Quick Search:    advanced search

GSW Home   GeoRef Home   My GSW Alerts   Contact GSW   About GSW   Journals List   Help

This Article Free via Open Access: OA Figures Only OA Full Text Full Text (PDF) Movies Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Madsen, J.K. Articles by Marshall, D.D. Search for Related Content GeoRef GeoRef Citation

Cenozoic to Recent plate configurations in the Pacific Basin: Ridge subduction and slab window magmatism in western North America

J.K. Madsen*1, D.J. Thorkelson*1, R.M. Friedman*2 and D.D. Marshall*3

¹ Department of Earth Sciences, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
² Pacific Centre for Isotopic and Geochemical Research, Department of Earth and Ocean Science, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
³ Department of Earth Sciences, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada

Forearc magmatic rocks were emplaced in a semicontinuous belt from Alaska to Oregon from 62 to 11 Ma. U-Pb and ⁴⁰Ar-³⁹Ar dating indicates that the magmatism was concurrent in widely separated areas. Eight new conventional isotope dilution–thermal ionization mass spectrometry (ID-TIMS) U-Pb zircon ages from forearc intrusions on Vancouver Island (51.2 ± 0.4, 48.8 ± 0.5 Ma, 38.6 ± 0.1, 38.6 ± 0.2, 37.4 ± 0.2, 36.9 ± 0.2, 35.4 ± 0.2, and 35.3 ± 0.3 Ma), together with previous dates, indicate that southwestern British Columbia was a particularly active part of the forearc. The forearc magmatic belt has been largely attributed to ridge-trench intersection and slab window formation involving subduction of the Kula-Farallon ridge. Integration of the new and previous ages reveals shortcomings of the Kula-Farallon ridge explanation, and supports the hypothesis of two additional plates, the Resurrection plate (recently proposed) and the Eshamy plate (introduced herein) in the Pacific basin during Paleocene and Eocene time. We present a quantitative geometric plate-tectonic model that was constructed from 53 Ma to present to best account for the forearc magmatic record using ridge-trench intersection and slab window formation as the main causes of magmatism. The model is also in accord with Tertiary to present inboard magmatic and structural features.

Keywords: tectonics • magmatism • geochronology • forearc • slab window • ridge subduction • western North America • Cordillera

This article has been cited by other articles:

				H. MIRNEJAD and K. BELL Origin and Source Evolution of the Leucite Hills Lamproites: Evidence from Sr-Nd-Pb-O Isotopic Compositions J. Petrology, December 1, 2006; 47(12): 2463 - 2489. [Abstract] [Full Text] [PDF]