Ian Ferguson - Academia.edu (original) (raw)
Papers by Ian Ferguson
Canadian Journal of Earth Sciences, 2005
Page 1. Electromagnetic images of the Trans-Hudson orogen: the North American Central Plains anom... more Page 1. Electromagnetic images of the Trans-Hudson orogen: the North American Central Plains anomaly revealed1, 2 Alan G. Jones, Juanjo Ledo, and Ian J. Ferguson Abstract: Magnetotelluric studies of the Trans-Hudson ...
Canadian Journal of Earth Sciences, 2005
Abstract: Magnetotelluric (MT) measurements to image the three-dimensional resistivity structure ... more Abstract: Magnetotelluric (MT) measurements to image the three-dimensional resistivity structure of the North American continent from an Archean core to a region of Tertiary assembly were recorded at almost 300 sites along 3200 km of profiles on the Lithoprobe Slave Northern ...
Geology, 1993
Magnetotelluric data acquired across the Paleoproterozoic Trans-Hudson orogen, northern Saskatche... more Magnetotelluric data acquired across the Paleoproterozoic Trans-Hudson orogen, northern Saskatchewan, image one of the world's longest crustal features, the North American Central Plains conductivity anomaly. Modeling shows the anomaly at this latitude to comprise two distinct, westward-dipping bodies of high conductivity lying structurally above a late collisional feature, the Guncoat thrust. The shallower of these bodies correlates with the western part of the La Ronge belt; the deeper body at mid-crustal depths underlies the Wathaman batholith, and its western boundary is close to the inferred subsurface extension of the subvertical Needle Falls shear zone. The anomaly is identified with interleaved, biotitic, metasedimentary rocks of the Nemeiben zone and Cree Lake belt and is interpreted to have been thrust beneath the margin during collision of the La Ronge arc with the Rae-Hearne continent via westward-directed subduction.
Physics of the Earth and Planetary Interiors, 2005
... Apparent resistivity responses indicate the ca 3.0 Ga North Caribou terrane contains extremel... more ... Apparent resistivity responses indicate the ca 3.0 Ga North Caribou terrane contains extremely resistive crust. ... The results suggest that the supracrustal component of the North Caribou terrane provides minimal enhancement of the crustal conductivity. ...
Lithos, 2003
The Slave craton in northwestern Canada, a relatively small Archean craton (600 Â 400 km), is ide... more The Slave craton in northwestern Canada, a relatively small Archean craton (600 Â 400 km), is ideal as a natural laboratory for investigating the formation and evolution of Mesoarchean and Neoarchean sub-continental lithospheric mantle (SCLM). Excellent outcrop and the discovery of economic diamondiferous kimberlite pipes in the centre of the craton during the early 1990s have led to an unparalleled amount of geoscientific information becoming available.
Journal of Geophysical Research, 2004
1] Two goals of Lithoprobe's geoscientific studies in the Phanerozoic accretionary cordillera of ... more 1] Two goals of Lithoprobe's geoscientific studies in the Phanerozoic accretionary cordillera of western North America were to define the subsurface geometries of the terranes and to infer the physical conditions of the crust. These questions were addressed in Canada's southern cordillera a decade ago and have more recently been addressed in the northern cordillera, of which one component of the new studies is magnetotelluric (MT) profiling from ancestral North American rocks to the coast. We present a resistivity cross section, and its interpretation, of the northern cordillera derived from modeling data from 42 MT sites along a 470-km-long NE-SW profile. Beneath the Coast Belt (southwestern end of the profile) a deep crustal low-resistivity layer dips inland; we interpret the crustal part of this conductor as being due to metasedimentary rocks emplaced and metamorphosed during Paleocene Kula plate subduction. A strong lateral transition in lithospheric mantle resistivity exists below the Intermontane Belt that is spatially coincident with changes in chemical and isotopic characteristics of Tertiary to recent alkaline lavas, suggesting that isotopically enriched lithosphere related to the Coast Belt basalts extends partly beneath the Intermontane Belt. The unusually high lower crustal resistivity in the Intermontane and Omineca Belts, similar in value to the resistivity found in the unextended part of central British Columbia, excludes the presence of fluids or conducting metasediments. Finally, our resistivity model displays strong lateral variation of the middle and lower crust between different terranes within the same belt, as a result of the complex structural evolution of the lithosphere.
