The structural history of the Leipikvattnet Nappe in the Joma area of Nord Trøndelag, central Scandinavian Caledonides, Norway

The Leipikvattnet Nappe in the Joma area is composed of the stratigraphic sequence, greenstone,
quartzitic phyllite, graphitic phyllite, tectonically repeated by thrusting and locally overturned in the area of the Joma sulphide deposit. The greenstones (Røyrvik Group) are composed of massive and pillowed lava flows overlain by volcaniclastic deposits and are thought to represent the remnants of a basaltic sea mount or oceanic island. In the Joma area, Dl and D2 deformations are associated with movements on the major and internal thrust planes, whereas D3 and D4 postdate them. This sequence is correlated with deformation histories from the rest of the central Scandinavian Caledonides, using the major NESW trending folds to which the F3 Joma Synform belongs. D3 deformation is suggested, from lineation distributions and finite strain results, to have resulted from late movement of the Børgefjell massif. Subhorizontally oriented F4 folds are suggested to have formed in response to overburden pressure when horizontal stress was reduced over the crest of the rising massif.