U-PB GEOCHRONOLOGY AND EVOLUTION OF THE ENGLISH RIVER SUBPROVINCE, ANARCHEAN LOW P-HIGH-T METASEDIMENTARY BELT IN THE SUPERIOR-PROVINCE

U-Pb isotopic data for zircon, monazite, and titanite are used to asse ss the evolution of the late Archean English River Subprovince (ERS) a nd adjacent domains of the Winnipeg River Subprovince in the northern Superior Province, Ontario. The ERS consists of turbiditic metasedimen tary rocks, deposited during the final stages of magmatic and tectonic accretion within the greenstone-granite Uchi Subprovince to the north at around 2720 to 2710 Ma. The sedimentary rocks were intruded by a s uite of calc-alkalic plutons at 2698 Ma. Major regional deformation, a mphibolite to granulite facies metamorphism, anatexis, and emplacement of an extensive peraluminous granitic suite culminated at 2691 Ma. La te episodes of metamorphism, metasomatism, and emplacement of pegmatit es occurred locally at circa 2680 and 2669 Ma. In contrast, the Winnip eg River Subprovince to the south consists of widespread tonalitic sui tes formed mainly between 3200 and 2800 Ma and granodioritic to granit ic intrusions formed between 2710 and 2690 Ma. Metamorphism occurred a t around 2710 Ma in southern domains, and a distinct granulite facies event at around 2680 Ma affected central and northern domains of the W innipeg River Subprovince. The rapid sequence of events recorded in th e ERS supports the notion that metamorphism was caused by thermal pert urbations related to injection of granitic magmas. These melts were ge nerated through partial melting of the lower crust by a thermal anomal y presumably caused by mantle upwelling related to collapse of the ina ctivated subducting plate. The short-lived metamorphic events nature o f the follow the cyclicity models linking the evolution of strain rate s to episodes of segregation and upward magma transfer in the course o f prolonged orogenic events. their recent and behaviour predicted by r ecent models linking the evolution of strain rates to episodes of segr egation and upward magma transfer in the course of prolonged orogenic events.