Tectonic transition during the Jurassic-Cretaceous in the Jiaodong Peninsula, North China: insights from asynchronous adakitic and A-type granitic plutons

ABSTRACT

Jurassic-Cretaceous magmatic rocks are widely distributed in the Jiaodong area, North China. These magmatic rocks are closely associated with gold deposits, but their petrogenesis and geodynamic background are still controversial. The Late Jurassic-Early Cretaceous granitic rocks exposed in the Guocheng area, Jiaodong Peninsula are the focus of this paper. Zircon U-Pb dating, Hf-O isotope and whole rock geochemical analysis are used to determine the petrogenesis of these rocks. Combined with previous data, the geodynamic processes of granite formation in different time intervals are investigated which provide new petrological evidence for understanding the magmatic-mineralization and tectonic background of the Jiaodong area. Samples were collected from the Queshan and Shazibu plutons. The Queshan pluton is a mylonite granite, one sample of which yields a ²⁰⁶U-²³⁸Pb zircon age of 156 Ma, while the Shazibu pluton is a quartz monzonite, one sample of which records a ²⁰⁶U-²³⁸Pb zircon age of 117 Ma. The two plutons have variable zircon Hf-O isotopic compositions: zircon ε_Hf(t) values of the Queshan pluton are −29.2 to −22.8, and δ¹⁸O values are 7.30–7.84 ‰, while the Shazibu pluton has relatively high zircon ε_Hf(t) values (−21.6 to −21.0) and δ¹⁸O values of 7.48–8.43 ‰. Whole-rock geochemical data shows that the Queshan pluton has high Sr/Y (60.7–169) and (La/Yb)_N (34.6–65.9) values and low Y (3.11–10.3 ppm) and Yb (0.29–0.85 ppm) contents, akin to adakites, whereas granites of the Shazibu pluton are A-type with high Zr+Nb+Ce+Y contents (354–420 ppm) and zircon saturation temperatures (752–795°C). Based on the geochemical and isotopic data, the Late Jurassic Queshan pluton is the product of partial melting of thickened lower crust of the North China Block, while the Early Cretaceous Shazibu pluton formed via fractional crystallization of mafic rocks derived from partial melting of the lower crust of the North China Block. Although both plutons were derived from the lower crust of the North China Block, the nature of the lower crust was modified by involvement of more depleted mantle-derived materials during the Early Cretaceous. From the Late Jurassic to the Early Cretaceous, the rock types (from the adakite to A-type granite) and the nature of the magma source suggest a shift in geodynamic processes. Combined with previous research, the Late Jurassic Queshan pluton is proposed to have formed under low-angle subduction of the ancient Pacific Plate, while the Early Cretaceous Shazibu pluton formed subsequently during Pacific Plate rollback and extension. The Early Cretaceous transformation of tectonomagmatic environments provided favourable conditions for the formation of large-scale gold deposits in the Jiaodong region.

Graphical abstract

KEYWORDS:

• Jiaodong peninsula
• North China craton
• Jurassic-Cretaceous
• A-type granite
• adakite
• lithosphere thinning
• gold deposit

Acknowledgments

This work was co-financed by the National Key Research and Development Plan (Grant No. 2016YFC0600104), the Geological Research Project of China National Gold Group Co., Ltd-Xintai Gold Mining Co., Ltd (Yantai, Shandong) (Grant No. XY-DZ2020081, WT-DZ2022001, XY-DZ20210161, XY-DZ2022183, WT-DZ2023074), and the Science and Technology Innovation Program of Hunan Province (Grant No. 2022RC1182, 2021RC4055). SAW acknowledges funding from KFUPM CPG Grant No. CPG21107. We thank Mr. Yuanxian Yue (senior geological engineer of Xintai Gold Mining Co. Ltd) for his great help during field investigation and sampling work.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/00206814.2023.2250846

Additional information

Funding

This work was supported by the National Key Research and Development Plan (Grant No. 2016YFC0600104), the Geological Research Project of China National Gold Group Co., Ltd-Xintai Gold Mining Co., Ltd (Yantai, Shandong) (Grant No. XY-DZ2020081, WT-DZ2022001, XY-DZ20210161, XY-DZ2022183, WT-DZ2023074), and the Science and Technology Innovation Program of Hunan Province (Grant No. 2022RC1182, 2021RC4055).