Detrital provenance analysis is an effective way to understand paleogeographic change and geodynamics. In this paper, we present petrological, whole-rock geochemical and detrital zircon U–Pb ...geochronological analysis of Early and Middle Jurassic terrestrial clastic rocks in the Jingdezhen Basin and the Huangshan Basin in the Jiangnan domain, South China. Petrology and whole-rock geochemistry show that the source rocks are dominated by intermediate to acid component. The Chemical Index of Alteration ranges from 69 to 86, suggesting a moderate weathering history for the source rocks. The Early–Middle Jurassic sediments in the Jingdezhen and Huangshan basins were mostly sourced from magmatogenic greywackes and felsic magmatic rocks, respectively. Detrital zircons have seven age peaks at ~240Ma, ~430Ma, ~1390Ma, ~1880Ma, ~2500Ma, –3200Ma and 788–999Ma (a wide peak). Provenance analysis indicates that the source rocks are in the Jiangnan domain, the Northwest Zhejiang Basin and the Wuyishan domain. Combining these with previous results and paleocurrent directions, we infer that the NE-trending Wuyishan and Xuefengshan domains and the nearly E–W-Jiangnan domain and Nanling tectonic belt were orogenic uplifts and watersheds during the Late Triassic to Middle Jurassic. The Early Mesozoic geodynamics in the South China Block was related to the westward subduction of the Paleo-Pacific Plate and the northward continent–continent collision following the closure of the Paleo-Tethys Ocean.
•Detrital provenance analysis is conducted for J1–J2 Huangshan and Jingdezhen basins.•Source rocks are in Northwest Zhejiang Basin, Jiangnan and and Wuyishan domains.•NE- and E- orogenic uplifts occurred during Late Triassic to Middle Jurassic.•T3–J2 geodynamics in SCB was Paleo-Pacific subduction and Paleo-Tethys closure.
Emulsion gels with low oil contents have been continuously developed in recent decades. In this study, the use of high-intensity ultrasound for the preparation of low oil emulsion gel (oil fraction ...of 0.25) was investigated. Specifically, defatted Antarctic krill protein (dAKP) was used to stabilize the interface of soybean oil and water. Then, the microstructure and the stabilization mechanism of the formed emulsion gel were evaluated by cryo-SEM, CLSM, zeta potential, rheological measurements, and FTIR. Besides, the particle diameter was measured to be around 5 μm. The results of CLSM indicated that the emulsion gel was the oil-in-water type. The emulsion gel exhibited gel-like viscoelastic behavior even at a low concentration of dAKP due to the formation of a rigid particle network while the rheological behavior of the emulsion gel was significantly affected by the concentration of dAKP. The stabilization of the emulsion gel can be maintained by space steric hindrance and hydrophobic interactions between particles in the emulsion gel system.
The late Mesozoic to Cenozoic tectonothermal history of the basin-and-range system within the Cathaysia Block in the southeastern South China Block remains poorly constrained, despite its ...significance in the tectonic and topographic evolution of eastern China. Zircon and apatite fission-track thermochronometers were applied to reconstruct the cooling histories of NE-trending mountain ranges mantled by late Mesozoic granites and older basement rocks in southwest Fujian. New zircon and apatite fission-track data record post-magmatic cooling of the sampled granites since their emplacement of ~164–118 Ma. Thermal modeling of the thermochronology data revealed two episodes of accelerated cooling events at ~110–85 Ma and ~40–25 Ma. The late Early Cretaceous initiation of an accelerated cooling event at rates of ~6 °C/Ma was considered to be the cause of the formation of the basin-and-range system in a back-arc extensional setting related to the rollback of the Paleo-Pacific Plate. The second cooling event at ~40–25 Ma at a rate of ~20 °C/Ma, reflected by the youngest apatite fission track ages (~25–20 Ma), was likely ascribed to headwater erosion along the drainage divide related to the intensification of the East Asian Monsoon and extensional tectonism. The sharp discrepancy in apatite fission track ages across the Zhenghe-Dapu Fault zone implies that the collapse of the late Mesozoic coastal magmatic arc in the early Eocene (51.4–45.6 Ma). This is attributed to the northward propagation of extension related to the rollback of the Paleo-Pacific Plate that formed the eastward-dipping topography. Furthermore, the long-lasting extension due to the rollback of the Pacific Plate since the ridge subduction of the Izanagi-Pacific at ~50 Ma likely drove the exhumation of the Cathaysia Block and opening of the South China Sea.
