Seismic evidence for the subduction of North China Block to Yangtze Block beneath Tongbai-Dabie Orogenic belt

2020 ◽  
Author(s):  
Hongwei Zheng
Keyword(s):  
Upper Mantle ◽  
High Velocity ◽  
North China ◽  
Orogenic Belt ◽  
Late Triassic ◽  
Yangtze Block ◽  
North China Block ◽  
Crust And Upper Mantle ◽  
Dabie Orogenic Belt ◽  
Velocity Anomalies

<p>The Tongbai-Dabie Orogenic belt formed in the Middle-to-Late Triassic through a collision between the Yangtze Block (YB) and North China Block (NCB) and is a key component of the Central Orogen of China, which is famous on the most extensive high and ultrahigh pressure (HP/UHP) metamorphic zone in the world and marks the irregular suture between the YB and NCB. It is an ideal place to study the ancient orogenic processes between collided continents. In this study, we used a large number of P-wave arrival times recorded by portable and permanent seismic stations to reveal the structure of the crust and upper mantle beneath the Tongbai-Dabie orogenic belt and its adjacent region. Our images show the south-dipping high-velocity anomalies beneath the Tongbai-Dabie orogenic belt and the east-dipping high-velocity anomalies beneath the Tanlu Fault, which represent the southeastward subducted NCB in Mesozoic. While a huge high-velocity anomaly beneath the Wudang Moutin region extending down to 250 km is possible the ancient lithosphere of the Yangtze Craton remnant since the Paleoproterozoic. The northward subducted YB is only limited in the Eastern Dabie terrane and Yangtze foreland. Break-off retained Paleo-Tethyan oceanic slab are revealed at depths from the upper mantle 250 to 400 km. The structure of the crust and upper mantle suggests that the southeastward subduction of NCB resulted in the collision of NCB with YB.</p>

Regional lithospheric deformation beneath the East Qinling-Dabie orogenic belt based on ambient noise tomography

2021 ◽  
Author(s):  
Yu Wei ◽  
Shuangxi Zhang ◽  
Mengkui Li ◽  
Tengfei Wu ◽  
Yujin Hua ◽  
...  
Keyword(s):  
High Velocity ◽  
Lithospheric Mantle ◽  
Lower Crust ◽  
North China ◽  
3D Model ◽  
Orogenic Belt ◽  
Yangtze Block ◽  
North China Block ◽  
The North ◽  
Dabie Orogenic Belt

Summary The Qinling–Dabie orogenic belt, which contain the arc-shaped Dabbashan orocline and is the world's largest belt of HP/UHP metamorphic rocks, formed by a long-term complex amalgamation process between the North China Block and the Yangtze Block. To understand the collision processes and tectonic evolution, we constructed a three-dimensional (3D) S-wave velocity model from the surface to a depth of ∼120 km in the eastern Qinling-Dabie orogenic belt and its adjacent region by inverting 5–70 s phase velocity dispersion data of Rayleigh waves extracted from ambient noise data. Our 3D model reveals low velocities in the middle–lower crust and high velocities in the upper mantle beneath the orogenic belt, suggesting the delamination of the lower crust. Our results support a two-stage exhumation model for the HP/UHP rocks in the study area. First-stage exhumation was caused by the slab breaking away from the subducted Yangtze Block during the Early–Middle Triassic. Partial melting of the lithospheric mantle caused by slab breakoff–related asthenospheric upwelling weakened the lithospheric mantle beneath the orogenic belt, and continued convergence of the two continental blocks led to further thickening of the lower crust. Such processes promoted lower-crust delamination, which triggered the second-stage exhumation of the HP/UHP rocks. In the Dabbashan orocline, two deep-rooted high-velocity domes, that is, Hannan–Micang and Shennong–Huangling domes, acted as a pair of indenters during the formation stage. High-velocity lower crust was observed beneath the Dabbashan orocline. In addition, our 3D model reveals that high-velocity lithospheric mantle extends from the Sichuan Basin to the Dabbashan orocline, with a subhorizontal distribution, providing strong support for the high-velocity lower crust. We also observed the destruction of lithospheric mantle beneath the Yangtze Block; the destruction area is bounded by the North–South Gravity Lineament, suggesting that the destruction mechanism of the Yangtze Block may be similar to the North China Block.

