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Deep Probe - Imaging the roots of western North America

Deep Probe - Imaging the roots of western North America
Deep Probe - Imaging the roots of western North America
Analysis of the Lithoprobe Deep Probe and Southern Alberta Refraction Experiment data sets, focusing on the region between Deep Probe shots 43 and 55, has resulted in a continental-scale velocity structural model of the lithosphere of platformal western Laurentia reaching depths of ~150 km. Three major lithospheric blocks were investigated: (i) the Hearne Province, a typical continental Archean cratonic province lying beneath the Western Canada Sedimentary Basin; (ii) the Wyoming Province, an even older block of Phanerozoic-modified Archean crust with an enigmatic lower lithosphere; and (iii) the Yavapai–Mazatzal Province, Proterozoic terranes underlying the Colorado Plateau and Southern Rocky Mountains. In this study, the northern two of these regions are investigated with a modified ray-theoretical traveltime inversion routine that respects the spherical geometry of the Earth. The resulting crustal velocity structure, combined with supporting geological and geophysical data, reveals that the Medicine Hat block (MHB), lying between the Hearne and Wyoming provinces, is a third independent Archean crustal block. The subcrustal lithosphere along the profile is homogeneous in velocity structure, but two significant northward-dipping reflectors are apparent and interpreted as relic subduction zones associated with sutures between the three Archean blocks. The Hearne crust is typical of an Archean shield or platform both in its thickness of 34–50 km and its seismic velocity structure. The crust of the Archean MHB and Wyoming Province, which ranges in thickness from 49 to 60 km, includes a 10–30 km thick high-velocity layer, interpreted to be Proterozoic in age. Such a feature is unexpected beneath Archean crustal provinces, but if the region is considered to be the remanent marginal portion of a larger Archean continent, then the interpreted Proterozoic underplating and lack of an Archean lithospheric root can be explained. The variable topography along the reflective upper and lower boundaries of this layer, especially within the MHB, suggests considerable variability in its emplacement and subsequent tectonic history.
375-398
Gorman, A.R.
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Clowes, R.M.
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Ellis, R.M.
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Henstock, T.J.
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Spence, G.D.
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Keller, G.R.
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Levander, A.R.
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Snelson, C.M.
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Burianyk, M.J.A.
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Kanasewich, E.R.
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Asudeh, I.
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Hajnal, Z.
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Miller, K.C.
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Gorman, A.R.
d64fb3d3-6eb4-4b19-a893-83bd5904652e
Clowes, R.M.
545b3b9e-756f-4b92-92d3-cf9185a2e386
Ellis, R.M.
f0c0b414-0ed1-42a0-8c68-ce961cba17ae
Henstock, T.J.
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Spence, G.D.
edb5fc92-da6d-46c5-902a-9c29bbc199f2
Keller, G.R.
8e983a4a-be7a-481c-ae33-ad371489bace
Levander, A.R.
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Snelson, C.M.
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Burianyk, M.J.A.
8622f242-9c4a-4500-a1db-932350e22b4e
Kanasewich, E.R.
8a3d2499-9651-4139-95de-f24e7a677a60
Asudeh, I.
61948848-1458-4dd0-bc5e-ed0666b54a61
Hajnal, Z.
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Miller, K.C.
b61efb68-e161-461f-aeb8-9242d8307b55

Gorman, A.R., Clowes, R.M., Ellis, R.M., Henstock, T.J., Spence, G.D., Keller, G.R., Levander, A.R., Snelson, C.M., Burianyk, M.J.A., Kanasewich, E.R., Asudeh, I., Hajnal, Z. and Miller, K.C. (2002) Deep Probe - Imaging the roots of western North America. Canadian Journal of Earth Sciences, 39, 375-398.

Record type: Article

Abstract

Analysis of the Lithoprobe Deep Probe and Southern Alberta Refraction Experiment data sets, focusing on the region between Deep Probe shots 43 and 55, has resulted in a continental-scale velocity structural model of the lithosphere of platformal western Laurentia reaching depths of ~150 km. Three major lithospheric blocks were investigated: (i) the Hearne Province, a typical continental Archean cratonic province lying beneath the Western Canada Sedimentary Basin; (ii) the Wyoming Province, an even older block of Phanerozoic-modified Archean crust with an enigmatic lower lithosphere; and (iii) the Yavapai–Mazatzal Province, Proterozoic terranes underlying the Colorado Plateau and Southern Rocky Mountains. In this study, the northern two of these regions are investigated with a modified ray-theoretical traveltime inversion routine that respects the spherical geometry of the Earth. The resulting crustal velocity structure, combined with supporting geological and geophysical data, reveals that the Medicine Hat block (MHB), lying between the Hearne and Wyoming provinces, is a third independent Archean crustal block. The subcrustal lithosphere along the profile is homogeneous in velocity structure, but two significant northward-dipping reflectors are apparent and interpreted as relic subduction zones associated with sutures between the three Archean blocks. The Hearne crust is typical of an Archean shield or platform both in its thickness of 34–50 km and its seismic velocity structure. The crust of the Archean MHB and Wyoming Province, which ranges in thickness from 49 to 60 km, includes a 10–30 km thick high-velocity layer, interpreted to be Proterozoic in age. Such a feature is unexpected beneath Archean crustal provinces, but if the region is considered to be the remanent marginal portion of a larger Archean continent, then the interpreted Proterozoic underplating and lack of an Archean lithospheric root can be explained. The variable topography along the reflective upper and lower boundaries of this layer, especially within the MHB, suggests considerable variability in its emplacement and subsequent tectonic history.

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Published date: 2002

Identifiers

Local EPrints ID: 12669
URI: http://eprints.soton.ac.uk/id/eprint/12669
PURE UUID: 23cdafe1-3fc1-41d8-984c-04238848e0a5
ORCID for T.J. Henstock: ORCID iD orcid.org/0000-0002-2132-2514

Catalogue record

Date deposited: 29 Nov 2004
Last modified: 10 Nov 2021 02:59

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Contributors

Author: A.R. Gorman
Author: R.M. Clowes
Author: R.M. Ellis
Author: T.J. Henstock ORCID iD
Author: G.D. Spence
Author: G.R. Keller
Author: A.R. Levander
Author: C.M. Snelson
Author: M.J.A. Burianyk
Author: E.R. Kanasewich
Author: I. Asudeh
Author: Z. Hajnal
Author: K.C. Miller

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