Geology and mineralisation of the Greenmount Cu-Au-Co deposit, southeastern Marimo Basin, Queensland
Titel:
Geology and mineralisation of the Greenmount Cu-Au-Co deposit, southeastern Marimo Basin, Queensland
Auteur:
Krcmarov, R. L. Stewart, J. I.
Verschenen in:
Australian journal of earth sciences
Paginering:
Jaargang 45 (1998) nr. 3 pagina's 463-482
Jaar:
1998-06
Inhoud:
The Greenmount deposit is hosted by mid-Proterozoic graphitic and carbonaceous slates of the Marimo Slate within tens of metres of the contact with the calcareous and evaporitic metasediments of the Staveley Formation in the southern Marimo Basin, some 40 km south of Cloncurry, A diorite intrudes the sequence and is altered and veined but not mineralised. The area around Greenmount is particularly disjointed and structurally complex. Late brittle faults fragmented the rocks and earlier tight D2 folds. Alteration and mineralisation was localised in or near to a 'flat' ramp (subparallel to the formational boundary) within a reverse fault/shear regime, and veining and mineralisation was in a dominantly brittle to brittle-ductile regime. The Marimo Slate, the Staveley Formation and the diorite underwent regional- and deposit-scale alkali-rich metasomatism dominated by micro-cline with subordinate albite, sericite (retrogressed microcline) and lesser hematite, rutile, tourma-line, quartz, dolomite ± sulfides ± magnetite. The underlying Staveley sequence contains 'red-rock' (hematite-microcline) alteration and intraformational breccias. The Marimo Slate often hosts 'white-rock' (microcline-quartz-pyrite) alteration. These extensive alteration zones are overprinted by episodic vein assemblages at Greenmount. Episodic veining comprises a stockwork of millimetre- to metre-wide veins, which in the Marimo Slate is dominated by microcline with lesser quartz, albite, phlogopite, apatite, ferroan dolomite and sulfides, and in the Staveley Formation is dominated by microcline, dolomite, calcite with lesser albite, muscovite, pyrite, biotite, magnetite and chalcopy-rite. Vein density generally decreases in the Staveley Formation away from the contact with the Marimo Slate. Mineralisation occurred syn- to post-veining. The most important economic metals are Au, Cu and Co. Sulfide mineralogies are dominated by pyrite and chalcopyrite with lesser cobaltite and minor marcasite.
Tijdschrift beschrijving