Mineralogy of Vesicles in an Olivine Leucitite at Cosgrove, Victoria, Australia

W. D. Birch
Department of Mineralogy, National Museum of Victoria, Russell Street, Melbourne, Victoria. 3000

Summary: An olivine-titanomagnetite-apatite-clinopyroxene-mica-nepheline-feldspar assemblage occurs in late-stage vesicles in a small outcrop of olivine leucitite at Cosgrove, Victoria. The vesicles were formed by exsolution of volatiles at an early stage in the cooling history of the lava. Subsequently, a volatile-rich residual liquid filled cavities and fractures, giving rise to a coarse-grained pegmatoid rock type similar in over-all mineralogy to the vesicles. The volatiles facilitating crystallization in both the vesicles and the pegmatoid were probably enriched in F, CO2, and P. A number of geothermometers applied to the vesicle assemblage failed to agree on likely crystallization temperatures.

Mineralogical Magazine; March 1980 v. 43; no. 329; p. 597-603; DOI: 10.1180/minmag.1980.043.329.06
© 1980, The Mineralogical Society
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