A suite of highly aluminous and titaniferous clinopyroxenes has been developed by amphibolite facies metamorphism of agpaitic alkalic rocks of the Red Wine alkaline complex in central Labrador, Canada. The pyroxenes are classified as aegirine, calcic aegirine, titanian aegirine, aegirine-jadeite, and titaniferous ferro-omphacite. The titanian pyroxenes have brilliant blue pleochroism. The omphacites are further distinguished from any previously known omphacites both by a high TiO2 content (up to 8 wt. per cent) and Mg × 100/Fe2+ + Fe3+) as high as 30. They have P2/n symmetry rather than the P2 symmetry generally ascribed to omphacite. Aegirine jadeites reach 70 mole per cent jadeite.The Red Wine complex consists of several small bodies of agpaitic alkalic rocks less than 4 km in diameter, and an area of oversaturated peralkaline granitic gneisses, all within the Grenville Front tectonic zone. The agpaitic alkalic rocks are strongly gneissic but enclose small bodies, often only a few hundred metres across, of nepheline syenite and malignite in which a relict igneous texture has survived metamorphic recrystallization.The principal rock types are green melanocratic gneisses, blue melanocratic gneisses, leucocratic to mesocratic gneisses, nepheline-arfvedsonite rocks, nepheline syenite and malignite. The major minerals are nepheline, albite, arfvedsonite and clinopyroxenes. Eudialyte-rich zones occur in most of the rock types, together with the usual suite of minor minerals associated with agpaitic rocks (e.g., ramsayite, lamprophyllite, joaquinite, aenigmatite, murmanite, etc.).Despite the presence of omphacites and jadeite-rich pyroxenes, the grade of regional metamorphism appears to be amphibolite facies. It is suggested that the metamorphism of the Red Wine alkaline complex was characterized by an initially steep P-T path that became shallower as temperature rose and pressure remained constant or declined. Aluminous and titaniferous pyroxenes are developed as a consequence of the low aSi and high peralkalinity of the rocks. Jadeitic pyroxenes are probably not uncommon in regionally metamorphosed nepheline-bearing rocks but generally have not been recognized during standard petrographic examination. Several examples of jadeitic pyroxenes from other localities are cited in support of this view. In nepheline-bearing rocks, jadeitic and omphacitic pyroxenes do not indicate the high pressures normally attributed to silica-saturated or oversaturated rocks that contain these minerals. © 1979 Oxford University Press.
