Petrogenesis of the Late Mesozoic Qijinfeng Granite Complex in the Tongbai orogen: Geochronological, geochemical and Sr-Nd-Pb-Hf isotope evidence

A comprehensive study of zircon U–Pb ages, major and trace elements, whole‐rock Sr–Nd–Pb isotopes and zircon Hf isotopes of the gneissic granite and quartz monzonite in the Tongbai Complex is conducted in an attempt to unravel their petrogenesis and shed new light on the tectonic evolution and crust thickening process of the Tongbai orogen. Zircon U–Pb dating indicates that the emplacement of gneissic granite was early at 144.2 ± 1.3 Ma, whereas the quartz monzonite formed later at 130.2 ± 1.7 Ma. Both the gneissic granite and quartz monzonite samples share many chemical similarities, such as high Al2O3, K2O, Sr contents and low MgO contents, together with high Sr/Y, high La/Yb ratios, suggesting an C‐adakitic affinity and possibly derived from partial melting of the thickened lower crust. The later quartz monzonites may have involvement of much more proportion of mantle‐derived materials (such as the metamorphosed mafic rocks, ecologite) in the lower crust during partial melting for its petrogenesis, due to its higher MgO, Cr, Ni, and V contents than the gneissic granites. The formation of the gneissic granite and quartz monzonite records the evolution history for the lower crust thickening beneath the Tongbai orogen at the Cretaceous. Nearly all granitoids in the Tongbai orogen currently found have an emplacement age of >130 Ma and have higher Sr/Y ratios and lower MgO, Cr, Ni, and V contents with respect to the granitoids in the Dabie orogen which occurs in two stages of granitic magmatism of >130 Ma and <130 Ma. The Tongbai orogen lacks the granitoids formed by significant crust–mantle mixing that occurred in the Dabei area at <130 Ma. These results indicate that the lower crust was continuing thickening but probably not delaminated beneath the Tongbai orogeny during the Early Cretaceous.

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Geological Settingmentioning

confidence: 99%

Section: Tongbai Complex and Samplingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Geochronological, geochemical, and Sr–Nd–Pb–Hf isotopes of Cretaceous gneissic granite and quartz monzonite in the Tongbai Complex: Record of lower crust thickening beneath the Tongbai orogen

Niu

Jiang

2021

Two periods of magmatism in the Weishancheng ore concentration area, Henan Province: Evidences from zircon U‐Pb chronology, Hf isotopes and petrogeochemistry

Lin,

Mao,

Lü

et al. 2024

The Weishancheng area of Tongbai County, Henan Province, is an important Au‐Ag polymetallic ore concentration area in China, characterized by a widespread distribution of plutons and frequent magmatic activities. To investigate the genetic relationship between magmatism and the mineralization of gold and silver polymetallic deposits in the area, this study focuses on the porphyritic monzogranite of the Liangwan pluton and the biotite granite of the Taoyuan pluton in detail. The zircon U‐Pb age of the Liangwan pluton is 128.5 ± 0.7 Ma, placing its intrusion age in the Early Cretaceous. Similarly, the zircon U‐Pb age of the Taoyuan pluton is 431.3 ± 2.7 Ma, indicating an intrusion age in the Early Silurian. Petrogeochemical analysis reveals that both the Liangwan and Taoyuan plutons exhibit high SiO2, Na2O and Al2O3 contents, along with low MgO, Fe2O3 and CaO contents, indicating a (high‐K) calc‐alkaline series, and have the properties of peraluminous I‐type granite. The total rare earth elements (REE) concentrations are low, with noticeable fractionation between light and heavy REE, and a negative Eu anomaly. High‐field‐strength elements (such as Nb, Ta, P, Ti) are depleted, while the large‐ion lithophile elements (such as Rb, K, Pb) are enriched. The εHf(t) values of the Liangwan and Taoyuan plutons range from −16.1 to −18.8 and from 11.0 to 14.6, respectively. The mean values of Hf two‐stage model ages (TDM2) are 603 Ma and 2230 Ma, respectively. These results suggest that the Liangwan pluton may have formed through partial melting of ancient crustal materials in the Palaeoproterozoic, during extensional tectonic events following the subduction of Izanagi Plate. It appears closely linked to Au‐Ag mineralization in the ore concentration area. The Taoyuan pluton likely originated from the depleted mantle and experienced some degree of crustal contamination. However, it is unrelated to regional mineralization.

Revisiting the deformation and migmatization of the Tongbai complex in the Tongbai orogenic belt, central China

Liu,

Zhang,

Huo

2024

The Tongbai complex plays an important role in the understanding of the tectonic evolution of the Tongbai‐Dabie orogenic belt. By detailed structural analysis, new zircon U–Pb dating, zircon Lu–Hf analysis and whole‐rock elements for the rocks in the Tongbai complex and the wrapped shear zones, we suggested that the Tongbai complex was derived from the partial melting of the basement of Yangtze Block and experienced a uniform orogen‐parallel extension with a top‐to‐NW shearing at 142–133 Ma. The migmatites yield a migmatization age of 116 ± 2 Ma and are identical to the metamorphic age of 115–111 Ma from the L and LS tectonites in the Tongbai complex. The late Early Cretaceous migmatization may give rise to the severance of the uniform top‐to‐NW shear zone and lead to an antiform folding of the Tongbai complex. The similar deformation and migmatization of the complexes in both the Tongbai and Dabie orogenic belts suggest that the Tongbai‐Dabie orogenic belt is likely to have a similar tectonic transformation from orogen‐parallel to orogen‐perpendicular extension in the Early Cretaceous, namely a uniform orogen‐parallel extension of the ductile lithosphere during the early Early Cretaceous and a widespread migmatization during the late Early Cretaceous.