Petrography, geochemistry and tectonic setting of mafic- ultramafic intrusion in the Bafq 15th anomaly (Iron), Central Iran

Abstract

The mafic- ultramafic intrusion in the Bafq 15th anomaly (Iron) is located in 35 Km, of northwest of Bafq city, central Iran. The 15th anomaly intrusion intruded in Rizu sequence series, stratigraphically attributed to early Cambrian magmatism in west of Posht-e- Badam block. Rizu sequence series is composed of carbonate rocks of upper Neo-Proterozoic- early Cambrian. The mafic- ultramafic intrusion, includes amphibole- gabbro, apatite- gabbro, anorthosite- gabbro, amphibole- pyroxenite, apatite-pyroxenite with predominant granular texture and cumulate characteristics. The associated main mineral assemblage composed of cumulate primarily clino-pyroxene, Fe-Ti oxides, calcic plagioclase, amphibole, apatite, as well as minor olivine. The intrusion was formed from mafic magma and was differentiated from tholeiitic to weakly calc-alkaline affinity. Spider diagrams of the analyzed samples were normalized to the standard values of chondrite and primitive mantle. The REE– normalized diagrams are characterized by LILEs enrichment and HFSEs depletion and mild negative REEs trend. Different tectonic setting discriminative diagrams and elemental ratios are indicating that a subduction related affinity. The parental magma could be generated by melting of mantle peridotites (lithospheric mantle) which previously affected by subduction related fluids. The results of this research is consistent with the previous models which considered the Early Cambrian magmatism in Post-e- Badam block related to the subduction of Proto- Tethys oceanic crust beneath central Iran in north of Gondwana land.