Formation of planar deformation features (PDFs) in zircon during coseismic faulting and an evaluation of potential effects on U–Pb systematics

Zircons from pseudotachylyte and cataclasite veins in the Svarthumlevatnet metagabbro, SW Norway, are faulted, brecciated and display multiple sets of planar deformation features (PDFs) that we assign to coseismic deformation in the middle crust during Caledonian continent collision. The zircons give a U–Pb upper intercept age of 1507 ± 4 Ma, interpreted as a minimum age of the gabbro, and a lower intercept age of 968 ± 31 Ma, likely indicating the time of granulite-facies metamorphism, but they do not record the Caledonian coseismic faulting even when the fault planes are healed by thin veins of low-U zircon. The work indicates that PDFs are not exclusive to meteorite impacts, but may also develop during seismic faulting.