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Study of the mode of occurrence, petrography, and chemical and mineralogic composition of pegmatitic phases in dolerite (diabase) sills of the northeast United States, Scotland, and South Africa leads to the conclusion that dolerite pegmatites represent a post-injection product of normal differentiation. Two types are distinguished --the normal type is concordant and characterized by moderate iron enrichment; the other occurs in cross-cutting veins and is characterized by extreme enrichment in iron and titania.
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F. Walker (1953) studied this question.
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