Two lithogeochemical approaches to the identification of alteration patterns at the Elura Zn-Pb-Ag deposit, Cobar, New South Wales, Australia: Use of Pearce Element Radio analysis and Isocon analysis

Michael Whitbread, Cara Moore

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    11 Citations (Scopus)

    Abstract

    Lithogeochemical approaches to the identification of ore-related alteration can be obscured by closure effects and/or pre-existing lithological variations. Two mass balance approaches that can address these problems are Pearce Element Ratio analysis (PER) and Isocon analysis (IA). Both approaches have been applied to sedimentary rocks hosting the Elura ore-body, north of Cobar, in central-west New South Wales, Australia. Elura is an epigenetic, zinc–lead–silver deposit, (45 Mt with 8.5% Zn, 5.3% Pb, and 69 ppm Ag), hosted within Devonian siltstone–sandstone turbidites of the Cobar Basin. The ability of PER and IA to identify alteration at Elura and to navigate towards ore within altered zones is evaluated.

    PER identified mineralogical controls on calcium, carbonate, potassium and aluminium. Molar Ca/Ti v. C/Ti plots segregate calcite-bearing background samples from iron–magnesium–carbonate altered rocks closer to ore. Molar K/Ti v. Al/Ti and K/Ti v. (Al–Na)/Ti diagrams show altered rock bulk compositions to be consistent with the development of muscovite, while background samples have an illite ± albite precursor. The precursor lithotype has a major influence on the intensity of alteration and resultant mineralogy of altered samples.

    IA shows that carbonate carbon, Ag, As, K, Pb, Rb, Sb, Tl and Zn are strongly added to host rocks, while Na is strongly leached. Other elements show variable trends towards ore, with lithotype strongly affecting the patterns. Samples have greater mass gains closer to ore. Selection of an appropriate parent rock is critical in gaining meaningful results in IA
    Original languageEnglish
    Pages (from-to)129-141
    Number of pages13
    JournalGeochemistry: Exploration, Environment, Analysis
    Volume4
    Issue number2
    DOIs
    Publication statusPublished - 2004

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    Ores
    Deposits
    radio
    Rocks
    Calcium Carbonate
    lithotype
    Bearings (structural)
    Sedimentary rocks
    rock
    Mineralogy
    Carbonates
    Aluminum
    ore body
    analysis
    albite
    calcium carbonate
    Potassium
    muscovite
    illite
    host rock

    Cite this

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    title = "Two lithogeochemical approaches to the identification of alteration patterns at the Elura Zn-Pb-Ag deposit, Cobar, New South Wales, Australia: Use of Pearce Element Radio analysis and Isocon analysis",
    abstract = "Lithogeochemical approaches to the identification of ore-related alteration can be obscured by closure effects and/or pre-existing lithological variations. Two mass balance approaches that can address these problems are Pearce Element Ratio analysis (PER) and Isocon analysis (IA). Both approaches have been applied to sedimentary rocks hosting the Elura ore-body, north of Cobar, in central-west New South Wales, Australia. Elura is an epigenetic, zinc–lead–silver deposit, (45 Mt with 8.5{\%} Zn, 5.3{\%} Pb, and 69 ppm Ag), hosted within Devonian siltstone–sandstone turbidites of the Cobar Basin. The ability of PER and IA to identify alteration at Elura and to navigate towards ore within altered zones is evaluated.PER identified mineralogical controls on calcium, carbonate, potassium and aluminium. Molar Ca/Ti v. C/Ti plots segregate calcite-bearing background samples from iron–magnesium–carbonate altered rocks closer to ore. Molar K/Ti v. Al/Ti and K/Ti v. (Al–Na)/Ti diagrams show altered rock bulk compositions to be consistent with the development of muscovite, while background samples have an illite ± albite precursor. The precursor lithotype has a major influence on the intensity of alteration and resultant mineralogy of altered samples.IA shows that carbonate carbon, Ag, As, K, Pb, Rb, Sb, Tl and Zn are strongly added to host rocks, while Na is strongly leached. Other elements show variable trends towards ore, with lithotype strongly affecting the patterns. Samples have greater mass gains closer to ore. Selection of an appropriate parent rock is critical in gaining meaningful results in IA",
    author = "Michael Whitbread and Cara Moore",
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    AU - Whitbread, Michael

    AU - Moore, Cara

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    N2 - Lithogeochemical approaches to the identification of ore-related alteration can be obscured by closure effects and/or pre-existing lithological variations. Two mass balance approaches that can address these problems are Pearce Element Ratio analysis (PER) and Isocon analysis (IA). Both approaches have been applied to sedimentary rocks hosting the Elura ore-body, north of Cobar, in central-west New South Wales, Australia. Elura is an epigenetic, zinc–lead–silver deposit, (45 Mt with 8.5% Zn, 5.3% Pb, and 69 ppm Ag), hosted within Devonian siltstone–sandstone turbidites of the Cobar Basin. The ability of PER and IA to identify alteration at Elura and to navigate towards ore within altered zones is evaluated.PER identified mineralogical controls on calcium, carbonate, potassium and aluminium. Molar Ca/Ti v. C/Ti plots segregate calcite-bearing background samples from iron–magnesium–carbonate altered rocks closer to ore. Molar K/Ti v. Al/Ti and K/Ti v. (Al–Na)/Ti diagrams show altered rock bulk compositions to be consistent with the development of muscovite, while background samples have an illite ± albite precursor. The precursor lithotype has a major influence on the intensity of alteration and resultant mineralogy of altered samples.IA shows that carbonate carbon, Ag, As, K, Pb, Rb, Sb, Tl and Zn are strongly added to host rocks, while Na is strongly leached. Other elements show variable trends towards ore, with lithotype strongly affecting the patterns. Samples have greater mass gains closer to ore. Selection of an appropriate parent rock is critical in gaining meaningful results in IA

    AB - Lithogeochemical approaches to the identification of ore-related alteration can be obscured by closure effects and/or pre-existing lithological variations. Two mass balance approaches that can address these problems are Pearce Element Ratio analysis (PER) and Isocon analysis (IA). Both approaches have been applied to sedimentary rocks hosting the Elura ore-body, north of Cobar, in central-west New South Wales, Australia. Elura is an epigenetic, zinc–lead–silver deposit, (45 Mt with 8.5% Zn, 5.3% Pb, and 69 ppm Ag), hosted within Devonian siltstone–sandstone turbidites of the Cobar Basin. The ability of PER and IA to identify alteration at Elura and to navigate towards ore within altered zones is evaluated.PER identified mineralogical controls on calcium, carbonate, potassium and aluminium. Molar Ca/Ti v. C/Ti plots segregate calcite-bearing background samples from iron–magnesium–carbonate altered rocks closer to ore. Molar K/Ti v. Al/Ti and K/Ti v. (Al–Na)/Ti diagrams show altered rock bulk compositions to be consistent with the development of muscovite, while background samples have an illite ± albite precursor. The precursor lithotype has a major influence on the intensity of alteration and resultant mineralogy of altered samples.IA shows that carbonate carbon, Ag, As, K, Pb, Rb, Sb, Tl and Zn are strongly added to host rocks, while Na is strongly leached. Other elements show variable trends towards ore, with lithotype strongly affecting the patterns. Samples have greater mass gains closer to ore. Selection of an appropriate parent rock is critical in gaining meaningful results in IA

    U2 - 10.1144/1467-7873/03-031

    DO - 10.1144/1467-7873/03-031

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