Keywords:

Abstract:

The influence of mantle plumes on tectonics is hotly debated with implications for styles of volcanism, heat flow, and cratonization processes in the Archean. Mafic- ultramafic rocks in the Wabigoon subprovince (WS), the North Caribou terrane (NCT), and the Abitibi Greenstone Belt (AGB) in the Superior Province exhibit variations in geochemistry that aid in the elucidation of models for Archean tectonics. The NCT and WS contain sedimentary-komatiite-tholeiite sequences overlying basement in greenstone belts that have been dated at 2.96-2.90 Ga (WS) and 2.93 Ga (NCT). The komatiite sequences in the AGB formed within the narrow interval 2.720-2.701 Ga. Variations in komatiite geochemistry in the WS and NCT may be explained by geochemical variations across a plume head, including material from the plume axis (ADK), middle plume head (AUK), and outermost plume head (basalts). Variations in komatiite geochemistry in the AGB may be also be explained by variations across a plume, including the plume axis (ADK, Ti-depleted komatiites, and Al-enriched komatiites) and middle plume head (AUK and Ti-enriched komatiites). However, wide geochemical variations occur within individual temporally distinct assemblages, within individual flow sequences, and rarely, within individual intercalated flows, which are difficult to reconcile with a simple plume model. This may imply subtle variations in the composition of the source region or the influence of subsequent petrogenetic processes (degree of partial melting, AFC, mixing, and metamorphism/alteration).

Notes:

GeoRef, Copyright 2018, American Geological Institute.<br/>2002-057799<br/>North Caribou Terrane