Natural observations of subduction initiation: Implications for the geodynamic evolution of the Paleo-Asian Ocean

Based on seismic interpretation of 18 regional 3D high‐resolution seismic sections across Liaodong Bay, extension amounts, extension rates and extension coefficients of different seismic sections from the south to the north are calculated by employing balanced section technique. Then, spatio‐temporal distribution of extension amounts is characterized and interpreted. Finally, the analysis of genetic mechanism is conducted and analysed. The results indicate that tectonic evolution in the Paleogene of Liaodong Bay is characterized by episodic extension. Furthermore, spatio‐temporal distribution of extension amounts is relatively uneven. In terms of space, extension amounts are mainly caused by extensional displacement of main depression‐controlled boundary faults and syn‐depositional faults in the depression. In addition, extensional amounts along main depression‐controlled boundary faults are characterized by larger displacement. In terms of time, the periods for horizontal extensional movement can be divided into three stages: The Palaeocene‐Early Eocene (Kongdian Formation‐third member of Shahejie Formation), Middle‐Late Eocene‐Early Oligocene (first and second member of Shahejie Formation) and Middle‐Late Oligocene (Dongying Formation). Among them, extension during the Palaeocene‐Early Eocene occurs both in the north and south of Liaodong Bay. However, extension intensity in the north is stronger than that in the south. Extension intensity in the middle and north during Middle‐Late Eocene‐Early Oligocene obviously increases. In contrast, it is dominated by strike‐slip movement during depositional period of Dongying Formation. Therefore, extension intensity is characterized by significant inheritance. Spatial–temporal distribution of extension amounts is predominantly controlled by tectonic evolution and associated tectonic deformation.

Section: Discussionmentioning

confidence: 99%

Spatio‐temporal distribution and genetic mechanism of Paleogene extension amounts in the Liaodong Bay, Bohai Bay Basin

Xia

Lin

et al. 2022

“…The India–Australia Plate still keeps previous convergence rate and collision direction (Maruyama & Seno, 1986; Ren et al, 2002; Wakita, 2013). The changes in subduction rate and direction of Pacific Plate lead to dextral shear activity in strike‐slip movements during this period (Van Hinsbergen et al, 2021; J. Wu et al, 2016; J. T. J. Wu & Wu, 2019; G. X. Yang et al, 2022). The Philippine Plate collides with south‐western Japan since the 30 Ma, resulting in southward movement of eastern block of Tan‐Lu Fault Belt under joint interaction of the Pacific Plate and the Philippine Plate during the Oligocene deposition.…”

Section: Discussionmentioning

confidence: 99%

The fault activity, tectonic subsidence history, and geodynamics of syn‐depositional faults during the Palaeogene in Liaodong Bay, Bohai Bay Basin

Xia

Lin

et al. 2022

The fault activity, tectonic subsidence history, and geodynamics are analysed based on borehole information and seismic datasets from Liaodong Bay. The results reveal that the faults are intensely active (resulting in the faults that are characterized by more lengths and more throws) both in the northern and southern portions of the study area, while the faults are not active in the central portion of the study area during Kongdian Formation and Shahejie Formation deposition. However, the faults are generally more active in the northern portion of the study area than that in the southern portion of the study area. In contrast, the faults are intensely active in central and southern portion of the study area during Dongying Formation deposition. The numerous syn‐depositional faults, which are intensely active, result in southward movement of depositional centre. The tectonic subsidence history of wells (including well JZ‐A, well JZ‐B, well JZ‐C, well JZ‐D, well JX‐A, and well SZ‐A) in Liaodong Bay indicates that it shows obvious episodic tectonic evolution during the Palaeogene in Liaodong Bay. The episodic tectonic movement (initial rifting, rifting climax, thermal subsiding, and strike‐slip rifting) corresponds to Kongdian Formation and Shahejie Formation deposition, and Dongying Formation deposition, respectively. The spatio‐temporal variation of tectonic subsidence history is closely related to fault activity. The analysis results of balanced cross‐sections show that faults are intensely active during Dongying Formation deposition. However, a few faults are much active than that during Shahejie Formation deposition. There is a slight decrease in tectonic activity intensity during Kongdian Formation and Shahejie Formation deposition. In contrast, there is a significant decrease in tectonic activity intensity during third‐member to first‐member of Dongying Formation deposition. The tectonic activity intensity tends to cease by the end of Dongying Formation.

