The Billefjorden Fault Zone (BFZ) is a N-S striking regional-scale long-lived lineament cropping out in central Spitsbergen. This lineament exposes multi-deformational evolution that initiated with ductile deformation preserved in the metamorphic basement. Following several phases of brittle deformation affected also younger sedimentary successions. This project aims to address key knowledge gaps about structural style and timing of the transition from ductile to brittle deformation of the BFZ. I will investigate two areas in the western and eastern parts of Billefjorden, where metamorphic basement is exposed. The field-based dataset will allow to reconstruct the structural evolution of this fault zone which is the main objective of my Master thesis.