Strongly peraluminous leucogranite (Ebrahim-Attar granite) as evidence for extensional tectonic regime in the Cretaceous, Sanandaj Sirjan zone, northwest Iran

Abstract The Ebrahim-Attar (EBAT) leucogranite body is intruded within the Jurassic metamorphic complex of the Ghorveh area, located in the northern part of the Sanandaj Sirjan zone (SaSZ) of northwest Iran. The granite comprises alkali feldspar, quartz, Na-rich plagioclase and to a lesser extent, muscovite and biotite. Garnet and beryl are also observed as accessory minerals. Additionally, high SiO 2 (71.4–81.0wt %) and Rb (145–440 ppm) content; low MgO ( 2 O 3 ( 87 Sr/ 86 Sr(i) and 143 Nd/ 144 Nd(i) ratios are 0.7081 ± 0.009 and 0.51220 ± 0.00005, respectively, and e Nd(t) values range from −5.8 to −1.6. These values verify that the source of this body is continental crust. The Nd model ages (T DM2 ) vary between 1.0 and 1.3 Ga and are more consistent with the juvenile basement of Pan African crust. Based on these results, we suggest that the upwelling of the hot asthenospheric mantle in the SaSZ (likely during the Neo-Tethys rollback activity) occurred after the late Cimmerian orogeny. Consequently, we suggest that this process was responsible for a thinning and heating of the continental crust, from which the SP granite was produced by the partial melting of muscovite rich in pelitic or felsic-metapelitic rocks in the northern SaSZ.