Strain localization associated with channelized melt migration in upper mantle lithosphere: Insights from the Twin Sisters ultramafic complex, Washington, USA

► Deformation in upper mantle peridotites was associated with dunite band formation. ► Dunite bands represent former melt channels, which facilitated strain localization. ► Strain partitioned within melt channels, without net displacement across band margins. ► Localization and material flow within channels also induced proximal host rock strain.