•Cooling and exhumation histories of the SE South China have been reconstructed by new zircon and apatite fission track data.•Two episodes of accelerated cooling during 110–85 Ma and 40–25 Ma are identified.•Middle-late Cretaceous accelerated cooling reflected the formation of the basin-and-range system in a back-arc setting.•Eocene-Oligocene accelerated cooling was interpreted to record both tectonic and climate influences on the the topography.
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•Dengfuxian and Wufengxian 227 Ma granites were formed in a syn-collision setting.•Dengfuxian and Xitian 152 Ma granites were formed in a post-orogenic setting.•Paleo-Tethys tectonic ...regimes affected the South China Block during the Triassic.•Paleo-Pacific tectonic regimes affected the South China Block during the Jurassic.•Tectonic regime transformation occurred during the Late Triassic to Early Jurassic.
The Early Mesozoic tectonic transition from the Palaeo-Tethys to Palaeo-Pacific tectonic regimes in the South China Block has long been a matter of debate. Zircon U–Pb dating, and whole-rock elemental and Sr–Nd–Hf isotoic analyses were conducted for the Early Mesozoic Dengfuxian, Xitian, and Wufengxian plutons to investigate their petrogenesis and the implications for the tectonic transition of the South China Block. These plutons were emplaced in two stages: 1) Late Triassic (227–226 Ma) Dengfuxian and Wufengxian monzogranite and 2) Late Jurassic (152–151 Ma) Dengfuxian and Xitian alkaligranites. Monzogranites are characterized by decrease in P2O5 contents when SiO2 contents increasing, low A/CNK (molar Al2O3/(CaO + Na2O + K2O)) indexes, high K2O contents and Mg# (molar 100 × Mg/(Mg + Fe)) values, and they belong to high-K calc-alkaline to shoshonite I-type granites. They have negative εNd(t) (−10.2 to −9.0) and εHf(t) (−20.6 to −4.4) values with old, two-stage crustal Nd–Hf isotopic model ages (1.40–2.68 Ga) and high zircon saturation temperatures (896 °C–861 °C), indicating that the monzogranites were derived from the partial melting of Mesoproterozoic meta-basaltic rocks. Alkaligranites are characterised by high A/CNK values, Fe# (FeOT/(FeOT + MgO)) indexes and low Al2O3 and CaO contents, and Mg#, and they belong to A-type granites. They have negative εNd(t) (−7.1 and −5.5) and εHf(t) (−8.5 to −4.7) values with old, two-stage crustal Nd–Hf isotopic model ages (1.20–1.49 Ga), low zircon saturation temperatures (799 °C–830 °C) and geochemical features, indicating that they were produced by the partial melting of Neoproterozoic meta-sedimentary rocks. Combined with previous results, we suggest that the Late Triassic monzogranites formed in a syn-collision environment related to the collision of the continental plates in the Palaeo-Tethys oceans, whereas the Late Jurassic syenogranites formed in a post-orogenic environment in the South China Block resulting from the rollback of the Palaeo-Pacific Plate. The tectonic transition from the Palaeo-Tethys to Palaeo-Pacific tectonic regimes in the South China Block could have occurred between the Late Triassic and Early Jurassic.
The Dabashan arcuate structures are composed of the NW-striking Northern Dabashan Belt belonging to the southern margin of the South Qinling Orogen and the curved Southern Dabashan Belt located in ...the northern margin of the Yangtze Block with the arcuate Chengkou-Fangxiang Fault as their boundary. The deep understanding of the orogenesis is indispensable to unravel the mechanism of the Dabashan arcuate structures, as the basement preserves important clues on the deformational characteristics as well as the timing and orogenic processes. Here we report integrated field investigation, structural analysis, and 40Ar/39Ar thermochronological data in the Wudang and Ankang Uplifts in the South Qinling Orogen to decipher the forming processes and mechanisms of the Dabashan arcuate structures. The field and microscopic observations reveal a dominantly top-to-south (southwest) shear sense at low to medium temperatures. The basement deformation expanded southward (southwestward) in the form of duplex. During the continued shortening, the basement was uplifted due to thrust stacking within duplex systems. According to the deformation temperatures, and the new and published 40Ar/39Ar thermochronological data, the basement recorded the ca. 248-212 Ma orogenesis for the Wudang Uplift and the ca. 222-161 Ma orogenesis for the Ankang Uplift. Based on the tectonic evolution of the study area, the formation of composite Dabashan arcuate structures included three stages. Firstly, the arcuate master fault accompanied by a series of NW-striking faults came into being at ca. 450-400 Ma based on previous studies. Secondly, the scissor-like convergence between the South China Block and North China Block reactivated the extensional structures and formed the general features of the Northern Dabashan Belt at ca. 250-160 Ma. Finally, the deformation expanded toward the foreland and formed the curved Southern Dabashan Belt with obstruction by the Hannan Uplift and Shennongjia-Huangling Uplift in the front at ca. 160-100 Ma.
