Mindanao, Philippines

Main commodities: Cu Au
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Tampakan comprises a highly telescoped copper-gold deposit pair of high sulphidation-epithermal ores overprinting older, erosionally exhumed, deeper-level porphyry-Cu mineralisation, located ~65 km north of General Santos City within southern Mindanao, the Philippines (#Location: 6° 28' 30"N, 125° 3' 0"E).

The deposit is hosted by sub-aerial andesites of Miocene to Pliocene age on the western flank of a deeply dissected andesitic stratovolcano belonging to the north-western Sangihe Arc.   It lies within the centre of a 100 km wide sinistral strike-slip deformation zone represented by the NW-trending trans-Mindanao Cotabato Fault zone.   NNE oriented dilational faults within the Pliocene stress field associated with the Cotabato Fault zone exert a stong control on the epithermal mineralisation at Tampakan.

The Tampakan district is centred on a deeply eroded polygenetic volcanic complex which was active episodically from the Late Miocene to late Quaternary. The volcanics and intrusives are dominated by mafic to silicic andesite flows and intrusives of Late Miocene to Middle Pliocene age, with lesser basaltic andesite flows of Late Miocene age and dacitic flow domes and plugs of Pleistocene age. The Tampakan porphyry mineralisation is hosted by Late Miocene and early Pliocene volcanics, whereas the Tampakan high-sulphidation deposit also lies within younger, middle Pliocene volcanic and intrusive rocks.

The principal host rocks to the high sulphidation mineralisation are the Tampakan Andesite Sequence of Late Miocene to Mid-Pliocene age. They comprise porphyritic hornblende-pyroxene andesite and silicic andesite flows that dip at 10 to 20° towards the WSW, sub-parallel to the mineralised lithocap in the deposit. Hornblende-diorite porphyry stocks intrude the Tampakan Andesite Sequence in the deposit area, varying from holocrystalline and equigranular to crowded-porphyry-textured intrusives with 70 to 80% phenocrysts. The intrusives form apophysis-like dykes and stocks, and tend to be altered but weakly mineralised.

The high sulphidation mineralisation and associated acid alteration form a manto-like zone extending along an erosion surface that exhumed the low grade porphyry Cu system which predated the epithermal phase by ~1 M.y. There is a strong structural and stratigraphic control to the high sulphidation mineralisation, which occurs as a flat lying to gently dipping 200 to 500 m thick body that covers a surface area of some1.6 x 2 km, and lies within a district wide advanced-argillic and argillic lithocap exceeding 90 sq. km. in area.   The Pula Bato Fault Zone, which comprises a NNE-trending series of faults that transect the Pliocene volcanic edifice, lies along the long-dimension of the Tampakan orebody. High-sulphidation mineralisation pinches downward along this fault zone, and mushrooms upward into a broad, manto-like, stratabound zone of advanced-argillic alteration that encapsulates the central zones of high-sulphidation ore. The ore is in turn encompassed by a gently dipping, tabular zone of partial to massive silicification accompanied by multiphase brecciation and acid leaching (producing vuggy porosity). The high sulphidation mineralisation is dominated by vein and vug-filling enargite-bornite-digenite-chalcocite-covellite±molybdenite, and is associated with an assemblage of silica-pyrophyllite-dickite-alunite-diaspore±sericite. This alteration grades downwards to sericite-chlorite and relict potassic biotite-chlorite-magnetite-anhydrite alteration and associated weakly mineralised, but pervasively developed quartz stockwork veining that is interpreted to represent the outer shell of a porphyry system.

Porphyry Cu-Au mineralisation is widespread below the high sulphidation ores. It is encountered at depths of 400 to 500 m where drilling has passed into low grade chalcopyrite-bornite-pyrite in pervasive quartz stockwork veining, hosted by andesitic flows and the roof zone of high level hornblende-diorite stocks. The principal sulphide and oxide minerals in equilibrium with porphyry-stage anhydrite-biotite alteration are chalcopyrite, bornite, pyrite, magnetite (up to 8%), subordinate specular hematite and molybdenite. This mineralisation is dominated by pink-grey coloured, multi-directional, crudely laminated veins with medial crack-seal textures that contain traces of bornite and/or chalcopyrite and/or pyrite. Anhydrite-bearing veins are less prevalent. Chalcopyrite is the dominant sulphide occurring as disseminated grains, as anhedral inclusions within and along the margins of hydrothermal magnetite grains, and as elongate laths that extend along cleavage planes of hydrothermal biotite grains. Bornite is subordinate to chalcopyrite, and both are always in textural equilibrium, often forming composite sulphide grains. Molybdenite and hematite are minor phases in the potassic alteration zone. Porphyry-stage sulphides also occur as fracture-controlled disseminations within the wallrock to quartz-dominated and lesser anhydrite-bearing veins.

The deposit in 2005 (Indophil Resources website) was estimated to contain 12 Mt of copper and 500 tonnes (16 Moz) of gold, but is open both to the west and at depth.
    At a cut-off of 0.2% Cu the mineral resource has been calaculated at 2.5 Gt @ 0.48% Cu
    At a cut-off of 0.5% Cu the mineral resource is estimated to be 900 Mt @ 0.75% Cu

In 2010, the measured + indicated + inferred resource estimate, using a 0.3% copper cut-off (Sagittarius Mines, Inc. website) totalled:
    2.4 Gt @ 0.6% Cu, 0.2 g/t Au, 70 ppm Mo, comprising 13.5 Mt of Cu and 490 t of contained Au.

The most recent source geological information used to prepare this summary was dated: 1999.    
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd.   Unauthorised copying, reproduction, storage or dissemination prohibited.

  References & Additional Information
   Selected References:
Middleton C, Buenavista A, Rohrlach B, Gonzalez J, Subang L and Moreno G  2004 - A geological review of the Tampakan copper-gold deposit, southern Mindanao, Philippines: in   Hi Tech and World Competitive Mineral Success Stories Around the Pacific Rim,  Proc. Pacrim 2004 Conference, Adelaide, 19-22 September, 2004, AusIMM, Melbourne,     pp 273-187
Rohrlach B D and Loucks R R   2005 - Multi-Million-Year Cyclic Ramp-up of Volatiles in a Lower Crustal Magma Reservoir Trapped Below the Tampakan Copper-Gold Deposit by Mio-Pliocene Crustal Compression in the Southern Philippines: in Porter, T.M. (Ed), 2005 Super Porphyry Copper & Gold Deposits - A Global Perspective, PGC Publishing, Adelaide,   v.2 pp. 369-407
Rohrlach B, Madera A, Watt R  1999 - Geology, alteration and mineralisation of the Tampakan copper deposit: in    Proc. Pacrim 99, Conference, Bali, Indonesia, AusIMM, Melbourne    pp 517-525

   References in PGC Publishing Books: Want any of our books ? Pricelist
Rohrlach B D and Loucks R R, 2005 - Multi-Million-Year Cyclic Ramp-up of Volatiles in a Lower Crustal Magma Reservoir Trapped Below the Tampakan Copper-Gold Deposit by Mio-Pliocene Crustal Compression in the Southern Philippines,   in  Porter T M, (Ed),  Super Porphyry Copper and Gold Deposits: A Global Perspective,  v2  pp 369-407
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Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge.   It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published.   While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo takes no responsibility what-so-ever for inaccurate or out of date data, information or interpretations.

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