Talvivaara - Kuusilampi, Kolmisoppi
Ni Co Cu Zn
The Talvivaara low-grade heap leach Ni, Zn, Cu, Co deposits of Kuusilampi and Kolmisoppi are located ~35 km south-west of the town of Sotkamo in eastern Finland and ~350 km south of the Arctic Circle (#Location: 63° 58' 21"N, 28° 5' 7"E).
Ni-Cu-Zn-rich black shales were found in glacial erratics and subsequently in outcrop during initial exploration during the 1930s and 1940s. The Geological Survey of Finland (GTK) discovered the deposit in 1977 and continued to investigate the resource until 1983. Outokumpu Plc. was granted mining licenses to the deposits in 1986 and continued testing in the late 1980's and early 1990's. The resource was found to be large but of relatively low grade, and it was concluded, at the time, that the deposit was uneconomic, and the rights were sold to Talvivaara Mining Company Plc in February 2004. After further research, construction of an on-site pilot heap was started in June 2005 and initial bioheapleaching commenced in August of the same year. Between April 2007 and October 2008, first metals were successfully produced at the Sotkamo mine. 13.3 Mt of ore was mined in 2010, and 11.1 Mt in 2011 (Talvivaara Mining Company, 2012).
The two deposits lie within the southern part of the Palaeoproterozoic Kainuu schist belt, in a 15 km long, 1 to 2 km wide unit characterised by black shales within a larger (100 km long) turbidite formation, and together define a >8 km long mineralised zone (Loukola-Ruskeeniemi and Heino, 1996). The host sequence in this mineralised zone consists mainly of quartzites, mica schists and black schists unconformably overlying an Archaean basement gneiss complex. The deposit is metamorphosed up to lower amphibolite facies and has been deformed.
The Ni-Cu-Co-Zn mineralisation is almost entirely (90%) hosted within high grade metamorphosed and intensively folded black schist, with the remaining 10% of the resource found within meta-carbonate rocks, mica schists, quartzites, greywackes and quartzwackes. Zn, Cu and Ni concentrations within the deposits are geochemically closely sympathetic, and as a whole, the host unit is enriched in Ag, As, Co, Cu, Hg, Mn, Ni, S, Se and Zn, and depleted in Na and the Light Rare Earth Elements, when compared to both adjacent unmineralised shales and global shale averages (Loukola-Ruskeeniemi, 1999; Vine and Tourtelot, 1970). Median δ34S sulphur isotope values are 25.2% for pyrrhotite and 24.3% for pyrite in Ni-rich units, and 23% for both in low Ni units. In addition, all shales within the deposits have positive Eu anomalies and are extensively pyritised (Loukola-Ruskeeniemi and Heino, 1996).
The black schists (characterised by >1% graphite and >1% S) are principally composed of an assemblage of quartz, micas, graphite and sulphides, with accessory rutile, apatite, zircon, feldspar and garnet (Loukola-Ruskeeniemi and Heino, 1996). They have been divided into three groups (Loukola-Ruskeeniemi and Heino, 1996) based on their absolute Ni and Mn content: i). Low Ni-Mn (< 0.1% Ni, <0.8% Mn); ii). Ni-rich (> 0.1% Ni), which are found mainly in a single horizon that can be followed for ~10 km along strike with a width which varies from a few metres up to 1 km; iii). Mn-rich (> 0.8% Mn), that occur in narrow, irregular horizons parallel to the Ni-rich black schists.
The sulphide content within the black schist ores is typically between 15 and 25%. Pentlandite contains between 75 and 88% of the contained nickel with much of the remainder in pyrrhotite. Pyrite holds the main share (between 67 and 90%) of contained cobalt while chalcopyrite carries copper and sphalerite is the principal zinc mineral. The black schist hosted ore also contains uranium in concentrations ranging from 0.0001% to 0.004% U, occurring as thucholite (a mixture of hydrocarbons, uraninite and sulphides). Curite type lead uranium hydroxide has also been encountered (Talvivaara Mining Company, 2012).
