Structural incorporation of W⁶⁺into hematite and goethite: A combined study of natural and synthetic iron oxides developed from precursor ferrihydrite and the preservation of ancient fluid compositions in hematite

Abstract

Hematite (a-Fe2O3) and goethite (a-FeOOH) can incorporate considerable amounts of tungsten (W). Although W concentrations up to several wt% in hematite and goethite have been reported in the literature, none of the proposed models for a structural incorporation has been generally accepted yet. Here, the first combination of X-ray absorption fine structure (XAFS) measurements with X-ray diffraction (XRD), Raman spectroscopy (RS), electron microprobe (EMPA) and total reflection X-ray fluorescence (TXRF) provides a general relation between W content and its structural incorporation into hematite and goethite.