Reconstructing crustal thickness evolution from europium anomalies in detrital zircons

A new data compilation shows that in intermediate to felsic rocks, zircon Eu/Eu* [chondrite normalized Eu/√(Sm×Gd)] correlates with whole rock La/Yb, which has been be used to infer crustal thickness. The resultant positive correlation between zircon Eu/Eu* and crustal thickness can be explained by...

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Bibliographic Details
Published in:Geology (Boulder) 2021-01, Vol.49 (1), p.76-80
Main Authors: Tang Ming, Tang Ming, Ji Weiqiang, Ji Weiqiang, Chu, Xu, Wu Anbin, Wu Anbin, Chen Chen, Chen Chen
Format: Article
Language:English
Subjects:
Anomalies
Asia
Cenozoic
chemical ratios
China
Cretaceous
crust
crustal thickening
Crustal thickness
Deformation
detrital zircon
Europium
europium anomaly
Evolution
Far East
Fractionation
Gangdese Belt
Garnet
geochemical anomalies
Geochemistry
Geology
Geophysics
high pressure
Isotopes
La/Yb
lanthanum
magmatic differentiation
melts
Mesozoic
metals
Mountains
nesosilicates
orthosilicates
Oxidation
Paleogene
partitioning
Plagioclase
pressure
rare earths
reconstruction
rock, sediment, soil
Rocks
silicates
solid Earth (tectonophysics)
stream sediments
Tertiary
Thickening
Thickness
valency
Xizang China
ytterbium
Zircon
zircon group
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Summary:A new data compilation shows that in intermediate to felsic rocks, zircon Eu/Eu* [chondrite normalized Eu/√(Sm×Gd)] correlates with whole rock La/Yb, which has been be used to infer crustal thickness. The resultant positive correlation between zircon Eu/Eu* and crustal thickness can be explained by two processes favored during high-pressure differentiation: (1) supression of plagioclase, and (2) endogenic oxidation of Eu2+ due to garnet fractionation. Here we calibrate a crustal thickness proxy based on Eu anomalies in zircons. The Eu/Eu*-in-zircon proxy makes it possible to reconstruct crustal thickness evolution in magmatic arcs and orogens using detrital zircons. To evaluate this new proxy, we analyzed detrital zircons separated from modern river sands in the Gangdese belt, southern Tibet. Our results reveal two episodes of crustal thickening (to 60-70 km) since the Cretaceous. The first thickening event occurred at 90-70 Ma, and the second at 50-30 Ma following Eurasia-India collision. These findings are temporally consistent with contractional deformation of sedimentary strata in southern Tibet.
ISSN:0091-7613
1943-2682
DOI:10.1130/G47745.1