The paleomagnetism of the Great Slave Supergroup: the Akaitcho River Formation

Abstract

Results are reported from 120 oriented samples collected from 40 stratigraphic horizons spanning the Akaitcho River Formation of the Great Slave Supergroup. Thermal demagnetization experiments reveal the presence of multiphase remanence. Difference vectors indicate that the lower blocking temperatures carry a magnetic component attributable to the present field. The remanence remaining above 500–600 °C defines two polarity groups, but the two groups are not exactly antiparallel. This is interpreted in terms of a previously recognised widespread magnetic overprint acquired during uplift and cooling in the Coronation Geosyncline. A compilation of appropriate overprint data from the Great Slave Supergroup yields a mean direction of D = 152°, I = +64 °(N = 75 sites, k = 30, α95 = 3°), with a corresponding pole at 91°W, 21°N (K = 14, A95 = 5°). A statistical procedure is employed to remove this overprint and obtain a best estimate of the original magnetization, which corresponds to a paleomagnetic pole on the western limb of the Coronation loop (92°W, 4°S, N = 35 sites, K = 13, A95 = 7°).

Paleomagnetism of the Great Slave Supergroup, Northwest Territories, Canada: multicomponent magnetization of the Kahochella Group

“…It is widespread in the Athapuscow Aulacogen and corresponds to a paleomagnetic pole at 91°W, 21°N (N = 75 sites, K = 14, Ag5 = 5", see Evans et al 1980). Its probable correlatives have been recorded from other parts of the Canadian Shield, and even as far east as Greenland (see McGlynn and Irving 1978;Irving and McGlynn 1979).…”

“…As pointed out above, the group 1 overprint has been recognised and reported by a number of workers ;Evans et al (1980) refer to it as the Coronation overprint. It is widespread in the Athapuscow Aulacogen and corresponds to a paleomagnetic pole at 91°W, 21°N (N = 75 sites, K = 14, Ag5 = 5", see Evans et al 1980).…”

“…(Evans and Bingharn 1973); K2 = Kahochella group 2 (herein); ET = Etthen Group (Irving et al 1972); CO = Coronation overprint (Evans et al 1980). The Coronation overprint pole represents a summary of data from several sources, but is dominated by the Kahochella group 1 result reported in this paper.…”

Paleomagnetism and the evolution of fluids in the Proterozoic Athabasca Basin, northern Saskatchewan, Canada

“…Like the A paleopole, all have normal polarity. Some are based on secondary post-folding magnetizations, such as those in sedimentary rocks from the Great Slave Supergroup (CO; Evans et al 1980) and in the Eskimo volcanics of the Belcher Islands (EVO; Schmidt 1980). Others have been obtained from metamorphic rocks whose magnetizations have been acquired as a result of uplift and cooling following deformation, such as those in the metamorphic rocks of the Melville Peninsula and Daly Bay (MD; Park 1973) and the Itivdelq dykes and gneisses of Greenland (IT; Morgan 1976).…”

“…(Beckmann 1983); CL, Cleaver dykes (see below); CO, Coronation overprint (Evans et al 1980); CS, Cape Smith basalt (Fujiwara and Schwarz 1975); EVO, Eskimo volcanics overprint (Schmidt 1980); FFO, Flin Flon overprint (Park 1975); IT, Itivdelq metamorphosed dykes and gneisses (Beckmann and Mitchell 1976;Morgan 1976); KD, Kangamuit metamorphosed dykes (Beckmann and Mitchell 1976); KMD, Kaminak metamorphosed dykes (Christie et al 1975); LL, Lynn Lake gabbro (Dunsmore and Symons 1990); MD, Melville Peninsula -Daly Bay metamorphic rocks (Park 1973); 01, Ottawa Island komatiites (Buchan and Baragar 1985); SD, Slave dykes overprint (McGlynn and Irving 1975); (ii) older Middle Proterozoic (1480-1350 Ma): BA, Belt-Purcell Supergroup of Alberta (Evans et al 1975); BM, Belt-Purcell Supergroup of Montana (Elston and Bressler 1980); BS, Belt-Purcell Supergroup, Spokane (Vitorello and Van der Voo 1977); CR, Croker Island Complex (Palmer 1969); HL, Harp Lake Complex (Irving et al 1977); MA, Michickamau anorthosite (Emslie et al 1976); MI, Mistastin pluton (Murthy et al 1968;Emslie et al 1976); NC, Nain Complex (Murthy 1978); SB, Sibley Group (Robertson 1973); SF, St. Francois igneous rocks (Hayes and Scharon 1966); SL, Seal Lake red beds (Roy and Fahrig 1973); WCD, Western Channel diabase dykes (Irving et al 1972); WCP, the dyke through Port Radium part of WCD (see below); and (iii) Late Proterozoic overprints in Jacobsville Sandstone (52) (Roy and Robertson 1978) and Chequamegon sandstone (CH) (McCabe and Van der Voo 1983). The Port Radium dyke (WCP) is situated at 66.3ON, 117.7"W; mean direction (D, I) is 359", -32", n = 8, k = 117, a,, = 5" obtained from 8 sites and paleopole 6"S, 1 17 "W (calculated from data in Irving et al 1972).…”