Abstract

A 15-m-wide dike at Popes Harbour on the eastern shore of Nova Scotia shows an increase in both the size (up to 1 m) and density (up to ∼50%) of predominantly pelitic xenoliths toward the dike center. These features reflect flowage differentiation processes during dike emplacement. Flow direction is indicated by sillimanite xenocrysts that represent the unassimilated products of xenolith disaggregation. The xenocrysts are highly aligned parallel to the dike margins (northwest-southeast), with a mean plunge of 20°SE, suggesting that the magma last moved, and may have been injected, in a subhorizontal, northwestward direction. The available information indicates that lateral injection of magma in mafic dikes is more common than predominantly vertical movement. This study shows that an analysis of fabrics in mafic dikes should be useful in further evaluating the role of lateral magma injection in dike formation.

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