Regional mapping of Precambrian basement beneath Phanerozoic cover in southeastern Trans-Hudson Orogen, Manitoba and Saskatchewan

Leclair, A D; Lucas, Stephen Bernard; Broome, H. J.; Viljoen, D; Weber, W.

doi:10.1139/e17-049

Cited by 23 publications

(30 citation statements)

References 31 publications

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“…In contrast to gravity signals from the mantle, gravity signals from Earth's lithosphere and crust are normally of greater absolute magnitude due to the shorter distance of the generating source from observing instruments, and due to distinctive geological domains that possess particular structural or density differences (Lucas et al, 1996;Leclair et al, 1997;Ashton et al, 1999). Such signals also derive from associated lithospheric heat-fl ow domains (Mareschal et al, 1999;Rolandone et al, 2002).…”

Section: Gravitational Effects Of the Subcrustal Lithospherementioning

confidence: 99%

Gravity anomalies of the Antarctic lithosphere

Weihaupt¹,

Rice

Hoeven

2010

Lithosphere

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Anomalous free-air gravity signals in and around the Antarctic continent have been reported for some decades. Recent defi nition of the Antarctic gravity fi eld from fi eld-based oversnow traverses and supporting data from Earth-orbiting satellites reveal discrete regions of both negative and positive free-air gravity anomalies. The data from these observations have enabled us to construct a free-air gravity anomaly map of Antarctica. Negative free-air gravity anomalies are found to occur mainly on the Antarctic continent, in particular, in the Wilkes Land, Ross Sea, central continental, and Weddell Sea sectors. Positive free-air gravity anomalies are found to occur mainly in the offshore circumcontinental sectors. While each of these regions of anomalies provides excellent opportunities for further investigation, including identifi cation of the causes of the negative and positive free-air gravity anomalies, special attention is given to the negative free-air gravity anomaly sites of the continent proper. Three potential sources of the negative free-air gravity anomalies are identifi ed: the mantle, lithosphere, and crust. Examination of thermally induced density variations in the mantle based upon seismic tomography, and analysis of mantle-related gravity anomaly wavelengths favor a gravity anomaly source other than the mantle. Examination of the subcrustal lithosphere based on upper-mantle thermal structure, the origin of the lithosphere, and crustal infl uences on the underlying lithosphere, including radiogenic heat, implies that the source of the negative free-air gravity anomalies is less likely to be the subcrustal lithosphere and more likely to be located in the Antarctic crust. Examination of possible crustal features that might account for these anomalies leads to a consideration of subglacial topography and specifi c locales of anomalously low rock density.

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Section: Gravitational Effects Of the Subcrustal Lithospherementioning

confidence: 99%

Gravity anomalies of the Antarctic lithosphere

Weihaupt¹,

Rice

Hoeven

2010

Lithosphere

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“…Temperature gradients in the two holes are identical in the upper 250 m and are perturbed by the neighboring lake. The equilibrium heat flow was determined from the deep part of borehole 9506 where heat [24] These two deep boreholes are located in the southern extent of the Hanson Lake block in the Flin Flon belt [Leclair et al, 1997;Maxeiner et al, 1999] where Archean basement windows are identified [Ashton et al, 1999]. They penetrate sequences of schists interlayered with gabbros and basalts.…”

Section: Southern Margin At the Edge Of The Paleozoic Covermentioning

confidence: 99%

Surface heat flow, crustal temperatures and mantle heat flow in the Proterozoic Trans‐Hudson Orogen, Canadian Shield

