MINTO BLOCK, SUPERIOR PROVINCE - MISSING LINK IN DECIPHERING ASSEMBLYOF THE CRATON AT 2.7 GA

Plate-tectonic models of the Superior province are rooted in the grani te-greenstone and metasedimentary belts of the southern part of the cr aton. North-striking domains of the Minto block in the northeastern pa rt of the province evolved at similar times, in 3.1-2.8, 2.725, and 2. 69 Ga events, requiring expansion of models of late Archean assembly t o accommodate Minto geology. Western and eastern protocratons (approxi mately 3.1-2.8 Ga) rifted at approximately 2.79 Ga to produce an ocean basin that was mostly consumed by subduction at 2.725 Ga. The Leaf Ri ver plutonic suite of calc-alkalic hornblende + biotite +/- orthopyrox ene +/- clinopyroxene granodiorite represents magmatic arcs built on t he protocratons, whereas the intervening Goudalie domain-containing fa ult-bounded fragments of rifted continental crust, rift volcanics, pri mitive oceanic crust, 2724 Ma island-arc rocks, and a <2718 Ma back-ar c assemblage-marks the suture. Terminal collision at approximately 2.7 Ga led to thickening and crustally derived granitoid magmatism. The s outhern Superior province also experienced vigorous activity between 2 .725 and 2.69 Ga as island arcs, oceanic plateaus, continental fragmen ts, and accretionary prisms were amalgamated progressively from north to south in a regime of dextral transpression then stitched by granite s. A northern proto-Superior craton had continental magmatic arcs buil t on its eastern and southern flanks in response to west-northwest-dir ected subduction; orthogonal convergence in the east produced wide plu tonic arcs, in contrast to terrane-accretion tectonics in the more obl ique regime along the southern margin.