Narrow rifts versus wide rifts: inferences for the mechanics of rifting from laboratory experiments
Narrow rifts versus wide rifts: inferences for the mechanics of rifting from laboratory experiments
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DOI：
10.1098/rsta.1999.0349
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发表时间：
1999-04-15
期刊：
影响因子：
5
通讯作者：
Brun, JP
中科院分区：
文献类型：
--
作者：
Brun, JP
岩石圈模拟模型的实验室实验是研究构造过程，特别是检验物理假说的有用工具。它们是对数值模拟的补充，因为每种方法的固有局限性是不同的。回顾了该方法的基本原理，并特别应用于模拟大陆地壳和岩石圈的脆性-延性分层的模型，用砂和硅灰来模拟岩石的摩擦和粘性行为。一系列实验被用来检验流变学在地壳尺度伸展结构发展中的作用：大陆裂谷、被动边缘、宽广的延展区域和核心杂岩。窄裂谷和宽裂谷之间的差异归因于对给定类型的岩石圈强度剖面可能产生的机械不稳定类型：即缩颈与扩展。颈缩优先发生在一个稳定的岩石圈中，该岩石圈具有四层型的强度剖面，其中最大强度位于次莫霍面地幔。它催生了狭窄的裂谷，从大陆裂谷到被动边缘。扩张优先发生在增厚的岩石圈，其强度剖面在热弛豫后，在上脆性地壳的底部表现出最大强度。它产生了宽阔的裂缝，如美国西部或爱琴海的盆地和山脉。核心杂岩不被认为代表了一种特定的伸展模式，而是宽阔裂谷中的异常。
Laboratory experiments on analogue models of the lithosphere are useful tools to study tectonic processes and, in particular, to test physical hypotheses. They complement numerical modelling because the inherent limitations of each method are different. The basic principles of the method are recalled with particular application to models simulating the brittle-ductile layering of continental crust and lithosphere using sand and silicone putties to simulate the frictional and viscous behaviour of rocks. A selection of experiments is used to examine the role of rheology on the development of crustal-scale extensional structures: continental rifts, passive margins, wide extended domains, and core complexes. The difference between narrow rifts and wide rifts is attributed to the type of mechanical instability that can develop for a given type of lithospheric strength profile: namely necking versus spreading. Necking occurs preferentially in a stable lithosphere that has a four layer-type of strength profile with the greatest strength located in the sub-Moho mantle. It gives birth to narrow rifts, from continental rifts to passive margins. Spreading occurs preferentially in a thickened lithosphere whose strength profile, after thermal relaxation, exhibits maximum strength at the base of upper brittle crust. It gives birth to wide rifts, such as the Basin and Range of the western United States or the Aegean. Core complexes are not considered to represent a particular mode of extension but are anomalies in wide rifts.