Middle Eocene magmatism in the Khur region (Lut Block, Eastern Iran): implications for petrogenesis and tectonic setting

Abstract

The Khur region is located in the Late Mesozoic-Cenozoic volcanic-plutonic rocks of the Lut Block, eastern Iran. There are several outcrops of subvolcanic rocks in the region which occur mainly as dike (granitoid and mafic dikes) and stock (monzonite porphyry). Volcanic rocks (basaltic andesites, andesites, trachyandesites, dacites and rhyodacites) are also abundant and cover pyroclastic rocks. U–Pb zircon ages indicate that granitic-dioritic dikes and monzonite porphyries were emplaced at 44.97 to 40.86 Ma and 41.11 Ma, respectively. Granitoid dikes are high-K calc-alkaline and metaluminous and geochemically belong to the I-type granitoids. Monzonite porphyries show I-type (and rarely A-type) signatures, with typical enrichments in alkalis, Zr and Ce, high FeOt/(FeOt+MgO) ratio and depletion in Sr and Nb. Primitive magmas of dikes, stocks and acidic volcanic rocks have formed in the lower crust and have undergone different degrees of AFC, while primitive magmas of mafic volcanic rocks have formed in the mantle and have presumably been modified by melts/fluids. Moreover, a syn to post-collision-related zone is responsible for the high magmatic rate during the Middle Eocene in the Lut Block.