Larvikite

Larvikite occurs in the Larvik Batholith (also called the Larvik Plutonic Complex), a suite of ten igneous plutons emplaced in the Oslo Rift (Oslo Graben) surrounded by ~1.1 billion year old Sveconorwegian gneisses. The Larvik Batholith is of Permian age, about 292–298 million years old. Larvikite is also found in the Killala Lake Alkalic Rock Complex near Thunder Bay in Ontario, Canada.

The name originates from the town of Larvik in Norway, where this type of igneous rock is found. Many quarries exploit larvikite in the vicinity of Larvik.

Formation

Intrusions of larvikite in Norway form part of the suite of igneous rocks that were emplaced during the Permian period, associated with the formation of the Oslo Rift. The crystallisation of a ternary feldspar indicates that this rock began to crystallise under lower crustal conditions.