Original paper

Geochemistry, Sr-Nd isotope data and petrogenesis of the Marziyan granitoid, Sanandaj–Sirjan Zone, western Iran

Darvishi, E.; Khalili, M.; Toksoy-Köksal, F.; Köksal, S.; Beavers, R.

Abstract

The Marziyan granitoid is part of the widespread granitoid bodies in the Sanandaj-Sirjan Zone. It intruded Mesozoic regional metamorphic rocks of this belt and is composed of leucogranite and subordinate granite. The mineralogy of the granitoid is dominated by quartz, K-feldspar, plagioclase, biotite, muscovite, garnet, tourmaline and accessory apatite, zircon and ilmenite. The peraluminous nature of these rocks is manifested by high molar A/CNK ratio (> 1.1), and the presence of garnet and minor sillimanite. Strong enrichment in alkalies and depletion in high field strength elements as well as high initial 87Sr/86Sr ratios (> 0.71) and low initial εNd(t) values (–0.8 to –3.7) suggest that the melt was derived from a metapelitic source. Part of the heat required for the formation of the Marziyan granitic magma was supplied by shear heating imposed by regional tectonic forces. The granitoids exhibit a high-K and calc-alkaline nature and show features typical of syn-collisional magmatic intrusions. Based on geological, mineralogical and geochemical data, we suggest that magma intrusion took place at mid to upper crustal levels possibly under vapour-absent conditions during the collision of the Afro-Arabian continental plate with the Central Iranian microplate.

Keywords

granitoidsanandaj-sirjan zoneiransyn-collisionperaluminousmarziyan