A Possible Exposed Conrad Discontinuity in the Kapuskasing Uplift, Ontario

  1. Muawia Barazangi and
  2. Larry Brown
  1. John A. Percival

Published Online: 15 MAR 2013

DOI: 10.1029/GD014p0135

Reflection Seismology: The Continental Crust

Reflection Seismology: The Continental Crust

How to Cite

Percival, J. A. (1986) A Possible Exposed Conrad Discontinuity in the Kapuskasing Uplift, Ontario, in Reflection Seismology: The Continental Crust (eds M. Barazangi and L. Brown), American Geophysical Union, Washington, D. C.. doi: 10.1029/GD014p0135

Author Information

  1. Precambrian Geology Division, Geological Survey of Canada, Ottawa, Ontario KlA 0E4

Publication History

  1. Published Online: 15 MAR 2013
  2. Published Print: 1 JAN 1986

Book Series:

  1. Geodynamics Series

ISBN Information

Print ISBN: 9780875905143

Online ISBN: 9781118670118

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Keywords:

  • Earth—Crust—Congresses;
  • Continents—Congresses;
  • Seismic reflection method—Congresses

Summary

Mid-crustal seismic velocity discontinuities have been recorded at several localities in the Archean Superior Province of the Canadian Shield. In the central part of the province, the Kapuskasing uplift exposes a relatively complete oblique section through the upper two-thirds of the crust. At a structural depth within the uplift of approximately 20 km, based on geobarometry of metamorphic assemblages, a complex transition occurs between an upper region consisting dominantly of tonalitic gneiss in the amphibolite facies (average density ∼2.70 g·cm−3) and a lower level of interlayered tonalite, diorite, anorthosite, paragneiss and mafic gneiss in the upper amphibolite and granulite facies (average density ∼2.82 g·cm−3). The transition zone, thought to be analogous to a mid-crustal velocity discontinuity, separates upper crust, in which felsic plutonic compositions predominate, from lower crust, where intrusive rocks include mafic tonalite, diorite and anorthosite.