Boudinage-type Structures at Sørfinnset, Gildeskaal, North Norway

• Published in: Geological Magazine
• Main Authors: Bradshaw, R., Wells, M. K.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Cambridge University Press (CUP) 1964
• Subjects: Geology; Norway; Sørfinnset; North Norway
• Online Access: http://dx.doi.org/10.1017/s0016756800050020; https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0016756800050020

Abstract A layer of massive and lineated hornblende-biotite-gneiss has fractured along ac -joints (perpendicular to the layering and b –lineation), at regular intervals along its lower surface in contact with a thin marble bed. The joints have been opened from below and the marble has penetrated upwards to form intrusive tongues caused by extremely plastic flow folding, as shown by the unbroken banding in the marble. The structure constitutes a variety of one-sided boudinage involving segmentation in the lowest metre or so of the hornblendic rock, while the extreme marble deformation is all accommodated in a few centimetres thickness. The structures must have developed at relatively high temperatures to allow contemporaneous segregation of quartz-feldspar pegmatite veins from the hornblendic rock, and of diopside reaction skarns at the marble junctions.