Slave Craton basement complex

Fig. 1. Relative probability histograms of Slave craton detrital zircons (continuous curve with black infill below based on data from Sircombe et al. 2001), Ar/ Ar ages of impact spherules in lunar soil samples (dash-dot curve after Culler et al. 2000), and Ar/ Ar ages of impact glasses in lunar meteorites (dashed curve after Cohen et al. 2000). Time interval spans from 4500 Ma, the approximate age of formation of the Moon, to 2500 Ma, the defined Archaean-Proterozoic boundary. Vertical scales of the three curves are independent. Shaded age bars with roman numerals represent main events in basement of the Slave craton that were initially defined on the basis of individual rock age and their inheritance (see Bleeker Davis 1999). The detrital zircon data represent c. 300 zircon grains from five widely distributed samples of a c. 2800 Ma quartzite unit overlying the Mesoarchaean to Hadean-age basement complex of the Slave craton. These data represent a least-biased record of pre-2.8 Ga components of the Slave craton. The broad complementarity in the datasets should be noted. With the first major peak in Slave crustal ages (event V 3100-3200 Ma) immediately following the last major peak in the lunar spherule data. Both lunar soil and meteorite data sets support a lunar cataclysm or late heavy bombardment that appears to have erased or swamped out the pre-4.0Ga lunar record.

Fig. 2. Geology and generalized stratigraphy of the Slave craton. (a) Geology map location of WSW-ENE cross-section line should be noted (red line see Fig. 3). Light purple overlay outlines minimum extent of the Mesoarchean to Hadean basement complex of the Slave craton. (b) Typical stratigraphy that overlies the basement complex precise zircon ages from Isachsen Bowring (1997), Bleeker et al. (1999a, b) and Ketchum Bleeker (unpubl. data), (c) Generalized stratigraphy for the entire craton.

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