A Very Ancient Island Arc

  1. Leon Knopoff,
  2. Charles L. Drake and
  3. Pembroke J. Hart
  1. R. E. Folinsbee,
  2. H. Baadsgaard,
  3. G. L. Cumming and
  4. D. C. Green

Published Online: 18 MAR 2013

DOI: 10.1029/GM012p0441

The Crust and Upper Mantle of the Pacific Area

The Crust and Upper Mantle of the Pacific Area

How to Cite

Folinsbee, R. E., Baadsgaard, H., Cumming, G. L. and Green, D. C. (2012) A Very Ancient Island Arc, in The Crust and Upper Mantle of the Pacific Area (eds L. Knopoff, C. L. Drake and P. J. Hart), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM012p0441

Author Information

  1. Departments of Geology and Physics, University of Alberta, Edmonton, Alberta, Canada

Publication History

  1. Published Online: 18 MAR 2013
  2. Published Print: 20 APR 2012

Book Series:

  1. Geophysical Monograph Series

Book Series Editors:

  1. Waldo E. Smith

ISBN Information

Print ISBN: 9780875900124

Online ISBN: 9781118663738



  • Ancient island arcs;
  • Granitic Plutons;
  • K/Ar dates;
  • Kenoran orogeny;
  • Rb/Sr isochron;
  • Rubidium-strontium radiometric dating;
  • Volcanic piles;
  • Yellowknife and Cameron River volcanic belts


In the early Precambrian of the Slave Province, Yellowknife area, N.W.T., Canada, mafic volcanic piles accumulated to heights of 2000 to 12000 meters, presumably as ancient island arcs. The pattern of eruption at Yellowknife commenced with the outpouring of a thick sequence of tholeiitic basalts and terminated with a thinner sequence of quartz latites and dacites, following in general the differentiation patterns noted by Kuno. A rubidium-strontium isochron suggests that these volcanics poured out in submarine eruptions 2.6 billion years ago. If, as has been suggested, the volcanic piles rest on basement gneisses (granodiorites), these gneisses must be amongst the most ancient crustal rocks known in North America. However, Rb/Sr and K/Ar dates of 2.5 to 2.6 b.y. for the granodiorites suggest that either the granite rocks are for the most part younger than the volcanics or that they were completely updated during the general period of Kenoran orogeny and intrusion at the close of the Archean.