Deformation path partitioning within a transpressive shear zone, Marble Cove, Newfoundland

Detailed study of the structures in Marble Cove, Newfoundland, indicates that they formed during a single transpressional event, during which deformation was partitioned between dominantly strike-slip and dominantly dip-slip domains. Marble Cove exhibits steeply dipping foliations, steeply to shallowly plunging stretching lineations, greenschist facies mineral assemblages, and abundant quartz veins. Within the broad domain where stretching lineations plunge steeply, sense-of-shear indicators and asymmetry of quartz-c-axis distributions in mylonitized quartz veins indicate dominantly reverse motion with a component of dextral shear. Adjacent greenschists exhibit orthorhombic symmetry and apparently accommodated pure shear. The abrupt transition to a narrow, high strain domain of shallowly plunging stretching lineations is accommodated by a rheologically distinct serpentinite body. Shear bands in this domain indicate dextral strike-slip movement with a reverse component. Smaller, conjugate shear bands are evident in thin section, indicating a component of pure shear. Sense-of-shear indicators and asymmetry of c-axis distributions in mylonitized quartz veins also record dextral strike-slip and reverse shear with a component of pure shear. Crenulations and asymmetric folds in foliation overprint all other fabrics in Marble Cove and record a final phase of reverse shear with a dextral component. artitioning of this kind, structures recording strike-slip movement may be limited in areal extent, and therefore less likely to be exposed, than structures recording dip-slip motion. Such partitioning within transpressional shear zones may therefore impede recognition of strike-parallel motions within orogenic belts.