Abstract

The Annieopsquotch ophiolite belt consists of ophiolite fragments exposed from Buchans in central Newfoundland to the southwest tip of the island. The largest remnants belong to the Annieopsquotch Complex in the northeast and the Long Range Mafic-Ultramafic Complex in the southwest. The Arenigian Annieopsquotch Complex exposes an ophiolite stratigraphy from layered cumulate gabbro (Moho sequence) through high-level gabbro, sheeted dikes, pillow lava, and chert. The Long Range Mafic-Ultramafic Complex consists largely of cumulate and high-level metagabbro with subordinate ultramafic rock and metabasalt, all engulfed as massif- to xenolith-size fragments in Ordovician tonalitic and younger mafic to felsic granitoid intrusions. The latter rocks are intersected by a wide, locally gently inclined, high-temperature ductile thrust zone, which also encompasses amphibolite, semipelitic schist, and marble. Between Buchans and the southwest tip of Newfoundland, the tonalite terrane encloses many smaller ophiolitic fragments. The ophiolite fragments of the northern half of the belt have similar dike trends, have N-type MORB chemistry, and likely formed one major allochthon of Iapetus oceanic crust. This was disrupted by the intrusion of tonalite and other magmas in an arc or arc-trench environment and by subsequent faulting. An attempt is made to assess the significance of the Annieopsquotch belt in relation to ether Newfoundland ophiolites.

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