Monteregian dike rocks.

The Monteregian petrographic province of southern Quebec consists of eleven alkalic intrusive stocks, and associated dikes and sills. The latter consist of lamprophyres (camptonite, fourchite, alnoite), leucocratic dikes (bostonite, tinguaite, ijolite) and mesocratic dikes of intermediate composition. The lamprophyres are distributed in three zones bounded by faults: an eastern camptonite zone, a central fourchite zone, and a western alnoite zone. The westward transition represents chemically a progressive decrease in Si02, Al203, Ti02 and total Fe, and a progressive increase in MgO, CaO, K20/Na20 and volatiles content of the respective lamprophyres, and is interpreted as generation of separate magma batches at increasingly greater depths within the upper mantle westward. [...