Northeast Superior Province, Douglas Harbour Domain
The Douglas Harbour domain is the eastern-most domain in the northeast Superior province (3.1 to 2.7 Ga) and lies east of Hudson and James Bays. It is dominated by 2.78-2.69 Ga plutonic rocks emplaced into older crust (3.8-2.83 Ga). U-Pb ages obtained through SHRIMP analyses of zircon samples reveal a history of successive magmatism between 3.07 and 2.70 Ga, followed by metamorphism, emplacement of crustally-derived granites (2.702-2.685 Ga), and late hydrothermal events (ca. 2.65 Ga). In the northeastern Minto block of the Douglas Harbour domain, dated localities to the northeast are 2.87 Ga. The Leaf River suite is dated at 3.01 Ga and the tonalitic crust contains 2.734-2.725 Ga granodioritic plutons. (Percival et al., 2001).
To the east of the Douglas Harbour domain are the Utsalik, Goudalie, Lac Minto and Tikkerutuk domains that yield almost exclusively late Archean ages of 3.0 to 2.7 Ga. This range of ages is evidence for recycling of earlier crustal lithologies by younger orogenic events and reflects melting of mid-Archean lithologies during the emplacement of juvenile late Archean magmas.
The Douglas Harbour Domain includes two TTG suites: the Faribault-Thury West and the Faribault-Thury East. Both contain embedded KT greenstone belts. The tonalities display elevated La/Yb ratios and are enriched in LILE (Ba-Rb-K-Cs-U-Th-Pb) with Sr-Pb anomalies and B Nb-Ta-Ti anomalies. This implies melting rates of subducted oceanic crust, but could also be the result of melting at the base of a basaltic plateau in the presence of garnet and rutile. Trace element models collectively imply that the evolution of trondhjemitic tonalite resulted from hornblende-dominated crystallization and is probably not caused by variable rates of partial melting in the subducted oceanic crust. The repetitive process of catalytic delamination explains the synchronous genesis of Archean crust and mantle, explains progressive crustal maturation (tonalite to granite transition), and simplifies tectonic models because all Archean magmatic suites can be generated in a single environment. (Bedard, 2005).
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