et al. 2002

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The Paleo‐Proterozoic (1.8 Ga) Trans‐Hudson Orogen (THO), of intermediate age between the Superior (2.7 Ga) and Grenville (1.0 Ga) provinces, is located near the center of the Canadian Shield. We report on new measurements of heat flow and radiogenic heat production in 30 boreholes at 17 locations in this province. With these data, reliable values of heat flow and heat production are available at 45 sites in the THO. The mean and standard deviation of heat flow values are 42 ± 9 mW m−2. In this province, distinctive geological domains are associated with specific heat flow distributions. The heat flow pattern follows the surface geology with a central area of low values over an ancient back arc basin (Kisseynew) and an ancient island arc (Lynn Lake Belt) made of depleted juvenile rocks. Higher heat flow values found in peripheral belts are associated with recycled Archean crust. Within the Canadian Shield, there is no significant variation in heat flow as a function of age between provinces spanning about 2 Gyr. There is no geographic trend in heat flow across the Canadian Shield from the THO to the Labrador Sea. Low heat flow areas where the crustal structure is well‐known are used to determine an upper bound of 16 mW m−2 for the mantle heat flow. Present and paleogeotherms are calculated for a high heat flow area in the Thompson metasedimentary belt. The condition that melting temperatures were not reached in Proterozoic times yields a lower bound of 11–12 mW m−2 for the mantle heat flow.

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“…As potential-field compilations extend to greater scales, they are used increasingly to tie existing isolated interpretations or maps together through continuous data coverage (e.g., Cady 1989;Percival et al 1992), provide continentscale (plate-tectonic) perspectives on geologic structure and evolution (Thomas et al 1988;Hoffman 1989;Shaw et al 1996), and extend geological mapping of exposed (particularly Precambrian basement) regions into sediment-covered areas (Coles et al 1976;Ross et al 1991;Johnson and Stewart 1995;Adams and Keller 1996;Leclair et al 1997). A fundamental building block in these interpretations is the geophysical domain, distinguished on the basis of anomaly trend, texture, and amplitude.…”

Section: Introductionmentioning

confidence: 99%

Potential-field signatures of buried Precambrian basement in the Western Canada Sedimentary Basin

Pilkington¹,

Miles²,

Ross³

et al. 2000

Can. J. Earth Sci.

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An internally consistent, levelled compilation of magnetic data is derived for Alberta and northeastern British Columbia. With Bouguer gravity data, this compilation is used to refine the definition of Precambrian basement domains within the Western Canada Sedimentary Basin. Magnetic data are draped at a constant distance above the mapped basement surface to reduce the effects of varying magnetic source depths. Automated interpretation methods that effectively map outlines of magnetic sources are used to characterize the internal structure of the domains and to aid in their delineation. The basement domain map thus derived differs from previous interpretations in the extension of domains further to the southwest, due mainly to the availability of new public-domain magnetic data and the more precise definition of domain boundaries, based on the magnetic source location maps. The Nahanni, Hottah, Chinchaga, Thorsby, Vulcan, and Kiskatinaw domains are weakly magnetic and characterized by magnetic sources that are paramagnetic, comprising low-susceptibility silicate minerals. All other domains are characterized by the presence of ferrimagnetic material, most likely magnetite, which has a sufficiently high susceptibility to produce measurable anomalies. The largest anomalies and magnetizations are found in the Fort Nelson, Fort Simpson, Buffalo Head, Talston, Ksituan, and Matzhiwin domains. Such large magnetizations are usually indicative of intermediate igneous rocks associated with magmatic arc environments. Moderate-amplitude anomalies and (or) magnetizations are characteristic of the Nova, Wabamun, Lacombe, Rimbey, Loverna, and Medicine Hat domains, suggesting the presence of ferrimagnetic basic and granitoid rocks. Within some of the moderately magnetic domains are areas of paramagnetic lithologies that produce no magnetic anomalies. The narrower regions of magnetic lows, such as the Thorsby, Kiskatinaw, and Vulcan domains, are interpreted as resulting from demagnetization effects accompanying collision. Since demagnetization zones are limited in areal extent, the wider, more extensive magnetic lows of the Chinchaga and Hottah domains likely result from a combination of boundary demagnetization and a lower bulk magnetization level of crustal lithologies present.

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Regional mapping of Precambrian basement beneath Phanerozoic cover in southeastern Trans-Hudson Orogen, Manitoba and Saskatchewan

Cited by 23 publications

References 31 publications

Gravity anomalies of the Antarctic lithosphere

Gravity anomalies of the Antarctic lithosphere

Surface heat flow, crustal temperatures and mantle heat flow in the Proterozoic Trans‐Hudson Orogen, Canadian Shield

Potential-field signatures of buried Precambrian basement in the Western Canada Sedimentary Basin

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