The Geochemical Study Of An Intrusion Related Bismuth-Gold Deposit In The Tengchong-Lianghe W-Sn Metallogenic Belt

The mechanism of Bi-melt scavenging of gold has previously been proposed to explain the common association between gold and bismuth seen in many ore deposits, and involves the scavenging of gold from hydrothermal fluid by liquid bismuth. Here, textural relationships and temperature and chemical conditions of mineralization at the bismuth-gold-silver-tungsten-molybdenum polymetalic prospect in northeastern Burma are analyzed to investigate whether the liquid bismuth collector model can explain gold accumulation at this prospect. We have used scanning electron microscope combined with EDS and electron microprobe to identify bismuthtellurium-sulfur ore minerals and to study the textural relationships between minerals. The resluts show that the Au-Bi-Te-S minerals consist of gold, native Bi, joseite-A（Bi₄TeS₂）, joseite-B（Bi₄Te₂S）, ikunolite（Bi₄S3_） with less amount of bismuthinite（Bi₂S₃）, hedleyite（Bi₇Te₃）. The correlation coefficient of Au and Bi is 0.792, which proves the closely paragenetic relationship between bismuth minerals and gold mineralization. Moreover, Au also correlate strongly with Mo,W,Te and Sb. Gold and Bi-Te-S phase minerals generally disseminated in the cleavage and fractures of molybdenite. Two distinct type of metallogenic associations have been classfied here, including Fe-Cu massive sulfides and Au-Bi-Mo-W-Ag-Te elemental associations, which are related to hydrothermal fluids. The striking aspect that the widespread occurrence of native gold and bismuth minerals together with molybdenite distributed in the muscovite-chlorite belt, which is resulting from fluid-rock interaction, may indicating that the changing of redox state and decreasing of fs2, pH value in hydrothermal fluids lead to the precipitation of bismuth liquids. The bismuth melts formed during this process can collect Au from ambient solutions to form Bi-Au ploymetalic melt, then depositing under the decreasing of temperature.We proposed the bismuth-gold polymetallic prospect as an intrusion related gold deposit, considering the metal assemblages of gold with Bi, W, Mo, Te, Sb, low sulfide mineral content, the limited muscovite-chlorite-carbonate（?） fluid-rock alteration; tectonic setting and location within a magmatic province with identified tungsten/tin deposits.