Serpentinization and carbonatization of tectonic melanges in the Coy Pond Complex, Central Newfoundland

• Main Author: Timbal, Nicolai Adrian
• Format: Thesis
• Language: English
• Published: Memorial University of Newfoundland 1992
• Subjects: Newfoundland
• Online Access: https://research.library.mun.ca/6748/; https://research.library.mun.ca/6748/1/NicolaiAdrianTimbal.pdf; https://research.library.mun.ca/6748/3/NicolaiAdrianTimbal.pdf

Mount Cormack Terrane, an elliptical tectonic window in the Dunnage Zone of central Newfoundland, is a structural dome comprising a central zone of variably metamorphosed metasediments surrounded by remnants of several ophiolitic complexes including the Coy Pond Complex, the subject of this study. The ophiolite complexes have been interpreted to represent remnants of the early Paleozoic Iapetus ocean floor, which was obducted onto the continental margin of Gondwana. -- The Coy Pond Complex, is an imbricated, but complete ophiolite which is oriented subvertically and dips and youngs outward from the tectonic window. -- Analyses of relict olivines, pyroxenes and spinels in the Coy Pond Complex indicate that it has an arc-related petrogenesis. -- The Coy Pond Complex is composed of two structural slices separated by two tectonic mélanges. From west to east the principal structural elements are: (i) basil structural slice composed of harzburgite and dunite; (ii) western tectonic mélange; (iii) central structural slice comprising pyroxenite, gabbro-diabase, pillow lava and sedimentary rocks; (iv) the eastern tectonic mélange. -- Locally the basal structural slice is missing and its place is taken by the mixed lithology slice, which is composed of exotic (i.e. non-ophiolitic) lithologies that were probably derived from the tectonically overlying and underlying units. -- The tectonic mélanges, are composed of ultramafic fragments up to 2 m in longest diameter enveloped in an ultramafic matrix. They display evidence of brittle (fragments) and ductile (matrix) deformation and are interpreted to have formed during fault movement and emplacement of the ophiolite. On the basis of the lithologies of the fragments, the tectonic mélanges are interpreted to have formed from the transition zone (dunite) and upper part of the mantle tectonite (harzburgite). -- Both fragments and matrix in the tectonic mélanges are extensively serpentinized and variably carbonatized. Petrographic evidence indicates that serpentinization initially ...