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首页> 外文期刊>Earth and Planetary Science Letters: A Letter Journal Devoted to the Development in Time of the Earth and Planetary System >Thermal modelling of the Laramide orogeny: testing the flat-slab subduction hypothesis
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Thermal modelling of the Laramide orogeny: testing the flat-slab subduction hypothesis

机译：Laramide造山运动的热模型：测试平板俯冲假说

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摘要

The Laramide orogeny is the Late Cretaceous to Palaeocene (80-55 Ma) orogenic event that gave rise to the Rocky Mountain fold and thrust belt in Canada, the Laramide block uplifts in the USA, and the Sierra Madre Oriental fold and thrust belt in Mexico. The leading model for driving Laramide orogenesis in the USA is flat-slab subduction, whereby stress coupling of a subhorizontal oceanic slab to the upper plate transmitted stresses eastwards, producing basement-cored block uplifts and arc magmatism in the foreland. The thermal models presented here indicate that arc magma generation at significant distances inboard of the trench (>600 km) during flat-slab subduction is problematic; this conclusion is consistent with the coincidence of volcanic gaps and flat-slab subduction at modern convergent margins. Lawsonite eclogite xenoliths erupted through the Colorado Plateau in Oligocene time are inferred to originate from the subducted Farallon slab, and indicate that the Laramide flat-slab subduction zone was characterised by a cold thermal regime. Thermal modelling indicates that this regime can be produced by flat-slab subduction of old (> ～ 50 Myr) oceanic lithosphere at high convergence rates. In the Canadian and Mexican portions of the Laramide orogen, the coeval development of a magmatic arc within 300 km of the trench refutes the existence of flat-slab subduction in these regions. It is proposed that subduction of an oceanic plateau/aseismic ridge may have overcome the negative buoyancy inherent in old oceanic lithosphere and resulted in a spatially restricted zone of flat-slab subduction in the USA. These findings case doubt on the flat-slab model as a primary means of driving Laramide orogenesis along its entire length, and instead point to the need for an alternative mechanism for Cordilleran-wide Laramide orogenesis.
机译：Laramide造山带是白垩纪至新世晚期（80-55 Ma）的造山事件，在加拿大引起了落基山褶皱和逆冲带，在美国引起了Laramide块隆升，在墨西哥引起了Sierra Madre Oriental褶皱和逆冲带。在美国，驱动拉拉米邦造山运动的主要模型是平板俯冲，即水平海底平板到上板的应力耦合将应力向东传递，从而在前陆产生基底带芯块隆起和弧岩浆作用。这里介绍的热模型表明，在平板俯冲过程中，在沟槽内侧相当远的距离（> 600 km）产生电弧岩浆是有问题的。这个结论与现代收敛边缘的火山间隙和平板俯冲的巧合相一致。渐新世时期从科罗拉多高原喷发的钙钠榴石榴辉岩异岩被推断为源自俯冲的法拉隆板块，并表明拉拉酰胺平板俯冲带的特征是冷热作用。热力模型表明，这种状态可以由旧的（>〜50 Myr）大洋岩石圈平板在高收敛速度下俯冲而产生。在拉拉米造山带的加拿大和墨西哥部分，距海沟300公里以内的岩浆弧的同时代发展驳斥了这些地区平板俯冲的存在。有人认为，在美国，海洋高原/地震脊的俯冲可能已经克服了旧海洋岩石圈固有的负浮力，并导致了平板俯冲的空间受限区域。这些发现使人们怀疑平板模型是驱动其整个长度上拉曼酰胺造山运动的主要手段，相反，这表明需要一种用于整个科迪勒兰山脉拉米酰胺造山运动的替代机制。

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