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]