Initial Caledonian Magmatism in Jamtland Area, Sweden: Chapter 28: Central Orogenic Belt
A late Precambrian sequence in the Caledonian geosyncline was penetrated by numerous steep dikes of olivine-bearing porphyritic diabase which acted as feeder conduits for volcanic members of the superimposed lower Ordovician sequence. Volcanism in this part of the geosyncline began with the extrusion of albite rhyolite, followed by basaltic and acidic volcanic rocks. The sequence of igneous activity ended with peridotite intrusions and a basaltic flow.