Reconstructing the Source and Growth of the Makran Accretionary Complex: Constraints From Detrital Zircon U‐Pb Geochronology

Abstract

AbstractWe have used U‐Pb zircon ages and Hf isotopic compositions for detrital zircons from Eocene and Cretaceous‐Triassic sedimentary rocks of the Makran accretionary complex (MAC, Iran) to understand the source and growth of the MAC during Mesozoic and Cenozoic time. The Cenozoic sandstones reveal the main age distribution from Paleocene to Eocene with a peak at 54 Ma and show εHf(t) values of −47.7 to +12.1. Our compiled U‐Pb‐Hf data from both the Urumieh‐Dokhtar Magmatic Belt magmatic zircons and the Paleogene Makran detrital zircons reveal that both Makran continental arc and Urumieh‐Dokhtar Magmatic Belt are important suppliers of the Makran detrital zircons. Mesozoic zircons show dominant peaks at 94–91 (Late Cretaceous), 151 (Late Jurassic), and 229 Ma (Triassic). Detrital zircons with peaks at 91 and 151 Ma with εHf(t) values of −42.5 to +15.2 can be supplied by the erosion of Makran ophiolitic rocks, although negative εHf(t) values indicate some Makran detrital zircons came from reworking of the magmatic rocks of the Sanandaj‐Sirjan zone of Iran. Late Cretaceous detrital zircons (~94–91 Ma) were also supplied from erosion of the nascent Makran arc. Middle to Late Jurassic zircons (163–151 Ma) can also come from erosion of the rifting‐related magmatic rocks within the Bajgan‐Durkan complex, although zircon U‐Pb ages show middle Jurassic ages (170–165 Ma) for the Bajgan‐Durkan magmatic rocks. Triassic zircons with εHf(t) values between −17 and +6.9 probably were supplied by the Bajgan‐Durkan complex and/or by Central Iran magmatic rocks. Paleozoic detrital zircons show major peaks at 330 (Carboniferous) and 460 Ma (Ordovician). Their εHf(t) values range from −51 to +18.2 and −9.5 to +4.6, respectively. Carboniferous detrital zircons may have come from the erosion of alkaline gabbros and A‐type granites reported from the NW, NE, SE, and central segments of the Sanandaj‐Sirjan zone and/or may have been supplied from reworking of Carboniferous strata of the Bajgan‐Durkan complex. Late Neoproterozoic‐Early Cambrian detrital zircons with εHf(t) values from −42.9 to +32.4 are suggested to be derived from the Cadomian magmatic rocks of Iran and Anatolia. The pre‐Cadomian detrital zircons with εHf(t) values of −28.9 to +27.5 are consistent with derivation from magmatic rocks of the Arabian‐Nubian Shield. Archean (2.5 Ga) and Paleoproterozoic (2.4–1.8 Ga) detrital zircons probably come from the Afro‐Arabian Craton and Saharan Metacraton. New data from detrital zircons imply that the MAC evolved from Triassic to Eocene and incorporated all orogenic elements including the continental lithosphere, oceanic crust, and its nearby continental arcs during its evolutionary cycle.