GEOLOGY AND PETROLOGY OF TWO DISTINCT TYPES OF GRANITOIDS, EASTERN NAJMABAD, GHONABAD, IRAN

Counter-clockwise rotation of the Lut Block since the Triassic caused strike-slip faulting and folding in eastern Najmabad, eastern Iran. Regional sub-greenschist to greenschist facies metamorphism associated with Jurassic-Cretaceous deformation has turned Jurassic shales and sandstones into slates and quartzites. An east-west trending biotite granodiorite porphyry pluton, 26×4 km² in size, intruded these Jurassic slates and quartzites. Based on mineralogy and low values of magnetic susceptibility [(5 to 11) × 10^-5 SI], this granodiorite is classified as belonging to the ilmenite-series of reduced S-type type granitoids. Chemically it is met-aluminous, with relative enrichment in LILE = Rb, Ba, Zr, Th, Hf, K and LREE, and depletion in Sr, P, Ti and HREE. Based on REE content and low (La/Yb)_N = 7-11.5, this pluton originated from melting of continental crust during the Jurassic-Cretaceous orogeny that caused regional metamorphism. Sub-volcanic monzonitic porphyries formed as younger stocks intruded into the granodiorite. Based on mineralogy and high values of magnetic susceptibility [(500) × 10-5 SI], these are classified as belonging to the magnetite-series of oxidized I-type granitoids. At the Hired Au-Sn prospect two distinct S and I type granitoids were also identified (Karimpour et al., 2009 . Petrochemistry of the Reduced, Ilmenite-Series Granitoid Intrusion Related to the Hired Gold-Tin Prospect (Basiran), Eastern Iran. J. of Applied Sciences 9: 226-236. At Hired the initial ⁸⁷Sr/⁸⁶Sr of S-type is 0.706200 and the I-type is 0.705074. Based on Rb-Sr and REE data, the S-type originated from the continental crust, but I-type did not.