The continent-ocean transition architecture and breakup mechanism at the mid-northern South China Sea
- 1Key Laboratory of Ocean and Marginal Sea Geology, South China Sea Institute of Oceanology, Innovation Academy of South China Sea Ecology and Environmental Engineering, Chinese Academy of Sciences,Guangzhou, 510301, China.
- 2Southern Marine Science and Engineering Guangdong Laboratory, Guangzhou 511458, China.
- 3Institut de Physique du Globe de Strasbourg, CNRS-UMR 7516, Université de Strasbourg, F-67084 Strasbourg Cedex, France.
- 4CNOOC Ltd.-Shenzhen, Shenzhen, 518054, China.
- 5CNOOC Ltd.-Deepwater, Shenzhen, 518054, China.
- 6Key Lab of Submarine Geosciences and Prospecting Techniques, MOE, Institute for Advanced Ocean Study, Ocean University of China, Qingdao 266100, China.
- 7Laboratories for Marine Mineral Resources and Marine Geology, National Laboratory for Marine Science and Technology, Qingdao 266237, China.
- 8Geological Survey of Norway, 7040 Trondheim, Norway.
- 9Department of Geoscience and Petroleum, Norwegian University of Science and Technology (NTNU), 7491 Trondheim, Norway.
Ocean Continent Transition (OCT) located between the edge of the continental and unequivocal oceanic crust is an ideal laboratory to understand one of the most fundamental processes of Plate Tectonics, namely the mechanism of formation of a new plate boundary, also referred to as lithospheric breakup. However, the location and architecture of the OCT and the processes governing the rupture of continental lithosphere and creation of new oceanic crust remain debated. In this paper, we present newly released high-resolution seismic reflection profiles that image the complete transition from unambiguous continental to oceanic crust in the mid-northern South China Sea (SCS), accompanied with IODP drill hole and gravity data, with the aim to map the OCT and explore where, when and how lithospheric breakup occur.
Based on observations and interpretations we define the limits of OCT. The results show that OCT corresponds to hybrid crust resulting from the complex interaction between crustal thinning along detachment systems and accretion of new syn-tectonic igneous materials. The observations suggest a sharp along strike transition in the OCT from a lower to an upper plate setting over a lateral distance of 25 km. The breakup in the northern SCS and the conjugate margin occurred asymmetrically and was accomplished by core-complex type structures related to a successive oceanward transition from tectonic to magma-controlled processes during plate separation. The along-strike variability in the basement architecture and the abrupt flip in detachment polarity in the OCT imply a sharp transfer fault to explain the segmentation of the margin. Such segmentation results from inherited pre-rift crustal and/or lithospheric heterogeneities. It is important to note that the segmentation did not control breakup and subsequent oceanic accretion.
How to cite: Zhang, C., Sun, Z., Manatschal, G., Pang, X., Li, S., Sauter, D., and Peron-Pinvidic, G.: The continent-ocean transition architecture and breakup mechanism at the mid-northern South China Sea, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-1625, https://doi.org/10.5194/egusphere-egu21-1625, 2021.