Organic Gases in Fluid Inclusions of Ore Minerals and Their Constraints on Ore Genesis:A Case Study of the Changkeng Au-Ag Deposit,Guangdong,China

The newly discovered Changkeng Au-Ag deposit is a new type of sediment-hostedprecious metal deposit. Most of the previous researchers believed that the deposit was formed bymeteoric water convection. By using a high vacuum quadrupole gas mass spectrometric system, ninelight hydrocarbons have been recognized in the fluid inclusions in ore minerals collected from theChangkeng deposit. The hydrocarbons are composed mainly of saturated alkanes C_(1-4) and unsaturatedalkenes C_(2-4) and aromatic hydrocarbons, in which the alkanes are predominant, while the contentsof alkenes and aromatic hydrocarbons are very low. The sum alka/sum alke ratio of most samples ishigher than 100, suggesting that those hydrocarbons are mainly generated by pyrolysis of kerogens insedimentary rocks caused by water-rock interactions at medium-low temperatures, and themetallogenic processes might have not been affected by magmatic activity. A thermodynamiccalculation shows that the light hydrocarbons have reached chemical equilibrium at temperatureshigher than 200 deg C, and they may have been generated in the deep part of sedimentary basins(e.g., the Sanzhou basin) and then be transported by ore-forming fluids to a shallow position of thebasin via a long distance. Most of the organic gases are generated by pyrolysis of the type IIkerogens (kukersite) in sedimentary host rocks, only a few by microorganism activity. Thecompositions and various parameters of light hydrocarbons in gold ores are quite similar to those insilver ores, suggesting that the gold and silver ores may have similar metallogenic processes.Based on the compositions of organic gases in fluid inclusions, the authors infer that the Changkengdeposit may be of a tectonic setting of continental rift. The results of this study support fromone aspect the authors' opinion that the Changkeng deposit is not formed by meteoric waterconvection, and that its genesis has a close relationship with the evolution of the Sanzhou basin,so it belongs to the sedimentary hot brine transformed deposit.

Fluid Inclusion Studies of Ore and Gangue Minerals from the Piaotang Tungsten Deposit, Southern Jiangxi Province, China

The Piaotang deposit is one of the largest vein-type W-polymetallic deposits in southern Jiangxi Province,South China.The coexistence of wolframite and cassiterite is an important feature of the deposit.Based on detailed petrographic observations,microthermometry of fluid inclusions in wolframite,cassiterite and intergrown quartz was undertaken.The inclusions in wolframite were observed by infrared microscope,while those in cassiterite and quartz were observed in visible light.The fluid inclusions in wolframite can be divided into two types:aqueous inclusions with a large vapor-phase proportion and aqueous inclusions with a small vapor-phase ratio.The homogenization temperature(Th)of inclusions in wolframite with large vapor-phase ratios ranged from 280℃ to 390℃,with salinity ranging from 3.1 to 7.2 wt%NaCl eq.In contrast,the Th values of inclusions with small vapor-phase ratios ranged from 216℃ to 264℃,with salinity values ranging from 3.5 to 9.3 wt%NaCl eq.T_(h) values of primary inclusions in cassiterite ranged from 316℃ to 380℃,with salinity ranging from 5.4 to 9.3 wt%NaCl eq.T_(h) values for primary fluid inclusions in quartz ranged from 162℃ to 309℃,with salinity values ranging from 1.2 to 6.7 wt%NaCl eq.The results show that the formation conditions of wolframite,cassiterite and intergrown quartz are not uniform.The evolutionary processes of fluids related to these three kinds of minerals are also significantly different.Intergrown quartz cannot provide the depositional conditions of wolframite and cassiterite.The fluids related to tungsten mineralization for the NaCl-H_(2)O system had a medium-to-high temperature and low salinity,while the fluids related to tin mineralization for the NaCl-H_(2)O system had a high temperature and medium-to-low salinity.The results of this study suggest that fluid cooling is the main mechanism for the precipitation of tungsten and tin.

Study on Epithermal Gold Mineralization System at Shwebontha Prospect,Monywa Copper-Gold Ore Field,Central Myanmar

The Shwebontha prospect area is situated in the Central Volcanic Belt,central Myanmar,where the well-known Sagaing Fault serves as its eastern boundary.This study aims to document key the mineralogy,host rock geochemistry and ore mineralizing fluids.The mineralization,hosted by Upper Oligocene to Middle Miocene rhyolites,displays a strong lithological control.Mineralization is characterized by gold-bearing silicified massive ore and chalcedonic quartz veins in which sulfides are clustered and disseminated not only in quartz gangue but also in rhyolite host rocks.The significant ore minerals in the mineralized veins include pyrite,sphalerite,galena,chalcopyrite,and gold.Common hydrothermal alterations such as silicic,argillic and propylitic alteration types are recognized.According to the fluid inclusion data and interpretation,ore mineralizing fluids in the research area are characterized by formation temperatures of 260-280℃ and salinity of 0.35-2.41%wt.NaCl eq.respectively.Mixing of hydrothermal fluids was generally considered to be an effective mechanism for ore transport and deposition.

