Crustal evolution and architecture of the Wawa Subprovince, Superior Province: Insights from zircon U-Pb-Hf-O isotopes and geochemistry

Abstract

The tectono-magmatic processes driving the evolution of Archean continental crust in the early-Earth are highly debated topics. To contribute to a better understanding of crustal evolution in the Meso- to Neoarchean, the Wawa subprovince of the Superior Province, comprising ∼ 2.9–2.6 Ga crustal rocks, represents an ideal location, located along-strike of the well-studied and mineralised Abitibi Subprovince. Here, we integrate whole-rock geochemistry and in-situ zircon U-Pb geochronology, Hf-O isotopes and trace element data from new and compiled magmatic samples across, and proximal to, the Wawa subprovince. Geochronology is used to identify four major volcano-magmatic stages at 2900–2750 Ma (I), 2750–2710 Ma (II), 2710–2680 Ma (III) and 2680–2670 Ma (IV), generally correlating with previous studies from the Michipicoten greenstone belt within the Wawa subprovince. Zircon Hf-isotopic data indicate TTG and felsic volcanic rocks follow two distinct crustal evolution lines from ∼ 3.2 Ga (mafic crust) and ∼ 2.9 Ga (felsic crust). We suggest at least two different sources are responsible for generating crust in the southwestern part of the SE Superior Province in the Archean; the older source is less juvenile and relatively dry, and the younger source is more juvenile and hydrous. Integration of isotopic data with whole-rock Sr/Y, La/Yb_N and Nb, indicates that the depth of magma generation from Source 1 is shallower than that from Source 2, indicating an increase in crustal thickness from Stage I through Stage IV. The comparable Hf-isotopic signatures of the Wawa subprovince, Eastern Wabigoon subprovince and Winnipeg River Terrane samples suggest these areas may have a long-lived, shared crustal evolution.