چكيده لاتين
The study area is located south of Ashin and west of Anarak. In this research, alluvial fan sediments of the Ashin region, covering an area of 200 square kilometers, were investigated to examine the sedimentological characteristics and provenance of magnetic-susceptible deposits through an integrated approach involving satellite imagery analysis, remote sensing studies, grain-size analysis, heavy mineral separation, and petrographic investigations. Initially, a thorough examination of preliminary geological maps, satellite imagery, and remote sensing studies was conducted to identify potential sampling areas within the alluvial deposits. Using satellite data from Landsat 9 and Sentinel-2 and applying various remote sensing techniques, promising zones for the concentration of mineral-bearing components such as hematite, magnetite, Fe²⁺, and Fe³⁺ were identified within the Ashin alluvial fan. Key band ratios including B6/B5, (B4 + B6)/B5, B5/(B7 + B2), and (B9/B8) × (B2/B7) played a significant role in distinguishing spectral differences of target minerals, leading to the extraction of 28 promising locations. Additionally, the preparation of geological, topographical, and drainage maps provided a better understanding of the structural characteristics, sedimentary dynamics, and sediment transport pathways within the fan system. The integration of satellite image interpretations and field studies revealed a fan depositional environment comprising three sub-environments: upper, middle, and distal fan zones, as well as clay flat environments typical of arid and semi-arid regions. The alluvial deposits are mainly sourced from the Ashin ophiolitic masses. During two field campaigns, 29 alluvial sediment samples were collected. Laboratory analyses included dry-sieve grain-size analysis and separation of magnetic heavy minerals. The grain-size analysis was conducted using mesh sizes ranging from 5 to 230. The granulometric and sorting data indicated a wide range of grain sizes, from gravelly sand to fine sand. Both positive and negative skewness reflected the influence of low- and high-energy depositional environments, while kurtosis values less than 3 pointed to particle size dispersion. The examination of magnetic minerals revealed a higher abundance of magnetite and hematite across different parts of the fan. Magnetic separation and quantitative assessment of the mineral content showed that samples A14, A12, A24, and A13 had the highest concentrations of magnetic-susceptible minerals across all grain-size fractions. The correlation between particle size, depositional location, and sedimentary environment indicated variations in the iron-bearing sediment weight in different facies, influenced by environmental energy fluctuations, flow dynamics, and distance from the source area. Based on the findings, ten representative samples from various locations were selected. Magnetic minerals were separated from each grain-size class using a hand magnet, and polished thin sections were prepared in six size fractions for microscopic examination under polarized light and reflected light microscopes. The results of this study demonstrate a direct relationship between grain-size distribution, heavy mineral abundance, provenance type, and the hydrodynamic conditions of the depositional environment. Furthermore, the identification of magnetic-susceptible minerals such as magnetite, hematite, and chromian spinel suggests the localized enrichment of these minerals within specific grain-size ranges, indicating the presence of economic potential in the studied deposits. These findings can serve as a foundation for the development of exploration programs and the evaluation of mineral resources in the region.
