Preferential dissolution of uranium-rich zircon can bias the hafnium isotope compositions of granites
| Autor: | Peng Gao, Changqing Yin, Chris Yakymchuk, Jian Zhang, Yanguang Li, Jiahui Qian |
|---|---|
| Rok vydání: | 2021 |
| Předmět: | |
| Zdroj: | Geology. 50:336-340 |
| ISSN: | 1943-2682 0091-7613 |
| Popis: | Hafnium (Hf) isotopes in zircon are important tracers of granite petrogenesis and continental crust evolution. However, zircon in granites generally shows large Hf isotope variations, and the reasons for this are debated. We applied U-Pb geochronology, trace-element, and Hf isotope analyses of zircon from the Miocene Himalayan granites to address this issue. Autocrystic zircon had εHf values (at 20 Ma) of–12.0 to–4.3 (median =–9). Inherited zircon yielded εHf values (at 20 Ma) of–34.8 to +0.3 (median =–13); the majority of εHf values were lower than those of autocrystic zircon. The εHf values of inherited zircon with high U concentrations resembled those of autocrystic zircon. Geochemical data indicates that the granites were generated during relatively low-temperature (820–850 °C) generally contain autocrystic and inherited zircons with comparable Hf isotope values. During higher-temperature melting, indiscriminate dissolution of source zircon until saturation is reached will result in near-complete inheritance of Hf isotope ratios from the source. Our results impose an extra layer of complexity to interpretation of the zircon Hf isotope archive that is not currently considered. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|