RT Journal Article
T1 Mineralogical and Crystal-Chemical Constraints on the Glauconite-Forming Process in Neogene Sediments of the Lower Guadalquivir Basin (SW Spain)
A1 Fernández Landero, Sandra
A1 Fernández Caliani, Juan Carlos
AB Glaucony is a significant green marine facies in the northwestern passive margin ofthe Guadalquivir Basin (Spain), where glauconite formed authigenically on a sediment-starvedcontinental shelf, with fecal pellets and benthic foraminiferal tests being the main glauconitizedsubstrates. Results from a study using XRD, TGA-DSC, SEM-EDS, and EPMA have revealed thatglauconite is remarkably heterogeneous in mineral composition and chemical maturity, even in asingle grain, reflecting a complex interaction of micro-environmental factors, substrate influencesand post-depositional alterations. In its early stage, the glauconitization process is consistent withthe slow precipitation of a Fe-rich smectite phase, most likely intergrade between nontronite andFe-montmorillonite end-members, which evolved to a regularly interstratified glauconite-smectite(Gl/S). The Fe-smectite-to-Gl/S transformation is interpreted as a diffusion-controlled reaction,involving sufficient Fe availability in pore water and the constant diffusive transport of seawaterK+ and Mg2+ ions towards the substrate. The pelletal glauconite is actually a highly evolved Gl/Sconsisting almost totally of mica layers, with 0.74 ± 0.05 apfu of K+in the interlayer, while the Gl/Soccurring as replacements of foraminiferal tests contains a mean of 7% of expandable layers in thewalls and 16% in the chamber fillings, due to rate-limited ion diffusion.
PB MDPI
SN 2075-163X (electrónico)
YR 2021
FD 2021-05
LK http://hdl.handle.net/10272/20071
UL http://hdl.handle.net/10272/20071
LA eng
NO Fernández-Landero S, Fernández-Caliani JC. Mineralogical and Crystal-Chemical Constraints on the Glauconite-Forming Process in Neogene Sediments of the Lower Guadalquivir Basin (SW Spain). Minerals. 2021; 11(6):578. https://doi.org/10.3390/min11060578
NO We thank Fernando Muñiz (University of Seville) for its collaboration duringfieldwork, Josep Tosquella (University of Huelva) for helping with microfossil identification, andJesús Díaz (University of Huelva) for assistance with thermal analysis. The authors greatly appreciatethe quick and valuable review of the manuscript by three anonymous referees.
DS Repositorio Institucional de la Universidad de Huelva
RD 14 jul 2026