Geochemistry and petrogenesis of Koudakan granitoid body (east of Lut block-Central Iran)

Koudakan Granitoid located in 100 km South of Birjand and 18 km North of Ghaleh-Zari mine in eastern Iran. It belong to the Lut Block volcanic–plutonic belt. These intrusive rocks (Eocene-Oligocene) petrogaphicaly composed of Diorite, Monzodiorite, Quartzmonzodiorite, Tonalite, Porphyritic Tonalite, Granodiorite, Granite and Porphyritic Granite. Plutonic rocks in this area have features typical of high-K calc-alkaline to shoshonite series, metaluminous and belong to I-type Granitoides. Enrichment in LILE rather than HFSE (RbN/YN: 38.12-124.93), negative anomalies of Nb and Ti and enrichment in LREE rather than HREE (LaN/YbN: 6.74-12.03) in all of samples are important evidences for the formation of this rocks in a subduction related magmatic belt. Positive anomalies of Pb and K indicate the involvement of continental crust in evolution of parental magma. Parallel trend of the samples in spider diagrams show that they are co-genetic. Elements ratios and Different discrimination diagrams show the formation of this rocks in an active continental margin with about less than 45 Km crustal thickness in per-collision steps. Parental magma has been generated by low degree partial melting (less than 5%) of an enriched peridotite in mantle wedge (Spinel lherzolite.).