Inverted isograds at Sulitjelma, Norway: the result of shear‐zone deformation

• Published in: Journal of Metamorphic Geology
• Main Author: MASON, ROGER
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1984
• Subjects: Sulitjelma
• Online Access: http://dx.doi.org/10.1111/j.1525-1314.1984.tb00288.x; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.1111%2Fj.1525-1314.1984.tb00288.x; https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1525-1314.1984.tb00288.x

Abstract At Sulitjelma, Norway, there is a major inversion of metamorphic isograds beneath an inverted but undisrupted ophiolite. The flysch‐like Furulund schist in which the inverted isograds occur is also inverted and the early folds in it are downward facing. The isograds cut across the axial surfaces of early folds and across the schistosity. These relationships are explained as the consequence of metamorphism during the progressive development of a large overfold. The inverted limb of the overfold is regarded as a major, thick, gently‐dipping shear zone, separating the lower‐grade, lower part of the Caledonian allochthon below from the higher‐grade upper part of the allochthon above. The association between stratigraphical inversion, downward‐facing of syn‐schistosity folds and metamorphic inversion is explained by the progressive development of the shear zone. It is suggested that the presence of such shear zones is a common feature of orogenic belts formed by continental collision.