RT Journal Article
T1 Rare earth element signature modifications induced by differential acid alteration of rocks in the Iberian Pyrite Belt
A1 Cuadros, Javier
A1 Mavris, Christian
A1 Nieto Liñán, José Miguel
AB The efficient use of REE as tracers of weathering processes requires further data acquisition to establish robust connections between mechanisms, mineral assemblages and REE concentration patterns. Here, results are provided corresponding to rocks from four locations in the Iberian Pyrite Belt that were altered with different intensity by sulfuric fluids. The acidic alteration was mild (pH 5–7) in Calañas and El Villar, while strong (pH below 3 to 5) in Quebrantahuesos and Tharsis. The main REE reservoir before alteration were phyllosilicates (and plagioclase/feldspar in El Villar only). Mild alteration generated mainly kaolinite while illite and some plagioclase/feldspar were preserved. Mildly altered rocks approximately preserved the relative REE concentrations of their precursors, interpreted as indicating a low fluid/rock ratio environment where binding sites in minerals outnumbered those in fluids. Strong acid alteration produced alunite, jarosite, beudantite and goethite, with partial illite preservation. Where illite and/or goethite were major minerals, this alteration generated REE patterns enriched in light REE over heavy REE or did not modify the relative REE concentrations of the original rock. However, samples where REE concentrations were controlled by alunite or jarosite had LREE > > HREE. In alunite the maximum concentration corresponded to Nd and Sm. In jarosite concentrations decreased from La to Lu, except that a positive Eu anomaly was preserved from the precursor. These REE concentration patterns are interpreted as due to crystallographic factors, controlled by the best fit of REE with charge 3+ in the 12-fold coordination site of K in jarosite and alunite. This site is larger in jarosite and fits La best, whereas the smaller site in alunite best fits Nd and Sm. Goethite REE signature is variable, perhaps due to two formation routes, (1) silicates ➔ goethite and (2) silicates ➔ jarosite ➔ goethite. Our interpretations of REE concentration in alunite, jarosite and goethite are novel and provide new routes to further develop REE as tracers of acid alteration processes.
PB Elsevier
SN 0009-2541
YR 2023
FD 2023
LK https://hdl.handle.net/10272/21972
UL https://hdl.handle.net/10272/21972
LA eng
NO Cuadros, J., Mavris, C., & Nieto, J. M. (2023). Rare earth element signature modifications induced by differential acid alteration of rocks in the Iberian Pyrite Belt. In Chemical Geology (Vol. 619, p. 121323). Elsevier BV. https://doi.org/10.1016/j.chemgeo.2023.121323
DS Repositorio Institucional de la Universidad de Huelva
RD 30 may 2026