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| Titel: |
Waterloo and Agincourt prospects, northern Queensland: Contrasting styles of mineralization within the same volcanogenic hydrothermal system |
| Auteur: |
Huston, D. L. Kuronen, U. Stolz, J. |
| Verschenen in: |
Australian journal of earth sciences |
| Paginering: | Jaargang 42 (1995) nr. 2 pagina's 203-221 |
| Jaar: |
1995-04 |
| Inhoud: |
The Waterloo and Agincourt prospects are two small volcanic-hosted massive sulphide deposits that occur close to the stratigraphic top of a large alteration zone within the Trooper Creek Formation of the Cambro-Ordovician Seventy Mile Range Group. Although only 1 km apart, the two deposits show differences in the style and mineralogy of mineralized zones in terms of metal contents, ratios and correlations, and sulphur isotope systematics. The Waterloo deposit is a small, high-grade zinc-copper-rich massive sulphide lens, whereas the Agincourt deposit consists of low- to moderate-grade disseminated zinc and lead through much of the alteration zone with only minor baritic sulphide lenses. These differences resulted from higher temperature fluids in the Waterloo deposit, and the swamping of the Agincourt hydrothermal system by felsic volcaniclastic flows. Major ore minerals present at both deposits include pyrite, sphalerite, galena, chalcopyrite and barite. Waterloo has significant quantities of tellurides and bornite, minerals not observed at Agincourt. The Waterloo deposit is characterized by high copper ratios (100Cu/[Cu+Zn+Pb]) and high zinc ratios (lOOZn/ [Zn+Pb]). Agincourt has low copper ratios and more typical zinc ratios. At Waterloo gold correlates with copper, whereas at Agincourt gold correlates with zinc. Alteration of footwall andesitic units at Waterloo is characterized by two principal mineralogical assemblages: (i) weak carbonate-pyrite-sericite; and (ii) a strong sericite-quartz-pyrite+carbonate alteration. Major and trace element data for relatively unaltered and variably altered andesitic volcanic units indicate that Al, Ti, P, Zr, Nb and the rare earth elements remained essentially immobile during hydrothermal alteration, whereas the most intense sericite-quartz-pyrite alteration resulted in strong relative enrichment in K, Rb and Bi, and mared relative depletion in Ca, Na, Sr, Mn and Cu. δ34S values of sulphide minerals from Waterloo and Agincourt are lower than other Cambro-Ordovician volcanic-hosted massive sulphide deposits, and the values increase from the footwall alteration zone, into the massive sulphide/barite lenses. These characteristics are most likely caused by sulphide deposition from oxidized hydrothermal fluids. |
| Uitgever: |
Taylor & Francis |
| Bronbestand: |
Elektronische Wetenschappelijke Tijdschriften |
Details van artikel 13 van 13 gevonden artikelen
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