Petrography and geochemistry of mafic to acidic dikes in Siahjakuk, south of Zahedan, southeastern Iran

: Siahjakuk dikes are located in southeast and south of Zahedan in Sistan Suture Zone. In this area Eocene flysch-like rocks were intruded by numerous Oligocene dikes and some small stocks. The flysch is also intruded by Oligocene granitoid as batholith in southern part of the area. The flysch is mainly and locally altered phyllite, shale, sandstone and siltstone. The dikes and flysch layers are mainly NW in strike and there are also dikes with N-S and NE trends. Some dikes occur as conjugate dikes. The dikes sharply follow the faults and shear structures. The dikes are leucocratic to melanocratic in color and mafic to felsic in composition. They are meladiorite, diorite, granodiorite, gronodiorite porphyry, diorite porphyry (andesite), dacite and rhyolite. The dikes are mainly high K calc-alkaline, shoshonitic and metaluminous and probably belong to post-collision magmatic arcs. The minor and rare earth elements which are normalized to the primitive mantle and the chondrite, respectively, show that LREE and LILE are enriched than LREE and HESE, respectively which is a feature of subduction related igneous rocks in volcanic arcs. Regard to geochemical studies, for the Siahjakuk dikes could assume an enriched, heterogeneous and metasomatized lithospheric source. The mafic and intermediate dikes were formed from melts that derived from partial melting of mafic rocks such as basalt and amphibolite and the acidic dikes are related to melts that derived from partial melting of crust sediments such as greywacke.

کلیدواژه ها:

Conjugate dikes ، Whole rock chemistry ، High-K calc-alkaline ، Post-collisional ، Sistan suture zone