Mantle, crustal and atmospheric noble gases in Ailaoshan Gold deposits, Yunnan Province, China

P. G. Burnard, R. Hu, G. Turner, X. W. Bi

    Research output: Contribution to journalArticlepeer-review

    Abstract

    Helium and argon isotopic and elemental compositions of fluids released by crushing pyrite grains are reported from the Ailaoshan Gold Province, China. The province is a series of gold deposits hosted on a 200-km segment of a major normal fault formed during Eocene extension. The deposits have been well characterised using conventional geochemical and microthermometric techniques, the results of which are consistent with a predominantly high temperature 'magmatic' fluid present in the ore minerals. In contrast, analyses of noble gases from three gold deposits demonstrate the palaeofluids were a mixture between a mantle-derived, magmatic fluid and two different low temperature fluids similar to modern groundwaters. The specific isotopic and abundance characteristics of helium and argon allow unequivocal identification of both a mantle-derived component and a surface-derived component to these fluids. The magmatic fluid dominates deposits from the northern end of the fault. The second groundwater is present only in deposits in the south of the province. By assuming fluid inclusion homogenisation temperatures in coexisting quartz are representative of fluid temperature, 3He/heat ratios can be estimated. The 3He/heat ratios vary systematically along the fault, from ~ 30 X 10-12 cm3 STP J-1 in the northern deposits to
    Original languageEnglish
    Pages (from-to)1595-1604
    Number of pages9
    JournalGeochimica et Cosmochimica Acta
    Volume63
    Issue number10
    Publication statusPublished - May 1999

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