ABSTRACT
The Lewis Hills is the southernmost of the four Bay of Islands Ophiolite
Complex massifs. These massifs are considered to be the dissected remnants
of a once nearly continuous thrust slice of oceanic crust and upper mantle
of Early Ordovician age. The Lewis Hills Massif may be divided into three
north south trending zones. The eastern zone (Bay of Islands Complex) is
composed of variably deformed and recrystallized gabbro, troctolite, wehrlite
and dunite cumulates and harzburgite tectonites. The western zone (Little
Port Assemblage) consists of greenschist facies metagabbros, diabase dikes
and minor quartz-diorite bodies. The central zone (Mount Barren Assemblage)
is a 3 kilometer wide zone of highly deformed metagabbros and amphibolites
cut by syn- and post- kinematic mafic and ultramafic intrusive bodies.
The central zone grades into the western zone but has a sharp igneous contact
against the eastern zone, it is proposed that the central zone rocks represent
the deep crustal levels of an oceanic fracture zone preserved between two
less deformed assemblages of oceanic crust and upper mantle. Along strike
to the northeast, rocks similar to those of the eastern and western zones
of the Lewis Hills are exposed in the Bay of Islands Ophiolite Complex
and the Coastal Complex respectively. The Mount Barren Assemblage has not
been previously described as part of the Coastal Complex and provides an
important link between the Bay of Islands and Coastal Complexes. Detailed
studies in the Lewis Hills permit fairly well constrained models to be
constructed for the kinematics and timing of processes during the evolution
of oceanic fracture zones and the obduction of the Bay of Islands Complex.
Karson, J.A., 1977. Geology of the northern Lewis Hills, western Newfoundland.
Unpublished PhD dissertation, State University of New York at Albany.
474pp., +xxii; 5 folded plates (maps)
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