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Studies of VHMS-related alteration: geochemical and mineralogical vectors to ore. CODES/AMIRA Project P.439. Report 5, October 1997.


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Huston, DL, Callaghan, T, Beckton, J, Wyman, B, Gifkins, CC, Allen, RL, Large, RR, Blake, MD, Yang, K, Huntington, JF, Gemmell, JB, Fulton, R, Herrmann, W, McPhie, J and Doyle, MG 1997 , Studies of VHMS-related alteration: geochemical and mineralogical vectors to ore. CODES/AMIRA Project P.439. Report 5, October 1997..

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This fifth report on the project presents results of
research in the five-month period between May and October 1997.

The content reflects the multi-disciplinary approach to studying VHMS-related alteration systems with major contributions on the factors which control "background" diagenetic alteration, the discrimination between diagenetic and ore-related hydrothermal alteration, and specific alteration studies on a diverse range of deposits in Tasmania and North Queensland.

• David Huston presents geochemical data from the Western Tharsis disseminated pyrite-chalcopyrite deposit suggesting that Ba and Mn could be weathering resistant pathfinder elements to detect the outer alteration zones, K2O depletion could indicate close proximity to ore, and As, Bi and Se could be useful vectors to ore lenses within the barren pyritic envelope.
• Tim Callaghan and Jason Beckton report on their new research into the Mt Julia and Henty gold deposits which are associated with extensive, stratabound, rather VHMS-like alteration zones adjacent to a major fault. However, some aspects of alteration, such as extreme silicification, mobility of Al203 and apparent overprinting of earlier pervasive carbonate and albite alteration, show these to be distinct from other deposits in the Mt Read Volcanics.
• Preliminary trace element results from the White Spur step out traverses indicate a coincident anomaly in Ag, As, Sb, Cd, Mo and Tl in altered and weakly mineralised volcaniclastic breccia at the base of the White Spur Formation, a few hundred metres north of drill hole MRl.
• In her report on background alteration in the Mt Black Volcanics, east of Rosebery, Cathryn Gifkins highlights the influence of volcanic facies and primary composition on diagenetic alteration, and shows how a complex pile of variably permeable and glassy felsic volcanics has been modified to a diverse and patchy arrangement of alteration types.
• Rod Allen texturally pursues diagenetic alteration into the confusion of the Rosebery-Hercules ore forming system and emerges with a convincing alteration sequence. It has implications for large porosity and density changes during diagenesis and for regional scale exploration targeting.
• Initial interpretation, by Ross Large and Mike Blake, of microprobe and spectrographic data on mineral chemistry of Rosebery carbonates and muscorite, shows potential for these techniques in alteration mapping and exploration vectors.
• The latest appraisal results from Hellyer, by Bruce
Gemmell and others, indicate that the PIMA portable infrared spectrometer also has applications in mapping of alteration intensity, particularly in recognition of Fe-Mg rich muscovites in alteration zones proximal to ore.
• Cliff Stanley presents the Pearce Element Ratio approach to interpretation of the Hellyer alteration system.
• Mark Doyle discusses the latest geochemical data from the alteration zones surrounding the synvolcanic, sub-seafloor replacement Cu-Au deposits at Highway-Reward.
• Wally Herrmann presents for discussion, a draft outline of the format for the P439 final report.

Item Type: Report (Technical Report)
Authors/Creators:Huston, DL and Callaghan, T and Beckton, J and Wyman, B and Gifkins, CC and Allen, RL and Large, RR and Blake, MD and Yang, K and Huntington, JF and Gemmell, JB and Fulton, R and Herrmann, W and McPhie, J and Doyle, MG
Publisher: CODES/AMIRA
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