Contributions to Mineralogy and Petrology

, Volume 88, Issue 4, pp 354–371 | Cite as

Origin and evolution of a peraluminous silicic ignimbrite suite: The Violet Town Volcanics

  • John D. Clemens
  • Victor J. Wall


The Violet Town Volcanics are a 373 Ma old, comagmatic, S-type volcanic sequence mainly comprising crystal-rich intracaldera ignimbrites. Rock types vary from rhyolites to rhyodacites, all containing magmatic cordierite and garnet phenocrysts. Variation in the suite is primarily due to fractionation of early-crystallized quartz, plagioclase and biotite (plus minor accessory phases) in a high-level magma chamber prior to eruption. Early magmatic crystallization occurred at around 4 kb and 850° C with melt water contents between 2.8 and 4 wt.%. This high-temperature, markedly water-undersaturated, restite-poor, granitic magma was generated by partial melting reactions involving biotite breakdown in a dominantly quartzofeldspathic source terrain, leaving a granulite facies residue.

Table of Less Common Abbreviations Used


pressure in kilobars

T° C

temperature in degrees Celsius

\(X_{H_2 O}^{Fl} \)

mole fraction of water in the fluid


activity of water




















potassium feldspar














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Copyright information

© Springer-Verlag 1984

Authors and Affiliations

  • John D. Clemens
    • 1
  • Victor J. Wall
    • 1
  1. 1.Earth Sciences DepartmentMonash UniversityClaytonAustralia

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