Spatial-temporal relationships of late Mesozoic granitoids in Zhejiang Province, Southeast China: constraints on tectonic evolution

ABSTRACT

Late Mesozoic granitoids in South China are generally considered to have been generated under the Palaeo–Pacific tectonic regime, however, the precise subduction mechanism remains controversial. Detailed zircon U–Pb geochronological, major and trace element, and Sr–Nd–Hf isotopic data are used to document the spatiotemporal distribution of the granitoids in Zhejiang Province. Three periods of late Mesozoic magmatism, including stage 1 (170–145 Ma), stage 2 (145–125 Ma), and stage 3 (125–90 Ma), can be distinguished based on systematic zircon U–Pb ages that become progressively younger towards the SE. Stage 1 granitic rocks are predominantly I-type granitoids, but minor S- or A-type rocks also occur. Sr–Nd–Hf isotopic data suggest that these granitoids were generated from hybrid magmas that resulted from mixing between depleted mantle-derived and ancient crust-derived magmas that formed in an active continental margin environment related to the low-angle subduction of the Palaeo–Pacific plate beneath Southeast China mainland. Stage 2 granitic rocks along the Jiangshan–Shaoxing Fault are predominantly I- and A-type granitoids with high initial ⁸⁷Sr/⁸⁶Sr, low ε_Nd(t), ε_Hf(t) values and Mesoproterozoic Nd–Hf model ages. These results suggest that stage 2 granitoids were derived from mixing between enriched mantle-derived mafic magmas and ancient crust-derived magmas in an extensional back-arc setting related to rollback of the Palaeo–Pacific slab. Stage 3 granitic rocks along the Lishui–Yuyao Fault comprise mainly A- and I-type granitoids with high initial ⁸⁷Sr/⁸⁶Sr ratios, and low ε_Nd(t) and ε_Hf(t) values, again suggesting mixing of enriched mantle-derived mafic magmas with more ancient crustal magmas in an extensional back-arc setting, related in this case to the continued rollback the Palaeo–Pacific plate and the outboard retreat of its subduction zone.

Graphical Abstract

KEYWORDS:

• Late Mesozoic granitoids
• tectonic evolution
• Zhejiang
• South China Block

Acknowledgements

We would like to thank Prof. Xianhua Li and Qiuli Li from the Institute of Geology and Geophysics, Chinese Academy of Sciences for their assistance with SIMS zircon U–Pb analysis. Thanks are given to Editor-in-Chief Robert J. Stern and Guest Editors Weidong Sun and Xiaoyong Yang for their valuable advice. The authors would like to thank three anonymous reviewers, who greatly improved the discussion part of the paper. Thanks are given to Dr. Thomas Ulrich in Aarhus University for language polishing and constructive comments. This work was supported by the National Natural Science Foundation of China (Grant No. 41502090), Postdoctoral Science Foundation of China (No. 2015M581165) and CSC-sponsored Scholarship Program for Visiting Scholars (No. 201604910054).

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplemental data

Supplemental data for this article can be accessed here.

Additional information

Funding

This work was supported by the National Natural Science Foundation of China [grant number 41502090], Postdoctoral Science Foundation of China [grant number 2015M581165] and CSC-sponsored Scholarship Program for Visiting Scholars [grant number 201604910054].