Paleomagnetic arguments for block rotations along the Arakapas fault (Cyprus)

Abstract

Paleomagnetic data from the sheeted dike complex north of the Arakapas fault reveal significant internal rotations. The north-south-trending dikes have remanent magnetization directions close to the well-known westerly paleomagnetic direction of the Troodos massif, whereas the east-west-trending dikes near the Arakapas fault have northerly remanent magnetization directions. The paleomagnetic data are in agreement with the apparent clockwise rotation of the dikes. Contrary to recent geological analyses which postulate that the pattern of dike trends is due to dike injection into a sigmoidal stress field along a sinistral transform fault, the paleomagnetic results indicate clockwise rotations about vertical axes in response to a dextral shear. In addition to the rotations around vertical axes, small rotations around subhorizontal axes are inferred from the paleomagnetic data for tilted dikes. Thus, these data reinforce the vertical intrusion hypothesis.

Direct evidence for dynamic magma supply fossilized in the lower oceanic crust of the Troodos ophiolite

“…The location of the Solea graben was originally constrained by the orientation of normal faults, opposing tilt of sheeted dikes, and rotated blocks of lava flow [Hurst et al, 1994]. Paleomagnetic study of the gabbroic suite [Granot et al, 2006] confirmed the location of the suspected paleospreading Solea axis and showed a clockwise rotation of remanence directions in the inside corner north of the Arakapas Transform fault ( Figure S1 in the auxiliary material), similar to the rotations shown for the overlying sheeted dikes [Allerton, 1989;Bonhommet et al, 1988], pillow lavas and hydrothermal sediments (umbers) [Morris et al, 1990]. …”

“…Paleomagnetic studies of the upper crust and overlying sedimentary sequence [e.g., Morris et al, 2006] showed that the entire ophiolite had rotated by nearly 90°anti-clockwise during the emplacement (late Cretaceous to early Eocene), leading to an expected remanent magnetization direction of 273°/38°(a 95 = 6.5°). Any deviation of remanent magnetization from this direction reflects pre-emplacement accretion-related rotations [e.g., Allerton and Vine, 1987;Bonhommet et al, 1988;Ebert et al, 2010;MacLeod et al, 1990]. Although the gabbros studied here lack independent structural information, remanence directions together with the assumed N-S trend of rotation axis (parallels the Solea axis) are sufficient to correct for tectonic rotations.…”

The oceanic crust in 3D: Paleomagnetic reconstruction in the Troodos ophiolite gabbro

“…On the other hand, the sheeted dikes show 60-80° rotation at the same sense (Fig. 4b) [20,22]. This means that in the IC terrain the lower crust deforms at the same sense as the upper crust, but the amount of rotation is smaller.…”

“…Maximum deformation, with ~90° cumulative clockwise rotation, is evident close to the transform (i.e., sheeted dike trending E-W). The degree of rotation gradually declines with increasing distance from the Arakapas transform reaching zero 6 km to the north [20][21][22][23].…”

“…Several paleomagnetic surveys conducted in Troodos have investigated the magnetization of the upper pillow lavas (e.g., [19,26]) as well as the magnetization of the sheeted dike complex (e.g., [21,22,27,28]). The entire complex had rotated by nearly 90° anti-clockwise during the late Cretaceous -early Eocene interval and recent uplift of the Troodos massif resulted in radial tilts about Mt.…”