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| Content Provider | World Health Organization (WHO)-Global Index Medicus |
|---|---|
| Author | Yamaguchi, Takao Hibiya, Yuki Amelin, Yuri Iizuka, Tsuyoshi |
| Description | Author Affiliation: Iizuka T ( Department of Earth and Planetary Science, The University of Tokyo, Tokyo 113-0033, Japan); Yamaguchi T ( Department of Earth and Planetary Science, The University of Tokyo, Tokyo 113-0033, Japan); Hibiya Y ( Department of Earth and Planetary Science, The University of Tokyo, Tokyo 113-0033, Japan); Amelin Y ( Research School of Earth Sciences, The Australian National University, Canberra, ACT 0200, Australia.); |
| Abstract | Knowledge of planetary differentiation is crucial for understanding the chemical and thermal evolution of terrestrial planets. The (176)Lu-(176)Hf radioactive decay system has been widely used to constrain the timescales and mechanisms of silicate differentiation on Earth, but the data interpretation requires accurate estimation of Hf isotope evolution of the bulk Earth. Because both Lu and Hf are refractory lithophile elements, the isotope evolution can be potentially extrapolated from the present-day (176)Hf/(177)Hf and (176)Lu/(177)Hf in undifferentiated chondrite meteorites. However, these ratios in chondrites are highly variable due to the metamorphic redistribution of Lu and Hf, making it difficult to ascertain the correct reference values for the bulk Earth. In addition, it has been proposed that chondrites contain excess (176)Hf due to the accelerated decay of (176)Lu resulting from photoexcitation to a short-lived isomer. If so, the paradigm of a chondritic Earth would be invalid for the Lu-Hf system. Herein we report the first, to our knowledge, high-precision Lu-Hf isotope analysis of meteorite crystalline zircon, a mineral that is resistant to metamorphism and has low Lu/Hf. We use the meteorite zircon data to define the Solar System initial (176)Hf/(177)Hf (0.279781 ± 0.000018) and further to identify pristine chondrites that contain no excess (176)Hf and accurately represent the Lu-Hf system of the bulk Earth ((176)Hf/(177)Hf = 0.282793 ± 0.000011; (176)Lu/(177)Hf = 0.0338 ± 0.0001). Our results provide firm evidence that the most primitive Hf in terrestrial zircon reflects the development of a chemically enriched silicate reservoir on Earth as far back as 4.5 billion years ago. |
| ISSN | 00278424 |
| e-ISSN | 10916490 |
| Journal | Proceedings of the National Academy of Sciences of the United States of America |
| Issue Number | 17 |
| Volume Number | 112 |
| Language | English |
| Publisher | National Academy of Sciences |
| Publisher Date | 2015-04-01 |
| Publisher Place | United States |
| Access Restriction | Open |
| Subject Keyword | Multidisciplinary |
| Content Type | Text |
| Resource Type | Article |
| Subject | Multidisciplinary |
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