Metamorphic peak geothermobarometry in the Furulund Group, Sulitjelma, Scandinavian Caledonides: implications for uplift

• Published in: Journal of Metamorphic Geology
• Main Authors: BOYLE, A. P., WESTHEAD, R. K.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1992
• Subjects: Arctic; Furulund; Sulitjelma; Tilting
• Online Access: http://dx.doi.org/10.1111/j.1525-1314.1992.tb00110.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1525-1314.1992.tb00110.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1525-1314.1992.tb00110.x

ABSTRACT Regional metamorphism in the Sulitjelma area of the arctic Scandinavian Caledonides has produced a series of Barrovian zones, from chlorite through to kyanite in more aluminous pelites, which transect the major lithological boundaries in a large nappe unit of the Köli Nappe Complex. The metamorphic zones are inverted, and metamorphic grade increases westwards from the foreland to the hinterland. The Furulund Group comprises a mixed sequence of originally flysch‐like sediments which crop out over the whole range of the observed Barrovian zones, but are usually too calcareous to develop the characteristic Barrovian aluminous phases staurolite and kyanite. Instead, above the garnet isograd, the Furulund Group pelites and semi‐pelites have widely developed hornblende porphyroblasts in the common assemblage Grt + Pl + Bt + Ms + Qtz ± Hbl ± Ep ± Czo ± Chl ± Cal ± Dol. Thermobarometric estimates of metamorphic peak P–T conditions (i.e. at maximum recorded temperatures) from this assemblage, using three different methods, indicate a westward increase of both pressure and temperature over a distance of 14 km away from the garnet isograd towards the hinterland of the orogen, independent of topographic level and without change in the common mineral assemblage. The increased peak pressure in the west indicates greater initial burial and subsequent exhumation in the hinterland than towards the foreland. Restoration indicates that the Furulund Group has been subjected to substantial eastward bulk tilting after peak metamorphic conditions. Whilst this enhances the overturning of the metamorphic zones, the amount of tilting was not sufficient to cause the overturning.