Petrology of the Scourie Dyke, Sutherland

M. J. O'Hara
Grant Institute of Geology, Edinburgh.

Summary: Chemical data are given for four rocks from the Scourie dyke, Sutherland, and for the constituent minerals. Three of the specimens are unsheared and represent stages in a continuous variation from a one-pyroxene (subcalcic ferroaugite) dolerits through partially amphibolized two-pyroxene dolerite to garnet-plagioclase amphibolite. These changes are not accompanied by conspicuous changes in bulk composition. The garnetiferous varieties represent a border facies of the dyke, which is in contact with little-altered pyroxene-bearing gneisses of the Lewisian complex. The fourth specimen is a hornblende schist formed from the dolerite by shearing. This change also involves little change in bulk composition, and affects impartially the three types of dolerite referred to above. Mineral relations are discussed and a hypothesis advanced to account for the garnetiferous border facies of the intrusion, invoking intrusion while the country rock was at relatively high temperature and pressure.

Mineralogical Magazine; September 1961 v. 32; no. 254; p. 848-865; DOI: 10.1180/minmag.1961.032.254.02
© 1961, The Mineralogical Society
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