Petrologic and geothermobarometric investigations in the Kasai gabbro-noritic complex and associated metadolerite dykes (Zaire).

In the south of Kasai, Archaean rocks metamorphosed (2800 m.y. ago) in granulite facies conditions include a large basic plutonic gabbro-norite complex with subordinate anorthosite and acidic charnockitic-enderbitic gneisses (M.A. 13-677, 14-154) and granulite-facies metasediments cut by dolerite dykes. In the gabbro-norite complex, the orthopyroxene-clinopyroxene and clinopyroxene-garnet mineral pairs gave an average T of 730 + or - 50oC and the plagioclase- clinopyroxene-orthopyroxene-garnet- quartz assemblages gave a P of 7.0 + or - 0.5 kbar. The development of garnet is controlled by the whole-rock Fe/Mg ratio, the An content of the plagioclase and the amount of normative quartz.-R.A.H.SCOPUS: ar.j