Petrographic analysis of fault rock structures from Notre Dame Bay, Newfoundland, Canada

Abstract

This study investigates fault rocks in the Leading Tickles area of Notre Dame Bay Magmatic Province (NDBMP), Newfoundland, Canada. The NDBMP consists of alkaline mafic intrusions, and the Leading Tickles region is characterized by radial lamprophyre dykes, Leading Tickles Stock and Budgell’s Harbour Stock, which fold and fault the surrounding Ordovician host rocks. This region is within an eastern peri-Gondwanan exploits subzone which was affected by the Appalachian orogenic events including the Taconic, Salinic and Acadian orogenies. The primary objectives of this study were to examine fault rock deformation processes, investigate interactions between the fault rocks and lamprophyre dyke fragments, and examine fault rock kinematics and reactivation. This thesis presents a petrographic analysis of two fault rock samples collected from Cull Island, near the town of Leading Tickles in NDBMP. The first sample is identified as a non-foliated Protocataclasite, displaying features of both brittle and ductile deformation, consistent with formation in the brittle to ductile transition zone and late-stage fluid infiltration. The second sample is classified as a non-foliated mosaic fault breccia, indicative of brittle deformation at shallower crustal levels in a fault zone with late-stage carbonate infiltration. The absence of lamprophyre dyke fragments within the samples suggests faulting processes predate the dyke intrusion. In addition, the observed fault rocks are likely related to the Luke’s Arm Fault Zone (LAFZ), which crosses the study area, and may reflect broader fault reactivation along Newfoundland’s margin during the Mesozoic.