The Siah Cheshmeh-Khoy-Misho-Tabriz fault (NW Iran) is a cryptic neotethys suture: evidence from detrital zircon geochronology, Hf isotopes, and provenance analysis

ABSTRACT

Provenance analysis including sandstone modal compositions, heavy mineral assemblages, and LA-ICP-MS U-Pb dating with in-situ Hf isotopic compositions of detrital zircons defines two types of Late Cretaceous-Eocene turbiditic sequences separated by the Siah Cheshmeh-Khoy-Misho-Tabriz Fault in the Azerbaijan Province, Northwest Iran: (1) Volcaniclastic turbidites to the southwest and (2) terrigenous turbidites to the northeast. The first appearance of Cr-spinel in Upper Cretaceous sandstones of both sequences indicates the erosion of ophiolites at that time. The southwestern volcaniclastic sandstones contain few Late Triassic and dominantly Late Cretaceous zircon grains whose Hf isotopic compositions suggest a continental magmatic arc provenance. In the northeastern terrigenous sandstones, detrital zircon U-Pb ages cluster in five main age groups from Paleoproterozoic-Neoproterozoic with Hf isotopic compositions typical of continental crust to Late Cretaceous-Palaeocene zircon grains with Hf isotopic compositions similar to those of the southwest turbidites. The provenance characteristics define, along with sedimentary structures, two separate basins, a marginal basin to the northeast, and a deep oceanic basin to the southwest. We conclude that the Siah Cheshmeh-Khoy-Misho-Tabriz Fault overprints a boundary between two lithospheres separated by ophiolite outcrops; therefore, the Siah Cheshmeh-Khoy-Misho-Tabriz Fault is a reworked suture. The Cretaceous arc, witnessed by clastic material, has been largely eroded and/or subducted.

KEYWORDS:

• Tabriz fault
• Khoy ophiolite (NW Iran)
• turbidites
• detrital zircon
• Hf isotopes
• neotethys suture

Acknowledgments

This study was funded by the Forschungsreserven/Burg J.-P (grant no. 2-78159-99) and the Swiss National Fund, grants no. 2-77644-09 and 2-77979-14. We thank the Geological Survey of Iran and Mohammad Faridi for logistic support during fieldwork. We sincerely thank Anna Lechmann for help in field and laboratory work. Thanks are due to Isabella Premoli-Silva for fossil determination, Yannick Buret for help in Hf isotopes processing, Karsten Kunze for his assistance on CL and BSC imaging, and Remy Lüchinger for the thin sections.

Disclosure statement

No potential conflict of interest was reported by the authors.

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Funding

This work was supported by the Swiss National Fund [grants no. 2-77644-09,grants no. 2-77979-14.]; Forschungsreserven/Burg J.-P [grant no. 2-78159-99].