HFO as the main contaminant carrier and transporting agent downstream the Zarshuran As deposit, NW lran

The Zarshuran arsenic deposit has been exploited for more than one thousand years. During this period of time, trace element pollutants have been transported downstream via natural agents, however this process has been exacerbated by human interferences, such as mining activities, especially in recent years. Geochemical study of metallic contaminants revealed a high concentration of elements especially of As, Sb, Hg, and TI in ore, waste piles, water and stream sediments, so that the arsenic concentration ranges between 40-0.028 mg/L in water samples of the Zarshuran Stream. In order to investigate the mechanism of contaminant transport downstream the mine, the concentrations of arsenic and other trace elements detected in ore-waste assemblage were measured in water samples taken from 11 stations. Also, the pH and Eh values have been measured in the same waster samples. The arsenic ore mainly consists of orpiment and realgar, associated with a small amount of Sb, Hg, Tl, minerals. Weathering of this assemblage gives rise to a mine water having an arsenic concentration of 22 mg/L. As concentrations are reduced to 4.272, 3.069, 0.421, 0.083, and 0.036 mg/L at distances of about 1, 1.3, 3.3, 7 and 15.2 km down the mine, respectively. The water samples have been passed through the 0.45μ filters to determine the fraction of contaminants transported in dissolved phase and also in particulate phase. The geochemical study of contaminant transport indicates that contaminants are transported mainly as colloidal and particulate phases in the upstream and only 13% of arsenic is transported as the dissolved phase. The milky appearance of stream is evidence for colloidal transport. From 6 km downward the mine, particulate phase is not the significant carrier of contaminants and more than 90% of the arsenic is transported as dissolved phase. The very positive correlation between trace element concentrations and Fe, colloidal deposition evidence as an ocher-colored precipitate on stream bed sediments accompanied by a decrease in contaminant concentrations in stream water, the physicochemical （Eh and pH） conditions, near neutral pH values, considerable difference in concentration of Fe in dissolved and total phases, weathering of iron sulfides in the ore-waste assemblage, XRD analysis of precipitates, indicate strongly that HFO is the main carrier and transporting agent in this area.     

Sorption of Zr~(4+) and Hf~(4+) onto Hydrous Ferric Oxide and Their Fractionation Behaviors:An experimental Study

1 Introduction Coherent element pairs (Y3+-Ho3+, Zr4+-Hf4+, Nb5+-Ta5+ and Sr2+-Eu2+) have the same valences and very similar ionic radii. They are seldom fractionated during silicate mineral/melt interaction systems because the partitioning of these element pairs between melts and minerals is tightly controlled by charge valence and crystal structure (lattice site size) or ionic radius. The concentration ratios of these pairs in igneous rocks are close to the chondritic values (Y/Ho=28, Zr…     

Natural alteration products of sulphide mattes from primary lead smelting

The natural alteration products developed on mattes from lead metallurgy were determined: oxides and hydroxides (HFO, Cu(OH)₂), sulphates (thenardite, gypsum), hydroxysulphates (jarosite, beaverite, brochantite) and carbonates (cerussite, malachite, NaOH·2 PbCO₃). The large range of stability of newly formed phases confirms a significant variety of E_h–pH conditions of natural weathering of matte. Jarosite is stable at pH<3, but some hydroxides and carbonates typically form in neutral and alkaline environments. Consequently, the best dumping conditions for metallurgical mattes are difficult to determine. Such materials can have severe environmental effects and should be dumped in controlled waste-disposal sites. To cite this article: V. Ettler et al., C. R. Geoscience 335 (2003).     

A Synthetic Haematite Reference Material for LA‐ICP‐MS U‐Pb Geochronology and Application to Iron Oxide‐Cu‐Au Systems

In both nature and synthetic experiments, the common iron oxide haematite (α‐Fe₂O₃) can incorporate significant amounts of U into its crystal structure and retain radiogenic Pb over geological time. Haematite is a ubiquitous component of many ore deposit types and, therefore, represents a valuable hydrothermal mineral geochronometer, allowing direct constraints to be placed on the timing of ore formation and upgrading. However, to date, no suitable natural haematite reference material has been identified. Here, a synthetic haematite U‐Pb reference material (MR‐HFO) is characterised using LA‐ICP‐MS and ID‐TIMS. Centimetre‐scale ‘chips’ of synthesised α‐Fe₂O₃ were randomly microsampled via laser ablation‐extraction and analysed using ID‐TIMS. Reproducible U/Pb and Pb/Pb measurements were obtained across four separate chips (n = 13). Subsequently, an evaluation of the suitability MR‐HFO in constraining U‐Pb data via LA‐ICP‐MS is presented using a selection of natural samples ranging from Cenozoic to Proterozoic in age. The MR‐HFO normalised U‐Pb ratios are more concordant and ages more accurate versus the same LA‐ICP‐MS spot analyses normalised to zircon reference material, when compared with independently acquired ID‐TIMS data from the same natural haematite grains. Results establish MR‐HFO as a suitable reference material for LA‐ICP‐MS haematite U‐Pb geochronology.