The Arvidsjaur granite is a diapir-like intrusion, 25 kilometres in diameter, situated 100 kilometres to the south of the Arctic circle in Swedish Lapland. It is a post-kinematic intrusion emplaced during the Svecokarelian orogeny and has yielded an Rb-Sr isochron age of about 1750 Ma.

Previously the granite was poorly known and this study represents the first detailed investigation of the region.

Geophysical data indicate that it has a discoid shape with an actual thickness of 3-5 kilometres, perhaps representing the basal part of a diapiric intrusion, the upper part (perhaps 5-10km) having been removed by erosion.

Petrographic study shows a very homogeneous perthite leucogranite with riebeckite. Microprobe analyses do not permit any subdivision of the batholith.

Major element chemistry is characterised by a high Si02 content (76#2%) and a high differentiation index (0.93 and above).

Analysis of trace elements reveals that the Arvidsjaur batholith ranges from normal alkali granite to highly differentiated granite.

It is suggested from geochemical relationships that the surrounding volcanics, the Arvidsjaur porphyries, are, at least partly, the extrusive equivalent of the initial magma of the Arvidsjaur granite. It can also be shown that, with respect to major and trace elements, there are strong similarities between the Revsund granites (diapir-like intrusions contemporary to the Arvidsjaur granite), the Avaviken granite and the Arvidsjaur granite.

An attempt is made to evaluate all the data and present a model for the magmatic evolution.

The magmatic history of the Arvidsjaur granite began in the mantle whilst a subduction zone was active further to the SW. Remelting of the basic lower continental crust occurred during the first stages of differentiation. As a result the Arvidsjaur granite inheritated mixed characters between I(gneous) and S(edimentary) types.