Abstract
SOME prominence has been given recently to the results and implications of isotope age studies1–4 in the early Precambrian rocks of the Godthåb region, southern West Greenland. The studies were initiated after field investigations5 suggested that the Godthåbsfjord region may contain outcrops of the oldest rocks in the earth's crust. McGregor5 has grouped these rocks into an older and a younger set of gneisses (respectively the Amîtsoq and Nûk gneisses) separated in time by dykes (the Ameralik dykes), metavolcanic and metasedimentary rocks (the Malene supracrustals) and stratiform meta-anorthosites. Among conclusions drawn from the isotope work is that based on initial ratios of 87Sr/86Sr that the parents of the Nûk gneisses in the Godthåbsfjord area cannot have been derived by partial or complete melting of the older Amîtsoq gneisses3. We wish to comment on the applicability of this conclusion to the Nûk gneisses mapped in the area immediately to the south.
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References
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Chadwick, B., Coe, K., Gibbs, A. D., Sharpe, M. R., and Wells, P. R. A., Rapp. Greenland geol. Surv. (in the press).
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CHADWICK, B., COE, K., GIBBS, A. et al. Field evidence relating to the origin of ∼ 3,000 Myr gneisses in southern West Greenland. Nature 249, 136–137 (1974). https://doi.org/10.1038/249136a0
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DOI: https://doi.org/10.1038/249136a0
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