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Kylylahti |
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Finland |
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Cu Co Ni Zn Au
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Super Porphyry Cu and Au
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IOCG Deposits - 70 papers
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All papers now Open Access.
Available as Full Text for direct download or on request. |
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The Kylylahti copper-cobalt deposit is located in eastern Finland, 24 km north-west of Outokumpu, and some 400 km north-east of Helsinki.
It is one of a series of 'Outokumpu style' deposits located within 50 km Outokumpu and are characterised by their unusual Cu-Co-Zn-Ni-Au association, occurring as elongate or ribbon-like sulphide rich bodies up to several km in length, several tens of metres thick and several hundred metres in width located at the contact between a complex sequence of metasomatically-altered ultramafic rocks and black sulphidic psammites ('black shale').
Kylylahti is hosted within one of a series of complexly deformed linear belts, of 1 to 5 km long discontinuous lenses of serpentinite, each of which is enclosed by an envelope of 'black shale' within a monotonous sequence of wackes. At Kylylahti these rocks have been metamorphososed to lower amphibolite facies.
The host sequence is characterised by progressively more altered ultramafic rocks as sulphide mineralisation is approached. The sequence from hangingwall to footwall comprises serpentinite grading into talc-magnesite rocks, to tremolite-carbonate-quartz rocks to quartz-tremolite rocks to sulphide bearing quartz±tremolite rocks.
The Kylylahti deposit is located on the vertically dipping eastern limb of a shallowly plunging synform. Mineralisation occurs as 1-20 m thick layers of 40-70% semi-massive sulphide mineralisation directly in contact with 'black shale'. The deposit subcrops to the north, and extends down plunge for more than 1000 m as two separate mineralised zones, Wallaby and Wombat, to a depth of 700 m below surface.
The sulphides of theorebody are coarse-grained and comprise roughly equal, but locally highly variable, proportions of pyrite and pyrrhotite with lesser chalcopyrite and sphalerite, and lesser, but significant cobaltite and Co-pentlandite. Semi-massive sulphides grade upwards into, and are interlayered with, disseminated sulphides up to 30 m thick with 5 to 40% sulphide, increasing upwards. The sulphide content generally decreases laterally. Disseminated sulphides are dominant pyrrhotite with only minor pyrite.
The published measured + indicated + inferred resource in 2008 was (Vulcan Resources Ltd, 2008):
7.8 Mt @ 1.17% Cu, 0.24% Co, 0.22% Ni, 0.49% Zn, 0.70 g/t Au.
At the same date the probable + proven reserves were (Vulcan Resources Ltd, 2008):
6.9 Mt @ 1.17% Cu, 0.24% Co, 0.20% Ni, 0.49% Zn, 0.70 g/t Au.
The most recent source geological information used to prepare this decription was dated: 2006.
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.
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