Northern continuation of Caledonian high-pressure metamorphic rocks in central-western Spitsbergen

Caledonian low-temperature, high-pressure metamorphic rocks, as first recognised at Motalafjella, central western Spitsbergen, include characteristic brown dolostone and serpentinite. Similar rocks are scattered in the strandflats, along the eastern marginal fault of the Tertiary Forlandsundet Graben, and along thrust faults to the east on both sides of St. Jonsfjorden. The mineral chemistries of the constituent carbonates and oxides are diagnostic of high-pressure metamorphic rocks, containing high contents of MgO in the carbonates and Cr₂O₃ in the oxides. Based on a surface magnetic-anomaly survey and fault-plane observations, some of these rocks are considered to have been pressed up along faults produced by strike-slip faulting during an early stage of the Forlandsundet Graben formation. The distribution of these rocks indicates that the high-pressure metamorphic rocks extend as much as 50 km to the NNW from Motalafjella to Sarsøyra.