IOCG and Porphyry-Cu deposits in Northern Finland ... - IAGS 2011

Hannukainen deposit
The Hannukainen deposit is the largest known deposit
in the Kolari area with current resource estimate
about 200 Mt (Table 1). The deposit consists
of five gently west dipping lenticular semi-massive
magnetite lenses hosted by Ca-clinopyroxene and
actinolite skarns (Fig. 3). The magnetite lenses and
the skarns overprint variably albitized Haparanda
Suite diorite and Savukoski Group tholeiitic volcanic
rock (Figs. 2-3). The deposit is structurally controlled
by one of the thrust zones of the Pajala-Kolari
shear zone system.
The Cu-Au mineralization is dominantly
hosted by the magnetite-rich lenses, and partially
by the skarns. Although Cu and Au occur in anomalous
concentrations throughout the deposit, only part
of the deposit is Cu-Au mineralized. The richest
Cu-Au grades are within the Laurinoja ore body in
which the best reported intercepts are ca. 0.8% Cu
and 0.3 g/t Au along 35 meter of core (Northland
data). However, as all the reported resource estimates
are based on iron cut off, the exact size and
grade of the Cu-Au-richest part is unknown.
The ore minerals at Hannukainen are magnetite,
pyrite, pyrrhotite and chalcopyrite bornite,
tellurides, gold, molybdenite, and uraninite (Hiltunen,
1982; Niiranen et al., 2007). Native gold occurs
in silicate gangue and inclusions in sulfides and
magnetite (Hiltunen, 1982;
Fig. 3. Surface
geology and a
cross section of
the Hannukainen
ore field. The deep
Kivivuopio ore
body is omitted
from the surface
geology. After
Hiltunen (1982),
redrawn by P.
Kurki.
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