Crust-mantle velocity structure in Shanxi rift, Central North China Craton

2020 ◽  
Author(s):  
Yan Cai ◽  
Jianping Wu
Keyword(s):  
Upper Mantle ◽  
High Velocity ◽  
North China Craton ◽  
Lower Crust ◽  
North China ◽  
Velocity Structure ◽  
Low Velocity ◽  
Crust And Upper Mantle ◽  
The North ◽  
Shanxi Rift

<p>North China Craton is the oldest craton in the world. It contains the eastern, central and western part. Shanxi rift and Taihang mountain contribute the central part. With strong tectonic deformation and intense seismic activity, its crust-mantle deformation and deep structure have always been highly concerned. In recent years, China Earthquake Administration has deployed a dense temporary seismic array in North China. With the permanent and temporary stations, we obtained the crust-mantle S-wave velocity structure in the central North China Craton by using the joint inversion of receiver function and surface wave dispersion. The results show that the crustal thickness is thick in the north of the Shanxi rift (42km) and thin in the south (35km). Datong basin, located in the north of the rift, exhibits large-scale low-velocity anomalies in the middle-lower crust and upper mantle; the Taiyuan basin and Linfen basin, located in the central part, have high velocities in the lower crust and upper mantle; the Yuncheng basin, in the southern part, has low velocities in the lower crust and upper mantle velocities, but has a high-velocity layer below 80 km. We speculate that an upwelling channel beneath the west of the Datong basin caused the low velocity anomalies there. In the central part of the Shanxi rift, magmatic bottom intrusion occurred before the tension rifting, so that the heated lithosphere has enough time to cool down to form high velocity. Its current lithosphere with high temperature may indicate the future deformation and damage. There may be a hot lithospheric uplift in the south of the Shanxi rift, heating the crust and the lithospheric mantle. The high-velocity layer in its upper mantle suggests that the bottom of the lithosphere after the intrusion of the magma began to cool down.</p>

scholarly journals New insights on the early Mesozoic evolution of multiple tectonic regimes in the northeastern North China Craton from the detrital zircon provenance of sedimentary strata

Solid Earth ◽  
2018 ◽  
Vol 9 (6) ◽  
pp. 1375-1397 ◽  
Author(s):  
Yi Ni Wang ◽  
Wen Liang Xu ◽  
Feng Wang ◽  
Xiao Bo Li
Keyword(s):  
North China Craton ◽  
North China ◽  
Early Jurassic ◽  
Orogenic Belt ◽  
Detrital Zircons ◽  
Late Triassic ◽  
Early Triassic ◽  
The South ◽  
The North ◽  
Early Mesozoic

Abstract. To investigate the timing of deposition and provenance of early Mesozoic strata in the northeastern North China Craton (NCC) and to understand the early Mesozoic paleotectonic evolution of the region, we combine stratigraphy, U–Pb zircon geochronology, and Hf isotopic analyses. Early Mesozoic strata include the Early Triassic Heisonggou, Late Triassic Changbai and Xiaoyingzi, and Early Jurassic Yihe formations. Detrital zircons in the Heisonggou Formation yield  ∼ 58 % Neoarchean to Paleoproterozoic ages and  ∼ 42 % Phanerozoic ages and were sourced from areas to the south and north of the basins within the NCC, respectively. This indicates that Early Triassic deposition was controlled primarily by the southward subduction of the Paleo-Asian oceanic plate beneath the NCC and collision between the NCC and the Yangtze Craton (YC). Approximately 88 % of the sediments within the Late Triassic Xiaoyingzi Formation were sourced from the NCC to the south, with the remaining  ∼ 12 % from the Xing'an–Mongolia Orogenic Belt (XMOB) to the north. This implies that Late Triassic deposition was related to the final closure of the Paleo-Asian Ocean during the Middle Triassic and the rapid exhumation of the Su–Lu Orogenic Belt between the NCC and YC. In contrast,  ∼ 88 % of sediments within the Early Jurassic Yihe Formation were sourced from the XMOB to the north, with the remaining  ∼ 12 % from the NCC to the south. We therefore infer that rapid uplift of the XMOB and the onset of the subduction of the Paleo-Pacific Plate beneath Eurasia occurred in the Early Jurassic.

scholarly journals Supplemental Material: Late Triassic successive amalgamation between the South China and North China blocks: Insights from structural analysis and magnetic fabrics study of the Bikou Terrane and its adjacent area, northwestern Yangtze block, central China

2021 ◽  
Author(s):  
Zhenhua Xue ◽  
Wei Lin ◽  
et al.
Keyword(s):  
North China ◽  
Stereographic Projection ◽  
Magnetic Hysteresis ◽  
Central China ◽  
Late Triassic ◽  
Adjacent Area ◽  
Yangtze Block ◽  
Data Set ◽  
Basic Principles ◽  
Magnetic Fabrics

Text: Basic principles of anisotropy of magnetic susceptibility (AMS); Figure S1: Photographs of supplementary shearing indicators of the structural kinematics; Figure S2: Complete magnetic hysteresis data set for specimen selected from 34 sites; Figure S3: Measurements of isothermal remanent magnetization of specimen selected from 34 representative sites of the Bikou Terrane; Figure S4: Thermo-magnetic experiments of specimen selected from 12 representative sites; Figure S5: Mrs/Ms versus Hcr/Hc diagram from the selected specimen of the representative sites to define the size of magnetite; Figure S6: Stereographic projection of the AMS directional fabrics and structural fabrics.

