Rb-Sr and Sm-Nd Isotopic Compositions, U-Pb Age and Petrogenesis of Khajeh Mourad Paleo-Tethys Leucogranite, Mashhad, Iran

Biotite-muscovite leucogranite and associated pegmatite intruded meta-ophiolite and meta-flysch (the remnants of Paleo-Tethys) during collision of Turan plate with Iran plate. Four types of pegmatite dykes, crosscutting biotite muscovite leucogranite, are identified. The results of U-Pb zircon age of Khajeh Mourad biotite muscovite leucogranite is 205. 9 ± 4. 1 Ma (Late Triassic, Rhaetian). Chemically, biotite muscovite leucogranite and aplite granite are peraluminous S-type pluton. Magnetic susceptibility of biotite muscovite leucogranite and aplite granite are between than 0-5 × 10-5 and the ratio of ferric to ferrous ratio (< 0. 35), therefore they are classified as belonging to the ilmenite-series (reduced type). The total REE content of biotite muscovite leucogranite is between TREE = 130-176 and aplite is very low Total REE = 50. 79. They have small negative Eu anomalies (Eu/Eu*= 0. 52 to 0. 76). The initial 87Sr/86Sr and (143Nd/144Nd) i was recalculated to an age of 205 Ma. Initial 87Sr/86Sr ratios for B-M leucogranite and aplite are 0. 708161-0. 709853. The (143Nd/144Nd) i isotope composition for B-M leucogranite 0. 512214, aplite dykes 0. 512024. Initial ε Nd isotope values for B-M leucogranite -6. 48 and aplite dykes is -6. 83. These values could be considered as representative of continental crust-derived magmas. The ratios of Rb/Sr = 1-1. 3 and CaO/Na2O» 0. 3 of biotite-muscovite leucogranite indicate that the source rock had a composition between meta-pelite and meta-psammite.