Arc magmatism witnessed by detrital zircon U-Pb geochronology, Hf isotopes and provenance analysis of Late Cretaceous-Miocene sandstones of onshore western Makran (SE Iran)

Abstract

The present work aims to contribute to the Cenozoic tectonic setting of the western part of the Makran Accretionary Wedge in SE Iran. We determine the provenance of both deep marine turbiditic and deltaic-shelf Late Cretaceous-Miocene sandstones, describe the sandstone modal framework and heavy minerals and report a new geochronological and isotopic study including 2307 detrital zircons U-Pb ages and 204 in-situ Hf isotopic analyses. Modal sandstone framework compositions indicate that a magmatic arc and recycled accreted sediments were the main sources of Eocene-Oligocene and Miocene sandstones. Cr-spinel and heavy mineral assemblages indicate ultramafic rocks, likely ophiolitic mantle, as a subsidiary source. Detrital zircon U-Pb ages cluster in five main age groups: (1) Neoproterozoic grains suggesting a continental crust provenance within the Central Iran blocks, (2) Jurassic grains with Hf isotopic compositions of continental crust, suggesting a rifting related magmatic provenance, (3) Late Cretaceous and (4) Eocene grains, with Hf isotopic compositions typical of continental crust and non-depleted mantle, suggesting a continental magmatic arc provenance, and (5) Early Miocene grains. The new U-Pb age and Hf isotopic ratios correspond to those obtained in the east Iranian Makran. They fit tectonic reconstructions with Middle Jurassic intracontinental rift, Early Cretaceous to Eocene subduction below Central Iran forming a continental arc to the north of Makran and closure of the related oceanic in the Paleogene. Erosional products of the corresponding magmatic arc are found in the Makran Basin. Our data disprove that provenance characteristics of the Makran sedimentary rocks are consistent with derivation from the Himalayan sources.