Zircon inherited

Chen Y. and Williams I. S. (1990) Zircon inheritance in mafic inclusions from Bega Batholith granites, southeastern Australia an ion microprobe study. J. Geophys. Res. 95, 17787-17796. 

Are the cyclic, bimodal, mafic to felsic sequences such as those of the Abitibi greenstone belt compatible with an oceanic plateau origin The zircon inheritance as well as the abimdance of felsic volcanic rocks seem incompatible with such an origin. Hence, where are the Ontong-Java plateaux of the past (cf. Kerr et al. 2000) ... 

Williams I. S., Chappell B. W., Chen Y. D., and Crook K. A. W. (1992) Inherited and detrital zircons—vital clues to the granite protoliths and early igneous history of southeastern Australia. Trans. Roy. Soc. Edinburgh Earth Set 83, 503. 

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.

As already discussed, in the Abitibi greenstone belt of the Superior craton, extensive dating of volcanic units, their inherited zircons, and feeder dykes cutting imits lower in the stratigraphy has established coherent stratigraphy where previous workers had proposed a tectonic collage. 

For the Bulawayo, Midlands and Harare greenstone belts, inherited zircons in the felsic volcanic rocks yield ages between 2895 and 2650 Ma (Fig. 2a), suggesting that juvenile or mixed continental crustal material was involved in their petrogenesis. Intermediate and felsic volcanic rocks make up more than half of the... 

They also analyzed zircon fractions from grano-diorite at Serpan Peak (Neptune Range) which define two discordia lines that converge to a lower intercept on concordia at 448 6 Ma. The dates of the upper intercepts are 981 31 Ma and -1700 Ma. These upper-intercept dates represent the approximate average age of zircon crystals which the granite magma inherited from its source. 

FIGURE 31.10 Backscattered electron image of zircon grain 4 showing an inherited core (dark area 1755 12 Ma) and a younger rim (lighter area). 

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