Abstract One hundred and five lead isotope analyses have been obtained for 47 volcanogenic massive sulfide deposits and occurrences within the Abitibi and Wawa subprovinces, largely from minor amounts of galena that form an integral part of the deposits. When 52 nonanomalous compositions for the best dated of these deposits are recalculated to a uniform age of 2716 Ma, they define the Abitibi-Wawa linear array at a slope of 1.034 ± 0.062. Two-stage calculation yields an age of 4490 ± 35 Ma for the Pb isotope sources responsible for this linear array if they each subsequently evolved in a single-stage manner from a source that was homogeneous prior to about 4490 Ma. If the assumption of single-stage evolution is valid, 4490 ± 35 Ma could represent the time of a major mantle differentiation event. The data indicate that the lead in deposits for a distance of at least 710 km from Matagami, Quebec, to the Winston Lake deposit in the Terrace Bay-Schreiber area of Lake Superior, Ontario, was derived from equivalent sources. This evidence helps confirm that the Abitibi and Wawa subprovinces, contiguous except for the Kapuskasing tectonic zone, had, at least in some respects, a common evolution history. Further study will be required to show that the Shebandowan subprovince west of Lake Superior, considered an extension of the Wawa subprovince, shared this isotopic history. The Pb isotope data for deposits in the Wabigoon and Uchi subprovinces of western Superior province, which lie to the north of the Wawa-Shebandowan belts, indicate strikingly different isotopic sources that were more isotopically evolved at a given age. The use of data for older deposits elsewhere in the world permits initial isotopic parameters (A o = 9.431, B o = 10.495, C o = 29.681) to be established for the Abitibi-Wawa model at 4490 Ma. In contrast to the Wabigoon-Uchi model (formerly referred to as the “western Superior model”), the Abitibi-Wawa model is not widely applicable elsewhere in the world. However, it does yield congruent model ages for some volcanogenic massive sulfide deposits in the Yilgarn craton, Western Australia, which shows that it has validity beyond the Abitibi-Wawa greenstone belts. Analyses for deposits of the Manitouwadge district, Ontario, and for an Archean deposit within the Grenville province east of Val d’Or, Quebec, illustrate the minor influence of high-grade, upper amphi-bolite to granulite metamorphism on Pb isotope compositions. Anomalous compositions were obtained for galenas from veins and for most low lead sulfides, such as pyrite and sphalerite. These indicate that a Grenvillian remobilization or isotopic resetting occurred throughout the Abitibi subprovince, although the character of such an event in the Matagami district, 190 km from the Grenville front, is very obscure. Other older events are also indicated by the data.

Abstract Eo- to Mesoarchaean greenstone belts (e.g. 3800–3700 Ma Isua, c . 3075 Ma Ivisaartoq, 3071 Ma Qussuk) occur within orthogneisses of the southern West Greenland Craton. Greenstone belts are composed mainly of metavolcanic rocks with minor ultramafic and sedimentary schists. Compositionally, volcanic rocks are dominantly tholeiitic basalts, boninites, and picrites, with minor intermediate to felsic volcanic rocks. These greenstone belts appear to have formed in convergent margin geodynamic settings. Detailed field observations, contrasting ages, and metamorphic and structural histories suggest that this craton was assembled in several accretionary tectonothermal events, involving accretion of arcs, back-arcs, forearcs, and continental fragments by horizontal tectonics. The Superior Province of Canada was also built by the amalgamation of oceanic and continental fragments ranging in age from 3700 to 2650 Ma, during five discrete tectonothermal events over 40 Ma between 2720 and 2680 Ma. The Neoarchaean (2750–2670 Ma) Wawa greenstone belts are composed of tectonically juxtaposed fragments of oceanic plateaux, oceanic island arcs, back-arcs, and siliciclastic trench turbidites. Following juxtaposition, these diverse lithologies were collectively intruded by syn- to post-kinematic granitoids with subduction zone geochemical signatures. Oceanic island arc lavas are easily distinguished from oceanic plateau counterparts because they possess positively fractionated rare earth element (La/Sm cn > 1 and Gd/Yb cn > 1) and high field strength element depleted (Nb/Th pm < 1; Nb/La pm < 1) patterns. In addition, the island arc association includes pyroclastic rocks that are rare to absent in the oceanic plateau volcanic association. Structural studies indicate that the Wawa greenstone belts underwent a complex history of deformation including thrusting, strike-slip faulting, and asymmetric folding. These belts constitute part of a c . 1000 km scale subduction–accretion complex that formed along an intra-oceanic convergent plate margin during trenchward migration of the magmatic arc axis. Several first-order geological observations on Archaean greenstone belts of SW Greenland and the Superior Province suggest that Phanerozoic-style plate-tectonic models can provide an elegant explanation for their structural, lithological, metamorphic and geochemical characteristics.