Abstract

The reinvestigation of the rocks of the Shiant isles, off the west coast of Scotland, which began with a study of the olivines, now continues with the clinopyroxenes. Optical and chemical data are given for six specimens from the picrite, picrodolerite, and crinanite of the Garbh Eilean sill, one from a pegmatite patch in the picrite, one from a vein, and one from a pyroxene-rich layer in the Eilean Mhuire sill. Another specimen from the Portrush olivine dolerite sill (Antrim, Ireland) was analyzed for comparison. The trend of crystallization, relation of the composition to the parent rocks, and paragenesis with olivine are discussed, and comparisons are made with the Skaergaard intrusion in Greenland.

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