The
Skouries gold-copper project is located 35 km from the Stratoni port in on the
Chalkidiki Peninsular of northeastern Greece. The deposit is hosted by at least
four hypabyssal monzonite-porphyry phases that intruded the basement of the
Sebomacedonian Massif (SMM) along a deep-seated NW-SE –striking fault system at
19 Ma. The pipe-like intrusions that host the Skouries deposit extend at
surface over an area of approximately 200 m2 and have a vertical
extent of 700 m.
The
Skouries porphyry copper-gold mineralization is subvertical in orientation and mainly
veinlet-type in nature, comprising chalcopyrite, pyrite and bornite. Intense
postassic alteration characterize high-grade ore and can be subdivided into hydrothermal
orthoclase, typically veinlets, and hydrothermal biotite-magnetite,
predominantly pervasive disseminations, assemblages. Large propylitic and
phyllic alteration zones, common to many porphyry copper deposits, are not obvious
at Skouries. Only a moderate propylitic alteration halo overprints with
wall-rock gneisses around the intrusions. This, less that 50 m wide, contact
halo contains less than 1% disseminated pyrite and rare chalcocite. Gold mineralization
typically occurs as native gold associated with gangue minerals, and as blebs
within sulphides, particularly bornite and chalcocite.
Metal
mineralogy displays vertical zoning within the orebody. The first 30-50 m from
surface is described as an oxidized zone with an assemblage of
azurite-malachite. This overlies a supergene enriched zone of mainly
covellite. The main porphyry deposit, a
medium-grained, pinkish-grey monzonite, is intimately associated with
high-grade ore and stockwork mineralization. It occurs at two intervals, one
near surface and a second below 350 m depth.
As
of 2012 the mines life is estimated at 27 years, with total mineral reserves of
3.6 Moz of gold and 736,000 t of copper. The project employs a simple
metallurgical process method to produce clean Cu-Au concentrate via floation
and dore from the gravity circuit. The project remains in the development stage
and is expected to access the porphyry via an open pit operation to ~240 m
depth followed by underground drift and fill.
Source: Eldorado Gold Corp. website http://www.eldoradogold.com,
April 2013
T.
Kroll, D. Müller, T. Seifert, P.M. Herzig & A. Schneider, 2002. Petrology and geochemistry of the shoshonite-hosted Skouries porphyry Cu–Au deposit, Chalkidiki,
Greece. Mineralium Deposita, 37:1 pp 137-144