The upper mantle beneath the South Atlantic Ocean, South America and Africa from waveform tomography with massive data sets

2020 ◽  
Vol 221 (1) ◽  
pp. 178-204 ◽  
Author(s):  
N L Celli ◽  
S Lebedev ◽  
A J Schaeffer ◽  
M Ravenna ◽  
C Gaina
Keyword(s):  
South America ◽  
Upper Mantle ◽  
High Velocity ◽  
South Atlantic ◽  
The South ◽  
Low Velocity ◽  
The West ◽  
Velocity Anomaly ◽  
Archean Crust ◽  
Velocity Anomalies

SUMMARY We present a tomographic model of the crust, upper mantle and transition zone beneath the South Atlantic, South America and Africa. Taking advantage of the recent growth in broadband data sampling, we compute the model using waveform fits of over 1.2 million vertical-component seismograms, obtained with the automated multimode inversion of surface, S and multiple S waves. Each waveform provides a set of linear equations constraining perturbations with respect to a 3-D reference model within an approximate sensitivity volume. We then combine all equations into a large linear system and solve it for a 3-D model of S- and P-wave speeds and azimuthal anisotropy within the crust, upper mantle and uppermost lower mantle. In South America and Africa, our new model SA2019 reveals detailed structure of the lithosphere, with structure of the cratons within the continents much more complex than seen previously. In South America, lower seismic velocities underneath the transbrasilian lineament (TBL) separate the high-velocity anomalies beneath the Amazon Craton from those beneath the São Francisco and Paraná Cratons. We image the buried portions of the Amazon Craton, the thick cratonic lithosphere of the Paraná and Parnaíba Basins and an apparently cratonic block wedged between western Guyana and the slab to the west of it, unexposed at the surface. Thick cratonic lithosphere is absent under the Archean crust of the São Luis, Luis Álves and Rio de La Plata Cratons, next to the continental margin. The Guyana Highlands are underlain by low velocities, indicating hot asthenosphere. In the transition zone, we map the subduction of the Nazca Plate and the Chile Rise under Patagonia. Cratonic lithosphere beneath Africa is more fragmented than seen previously, with separate cratonic units observed within the West African and Congo Cratons, and with cratonic lithosphere absent beneath large portions of Archean crust. We image the lateral extent of the Niassa Craton, hypothesized previously and identify a new unit, the Cubango Craton, near the southeast boundary of the grater Congo Craton, with both of these smaller cratons unexposed at the surface. In the South Atlantic, the model reveals the patterns of interaction between the Mid-Atlantic Ridge (MAR) and the nearby hotspots. Low-velocity anomalies beneath major hotspots extend substantially deeper than those beneath the MAR. The Vema Hotspot, in particular, displays a pronounced low-velocity anomaly under the thick, high-velocity lithosphere of the Cape Basin. A strong low velocity anomaly also underlies the Cameroon Volcanic Line and its offshore extension, between Africa and the MAR. Subtracting the global, age-dependent VS averages from those in the South Atlantic Basins, we observe areas where the cooling lithosphere is locally hotter than average, corresponding to the location of the Tristan da Cunha, Vema and Trindade hotspots. Beneath the anomalously deep Argentine Basin, we image unusually thick, high-velocity lithosphere, which suggests that its anomalously great depth can be explained, at least to a large extent, by isostatic, negative lithospheric buoyancy.

Occurrence of the ophiolitic complexes along the Indoburman orogenic belt

1983 ◽  
Vol 120 (2) ◽  
pp. 175-182 ◽  
Author(s):  
R. Duarah ◽  
M. M. Saikia ◽  
C. C. Bhattacharjee
Keyword(s):  
Upper Mantle ◽  
Deep Sea ◽  
Lower Cretaceous ◽  
Late Jurassic ◽  
Orogenic Belt ◽  
Indian Plate ◽  
Mantle Material ◽  
Crust And Upper Mantle ◽  
Thrust Sheets ◽  
Ophiolitic Belt

SummaryThe ophiolitic complexes within the Indoburman orogenic belt form a conspicuous N-S line along the eastern margins of Manipur and Nagaland. The rock assemblages consisting of mafic-ultramafics are associated with deep sea pelagic sediments of the Disang Group (Lower Cretaceous-Eocene). The ultramafics in part, represent the oceanic crust and upper mantle material that formed the basement on which the radiolarites and other pelagic sediments were deposited. The fossil radiolaria present in the cherts suggest that the orogen took its foundation during late Jurassic-Lower Cretaceous time. The westward obduction of the flysch ophiolites in the form of large thrust sheets was possible during underthrusting of the Indian plate beneath the Burmese. The position of the ophiolitic belt defines the Indoburman suture zone.

Post-orogenic granites in Pingwu region, Northwest Sichuan: Evidence for North China block and Yangtze block collision during Triassic

2009 ◽  
Vol 20 (2) ◽  
pp. 250-273 ◽  
Author(s):  
Xianzhi Pei ◽  
Zuochen Li ◽  
Saping Ding ◽  
Jianyun Feng ◽  
Ruibao Li ◽  
...  
Keyword(s):  
North China ◽  
Yangtze Block ◽  
North China Block
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