•Deformation with top-to-south (southwest) shear sense at low-medium temperatures.•248–212 Ma and 222–161 Ma deformation respectively for Wudang and Ankang uplifts.•Deformation expanded southward (southwestward) in the form of duplex.•Three stages include faulting, reactivation and formation of foreland curvature.
Multi-plate convergence around a nuclear block and the geodynamic transition occurred generally after the onset of plate tectonics. Late Triassic to Middle Jurassic geodynamics of the South China ...Block has been under hot debate. Late Triassic to Middle Jurassic basins and provenance, magmatism and geochemistry, structural deformation and geochronology were reevaluated and a geodynamic model was proposed for the South China Block. Late Triassic to Early Jurassic peripheral foreland basins and retro-arc foreland basins occurred along the western and northern margins and the southeastern margin, respectively. Sandstone components, paleocurrent directions and detrital zircon UPb ages indicate that clastic rocks in these foreland basins were derived mainly from adjacent Indosinian orogens around the South China Block. Late Triassic to Middle Jurassic magmatism in the South China Block mainly includes weakly to strongly peraluminous granites. Both NW-SE and NE-SW granitic sections show that Late Triassic granites have high whole rock (87Sr/86Sr)i ratios, accumulational whole rock ε Nd (t) values and the same sources of global sediments whereas Early and Middle Jurassic granites have low whole rock (87Sr/86Sr)i ratios, dispersive whole rock ε Nd (t) values and different sources of global sediments and ocean island basalts. But all granites have similar zircon ε Hf (t) values and TDM2 ages. Late Triassic and Middle Jurassic granites occurred in a syn-collisional environment whereas Early granites along the southeastern margin in a volcanic arc setting or Early granites along the E-W Nanling granitic belt in a within-plate setting. NE-SW and NW-SE structural sections present NW-striking folds and thrust faults and NNE-striking folds, thrust faults and ductile strike-slip shearing, respectively. The NNE-striking structures show younger from SE to NW direction whereas NW-striking folds and thrusts along the southern and northern margins occurred synchronously. The NW-striking folds and thrust faults were superimposed by the NNE-striking folds and thrust faults. Lines of evidence indicate that the Paleo-Tethys and Paleo-Pacific tectonic regimes co-existed in the South China Block during Late Triassic to Early Jurassic and the geodynamic transition from the Paleo-Tethys to Paleo-Pacific tectonic regimes was completed during Middle Jurassic.
► Multiple episodes of igneous events are discerned in the coastal Changle-Nan’ao zone, SE China. ► The T3–J sediments were deformed and metamorphosed in the Late Mesozoic orogeny (ca. 165–135Ma). ► ...The migmatization and syn-kinematic magmatism were active at 147–136Ma. ► Post-kinematic magmatic rocks were emplaced at 132–117Ma. ► The transition from syn-orogenic compression to post-orogenic extension occurred at 136–132Ma.
The coastal Changle-Nan’ao tectonic zone of SE China contains important geological records of the Late Mesozoic orogeny and post-orogenic extension in this part of the Asian continent. The folded and metamorphosed T3–J1 sedimentary rocks are unconformably overlain by Early Cretaceous volcanic rocks or occur as amphibolite facies enclaves in late Jurassic to early Cretaceous gneissic granites. Moreover, all the metamorphic and/or deformed rocks are intruded by Cretaceous fine-grained granitic plutons or dykes. In order to understand the orogenic development, we undertook a comprehensive zircon U–Pb geochronology on a variety of rock types, including paragneiss, migmatitic gneiss, gneissic granite, leucogranite, and fine-grained granitoids. Zircon U–Pb dating on gneissic granites, migmatitic gneisses, and leucogranite dyke yielded a similar age range of 147–135Ma. Meanwhile, protoliths of some gneissic granites and migmatitic gneisses are found to be late Jurassic magmatic rocks (ca. 165–150Ma). The little deformed and unmetamorphosed Cretaceous plutons or dykes were dated at 132–117Ma. These new age data indicate that the orogeny lasted from late Jurassic (ca. 165Ma) to early Cretaceous (ca. 135Ma). The tectonic transition from the syn-kinematic magmatism and migmatization (147–136Ma) to the post-kinematic plutonism (132–117Ma) occurred at 136–132Ma.
