Abstract

Middle-Late Jurassic high Sr/Y granitic intrusions are extensively exposed in the Liaodong Peninsula, in the eastern part of the North China Craton (NCC). However, the genesis of the high Sr/Y signature in these intrusions has not been studied in detail. In this study, we report results of zircon U-Pb dating, Hf isotopic analysis and zircon and whole-rock geochemical data for the Late Jurassic Zhoujiapuzi granite in the middle part of the Liaodong Peninsula. The Zhoujiapuzi granite is high-K (calc-alkaline) and peraluminous in nature, with high SiO2 (68.1–73.0 wt %) and Al2O3 (14.5–16.8 wt %), low in TFe2O3 (1.10–2.49 wt %) and MgO (0.10–0.44 wt %), and with high Sr/Y (19.9–102.0) and LaN/YbN (14.59–80.40). Morphological and chemical studies on zircon grains show that there are two stages of zircon growth, interpreted as magmatic evolution in two distinct stages. The early stage of zircons (ESZ) reflects a crystallization environment of low oxygen fugacity and high TZr-Ti (Ti-in-zircon thermometer values: 669–792 °C); the late stage of zircons (LSZ) formed with high oxygen fugacity and lower TZr-Ti (498–720 °C). LA-ICP-MS U-Pb zircon dating yielded the formation ages of the ESZ and LSZ of ~162 ± 1 Ma and ~158 ± 1 Ma, respectively, with similar εHf(t) values in the range of &minus26.3– −22.8. Interpretation of the elemental and isotopic data suggests that the Zhoujiapuzi granite was a I-type granite derived from partial melting of basement in the region: ~2.17 Ga Liaoji granites. The high Sr/Y signature is most likely inherited from these source rocks. Based on the geochemical features and regional geological data, we propose that the Liaodong Peninsula in the Late Jurassic was part of a mature continental arc, with extensive melting of thick crust above the Paleo-Pacific subduction zone.

Highlights

  • The Liaodong Peninsula is located in the northeast of the North China Craton (NCC)

  • Middle-Late Jurassic high Sr/Y granitic intrusions are extensively exposed in the Liaodong Peninsula, in the eastern part of the North China Craton (NCC)

  • 25 Based on the geochemical features and regional geological data, we propose that the Liaodong Peninsula in the Late Jurassic was part of a mature continental arc, with extensive melting of thick crust above the Paleo-Pacific subduction zone

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Summary

Introduction

The Liaodong Peninsula is located in the northeast of the North China Craton (NCC). The northeast NCC was influenced by three main tectonic regimes in the Mesozoic, related to the subduction of the Paleo-Asian, Paleo-Pacific and Mongol Okhotsk oceans (Tang et al, 2018). The petrogenesis of the Middle-Late Jurassic high Sr/Y rocks needs to be reevaluated, based on more detailed work and a consideration of possible sources This 45 petrogenesis is of significance for understanding the Jurassic tectonics of the Liaodong Peninsula, and the NCC in general. Some of them, exposed near later extensional structures, have undergone regional ductile deformation These Jurassic magmatic rocks are generally considered to relate to the subduction of the Paleo-Pacific slab (Li et al, 2004; Zhai et al, 2004). 75 them, the granites have mainly A- and I-type affinities These rocks are generally considered to have formed in an intense extension environment, which is connected with either the rollback or low-angle subduction of the Paleo-Pacific slab (Wu et al, 2005c; Zheng et al, 2018). Detailed analytical procedures refer to Zhang et al (2019) and Nash et al (2020)

Whole-rock major and trace element compositions
Zircon CL images, Raman spectra and REE elements
Significance of the two stages of zircon
Genetic type
Petrogenesis of the high Sr/Y granite The samples of the
Model A
Model B
Model C
Model D
Model E
Model F
Tectonic implications
Conclusion
430 Acknowledgements
Full Text
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