Geochronology, Radiogenic Isotope Geochemistry, and Petrogenesis of Sangbast Paleo-Tethys Monzogranite, Mashhad, Iran

The study area is located in northeastern iran (south of mashhad). palco-tethys ocean openedduring silur ian time and subduction under turan plate was started in late devon ian. by late triassic (225ma) there was no paleo-tethys left on an iranian transect, therefore turan plate obducted over iran plate .two stages of low grade regional metamorphism are exposed, that are related to hercynian (late paleo zoic)and cimmerian (jurassic) orogenies. the paleo-tethys renmants (meta-ophiolite and meta-flysch) wereintruded by sangbast monzogranite. chemically, monzogranite is moderately peraluminous s-type granitoid.it has low values of magnetic susceptibility [(5 to 11x 10'5 si] therefore it is class ified as belonging to theilmenite-series of reduced type granitoids. monzogranite is characterized by strong light rare earth element(lree) enrichment and less low heavy ree (hree) . all samples have very small negative eu anomalies(eu/eu* = 0.62 to 0.88). total ree content of monzogranite is between 212-481 ppm. the result of u-pbzircon age dating of monzogranite is 201 .3 ± 3.6 ma (upper triassic, rhaetian time). the initial 87sr/86srand 143nd;i44nd ratios for monzogranite is (0.706776 and 0.512219) when recalculated to an age of201 ma,consistent with the new radiometric. the initial 87sr;86sr and 143nd/144nd ratios for slate is (0.720613 and0.51160 i) respectively when recalculated to an age of 20 i ma, consistent with the new radiometric results .initial end isotope values for monzogranite is -3.13 and the slate is -15.19. based on radiogenic isotop ic dataand ree monzogranite magma originated either from lower continental crust which was very different fromslate or it is originated from mantle and contaminated in continental crust during ascending