Geophysical Research Letters, 2002
1] Wideband magnetotelluric (MT) data were acquired along three profiles crossing the strike-slip... more 1] Wideband magnetotelluric (MT) data were acquired along three profiles crossing the strike-slip Tintina Fault in northwestern Canada. The MT responses obtained exhibit remarkable similarity from all three profiles, implying similar two-dimensional (2-D) electromagnetic behavior of the fault zone over a strike length of at least 350 km. Analyses of the MT responses for dimensionality corroborate the validity of assuming regional 2-D structures in interpretation. Several high conductivity anomalies at different depth scales are present in the models obtained, and we suggest that both the shallow structures and the deep crustal scale anomalies are caused by electronic conduction mechanisms in interconnected mineralized zones. Intriguingly, the middle and lower crust beneath the surface expression of the Tintina Fault is highly resistive, in contrast to some other large-scale strike-slip faults. This implies that fault zone processes that result in interconnected conducting phases are not generic in nature but are controlled by local conditions.
Geology, 2001
The Archean Slave craton in northwestern Canada is an ideal natural laboratory for investigating ... more The Archean Slave craton in northwestern Canada is an ideal natural laboratory for investigating lithosphere formation and evolution, and has become an international focus of broad geoscientific investigation following the discovery of economic diamondiferous ...
Canadian Journal of Earth Sciences, 2005
Page 1. 495 Electrical-resistivity imaging of the central Trans-Hudson orogen1, 2 Ian J. Ferguson... more Page 1. 495 Electrical-resistivity imaging of the central Trans-Hudson orogen1, 2 Ian J. Ferguson, Kevin M. Stevens, and Alan G. Jones Abstract: Magnetotelluric (MT) measurements were made on a profile across the Trans-Hudson ...
Canadian Journal of Earth Sciences, 2005
Page 1. Electromagnetic images of the Trans-Hudson orogen: the North American Central Plains anom... more Page 1. Electromagnetic images of the Trans-Hudson orogen: the North American Central Plains anomaly revealed1, 2 Alan G. Jones, Juanjo Ledo, and Ian J. Ferguson Abstract: Magnetotelluric studies of the Trans-Hudson ...
Canadian Journal of Earth Sciences, 2005
Abstract: Magnetotelluric (MT) measurements to image the three-dimensional resistivity structure ... more Abstract: Magnetotelluric (MT) measurements to image the three-dimensional resistivity structure of the North American continent from an Archean core to a region of Tertiary assembly were recorded at almost 300 sites along 3200 km of profiles on the Lithoprobe Slave Northern ...
Earth and Planetary Science Letters, 2002
The Great Slave Lake shear zone (GSLsz) is a northeast-trending 25-km-wide dextral continental tr... more The Great Slave Lake shear zone (GSLsz) is a northeast-trending 25-km-wide dextral continental transform fault from the foothills of the Rocky Mountains in northeast British Columbia to the southeast side of Great Slave Lake. Based on its magnetic expression the GSLsz can be correlated for at least 1300 km, mostly in the subsurface. Magnetotelluric (MT) soundings were made at 60 sites in the southwest part of the Northwest Territories, Canada, along the LITHOPROBE Slave^Northern Cordillera Lithospheric Evolution (SNORCLE) Transect Corridors 1 and 1A, in the Summer and Autumn of 1996. Of these, 15 sites were along Corridor 1A which crossed the GSLsz, the Great Bear magmatic arc and Hay River terrane to the northwest of the shear zone, and the Buffalo Head terrane to the southeast. The primary objective of the Corridor 1A deployments was to image the structure of the GSLsz. Analysis of MT data indicates that along the Corridor 1A the resistivity structure is approximately 1D at shallow depth ( 6 1 km) corresponding to Phanerozoic sedimentary rocks, 2D in the upper to mid crust with a strike VN30³E, and approximately 2D in the lower crust to lithospheric mantle with a strike of VN60³E. The direction in the upper crust is interpreted to represent the local-scale ( 6 50 km) horizontal strike of the GSLsz whereas the direction in the mantle is parallel to the larger-scale strike of the GSLsz. 2D inversions of the MT data reveal that the GSLsz forms a crustal-scale resistive zone ( s 5000 6m) that is spatially correlated with a magnetic low. The GSLsz comprises greenschist to granulite facies mylonites. Its high resistivity is interpreted to be due to the resistive nature of the granitic protolith of the mylonites and that mylonites are dominated by rocks deformed in the ductile regime. To the northwest of GSLsz the MT profile reveals crustal conductors beneath the Great Bear magmatic arc and Hay River terrane. The enhanced conductivity occurring beneath the Great Bear magmatic arc is interpreted to be caused by electronic conduction within deformed and metamorphosed rocks of the Hottah terrane or the Coronation Supergroup. The MT results also reveal a mantle conductor beneath the margin of the Hottah terrane and Great Bear magmatic arc that is interpreted to be associated with the subduction of oceanic lithosphere. A second mantle conductor to the southeast is truncated at the GSLsz suggesting an older source for the enhanced conductivity and that the GSLsz includes significant strike^slip motion of sub-crustal lithosphere. ß
Canadian Journal of Earth Sciences, 2005
Page 1. Electromagnetic images of the Trans-Hudson orogen: the North American Central Plains anom... more Page 1. Electromagnetic images of the Trans-Hudson orogen: the North American Central Plains anomaly revealed1, 2 Alan G. Jones, Juanjo Ledo, and Ian J. Ferguson Abstract: Magnetotelluric studies of the Trans-Hudson ...
