On the basis of their mineralogy and chemistry, the late Precambrian volcanic rocks of Avalon, southeast Newfoundland, are shown to be spilite and keratophyre. A metasomatism, operative at least on the scale of analyzed samples, accompanied this metamorphism. The effects of this metasomatism cannot be ignored in assessing analytical data for purposes of igneous petrogenesis. This and other difficulties arising from penological investigation of spilite/keratophyre terrain are discussed.

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