The average metal contents of the ore are 0.23% Ni, 0.13% Cu, 0.02% Co and 0.50% Zn. Three mineralogical ore types are recognised (Lamberg and Sotka, 2004):
i). Fine-grained disseminations, which is the dominant ore type, consisting of fine-grained pyrrhotite-pyrite disseminated in banded graphite mica schist - black schist. Pentlandite is generally encountered in fine-grained zones where it occurs in association with pyrrhotite. The pentlandite has three main modes of occurrence: a). discrete grains (<20 µm in diameter) on the boundaries of pyrrhotite grains, b). inclusions (<10 µm) in pyrrhotite, and b). exsolution inclusions (5x10 µm) in pyrrhotite.
ii). Sulphide breccia, which contains coarse-grained secondary pyrite-pyrrhotite breccia material and disseminated sulphides. This ore also contains fine-grained primary disseminated sulphide. The coarser grained breccia accounts for 7 to 20% of the total volume of the rock. The pyrrhotite / pyrite ratio in the coarse-grained veins varies significantly. Pentlandite is generally associated with pyrrhotite as discrete grains (10 to 70 µm in diameter) and grain chains on the boundaries of pyrrhotite crystals, or as exsolution inclusions (5 x 10 µm) in pyrrhotite; and
iii). Metacarbonate rock ore, composed of coarse-grained amphibole (tremolite) and calcite, with sulphide breccia material. In addition to tremolite and calcite, the principal mineral assemblage also includes phlogopite and graphite. Pentlandite occurs as fine-grained particles on the boundaries of pyrrhotite grains or as fine exsolution inclusions in pyrrhotite.
The Talvivaara deposit comprises two separate orebodies about 3 km apart, Kuusilampi and Kolmisoppi. Both are close to surface, with less than 2 m of overburden and extractable with a waste/ore ratio of close to 1:1 (Eilu and Västi, 2009). Kuusilampi is around 2600 m long, 40 to 1000 m wide and persists to a depth of 600 m, while Kolmisoppi is ~1500 x 30 to 350 m at surface, having being traced to a depth of 300. The metal distribution in the deposits is homogeneous.
Published resource figures at a 0.07% Ni cutoff are (Pitkäjärvi, of Talvivaara Exploration Ltd, 2010):
Measured Resource - 301.6 Mt @ 0.23% Ni, 0.02% Co, 0.13% Cu, 0.51% Zn,
Indicated Resource - 203.5 Mt @ 0.22% Ni, 0.02% Co, 0.12% Cu, 0.49% Zn,
Inferred Resource - 321.2 Mt @ 0.21% Ni, 0.02% Co, 0.12% Cu, 0.50% Zn,
Measured Resource - 61.9 Mt @ 0.24% Ni, 0.02% Co, 0.14% Cu, 0.52% Zn,
Indicated Resource - 74.6 Mt @ 0.22% Ni, 0.02% Co, 0.13% Cu, 0.49% Zn,
Inferred Resource - 41.3 Mt @ 0.20% Ni, 0.02% Co, 0.12% Cu, 0.47% Zn,
Measured + Indicated Resource - 642 Mt @ 0.20% Ni, 0.02% Co, 0.12% Cu, 0.49% Zn,
Inferred Resource - 362 Mt @ 0.20% Ni, 0.02% Co, 0.13% Cu, 0.49% Zn,
Measured + Indicated + Inferred Resource - 1.004 Gt @ 0.22% Ni, 0.02% Co, 0.13% Cu, 0.50% Zn.
Published JORC compliant resource figures (Talvivaara Plc website, 2013) at a 0.07% Ni cutoff, at the end of 2012 were:
Measured + Indicated Resource - 1305.5 Mt @ 0.22% Ni, 0.02% Co, 0.13% Cu, 0.50% Zn, 0.0017% U,
Inferred Resource - 748.3 Mt @ 0.21% Ni, 0.02% Co, 0.12% Cu, 0.49% Zn, 0.0018% U,
Measured + Indicated + Inferred Resource - 2.0528 Gt @ 0.22% Ni, 0.02% Co, 0.13% Cu, 0.50% Zn, 0.0017% U.
The most recent source geological information used to prepare this summary was dated: 2010.
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 to this deposit in the PGC Literature Service Collection:||
Jowitt S M and Keays R R, 2011 - Shale-hosted Ni‐(Cu‐PGE) mineralisation: a global overview: in Trans. IMM (incorp. AusIMM Proc.), Section B, Appl. Earth Sc. v.120 pp. 187-197|
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