Paul D. Gray

B. Sc. Honours Thesis

Deformation and metamorphism in the contact aureole of the S. Mt. Batholith, Bedford area

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This study documents structures related to Halifax Pluton emplacement, in the Bedford area. Intrusion of the Devonian South Mountain Batholith caused both metamorphism and deformation of the Cambrian-Ordovician Meguma Group. Most previous structural interpretations for the area have attributed local structural features to regional deformation events. Field and petrographic analysis indicates that a strain and thermal aureole exists in a zone surrounding the Halifax Pluton. Mapping revealed several structures hitherto locally unrecognized, including a schistose lineated fabric (LS2) and other minor contact-parallel features. Microscopic analysis of these rocks defined an aureole at least 1.5 km wide, divided into an outer biotite zone, a medial cordierite zone, and an inner K-feldspar zone. A cross-section along the axial trace of the Bedford Syncline indicates a variation in style of deformation and strain with proximity to the granite contact. An increase in dip of bedding towards the contact is interpreted as a result of flattening perpendicular to the granite boundary, probably with a high ratio of pure shear to simple shear. The same cross-section also offered insight on the depth to detachment of both the transverse anticline and the larger Magazine Hill Basin. Metamorphic minerals define the deformation structures (e.g. LS2), which suggests deformation and metamorphism were both imposed by the rising, and possibly ballooning granite pluton. Therefore this study proposes that metamorphism and significant deformation of the Goldenville Formation in the study area are related spatially and temporally to the emplacement of the Halifax Pluton.

Keywords: Halifax Pluton, Goldenville Formation, Contact Metamorphism, Deformation, Emplacement, Aureole, Foliation
Pages: 77
Supervisors: Nicholas Culshaw / Rebecca A. Jamieson