Origin and Emplacement of Neogene and Quaternary Lavas in the Canadian Cordillera
Date
2025
Authors
Sanderson, Kayla
Journal Title
Journal ISSN
Volume Title
Publisher
University Of Victoria
Abstract
The depth of formation of Neogene and younger (<28 Ma) alkaline volcanism hosting mantle xenoliths in the back arc of the Canadian Cordillera can be used to constrain the depth to the lithosphere-asthenosphere boundary (LAB). This informs on the lithosphere thickness, strength, and susceptibility of deformation. Clinopyroxene and olivine phenocrysts hosted in alkaline lava samples from three locations in the Canadian Cordillera were analyzed using LA-ICPMS and electron microprobe. Major and trace element chemistry of these phenocrysts are used to estimate the pressure and temperature of formation, and test for equilibrium. Formation temperatures of phenocrysts were estimated using nickel and iron-magnesium thermometers. Growth patterns in clinopyroxene were used to estimate lava ascent times from experimentally determined growth rates. Lava ascent times at Summit Lake ranged from 2 hours to 13.9 days. Depth of formation of clinopyroxene phenocrysts at Summit Lake were estimated to be between 36 and 40 km, suggesting that the lava stalled beneath the crust-mantle boundary before rapid ascent and emplacement.
Description
Keywords
Cordillera, geothermometry, geobarometry, olivine, clinopyroxene, lava