Petrology and geochemistry of granulite xenoliths from Central Hoggar (Algeria) — Implications for the lower crust

Granulitic xenoliths, enclosed in Neogene alkali basalts from the Atakor and Adrar N'Addjer volcanic massifs in Central Hoggar, southern Algeria, include mafic metaigneous and felsic metasedimentary rocks. The main mineral phases of metaigneous xenoliths are plagioclase and pyroxenes whereas quartz, feldspars, sillimanite, garnet and sapphirine occur in metasedimentary granulites. The metaigneous xenoliths represent a magmatic sequence of cumulitic and non-cumulitic rocks which resembles gabbroic bodies associated with anorthosites and has calc-alkaline affinities. Similar types and distributions of granulitic xenoliths are widespread and are probably characteristic of the lower crust in general, suggesting its homogeneity on a large scale but heterogencity on a local scale.