Anorthoclase Megacrysts: Physical Conditions of Formation

Dov Bahat
Department of Geology and Mineralogy, Ben Gurion University of the Negev Beer Sheva, Israel

Summary: Previous interpretations relating to precipitation of anorthoclase megacrysts from alkaline basaltic magmas under high-pressure conditions are contradicted. It is proposed that these feldspars were crystallized above the solvus from hydrous melts at shallow depths, under low-pressure equilibrium conditions. These melts had been considerably enriched with volatiles of sodium, strontium, and barium, and to some extent also of rubidium.

Mineralogical Magazine; June 1979 v. 43; no. 326; p. 287-291; DOI: 10.1180/minmag.1979.043.326.11
© 1979, The Mineralogical Society
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