Introduction

The Lut Desert, located in southeastern Iran, represents one of the most remarkable hyper-arid regions on Earth, characterized by extreme temperatures, minimal precipitation, and diverse geomorphological features such as kaluts, hammadas, and vast sand seas (Rig-e Yalan). Due to its unique geomorphic and climatic conditions, the Lut Desert provides an exceptional natural laboratory for studying sedimentological and geochemical processes in arid environments. The desert’s surface materials are shaped by the interplay between aeolian, fluvial, and playa processes that operate under intense evaporation and limited weathering.
Despite extensive geomorphological research in the Lut Desert, relatively few studies have focused on the geochemical composition, provenance, and tectonic setting of its surface sediments. Understanding these parameters is crucial for reconstructing source lithologies, sediment transport pathways, and regional tectonic evolution. The present study aims to investigate the mineralogical and geochemical characteristics of surficial sediments in different geomorphic units of the Lut Desert, including kaluts, intermediate hammadas, and the Rig-e Yalan sand sea, to identify their provenance, weathering intensity, and tectonic setting.
 
2.Materials and Methods
Representative sediment samples were collected from multiple geomorphological units across the Lut Desert, covering the kalut area in the west, the intermediate hammada zone, and the extensive sand sea of Rig-e Yalan in the east. Field observations focused on grain size, sorting, rounding, and sediment color, while laboratory analyses determined the mineralogical and geochemical composition.
Mineralogical studies were conducted using optical microscopy and X-ray diffraction (XRD), revealing the dominant minerals present in the sediments. Major and trace element concentrations were measured using X-ray fluorescence (XRF) and Inductively Coupled Plasma (ICP) techniques at certified laboratories. The obtained data were processed statistically and plotted on various geochemical discrimination diagrams to interpret provenance and tectonic environment.
Key geochemical ratios such as Al₂O₃/TiO₂, TiO₂-Zr, Na₂O/K₂O, and SiO₂/Al₂O₃ were used to infer source rock composition and weathering intensity. Provenance and tectonic setting discrimination diagrams, including SiO₂/Al₂O₃ vs. Fe₂O₃+MgO, La/Th vs. Hf, and Ti/Zr vs. La/Sc, were applied to evaluate the dominant lithologic sources and the tectonic environment of sediment derivation.
 

Results and Discussion

Field observations indicated significant textural variation across geomorphic units. Sediments from the kalut areas contained poorly sorted particles with subangular grains and a mixture of quartz, lithic fragments, and carbonate debris, suggesting limited transport and reworking. In contrast, samples from Rig-e Yalan displayed well-sorted, highly rounded quartz grains, reflecting prolonged aeolian transport and mechanical abrasion. These textural differences illustrate the combined effects of aeolian deflation, fluvial reworking, and episodic playa sedimentation on sediment distribution in the Lut Desert.
Mineralogical analysis confirmed that quartz, feldspars, carbonates, and lithic fragments are the dominant detrital components, while heavy minerals such as magnetite, ilmenite, and zircon occur in minor amounts. The abundance of quartz, coupled with depletion in unstable minerals, indicates a high degree of sedimentary maturity, particularly in the aeolian deposits of the Rig-e Yalan. Geochemical analyses revealed that SiO₂, Al₂O₃, Fe₂O₃, and CaO are the major oxides, with SiO₂ content ranging between 62–85 wt%, indicating quartz-rich compositions. Elevated Fe₂O₃ and TiO₂ contents in kalut sediments suggest contributions from volcanic and mafic lithologies. The Al₂O₃/TiO₂ ratios (ranging between 10 and 25) and TiO₂–Zr relationships suggest derivation predominantly from felsic to intermediate igneous rocks such as granites, rhyolites, and volcanic tuffs. The Na₂O/K₂O ratio displays relatively low values, implying advanced chemical weathering and feldspar depletion, consistent with strong mechanical disintegration and limited chemical alteration under hyper-arid conditions. Variations in SiO₂/Al₂O₃ and Fe₂O₃+MgO indicate compositional maturity differences among the three geomorphic zones, with the highest maturity observed in the eastern sand sea.
Provenance discrimination diagrams (e.g., Ti/Zr vs. La/Sc and La/Th vs. Hf) suggest that the majority of samples plot within the field of felsic volcanic and plutonic source rocks, with minor influence from recycled sedimentary materials. The spatial geochemical variability implies that the western and central parts of the Lut Desert receive detritus mainly from igneous and metamorphic rocks of the Kerman magmatic arc, whereas the eastern portions are affected by long-distance aeolian transport and recycling of older alluvial and playa sediments. Tectonic discrimination diagrams (e.g., Fe₂O₃+MgO vs. TiO₂ and Th–Sc–Zr/10) place most samples within the fields of Active Continental Margin (ACM) and Continental Arc Settings (CAS), consistent with the geotectonic framework of Central Iran. This correlation reflects sediment derivation from uplifted continental crust and volcanic arc terranes associated with Neogene to Quaternary magmatism and tectonic reactivation along the Lut block margins.
 

Conclusion

The integrated sedimentological and geochemical data reveal that the surficial deposits of the Lut Desert are products of complex interactions between aeolian, fluvial, and playa processes. The sediments are compositionally immature in the western kalut and hammada regions but become progressively mature toward the eastern Rig-e Yalan due to prolonged aeolian reworking. The dominance of quartz and the depletion of feldspars and mafic minerals indicate advanced mechanical weathering under extreme aridity.
Geochemical ratios and element distributions confirm that the sediments were derived mainly from felsic to intermediate igneous sources (granites and volcanic tuffs) with minor sedimentary recycling. Tectonic setting analysis demonstrates that these deposits originated within an Active Continental Margin environment, consistent with the tectono-magmatic evolution of Central Iran.
Overall, the findings provide new insights into the provenance, weathering, and tectonic controls on sediment composition in one of the driest and most dynamic desert systems of the world. This study contributes valuable baseline data for future research on geomorphological evolution, sediment transport, and paleoenvironmental reconstruction in arid regions of Iran.