title: Deconvoluting complex structural histories archived in brittle fault zones.
abstract: Brittle deformation can saturate the Earth's crust with faults and fractures in an apparently chaotic fashion. The details of brittle deformational histories and implications on, for example, seismotectonics and landscape, can thus be difficult to untangle. Fortunately, brittle faults archive subtle details of the stress and physical/chemical conditions at the time of initial strain localization and eventual subsequent slip(s). Hence, reading those archives offers the possibility to deconvolute protracted brittle deformation. Here we report K-Ar isotopic dating of synkinematic/authigenic illite coupled with structural analysis to illustrate an innovative approach to the high-resolution deconvolution of brittle faulting and fluid-driven alteration of a reactivated fault in western Norway. Permian extension preceded coaxial reactivation in the Jurassic and Early Cretaceous fluid-related alteration with pervasive clay authigenesis. This approach represents important progress towards time-constrained structural models, where illite characterization and K-Ar analysis are a fundamental tool to date faulting and alteration in crystalline rocks.
authors.affiliation: Geological Survey of Norway, Trondheim 7491, Norway.|Department of Geology and Mineral Resources, Norwegian University of Science and Technology, Trondheim 7491, Norway.
authors.forename: G
authors.initials: G
authors.lastname: Viola
authors.affiliation: Geological Survey of Norway, Trondheim 7491, Norway.
authors.forename: T
authors.initials: T
authors.lastname: Scheiber
authors.affiliation: Geological Survey of Norway, Trondheim 7491, Norway.|Department of Geography, Norwegian University of Science and Technology, Trondheim 7491, Norway.
authors.forename: O
authors.initials: O
authors.lastname: Fredin
authors.affiliation: Department of Geology and Mineralogy, Kyoto University, Kitashirakawa Oiwake-cho, Kyoto 606-8502, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Zwingmann
authors.affiliation: Geological Survey of Norway, Trondheim 7491, Norway.
authors.forename: A
authors.initials: A
authors.lastname: Margreth
authors.affiliation: Geological Survey of Norway, Trondheim 7491, Norway.|CAGE-Centre for Arctic Gas Hydrate, Environment and Climate, Department of Geology, The Arctic University of Norway, Tromsø 9037, Norway.
authors.forename: J
authors.initials: J
authors.lastname: Knies