Canadian Journal of Earth Sciences, 2005
Abstract: Magnetotelluric (MT) measurements to image the three-dimensional resistivity structure ... more Abstract: Magnetotelluric (MT) measurements to image the three-dimensional resistivity structure of the North American continent from an Archean core to a region of Tertiary assembly were recorded at almost 300 sites along 3200 km of profiles on the Lithoprobe Slave Northern ...
Geology, 1993
Magnetotelluric data acquired across the Paleoproterozoic Trans-Hudson orogen, northern Saskatche... more Magnetotelluric data acquired across the Paleoproterozoic Trans-Hudson orogen, northern Saskatchewan, image one of the world's longest crustal features, the North American Central Plains conductivity anomaly. Modeling shows the anomaly at this latitude to comprise two distinct, westward-dipping bodies of high conductivity lying structurally above a late collisional feature, the Guncoat thrust. The shallower of these bodies correlates with the western part of the La Ronge belt; the deeper body at mid-crustal depths underlies the Wathaman batholith, and its western boundary is close to the inferred subsurface extension of the subvertical Needle Falls shear zone. The anomaly is identified with interleaved, biotitic, metasedimentary rocks of the Nemeiben zone and Cree Lake belt and is interpreted to have been thrust beneath the margin during collision of the La Ronge arc with the Rae-Hearne continent via westward-directed subduction.
Physics of the Earth and Planetary Interiors, 2005
... Apparent resistivity responses indicate the ca 3.0 Ga North Caribou terrane contains extremel... more ... Apparent resistivity responses indicate the ca 3.0 Ga North Caribou terrane contains extremely resistive crust. ... The results suggest that the supracrustal component of the North Caribou terrane provides minimal enhancement of the crustal conductivity. ...
Lithos, 2003
The Slave craton in northwestern Canada, a relatively small Archean craton (600 Â 400 km), is ide... more The Slave craton in northwestern Canada, a relatively small Archean craton (600 Â 400 km), is ideal as a natural laboratory for investigating the formation and evolution of Mesoarchean and Neoarchean sub-continental lithospheric mantle (SCLM). Excellent outcrop and the discovery of economic diamondiferous kimberlite pipes in the centre of the craton during the early 1990s have led to an unparalleled amount of geoscientific information becoming available.
Journal of Geophysical Research, 2004
1] Two goals of Lithoprobe's geoscientific studies in the Phanerozoic accretionary cordillera of ... more 1] Two goals of Lithoprobe's geoscientific studies in the Phanerozoic accretionary cordillera of western North America were to define the subsurface geometries of the terranes and to infer the physical conditions of the crust. These questions were addressed in Canada's southern cordillera a decade ago and have more recently been addressed in the northern cordillera, of which one component of the new studies is magnetotelluric (MT) profiling from ancestral North American rocks to the coast. We present a resistivity cross section, and its interpretation, of the northern cordillera derived from modeling data from 42 MT sites along a 470-km-long NE-SW profile. Beneath the Coast Belt (southwestern end of the profile) a deep crustal low-resistivity layer dips inland; we interpret the crustal part of this conductor as being due to metasedimentary rocks emplaced and metamorphosed during Paleocene Kula plate subduction. A strong lateral transition in lithospheric mantle resistivity exists below the Intermontane Belt that is spatially coincident with changes in chemical and isotopic characteristics of Tertiary to recent alkaline lavas, suggesting that isotopically enriched lithosphere related to the Coast Belt basalts extends partly beneath the Intermontane Belt. The unusually high lower crustal resistivity in the Intermontane and Omineca Belts, similar in value to the resistivity found in the unextended part of central British Columbia, excludes the presence of fluids or conducting metasediments. Finally, our resistivity model displays strong lateral variation of the middle and lower crust between different terranes within the same belt, as a result of the complex structural evolution of the lithosphere.
