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Epithermal Gold 2012
Epithermal Gold Deposits of the Western Pacific
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[Field Traverses]
Field Traverses at Mankayan:   Interspersed between the lectures/presentations, the group was taken into the field to study the stratigraphy and lithologies (upper left image), including the diatreme breccia that cuts the concealed Far South-east porphyry deposit at depth, and contains clasts of porphyry mineralisation at surface, originally prompting the search for that deposit.   The group was also taken to study the 'Spanish Workings' (upper right image) where fresh exposures of the Lepanto high sulphidation ore may be inspected. The Lepanto ore is developed over an extensive area, basically along the intersection of an overlying aquitard unconformity and a pre-mineralisation fault that is cut by the Far South-east porphyry mineralisation below.   Escaping fluids from the Far South-east porphyry appear to have seeped up the fault and followed an upward gradient below the unconformity to form an extensive (>3 km long and up to 1 km wide), thick (100 to 200 m) advanced argillic lithocap, characterised by quartz-alunite and dickite-kaolinite, that hosts the enargite-luzonite-gold orebody (lower left image).   As such, this orebody is an upper, shallow, broadly coeval, peripheral zone of the large, concealed Far South-east porphyry copper-gold system.   Later in the day, the group studied vein material from the low to intermediate sulphidation Victoria and Teresa vein systems that appear to cut both the Far South-east and Lepanto ores.   Subsequent to visiting the 'Spanish Workings', the group was taken to a vantage point and the structure and distribution of the main units were pointed out with the aid of detailed geological maps (lower right image).   The field traverses were led by Peter Dunkley.   Photographs by Mike Porter.

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