Rb–Sr and Sm–Nd isotopic compositions, U-Pb Age and Petrogenesis of Khajeh Mourad Paleo-Tethys Leucogranite, Mashhad, Iran

Abstract

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<br><br>age of Khajeh Mourad biotite muscovite leucogranite is 205.9 ± 4.1 Ma (Late Triassic, Rhaetian).<br><br>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 (&lt; 0.35), therefore they are classified as belonging to the ilmenite-series (reduced type). The total REEs content of biotite muscovite leucogranite is between TREEs = 130-176 and aplite is very low Total REEs = 50.79. They have small negative Eu anomalies (Eu/Eu*= 0.52 to 0.76). <br><br>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