Eo-Paleoarchean detrital zircon in the Winnipeg River terrane, Western Superior Province: Provenance and implications

Abstract

Metasedimentary rocks within Archean cratons can preserve a record of early cratonic crustal evolution and later metamorphic events. However, interpreting this record is difficult where the metasedimentary rocks have undergone amphibolite-granulite facies metamorphic overprinting and migmatization. In the Western Superior Province, migmatitic metasedimentary rocks represent a dominant supracrustal component in several terranes, including, from north to south, the English River, Winnipeg River, Wabigoon and Quetico terranes. Here we present zircon U-Pb-Hf isotope data for three metasedimentary rocks and one augen gneiss from the Mystery Lake dome in the Winnipeg River plutonic-gneiss terrane using in-situ techniques and large zircon populations. The augen gneiss contains zircon that has overlapping U-Pb-Hf isotope systematics with the ca. 3250 Ma gneissic basement of the terrane. The detrital zircon grains from the metasedimentary rocks have age populations at ca. 3750 Ma, 3600 Ma, 3500 Ma, 3400 Ma, 3300–3100 Ma, 3050 Ma, 2950–2900 Ma, 2850–2800 Ma, and 2800–2745 Ma, with metamorphic zircon between approximately 2745 Ma and 2550 Ma. The paucity of exposed Eo-Paleoarchean rocks in adjacent terranes suggests that the source rocks were derived from within the Winnipeg River terrane. The age and Hf isotope systematics of Eo-Paleoarchean detrital zircons from the Winnipeg River terrane overlap with zircon data from the Hudson Bay and Minnesota River Valley terranes on the northern and southern margins of the craton, respectively. The evidence suggests all three plutonic-gneiss terranes have preserved similar Eo-Paleoarchean geological histories, supporting the hypothesis that they were derived from a contiguous proto-craton.