Gold deposits in northern Finland - Arkisto.gsf.fi

Lansi
Karolina
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Mobydick
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Whaleback
Figure 12. Resource blocks
beyond the past and present
mining, as of October
2012, in the Pahtavaara
gold mine. View to the NW.
Image courtesy Lappland
Goldminers AB.
ite, cubanite, gold, clausthalite and merenskyite
have been detected in the ore (Hulkki 1990,
Korkiakoski 1992, Kojonen & Johanson 1988).
As the gold occurs as free grains, the ore can
be concentrated using a gravity and a flotation
circuit, as described on Lappland Goldminers’
web site (www.lapplandgoldminers.se): “The ore
is first crushed and then ground down into a
1.5 mm grain size. This finely-ground material
goes through a cyclone, where heavier material
continues on to a cone separator. Afterwards the
material continues through a magnetic separator
and spiral separators before coming out onto the
concentrating table. The lighter material continues
after the cyclone to a flotation circuit.
The final product is three different concentrates:
gravitation concentrate, middling concentrate
and flotation concentrate. Concentration has a
capacity of 1 500 tons of raw ore/day.”
Saattopora gold mine
Tero Niiranen, Geological Survey of Finland
The Saattopora Au(-Cu) deposit is located in
the western part of the Central Lapland Greenstone
Belt next to the crustal-scale Sirkka thrust
zone (Fig. 3). The deposit was discovered in
1985 by Outokumpu Oyj and was subsequently
mined 1988–1995 from two open pits and
underground workings. The total amount of
gold produced was 6 279 kg, and 5 177 tonnes
of copper was recovered as a by-product from
2.163 million tonnes of ore. Mill feed grades
were 3.29 g/t Au and 0.28% Cu (Lahtinen et al.
2005, unpublished report, Outokumpu Mining
Oy). Saattopora is one of several gold deposits
discovered along the east–west trending
Sirkka Thrust Zone. However, it is the only deposit
which has been under full-scale mining.
The deposit consist of two, roughly east–west
trending lodes which are hosted by variably altered
mica schist, phyllite, komatiite, mafic tuff
and mafic lava of the >2.2 Ga Savukoski Group
sequence (Fig. 13). The intrusions in the area
consist of 2.2–2.0 Ga dolerite and c. 2.0 Ga
felsic porphyry dykes. The former occurs in the
ore-hosting sequence.
The deposit consists of north-striking, subvertical
to vertical, auriferous quartz-carbonate-sulphide
veins, vein arrays and hydrothermal
breccias (Fig. 14). Gold occurs as free and
native gold in association with the sulphides,
quartz and carbonates. Pyrite and pyrrhotite
are the main opaque phases, and chalcopyrite,
gers dorffite, rutile, pentlandite, tucholite,
urani nite, bismuthite and niccolite com­
28 Pasi Eilu & Tero Niiranen (ed.)