Longitudinal strike-slip-faults in oceanic rifting: a mesostructural study from western to southeastern Iceland

Mesostructural analysis carried out in several localities of western, southern-central and southeastern Iceland shows an unexpectedly frequent occurrence of strike-slip faults parallel to, or lying at relatively small angles with, the axis of rifting. Some faults can be interpreted in terms of shear parallel to the rifts, whereas others form conjugate systems referable to rift-parallel compression. Axial shear can be explained by the accommodation of differences in the directions of tectonic extension between different segments of the axial rift system and subordinately by lateral rift-parallel. displacements between the major lithospheric plates. Axial compression may be attributable to rift-oblique transform shear or to mantle transport parallel to the spreading axis compensating local deficiencies in mantle upwelling. The data regard 1974 fault surfaces, mainly small-scale.