Bohus granite

Besides the main minerals plagioclase, K-feldspar and quartz the Bohus granites contain lesser amounts of magnetite, apatite, zircon, titanite, garnet and monazite.

In restricted areas alteration of the original rock has added prehnite, calcite and chlorite to the mineral assemblage.

In terms of geochemistry the rocks have a narrow range of high silica contents (68–75 wt% SiO2) and are mildly peraluminous.

The Bohus granites intruded and cooled in the brittle middle crust, later being rapidly exhumed so that by the time of the formation of the Sub-Cambrian peneplain in the Late Neoproterozoic the rocks were at surface.

[4] In the Mesozoic the rocks were subject to significant weathering resulting in the formation an irregular grand-scale relief called the Sub-Mesozoic hilly peneplain.

Polished surface of a Bohus granite.
Simplified geological map of Sweden. The Bohus granites are shown as a belt in the northern Swedish West Coast.