Geological, geomorphological, and environmental insights into the Neoproterozoic Aswan granites, Egypt: remote sensing and radiological assessment

TL;DR

This study uses remote sensing and radiological data to analyze the geological and environmental characteristics of Neoproterozoic Aswan granites in Egypt, highlighting their impact on landscape and safety.

Contribution

The integration of remote sensing and radiological data provides new insights into the geological and environmental dynamics of the Aswan granites.

Findings

Four granite suites were identified, each with distinct geological and radiological properties.

Radiological parameters in fine-grained granites exceed indoor-use limits, while others remain within safety standards.

Lithology and structural features primarily control landscape evolution and quarrying suitability.

Abstract

The Neoproterozoic Aswan granites constitute a major post-collisional intrusive complex within the Egyptian Nubian Shield and represent one of Egypt’s most significant geological, geomorphological, and cultural landscapes. Integrated remote-sensing and radiological data are used to characterize their geological, geomorphological, and environmental attributes. Four granite suites are recognized in the Aswan area: greyish-black tonalites–granodiorites, coarse pink monzogranites–syenogranites, medium- to coarse-grained High Dam granites, and fine-grained granites. These lithologies exert a strong control on regional geomorphology, with structural fabrics—dominated by N–S and NE–SW joint sets and locally developed NE-trending shear zones—governing drainage patterns, landscape evolution, quarrying potential, and the distribution of radioelements. Integrated geomorphological and remote sensing analyses demonstrate that lithology and structural framework exert primary control on the Nile’s course and on the development of characteristic granite landforms, including inselbergs, exfoliation domes, joint-controlled valleys, steep canyons, and granitic island chains. PRISMA hyperspectral data further enhanced this framework by differentiating the rock units, delineating shear zones, and clearly identifying quarrying scars and associated landscape degradation. All remote-sensing interpretations were validated through detailed geological field investigations, ensuring accurate characterization of the granitic rocks and their modification by human activities. The granites show progressive differentiation from greyish-black granodiorites to coarse pink and fine-grained types, with U–Th–K enrichment and mean activities of 238U (77.23 Bq/kg), 226Ra (41.93 Bq/kg), 232Th (73.07 Bq/kg), and 40K (1281.3 Bq/kg), exceeding global averages. Radiological parameters record mean values of 131.35 nGy/h (absorbed dose), 0.16 mSv/y (annual effective dose), 275.82 Bq/kg (radium equivalent), hazard indices of 0.74 and 0.95, and a gamma index of 2.07. Fine-grained granites locally exceed indoor-use limits, High-Dam granites show moderate Th–K enrichment due to deformation, whereas greyish-black and most coarse pink granites (including Fila) remain within safety limits and are most suitable for quarrying. Overall, lithology and structural architecture—rather than external environmental factors—control mechanical behavior, landscape evolution, quarrying suitability, and radiological distribution across the Aswan granite province. Despite generally safe radiological levels, unregulated quarrying and rapid urban expansion have altered terrain and disrupted geomorphic integrity. These findings provide a framework for sustainable resource management, radiological safety evaluation, geomorphology-informed land-use planning, and preservation of Aswan’s unique geological and cultural heritage.

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