NGU-scientists present new article in Nature Communications
The paper “Deconvoluting complex structural histories archived in brittle fault zones” by G. Viola, T. Scheiber, O. Fredin, H. Zwingmann, A. Margreth and J. Knies (doi: 0.1038/NCOMMS13448) describes the results of an innovative conceptual and methodological approach to a better understanding of brittle fault zones. Detailed structural analysis is therein combined with K-Ar dating of illitic clays formed in situ during brittle faulting. This is innovative because, for the first time, it is possible to untangle the complex internal architecture of fault zones by constraining their individual structural domains with their age of formation.
The results are highly impacting because brittle faulting accommodates momentous and potentially dangerous deformation (the recent earthquakes in Italy and New Zealand reflect the slip of major brittle faults) and brittle structures are among the most common (yet most poorly understood) features of the Earth’s upper crust. They affect and steer with often dramatic consequences processes such as earthquake nucleation, water flow in rocks, slope and rock mass stability, mineral deposit distribution and oil reservoir occurrence and characteristics, just to mention a few.
Viola et al. report results from a reactivated fault in western Norway, the Goddo Fault (Fig. 1). The Goddo Fault nucleated during the Permian c. 260 Ma ago before being reactivated again in the Jurassic 200 Ma ago. 125 Ma ago, during the Early Cretaceous, the fault reacted again to circulating fluids connected with the evolution of the off-shore domain on the Mid-Norwegian margin. The approach illustrated by the paper 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.
One central thrust of the BASE project has been to establish a new laboratory for characterization of illite clay and dating using the K-Ar method at NGU. The laboratory is now operational and NGU expect significant scientific and applied advances to be made the coming years.
The BASE project (“Basement fracturing and weathering on- and offshore Norway – Genesis, age, and landscape development”) is a multidisciplinary research program run by a team of researchers based at the Geological Survey of Norway (NGU), some of which are also affiliated with other Norwegian institutions such as the NTNU, the University of Tromso – CAGE Center of Excellence and the Sogn and Fjordane University College. BASE draws significantly also on the collaboration with other Norwegian (SINTEF) and international partners (University of Bologna, Italy; CSIRO, Perth, Australia; Kyoto University, Japan).
BASE is a four-year initiative launched in 2014 that is funded by several oil companies (Lundin Oil, Det norske oljeselskap, Maersk Oil and Wintershall) and the NGU. Its main aim is to gain improved knowledge of the genesis, of the age and the processes of landscape development of fractured and weathered basement blocks on- and offshore Norway. The project’s research rationale is steered by the need of a better understanding of the Norwegian territory at large and oil exploration-driven goals. Recent large oil discoveries for example in the North Sea are located within basement blocks that exhibit geological features typical of highly fractured, faulted and weathered rocks and their understanding requires good control of the responsible geological processes.