Abstract

The South Lake Igneous Complex, located south of Notre Dame Bay in the Exploits Zone of central Newfoundland, consists of ophiolitic (layered gabbro and sheeted dike) fragments intruded by a quartz–hornblende diorite and a later tonalite. All units are cut by swarms of basalt dikes. The sheeted dikes of the ophiolitic fragments are depleted in incompatible elements relative to mid-ocean ridge basalts, but to a lesser degree than the depleted lavas of the Bett's Cove Ophiolite in the Notre Dame Bay Zone to the west, and are interpreted as being components of oceanic crust formed in a back-arc basin. The intruding plutonic phases are rich in hydrous minerals and are severely depleted in incompatible elements, and are considered to be related to the formation of an island-arc volcanic pile upon the ophiolitic basement, with the rising magmas massively intruding and disrupting the basement rocks. The late dikes are enriched in incompatible elements and have a transitional tholeiitic–alkalic character. How much younger these dikes are than the rocks they intrude is unknown. Assuming that they are similar in age, an origin of these basalts from a subducted oceanic ridge is speculated.

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