Research On Silver Manganese Minerals In The Xiang Guang Manganese Silver Deposit In Hebei And Its Synthetic Experiments

Manganese-silver ore is one of the important resource of silver.Due to the coexistence of silver with manganese,a large amount of silver resources have not been propeity studied and utilized.At present,there are few publications on manganese-silver minerals,which urgently need to be enriched.Taking Xiangguang Mn-Ag Deposit in Hebei Province as the research object,this study used a combination of multiple modern testing techniques to determine the mineralogical characteristics and crystal chemical characteristics of the silver-bearing manganese minerals produced in Hebei Xiangguang Mn-Ag Deposit,and discussed the occurrence state of silver in the silver-bearing manganese minerals.Synthetic experiment was carried out to explore the physical and chemical conditions that affect the synthesis and transformation of the silver-bearing manganese minerals,so as to provide theoretical support for the further exploitation and utilization of such minerals.Based on the project of the Youth Science Natural Foundation,Study on the Occurrence State and Formation Mechanism of “Invisible Silver” in Mn-Ag Deposit,this paper comprehensively applied multiple modern mineralogical testing techniques on the basis of detailed field geological investigation and carried out a systematic study and explanation on basic geology,ore deposits,mineralogy,geochemistry and laboratory synthesis of minerals respectively.The main results are as follows:(1)It was found that manganese-silver oxides are the dominant ore minerals in Hebei Xiangguang Mn-Ag Deposit.Manganese minerals mainly consist of chalcophanite,cryptomelane,coronadite,Rancieite,pyrolusite,etc.Silver minerals mainly include bromchlorargyrite,iodargyrite,argentite and so on.(2)Silver is mainly occurred in the oxidized manganese-silver ores of Hebei Xiangguang Mn-Ag Deposit in two forms,independent silver minerals(bromchlorargyrite,iodargyrite,argentite,etc.)and isomorphism.The latter takes the lead,which is mainly concentrated in cryptomelane with large pore channel structure and K-Ca-Ag manganese minerals.(3)Using potassium(sodium)hydroxide and manganese sulfate as raw materials,potassium(sodium)type birnessite could be prepared by aeration under alkaline conditions.Silver-bearing manganese oxides with pore channel structure were further formed by ion exchange with silver ions under hydrothermal conditions.The XRD result of the experimental products tallied with that of the natural manganese minerals.In condition experiment,the increase of pressure,the increase of silver ion concentration and the increase of temperature can promote the transformation of the precursor birnessite to the pore channel type silver-bearing manganese mineral,but the increase of time has little effect on the experimental results.(4)The crystal morphology of the synthesized samples is fibrous,about 1-1.5?m in length and more than 10 nanometers in width.The interplanar spacing of the synthesized samples coincided with that of the natural cryptomelane.EDS showed that there was silver composition,but no elemental silver was observed in the transmission electron microscope.So it is inferred that silver exists in the pore channel structure of manganese oxide in the form of ions.