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The Feidong Complex, located on the northeastern margin of the Yangtze Craton, exposes Precambrian basement rocks and is the subject of debate regarding its tectonic affinity. In this study, we conducted in situ U–Pb dating and Hf isotope analyses of zircons from basement rocks within the Feidong Complex. The results reveal crystallisation ages of ca. 2.45, 2.0 and 0.8 Ga for the granitic gneiss, amphibole biotite plagiogneiss and mylonitised monzonitic granite, respectively. The basement rocks with ages of ca. 2.45 and 2.0 Ga exhibit negative zircon εHf(t) values (−10.48 to −0.13) and older two‐stage model ages (TDM2 = 2974 to 3296 Ma). We compared the zircon U–Pb ages and Hf isotopic characteristics of the basement rocks from the Feidong Complex with those of the southern margin of the North China Craton and the northern margin of the Yangtze Craton. Additionally, we also compared the metamorphic grades of rocks between the Feidong Complex and Susong Complex of the Dabie orogenic belt. We found that the Feidong Complex and the northern margin of Yangtze Craton share comparable zircon U–Pb ages and Hf isotopic characteristics. However, the metamorphic grades of the Feidong Complex were distinct from those of the Susong Complex. In particular, the basement rocks with an age of ca. 2.45 Ga formed within a subduction setting; those with an age of ca. 2.0 Ga formed during the subduction and collision associated with the assembly of the Columbia supercontinent; and those with an age of ca. 0.8 Ga experienced extensional processes before the breakup of the Rodinia supercontinent. [ABSTRACT FROM AUTHOR]

A relatively complete trench–arc–basin system developed on the northern margin of the Proto-Tethys Ocean, and its subduction mode is key in reconstructing the tectonic evolution of the northern Proto-Tethyan margin. The Erlangping Group in the East Qinling Mountains is thought to be the product of subduction in the back-arc basin. Analysis of the metamorphism and deformation recorded by the group may elucidate the subduction mode of the back-arc basin. In this study, the tectonites in the southern and northern parts of Erlangping Group are taken as the research object, and their dynamic parameters such as geometry, kinematics and vorticity are determined by field observation and indoor tectonic deformation analysis. Deformed rocks in the northern part of the Erlangping Group are mainly feldspathic schists, primary mylonite, and mylonite, and the deformed rocks in the southern part of the Erlangping Group are mainly schists. The geometric characteristics of Erlangping group show that the foliation (30°–60°∠ 42°–70°) and dip lineation (5°–62°∠ 33°–51°) in the north of Erlangping group incline to NE, while the foliation (174°–234°∠ 50°–80°) and dip lineation (195°–230°∠ 45°–65°) in the South incline to SW; the kinematic characteristics show that both sides of Erlangping Group move under Qinling Group and Kuanping Group, respectively. Kinematic vorticity calculation shows that the vorticity values of the northern and southern parts of Erlangping Group are 0.79 and 0.78, respectively, both of which are more than 0.75, indicating that the shear type is dominated by simple shear and supplemented by pure shear. The average values of kinematic vorticity on the northern and southern parts of Erlangping Group are 0.78 and 0.79, respectively, both more than 0.75, indicating that subduction was dominated by simple shear, with minor pure shear deformation. The subduction deformation temperature range of Erlangping Group is estimated to be 380 ~ 500°C by the degree of quartz dynamic recrystallization. There is a positive correlation between the differential stress value σ (southern parts of Erlangping Group: 17.84–46.50; northern parts of Erlangping Group: 17.87–71.66) and strain rate ε (southern parts of Erlangping Group: 2.09 × 10–14 – 2.51 × 10–13; northern parts of Erlangping Group: 2.08 × 10–14 – 8.23 × 10–13) during subduction, while the grain size of dynamically recrystallized quartz is negatively correlated with strain rate. The specific performance is that in the northern part of Erlangping Group, from the Waxuezi–Qiaoduan shear zone to the Damiao–Dongjie shear zone, with the increase of the particle size of dynamically recrystallized quartz particles, the values of differential stress and strain rate gradually decrease, and have the same performance in the southern part of Erlangping Group. Through the above structural deformation analysis, combined with the previous research results on the material composition, sedimentary formation, magmatism, metamorphism and deformation of the Erlangping back-arc basin, it is considered that the Erlangping back-arc basin has the characteristics of bidirectional subduction during the late Palaeozoic subduction.* [ABSTRACT FROM AUTHOR]