The Jiangnan Orogen in the South China Block collapsed rapidly after the Neoproterozoic assembly of the Yangtze and Cathaysia blocks. Extensional collapse of orogens is generally triggered by ...post-orogenic extension and/or continental rifting. Detrital zircon U-Pb geochronology and trace elements geochemistry was conducted on sedimentary rocks across the Neoproterozoic angular unconformity in the Northwestern Zhejiang Basin. Detrital zircon U-Pb ages indicate that the Chentangwu Formation (upper Pingshui Group) and the Heshangzhen Group were deposited from 840 to 820 Ma and 810-780 Ma, respectively. The Trace elements geochemistry of early Neoproterozoic detrital zircons suggests that the source rocks of the Chentangwu Formation were derived from continental arcs and oceanic islands whereas those of the Heshangzhen Group (the Luojiamen and the Hongchicun formations) were likely related to continental arcs, oceanic islands and mid-oceanic ridges. This study reveals that the Chentangwu Formation was probably deposited in a Neoproterozoic back-arc basin which was filled by sediments from the Cathaysia Block, the Shuangxiwu Arc, and the Jiangnan Orogen. The source regions of the Hongchicun formations outcrops in the eastern and western Northwestern Zhejiang Basin are the Cathaysia Block and the Jiangnan Orogen, respectively. However, the Shangshu Formation in the west has the same source regions as the underlying Hongchicun Formation in the east. The variations in thickness and source rocks exhibited by the Hongchicun formations in the west and east are controlled by normal faulting along the Dexing-Huangshan fault zone, which is the western boundary fault of the Northwestern Zhejiang Basin. The growth fault resulted in the formation of a ridged rollover anticline in the middle of the Northwestern Zhejiang Basin and prevented ∼810 Ma zircons from being transported to the west during deposition of the Hongchicun Formation. Comprehensive analysis reveals that the extensional collapse of the Jiangnan Orogen resulted from 810 to 780 Ma post-orogenic extension.
•Chentangwu Formation was deposited in a 840-820 Ma back-arc basin.•Heshangzhen Group was deposited in a 810-780 Ma post-orogenic basin.•Provenances of Chentangwu Fr. are continental arcs and oceanic islands.•Provenances of Heshangzhen Gr. are continental arcs, oceanic islands and mid-oceanic ridges.•Different thickness and provenance of Hongchicun Fr. were dominated by growth fault.
The Neoproterozoic Xikou Group is unconformably overlain by the Heshangzhen Group in the eastern Jiangnan orogen, South China. Samples from the Xikou and Heshangzhen Groups have generally ...intermediate to high SiO2 (53.14–77.48wt.%, average 65.33wt.%) and Al2O3 (11.53–27.14wt.%, average 18.96wt.%) contents, typical of immature lithic varieties. Compared to the Xikou Group, the Heshangzhen Group has higher Al2O3 (average 21.19wt.% for the Heshangzhen Group and 18.33wt.% for the Xikou Group, respectively) and Fe2O3*+MgO (average 9.38wt.% and 8.86wt.%) contents, but lower SiO2 (average 59.79wt.% and 66.91wt.%) content, suggesting that the Heshangzhen Group has more mafic components. The Chemical Index of Alteration (69–81) and the high Th/U ratios (>3.8) indicate moderate weathering of the source area. Rare earth element patterns suggest that the source rocks came from an upper continental crust composed chiefly of felsic rocks. Discrimination diagrams reveal a mixed provenance of granitic and felsic volcanic components with minor old sedimentary component.
Detrital zircon U–Pb ages and previous geochronological data of granitic plutons indicate that the Xikou and Heshangzhen Groups were deposited at 840–820Ma and 810–780Ma, respectively. The Xikou Group was deposited in a back–arc basin and its source rocks came mainly from the Yangtze Block. The Heshangzhen Group formed in a post-orogenic setting with a provenance of the Yangtze Block and the Shuangxiwu arc. The Jiangnan orogen was built at 820–810Ma after the final suturing between the Yangtze and the Cathaysia Blocks. This orogen collapsed shortly following the collision (within 10–20million years) and formed the Dexing–Huangshan normal fault zone.
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•Xikou Group was deposited in a back-arc basin at 840~820Ma.•Heshangzhen Group was deposited at 810~780Ma due to the post-orogenic extension.•The final suturing of the Yangtze and Cathaysia Blocks occurred at 820~810Ma.
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