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TitleCopper isotopic zonation in the Northparkes porphyry Cu-Au deposit, SE Australia
AuthorLi, W; Jackson, S E; Pearson, N J; Graham, S
SourceGeochimica et Cosmochimica Acta vol. 74, no. 14, 2010 p. 4078-4096,
Alt SeriesNatural Resources Canada, Contribution Series 20182805
PublisherElsevier BV
Mediapaper; on-line; digital
File formatpdf (Adobe® Reader®)
AreaNew South Wales; Parkes; Victoria; Australia
Lat/Long WENS 147.9667 148.0833 -32.9000 -32.9667
Subjectseconomic geology; geochemistry; Science and Technology; mineral exploration; mineral deposits; porphyry deposits; porphyry copper; gold; ore mineral genesis; mineralization; alteration; isotopic studies; copper geochemistry; sulphides; sulphur geochemistry; iron geochemistry; thermal analyses; bedrock geology; lithology; igneous rocks; porphyries; volcanic rocks; intrusive rocks; monzonites; mass spectrometer analysis; hydrothermal systems; magmatism; fluid dynamics; zoning; ore grades; Northparkes Deposit; Wombin Volcanics; trachyandesites; Phanerozoic; Paleozoic; Devonian; Silurian; Ordovician
Illustrationsbar graphs; location maps; geoscientific sketch maps; plots; profiles
Released2010 04 08
AbstractSignificant, systematic Cu isotopic variations have been found in the Northparkes porphyry Cu-Au deposit, NSW, Australia, which is an orthomagmatic porphyry Cu deposit. Copper isotope ratios have been measured in sulfide minerals (chalcopyrite and bornite) by both solution and laser ablation multi-collector inductively coupled plasma-mass spectrometry (MC-ICP-MS). The results from both methods show a variation in delta-65Cu of hypogene sulfide minerals of greater than 1 permille (relative to NIST976). Significantly, the results from four drill holes through two separate ore bodies show strikingly similar patterns of Cu isotope variation. The patterns are characterized by a sharp down-hole decrease from up to 0.8 permille (0.29±0.56 permille, 1 sigma, n=20) in the low-grade peripheral alteration zones (phyllic-propylitic alteration zone) to a low of ~-0.4 permille (-0.25±0.36 permille, 1 sigma, n=30) at the margins of the most mineralized zones (Cu grade >1wt%). In the high-grade cores of the systems, the compositions are more consistent at around 0.2 permille (0.19±0.14 permille, 1 sigma, n=40). The Cu isotopic zonation may be explained by isotope fractionation of Cu between vapor, solution and sulfides at high temperature, during boiling and sulfide precipitation processes. Sulfur isotopes also show an isotopically light shell at the margins of the high-grade ore zones, but these are displaced from the low delta-65Cu shells, such that there is no correlation between the Cu and S isotope signatures. Fe isotope data do not show any discernable variation along the drill core. This work demonstrates that Cu isotopes show a large response to high-temperature porphyry mineralizing processes, and that they may act as a vector to buried mineralization.