Patterns of Rare Earth Elements in Sediments as Tracers in a Fluvial System Influenced by a Gold Mine, El Triunfo, BCS, Mexico

Concentrations of rare earth elements (REE) were analyzed to determine their variations in various samples, such as sediments, tailings, and ash at the mining district El Triunfo (MDET) and its adjacent coastal zone. The REE concentrations were measured in tailings and ash, showing a clear variation in their contents, distribution, and the Eu anomalies among the MDET. These were compared with the surface sediments along the Hondo–Las Gallinas–El Carrizal (H – G – C) arroyo, a test pit, sediment core, and dunes at the end of the arroyo discharge adjacent to the Pacific Ocean. The results show a clear anthropogenic influence because of the depleted contents in the tailings, ash, and the test pit. Although larger REE concentrations were found in the arroyo basin, its contents remain depleted as compared to the National American Shale Composition (NASC). Therefore, the perturbation caused by the mining is masked by the natural contents and the high weathering degree of the rocks. The artisanal mining has altered the El Triunfo fluvial system, and its associated sediments, in its discharge to the Pacific Ocean.