Abstract:The 'S' type Barrytown biotite granite pluton which intrades Lower Ordovician greywacke and shales is exposed noar jts original roof level. The pluton is intemally zoned from a biotite-rich margin to an acid core. Mild pervasive hydrothermal alteration which affects much of the pluton comprises 3distinct varietiest; early propylitic alteratiori (chlorite-sericite +clinozoisite, sphene) was concentrated above the NW-SE trending, residially warm pluton core, while later intermediate argillic alteration (kaolinite, illite-tourmaline) developed in the vicinity of roof contacts due to trapping and condensation of acid volatiles. Quartz-tourmaline veins and associated greisen selvedges (quartz-muscovite-rutile in granite, quartz-musccvite-tourmaline in metasediments) are restricted to, and apparently postdate, the central clinozoisite-sphene part of the propylitic zone, and contain minor scheelite and rare wolframite, cassiterite, molybdenite and chalcopyrite. Abundant secondary Ti-phases may have held magmatic Sn, W in situ during alteration of biotite, preventing effective leaching and potential ore concentration.
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A. J. Tullocb.1986.[J].矿床地质,5(3):27~36.1986.Hydrothermal Alteration And Scheelite Mineralisation Associated With The Barrytown Pluton,North Westland, New Zealand[J].Mineral Deposits5(3):27~36
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