Coupled 182W-142Nd constraint for early Earth differentiation

• Published in: Proceedings of the National Academy of Sciences
• Main Authors: Moynier, Frédéric, Yin, Qing-Zhu, Irisawa, Keita, Boyet, Maud, Jacobsen, Benjamin, Rosing, Minik
• Other Authors: McDonnell Center for Space Sciences, Washington University in Saint Louis (WUSTL), Department of Earth and Planetary Sciences St Louis, Department of Geology Davis, University of California Davis (UC Davis), University of California (UC)-University of California (UC), Department of Earth and Planetary Sciences TITECH Tokyo, Tokyo Institute of Technology Tokyo (TITECH), Laboratoire Magmas et Volcans (LMV), Observatoire de Physique du Globe de Clermont-Ferrand (OPGC), Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Blaise Pascal - Clermont-Ferrand 2 (UBP)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS)-Université Jean Monnet - Saint-Étienne (UJM)-Centre National de la Recherche Scientifique (CNRS), Nordic Centre of Earth Evolution (NORDCEE), University of Copenhagen = Københavns Universitet (UCPH)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2010
• Subjects: hafnium; tungsten; hidden reservoir; Hawaï; Iceland; [SDU.STU.GC]Sciences of the Universe [physics]/Earth Sciences/Geochemistry; [SDE.MCG]Environmental Sciences/Global Changes; Greenland
• Online Access: https://hal.science/hal-00515962; https://doi.org/10.1073/pnas.0913605107

International audience 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 approximately 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 approximately 2epsilon-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.