Abstract

The sedimentary and volcanic formations of the Aillik series in the Makkovik Bay area of the Labrador coast are about 25 000 ft (~7620 m) in thickness. They have been folded into a series of northerly-trending folds and are intruded by gabbro, diorite, syenite, and abundant granite. Potassium–argon age determinations range from 1730 to 1830 million years for two gneisses, and from 1500 to 1600 million years for the metamorphosed sedimentary and volcanic rocks and intrusive granite-gneiss and granite. The structural features of the area indicate a single cycle of orogenic deformation for the sedimentary and volcanic rocks, in which the emplacement of synkinematic granite gneiss as domes and other bodies played an important role. One of the gneisses is considered a part of the migmatized Archean basement on which the Aillik series was laid down, and was subsequently involved in the Hudsonian orogenic cycle about 1600 million years ago. The area lies to the northwest of the Grenville Front, and has been intruded by diabase dikes corresponding in age to the Grenville orogeny, and by lamprophyre dikes of Cambrian age.

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