Geophysical Research Letters, 2002
1] Wideband magnetotelluric (MT) data were acquired along three profiles crossing the strike-slip... more 1] Wideband magnetotelluric (MT) data were acquired along three profiles crossing the strike-slip Tintina Fault in northwestern Canada. The MT responses obtained exhibit remarkable similarity from all three profiles, implying similar two-dimensional (2-D) electromagnetic behavior of the fault zone over a strike length of at least 350 km. Analyses of the MT responses for dimensionality corroborate the validity of assuming regional 2-D structures in interpretation. Several high conductivity anomalies at different depth scales are present in the models obtained, and we suggest that both the shallow structures and the deep crustal scale anomalies are caused by electronic conduction mechanisms in interconnected mineralized zones. Intriguingly, the middle and lower crust beneath the surface expression of the Tintina Fault is highly resistive, in contrast to some other large-scale strike-slip faults. This implies that fault zone processes that result in interconnected conducting phases are not generic in nature but are controlled by local conditions.
Geology, 2001
The Archean Slave craton in northwestern Canada is an ideal natural laboratory for investigating ... more The Archean Slave craton in northwestern Canada is an ideal natural laboratory for investigating lithosphere formation and evolution, and has become an international focus of broad geoscientific investigation following the discovery of economic diamondiferous ...
Canadian Journal of Earth Sciences, 2005
Page 1. 495 Electrical-resistivity imaging of the central Trans-Hudson orogen1, 2 Ian J. Ferguson... more Page 1. 495 Electrical-resistivity imaging of the central Trans-Hudson orogen1, 2 Ian J. Ferguson, Kevin M. Stevens, and Alan G. Jones Abstract: Magnetotelluric (MT) measurements were made on a profile across the Trans-Hudson ...
Canadian Journal of Earth Sciences, 2005
Page 1. Electromagnetic images of the Trans-Hudson orogen: the North American Central Plains anom... more Page 1. Electromagnetic images of the Trans-Hudson orogen: the North American Central Plains anomaly revealed1, 2 Alan G. Jones, Juanjo Ledo, and Ian J. Ferguson Abstract: Magnetotelluric studies of the Trans-Hudson ...
Canadian Journal of Earth Sciences, 2005
Abstract: Magnetotelluric (MT) measurements to image the three-dimensional resistivity structure ... more Abstract: Magnetotelluric (MT) measurements to image the three-dimensional resistivity structure of the North American continent from an Archean core to a region of Tertiary assembly were recorded at almost 300 sites along 3200 km of profiles on the Lithoprobe Slave Northern ...
Earth and Planetary Science Letters, 2002
The Great Slave Lake shear zone (GSLsz) is a northeast-trending 25-km-wide dextral continental tr... more The Great Slave Lake shear zone (GSLsz) is a northeast-trending 25-km-wide dextral continental transform fault from the foothills of the Rocky Mountains in northeast British Columbia to the southeast side of Great Slave Lake. Based on its magnetic expression the GSLsz can be correlated for at least 1300 km, mostly in the subsurface. Magnetotelluric (MT) soundings were made at 60 sites in the southwest part of the Northwest Territories, Canada, along the LITHOPROBE Slave^Northern Cordillera Lithospheric Evolution (SNORCLE) Transect Corridors 1 and 1A, in the Summer and Autumn of 1996. Of these, 15 sites were along Corridor 1A which crossed the GSLsz, the Great Bear magmatic arc and Hay River terrane to the northwest of the shear zone, and the Buffalo Head terrane to the southeast. The primary objective of the Corridor 1A deployments was to image the structure of the GSLsz. Analysis of MT data indicates that along the Corridor 1A the resistivity structure is approximately 1D at shallow depth ( 6 1 km) corresponding to Phanerozoic sedimentary rocks, 2D in the upper to mid crust with a strike VN30³E, and approximately 2D in the lower crust to lithospheric mantle with a strike of VN60³E. The direction in the upper crust is interpreted to represent the local-scale ( 6 50 km) horizontal strike of the GSLsz whereas the direction in the mantle is parallel to the larger-scale strike of the GSLsz. 2D inversions of the MT data reveal that the GSLsz forms a crustal-scale resistive zone ( s 5000 6m) that is spatially correlated with a magnetic low. The GSLsz comprises greenschist to granulite facies mylonites. Its high resistivity is interpreted to be due to the resistive nature of the granitic protolith of the mylonites and that mylonites are dominated by rocks deformed in the ductile regime. To the northwest of GSLsz the MT profile reveals crustal conductors beneath the Great Bear magmatic arc and Hay River terrane. The enhanced conductivity occurring beneath the Great Bear magmatic arc is interpreted to be caused by electronic conduction within deformed and metamorphosed rocks of the Hottah terrane or the Coronation Supergroup. The MT results also reveal a mantle conductor beneath the margin of the Hottah terrane and Great Bear magmatic arc that is interpreted to be associated with the subduction of oceanic lithosphere. A second mantle conductor to the southeast is truncated at the GSLsz suggesting an older source for the enhanced conductivity and that the GSLsz includes significant strike^slip motion of sub-crustal lithosphere. ß