Metamorphism and Metasomatism of Rocks of the Moine Series by a Dolerite Plug in Glenmore, Ardnamurchan

B. C. M. Butler
Dept. of Geology and Mineralogy, University Museum, Oxford.

Summary: A small dolerite plug in Glenmore, Ardnamurchan, has metamorphosed and partially vitrified the adjacent Moine arkoses up to a distance of 6 ft. from the contact. Chemical analyses show that the glasses produced by the metamorphism have compositions close to the ternary minimum in the system NaAlSi3O8-KAlSi3O8-SiO2, indicating that they were formed by fractional fusion of a lowest-melting composition from the arkose. Alkali metasomatism in the metamorphosed arkoses resulted in an increase of Na2O and a decrease of K2O as the contact with the dolerite is approached, while an associated pelitic horizon shows an increase of K2O content. A review of other examples of thermal metamorphism of quartzo-feldspathic rocks by basic intrusions shows that movements of alkalis are very common in this type of environment, and the possible relations of the metasomatism and the fusion are discussed.

Mineralogical Magazine; September 1961 v. 32; no. 254; p. 866-897; DOI: 10.1180/minmag.1961.032.254.03
© 1961, The Mineralogical Society
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