Effects of Galvanic Interaction between Chalcopyrite and Monoclinic Pyrrhotite on Their Flotation Separation

The galvanic interaction between chalcopyrite and monoclinic pyrrhotite and its effect on flotation separation were studied using monomineral flotation tests, adsorption capacity tests, X-ray photoelectron spectroscopy (XPS) characterization, and scanning electron microscopy (SEM) test. These results showed that the interaction promoted the reduction of O2 on the cathodic chalcopyrite surface and accelerated the generation of Fe(OH)3, which was not conducive to collector adsorption; hence, the flotation recovery decreased by 10–16%. On the other hand, galvanic interaction accelerated the oxidation of S on the anodic monoclinic pyrrhotite surface to S0 or SO42− and produced a large amount of H+, thus preventing the formation of Fe(OH)3. Meanwhile, the Cu2+ eluted from chalcopyrite surface activated monoclinic pyrrhotite; hence, the flotation recovery increased by 3–10%. Galvanic interaction reduced the floatability difference between the two minerals, and the separation difficulty was significantly increased. Even with an increase in the amount of lime, the separation could not be improved.

Distribution of sulfides and PGE minerals in the picritic and taxitic gabbro-dolerites of the Norilsk 1 intrusion

ABSTRACT Disseminated ores in the Norilsk 1 intrusion were studied to elucidate the typomorphic features of sulfides and noble metal mineralizations in picritic and taxitic (or lower olivine) gabbro-dolerites. The former are characterized by the development of a low-sulfur sulfide association (troilite, Fe-rich pentlandite, talnakhite, chalcocite, native copper) while the latter exhibits a high-sulfur association (monoclinic pyrrhotite, Ni-rich pentlandite, pyrite, heazlewoodite). The contact between these types of rocks is geochemically and mineralogically contrasting. The mineralogical and geochemical zoning directed from the roof to the base of each layer is expressed by an increase in the Cu content (and chalcopyrite) in ores, an increase in the concentration of Ni in pentlandite and S in pyrrhotite in line with a decrease of the crystallization temperature, and an increase in sulfur fugacity in the same direction. Zoning of Pd(Pt) mineralization in picritic and taxitic (olivine) gabbro-dolerites is uniform and characterized by the distribution of Pd-Sn compounds in the upper parts (together with Pd-Pb minerals in picritic rocks) and Pd-As compounds in the lower parts of the sections according to a drop in temperature. Such reverse zoning contradicts the typical mechanism of differentiation by fractional crystallization, and possibly suggests a fluid-magmatic nature. Mineralogical and geochemical features in platinum group element-Cu-Ni-bearing rocks are consistent with the idea that different stages of multi-pulse intrusions of mafic-ultramafic magmas with different compositions formed the picritic and taxitic gabbro-dolerites of the Norilsk region.

Preparation of Monoclinic Pyrrhotite by Thermal Decomposition of Jarosite Residues and Its Heavy Metal Removal Performance

Jarosite residues produced by zinc hydrometallurgical processing are hazardous solid wastes. In this study, monoclinic pyrrhotite (M­Po) was prepared by the pyrolysis of jarosite residues in H2S atmosphere. The influence of gas speed, reaction temperature, and time was considered. The mineral phase, microstructure, and elemental valence of the solids before and after pyrolysis were analyzed using X­ray diffraction, scanning electron microscopy, and X­ray photoelectron spectroscopy, respectively. The performances of the prepared M­Po on the removal of Zn and Pb from aqueous solution were evaluated. The results show M­Po to be the sole product at the reaction temperatures of 550 to 575 °C. Most of the M­Po particles are at the nanometer scale and display xenomorphic morphology. The phase evolution process during pyrolysis is suggested as jarosite → hematite/magnetite → pyrite → pyrite+M­Po → M­Po+hexagonal pyrrhotite (H­Po) → H­Po. The formation rate, crystallinity, and surface microtexture of M­Po are controlled by reaction temperature and time. Incomplete sulfidation may produce coarse particles with core–shell (where the core is oxide and the shell is sulfide) and triple-layer (where the core is sulfate, the interlayer is oxide, and the shell is sulfide) structures. M­Po produced at 575 °C exhibits an excellent heavy metal removal ability, which has adsorption capacities of 25 mg/g for Zn and 100 mg/g for Pb at 25 °C and pH ranges from 5 to 6. This study indicates that high-temperature sulfidation is a novel and efficient method for the treatment and utilization of jarosite residues.

Geochemical Features and Mineral Associations of Differentiated Rocks of the Norilsk 1 Intrusion

The purpose of this study is to show the patterns of distribution of disseminated sulfide in layered rocks based on the numerous geochemical and mineralogical data obtained for eight boreholes of the Norilsk intrusion (southern part of the Norilsk 1 deposit). There is a common trend of sulfide liquid fractionation in the Main Ore Horizon, which is composed of picritic and taxite (or olivine) gabbro-dolerites: the Ni/Cu in both rock types decreases down all sections, indicating an increase in the degree of fractionation of the sulfide liquid from top to bottom. On the contrary, the Ni/Fe ratios in pentlandite increase in this direction due to an increase in sulfur fugacity. However, picrite and taxite/olivine gabbro-dolerites are very distinctly separated by Ni/Cu values: these values are >1 in picritic gabbro-dolerite while they are always <1 in taxite/olivine gabbro-dolerite. These rock types are distinguished by sulfide assemblages. The first includes troilite, Fe-rich pentlandite, chalcopyrite, cubanite, talnahite, bornite and copper (low sulfur association); the second one is composed of monoclinic pyrrhotite, chalcopyrite, Ni-rich pentlandite and pyrite (high sulfur association). A two-stage magma injection with different ore specializations is supposed for picritic and taxite/olivine gabbro-dolerites.

The evolution of the ore-forming system in the low sulfide horizon of the Noril'sk 1 intrusion, Russia

We present here new data on the low-sulfide mineralisation in the upper endocontact of the Noril'sk 1 intrusion. Twenty four mineral species of platinum-group elements and their solid solutions, as well as numerous unnamed phases, including an Sb analogue of vincentite, As and Sn analogues of mertieite-I and a Sn analogue of mertieite-II have been found. It is shown that the features of the mineral association: (1) the atypical trend of TiO2 and Fe2+ in chromian spinel; (2) the composition of the Pt–Fe alloys with a Fe/Fe + Pt range of 0.26–0.37 (logfO2 ≈ – (9–10); and (3) crystallisation of high-temperature sperrylite from silicate melt (at >800°C and logfS2 < –10.5), which is possible under fO2 of FMQ to FMQ-2 in mafic magma, are due to the reducing conditions of their formation and evolution. Droplet-like inclusions of silicate-oxide minerals in сhromian spinels and sulfides in platinum-group minerals are interpreted to be trapped droplets of co-existing sulfide melt. The captured sulfide melt has evolved in the direction of increasing the fugacity of sulfur: troilite + pentlandite (Fe>Ni) – in sperrylite (paragenesis I) to monoclinic pyrrhotite + pentlandite (Ni≈Fe) + chalcopyrite – in Pt–Fe alloys (paragenesis II). Paragenesis from the sulfide aggregates in the silicate matrix are more fractionated: pyrrhotite + pyrrhotite (Ni>Fe) + chalcopyrite (III) and pyrite + pentlandite (Ni>>Fe) + millerite (IV). Pd arsenides and antimonides crystallised later than sperrylite and isoferroplatinum, as a result of the evolution of a sulfide melt with an increased activity of the element ligands (Te, Sn, Sb and As).