The Petrology and Paleomagnetism of the Coronation Sills

Abstract

The Coronation Sills and their extrusive equivalents of the Franklin Magnetic Division form a major basaltic province of Hadrynian age in the northwestern part of the Canadian Shield. The sills are saturated or slightly undersaturated, undifferentiated tholeiites. They are similar in composition to tholeiitic plateau basaltic provinces elsewhere, particularly to the Karroo Province. Most of the paleomagnetic samples contain secondary components that are much reduced by magnetic cleaning.The optimum cleaning field determined by the precision method is 105 Oe, but by the endpoint method it is in the 200–400 Oe range. Sites may be separated by thermal cleaning into a stable group with a dominant discrete blocking temperature above 500 °C, and a less stable group with blocking temperatures distributed in the 50–550 °C range. The pole position calculated from samples cleaned in 210 Oe is 1 °S, 163 °E (α95 = 9°). The position of the revised pole for the Franklin Magnetic Interval, incorporating the Coronation Sills data, is at 5 °N., 168 °E. (α95 = 5°).