The Spatial Distribution of Trace Elements and Rare-Earth Elements in the Stream Sediments Around the Ikuno Mine Area in Hyogo Prefecture, Southwest Japan

In the present study, major oxide, trace, and rare-earth element (REE) contents in the stream sediments of the Ikuno and surrounding areas of the central part of Hyogo Prefecture in the Kinki district in southwestern Japan were analyzed. Several abandoned mines that contain Au, Ag, Cu, Pb, Zn, Fe, W, and As exist in these areas, including the Ikuno and Akenobe mines, which are famous historical mines. A total of 156 stream sediments over approximately 1300 km2 in these areas were analyzed using X-ray fluorescence (XRF) and inductively coupled plasma mass spectrometry (ICP-MS). The spatial distribution patterns of elemental concentrations in the stream sediments in the Ikuno area were determined by three primary factors: the surface geology, the localized deposition of ore minerals, and the influence of the sedimentation of heavy minerals in the basin on local distribution. The mean value of the spatial distributions of the ore deposits was greater than the median, primarily due to the presence of concentrated regions near the mining sites. A Kolmogorov–Smirnov test indicated abnormal distribution patterns of Pb, Zn, Cu, Cr, and Ni due to the presence of exceptionally high concentrations of these elements at the mine sites. The stream sediments showed higher levels of light REEs, mainly La, Ce, and Nd, in comparison with the heavy REEs. This pattern, deviating from the global abundance, suggests the dominating influence of mining sites on local REE distributions. These findings are essential for assessing the environmental impacts of historical mining and developing strategies for responsible resource management in the region. By understanding the geochemical signatures of mining-affected areas, these data could contribute to future environmental monitoring and mitigation efforts, enhancing our understanding of environmental sustainability and responsible resource utilization.