Geochemistry and tectonomagmatic setting of Late Cretaceous magmatism (the Bazman batholith) in southern margin of the Lut Block

The Bazman batholith crops out in the south of the Lut block and north of the Makran Zone, southeastern Iran. This batholith includes granite to intermediate granitoids (quartz-diorite, quartzmonzonite and granodiorite) and minor gabbros intruded by sparse leucocratic dykes. U–Pb zircon geochronology of a granodiorite indicates an emplacement age of 75 ± 1 Ma. The gabbros, intermediate granitoids and dykes have low-K tholeiitic, high-K calc-alkaline and shoshonitic affinities, respectively. The A/CNK and A/NK ratios indicate that intermediate granitoids and dykes are metaluminous. In chondrite-normalized diagrams, fractionated REE patterns are characterized by (La/Yb) N of 7.5 to 9.8 and (La/Sm) N of 3.2 to 4.6. In primitive mantle normalized diagrams, the high field strength elements (HFSEs) negative anomaly is revealed by pronounced troughs in Nb, Ta and Ti. The low (Na2O+K2O)/(MgO+FeO+TiO2), K2O/Na2O, and Al2O3/(MgO+FeO+TiO2) ratios besides elevated CaO/Al2O3 and CaO+FeO+MgO+TiO2 contents suggest an amphibolitic source for the intermediate granitoids. Furthermore, their REE compositions compared to theoretical model melts suggest generation from 10 to 30% dehydration melting of amphibolite without stable amphibole in the residuum. However, the major element and REE compositions of leucocratic dykes are inconsistent with an amphibolitic source; they are instead analogous to highly differentiated melts produced by fractionation of some major and REE-enriched accessory minerals. Tectonically, the Bazman batholith documents igneous activity in the Late Cretaceous active continental margin of southern Eurasia. This margin records subduction of an oceanic basin which was created by pre- Early Cretaceous rifting and now covered by the modern Jaz Murian depression.