Understanding the magma-crust interaction: the role of the northern Gondwana margin in the genesis and evolution of the Jurassic Alvand plutonic complex (Sanandaj-Sirjan Zone, NW Iran)

Abstract

This work investigates the petrogenesis of the main magmatic rocks of the Jurassic Alvand plutonic complex, located in the northern sector of the Sanandaj-Sirjan Zone of Iran. The Alvand complex is made up of a wide range of rocks spanning gabbro to leucogranites, containing a diversified range of enclaves, from mafic-to felsic- and surmicaceous-type. Here we present new textural characterization together with mineral, whole rock and Sr–Nd isotope chemistry of the main magmatic lithotypes. We integrated this new data with the available ones to understand the petrogenesis of the Alvand magmas and their interaction with the Ediacaran-Cambrian crystalline basement. A legacy of the Peri-Gondwanan crust is evident in Alvand felsic rocks. The whole rock chemistry, the Sr–Nd isotope ratios and assimilation-fractional crystallization numerical models indicate their genesis partly through differentiation via fractional crystallization from the coeval Alvand gabbros coupled with a concurrent and significative mass-addition of material from the Cadomian basement. At a wider scale, this work also provides new insights into the understanding the role of the continental crust in the buildup of transcrustal magmatic systems and therefore to a better comprehension of crust growth process driven by intense magma-crust interaction events.