Distribution of the glass phase in hot-pressed, olivine-basalt aggregates: An electron microscopy study

P. J. Vaughan, D. L. Kohlstedt

Research output: Contribution to journalArticle

45 Scopus citations

Abstract

Samples of olivine mixed with small amounts of tholeiitic basalt which were hot-pressed above the solidus temperature were examined by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) techniques. Two sets of samples were compared. One set was hot-pressed for approximately 1 h near 1,300° C at 0.2 GPa, and the other set was held for approximately 200 h near 1,250° C at 1.0 GPa. SEM observations reveal that, in samples which were hot-pressed for 1 h, the glass phase occurs in irregular pockets surrounded by four or five olivine grains as well as in triple junctions. The crystal-glass interfaces show both positive and negative curvature. These observations and the presence of voids suggest that the microstructure is far from textural equilibrium. In contrast, in samples which were hot-pressed for 200 h, glass is largely confined to triple junctions of uniform size and the crystal-glass interfaces have uniform curvature indicating a much greater degree of textural equilibrium. TEM images reveal layers of glass 10-50 nm thick along most of the grain boundaries in the samples annealed for short times. However, within the limit of resolution, ∼2 nm, virtually all of the grain boundaries in the samples hot-pressed for long times appear to contain no glass. These observations indicate that segregation of melt from grain boundaries to triple junctions is an integral part of the process of textural equilibration.

Original languageEnglish (US)
Pages (from-to)253-261
Number of pages9
JournalContributions to Mineralogy and Petrology
Volume81
Issue number4
DOIs
StatePublished - Dec 1 1982

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