BACKGROUND The Xianghualing mining area in Hunan Province is an important part of the east-west tectonic-magmatic-metallogenic belt in the Nanling area.The ore-forming geological conditions in the mining area are superior, and it is famous for its many types of deposits and complex types of minerals.The tin-lead-zinc deposit in the Xianghualing mining area is a very important polymetallic deposit in the Nanling metallogenic belt.The ore types are mainly cassiterite sulfide tin ore, tin-lead-zinc ore and sulfide lead-zinc ore.Tin, lead and zinc are very important nonferrous metal elements.The abundance and variation characteristics of these three elements can reflect the regional metallogenic conditions, indicate the existence of deposits or mineralization, and are the important basis for studying the metallogenic model, deepening the understanding of the genesis of the deposit, and identifying the metallogenic control factors.Therefore, it is very necessary to accurately determine the content of tin, lead and zinc in the tin, lead and zinc deposits in the Xianghualing mining area, and it is important to study the regional metallogenic conditions The geological characteristics of the deposit, the occurrence state of elements, mineral processing and comprehensive utilization of non-ferrous metal minerals are of great significance.However, the average grades of tin, lead and zinc in the deposit are percentage contents and tin itself is a refractory element.Conventional open acid dissolution or closed acid dissolution in the dissolution of high content of tin, lead and zinc in the ore will have the disadvantages of incomplete digestion and easy precipitation of the solution, resulting in serious low determination results.However, alkali fusion is more capable of decomposing minerals than acid dissolution.As long as the appropriate alkali fusion reagent, temperature and time are optimized, some high content of inorganic elements, even insoluble elements, can be completely decomposed, which is an ideal method of mineral decomposition pretreatment.

OBJECTIVES To rapidly and accurately determine the concentrations of tin, lead and zinc in high contents of tin, lead and zinc samples of a tin-lead-zinc deposit in the Xianghualing mining area, Hunan Province.

METHODS Inductively coupled plasma-optical emission spectrometry (ICP-OES) with alkali fusion was used to determine the levels of tin, lead and zinc.The selection of alkali fusion reagent, reagent dosage, alkali fusion temperature and time as well as the plasma excitation conditions, element spectral lines, button background position and other instrumental determination conditions were optimized.The effects of three kinds of fluxes: sodium hydroxide, anhydrous sodium carbonate and sodium peroxide were compared.

RESULTS The measured value of tin was greatly affected by the alkali flux.Under the flux of sodium hydroxide or anhydrous sodium carbonate, the measured value of tin was low, while the measured value of tin was consistent with the standard value under the flux of sodium peroxide.Based on the comparison of the effects of various fluxes on the analysis results, sodium peroxide was selected as the flux, melting at a constant temperature of 750℃ for 20 minutes, and acidification with 20mL of hydrochloric acid after 30mL of boiling water extraction to ensure the complete decomposition of the sample.The calibration series was prepared with blank alkali melt solution as the medium, so that the calibration series matched the sample matrix and eliminated the influence of matrix interference.The national first-class geochemical reference materials were used for method quality evaluation, and the results showed that the absolute value of the logarithmic difference between the measured value and the certified value of the reference material was less than 0.04.The detection limits of the method for tin, lead and zinc were 13.60μg/g, 36.45μg/g and 53.83μg/g, respectively.The precision of the method was better than 8%.The determination range of the calibration curve was between 0 to 100μg/mL.

CONCLUSIONS Due to the use of alkali fusion method and blank alkali fusion solution as the standard preparation medium, this method is suitable for the determination of high contents of tin, lead and zinc in cassiterite-sulfide type tin ores, tin-lead-zinc ores, and sulfide type lead-zinc ores, and it has good application prospects.At present, this method has been successfully applied to the analysis of actual samples in the Xianghualing mining area, Hunan Province, with satisfactory results.