Pahtavaara Gold Mine

DESCRIPTION

Pahtavaara gold mine lies in the Finnish Lappland. About 25 km NW of Sodankylä.
At first some gold anomalies in till and an extensive scarn zone gave the explorers a lead to the ore. Visible gold in an outcrop was found by Geological Survey of Finland (GTK) in 1985.
GTK made in the following years a detailed exploration of the area. In 1991 the ownership switched to Terra Mining who continued the exploration.
An open pit mine was opened in 1996. Between 1996 and 1998 2131 kg gold was mined. The total contents of gold in the mine is about 10500 kg.
The mine was planned to be closed in 1999, if it was closed or not, I don't know.

GEOLOGY

The ore lies in the center of a 40x5 km area with komatiitic lavas and pyroclastic rocks, in the contact zone between a komatiitic pyroclastic and a komatiitic lava unit.
Regional metamorphism have transformed minerals into new ones. like carbonates and talc.
The gold is concentrated in a central ore, 5-10m wide, over 400m long, dipping to the north at an angle of 70-80°.
At least two stages of folding have affected the area.
The age of the gold mineralisation lies at about 1820 million years.
Most gold occur as free gold associated with silicate, carbonates and baryte. Some gold also occurs as inclusions in magnetite, pyrite and chalcopyrite. Visible gold is easiest found in coarse-grained amphibole rock with quartz-baryte veins.

VISITS

1999-06-30 We made a brief stop at the Pahtavaara gold mine during the 1999 Northern Scandinavia mineral tour. We were greated by the management of the mine and the local geologist. After a short introduction to the local geology and the history of the mine we were guided into the oldest open pit mine. It was closed and the water had started to fill it, but still a large part of the mine remained above the water level.
We stopped about half way down and was showed the ore zone on the rock wall. It consisted of baryte, talc, siderite and tremolite. I chopped of some baryte and passed it around the rest of the group. When Eli got it she looked at it and said crap, tossed it straight up ... of course it came down again ... on the head of Odd. What a luck that we all wore helmets!
After that we all spread out along the road at the side of the pit, examining the rocks. After a while I heard people shouting and turned around. Up from the bottom of the pit a reindeer was running for it's life, between the cars and the people. It seemed as we had trapped a reindeer and when people got deeper and deeper down in the pit we finally got it cornered and it decided to flee. What a sight, too bad I didn't have the camera handy.
We only found one small grain of gold, but some nice samples of baryte and some carbonate crystals were found.

I thank the Pahtavaara mine for a very nice reception and for letting us visit their mine.

LITTERATURE

To read more, see the page at GSF.

Mineral assemblage

Gold, Magnetite, Rutile, Scheelite, Pyrite, Chalcopyrite, Pentlandite, Pyrrhotite, Violarite, Millerite, Cubanite, Clausthalite, Merenskyite, Quartz, Baryte, Calcite, Siderite, Tremolite, Talc, Plagioclase, Actinolite, Biotite, Tourmaline,

Tremolite
Dark green tremolite with small patches of brown siderite.
Collected in 1999-06-30.
(Size 7x5x4 cm)

Siderite
Another view of the same rock as above. This side of the rock contains mostly siderite with some parts of tremolite visible.
Collected in 1999-06-30.
(Size 7x5x4 cm)

Talc
This small rock concists mostly of siderite with some talc sheets embedded in the matrix.
Collected in 1999-06-30.
(Size 3x3x2.5 cm)

Baryte
A massive piece of baryte from the main pit at Pahtavaara.
In the medium grained baryte lies a larger crystal of baryte. It doesn't show any crystal faces, but shows perfectly the cleavage of baryte.
Collected in 1999-06-30.
(Size 7x3x4 cm)

Baryte
A good example of the mineral mixture in the baryte veins. This small rock from the main pit contains pyrite, magnetite, talc, some carbonates, tremolite and possibly chalcopyrite.
Collected in 1999-06-30.
(Size 3x3x3 cm)

Magnesite ???
A nice rock with the top half of it covered with small rhombohedric crystals, 1-3 mm in size. Some clear, some with yellow to gray inclusions.
I'm not shure what carbonate this is. At least the brown middle part of the rock seems to concist of siderite. The bottom part is mainly a mixture of talc, actinolite and some carbonate. The matrix indicates that it could be siderite, magnesite or ankerite.
Collected in 1999-06-30.
(Size 11x6x4 cm)

If you have some questions, suggestions or comments you are welcome to write me a line or two.

Locality index. Finnish locality index. Main index.

axelsson@acc.umu.se

	Tremolite Dark green tremolite with small patches of brown siderite. Collected in 1999-06-30. (Size 7x5x4 cm)
	Siderite Another view of the same rock as above. This side of the rock contains mostly siderite with some parts of tremolite visible. Collected in 1999-06-30. (Size 7x5x4 cm)
	Talc This small rock concists mostly of siderite with some talc sheets embedded in the matrix. Collected in 1999-06-30. (Size 3x3x2.5 cm)
	Baryte A massive piece of baryte from the main pit at Pahtavaara. In the medium grained baryte lies a larger crystal of baryte. It doesn't show any crystal faces, but shows perfectly the cleavage of baryte. Collected in 1999-06-30. (Size 7x3x4 cm)
	Baryte A good example of the mineral mixture in the baryte veins. This small rock from the main pit contains pyrite, magnetite, talc, some carbonates, tremolite and possibly chalcopyrite. Collected in 1999-06-30. (Size 3x3x3 cm)
	Magnesite ??? A nice rock with the top half of it covered with small rhombohedric crystals, 1-3 mm in size. Some clear, some with yellow to gray inclusions. I'm not shure what carbonate this is. At least the brown middle part of the rock seems to concist of siderite. The bottom part is mainly a mixture of talc, actinolite and some carbonate. The matrix indicates that it could be siderite, magnesite or ankerite. Collected in 1999-06-30. (Size 11x6x4 cm)