Abstract

Lamprophyre dikes occur as northeast-striking swarms and in radiating patterns around alkaline stocks. They range in age from Jurassic to Cretaceous and are interpreted as the result of the rifting associated with formation of the North Atlantic Ocean. They show strong evidence of coexisting immiscible silicate liquids, with leucocratic globules in a darker host matrix. The globules are richer in CO2 and Na2O than the host and these liquids are not similar in composition to those of other immiscible liquid pairs. The whole suite is interpreted to have resulted from high pressure eclogite fractionation followed by volatile build-up due to lower pressure fractionation of olivine, titanaugite, plagioclase, biotite, and/or kaersutite.

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