Geochemical character and tectonic significance of Early Devonian keratophyres in the New England Fold Belt, eastern Australia

Peter A. Cawood, Richard H. Flood

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Extrusive and high level intrusive Early Devonian keratophyres are the oldest in situ igneous rocks in the Tamworth Block of the New England Fold Belt of eastern Australia. They show extensive evidence of degradation, including the destruction of magmatic phases, the growth of low grade metamorphic minerals, and changes in composition involving the dilution of elemental abundances in response to silica addition. Relations between the less mobile minor and trace elements, and limited data on clinopyroxene compositions, lead to the conclusion that these Early Devonian volcanic rocks are mostly calc-alkaline volcanic arc andesites with minor dacite. These rocks unconformably overlie a sequence of Early Palaeozoic forearc basin deposits, indicating that the Early Devonian marks a period of readjustment of tectonic elements within the New England Fold Belt, associated with a marked east-directed stepping out of the magmatic arc. Generation of the keratophyres in a subduction zone environment limits the position of the trench to 100 km east of the Peel Fault System.

Original languageEnglish
Pages (from-to)297-311
Number of pages15
JournalAustralian Journal of Earth Sciences
Issue number2
Publication statusPublished - 1 Jan 1989
Externally publishedYes


  • Andesite
  • Calc-alkaline
  • Eastern australia
  • Keratophyre
  • Spilite

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