Diabase dikes emplacement in the Oman Ophiolite: a magnetic fabric study with reference to geochemistry

Abstract

The anisotropy of magnetic susceptibility, coupled with geochemical identification of magma sources, has been investigated in 360 samples from 67 basaltic dikes of the sheeted dike complex of the Oman ophiolite. Two thirds of the analysed dikes have MORB affinities, while the others, previously related to island arc setting, show REE patterns and trace elements evolution more in agreement with an off-axis ridge magmatism and an interaction between magma and ultramafic country rocks. Only half of the dikes yield primary flow fabrics with a minimum magnetic axis K3 close to dike pole and a maximum axis K1 parallel to flow line. Secondary fabrics, mainly with K1 parallel to dike pole, are more likely to occur in thick (≥1.5m) dikes with high susceptibility and MORB composition. Flow lines appear quite dispersed with an overall tendency toward vertical flow. There is evidence of shear which could be a signature of oblique spreading during the accretion of the Omani oceanic crust. -from Authors