Distribution Characteristics Of Tellurium In Gold Deposits And Its Relationship With Gold Mineral Assemblage

Telluride gold deposit,characterized by enrichment of tellurides,is an important kind of gold deposits.In this paper,gold deposits with tellurium(Te)-gold(Au)minerals are referred as gold-telluride deposits.The study of telluride gold deposits plays an important role in the understanding of paragenetic association of elements during the formation of gold deposits,mining and mineral processing of gold deposits,and Te resource comprehensive utilization.We take some typical telluride gold deposits as example,such as Sandaowanzi gold deposit in Heilongjiang Province,Dongping,Jinchangyu and Yuerya gold deposits in Hebei Province,and Guilaizhuang gold deposit in Shandong Province.Among these deposits,Sandaowanzi,Guilaizhuang and Dongping deposits are gold-telluride deposits with the occurrence of Te-Au minerals.For comparision,we study the gold deposits without tellurides,such as Baiyun deposit in Liaoning Province,Zhilingtou deposit in Zhejiang Province,Yangshan deposit in Gansu Province,Laozuoshan and Wulaga deposits in Heilongjiang Province,Jiapigou deposit in Jilin Province,and Zijinshan deposit in Fujian Province.Finally,we summarize the distribution characteristics of Te in different type of gold deposits and calculate the relative content of atoms of main metallogenic elements(Au,Ag,Bi,Sb,Pb,Cu and Hg)and mineralizer(S and Te),and then investigate the relationship between the contents and element associations in hydrothermal ore-forming system.On the basis of geochemical affinity and ratio of number of atoms in ore-forming system,we clarify the origin of Te-Au minerals in gold deposits.Chemical analysis results show that Te contents in gold ores from telluride gold deposits are generally higher than those of gold deposits without tellurides.Similarily,calculation results of the relative atomic contents of the main metallogenic elements and mineralizer show that the relative contents of Te atom in gold ores from telluride gold deposits are generally higher than those of gold deposits without tellurides.The Sandaowanzi deposit has the highest relative atomic content of Te,and is followed by Guilaizhuang,Dongping,Yuerya,and Jinchangyu deposits.The variations of elemental relative atomic content in different type of gold deposits are large for Bi and Hg,moderate for Sb,Pb and Cu,and non-significant for Ag.The relationship between the sulfide content and Te atom number indicates that there are Te-Au minerals in gold deposits with high Te and low S(such as Sandaowanzi and Guilaizhuang gold deposits),and there maybe Te-Au mminerals in deposits with high Te and S(such as Dongping deposit),or maybe not(such as Yuerya and Jinchangyu deposits),while there is almost no Te-Au mineral in gold deposits with low S.The hydrothermal ore-forming system is multi-element and polyphase system,and the formation of minerals is controlled by geochemical affinity,elemental contents and physico-chemical conditions.According to Gibbs free energy of formation of minerals at different temperatures,the thiophilic properties of Bi,Sb,Pb,Cu,and Hg are stronger than their affinities to Te,and it is quite the opposite for elements Ag and Au.At temperatures between 150 °C and 350 °C,the affinity degrees of these elements to Te can be sorted as follows: Pb> Ag> Hg> Cu> Bi> Sb> Au.At 150 °C,the order is Pb> Cu> Sb> Hg> Bi> Ag,and at temperatures between 250 °C and 350 °C,Cu> Pb> Sb> Ag> Hg> Bi.Our researches show that the requirement for the formation of Te-Au minerals in the ore-forming system of telluride gold deposits is that a certain amount of Te should be left when associations of elements S and Te with metallogenic elements expect Au are completed.Because the affinity of Bi to S is weakest among the above elements,when S is insufficient in the ore-forming system,the primarily remains will be element Bi.In addition,the affinity of Bi to Te is higher than that of Au.Therefore,the formation of Te-Au minerals is dominantly controlled by element Bi.In the ore-forming system of gold deposits with high Te and low S(such as Sandaowanzi and Guilaizhuang gold deposits),the relative contents of Te and Au atoms are very high.A large amount of Te will be left after association of metallogenic elements with elements of S and Te,which makes it possible for Au to combine with Te to form Te-Au minerals with a relatively small amount of matural gold.In the oreforming system of gold deposits with high Te and S,sulfides are the main metallic minerals.It appears to be that the relative contents of Te atom of these deposits will not be higher than that of the Sandaowanzi deposit,which will lead to a decline in the amount of generated tellurides.In Dongping gold deposit,almost all of the metallogenic elements are bound by S to form sulfides,therefore,Te can combine with Au to form Te-Au minerals.In addition,a large amount of natural gold is formed because Te is insufficient in the ore-forming system.The occurrence of natural Bi in the Jinchangyu and Yuerya gold deposits indicates that the relative atomic content of metallogenic elements is higher than that of the anions.Therefore,there are Te-Bi minerals and natural gold in these deposits.