Petrography, geochemistry and tectonic setting of mafic dyke swarms of Zrigan granitoid, north of Bafq (Central Iran)

Mafic dyke swarms of the Zarigan granitoid in the north of Bafq have intruded the Lower Cambrian volcanic-sedimentary sequence of central Iran. These dykes are lithologically classified as gabbro-diorite and alkali gabbro. The alkaline gabbros are younger and penetrate higher horizons. Geochemically, gabbro-diorites have a tholeiitic to transitional nature with enrichment of LILE, HREE and depletion of Nb and Ta elements. By contrast, alkali gabbros have the sodic alkaline nature, exhibiting Nb-Ta enrichment and high LREE/HREE ratio. Gabbro-diorite magmas are derived from partial melting of sub-continental lithospheric mantle affected by subduction components in equilibrium with spinel lherzolite. On the other hand, the alkali gabbros originate from greater depth and lower partial melting of enriched asthenospheric mantle in equilibrium with garnet lherzolite. These dykes are formed in an intra-arc extension setting associated with subduction of the continental margin. Geometry and mechanism of motion of Posht-e-Badam and Kuh Banan basement faults caused an anticlockwise rotation, crustal fracturing, lithospheric thinning, and stenosphere upwelling of these two faults bounded block.