ASTER-based mapping of iron skarn mineralization in Keban (Elazığ), Eastern Türkiye: Insights from mineralogical, geochemical, and spectral validation

This study investigates the iron-bearing mineral deposits and contact-metamorphic skarn zones associated with magmatic intrusions in the Keban region (Elazığ, Eastern Türkiye), focusing on the Aşvan (Muratçık), Fatmalı, Üçağaç, and Ulupınar (Birvan) areas. The primary objective is to delineate the spatial extent of Fe-bearing zones using ASTER imagery and to evaluate their multi-stage paragenetic evolution through integrated field verification, mineralogy, petrography, and geochemistry. Advanced image processing techniques specifically ASTER band ratios B2/B1 ferric iron, B5/B4 (iron silicates), and B4/B5 (lateritic zones) were applied using statistical thresholding to map iron anomalies. The spatial distribution of spectral anomalies was quantitatively cross-validated with field samples (MEU series) and reference datasets (MS series) and historical exploration data. Petrographic, mineralogical, and geochemical analyses demonstrate a distinct chemical variation across the skarn system, with total iron contents shifting sharply from dioritic/gabbroic endoskarn contacts (1–15 % FeO) and exoskarn zones (14–24 % FeO) up to high-grade skarn/oxide mineralization (> 45–52 % FeO). These geochemical markers, accompanied by high Loss on Ignition (LOI up to 8.99%), mobile trace element enrichments (Cu up to 145.42 ppm, Zn up to 185.32 ppm), and XRD identification of nontronite and jarosite, confirm that the Keban system experienced a multi-stage evolution: high-temperature prograde skarn formation, late-stage low-temperature retrograde hydrothermal overprinting, and subsequent supergene lateritization. Notably, the precise spatial overlap between pre-mining 2003 ASTER anomalies and post-2012 open-pit excavations demonstrates that this remote sensing methodology acts as a powerful predictive tool for mapping surface micro-leakage signatures of blind (buried) mineralization. Overall, this study confirms the efficacy of integrating spectro-mineralogical satellite mapping with empirical ground-truthing for iron ore prospection in rugged, geologically complex skarn terrains.