H. Huang
Garnet effect on Nd-Hf isotope decoupling: Evidence from the Jinfosi batholith, Northern Tibetan Plateau
Huang, H.; Niu, Yaoling; Mo, X.X.
Authors
Yaoling Niu
X.X. Mo
Abstract
The initial Nd and Hf isotope ratios of a 420 Ma post-collisional dioritic-granitic batholith from the Northern Tibetan plateau define a negative trend above and orthogonal to the ԐHf(t)-ԐNd(t) terrestrial array. This uncommon trend offers an insight into the origin of the puzzling Nd-Hf isotope decoupling in the crustal rocks. On this trend, samples depleted in heavy rare earth elements (HREEs, i.e., [Dy/Yb]N ≫ 1) deviate most from the terrestrial array whereas samples with flat HREEs (i.e., [Dy/Yb]N ≥ 1) deviate less or plot within the terrestrial array, pointing to the controlling effect of garnet in the magma source. Ancient garnet-bearing residues after melt extraction will have elevated Lu/Hf ratios and can evolve with time to produce high ԐHf(t) at a low ԐNd(t) value. Mixing of melts derived from such source lithologies (high Lu/Hf) with melts possessing a within-terrestrial array Nd-Hf isotopic composition (low Lu/Hf) best explains the observed trend orthogonal to the terrestrial array. The samples from the Jinfosi batholith with the most decoupled Nd-Hf isotope compositions require a larger degree (> 40%) and ancient (i.e., ≥ 1.8 Gyr) previous melt extraction from their source. It follows that the ancient melts with depleted HREEs complementary to those garnet-bearing residues should have low ԐHf values and plot below the terrestrial array, which is indeed shown by some Archean/Paleoproterozic TTGs.
Citation
Huang, H., Niu, Y., & Mo, X. (2017). Garnet effect on Nd-Hf isotope decoupling: Evidence from the Jinfosi batholith, Northern Tibetan Plateau. Lithos, 274-275, 31-38. https://doi.org/10.1016/j.lithos.2016.12.025
Journal Article Type | Article |
---|---|
Acceptance Date | Dec 21, 2016 |
Online Publication Date | Dec 31, 2016 |
Publication Date | Mar 1, 2017 |
Deposit Date | Feb 6, 2017 |
Publicly Available Date | Mar 29, 2024 |
Journal | Lithos |
Print ISSN | 0024-4937 |
Publisher | Elsevier |
Peer Reviewed | Peer Reviewed |
Volume | 274-275 |
Pages | 31-38 |
DOI | https://doi.org/10.1016/j.lithos.2016.12.025 |
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http://creativecommons.org/licenses/by-nc-nd/4.0/
Copyright Statement
© 2016 This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/
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