Paleoproterozoic tectonic processes revealed through electromagnetic studies of the North American Central Plains (NACP) conductivity anomaly: From continental to hand sample scale

1996 ◽  
Author(s):  
Alan G. Jones ◽  
Jon Katsube ◽  
Ian Ferguson
Keyword(s):  
North American ◽  
Conductivity Anomaly ◽  
Central Plains ◽  
The North ◽  
Tectonic Processes ◽  
Hand Sample

Electromagnetic images of the Trans-Hudson orogen: the North American Central Plains anomaly revealed

2005 ◽  
Vol 42 (4) ◽  
pp. 457-478 ◽  
Author(s):  
Alan G Jones ◽  
Juanjo Ledo ◽  
Ian J Ferguson
Keyword(s):  
Electrical Properties ◽  
North American ◽  
Upper Mantle ◽  
Lithospheric Mantle ◽  
Three Dimensional ◽  
Conductivity Anomaly ◽  
Central Plains ◽  
Slave Craton ◽  
The North ◽  
Kimberlite Field

Magnetotelluric studies of the Trans-Hudson orogen over the last two decades, prompted by the discovery of a significant conductivity anomaly beneath the North American Central Plains (NACP), from over 300 sites yield an extensive database for interrogation and enable three-dimensional information to be obtained about the geometry of the orogen from southern North Dakota to northern Saskatchewan. The NACP anomaly is remarkable in its continuity along strike, testimony to along-strike similarity of orogenic processes. Where bedrock is exposed, the anomaly can be associated with sulphides that were metamorphosed during subduction and compression and penetratively emplaced deep within the crust of the internides of the orogen to the boundary of the Hearne margin. A new result from this compilation is the discovery of an anomaly within the upper mantle beginning at depths of ~80–100 km. This lithospheric mantle conductor has electrical properties similar to those for the central Slave craton mantle conductor, which lies directly beneath the major diamond-producing Lac de Gras kimberlite field. While the Saskatchewan mantle conductor does not directly underlie the Fort à la Corne kimberlite, which is associated with the Sask craton, the spatial correspondence is close.

scholarly journals The North American Central Plains Conductivity Anomaly

1975 ◽  
Vol 43 (3) ◽  
pp. 815-833 ◽  
Author(s):  
A. O. Alabi ◽  
P. A. Camfield ◽  
D. I. Gough
Keyword(s):  
North American ◽  
Conductivity Anomaly ◽  
Central Plains ◽  
The North

scholarly journals Occam's Inversion and the North American Central Plains Electrical Anomaly.

1993 ◽  
Vol 45 (9) ◽  
pp. 985-999 ◽  
Author(s):  
Catherine Degroot-Hedlin ◽  
Steven Constable
Keyword(s):  
North American ◽  
Central Plains ◽  
The North ◽  
Occam’S Inversion

Crustal electrical conductivity in north-central Saskatchewan: the North American Central Plains anomaly and its relation to a Proterozoic plate margin

1984 ◽  
Vol 21 (5) ◽  
pp. 533-543 ◽  
Author(s):  
S. Handa ◽  
P. A. Camfield
Keyword(s):  
Electrical Conductivity ◽  
Subduction Zone ◽  
North American ◽  
Central Plains ◽  
Period Range ◽  
Geological Evidence ◽  
North Central ◽  
The North ◽  
Plate Margin ◽  
Lake Zone

