In:
Proceedings of the National Academy of Sciences, Proceedings of the National Academy of Sciences, Vol. 107, No. 24 ( 2010-06-15), p. 10810-10814
Abstract:
Recent high precision 142 Nd isotope measurements showed that global silicate differentiation may have occurred as early as 30–75 Myr after the Solar System formation [Bennett V, et al. (2007) Science 318:1907–1910]. This time scale is almost contemporaneous with Earth’s core formation at ∼30 Myr [Yin Q, et al. (2002) Nature 418:949–952]. The 182 Hf- 182 W system provides a powerful complement to the 142 Nd results for early silicate differentiation, because both core formation and silicate differentiation fractionate Hf from W. Here we show that eleven terrestrial samples from diverse tectonic settings, including five early Archean samples from Isua, Greenland, of which three have been previously shown with 142 Nd anomalies, all have a homogeneous W isotopic composition, which is ∼2 ε -unit more radiogenic than the chondritic value. By using a 3-stage model calculation that describes the isotopic evolution in chondritic reservoir and core segregation, as well as silicate differentiation, we show that the W isotopic composition of terrestrial samples provides the most stringent time constraint for early core formation (27.5–38 Myr) followed by early terrestrial silicate differentiation (38–75 Myr) that is consistent with the terrestrial 142 Nd anomalies.
Type of Medium:
Online Resource
ISSN:
0027-8424
,
1091-6490
DOI:
10.1073/pnas.0913605107
Language:
English
Publisher:
Proceedings of the National Academy of Sciences
Publication Date:
2010
detail.hit.zdb_id:
209104-5
detail.hit.zdb_id:
1461794-8
SSG:
11
SSG:
12
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