Deng Hongdan, Ren Jianye, Pang Xiong, Rey Patrice F, McClay Ken R, Watkinson Ian M, Zheng Jingyun, Luo Pan
Hubei Key Laboratory of Marine Geological Resources, China University of Geosciences, 430074, Wuhan, China.
College of Marine Science and Technology, China University of Geosciences, 430074, Wuhan, China.
Nat Commun. 2020 Sep 11;11(1):4583. doi: 10.1038/s41467-020-18448-y.
During extension, the continental lithosphere thins and breaks up, forming either wide or narrow rifts depending on the thermo-mechanical state of the extending lithosphere. Wide continental rifts, which can reach 1,000 km across, have been extensively studied in the North American Cordillera and in the Aegean domain. Yet, the evolutionary process from wide continental rift to continental breakup remains enigmatic due to the lack of seismically resolvable data on the distal passive margin and an absence of onshore natural exposures. Here, we show that Eocene extension across the northern margin of the South China Sea records the transition between a wide continental rift and highly extended (<15 km) continental margin. On the basis of high-resolution seismic data, we document the presence of dome structures, a corrugated and grooved detachment fault, and subdetachment deformation involving crustal-scale nappe folds and magmatic intrusions, which are coeval with supradetachment basins. The thermal and mechanical weakening of this broad continental domain allowed for the formation of metamorphic core complexes, boudinage of the upper crust and exhumation of middle/lower crust through detachment faulting. The structural architecture of the northern South China Sea continental margin is strikingly similar to the broad continental rifts in the North American Cordillera and in the Aegean domain, and reflects the transition from wide rift to continental breakup.
在伸展过程中，大陆岩石圈变薄并破裂，根据伸展岩石圈的热机械状态形成宽或窄的裂谷。宽达1000公里的宽大陆裂谷在北美科迪勒拉山脉和爱琴海地区得到了广泛研究。然而，由于缺乏关于远端被动大陆边缘的地震可分辨数据以及陆上自然露头，从宽大陆裂谷到大陆解体的演化过程仍然是个谜。在此，我们表明，南海北缘的始新世伸展记录了宽大陆裂谷与高度伸展（<15公里）的大陆边缘之间的过渡。基于高分辨率地震数据，我们记录了穹窿构造、波状和槽状拆离断层以及涉及地壳规模推覆褶皱和岩浆侵入体的拆离下变形的存在，这些与拆离上盆地是同时期的。这个广阔大陆区域的热和力学弱化使得变质核杂岩得以形成、上地壳香肠状构造化以及通过拆离断层作用使中/下地壳得以剥露。南海北部大陆边缘的构造结构与北美科迪勒拉山脉和爱琴海地区的宽大陆裂谷惊人地相似，反映了从宽裂谷到大陆解体的过渡。
