Preferential dissolution of uranium-rich zircon can bias the hafnium isotope compositions of granites

• Published in: Geology (Boulder) 2022-03, Vol.50 (3), p.336-340
• Main Authors: Gao Peng, Gao Peng, Yakymchuk, Chris, Zhang Jian, Zhang Jian, Yin Changqing, Yin Changqing, Qian Jiahui, Qian Jiahui, Li Yanguang, Li Yanguang
• Format: Article
• Language: English
• Subjects: absolute age; Archives & records; Asia; Cenozoic; chemical composition; China; Continental crust; Dissolution; Dissolving; Far East; Geochronology; Geochronometry; Geology; Granite; granites; Hafnium; Hafnium isotopes; Heredity; Hf-177/Hf-176; High temperature; Himalayas; igneous and metamorphic rocks; igneous rocks; intrusions; Isotope composition; Isotope ratios; Isotopes; Low temperature; Melting; metals; Miocene; Nariyongcuo Pluton; Neogene; nesosilicates; orthosilicates; Petrogenesis; Petrology; plutonic rocks; plutons; Radiation; Radiation damage; Radiometric dating; Saturation; silicates; solution; stable isotopes; temperature; Tertiary; Trace elements; Tracers; U/Pb; Uranium; Xizang China; Zircon; zircon group
• ISSN: 0091-7613; 1943-2682
• DOI: 10.1130/G49656.1

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 (