Geochemistry of Fe3+ in the hydrothermal dickite from Jedlina Zdroj (Lower Silesia, Poland)

Abstract

Geochemical analysis for Fe was made on a representative sample of dickite-rich hydrothermal clay from Jedlina Zdroj. The mineralogy of the sample is comparatively simple, dickite being the principal component (>95 wt. % of the total sample), with lesser amounts of goethite and barite. Geochemical fractionation and inductively coupled plasma-optical emission spectrometry indicated that most of the Fe (ca. 97 wt. % of the total metal) resides in the dickite. Electron spin resonance showed that some of the Fe in the dickite structure is in the form of Fe3+. A substantial proportion of these ions (as well as Fe) in the dickite matrix were probably contained in the original hydrothermal dickite-forming solution. From the geochemistry of Fe3+, it was deduced that the oxidation potential (Eh) and pH of the solution during the formation of dickite from the Jedlina Zdroj were approximately 0.45-0.95 V (highly oxygenated) and 0-4 (highly acidic), respectively