MINERALOGY OF WEATHERING PRODUCTS OF Fe-As-Sb MINE WASTES AND SOILS AT SEVERAL Sb DEPOSITS IN SLOVAKIA

Abstract

We present the results of an investigation of tailing ponds and contaminated soils at five antimony deposits in Slovakia, Pezinok, Dubrava, Medzibrod, Cucma, and Poproc. With the exception of Poproc, all primary mineralization contained abundant carbonates; the sites studied are examples of neutral mine drainage. The Fe–As–Sb-rich products of weathering were studied in 250 samples of tailings and also in contaminated soils for comparison. They were examined by means of 2500 electron-microprobe (EMP) and 500 micro-X-ray diffraction (μ-XRD) analyses. The primary focus of this work is the incorporation of the metalloids Sb and As into (poorly) crystalline authigenic phases, not their association with mineral surfaces. The EMP analyses define a densely populated field in a triangular Fe–Sb–As diagram. Compositions along the entire Fe–Sb edge are common; many of them lie near the Fe apex, with an (As + Sb)/(Fe + As + Sb) value not exceeding 0.3. Oxidation-induced rims on arsenopyrite mostly consists of X-ray-amorphous hydrous ferric oxides (HFO) with average As and Sb contents equal to 13.9 and 5.69 wt%, respectively. The rims developed on pyrite mostly consist of goethite or a mixture of goethite and HFO, which acts as effective sorbents of As, Sb, Ca, Si and Cu. Among the grains without relics of primary sulfides, HFO with variable concentrations of As, Sb is common. The most common secondary mineral at all sites is goethite, with average As and Sb contents of 1.33 and 3.93 wt%, respectively. A very common Sb-bearing secondary phase at all studied localities is tripuhyite (FeSbO 4 ). Calcium antimonates with the pyrochlore structure are typical of environments rich in Ca. Simple secondary Sb oxides such as cervantite and senarmontite were observed each in only one soil sample. Beudantite was identified in a few samples with a higher Pb content. In one sample, a porous secondary oxide rich in Pb and As was identified as clinomimetite.