A càrrec de>/b>: Dr. A. Mohammadi
Geological Institute, ETH Zurich, Suïssa

Dia: Dijous 19 de gener
Hora: 12:00 h
Lloc: Sala d'actes de l'Institut Jaume Almera


A multidisciplinary provenance study, including sandstone framework, heavy mineral analysis, in situ U-Pb dating of detrital zircon, and Hf isotopic ratio analysis of dated zircons, was undertaken on Late Cretaceous– Miocene deep-marine turbiditic and deltaic sandstones of Makran accretionary wedge, SE Iran, to determine their sedimentary provenance and tectonic setting. Sandstone framework modes reveal both magmatic arc rocks as a source of Late Cretaceous–Oligocene detritus and recycling of Miocene sandstones. Heavy mineral assemblages, Cr-spinel, and blue amphibole indicate ophi-olite and high-pressure–low-temperature metamorphic rocks (blueschists) as a supplementary provenance. In total, 2931 laser-ablation–inductively coupled plasma–mass spectrometry (ICP-MS) U-Pb detrital zircon ages on 21 sandstone samples yielded three major age peaks at ca. 167 Ma, 88.7 Ma, and 48.9 Ma. Also, 241 in situ Hf isotope analyses of dated zircons provide evidence for dominantly igneous source rocks. Two main detrital zircon ages are identified: (1) abundant Middle Jurassic grains with Hf isotopic compositions of continental crust, suggesting a rifting-related magmatic provenance; and (2) Late Cretaceous–Eocene grains with Hf isotopic compositions of continental crust and nondepleted mantle, suggesting a continental magmatic arc provenance. This change in provenance is attributed to the Late Cretaceous convergence between Ara-bia and Eurasia.