Paleomagnetism of some Grenville Province Rocks

Abstract

Anorthositic rocks 20 to 30 km south of the Grenville Front in the Grenville Province of Ontario have a stable remanent magnetization which yields a paleomagnetic pole at 161 °E, 8 °N. This pole is close to other poles from the Precambrian of North America of 1050 m.y. age. Paleomagnetic results have also been obtained from two rock units in the southern part of the Grenville Province of Ontario. These are a pyroxenite exposed near Wilberforce and the Tudor Gabbro exposed near Madoc. The directions of remanent magnetization yield pole positions as follows: Wilberforce pyroxenite—148 °E, 14.5 °S; Tudor Gabbro—137 °E, 17 °N. These pole positions, together with others from the literature, which have been derived from rock units 200 km or more south of the Grenville Front, plot farther west in the Pacific than do poles of inferred similar age from other regions of North America. A possible interpretation of these results is that the southern part of the Grenville province was formed some 30° SE of its present position.

Amphibole and plagioclase chemistry in two Proterozoic dyke swarms and its relation to the uplift history of the Kapuskasing Structural Zone

“…Where these have been studied in anorthosites (Murthy et al 1971;Palmer and Carmichael 1973) the particles are acicular and up to 30 pm in length, considerably larger than those in the dyke rocks of the present study. If the segregation of these opaque particles is the result of exsolution (Philpotts 1981), the slower cooling of the massif-type anorthosites probably accounts for their larger size.…”

A paleomagnetic and U–Pb geochronology study of the western end of the Grenville dyke swarm: Rapid changes in paleomagnetic field direction at ca. 585Ma related to polarity reversals?

“…Within the Grenville Front Tectonic Zone (GFTZ), a well-defined C-like direction characterizes the 2.47 Ga River Valley anorthosite (Palmer and Carmichael, 1973) which has been subject to a ∼1 Ga metamorphic event associated with the Grenville orogen (biotite and hornblende Ar 40 -Ar 39 data; Halls and Lovette, unpublished data). Samples collected from several additional sites within the anorthosite as well as meta-diabases from Sudbury and 2.2 Ga Nipissing intrusions in the same region all give this direction (Palmer et al, 1977, Halls and Lovette, unpublished paleomagnetic data) which presumably post-dates the age of Sudbury dykes (1.23 Ga) and pre-dates Grenville dyke emplacement.…”

Paleomagnetism of the Katherine Group in the Mackenzie Mountains: implications for post-Grenville (Hadrynian) apparent polar wander

“…(Park and Emslie 1983); 2, 3, Thanet gabbro A, and A, components (Buchan 1978); 4, Grenville diorites, Quebec (322) ; 5, Mealy Mountains dykes, B component (Park and Emslie 1983); 6, Morin anorthosite complex (482) (Irving et al 1974~); 7, Allard Lake anorthosite (Hargraves and Burt 1967); 8, Haliburton intrusions, Hb, (Buchan and Dunlop 1976); 9, Whitestone diorite, WZ (503) (Ueno et al 1975); 10, Lac St-Jean anorthosite, normal (Buchan et al 1983); 1 1, Magnetawan metasediments (McWilliams and Dunlop 1978); 12, Wilberforce pyroxenite (457) (Palmer and Carmichael 1973); 13, Whitestone anorthosite, WW (500) (Ueno et al 1975); 14, St-Urbain anorthosite (409) (P. B. (Park and Emslie 1983); 2, 3, Thanet gabbro A, and A, components (Buchan 1978); 4, Grenville diorites, Quebec (322) ; 5, Mealy Mountains dykes, B component (Park and Emslie 1983); 6, Morin anorthosite complex (482) (Irving et al 1974~); 7, Allard Lake anorthosite (Hargraves and Burt 1967); 8, Haliburton intrusions, Hb, (Buchan and Dunlop 1976); 9, Whitestone diorite, WZ (503) (Ueno et al 1975); 10, Lac St-Jean anorthosite, normal (Buchan et al 1983); 1 1, Magnetawan metasediments (McWilliams and Dunlop 1978); 12, Wilberforce pyroxenite (457) (Palmer and Carmichael 1973); 13, Whitestone anorthosite, WW (500) (Ueno et al 1975); 14, St-Urbain anorthosite (409) (P. B.…”