"Petrographic and chemical study of biotite gneiss and charnockite and the gradational transition zone between them suggests three probable modes of origin: (i) that charnockite was regionally widespread and the biotite gneiss was derived from it by retrograde metamorphism; (ii) that the charnockite represents a conformable intrusive igneous rock which with biotite gneiss was subjected to high-grade metamorphism; (iii) that the charnockite was derived from the biotite gneiss, by the introduction of some ferrous-iron rich juvenile solution. The latter is preferred."

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