Geology, geochemistry, mineralisation, and metal zoning of the McConnochie greisenised granite, Reefton district, Westland, New Zealand

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Abstract
A high-level, small gramtic body, informally named McConnochie greisenised granite, was emplaced within Greenland Group rocks, probably above the roof region of a subjacent pluton, in the Reefton-Victoria Range area of Westland, New Zealand. The McConnochie greisenised granite is a highly evolved member of a granite series forming the western margin of the Karamea Batholith in the area of study and shows an apparent overall S-type chemistry. It was originally a granodiorite which was subjected to varying degrees of postmagmatic alteration (greisenisation) during the Cretaceous. The greisenisation affected both the original granodiorite body (endogreisen) and the surrounding country rock (exogreisen). Mineralisation occurs in both endogreisen and exogreisen rocks and consists of pyrite, marcasite, chalcopyrite, molybdenite, minor sphalerite, and native bismuth. Sn mineralisation probably occurred near the top of the greisenised granite cupola, but was later removed by erosion. This is shown by a vertical geochemical zonation in which Sn values decrease with depth in the drill core, whereas Cu and Mo are enriched in the lower and more greisenised parts of the granite body. It is possible that muscovitisation of biotite is, at least in part, responsible for the release of the ore metals during greisenisation and associated hydrothermal activity.