Seven recording magnetometers monitored time-varying fields at points on a northwest–southeast line 280 km long in north-central Saskatchewan during July 1981. The experiment was designed to test the hypothesis advanced in 1975 by Alabi, Camfield, and Gough that the electrical conductivity anomaly in the North American Central Plains links with the Wollaston Domain in the exposed Precambrian Shield of Saskatchewan. From clear reversals in the phase of vertical variations, it is evident that the conductor passes between two stations straddling the Rottenstone–La Ronge Magmatic Belt, to the immediate east of the Wollaston Domain. Enhanced horizontal variations transverse to the belt at a third, intermediate, station reinforce this interpretation. Vertical-field response arrows obtained from daytime events in the period range 1–40 min clearly indicate the existence of a major conductor that extends to lower crustal depths beneath the belt. To the northwest across the Cree Lake Zone, reversals in the direction of response arrows at short periods (up to 4 min) imply complex electrical structures in the shallow part of the crust.Lewry termed the Rottenstone–La Ronge Belt a Hudsonian "Cordillera-type" arc massif, and described strong geological evidence for collisional suturing and microplate interaction in this part of the Churchill Province. A similar scenario seems to apply in Wyoming, from the work of Hills and Houston. Thus the conductor appears to trace a Proterozoic plate margin 1500 km from a subduction zone in Wyoming along a transform fault to a subduction zone in northern Saskatchewan.

A magnetotelluric investigation under the Williston Basin of southeastern Saskatchewan

1988 ◽  
Vol 25 (1) ◽  
pp. 60-67 ◽  
Author(s):  
J. M. Maidens ◽  
K. V. Paulson
Keyword(s):  
Low Frequency ◽  
Singular Value ◽  
Williston Basin ◽  
Frequency Range ◽  
Conductivity Anomaly ◽  
Central Plains ◽  
The North ◽  
Naturally Occurring ◽  
Value Decomposition ◽  
Resistivity Log

A magnetotelluric (MT) survey using naturally occurring ultra low frequency (ULF) and extremely low frequency (ELF) sources was conducted in the frequency range of 0.5 mHz to 20 Hz in order to locate the western edge and the depth of the North American Central Plains (NACP) conductivity anomaly in the Bengough area of southeastern Saskatchewan. The data base was also used to evaluate the complex singular-value decomposition (CSVD) method of MT processing and to corroborate certain geologic interpretations in this part of the Williston Basin.Modelling of the resulting impedance tensors revealed a deep (10–15 km) zone with resistivity (35–85 Ω∙m) significantly lower than typical values (1000–1500 Ω∙m) obtained from a borehole resistivity log of the top 30 m of the Precambrian at a depth of 2.3 km. An increase in depth (to 20 km) and resistivity (150–275 Ω∙m) of this deep zone measured at the survey's west end was interpreted as indicating the anomaly's western edge. The CSVD processing of the data did not show any particular advantages over the conventional cross-spectral method.

North American Central Plains conductivity anomaly within the Trans-Hudson orogen in northern Saskatchewan, Canada

Geology ◽  
1993 ◽  
Vol 21 (11) ◽  
pp. 1027 ◽  
Author(s):  
Alan G. Jones ◽  
James A. Craven ◽  
Gary W. McNeice ◽  
Ian J. Ferguson ◽  
Trevor Boyce ◽  
...  
Keyword(s):  
North American ◽  
Conductivity Anomaly ◽  
Central Plains ◽  
Northern Saskatchewan

scholarly journals NEW OR LITTLE KNOWN GENERA OF NORTH AMERICAN SYRPHIDÆ

1882 ◽  
Vol 14 (4) ◽  
pp. 77-80 ◽  
Author(s):  
S. W. Williston
Keyword(s):  
New Species ◽  
North America ◽  
North American ◽  
Careful Study ◽  
Central Plains ◽  
The North

In the preparation of a synopsis of the North American genera of Syrphidæ, I have found several new species that could not be placed in any of our known genera. A careful study of the figures and descriptions of exotic forms has not thrown much light upon them, and I am therefore constrained to regard them as new.With the genera included in the present paper, and resuscitating Macquart's Toxomerus, the number now recorded from North America will reach sixty, all but five or six of which are in the writer's collection. Of these, but nine or ten have not yet been found east of the Central Plains, and the following, only, that are not now known west of that region, viz., Triglyphus, Senogaster, Pyrophaena, Doros, Ocyptamus, Rhingia, Brachyalpus, Somula, Temnostoma, Merapioidus, Pterallastis, Teuchocnemis and Lepidomyia, leaving nearly forty genera that occur entirely across the continent; indeed a large proportion of the species are identical from the Atlantic and Pacific regions.

Sign in / Sign up

Export Citation Format

Share Document