The study area of the SNORCLE Lithoprobe transect comprises the northern Canadian
Cordillera and the northwestern Canadian shield. An array of five portable broadband seismographs
has been deployed along the trend of the transect, to complement five permanent
stations of the Canadian National Seismic Network and seven Alaskan short-period instruments.
The objective of the experiment is to examine the physical state of the upper mantle along the
transect. P-wave travel-time residuals up to 2 seconds have been measured, and analyzed using
a non-linear tomographic technique, thereby recovering velocity structure between 100 and 600
km depth for the western portion of the transect.
Two significant P-wave mantle velocity anomalies have been located. The first, a relatively
shallow high-velocity feature located at the western edge of the model, has been interpreted as
being the edge of the Pacific slab from the southern Alaska subduction zone. The second is a
large, tabular low-velocity anomaly centered at 60°N by 136°W, elongate northwest-southwest,
dipping southeast, and reaching a depth of 450-500 km. This low-velocity anomaly is judged
to reflect a thermal anomaly of the order of 100°C, with a possible compositional component.
Multiple interpretations of the low-velocity feature are considered, the two main hypotheses
being a mantle plume or a flow feature related to the proximity of the subducting slab and
the opening of the northern Cordilleran slab window. The latter hypothesis is favored, due to
the absence of other evidence for a plume in this region. In addition, the upper part of the
low-velocity anomaly may reflect the influence of strain heating at lithospheric levels, related
to the convergence of the Pacific and North American plates and the uplift of the St. Elias
Mountains. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate
| Identifer | oai:union.ndltd.org:UBC/oai:circle.library.ubc.ca:2429/5862 |
| Date | 05 1900 |
| Creators | Frederiksen, Andrew William |
| Source Sets | University of British Columbia |
| Language | English |
| Detected Language | English |
| Type | Text, Thesis/Dissertation |
| Format | 6258688 bytes, application/pdf |
| Rights | For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use. |
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