Tracing magma mixing in granite genesis: in situ U–Pb dating and Hf-isotope analysis of zircons |
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| Authors: | Jin-Hui Yang Fu-Yuan Wu Simon A Wilde Lie-Wen Xie Yue-Heng Yang Xiao-Ming Liu |
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| Institution: | (1) State Key Laboratory of Lithospheric Evolution, Institute of Geology and Geophysics, Chinese Academy of Sciences, P.O. Box 9825, Beijing, 100029, China;(2) Department of Applied Geology, Curtin University of Technology, P.O. Box U1987, Perth, WA, 6845, Australia;(3) Key Laboratory of Continental Dynamics, Department of Geology, Northwest University, Xi’an, 750069, China |
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| Abstract: | In situ zircon U–Pb and Hf-isotopic data have been determined for mafic microgranular enclaves and host granitoids from the
Early Cretaceous Gudaoling batholith in the Liaodong Peninsula, NE China, in order to constrain the sources and petrogenesis
of granites. The zircon U–Pb age of the enclaves (120 ± 1 Ma) is identical to that of the host monzogranite (120 ± 1 Ma),
establishing that the mafic and felsic magmas were coeval. The Hf isotopic composition of the enclaves ε
Hf(t) = +4.5 to −6.2] is distinct from the host monzogranite ε
Hf(t) = −15.1 to −25.4], indicating that both depleted mantle and crustal sources contributed to their origin. The depleted mantle
component was not previously revealed by geochemical and Nd and Sr isotopic studies, showing that zircon Hf isotopic data
can be a powerful geochemical tracer with the potential to provide unique petrogenetic information. Some wall-rock contamination
is indicated by inherited zircons with considerably older U–Pb ages and low initial Hf isotopic compositions. Hafnium isotopic
variations in Early Cretaceous zircons rule-out simple crystal–liquid fractionation or restite unmixing as the major genetic
link between enclaves and host rocks. Instead, mixing of mantle-derived mafic magmas with crustal-derived felsic magmas, coupled
with assimilation of wall rocks, is compatible with the data.
Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users. |
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