Seasonal variations in the formation of Al and Si rich Fe-stromatolites in the highly polluted acid mine drainage of Agua Agria Creek (Tharsis, SW Spain)

• Published in: Chemical geology 2011-05, Vol.284 (1), p.97-104
• Main Authors: Caraballo, Manuel A., Sarmiento, Aguasanta M., Sánchez-Rodas, Daniel, Nieto, José Miguel, Parviainen, Annika
• Format: Article
• Language: English
• Subjects: Acid mine drainage; Aluminum; Bacillariophyceae; Bacillariophyta; complement; Diatoms; drought; Extreme environments; Fe-stromatolites; goethite; Iron; Jarosite; Minerals; rivers; Rostite; seasonal variation; Seasonal variations; silicon; Surface layer; Texture
• ISSN: 0009-2541; 1872-6836
• DOI: 10.1016/j.chemgeo.2011.02.012

The study of the different biotic and abiotic processes involved in the current formation of Fe-stromatolites in rivers affected by acid mine drainage (AMD) is essential not only to understand this unique and extreme environment, but also to achieve a better understanding of the past iron formation on the Earth and on Mars. The Fe-stromatolites studied in the highly polluted AMD in Tharsis, SW Spain, revealed a unique mineral assemblage with jarosite and rostite as the most unexpected Fe and Al phases and goethite and schwertmannite as the main constituents. Seasonal variations in this region greatly affected the composition of the precipitates and the distribution of diatoms within the Fe-stromatolites. Drought and flood events were also recognized in the sedimentary textures and in the mineral assemblages observed of particular layers within the Fe-stromatolites. The characterization of the chemical and mineralogical composition of Fe-stromatolites in Tharsis as well as the different formation mechanisms proposed complement the existing literature on newly-formed Fe-stromatolites and provides new observations to increase our understanding of those extreme environments. ► Jarosite and rostite were observed as Fe-stromatolites forming minerals. ► Al and Si enrichment in the Fe-stromatolites reflects the extreme water chemistry. ► Seasonal variations in water chemistry was linked to the precipitates mineralogy. ► Diatoms distribution in the Fe-stromatolites reflects water seasonal variations. ► A detailed description of an extreme environment resembling Mars surface was offered.