Research progress on the Zhongnan-Liyue Fault Zone in the South China Sea Basin

Abstract

<p>We give a review of the up-to-date research situation about The Zhongnan-Liyue Fault Zone (ZLFZ), than analyze the spatial distribution and tectonic deformation feature of the ZLFZ based on the geophysical data including topographic, seismic, gravity and magnetic data. The results show that the ZLFZ has obvious north-south segmentation characteristics in in the South China Sea Basin. The north section, which is between northwest sub-basin and east sub-basin, is a narrow zone with the width of ~16 km, and is NNW trend from 18°N,115.5°E to 17.5°N,116°E. Meanwhile ,the south section, which is between southwest sub-basin and east sub-basin, is a wide zone with the width of 60-80 km, and is NNW trend from the east of ZhongshaBank to the west of LiyueBank. The main fault of the ZLFZ is NNW trend along the seamounts ridge of Zhongnan. the ZLFZ of transition region is NNE trend from the north section to the south section. According the sub-basin’s sedimentary thickness and oceanic crust thickness exist obvious difference, on both sides of the ZLFZ, we speculate that the ZLFZ play an important role on geological structure of sub-basin. According to the chang of crustal structure, We speculate that the ZLFZ is at least a crustal fracture zone.</p><p><strong>Key words: </strong>South China Sea Basin; Zhongnan-Liyue Fault Zone; Spatial distribution; Tectonic deformation<strong> </strong></p><p><strong>Foundation item:</strong> National Natural Science Foundation of China (41606080, 41576068); The China Geological Survey Program (GZH201400202, 1212011220117, DD20160138, 1212011220116).</p>

Rifting/spreading propagation interacts with preexisting transform faults: 3D geodynamic modeling

“…This supports that the Zhongnan Fault Zone was a continental transform fault which evolved to an oceanic transform fault before and after the South China Sea basin spreading. Firstly, the dynamic growth of the transform fault modeled in our study is comparable to the Zhongnan Fault Zone in the South China Sea basin (Figure 12; Xu et al, 2019;Roeser, 2004, Barckhausen et al, 2014;Frank, 2013;Frank et al, 2004;Ruan et al, 2016;Sibuet et al, 2016). 1) The Zhongnan Fault Zone is 15-25 km wide at its northern end (Figure 12B), 60 km wide in the middle (Figure 12C) and ~35 km wide in the southern end (Figure 12D) revealed by seismic reflection data (Ruan et al, 2016;Qiu et al, 2019;Xu et al, 2021).…”

“…Our model results are comparable to the observations of the South China Sea basin, in terms of the growth of transform faults, the formation of ridge segments and the establishment of a volcanic chain. According to the fine interpretation of the seismic reflection Frontiers in Earth Science frontiersin.org profiles in the South China Sea basin (Figure 12B), the Zhongnan Fault Zone cuts through the T6 horizon as well as the Tg horizon, but does not cut through the T5 horizon (where T5, T6 and Tg represents the early Miocene interface, the late Oligocene interface, and the early Oligocene basement, respectively), indicating that the Zhongnan Fault Zone was active before the early Oligocene-prior to the spreading of the South China Sea basin (~32 Ma; e.g., Li, 2012;Xu et al, 2019). This supports that the Zhongnan Fault Zone was a continental transform fault which evolved to an oceanic transform fault before and after the South China Sea basin spreading.…”

“…Although the age of the Zhongnan Fault Zone is debated (Tongkul et al, 1993;Li et al, 2008;Li et al, 2012;Li et al, 2014;Ruan et al, Frontiers in Earth Science frontiersin.org 04 2016; Sibuet et al, 2016), increasing studies proposed that the Zhongnan Fault Zone was formed before the South China Sea basin spreading (Briais et al, 1993;Sibuet et al, 2016;Li et al, 2017). The recent studies using seismic reflection data demonstrated that the Zhongnan Fault Zone developed before the opening of the South China Sea basin (Li et al, 2017;Xu et al, 2019, Xu et al, 2021.…”

“…FIGURE 12Variations in the width of the Zhongnan Fault Zone in the South China Sea basin. (A) Topographic map in the South China Sea basin (B-D) Seismic reflection profiles of the north, central and south Zhongnan Fault Zone (L1, L2 in a, fromXu et al, 2019, L3 from Qiu et al, 2019.…”