Data repository for: Evolution of brittle structures in plagioclase-rich rocks at high-grade metamorphic conditions – Linking laboratory results to field observations

Published: 11-03-2020| Version 1 | DOI: 10.17632/st6m4ccz4m.1
Sarah Incel,
Joerg Renner,
Bjørn Jamtveit


Pseudotachylytes as well as ductile shear zones can be found in high-grade metamorphic rocks in the Lofoten archipelago, N Norway, both reflecting the localization of strain. Compared to the pseudotachylyte mineral assemblage, ductile shear zones show a much larger extent of hydration, expressed by the formation of hydrous minerals. We combined experimental results and field observations to investigate the evolution of brittle structures in plagioclase-rich rocks at eclogite-facies conditions. We conducted deformation experiments on intact granulite samples and compared our laboratory results to natural microstructures of the Lofoten samples. To investigate the microstructural evolution of the experimental samples, we terminated the tests at ~7-8 % and 33-36 % axial shortening. We studied the importance of water for the microstructural evolution of the samples by either deforming natural samples ‘as-is’ or by adding approx. 1 wt.% H2O. In addition, we tested the influence of temperature by performing the experiments at 700 °C and 900 °C. All tests were conducted at a confining pressure of 2.5 GPa and a strain rate of 5×10^-5 s^-1. Similarities between the experimental and natural microstructures suggest that the transformation of brittle structures to ductile shear zones is most effective in samples deformed with added water.