Fault geometry, kinematics, geophysics, the tectonic stress field and tectonic evolution of the Zhouwang fault in the southern Jiangnan tectonic transition zone of the Lower Yangtze region, eastern China are examined. Field observations show the fault is composed of a series of nearly E–W trending, N–S dipping faults, and four stages of tectonism (sinistral strike‐slip, thrust nappe, normal fault, and dextral strike‐slip) developed in turn. Geophysical data show that the fault trends almost linearly E–W along a flat, steep gravity gradient at shallow depth, with distinct gravity anomalies to the north and south and different in the north and south. Also, the deep part is characterized by northward dip and a gradual slowing down. Tectonic stress field analysis indicates that the fault experienced four tectonic movements: NNE–SSW compression, NNW–SSE compression, NEE–SWW extension, and E–W compression. Combined with regional tectonic background and previous research results, this indicates that: (1) the Zhouwang fault experienced sinistral strike‐slip movement during the Indosinian Period (260–200 Ma); (2) thrust nappes developed during the early Yanshanian Period (163–145 Ma); (3) a normal fault occurred in the late Yanshanian Period (125–65 Ma); and (4) dextral strike‐slip movement occurred in the Himalayan Period (ca. 50–37 Ma). The results reveal the tectonic evolution of the fault during Mesozoic deformation in the area, and also reveal the geological evolution and tectonic transformation of the Lower Yangtze region, which is key to our understanding of intracontinental deformation in eastern China. [ABSTRACT FROM AUTHOR]

Late Mesozoic magmatic rocks of the Zhangbaling Uplift (ZBU) in eastern China, which comprises the northern Zhangbaling area and the southern Feidong area, can provide insights into the deep crustal processes and tectonic affinity of the massif. These rocks are dominated by granitoids with formation ages of 132–120 Ma and a peak at 129 Ma. The Shankouling dyke (120.4 ± 1.1 Ma) and the Zhuyuanzhang quartz monzodiorite (129.0 ± 2.2 Ma) crop out sporadically in the Feidong area. These rocks show adakitic signatures of high Al2O3 and Sr contents, high Sr/Y, (La/Yb)N, and (Dy/Yb)N ratios, and low Y and YbN contents. They have enriched (87Sr/86Sr)i ratios, negative εNd(t) and εHf(t) values, and unradiogenic Pb isotopic compositions that resemble those of coeval high Sr/Y granitoids in the Dabie Orogen. These ZBU rocks can be divided into two groups: low-Mg granitoids with more enriched Sr–Nd isotopic signatures and low Mg# values (<50), and high-Mg granitoids with weakly enriched Sr–Nd isotopic signatures and high Mg# values (mostly >50). Combining their geochemical features with previous results of experimental melts, we conclude that the low-Mg granitoids were derived from fluid-absent partial melting of in situ thickened lower continental crust, resulted from Triassic continental subduction and collision in this area, whereas the high-Mg granitoids were derived from delaminated eclogitic lower crust followed by interaction with mantle peridotites during magma ascent. Isotopic compositions show that these granitoids could have been derived from ancient crust of the Yangtze Block via re-melting of Neoarchean and Paleoproterozoic lower continental crust. The great depth of the Tan–Lu Fault Zone enabled delamination of the thickened eclogitic mountain root beneath the ZBU, which resulted in the formation and emplacement of the high-Mg rocks, followed by uplift of the Zhangbaling massif associated with rollback of the subducting Paleo-Pacific (Izanagi) Plate. [ABSTRACT FROM AUTHOR]

The Qinling orogen is a key area for understanding the processes of subduction and collision between the South China Block (SCB) and North China Block (NCB). The Wuguan Complex, distributed along the southern margin of the Shangdan suture zone, can provide important constraints on the age of collision between NCB and SCB and the tectonic evolution of the Qinling orogen in Late Paleozoic. Detrital zircons from meta-sedimentary rocks of the Wuguan Complex in the Danfeng-Shangnan area have an age spectrum with two main peaks at ~448 Ma and ~819 Ma, and two subordinate peaks at ~938 and ~1440 Ma, respectively, and are interpreted to have been derived from the North Qinling terrane (NQT). The petrographic and geochemical characteristics of the meta-sedimentary rocks indicate that they were deposited in a fore-arc basin along the southern margin of the NQT. The youngest detrital zircons yield a weighted mean age of 378 ± 3 Ma, indicating that the fore-arc deposition was continuing at least to this time, which implies that the Paleo-Qinling Ocean between the NCB and SCB was not finally closed until at least the late Devonian. In combination with regional data, we propose that sedimentary rocks of the Wuguan Complex might once have been a sequence of late Ordovician to late Devonian strata with intercalated mafic rocks, which has been dismembered by the later tectonic activity. It was metamorphosed during northward subduction of the Paleo-Qinling Ocean at ca. 320 Ma, and slowly cooled through ca. 350°C at ca. 247 Ma (muscovite 40Ar/39Ar age). It has recorded the detailed processes of subduction and collision between the NCB and SCB. [ABSTRACT FROM AUTHOR]

