Grandidierite from Aluminous Metasedimentary Xenoliths Within Acid Volcanics, a First Record in Italy

Manfred J. van Bergen
Department of Structural and Applied Geology, Geological Institute, State University of Utrecht, Budapestlaan 4, Utrecht, the Netherlands

Summary: Grandidierite has been identified in two aluminous metasedimentary xenoliths from quartz-latitic volcanic rocks from Mt. Amiata and Mt. Cimino, central Italy. Physical and electron microprobe data for the grandidierites and petrological data for the grandidierite-bearing xenoliths are presented. The grandidierites formed by a reaction involving pre-existing aluminium rich minerals, possibly at temperatures of at least 800 °C and at low pressures. The grandidierite from Mt. Amiata replaces sillimanite. Several common characteristics can be demonstrated for magmatic and metamorphic grandi-dierite-bearing rocks. It is suggested that metamorphic rocks in which grandidierite occurs have often undergone partial melting.

Mineralogical Magazine; March 1980 v. 43; no. 329; p. 651-658; DOI: 10.1180/minmag.1980.043.329.15
© 1980, The Mineralogical Society
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