Early Ordovician development of the Macquarie Arc, Lachlan Orogen, New South Wales

R. A. Glen*, A. J. Crawford, I. G. Percival, L. M. Barron

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

39 Citations (Scopus)


The first recorded igneous activity of the now-fragmented Macquarie Arc in central New South Wales began in Early Ordovician (Lancefieldian-Bendigonian) times. In the westernmost Junee-Narromine Volcanic Belt, mafic to intermediate lavas of the Nelungaloo Volcanics, intruded by monzonite at 481Ma, pass up into sandstone, conglomerate and siliceous siltstone of the Lancefieldian to early Bendigonian Yarrimbah Formation. Further east, in the northern Molong Volcanic Belt, the Mitchell Formation consists of volcaniclastic conglomerate, sandstone and siltstone with minor lavas and is succeeded conformably by volcaniclastic granule conglomerate, sandstone and siltstone of the middle-late Bendigonian Hensleigh Siltstone. This earliest phase of volcanism in the Macquarie Arc is dominated by high-K calc-alkaline to shoshonitic evolved basalt, basaltic andesite and andesite, but felsic lavas with SiO2 < 63% are absent. Age-corrected εNd values for five lavas range from +6.2 to +7.8, indicating an absence of any old continental crustal component in the petrogenesis of these volcanic rocks. Together, these data suggest formation of the Macquarie Arc as an intra-oceanic arc, probably built on Cambrian oceanic crust.

Original languageEnglish
Pages (from-to)167-179
Number of pages13
JournalAustralian Journal of Earth Sciences
Issue number2-3
Publication statusPublished - Mar 2007
Externally publishedYes


  • Geochemistry
  • Lachlan Orogen
  • Macquarie Arc
  • Ordovician
  • Petrology
  • Stratigraphy


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