The Jiulianshan anticlinorium is located at the southern part of the Mount Maoshan–Jiulianshan in the Lower Yangtze region, where a number of new‐found thrust faults were identified. Movement of these thrust faults had resulted in Palaeozoic strata lying unconformably above Cretaceous strata. However, the Lower Yangtze region was mostly under an extensional tectonic regime during the Late Mesozoic, which is inconsistent with existence of the nappe in the Mount Maoshan–Jiulianshan. Therefore, what the structural characteristics are and when these thrust faults developed are important for understanding the evolution of the South China Block. Based on detailed field observations, these new‐found thrust faults outcropped in the Liqiao, Yangxian, and Miaopu areas. These faults, SE‐dipping deeply, developed a meters‐wide fault‐and‐fracture zone of width in meters. The footwall was composed of the Early Cretaceous pyroclastic rock or tuff, which indicates that these faults developed since the Early Cretaceous. Two undeformed dykes formed in the fault‐and‐fracture zone of Miaopu area and a footless intrusion in the hanging wall, which give emplacement ages of ca. 132 Ma by using zircon U–Pb LA‐ICP‐MS dating and thus implies that thrust fault motion occurred prior to or around this time. The volcanic tuff and pyroclastic rocks, located in the footwall of the Yangxian and Miaopu thrust fault, are dated at ca. 137 and 134 Ma, respectively, indicating that fault motion must have occurred after this time. The Qiaotouyang pluton emplaced in the core of one of the folds in the fold‐and‐thrust belt at ca. 141 Ma, which indicates that the fold‐and‐thrust belt of Tongling Uplift formed prior to 141 Ma. Integrating other evidences, such as magmatic quiescence, large‐scale and short‐duration volcanic eruptions, and beginning time of metamorphic core complex and rift basin, it is inferred that Early Yanshanian thrust faults were reactivated during the Late Mesozoic, resulting in thrusting within the Jiulianshan anticlinorium. [ABSTRACT FROM AUTHOR]

The Tongbai orogenic belt has an overall antiformal geometry and the hinge of the antiform is sub-horizontal and trends NW–SE. The Tongbai complex (TBC) in the core of the antiform is bounded by the S-dipping Yindian–Malong shear zone in the south, the sub-horizontal Taibaiding shear zone at the top and the N-dipping Hongyihe–Tongbai shear zone in the north. The three shear zones have dextral, top-to-NW and sinistral movement, respectively. They are parts of a single shear zone, termed the Tongbai shear zone, that has a uniform top-to-NW sense of shear. Three samples of deformed granitoid (mylonite or protomylonite) from the shear zone have U–Pb zircon ages of 145 ± 6 Ma, 142 ± 2 Ma and 131 ± 6 Ma, respectively. An L-tectonite in the TBC yielded a metamorphic age of 137 ± 8 Ma and a migmatite an age of 137 ± 1 Ma. The Tongbai shear zone is intruded by undeformed Early Cretaceous granite and dykes and deformation in the shear zone is constrained to ca. 140–135 Ma, synchronous with metamorphism and migmatization in the TBC. Early Cretaceous magma emplacement and the associated uplift modified the TBC into a gentle antiform and the uplift may have continued to ca. 102–85 Ma. Similar geometry and kinematics have been documented in the Dabie orogenic belt to the east, which suggests that the Central Orogenic Belt in China probably experienced a uniform orogen-parallel extension and top-to-NW shearing in the ductile lithosphere in the Early Cretaceous. [ABSTRACT FROM PUBLISHER]

Samples of mylonite, ultramylonite and phyllonite were collected from 5 localities in the Anhui part of the Tan-Lu fault zone for40Ar/39Ar chronological studies. Among them 4 samples from 3 localities on the eastern margin of the Dabie orogenic belt yielded40Ar/39Ar plateau ages of 128 —132 Ma; and 2 samples from the western margin of the Zhangbalin uplift and eastern margin of the Bengbu uplift gave the same40Ar/39Ar plateau ages of 120 Ma. Isochron analyses and other lines of evidence suggest that the data are reliable. The data are interpreted as cooling ages of sinistral strike-slip deformation of the Tan-Lu fault zone. The younger ages from the north might be related to slower strike-slip rising. These results indicate that the large-scale left-lateral displacement in the Tan-Lu fault zone took place in the Early Cretaceous, rather than in Late Triassic (Indosinian) as proposed by some geologists. Therefore, this fault zone is an intracontinental wrench fault rather than a transform fault or suture line developed during formation of the Dabie orogenic belt. [ABSTRACT FROM AUTHOR]