西南暗色岩深渊分异两个系列的岩石化学特征与铁镍矿化的关系

The primary concern of this paper is to analyse the systematic differences in chemical composition between two suites of trap intrusives that bear a close genetic relationship to titaniferous magnetite and nickel sulfide mineralizations respectively.A discussion is also given to the possible mechanisms of differentiation for such differences. The“alkali-ealeium index”(Calk/m=(Ca+Al+Na+K)×100/Mg+Ca+Al+Na+K number of atoms%)ad “acidity”(αsi=Si×100/Si+Ti+Al+Fe+Mn+Mg+Ca+Na+K number of atoms%)were calculated and plotted for various facies belts of the trap intrusives.It is apparent from these diagrams that alkali-calcium indexes of the suites with strong titaniferous magnetite mineralization are systematically higher than that of the niekelsulfide-rieh ones. The former is therefore referred to as “alkali-calcium trap”and the latter “partial-magnesium trap”. The experimental results of D. H. Green and A. E. Ringwood (1964) for samples of olivine thoteiite compositioN agree in many respects with the trend of compositional variation among the two trap groups in Southwestern China. In conjunction with the intimate tectonic relationship between the two suites, it can be inferred that they represent products of the upper and lower daughter magmas derived from a single parent trap magma by fractional crystallization at 12.5--20 kbar and 1200--1300℃. As is evidenced by their compositional features, the Perraian Omeishan basalt floods are probably the eruptive facies of an alkali-caleium daughter magma, but,owing to the peculiarity of differentiation mechanism in the magmatic sources, they exhibit neither rockforming mineral assemblage characteristie of typical olivine tholeiite nor can be regarded as alkali-olivine basalt. A review of available data on various types of magmatie rock formations throughout the world indicates that the chemistry of basic and ultrabasie intrusives related to titaniferous magnetite mineralization is approximately consistent with the characteristics of alkali-calcium trap series, i.e., being rich in calcium and aluminum, slightly rich in alkalis and relatively poor in magnesium. On the other hand, the general petrochemical character of intrusives related to large nickel sulfide deposits is the low contents of alkalis and titanium. It has also been noted that, among these intrusives,a chemical composition comparable to that of “partial-magnesium trap” and. a TiO3 content of less than 1.6% may be much more favorable for nickel sulfide deposition.Furthermore, as an additional requirement, the ultrabmsic facies belts at the lower parts of these intrusives should be ferro-ultrabasic rocks produced by differentiation from tholeiite magma. In many cases, however, little evidence of appreciable nickel sulfide mineralization has been obsernred in magnesium-ultrabasic rocks.

Decomposition mechanism of pentlandite during electrochemical bio-oxidation process

Electrochemical measurements were carried out to elucidate decomposition mechanism of pentlandite using modified powder microelectrode with Acidithiobacillus ferrooxidans attached or without on the mineral powder surface.Cyclic voltammetry（CV） results show that at a low potential of about-0.2 V（vs SCE）,the pentlandite was transformed to an intermediated phase like Fe4.5-yNi4.5-xS8-z when Fe and Ni ions were evacuated from mineral lattice;when the potential was changed from-0.2 V to 0.2 V,the unstable violarite（Fe3Ni3S4） and FeNi2S4 were formed which was accompanied by element sulfur formed on the mineral surface;when the potential increased over 0.2 V,the unstable intermediated phase decomposed entirely;at a higher potential of 0.7 V,the evacuated ferrous ion was oxidized to ferric ion.The presence of Acidithiobacillus ferrooxidans made the oxidation peak current increase with initial peak potential negatively moving,and the bacteria also contributed to the sulfur removing from mineral surface,which was demonstrated by the reduction characteristic at potential ranging from-0.75 to-0.5 V.Leaching experiments and electrochemical results show that the solution acidity increasing when pH2 may impede the oxidation process slightly.

Fe/Co and Ni/Co-pentlandite type electrocatalysts for the hydrogen evolution reaction

Metal-rich transition metal sulfides recently gained increasing attention as electrocatalysts for the hydrogen evolution reaction(HER),as they are capable to overcome major challenges faced by sulfide-rich metal catalysts such as limited conductivity and the necessity of nanostructuring.Herein,we present the synthesis,characterization and electrocatalytic investigation of ternary metal-rich sulfide composites FexCo9-xS8 as well as Ni_(y)Co_(9-y)S_(8)(x=y=0-4.5),which possess pentlandite-type structures.In this study,we show a stepwise alteration of the binary cobalt pentlandite Co9S8 and report on the replacement of cobalt with up to 4.5 equivalents of either iron or nickel.These altered pentlandite composites facilitate the proton reduction in acidic media at different temperatures.We furthermore show that the stoichiometric variation has a decisive influence on the electrochemical activation/deactivation behavior of the catalysts under reductive electrocatalytic conditions.Here,Co-deficient composites display an improved HER performance in contrast to Co_(9)S_(8).Notably,Ni/Co compounds generally tend to show higher catalytic activities towards HER than their respective Fe/Co compounds.

Extraction of valuable metals from low nickel matte by calcified roasting-acid leaching process

A calcified roasting-acid leaching process was developed as a highly effective method for the extraction of valuable metals from low nickel matte in the presence of CaO additive. The influences of process parameters on the metal extraction were studied, including the roasting temperature, roasting time, addition of CaO, H2SO4 concentration and liquid-solid ratio. Under the optimum condition, 94.2% of Ni, 98.1% of Cu, 92.2% of Co and 89.3% of Fe were recovered. Additionally, 99.6% of Fe was removed from the leachate as goethite by a subsequent goethite iron precipitation process. The behavior and mechanism of CaO additive in the roasting process was clarified. The role of CaO is to prevent the formation of nonferrous metal ferrite phases by a preferential reaction with Fe2O3 during the roasting process. The metal oxides(Cu O and NixCu1-xO) remained stable during high-temperature roasting and were subsequently efficiently leached using a sulfuric acid solution.

Electrogenerative leaching of nickel sulfide concentrate with ferric chloride

In order to utilize the chemical energy in hydrometallurgical process of sulfide minerals reasonably and to simplify the purifying process, the electrogenerative process was applied and a dual cell system was introduced to investigate FeCl3 leaching of nickel sulfide concentrate. Some factors influencing the electrogenerative leaching, such as electrode structure, temperature and solution concentration were studied. The results show that a certain quantity of electrical energy accompanied with the leached products can be acquired in the electrogenerative leaching process. The output current and power increase with the addition of acetylene black to the electrode. Varying the components of electrode just affects the polarization degree of anode. Increasing FeCl3 concentration results in a sharp increase in the output of the leaching cell when c（FeCl3） is less than 0.1 mol/L. The optimum value of NaCl concentration for electrogenerative leaching nickel sulfide concentrate with FeCl3 is 3.0 mol/L. Temperature influences electrogenerative leaching by affecting anodic and cathodic polarization simultaneously. The apparent activation energy is determined to be 34.63 kJ/mol in the range of 298 K to 322 K. The leaching rate of Ni2+ is 29.3% after FeCl3 electrogenerative leaching of nickel sulfide concentrate for 620 min with a filter bag electrode.