Polykinematic evolution of the Teakettle and Carmanville Melanges in the exploits subzone, Northeast Newfoundland

Lee, Christopher Bernard (1994) Polykinematic evolution of the Teakettle and Carmanville Melanges in the exploits subzone, Northeast Newfoundland. Masters thesis, Memorial University of Newfoundland.

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Abstract

The Carmanville Melange contains an impressive variety of sedimentary, igneous and metamorphic blocks in a silty shale matrix. Block lithologies include: pillowed basalts, gabbro, trondhjemite, greywacke, grey siltstone, rhythmically bedded grey siltstone and black shale, and polyphase deformed metamorphic rock. The polydeformed and metamorphosed rocks consist of variably strained pillow basalts, banded mafic metavolcanic rocks, and psammite, in a black pelitic matrix. This assemblage is interpreted as an earlier generation of melange (Teakettle melange), that now occurs as discrete blocks in the Carmanville Melange. -- The Carmanville Melange is associated with distinctive coticule-bearing shales and siltstones of the Woody Island formation and fragmental volcanic rocks of the Noggin Cove Formation. All of these units are assigned to the Hamilton Sound complex, and distinguished from the adjacent Davidsville Group. -- Structural and metamorphic contrasts between the Teakettle and Carmanville melanges are spectacular. Teakettle psammites locally exhibit overprinting of three phases of deformation, at least two with associated fabric development. The strong asymmetry of most of the structures, coupled with large scale boudinage, suggests a tectonic origin for the Teakettle melange or extreme deformation of an existing melange, at mid to deep crustal levels. -- The Carmanville Melange formed at higher crustal levels. It has early, asymmetrical layer-parallel shearing, produced by independent particulate flow, and asymmetrical, isoclinal folding in entrained stratified blocks. Later structures record increasing viscosity during deformation, progressing from folds and shear bands, to shearing on discrete surfaces and finally brecciation and cataclasis. Structures in the Carmanville Melange are interpreted as products of diapiric processes whereby a mobile matrix sampled and entrained of a wide variety of lithologies, with dramatic structural and metamorphic contrasts. The Carmanville Melange is therefore a non-stratigraphic unit, that has injected the Noggin Cove and Woody Island formations, and post-dates both. Diapiric mobility could have been driven by thrust imbrication, with attendant overthickening and overpressuring of wet sediments, at the base of an accretionary wedge.

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