Mode of lithospheric extension: Conceptual models from analogue modeling
Mode of lithospheric extension: Conceptual models from analogue modeling
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DOI：
10.1029/2002tc001435
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发表时间：
2003-04
期刊：
影响因子：
4.2
通讯作者：
L. Michon;O. Merle
中科院分区：
文献类型：
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作者：
L. Michon;O. Merle
地壳尺度和岩石圈尺度的模拟实验对比提供了有关岩石圈伸展变形模式的重要信息。研究表明，在拉张过程中，岩石圈变形受韧性剪切带发育的控制。在岩石圈尺度上，全球变形是由脆性地幔岩石圈破裂引起的。这种破坏在下地壳和韧性地幔岩石圈中形成共轭和反向剪切带。韧性层内部应变的分析表明，位于不对称地堑下方的两条相对的剪切带在下地壳和韧性地幔岩石圈中占主导地位。实验表明，从一个类似的初始阶段，这些剪切带的相对优势起源于两种不同的变形模式。如果地壳剪切带占主导地位，一个主要的拆离构造横切整个岩石圈，并控制其减薄。在这个被称为简单剪切模式的模型中，所得到的几何形状显示地壳和岩石圈减薄是横向移动的。如果地幔剪切带占主导地位，岩石圈减薄是由两条主剪切带同时活动引起的。这一过程称为颈缩模式，导致了地壳和地幔岩石圈减薄的垂向叠加。应用到自然实验室（西欧裂谷，红海裂谷和北大西洋），这个概念模型允许在这些省份描述的不同的几何形状和演变的一个合理的解释。北大西洋和红海裂谷系统可能是简单剪切模式的结果，而颈缩模式可以解释西欧裂谷特别是中央地块和埃格地堑的部分演化。
Comparison of analogue experiments at crustal and lithospheric scale provides essential information concerning the mode of deformation during lithospheric extension. This study shows that during extension, lithospheric deformation is controlled by the development of shear zones in the ductile parts. At lithospheric scale, the global deformation is initiated by the rupture of the brittle mantle lithosphere. This failure generates the formation of conjugate and opposite shear zones in the lower crust and the ductile mantle lithosphere. The analysis of the internal strain of the ductile layers suggests that the two opposite shear zones located below the asymmetric graben in the lower crust and the ductile mantle lithosphere prevail. Experiments show that from a similar initial stage, the relative predominance of these shear zones originates two different modes of deformation. If the crustal shear zone prevails, a major detachment‐like structure crosscuts the whole lithosphere and controls its thinning. In this model named the simple shear mode, the resulting geometry shows that crustal and lithospheric thinning are laterally shifted. If the mantle shear zone predominates, the lithospheric thinning is induced by the coeval activity of the two main shear zones. This process called the necking mode leads to the vertical superposition of crustal and mantle lithospheric thinning. Applied to natural laboratories (West European rift, Red Sea rift and North Atlantic), this conceptual model allows a plausible explanation of the different geometries and evolutions described in these provinces. The North Atlantic and the Red Sea rift systems may result from a simple shear mode, whereas the necking mode may explain part of the evolution of the West European rift especially in the Massif Central and the Eger graben.