In the western part of Rhum island, Scotland, Tertiary rocks consist of a core of spherulitic microgranite surrounded by a graphophyre (used to denote a specific type of acid rock, since granophyre has been used for the whole) and bounded on the north by Torridonian sandstone. Structural, petrologic, and chemical evidence indicates that the microgranite, graphophyre, and a zone of transitional rocks have been produced by metasomatic and metamorphic transformation of the Torridonian sandstone while in a solid state. The Torridonian rocks have been enriched in Al 2 O 3 , Na 2 O, FeO, and Fe 2 O 3 , and SiO 2 has been expelled.

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