Recognizing detachment-mode seafloor spreading in the deep geological past.
Recognizing detachment-mode seafloor spreading in the deep geological past.
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DOI：
10.1038/srep02336
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发表时间：
2013
影响因子：
4.6
通讯作者：
Anderson, Mark W.
中科院分区：
文献类型：
--
作者：
Maffione, Marco;Morris, Antony;Anderson, Mark W.
大偏移距的大洋拆离断层是慢速和超慢速扩张洋脊的一个特征，导致大洋核杂岩（OCC）的形成，使上地幔和下地壳岩石暴露在海底。这些结构所容纳的岩石圈伸展，现在被认为是一个根本不同的“扩张模式”的海底扩张相比，经典的岩浆增生。在这里，我们展示了一个古地磁的方法，允许明确的识别古蛇绿岩的扩张模式海底扩张，并将其应用到一个潜在的侏罗纪拆离断层系统的米尔迪塔蛇绿岩（阿尔巴尼亚）。我们发现，下盘和上盘块体的推断拆离的任何一方有显着不同的磁化，只能解释在海底扩张的相对旋转。旋转的风格被证明是相同的滚动铰链下盘旋转记录最近在OCC在大西洋，证实了扩张模式的扩展操作至少早在侏罗纪。
Large-offset oceanic detachment faults are a characteristic of slow- and ultraslow-spreading ridges, leading to the formation of oceanic core complexes (OCCs) that expose upper mantle and lower crustal rocks on the seafloor. The lithospheric extension accommodated by these structures is now recognized as a fundamentally distinct “detachment-mode” of seafloor spreading compared to classical magmatic accretion. Here we demonstrate a paleomagnetic methodology that allows unequivocal recognition of detachment-mode seafloor spreading in ancient ophiolites and apply this to a potential Jurassic detachment fault system in the Mirdita ophiolite (Albania). We show that footwall and hanging wall blocks either side of an inferred detachment have significantly different magnetizations that can only be explained by relative rotation during seafloor spreading. The style of rotation is shown to be identical to rolling hinge footwall rotation documented recently in OCCs in the Atlantic, confirming that detachment-mode spreading operated at least as far back as the Jurassic.
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