GEOGRAPHY

The evolutionary process of oblique extension of volcanic passive continental margin development was revealed


Recently, Guan Huixin, associate researcher of the South China Sea Institute of Oceanology, Chinese Academy of Sciences, and Xu Min, a researcher at the Institute of Oceanology, together with researchers from the University of West Breton in France and the University of Oslo in Norway, have made new progress in the study of the development and evolution process of obliquely stretched volcanic passive continental margin. The study was published in Structural Physics.

Oblique rift refers to the fact that during the process of crustal tension, there is a certain angle between the tension direction of the rift valley and the orthogonal direction of the central axis of the rift valley. For the magma-poor rift environment, the developmental evolution process of oblique rift has been extensively studied. However, in the magma-rich rift environment, there is little research on the formation and developmental evolution of oblique rift valleys.

The western continental margin of Greenland was formed during the early Tertiary Greenlandic-North American plate cracking period, and was influenced by the development of the North Atlantic large igneous province. In the process of continental fissure, the tensile direction is 57 degrees orthogonal to the continental margin, which belongs to the passive continental margin with high angle oblique extension, and is also a typical case for studying the genesis of oblique rift.

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Evolutionary pattern of SDR in Nusuak region. Photo courtesy of the research team

The researchers combined satellite remote sensing data, field observation data and multi-channel reflected seismic data to analyze the three-dimensional structure of the sea-tilting reflective layer (SDR) in the Nusuac region of western Greenland, revealing for the first time the development and evolution of the obliquely stretched volcanic passive continental margin. Taking the development of the sea-tilting reflective layer in this area as an example, the development process of obliquely stretched volcanic passive continental margin SDR goes through two stages: the first stage stress is decomposed into two components, strike-slip and tilt-slip, and the strike-slip fault and normal fault are developed at the same time. Then, in the second stage, the stress near the land margin is reoriented.

The direction of the legacy structures has an inclination angle to the regional stress, which causes these structures to be reactivated during the tensile cracking process, which in turn deflects the local stress; The magma pressure upgushing in the mantle is high, and when flowing horizontally, stress perpendicular to the continental margin is generated at the passive land margin, resulting in the reorientation of local stress.

“This study is the development process of obliquely stretched volcanic passive continental margin, and it was previously thought that normal continental margin SDR development is the same process, but because the tension fissure is oblique, there are two stages of strain decomposition and stress shift in SDR development.” Guan Huixin said that the results of this study provide an important clue for the understanding of the development process of passive continental margin SDR, and are of great significance for in-depth understanding of the mantle-crust interaction relationship during continental fissure. (Source: China Science News, Zhu Hanbin, Li Shu)

Related paper information:https://doi.org/10.1016/j.tecto.2023.229936



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