Grandidierite from a Pelitic Xenolith in the Haddo House Complex, NE Scotland

R. K. Herd, B. F. Windley and D. Ackermand
Geological Survey of Canada, 601 Booth Street, Ottawa, Ontario K1A OE8, Canada
Department of Geology, The University, Leicester LE1 7RH, United Kingdom
Mineralogisches Institut der Universität, D-2300 Kiel, Federal Republic of Germany

Abstract: Grandidierite occurs in the outer margin of a biotite-rich pelitic xenolith in norite close to the contact of a tourmaline-bearing granite in the Haddo House norite-gabbro complex. The boron for the grandidierite was derived by metasomatism from the granite. The assemblage is (decreasing order): An55–51 plagioclase (65%), biotite (10%), spinel (10%), cordierite (5%), corundum (5%), ilmenite, grandidierite (< 1%), rutile, sphene, zircon. XMg range is grandidierite (0.80–0.78) > cordierite (0.78) > biotite (c. 0.59) > spinel (0.35–0.27). The grandidierite has little chemical variation: SiO2, 19.9–20.5%; Al2O3, 51.3–51.9%. A compilation of all grandidierite analyses in the literature shows that the only substitutions are Fe2+ ⇌ Mg and Al ⇌ Fe3+, the XMg range being 0.98 to 0.19.

Mineralogical Magazine; September 1984 v. 48; no. 348; p. 401-406; DOI: 10.1180/minmag.1984.048.348.11
© 1984, The Mineralogical Society
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