Zircon isotope evidence for recycling of subducted continental crust in post‐collisional granitoids from the Dabie terrane in China

Geophysical Research Letters - Tập 31 Số 22 - 2004
Zi‐Fu Zhao1,2, Yong‐Fei Zheng2, Chun‐Sheng Wei2, Yuan‐Bao Wu2
1Also at Beijing Ion Microprobe Center, Chinese Academy of Geological Sciences, Beijing, China.
2School of Earth and Space Sciences, University of Science and Technology of China, Hefei, China

Tóm tắt

Recycling of subducted continental crust in continental collision belts is examined by a combined study of zircon U‐Pb dating and O isotope analysis of mineral separates from post‐collisional granitoids in the Dabie terrane, east‐central China. Although zircon U‐Pb dating give concordant ages of 121 to 131 Ma for magma crystallization, the occurrence of inherited cores is identified by CL imaging and SHRIMP dating in some zircon grains that yield older ages of 742 to 815 Ma and 222 Ma, respectively, in agreement with Neoproterozoic protolith ages of UHP metaigneous rocks and Triassic tectono‐metamorphic event in the Dabie‐Sulu orogen. All the samples have zircon δ18O values of 4.14 to 6.11‰, most of which differ from the δ18O value of 5.3±0.3‰ for the normal mantle zircon. This indicates the remelting of continental crust containing both 18O‐depleted and enriched components, with significant isotope homogenization relative to the UHP metaigneous rocks. These observations indicate the involvement of the subducted Yangtze plate in the Cretaceous granitoids and thus provide evidence for geochemical recycling of the continental crust that was thickened by the Triassic collision.

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Geophysical Research Letters

Tập 31 Số 22

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