Magmatic Ni-Cu-(PGE) deposits in magma plumbing systems:Features,formation and exploration

The three most crucial factors for the formation of large and super-large magmatic sulfide deposits are： （1） a large volume of mantle-derived mafic-ultramafic magmas that participated in the formation of the deposits; （2） fractional crystallization and crustal contamination, particularly the input of sulfur from crustal rocks, resulting in sulfide immiscibility and segregation; and （3） the timing of sulfide concentration in the intrusion. The super-large magmatic Ni-Cu sulfide deposits around the world have been found in small mafic-ultramafic intrusions, except for the Sudbury deposit. Studies in the past decade indicated that the intrusions hosting large and super-large magmatic sulfide deposits occur in magma conduits, such as those in China, including Jinchuan （Gansu）, Yangliuping （Sichuan）, Kalatongke （Xinjiang）, and Hongqiling （Jilin）. Magma conduits as open magma systems provide a perfect environment for extensive concentration of immiscible sulfide melts, which have been found to occur along deep regional faults. The origin of many mantle-derived magmas is closely associated with mantle plumes, intracontinental rifts, or post-collisional extension. Although it has been confirmed that sulfide immiscibility results from crustal contamination, grades of sulfide ores are also related to the nature of the parental magmas, the ratio between silicate magma and immiscible sulfide melt, the reaction between the sulfide melts and newly injected silicate magmas, and fractionation of the sulfide melt. The field relationships of the ore-bearing intrusion and the sulfide ore body are controlled by the geological features of the wall rocks. In this paper, we attempt to demonstrate the general characteristics, formation mechanism,tectonic settings, and indicators of magmatic sulfide deposits occurring in magmatic conduits which would provide guidelines for further exploration.

Adsorption properties of Ag(Ⅰ),Au(Ⅲ),Pd(Ⅱ)and Pt(Ⅳ)ions on commercial 717 anion-exchange resin

The adsorption properties of the four precious metal ions(Ag(Ⅰ),Au(Ⅲ),Pd(Ⅱ)and Pt(Ⅳ))on the commercial Cl--form 717 strongly basic anion-exchange resin were studied in detail.The effects of the contact time,solution acidity,and concentrations of Cl - and Pb 2+ ions on the adsorption properties were studied by the batch method.Then,the column method was conducted under the optimized adsorption conditions(pH=3.0).The effects of the sample loading flow rate and the length-to-diameter ratios of the columns were investigated.The precious metal ions adsorbed could not be eluted completely after the saturated adsorption because the precious metal ions were found to be reduced to their metallic states during the adsorption process.So,it is recommended that the commercial Cl--form 717 strongly basic anion-exchange resin should be decomposed directly to recovery the precious metals after the saturated adsorption.

Tracing Sources of Geochemical Anomalies in a Deeply Buried Volcanic-Related Hydrothermal Uranium Deposit:the Daguanchang Deposit,Northern Hebei Province,North China Craton

Radon(Rn)and helium(He)gases from uranium decay form distinct anomalies related to buried uranium deposits.In order to trace the geochemical anomalous sources from the volcanic-related uranium deposits in deeply buried areas,systematical Rn contents and He isotope ratios were analyzed from the Daguanchang uranium deposit.The soil gas Rn concentrations above the deep uranium are ten times higher than those in barren areas,indicating that instantaneous Rn content measurements can be used to detect deeply buried uranium.The helium isotope ratios(^(3)He/^(4)He)of the unmineralized samples from the mineralized drill hole(ZK1)are relatively lower and uniform compared to those of the samples from no-mineral drill hole(ZK2).However,the Th and U contents of the drill core samples from ZK1 are slightly lower than those of the samples from ZK2,indicating that the lower 3He/4He ratios in ZK1 are most likely due to the addition of 4He from underlying uranium intervals.The differences in the instantaneous Rn contents are consistent with the variations in the He isotope ratios of the drill core samples.These results demonstrate that soil gas Rn and ^(3)He/^(4)He ratios are useful tracers and can indicate the existence of deeply buried volcanic-related hydrothermal uranium ores.

Mechanism of fluidized chlorination reaction of Kenya natural rutile ore

In this paper, the thermodynamics and kinetics of nature rutile carbochlorination in a fluidized-bed were investigated. The thermodynamic calculations of TiO2-C- C12 system show that when C is excess in the solid phase, titanium tetrachloride and carbon monoxide can exist sta- bly. At high temperature, the reaction with CO as the product is the dominant reaction. The appropriate reaction conditions are as follows： reaction temperature of 950 ℃, reaction time of 40 min, carbon ratio of 30 wt% of rutile, natural rutile particle size of -96 μm, petroleum coke size of -150 μm, and chlorine flow of 0.036 m3.h-1. Under the above conditions, the reaction conversion rate of TiO2 can reach about 95 %. This paper proposed a reaction rate model, and got a rutile chlorination rate formula, which is generally consistent with the experimental data. For the TiO2-C-C12 system, the reaction rate is dependent on the initial radius of rutile particle, density, and the partial pressures of C12. From 900 to 1,000 ℃, the apparent activation energy is 10.569 kJ.mo1-1, and the mass diffu- sion is found to be the main reaction-controlling step. The expression for the chlorine reaction rate in the C-C12 sys- tem is obtained, and it depends on the degree of reaction, the partial pressure of C12, and the size of rutile particle.