Occurrence And Distribution Of Indium In The Dulong Zinc-tin Deposit In Southeastern Yunnan

Dulong superlarge zinc tin deposit in southeastern Yunnan is the largest indium resource producing area in China.At present,the occurrence,distribution and formation of indium in the ore are still unclear,which limits the resource exploration and evaluation and deep development and utilization.In this paper,on the basis of data collection,field investigation,sampling and test analysis have been carried out systematically,and detailed petrological and geochemical studies have been carried out on the indium bearing ores in Dulong deposit(1)The results of chemical analysis of Dulong zinc tin ore concentrate show that indium mainly occurs in zinc concentrate and copper concentrate,while the content of indium in iron sulfur concentrate and tin concentrate is very low.This shows that the main carrier mineral of indium is marmatite,a small amount of which occurs in chalcopyrite,but rarely in cassiterite.(2)In the main silicate ore bodies in the mining area,the proportion of indium is relatively high,and the proportion of main minerals(tin and zinc)is also high.The indium in the ore mainly occurs in skarn minerals(wet skarn belt),and the cassiterite sulfide ore is the main carrier.The results of microscopic observation show that the degree of automorphism of in bearing Sphalerite in all kinds of skarn is high,and it is characterized by disseminated or linear filling along fractures and cleavages.(3)Energy spectrum CT micro chemical composition analysis shows that the content of indium in different measuring points of marmatite changes little,and the distribution of indium in marmatite is relatively uniform.It can be concluded that indium should occur in the form of incomplete isomorphism in sphalerite.(4)The REE total amount and REE distribution pattern of the indium bearing skarn type ore show the characteristics of right leaning LREE enrichment type and EU negative anomaly,which is consistent with the REE composition characteristics of Laojunshan granite.It shows that the metal minerals including indium in the skarn in the area are mainly derived from granite and have clear granite affinity.(5)The statistical characteristics of chemical composition of indium bearing ores show that the indium content gradually decreases from cassiterite sulfide ore to wet skarn ore and to dry skarn ore.At the same time,there is a positive correlation between indium,tin and zinc,and the positive correlation between indium and tin is more obvious,that is,the higher the content of tin,the higher the content of indium.Therefore,the enrichment and mineralization of indium and tin in sphalerite show the rule of continuous occurrence and spatial coexistence.(6)The enrichment and mineralization of indium in the Dulong Zn Sn deposit are mainly controlled by the changes of the physicochemical conditions of the Sn rich and Zn bearing hydrothermal solution from the granite.It can be said that the enrichment and mineralization of indium in the area is also the product of crystallization differentiation of early Yanshanian(Late Cretaceous)granites,and they were enriched together with tin,zinc and other metals in the stage of wet skarn and formed successively.