The role of magmatism in the thinning and breakup of the South China Sea continental margin

Sun, Zhen; Lin, Jian; Qiu, Ning; Jian, Zhimin; Wang, Pinxian; Pang, Xiong; Zheng, Jinyun; Zhu, Bingquan

doi:10.1093/nsr/nwz116

Cited by 108 publications

(82 citation statements)

References 8 publications

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“…However, we note that we are dealing with magma-poor environments, with half-extension velocities of 5 mm yr −1 , where total magmatic crustal thicknesses are anticipated to be around 3 km (see Figure 4 of Ros et al, 2017). In the margins analyzed here and elsewhere a recurrent and important observation is the occurrence of distal highs (see profiles shown here and also Seismic Section 155 in the South China IODP 367-368 drilling area by Sun et al, 2019, andNirrengarten et al, 2020, seismic profiles in southern Australia by Gillard et al, 2015, andeastern India by Pindell et al, 2014, among others). In our models these distal highs correspond to the footwalls of the last oceanward conjugate faults that breakup the crust and lead to formation of new ocean floor.…”

Section: 1029/2020tc006255mentioning

confidence: 74%

Lithospheric Strength and Rift Migration Controls on Synrift Stratigraphy and Breakup Unconformities at Rifted Margins: Examples From Numerical Models, the Atlantic and South China Sea Margins

et al. 2020

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Synrift stratigraphy and the distribution of breakup-related erosional unconformities vary vastly between passive margins and cannot be explained by classical rifting models. Here we use numerical modeling to predict their spatiotemporal distribution. We show that synrift stratigraphy mimics rift architecture, which is controlled by lithospheric strength. Basinward rift migration during extension produces (1) oceanward younging, syntectonic and posttectonic sequences, (2) rift migration unconformities, RMUs, predating breakup, and (3) a breakup unconformity, BU, that only extends over the outermost margins, since breakup is not linked with a sudden stress drop. With small synrift sedimentation, the RMUs and BU laterally merge to form a margin-wide unconformity. In symmetric, wide conjugate margins, which arise for weak lithospheres such as the South China Sea, a long phase of distributed deformation with little subsidence results in early synrift sediment over most of the margins. RMUs merge into a single event that marks the subsequent focusing of deformation into a narrow breakup area, which experiences short-lived intense thinning and subsidence. In asymmetric conjugate margins, lateral rift migration transports shallowly deposited, early synrift sediments from the narrow to the wide, hyperextended margin, leading to a condensed syntectonic sequence and a single BU in the narrow margin and a series of RMUs in the wide one. For very weak lower crusts, lateral rift migration generates large synrift sag basins in the wide margin, as in Angola and Congo margins. Our models resemble the observed margins tectonic diversity and may be used as templates for interpreting their distal, unexplored areas.

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Section: 1029/2020tc006255mentioning

confidence: 74%

Lithospheric Strength and Rift Migration Controls on Synrift Stratigraphy and Breakup Unconformities at Rifted Margins: Examples From Numerical Models, the Atlantic and South China Sea Margins

et al. 2020

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“…IODP Site U1504 cored the basement of another OMH in the more distal margin and recovered greenschist mylonites overlain by the late Eocene syn-rift sediments (Larsen et al, 2018b). Macrostructure and mineral analysis suggest that the mylonites experienced mainly normal ductile shearing and is supposed to be exhumed from midcrust during Cenozoic extension (Sun, Lin, et al, 2019). Thus, the top of seismic basement corresponds to a stratigraphic unconformity and/or a detachment surface.…”

Section: Methodsmentioning

confidence: 99%

Discovery of Mega‐Sheath Folds Flooring the Liwan Subbasin (South China Sea): Implications for the Rheology of Hyperextended Crust