A New Potential Caledonian–Indosinian Ore Concentration Area:Evidence from Diagenesis and Mineralization Ages of the Miao'ershan–Yuechengling Region

Objective The Miao＇ershan-Yuechengling composite granite, located in northern Guangxi at the western section of the Nanling Range, is a multi-period and multi-stage composite pluton with an exposed area of more than 3000 km2 （Fig. 1）. Paleozoic and Proterozoic strata are exposed around it, and magmatic activities mainly occurred during the Caledonian and Indosinian periods. Till now, more than one hundred W-Sn-Mo-Pb-Zn-Cu （U） deposits and ore occurrences have been discovered along the inner and outer contact zones of this granite. Through recent years＇ research, we infer that this area is not only a preferred area for studying granite and mineralization in Caledonian and lndosinian periods, but also a potential Caledonian- lndosinian ore-concentrated area.

Magmatic Evolution and Mineralization of Porphyry Copper-Gold Deposits in the Duolong Ore Concentration Area, Tibet

The Bangong Lake-Nujiang River metallogenic belt is located between the Qiangtang Block and Lhasa Block, and the Duolong ore concentration area is located in the western section of the Bangong Lake-Nujiang River metallogenic belt. Till now, several large and super large copper-gold deposits, such as Duobuza, Bolong, Dibaonamugang, Naruo and Rongna deposits have been discovered in this area, mainly porphyry copper-gold ones.

Metallogeny and Emplacement Conditions of Continental Terminal 3 (Ct3) Iron Formations of the Niamey Region (Western Niger)

This study aims to characterize the different lithofacies of the Ct3 formation in the Niamey region, and to determine the distribution of major and trace elements, in order to highlight the conditions for the establishment of iron mineralization. A lithological column, synthesizing sections of selected outcrops in the vicinity of Niamey, was produced. The chemical compositions of the selected samples were determined by X-ray fluorescence (XRF) spectrometry. Microscopic analysis of the thin sections determined the gœthitic nature of the oolitic iron ore. The oolites show a quartz, limonitic or gœthitic nucleus. Sometimes the nucleus is absent. From a morphoscopic point of view, two types of oolites have been distinguished: spherical-shaped and ellipsoidal-shaped oolites. The oolites are either contiguous or disseminated, as the case may be, in a limonitic to goethitic cement or in a fine sandstone matrix. The larger oolites (pisolites) are relatively friable. They reflect the influence of a relatively turbulent to submerged environment. The hardground of the iron mineralized horizons are covered by quartz grains. They are indicative of a submerged or emergent environment. X-ray fluorescence analysis shows high Fe2O3 contents (50% to 80%) and variable contents of major elements SiO2, Al2O3, TiO2, MnO, MgO, CaO, K2O and P2O5 associated with certain trace elements such as Th, U, V, Y, Zn, Zr and As. The results of the study are an important tool for decision-makers to adopt effective prevention/remediation measures for groundwater contamination in the Continental terminal aquifer systems.

Swelling of clay minerals in ammonium leaching of weathered crust elution-deposited rare earth ores

The effect of hydrated radius, cation valence, pH and solution concentration on the zeta potential of clay minerals was investigated, and the relation between zeta potential of clay minerals and swelling was discussed in different leaching agents as well. The results show that the zeta potential of clay minerals decreases with the hydrated ionic radius increasing. It could be seen that the zeta potential of the clay minerals in AICl3 solution is positive,whereas that in NH4C1, KCl and MgCl2 solution is negative. And the zeta potential of clay minerals increases with the cation valence increasing. Moreover, the zeta potential of clay minerals decreases with the solution pH increasing,whereas that increases with the solution concentration increasing in different ammonium solutions. In addition,the swelling of clay minerals decreases while the zeta potential of clay minerals increasing in different ammonium solutions. The ability of compound ammonium to inhibit the swelling of clay minerals is lower than that of single ammonium solution.

Ministry of Land and Resources: To Strengthen Reserve of Key Ore Mines for Strategic Minerals

The Ministry of Land and Resources formally promulgated‘Outline of the'Thirteenth Five Year Plan'for Land and Resources’on August14.The'Outline'pointed out to,reinforce prospecting and protection of key mineral resources;improve orefield reserve mechanism,strengthen reserve of key orefields for strategic minerals such as tungsten,rare earth。

A FAST STOCKPILE SIMULATION ENGINE AND ITS APPLICATION IN MINERAL ORE HANDLING

This paper presents structures and principles of a fast stockpile simulation engine that enhances automatic material process by providing accurate digital information of material quality distribution within stockpiles.Compared with traditional measurementbased approaches,our simulation technology reduces operation cost by eliminating frequent physical measuring;improves operation accuracy through all-time whole-area contour simulation(instead of measuring a few positions of material layers now and then);and speeds the process through fast simulation and instant response to quality information query.Based on simplified grain dynamics and cellular automata models,the technology can achieve real-time/super-real-time simulation,which is critical to be adopted by the industry.Application of the technology in analyzing mineral ores handling is also discussed.