Paleomagnetism and structural history of the Ghost Range intrusive complex, central Abitibi Belt, Ontario: further evidence for the Late Archean geomagnetic field of North America

• Published in: Canadian Journal of Earth Sciences
• Main Authors: Geissman, John Wm., Strangway, David W., Tasillo-Hirt, Ann M., Jensen, Larry S.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1982
• Subjects: General Earth and Planetary Sciences; Geomagnetic Pole
• Online Access: http://dx.doi.org/10.1139/e82-184; http://www.nrcresearchpress.com/doi/pdf/10.1139/e82-184

On the basis of their remanence properties, the lithologies of the Late Archean (2710–2703 Ma) Ghost Range Complex, an east–west-trending layered mafic–ultramafic extrusive sequence in the central Abitibi Greenstone Belt, can be divided into three groups. Group 1 units contain a high-coercivity, high-blocking temperature (greater than 520 °C) magnetite-dominated remanence characteristic of the complex (D = 280°, I = 2°, k = 5.5, α 95 = 11.8°, virtual geomagnetic pole = 13°E, 7°S; isolated by both AF and thermal methods), in good agreement with the few previous results bearing on the Late Archean apparent polar wander path for North America. Group 2 units contain a low-coercivity, low-blocking-temperature (less than 310°C) scattered remanence residing in pyrrhotite. Often, both remanences coexist in a single lithology at a given site. Group 3 units contain distributed coercivity and blocking-temperature remanences, again residing in magnetite, that are more scattered but statistically identical to the mean group 1 direction. The order of magnetic blocking appears to have been group 1 before group 3 before group 2. The geologic setting of the Ghost Range suggests that it has remained essentially stable since emplacement and therefore the group 1 direction appears to reliably represent a Late Archean paleomagnetic pole.