Authors / CoAuthors
Abstract
In addition to typical VHMS deposits, the ~3240 Ma Panorama district contains contemporaneous greisen- and vein-hosted Mo-Cu-Zn-Sn mineral occurrences that are hosted by the Strelley granite complex, which drove VHMS circulation, making this district a natural laboratory to assess the role of magmatic-hydrothermal fluids in VHMS hydrothermal systems. High-temperature alteration zones in volcanic rocks below the VHMS deposits are dominated by quartz-chlorite±albite assemblages, with lesser quartz-sericite±K-feldspar assemblages, typical of VHMS systems. In contrast, the assemblages associated with granite-hosted greisens and veins, which do not extend into the overlying volcanic pile, include quartz-topaz-muscovite-fluorite and quartz-muscovite(sericite)-chlorite-ankerite. Fluid inclusion and stable isotope data suggest that the greisens formed from high temperature (~590°C), high salinity (38-56 wt % NaCl equiv) fluids with high densities (>1.3 g/cm3) and high -18O (9.3±0.6-). These fluids are compatible with the characteristics of magmatic fluids evolved from the Strelley granite complex. Fluids in the volcanic pile (including the VHMS ore-forming fluids) were of lower temperature (90-270°C), lower salinity (5.0-11.2 wt % NaCl equiv), with lower densities (0.88-1.01 g/cm3) and lower -18O (-0.8±2.6-), compatible with evolved Paleoarchean seawater. Fluids that formed quartz-chalcopyrite-sphalerite-cassiterite veins, which are present within the granite complex near the contact with the volcanic pile, had intermediate in temperature and isotopic compositions (T = 240-315°C; -18O = 4.3±1.5-) and likely indicate mixing between the two end-member fluids. Evidence of mixing between evolved seawater and magmatic-hydrothermal fluid within the granite complex, together with the lack of evidence for a magmatic component in fluids from the volcanic pile, suggest partitioning of magmatic-hydrothermal from evolved seawater hydrothermal systems in the Panorama system.
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nonGeographicDataset
eCat Id
69969
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Cnr Jerrabomberra Ave and Hindmarsh Dr GPO Box 378
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Keywords
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- External Publication
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- AU-WA
- Australian and New Zealand Standard Research Classification (ANZSRC)
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- Earth Sciences
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- Published_Internal
Publication Date
2009-12-16T00:00:00
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geoscientificInformation
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[-21.5, -21.0, 119.0, 119.25]
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