Kiruna porphyry

Igneous rocks found in northernmost Sweden

Kiruna porphyry (Swedish: Kirunaporfyr) is a group of igneous rocks found near Kiruna in northernmost Sweden.[1] The Kiruna Porphyry formed 1,880 to 1,900 million years ago[1][2] during the Paleoproterozoic Era in connection to the Svecofennian orogeny.[2]

The iron-apatite ore mined in Kiruna, Malmberget and Svappavaara are all hosted in Kiruna porphyry.[2] While generally well-preserved for its age at some locations such as Malmberget the Kiruna porphyry is more metamorphosed.[1]

In detail, various rock types are distinguished in the Kiruna porphyry such as trachyandesite lava and quartz-bearing porphyry of rhyolitic composition.[1] These two rocks are traditionally known as "syenite porphyry" and "quartz porphyry" respectively (Swedish: syenitporfyr , kvartsporfyr).[2][1] The former is found on the foot wall of the Kiruna iron ore body, while the latter is found in the hanging wall.[1] Part of the quartz-bearing porphyry is thought to be ignimbrite.[1] The Haparanda Series of rocks found to east near the Sweden-Finland border are thought to have the same origin as the Kiruna porphyry.[3]

## See also

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* Kurravaara conglomerate

## References

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1. ^ a b c d e f g Lundqvist, Thomas (2009). Porfyr i Sverige: En geologisk översikt (in Swedish). pp. 24–25. ISBN 978-91-7158-960-6.
2. ^ a b c d "kirunaporfyrer". Nationalencyklopedin (in Swedish). Retrieved 12 December 2019.
3. ^ Brewer, T.S.; Pharao, T.C. (1990). "Early Precambrian basic rocks of the Baltic Shield". In Hall, R.P.; Hughes, D.J. (eds.). Early Precambrian Basic Magmatism. Blackie. p. 291.