Evidence from Feldspar Compositions of High Temperatures in Granite Sheets in the Scourian Complex, N.W. Scotland

Hugh R. Rollinson
Department of Earth Sciences, The University, Leeds, LS2 9JT*
*Present Address: Department of Geography and Geology, College of St. Paul and St. Mary, The Park, Cheltenham, Glos. GL50 2RH.

Abstract: Mesoperthite feldspars from hypersolvus granites, with granulite-facies mineralogy from the Scourian complex, N.W. Scotland have an average bulk composition of (Ab0.58Or0.42)88An12. The mesoperthites have an Ab/Or ratio close to the critical composition of the alkali feldspar solvus for anorthite-free compositions. The critical temperature of the ternary feldspar solvus is estimated at high anorthite contents and used to indicate a temperature in excess of 1000°C for the crystallization of the granite sheets prior to granulite-facies metamorphism and permits a maximum water content in the melt of 1%.

Mineralogical Magazine; March 1982 v. 46; no. 338; p. 73-76; DOI: 10.1180/minmag.1982.046.338.12
© 1982, The Mineralogical Society
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