Zhang

Manatschal

Pang

et al. 2020

Geochem Geophys Geosyst

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Sheath folds recognized on kilometer scale are rare and only described in salt tectonics in seismic data. Here, we present mega‐sheath folds spectacularly imaged in a 3‐D seismic survey in the seismic basement flooring the hyperextended Liwan subbasin in the northern margin of the South China Sea. The sheath folds show eye structures delimited by anastomosing discontinuities. The axial planes of the sheath folds are subparallel to a rift‐related, extensional detachment surface separating hyperextended seismic basement from the syn‐rift sedimentary sequence. The sheath folds as well as the anastomosing discontinuities formed during hyperextension by ductile shearing of the forearc inherited and prestructured metasediments. The ductile shearing eventually resulted in the metasediments derived from midcrust unroofed at the footwall of an extension detachment fault. The discovery of mega‐sheath folds and ductile deformation within the basement conflicts with the general assumption that hyperextended domains are in the brittle field. The new seismic observations show the importance of forearc inherited, prestructured anisotropic basement controlling the crustal rheology during hyperextension.

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“…Plate reconstructions of the SCS region. The schematic of the process of subduction direction reversal in plane (a-b) and in profile (c-f) (summarized after Hall, 2002;Holloway, 1982;Li et al, 2014;Li, Sun, & Zhang, 2018;Pautot et al, 1986;Sun et al, 2009Sun et al, , 2019Wu & Suppe, 2018…”

Section: Numerical Model Descriptionmentioning

confidence: 99%

“…A similar but smaller slab remnant was also recognized by interpreting the wide‐angle seismic profiles (Zhou et al, 2006). These slab remnants were possibly the results of a slab‐tear event that occurred during the rifting of the continental edge (Sun et al, 2019; Wu & Suppe, 2018).…”

Section: Introductionmentioning

confidence: 99%

Continental Interior and Edge Breakup at Convergent Margins Induced by Subduction Direction Reversal: A Numerical Modeling Study Applied to the South China Sea Margin

Sun

Yang

et al. 2020

Tectonics

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The dynamics of continental breakup at convergent margins has been described as the results of backarc opening caused by slab rollback or drag force induced by subduction direction reversal. Although the rollback hypothesis has been intensively studied, our understanding of the consequence of subduction direction reversal remains limited. Using thermo-mechanical modeling based on constraints from the South China Sea (SCS) region, we investigate how subduction direction reversal controls the breakup of convergent margins. The numerical results show that two distinct breakup modes, namely, continental interior and edge breakup ("edge" refers to continent above the plate boundary interface), may develop depending on the "maturity" of the convergent margin and the age of the oceanic lithosphere. For a slab age of~15 to~45 Ma, increasing the duration of subduction promotes the continental interior breakup mode, where a large block of the continental material is separated from the overriding plate. In contrast, the continental edge breakup mode develops when the subduction is a short-duration event, and in this mode, a wide zone of less continuous continental fragments and tearing of the subducted slab occur. These two modes are consistent with the interior (relic late Mesozoic arc) and edge (relic forearc) rifting characteristics in the western and eastern SCS margin, suggesting that variation in the northwest-directed subduction duration of the Proto-SCS might be a reason for the differential breakup locus along the strike of the SCS margin. Besides, a two-segment trench associated with the northwest-directed subduction is implied in the present-day SCS region.

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The role of magmatism in the thinning and breakup of the South China Sea continental margin

Cited by 108 publications

References 8 publications

Lithospheric Strength and Rift Migration Controls on Synrift Stratigraphy and Breakup Unconformities at Rifted Margins: Examples From Numerical Models, the Atlantic and South China Sea Margins

Lithospheric Strength and Rift Migration Controls on Synrift Stratigraphy and Breakup Unconformities at Rifted Margins: Examples From Numerical Models, the Atlantic and South China Sea Margins

Discovery of Mega‐Sheath Folds Flooring the Liwan Subbasin (South China Sea): Implications for the Rheology of Hyperextended Crust

Continental Interior and Edge Breakup at Convergent Margins Induced by Subduction Direction Reversal: A Numerical Modeling Study Applied to the South China Sea Margin

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