Major, Trace and REE geochemistry of Paleo-Tethys Collision-Related Granitoids from Mashhad, Iran

The study area is located in northeastern Iran (south of Mashhad). The Paleo-Tethys remnants (meta-ophiolite and meta-flysch) were intruded at three different episodes of magmatism (Triassic to Cretaceous time). 1) Dehnow-Kuhsangi hornblende biotite tonalite-granodiorite; 2) Sangbast Feldspar monzogranite; and 3) Khajehmourad biotite-muscovite leucogranite and pegmatite. They are moderately peraluminous to highly felsic peraluminous S-type granitoid. Paleo-Tethys opened in Silurian time and subduction under Turan plate was started in Late Devonian. By Late Carnian (225 m.y. ago) there was no Paleotethys left on an Iranian transect. Turan plate is abducted over Iran Plate. Only two stages of low grade regional metamorphism are exposed, Hercynian orogeny (Late Paleozoic) and Cimmerian orogeny (Jurassic time). Ophiolites constitute allochthonous sheets and they are dated by 40Ar-39Ar, 281.4 and 277.4 Ma. Dehnow to Kuhsangi tonalite-granodiorite (Early Triassic) are meta to moderately peraluminous S to I-type granitoids. They are sub-alkaline, calcic-type. They have low values of magnetic susceptibility [(1.5 to 2.5) × 10−5 SI]. Sangbast feldspar monzogranite porphyry (Late Triassic) is moderately peraluminous, K-rich calc-alkaline type. Biotite-muscovite leucogranite and late pegmatite dikes (Jurassic age) are highly felsic peraluminous S-type granitoids. They are syn-collision granite. They have low values of magnetic susceptibility [(0.1 to 0.6) × 10−5 SI]. Total REE content of tonalite-granodiorite is 101-136, in feldspar monzogranite is 221-238 and in leucogranite is 130-170 ppm. The leucogranite has the highest [(La/Yb)N = 37-124] tonalite-granodiorite has the lowest [(La/Yb)N = 7 to 22]. The Eu anomalies (Eu/Eu* = 0.55 to 1.1) is low in all of them. Tonalite-granodiorite magma has originated from a mafic source. Feldspar monzogranite has originated from a deeper source and contaminated in the crust. Biotite-muscovite leucogranite may have originated from the crustal materials.