“…Oceanic plateaus, submarine ridges, and seamounts are mafic igneous regions with a crust that is thicker and much more buoyant than the surrounding oceanic crust, they often resist subduction and thus results in subduction polarity reversal (Figure 7e), and the formation of a new subduction zone behind the accreted terrain (Arrial & Billen, 2013; Cloos, 1993; Kerr & Mahoney, 2007; B. Sun, Kaus, et al, 2021; L. L. Wang, Dai, et al, 2022; G. X. Yang et al, 2022). For example, the subduction direction reversed in the Solomon Islands convergent zone following the collision with the Ontong Java Plateau (Figure 8a; Mann & Taira, 2004).…”

Section: The Effect Of Seamount Chains Subductionmentioning

confidence: 99%

“…But these models above did not address the role of seamount and/or oceanic plateau subduction and accretion. Actually, this might have played a key role in oroclinal bending (Figure 11; Miller et al, 2006; Rosenbaum & Mo, 2011; G. X. Yang, 2019) and resulted in subduction initiation (G. X. Yang et al, 2022).…”

Section: Implications For the Evolution Of Caobmentioning

confidence: 99%

“…This is similar to the natural example of the Solomon‐Vanuatu subduction system polarity‐reversal subduction zone initiation (Figure 8a; Mann & Taira, 2004). Except for subduction transference and subduction polarity reversal triggered by oceanic plateau collision, the plume‐induced subduction initiation played the dominant role prior to Cambrian in the CAOB (G. X. Yang et al, 2022; G. X. Yang, Li, et al, 2020). Moreover, the geochemical anomaly (higher Nd/Sm and 206 Pb/ 204 Pb ratios) in Devonian – Carboniferous volcanic rocks from West Junggar were probably affected by the partial melting of an early seamount in the subduction channel (G. X. Yang, Wang, et al, 2020).…”

Section: Implications For the Evolution Of Caobmentioning

confidence: 99%

See 1 more Smart Citation

The effect of seamount chain subduction and accretion

Yang

Tong

et al. 2022

Self Cite

Seamount chains (oceanic plateaus, submarine ridges) are unique morphologic features on the seafloor, which resulted from the motion of the lithosphere over a convective plume. Seamount chains are being carried along by plate motions, which are eventually subducted beneath continental/oceanic plates or accreted in the accretionary complex, thus causing a series of effects in the convergent margin. In this paper, we briefly review the distribution and features of the typical modern seamount chains, including Hawaiian‐Emperor and Louisville seamount chains, Cocos, Ninetyeast and Caroline ridges, and Ogasawara Plateau, and mainly focus on the effects of seamount chains subduction and accretion. The geological effects mainly include the following: (1) deformation and tectonic erosion of the overriding plate; (2) flat‐slab subduction in the convergent margin; (3) growth of continental crust through time; (4) subduction initiation of plate tectonics; (5) generation of large earthquakes; (6) magmatism of the volcanic arc; and (7) formation of porphyry copper and gold deposits. The subduction of seamount chains resulted in similar effects in the Central Asian Orogenic Belt (CAOB) which is one of the largest and longest‐lived accretionary orogens on Earth. However, there are still many aspects that need further improvements, such as identification of the seamounts in the geological record, and geodynamic effects of subducted seamount chains. A detailed study on these sides of the seamount chains will enable us to further understand the tectonic evolution and metallogenesis of the CAOB, especially in accretionary orogenesis, continental crust growth, and subduction initiation dynamics.