidence of diffused deformation north of the transform, such as block rotation and sigmoidal structure of dikes and faults.

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