Provenance of the Late Triassic-Early Jurassic Gano bauxite deposit in Alborz Orogen, Northern Iran: A multi-proxy geochronological approach by detrital zircon and rutile

A significant Eo-Cimmerian unconformity developed during the Late Triassic-Early Jurassic in the Alborz Orogen, Iran, resulting in the formation of bauxite on the surface of carbonate rocks. Provenance analysis of such bauxite can help understand the Tethyan tectonic evolution, but strong geochemical weathering eliminates most geochemical information for source tracing. The multiproxy geochronology method is emerging for bauxite provenance studies and remains unexplored in Iran. Here, we supplemented a multi-proxy approach (detrital zircon and rutile) with zircon trace elements, Hf isotopes, and machine learning methods to constrain the provenance of Gano bauxite in the Alborz Orogen. New data present a dominant zircon age cluster (250–200 Ma), indicating magmatic provenance from the Alborz Orogen. The Semi-supervised Random Forest algorithm indicates a transition from S-type to A-type granites as detrital zircon sources. This shift correlates with the initial collision of the Central Iran and Eurasia blocks, likely occurring during the Late Triassic Carnian stage (≥ ∼231 Ma). Two rutile age groups (1100–500 Ma and 500–400 Ma) indicate local recycled basement contributions. These two types of provenance were deposited in a foreland basin and underwent bauxitization in the Late Triassic-Early Jurassic. Zircon and rutile UPb ages in Gano bauxite show a young, near-unimodal zircon age spectrum with several older rutile age fractions, reflecting provenance fertility imbalance in the active continental margin. The application of detrital zircon alone for bauxite provenance analysis in active continental margins is constrained. Employing diverse detrital accessory minerals could better clarify the complex origins.