146Sm-142Nd evidence from Isua metamorphosed sediments for early differentiation of the Earth's mantle

Details 146Sm-142Nd evidence from Isua metamorphosed sediments for early differentiation of the Earth's mantle 146Sm-142Nd evidence from Isua metamorphosed sediments for early differentiation of the Earth's mantle

May 2003

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2003natur.423..428c&link_type=abstract

Nature, Volume 423, Issue 6938, pp. 428-432 (2003).

Physics

49

Scientific paper

Application of the 147Sm-143Nd chronometer (half-life of 106Gyr) suggests that large-scale differentiation of the Earth's mantle may have occurred during the first few hundred million years of its history. However, the signature of mantle depletion found in early Archaean rocks is often obscured by uncertainties resulting from open-system behaviour of the rocks during later high-grade metamorphic events. Hence, although strong hints exist regarding the presence of differentiated silicate reservoirs before 4.0Gyr ago, both the nature and age of early mantle differentiation processes remain largely speculative. Here we apply short-lived 146Sm-142Nd chronometry (half-life of 103Myr) to early Archaean rocks using ultraprecise measurement of Nd isotope ratios. The analysed samples are well-preserved metamorphosed sedimentary rocks from the 3.7-3.8-Gyr Isua greenstone belt of West Greenland. Our coupled isotopic calculations, combined with an initial ɛ143Nd value from ref. 6, constrain the mean age of mantle differentiation to 4,460 +/- 115Myr. This early Sm/Nd fractionation probably reflects differentiation of the Earth's mantle during the final stage of terrestrial accretion.

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