A paleomagnetic study of the layered mafic intrusion at Sept-Îles, Quebec

Abstract

A paleomagnetic study of gabbroic and anorthositic members of the Sept-Îles layered mafic intrusion has isolated a remanence with direction D = 333°, I = −29 °(remanence A) and a corresponding pole of 141 °E, 20°N. The rocks are cut by numerous diabase dykes of unknown age. The remanence carried by the dykes has direction D = 188°, I = −85 °(remanence B), with a corresponding pole of 116°E, 59°S. Another remanence, statistically identical to B (D = 186°, I = −85°), is found at dyke contacts and in the local host rock; its associated pole, 115°E, 61°S, is identical to the one derived from the dykes. This overprint is significantly different from remanence A, and is obviously related to dyke emplacement. The location of the pole derived from remanence A is in excellent agreement with many other Cambrian poles from a variety of locations throughout cratonic North America. The rocks at Sept-Îles have been previously dated radiometrically at 540 Ma. Thus, all evidence indicates that remanence A is an original thermochemical remanent magnetization, acquired during initial cooling of the intrusion in the Cambrian and prior to the emplacement of the dykes.

A palaeomagnetic and palaeobiogeographical perspective on latest Neoproterozoic and early Cambrian tectonic events

“…Our preferred high-latitude Laurentia option (Fig. 1a and b) has palaeomagnetic support from two studies in North America (Symons & Chiasson 1991;Meert et al 1994) and weaker support from a study of the Sept Îles Igneous Complex (Tanczyk et al 1987). The model does require a relatively rapid transition (minimally c. 11 cm a À1 ) from a high-latitude Laurentia at c. 565 Ma to a more equatorial position by MidCambrian time (c. 508 Ma, Tapeats sandstone).…”

A Paleogeographic Model for Vendian and Cambrian Time

“…This implies that North America was in mC'derate southerly latitudes, with the Cordilleran margin to the north. A newly reported paleomagnetic pole, from intrusives dated at 540 ± 22 Ma (Rb,tSr) from the Sept-lies layered mafic intrusion in Quebec, Canada (Tanczyk et al 1987), also falls in this vicinity (although the age of the magnetizations in this unit are not constrained biostratigraphically).…”

Neoproterozoic?Early Paleozoic evolution of peri-Gondwanan terranes: implications for Laurentia-Gondwana connections

“…Two reliable paleomagnetic poles from Laurentia exist for this time interval. One is from the 577 Ma Callander Complex (Symons and Chaisson 1991), the other from the Sept les intrusion (Tanczyk et al 1987), dated at 565 Ma (Higgins and van Breeman (1998). Since it is impossible to incorporate both poles into the same tectonic model, two models are presented here.…”