Academic Journal
Fluid effect on zircon O and U-Pb isotopes during ultrahigh-pressure metamorphism: Insights from the Dora-Maira Massif of the Western Alps
| العنوان: | Fluid effect on zircon O and U-Pb isotopes during ultrahigh-pressure metamorphism: Insights from the Dora-Maira Massif of the Western Alps |
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| المؤلفون: | Kun Zhou, Yi-Xiang Chen, Jia-Wei Xiong, Hans-Peter Schertl, Xiao-Ping Xia |
| المصدر: | Geoscience Frontiers, Vol 14, Iss 6, Pp 101651- (2023) |
| بيانات النشر: | Elsevier |
| سنة النشر: | 2023 |
| المجموعة: | Directory of Open Access Journals: DOAJ Articles |
| مصطلحات موضوعية: | Subduction zone, Fluid action, Metasomatism, Zircon, O isotope, U-Pb dating, Geology, QE1-996.5 |
| الوصف: | Zircon geochemistry such as U-Pb and O isotopes have been widely used in dating and tracing complex geological processes. However, it still remains unclear how fluid action affects zircon geochemistry during metamorphic and metasomatic processes in subduction zones. Here a systematic study on zircon U-Pb dating, O isotopes and trace elements as well as whole-rock O isotopes was carried out for the coesite-bearing whiteschists, jadeite quartzites and granitic gneisses from the Dora-Maira Massif, Western Alps. Whole-rock and zircon geochemistry supports a common protolith, i.e., Permian S-type granites, for the above three types of rocks and an intense fluid metasomatism during the Alpine orogeny to form whiteschists and jadeite quartzites. Zircon cores in all samples have nearly identical δ18O values (9‰–11‰), whereas their apparent 206Pb/238U ages show a greater variability due to Pb loss during metamorphism. Zircon rims formed in the late Eocene to early Oligocene can be categorized into two types. Type-I rims occur in granitic gneisses and jadeite quartzites. They have high δ18O values consistent with zircon cores, but much lower contents of P and Y as well as lower Th/U ratios than the cores. Their growth can be attributed to internal metamorphic fluid action at the UHP metamorphic stage. Type-II rims occur in whiteschists and jadeite quartzites. They have remarkably lower δ18O values (5‰–8‰) and Th/U ratios (<0.01), compared with zircon cores and Type-I rims. Their growth can be ascribed to external fluids during the metasomatic process. Some zircon domains in whiteschists and jadeite quartzites show a positive correlation between δ18O values and apparent 206Pb/238U ages, which suggest the simultaneous impacts on U-Pb-O isotopes during external fluid metasomatism. This process can be attributed to the fluid-assisted dissolution and recrystallization of protolith zircons. Especially, coesite inclusions that would have been expected to occur only in young zircon rims formed during UHP metamorphism are also ... |
| نوع الوثيقة: | article in journal/newspaper |
| اللغة: | English |
| تدمد: | 1674-9871 |
| Relation: | http://www.sciencedirect.com/science/article/pii/S1674987123001184; https://doaj.org/toc/1674-9871; https://doaj.org/article/9862ca5c9b214115b5a76f6cd438afe2 |
| DOI: | 10.1016/j.gsf.2023.101651 |
| الاتاحة: | https://doi.org/10.1016/j.gsf.2023.101651 https://doaj.org/article/9862ca5c9b214115b5a76f6cd438afe2 |
| رقم الانضمام: | edsbas.5B7231C1 |
| قاعدة البيانات: | BASE |
Full Text Finder | تدمد: | 16749871 |
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| DOI: | 10.1016/j.gsf.2023.101651 |