Abstract

The Flin Flon Belt is a complex (“Amisk collage”) of distinct tectono-stratigraphic assemblages that was brought together at a relatively early stage in the tectonic evolution of the Paleoproterozoic Trans-Hudson orogen. Four main tectono-stratigraphic assemblage types are recognized: isotopically juvenile oceanic arc (1.90–1.88 Ga), ocean floor (ca. 1.90 Ga), oceanic plateau/ocean island, and isotopically evolved arc (1.92–1.90 Ga). Oceanic arc assemblages include tholeiitic, calc-alkaline, and lesser shoshonitic volcanic and volcaniclastic rocks, as well as turbidites and arc-rift volcanic rocks. The tectono-stratigraphic assemblages were juxtaposed in an accretionary complex (Amisk collage) at ca. 1.88–1.87 Ga, probably as a result of arc-arc collision/collisions. Accretionary collage structures are largely obliterated by subsequent deformation and metamorphic events, but can be inferred where cut by calc-alkaline plutons related to a 1.866–1.838 Ga arc. Coeval subaerial volcanism is recorded in ca. 1.87–1.85 Ga calc-alkaline to shoshonitic volcaniclastic sequences. Unroofing of the accretionary collage, development of a paleosol, and deposition of continental (alluvial-fluvial) sedimentary rocks occurred ca. 1.85–1.84 Ga, coeval with the waning stages of post-accretion arc magmatism. Stabilization of the Flin Flon Belt by 1.85–1.84 Ga as part of a Philippines- or Japan-like microcontinent is attributed to both tectonic and magmatic thickening of the lithosphere.

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