Authors / CoAuthors
Huston, D.L.
Abstract
The Western Tharsis deposit, located in the Cambrian Mount Read Volcanic Belt of western Tasmania, is one of 22 mainly Cu-Au deposits in the Mount Lyell district. Although Western Tharsis is characterized mainly by disseminated pyrite-chalcopyrite like most other deposits in the Mount Lyell district, it also contains bornite-rich ores characteristic of a second, less common type of deposit in the Mount Lyell district. The deposit is stratabound and occurs within intermediate and felsic volcanic rocks belonging to the Central Volcanic Complex. Alteration is developed symmetrically around the ore zone, with an ore-bearing core characterized by a quartz-chlorite?sericite assemblage. The core is enveloped by a pyritic quartz-pyrophyllite?topaz?fluorite?zunyite?woodhouseite "advanced argillic" assemblage with local bornite-bearing ore zones. This zone, in turn, is enveloped by a pyritic quartz-sericite assemblage and then by an outermost quartz-chlorite-carbonate-sericite?albite assemblage that lacks pyrite. The bornite-related pyrophyllite-bearing assemblage is more characteristic of ?high sulfidation? epithermal rather than VHMS-related alteration assemblages. The close relationship of this assemblage to the quartz-chlorite?sericite assemblage associated with disseminated pyrite-chalcopyrite suggests that the bornite and chalcopyrite assemblages formed as two stages of one mineralizing event. The chalcopyrite-pyrite ore zone is characterised by extreme enrichment (relative to regional background) in As, Bi, Ce, Cu, Mo, Ni, S and Se. With the exception of Mo, these elements are also enriched, but at a much lower level, in the pyrite-bearing advanced argillic and sericitic halos. Positive Eu anomalies and pronounced depletion in K, Cs, Mg, Be, Ga, Rb, Y, MREE and HREE are associated with the advanced argillic assemblages. The outermost carbonate-bearing halo is highly enriched in C, Ca and Mn, and weakly enriched in Zn and Tl. The dispersion patterns and alteration assemblages observed at Western Tharsis are quite unlike those of Zn-Pb-rich volcanic-hosted massive sulfide (VHMS) deposits in western Tasmania. Rather, the dispersion patterns observed at Western Tharsis are more akin to those surrounding porphyry Cu deposits and related acid-sulfate Cu-Au deposits. Geological relationships and radiogenic isotope data may suggest an Ordovician timing for Mt Lyell Cu-Au mineral deposits.
Product Type
nonGeographicDataset
eCat Id
36305
Contact for the resource
Custodian
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Cnr Jerrabomberra Ave and Hindmarsh Dr GPO Box 378
Canberra
ACT
2601
Australia
Keywords
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- External PublicationAbstract
- ( Theme )
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- economic geology
- ( Theme )
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- geochemistry
- ( Theme )
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- mineral deposits
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- AU-TAS
- Australian and New Zealand Standard Research Classification (ANZSRC)
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- Earth Sciences
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- Published_Internal
Publication Date
2001-01-01T00:00:00
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geoscientificInformation
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Unknown
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Extents
[-42.0, -41.0, 144.0, 145.5]
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