Petrology, geochemistry and origin of Mirabad dacitoid dykes, south of Zahedan (Southeast of Iran)

Abstract

The Mirabad dacitoid dykes exposed in the Sistan and Baluchestan province, Sistan suture zone and South of Zahedan city, near Mirabad village. These dykes, with mainly dacitoid in composition, are hosted by the Eocene flysch assemblages and the Cretaceous ophiolitic mélange. They are composed of plagioclase, quartz, hornblende and biotite minerals and the dominant texture is porphyry. The studied dykes have sharp boundary with host rocks and sometimes have metapelitic enclaves. They are calc-alkaline, meta-aluminous and I-type nature with LREE and LILE enrichment and HREE and HFSE depletion. Europium does not show any distinct anomaly reflecting the oxidation state of magma. The rocks under study have a common origin on the base of similar REE trends and spider diagram and are related to subduction environments on tectonomagmatic diagrams. Based on the Ta/Yb versus Th/Yb tectonomagmatic diagram, it is possibly that the parent magma derived from the mantle wedge above the subduction plate, which is usually affected by the fluids released from the subducted plate and their elements (including silica, potassium and sodium). The overall results indicate that the investigated dykes are synmagmatism occurred during subduction of Neothytean oceanic crust between the Lut and the Afghanblocks.

Keywords

• dacitoid dykes
• sistan suture zone
• collision
• mirabad
• zahedan