Paleomagnetism of the Mississippian HP Pipe and the Western Margin of the North American Craton

  1. John W. Hillhouse
  1. D.T.A. Symons and
  2. M.T. Lewchuk

Published Online: 18 MAR 2013

DOI: 10.1029/GM050p0113

Deep Structure and Past Kinematics of Accreted Terranes

Deep Structure and Past Kinematics of Accreted Terranes

How to Cite

Symons, D.T.A. and Lewchuk, M.T. (1989) Paleomagnetism of the Mississippian HP Pipe and the Western Margin of the North American Craton, in Deep Structure and Past Kinematics of Accreted Terranes (ed J. W. Hillhouse), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM050p0113

Author Information

  1. Department of Geology, University of Windsor, Windsor, Ontario, Canada N9B 3P4

Publication History

  1. Published Online: 18 MAR 2013
  2. Published Print: 1 JAN 1989

ISBN Information

Print ISBN: 9780875904542

Online ISBN: 9781118666609

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Keywords:

  • Geology, Structural—Congresses;
  • Geodynamics—Congresses;
  • Earth—Crust—Congresses

Summary

The HP pipe is a small oval (80m×40m) kimberlitic diatreme near Golden, B.C., in the fold-and-thrust belt of the Rocky Mountains. The pipe intrudes gently-dipping (∼10°S) Late Cambrian to Middle Ordovician limestones with nearly vertical contacts. It is comprised of carbonate breccia fragments and pyroxenite nodules in a light-green serpentine matrix and gives a Rb-Sr age of 348±7 Ma. A later phase of dark-green dikes cut the breccia and adjacent limestones. AF and thermal step demagnetization of 168 specimens from 42 oriented blocks was done using an automated cryogenic magnetometer in a shielded room for remanence measurement. The diatreme breccia and dikes retain a stable A remanence component after thermal cleaning above ∼400°C and AF cleaning above ∼20 mT. Their combined mean direction of 129.8°, −44.3° (α95 = 6.5°) after tilt correction gives a concordant Mississippian pole position of 138.5°E, 44.5°N (Dp = 5.1°, Dm = 8.2°). The limestones provide a positive contact test by giving a stable B component direction of 114.4°, −22.7° (α95 = 12.4°) with a concordant Late Cambrian to Middle Ordovician pole of 141.0°E, 24.3°N (δp = 7.0°, δm = 13.3°). These concordant poles indicate that the fold-and-thrust belt is part of the North American craton. Thus the suture with allochthonous terranes to the west must be located at or west of the Rocky Mountain Trench. Both the diatreme and limestones retain a low-coercivity and unblocking-temperature C component, isolated by vector subtraction without tilt correction, that records a minor overprint from the Laramide Orogeny combined with Pleistocene viscous remanence.