Coexisting Glasses Occurring as Inclusions in Leucite from Lamproites: Examples of Silicate Liquid Immiscibility in Ultrapotassic Magmas

Roger H. Mitchell
Department of Geology, Lakehead University, Thunder Bay, Ontario, Canada P7B 5E1

Abstract: Inclusions occurring in leucites from the Oscar and Zirkel Mesa leucite lamproites consist of high (>10 wt.%) and low (<4 wt.%) K2O discrete glass phases which are interpreted to have resulted from silicate liquid immiscibility. Both glasses are quartz-normative and rich in Ti, Fe, Mg, Ca and Ba and poor in A1. The high-K glass is strongly peralkaline. Neither of the glasses have compositions representative of any known lamproites. These inclusions represent the first described examples of silicate-silicate immiscibility shown by glass in alkaline rocks.

Keywords: leucite • inclusions • glasses • lamproite • silicate liquids • immiscibility

Mineralogical Magazine; June 1991 v. 55; no. 379; p. 197-202; DOI: 10.1180/minmag.1991.055.379.07
© 1991, The Mineralogical Society
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