Location:

Porphyry-style wolframite-molybdenite-arsenopyrite-sphalerite. Mount Pleasant, New Brunswick, Canad

Two quartz-feldspar porphyritic stocks have intruded Carboniferous acid volcanics and both the mineralization and wallrock alteration are zoned about them. Potassic alteration of the porphyry stocks has produced numerous orthoclase, quartz, fluorite and molybdenite veinlets and passes out into a zone of phyllic-style alteration comprising quartz, muscovite and chlorite with minor topaz and fluorite. Within this zone, silicification accompanied by topaz and fluorite is intense and passes outwards to a chlorite zone with lesser amounts of silica and fluorite. Early tungsten, molybdenum and bismuth minerals with arsenopyrite and minor cassiterite occur along joint planes or are disseminated within the stock a5 an inner zone. Cassiterite, arsenopyrite, sphalerite and chalcopyrite are disseminated within breccia pipes and dykes as a middle zone, and sphalerite, arsenopyrite, cassiterite, chalcopyrite, galena, and bismuthinite occur as a replacement deposit at the margins of the stocks.

Major Minerals:

Arsenopyrite, sphalerite, wolframite (ferberite), molybdenite, native bismuth, cassiterite, lollingite chalcopyrite, galena

Minor Minerals:

Scheelite, rutile, bismuthinite, stannite, kesterite, stannoidite, pyrite, tennantite, marcasite

Trace Minerals:

Include wittichenite, galenobismutite, aikinite, cosalite, covelline, blaubleibender covelline, bornite, pyrrhotite, pyrargyrite

Textures:

Rutile is prismatic or acicular. Tabular wolframite is associated with scheelite. Euhedral, simply twinned cassiterite is replaced by chalcopyrite and sphalerite. Molybdenite encloses the oxide minerals. Arsenopyrite/lollingite carry native bismuth inclusions and are fractured. A number of sphalerite generations are present and enclose pyrrhotite and stannite group minerals. Chalcopyrite disease in sphalerite is widespread. Chalcopyrite carries stannite inclusions as does galena. Pyrrhotite is altered to, and pseudomorphed by, pyrite and marcasite to give bird's-eye and lath-shaped textures

References:

Dagger, 1972; Petruk, 1973; Parrish, 1977; Davis and Williams-Jones, 1985; Kooiman et al., 1986