Diabase Dikes Emplacement in the Oman Ophiolite: A Magnetic Fabric Study with Reference to Geochemistry
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 Kl parallel to flow line. Secondary fabrics, mainly with Kl parallel to dike pole, are more likely to occur in thick (≥1.5 m) dikes with high susceptibility and MORB composition. Flow lines appear quite dispersed with an overall tendency toward vertical flow. Dikes of the end of emplacement. This shear could be a signature of oblique spreading during the accretion of the Omani oceanic crust MORB type composition show a distinct obliquity of their flow plane relative to dike margins, suggesting that the dikes were horizontally sheared at the end of emplacement. This shear could be a signature of oblique spreading during the accretion of the Omani oceanic crust.
KeywordsFlow Line Secondary Fabric Magnetic Foliation Dextral Shear Oman Ophiolite
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