Analcime phenocrysts in a vitrophyric analcimite — Primary or secondary?

✍ Scribed by J. F. G. Wilkinson

• Publisher: Springer
• Year: 1977
• Tongue: English
• Weight: 879 KB
• Volume: 64
• Category: Article
• ISSN: 0010-7999
• DOI: 10.1007/bf00375282

✦ Synopsis

A vitrophyric analcimite contains phenocrysts of analcime and olivine in a groundmass of titansahlite, titanomagnetite, apatite, and abundant glass. The chemistry of the analcimite and its vitric residuum, the crystallization history of the host, and experimental data collectively favour an interpretation that the analcime "phenocrysts" are ion-exchanged KAI-Si20 6 leucites. Conversion of leucite to analcime resulted from two-way diffusion involving Na + and H20, and K + across the original leucite-glass interfaces and probably was largely accomplished during hydration of the vitric groundmass.