A gap in the North American Central Plains conductivity anomaly

Rankin, David; Pascal, F.

doi:10.1016/0031-9201(90)90255-v

Cited by 8 publications

(5 citation statements)

References 11 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…MT measurements (not shown) were made just north of the PanCanadian profile by Maidens and Paulson (1988; see a discussion of their work in Jones 1988b) and by Rankin and Pascal (1990). The former interpreted static shift effects (Jones 1988a) in terms of structure, whereas the latter, notwithstanding their imaging of the NACP anomaly, concluded, somewhat perplexingly, that there was a gap in the NACP structure so that it did not cross their profile.…”

Section: Magnetotelluric Data Acquired Across the Trans-hudson Orogenmentioning

confidence: 97%

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

Jones¹,

Ledo²,

Ferguson³

2005

Can. J. Earth Sci.

View full text Add to dashboard Cite

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 ~80100 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.

show abstract

Section: Magnetotelluric Data Acquired Across the Trans-hudson Orogenmentioning

confidence: 97%

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

Jones¹,

Ledo²,

Ferguson³

2005

Can. J. Earth Sci.

View full text Add to dashboard Cite

show abstract

“…Branching off the FFW belt, the Cedar Creek fault HCB follows the west edge of a positive gravity anomaly and a magnetic quiet zone (Figures 2c and 2d). This HCB terminates abruptly at 49°N (Jones & Savage, 1986; Rankin & Pascal, 1990), coincident with a change in magnetic character. The Cedar Creek fault HCB lies downdip of west‐dipping lower‐crustal reflectors in northeast Montana (Nelson et al., 1993), marking west‐dipping subduction beneath the Wyoming craton and Medicine Hat block.…”

Section: Tectonic Frameworkmentioning

confidence: 98%

“…Termed the NACP conductor, Camfield and Gough (1977) suggested it marks a Proterozoic plate boundary, and it was quickly related to the THO once the orogen was itself recognized (Hoffman, 1988; Lewry & Collerson, 1990). Despite numerous studies, however, the geometry and source of the NACP conductor remain subject to debate (Jones & Savage, 1986; Rankin & Pascal, 1990) and it has never been fully incorporated into tectonic models of the region.…”

Section: Introductionmentioning

confidence: 99%

When Wyoming Became Superior: Oblique Convergence Along the Southern Trans‐Hudson Orogen

Bedrosian

Finn

2021

Geophysical Research Letters

View full text Add to dashboard Cite

The Trans‐Hudson orogen (THO) is one of the best‐preserved Proterozoic orogens on Earth, largely unaffected by subsequent tectonism, yet its southern extent lies concealed beneath the North American Central Plains. A new 3D resistivity model over the southern orogen is developed and interpreted alongside borehole, potential field, and seismic reflection data. We present the first synoptic crustal view of the southern THO and a new tectonic model of the orogen. Our model reveals high‐conductivity belts marking paleo‐subduction zones while the orogen center consists of deeply exhumed relatively dense and mostly magnetic juvenile crust preserved between the deformed margins of the Wyoming and Superior cratons. Complex structure along the western margin suggests convergence began with oblique subduction and the northward transport of severed fragments of the Wyoming Province. High‐conductivity belts are in places offset from upper‐crustal geophysical boundaries, consistent with the thrusting of accreted arcs over the Archean margins during terminal closure.

show abstract

“…Subsequent to these surveys, MT measurements were made just north of the PanCanadian profile by MAIDENS and PAULSON (1988;see also JONES, 1988b), andPASCAL (1990). The former interpreted static shift effects in terms of structure, whereas the latter, notwithstanding their imaging of the NACP anomaly, concluded, somewhat perplexingly , that there was a gap in the NACP structure so that it did not cross their profile.…”

Section: Previous Em Studies In the Regionmentioning

confidence: 99%

The COPROD2 Dataset: Tectonic Setting, Recorded MT Data, and Comparison of Models.

Jones

1993

J. geomagn. geoelec

View full text Add to dashboard Cite

To facilitate a comparative study of approaches and algorithms for two-dimensional interpretation of magnetotelluric (MT) data, a dataset of thirty-five sites, called COPROD2, was distributed to the electromagnetic induction community. The data are from stations along a 400 km east-west profile in southern Saskatchewan and Manitoba, Canada, crossing the thick Paleozoic sediments of the Williston basin. Within the basement beneath the sediments lies one of the world's longest and most enigmatic crustal conductivity features-the North American Central Plains (NACP) conductivity anomaly. Also, at the eastern extremity of the profile is a second basement anomaly (TOBE) interpreted to be associated with the Thompson Nickel Belt at the Superior-Churchill boundary. The MT data were corrected for static shifts, and only the ofd diagonal impedance data together with the transfer function data, and their errors, were made available. These MT data are of wide bandwidth (384 Hz-1820 s) and high quality (impedance errors typically <2%), and require sophisticated modelling and inversion in order to extract as much meaningful information as possible from them. A challenge for those interpreting these data is that there is a very small, but critical, response in the B-polarization data to the presence of the basement anomalies. In this introductory paper, the previous electromagnetic, and other geophysical, studies of the NACP anomaly, and its tectonic setting within the Trans-Hudson orogen, are described. Representative data from the COPROD2 data are illustrated, and models derived by various groups are shown. Comparisons of these models reveals that a single measure of misfit is an inadequate description of how well a model fits a dataset; one must compare the model fit to the data at virtually each datum to avoid trends in the misfit residuals. Additionally, reliable and consistent error and static shift estimates are essential in order to obtain high resolution images of the Earth's conductivity structure. Finally, the COPROD2 data highlight the sensitivity in B-polarization mode data to breaks in the resistive layer, whereas the E-polarization data sense regions of enhanced conductivity.

show abstract

A gap in the North American Central Plains conductivity anomaly

Cited by 8 publications

References 11 publications

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

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

When Wyoming Became Superior: Oblique Convergence Along the Southern Trans‐Hudson Orogen

The COPROD2 Dataset: Tectonic Setting, Recorded MT Data, and Comparison of Models.

Contact Info

Product

Resources

About