Distribution, Nature, and Origin of Neogene–Quaternary Magmatism in the Northern Cordilleran Volcanic Province, Canada
Distribution, nature, and origin of Neogene–Quaternary magmatism in the northern Cordilleran volcanic province, Canada Benjamin R. Edwards* Igneous Petrology Laboratory, Department of Earth and Ocean Sciences, James K. Russell } University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada ABSTRACT Cordillera, driven by changes in relative these diverse volcanic rocks in space and time. plate motion between the Pacific and North We then use the compiled petrological and geo- The northern Cordilleran volcanic province American plates ca. 15–10 Ma. chemical data to address the origins of this alka- encompasses a broad area of Neogene to Qua- line magmatism and the structure of the litho- ternary volcanism in northwestern British Keywords: alkaline basalt, Canada, Cordil- sphere beneath the northern Cordilleran volcanic Columbia, the Yukon Territory, and adjacent leran, magmatism, Quaternary, volcanism. province. Specifically, we determine the source eastern Alaska. Volcanic rocks of the north- region characteristics of northern Cordilleran ern Cordilleran volcanic province range in INTRODUCTION volcanic province magmas using trace element age from 20 Ma to ca. 200 yr B.P. and are and isotopic data, and we produce a petrological dominantly alkali olivine basalt and hawai- Neogene to Quaternary magmatism in the image of the lithosphere using phase equilibria ite. A variety of more strongly alkaline rock Cordillera of North America is closely related to calculations for lavas and mantle peridotite types not commonly found in the North the current tectonic configuration between the xenoliths. Results of this analysis provide a basis American Cordillera are locally abundant in North American, Pacific, and Juan de Fuca plates on which to amplify the tectonic model we have the northern Cordilleran volcanic province.
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