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The Sept Iles Intrusion

The Sept Iles Intrusion

The Sept Iles Intrusion, Quebec, Canada

 

The Sept Iles layered intrusion (564 Ma) is located along the St Lawrence rift system and is thought to have been fed by a mantle plume related to the opening of the Iapetus Ocean. With a diameter of 80 km and an estimated volume of 20,000 km3, Sept Iles is considered to be the third largest layered intrusion on Earth. The intrusion is subdivided into three series: (1) the troctolite-gabbro Layered Series (Fig. 1a); (2) the anorthositic Upper Border Series (Fig. 1b) and (3) the mostly granitic Upper Series (Fig. 1c). The intrusion results from the crystallization of several pulses of ferrobasaltic magma. The granitic Upper Series has been shown to represent the most evolved residual liquids of the ferrobasaltic differentiation, while the Upper Border Series was formed by plagioclase flotation to the top of the magma chamber.

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