Thermal evolution of a rift basin: The Tyrrhenian Sea
Thermal evolution of a rift basin: The Tyrrhenian Sea
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裂谷盆地的热演化：第勒尼安海
DOI：
10.1029/jb094ib04p03991
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发表时间：
1989
影响因子：
--
通讯作者：
Yaolin Shi
中科院分区：
文献类型：
--
作者：
Chi‐yuen Wang;W. Hwang;Yaolin Shi
现有的地质和地球物理数据支持这样一种观点，即第勒尼安海的开放是由以前连续的大陆岩石圈的裂谷作用造成的，该大陆岩石圈始于上中新世的上撒丁岛边缘，并向东南迁移到卡拉布里亚边缘。流经第勒尼安海的热流显示出明显的不对称性，撒丁岛边缘的热流约为50-70 mW m−2，而在意大利南部和卡拉布里亚的东南边缘则超过150 mW m−2。在这项研究中，我们使用新获得的数据从大洋钻探计划腿107，热流，地震速度和测深数据约束一组模型，假设第勒尼安海开放的剥离以前连续的岩石圈沿着东南面向，低角度的正断层。检验的具体模型包括：（1）Wernicke模型，该模型认为大陆岩石圈的减薄和伸展是通过沿着一条大规模、缓倾的拆离断层带的“简单剪切”完成的，该断层带贯穿整个岩石圈;（2）拆沉模型，其中，低角度拆离断层被认为只切割上地壳和中地壳，但近水平地并入下地壳，在下地壳之下可能发生并发的纯剪切。一个通用的，二维有限元程序被用来评估这些模型的构造和热演化，并与观测结果进行比较，以测试模型的有效性。在岩石圈下部具有大的纯剪切分量的脱层模型和Wernicke模型预测的热流值与测量值相差不超过±1σ。然而，Wernicke模型预测的盆地配置太深，与测深和一个subbasinal岩石圈厚度基本上不同的瑞利波色散结果相比。拆沉模型与一个大的组成部分，在subbasinal较低的岩石圈纯剪切，另一方面，令人满意的预测水深和岩石圈厚度的盆地。
Existing geological and geophysical data support the view that the opening of the Tyrrhenian Sea was by rifting of a formerly continuous continental lithosphere, which began in upper Miocene on the upper Sardinian margin and migrated southeastward to the Calabria margin. Heat flow across the Tyrrhenian Sea shows a pronounced asymmetry, from about 50–70 mW m−2 over the Sardinian margin, to more than 150 mW m−2 over its southeastern margin off southern Italy and Calabria. In this study we use the newly acquired data from Ocean Drilling Program Leg 107, heat flow, seismic velocity, and bathymetric data to constrain a group of models that supposes the Tyrrhenian Sea opened by detachment of a formerly continuous lithosphere along a southeastern facing, low-angle normal fault. Specific models tested include (1) the Wernicke model, in which thinning and extension of the continental lithosphere are supposed to be accomplished by “simple shear” along a large-scale, gently dipping detachment fault zone which cut through the entire lithosphere, and (2) the delamination model, in which the low-angle detachment fault is supposed to cut only the upper and middle crust but to merge subhorizontally into the lower crust, below which concurrent pure shear may occur. A versatile, two-dimensional finite element procedure is used to evaluate the tectonic and thermal evolution of these models, and the results are compared with observations to test the validity of the models. Delamination models with large pure shear components in the lower lithosphere and the Wernicke model predict heat flow within ±1σ of the measurements. The Wernicke model, however, predicts a basin configuration much too deep in comparison with bathymetry and a subbasinal lithospheric thickness substantially different from Rayleigh wave dispersion results. The delamination model with a large component of pure shear in the subbasinal lower lithosphere, on the other hand, predicts satisfactorily both the bathymetry and the lithospheric thickness beneath the basin.