Slab Rollback Versus Delamination: Contrasting Fates of Flat-Slab Subduction and Implications for South China Evolution in the Mesozoic
Slab Rollback Versus Delamination: Contrasting Fates of Flat-Slab Subduction and Implications for South China Evolution in the Mesozoic
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DOI：
10.1029/2019jb019164
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发表时间：
2020-04-01
影响因子：
3.9
通讯作者：
Yu, Shengyao
中科院分区：
文献类型：
--
作者：
Dai, Liming;Wang, Liangliang;Yu, Shengyao
越来越多的证据表明，中国地块南部广泛发育的中生代褶皱和岩浆活动是由于古太平洋板块的平板俯冲和板块陡峭作用所致。然而，从平面到陡峭板块俯冲的动力学，以及构造过程与地表变形和岩浆事件之间的关系，受到的约束很少。利用二维热力学数值模型，系统地研究了俯冲大洋高原榴辉岩化后板片回滚或剥离对地表地形、构造变形和岩浆作用的影响。我们的结果表明，大洋高原的俯冲驱动了平板俯冲，进而导致了宽阔的逆冲断裂带、隆起和岩浆活动的前陆以及前陆盆地的沉降。受俯冲速率和大洋高原榴辉岩化时间的控制，通过板片回滚或剥离从平板片俯冲到陡峭板片俯冲，这一模式变得更加复杂。数值计算结果与中国南部地质资料的对比表明，板片拆沉模型再现了中国南部中生代的区域演化。基于我们的模型，我们认为板块俯冲过程中的榴辉岩化不是瞬时的，而是在大洋高原达到理想的相变条件后至少18Myr。
Growing evidence supports that the widely developed Mesozoic folds and magmatism in the South China Block are attributed to the flat-slab subduction, followed by slab steepening, of the Paleo-Pacific Plate (PPP). However, the dynamics of the transition from flat- to steep-slab subduction, as well as the relationship between tectonic processes and surface deformation and magmatic events, are poorly constrained. Using a 2-D thermomechanical numerical model, we systematically investigate the effects of slab rollback or delamination following the eclogitization of a subducted oceanic plateau on the surficial topography, structural deformation, and magmatism. Our results indicate that the subduction of an oceanic plateau drives flat-slab subduction, which further leads to the development of a wide thrust fault zone, an uplifted and magmatically active foreland, and the foreland basin subsidence. This model is further complicated by the transition from flat- to steep-slab subduction through slab rollback or delamination which is controlled by the subduction rate and the timing of oceanic plateau eclogitization. The comparisons between our numerical results and the geological data from South China reveal that the slab delamination model reproduces the regional evolution of the Mesozoic South China. Based on our models, we suggest that the eclogitization during flat-slab subduction is not instantaneous, which is instead at least 18 Myr after the oceanic plateau reaches the ideal conditions of phase change.