A synthetic fluid inclusion study of copper solubility in hydrothermal brines from 525 to 725 °C and 0.3 to 1.7 GPa

Alistair C. Hack*, John A. Mavrogenes

*Corresponding author for this work

    Research output: Contribution to journalArticlepeer-review

    45 Citations (Scopus)

    Abstract

    Fluid inclusions were synthesized in a piston-cylinder apparatus under mineral-buffered conditions over a range of Cl concentration (0.29 to 11.3 mol kg-1), temperature (525 to 725 °C), and pressure (0.3 to 1.7 GPa). All fluids were buffered by the mineral assemblage native copper + cuprite + talc + quartz. In situ fluid composition was determined by analysing individual fluid inclusions by LA-ICPMS and independently analysing the quench solution. The solubility data provide basic information necessary to model the high temperature behaviour of Cu in magmatic-hydrothermal systems. Copper concentrations up to ∼15 wt% were measured at 630 °C and 0.34 GPa. These results give an upper limit for Cu in natural fluids and support field-based observations of similar high Cu concentrations in fluids at near-magmatic conditions. Experimental evidence indicates that Cu+ may form neutral chloride complexes with the general stoichiometry CuCl (HCl)n - 10 with n up to 4, though n ≤ 2 is typical for the majority of the experimental conditions. At high pressure (>∼0.5 GPa) there is evidence that hydroxide species, e.g., CuOH0, become increasingly important and may predominate over copper(I)-chloride complexes. The roles of fluid mixing, cooling and decompression in ore-forming environments are also discussed.

    Original languageEnglish
    Pages (from-to)3970-3985
    Number of pages16
    JournalGeochimica et Cosmochimica Acta
    Volume70
    Issue number15
    DOIs
    Publication statusPublished - 1 Aug 2006

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