Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
5783421 | Geochimica et Cosmochimica Acta | 2017 | 49 Pages |
Abstract
The Si-rich sediments have slightly positive εNd (t=3.23Ga) but extremely radiogenic εHf (t=3.23Ga), up to +11. Based on analyses of 3.4 Ga Buck Reef cherts, we suggest that the radiogenic Hf isotopic signature of the Si-rich sediments can be accounted for by the old chert clasts or detrital silicified rock fragments present in the rocks. The latter have extremely high Lu/Hf ratios such that their εHf values would increase dramatically, by about +100 epsilon units every 100 Ma. In the Ca-, Fe-rich sediments, one sample contains carbonate that preserves the typical rare-earth element features of seawater precipitates. The initial Nd isotopic composition of this sample (εNd (t=3.23Ga) = +1.7) is within the range of previous estimates for Archean anoxic seawater.
Related Topics
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Geochemistry and Petrology
Authors
M. Garçon, R.W. Carlson, S.B. Shirey, N.T. Arndt, M.F. Horan, T.D. Mock,