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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 >Impact induced melting and the development of large igneous provinces
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Impact induced melting and the development of large igneous provinces

机译：撞击诱发的融化与火成大省的发展

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We use hydrodynamic modelling combined with known data on mantle melting behaviour to examine the potential for decompression melting of lithosphere beneath a large terrestrial impact crater. This mechanism may generate sufficient quantity of melt to auto-obliterate the crater. Melting would initiate almost instantaneously, but the effects of such massive mantle melting may trigger long-lived mantle up-welling that could potentially resemble a mantle hotspot. Decompression melting is well understood; it is the main method advocated by geophysicists for melting on Earth, whether caused by thinned lithosphere or hot rising mantle plumes. The energy released is largely derived from gravitational energy and is outside (but additive to) the conventional calculations of impact modelling, where energy is derived solely from the kinetic energy of the impacting projectile, be it comet or asteroid. The empirical correlation between total melt volume and crater size will no longer apply, but instead there will be a discontinuity above some threshold size, depending primarily on the thermal structure of the lithosphere. We estimate that the volume of melt produced by a 20 km diameter iron impactor travelling at 10 km/s may be comparable to the volume of melt characteristic of terrestrial large igneous provinces (～10~6 km~3); similar melting of the mantle beneath an oceanic impact was also modelled by Roddy et al. [Int. J. Impact Eng. 5 (1987) 525]. The mantle melts will have plume-like geochemical signatures, and rapid mixing of melts from sub-horizontal sub-crater reservoirs is likely. Direct coupling between impacts and volcanism is therefore a real possibility that should be considered with respect to global stratigraphic events in the geological record. We suggest that the end-Permian Siberian Traps should be reconsidered as the result of a major impact at ～250 Ma. Auto-obliteration by volcanism of all craters larger than ～200 km would explain their anomalous absence on Earth compared with other terrestrial planets in the solar system.
机译：我们将流体动力学模型与有关地幔融化行为的已知数据结合使用，以检查在大型地面撞击坑下方岩石圈减压融化的潜力。该机制可以产生足够量的熔体以自动堵塞火山口。融化几乎是在瞬间开始的，但是如此大规模的地幔融化的影响可能会触发长期存在的地幔上升流，这可能类似于地幔热点。减压熔化是众所周知的。这是地球物理学家提倡的在地球上融化的主要方法，无论是由岩石圈变薄还是由热的地幔羽流引起的。释放的能量主要来自重力能量，并且在冲击建模的常规计算之外（但附加），在常规计算中，能量仅从撞击的弹丸（无论是彗星还是小行星）的动能中得出。总熔体体积和弹坑尺寸之间的经验相关性将不再适用，而是主要在岩石圈的热结构上，在某个阈值尺寸以上将出现不连续性。我们估计，直径为20 km的铁质撞击器以10 km / s的速度行进时产生的熔体量可能与陆地大火成岩省（〜10〜6 km〜3）的熔体特征量相当; Roddy等人也模拟了海洋作用下地幔的类似融化。 [Int。 J.影响工程。 5（1987）525]。地幔熔体将具有类似于羽状的地球化学特征，并且可能会从水平下火山口储层快速混合熔体。因此，对于地质记录中的全球地层事件，影响和火山作用之间的直接耦合是一种实际可能性。我们建议，由于在〜250 Ma发生重大影响，应重新考虑二叠纪末期的西伯利亚圈闭。火山作用自动吹扫所有大于200 km的陨石坑，可以解释它们与太阳系中其他陆地行星相比在地球上的异常缺失。

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