Emplacement features of lamprophyre and carbonatitic lamprophyre dykes at Aillik Bay, Labrador

Abstract

AbstractAlkaline and ultramafic lamprophyre dykes at Aillik Bay on the coast of central Labrador exhibit features indicative of volatile-rich conditions at the time of emplacement. Aillikites (ultramafic lamprophyres) are flanked by closely spaced fracture systems whose formation was promoted by a carbonate-rich fluid moving ahead of the intruding magma. Sannaites (alkaline lamprophyres) frequently have horned termination structures which are interpreted to be partial reconnections between dyke segments which had separated at an earlier stage of intrusion.The lamprophyre dykes comprise three sets which are interpreted as cone sheets and radial dykes related to an intrusive centre located beneath the Labrador Sea to the northeast of the coastal exposures. This complex is one of several on the margins of the Labrador Sea, and its position may be influenced by the Archean/Aphebian boundary and by a major oceanic structural feature represented by offsets in seafloor magnetic anomalies.