Evaluating the Alteration Zones and Environmental Impacts in the Chore Nab Iron Mine, NW Iran

This research focuses on investigating the alteration zones and environmental impacts of potentially toxic element pollution in the soil surrounding Chore Nab in the Tarom subzone. Based on field and petrographic evidence, the area exhibits six alteration zones in both plutonic and volcanic rocks. Pollution indicators, such as the Igeo index, reveal a moderate arsenic (As) concentration of 1.36. Enrichment factor (EF) values indicate moderate enrichment for Cd at 2.74, Cr at 2.38, and Mn at 2.45, with significant enrichment for As at 6.50. The pollution index (PI) indicates high arsenic pollution (3.86), while the pollution load index (PLI) reflects poor soil quality. The results reveal that arsenic poses a significant environmental and health risk, with a high EF of 6.50 and a PI of 3.86. During the study, significant positive correlations were found between Co and Ni (0.876), V and Ni (0.793), Mg and Co (0.704), Cu and Cd (0.982), and Cu and Pb (0.805), suggesting a common origin, presence in sulfide minerals, or similar geochemical behavior among these elements in relation to one another. Moreover, multivariate statistical methods, including principal component analysis (PCA) and hierarchical cluster analysis (HCA), were employed for soil classification. PCA revealed three factors accounting for 77.70% of the variance: the first factor (43.34%) includes Ni, Co, As, Ca, Cu, Fe, Pb, V, and Cd; the second factor (23.52%) includes Zn and Mg; and the third factor (10.84%) includes Co and Mo, which control the quality of soil resources. Based on HCA analysis, four clusters were observed. The multivariate analyses suggest that the source of contamination is primarily natural, with human activities not contributing to additional pollution in the area. Pearson correlation and PCA indicate that the distribution of elements such as Cd, Fe, Ni, Cu, As, Pb, Ca, V, and Co is controlled by lithological sources, while the distribution of Zn and Mg is influenced by rock weathering and the alteration of mafic rocks.