Catastrophic emplacement and depositional processes during large asteroid impacts: lithofacies analysis and applied volcanology, Manicouagan (Canada)

当小行星或彗星与地球相撞时，它们会造成灾难性的冲击、蒸发、熔化、碎片和喷射，显著改变地壳，破坏环境和生物群。这种“超高速碰撞”是行星演化的基本过程，也可以说是最大的自然灾害。在冲击变质作用、岩石学和建模方面已经取得了重大进展，但对所发生的事情的几个地质方面仍然知之甚少。我们需要更好地了解熔融喷出物侵位的过程，以便解释更广泛的影响。信息的主要来源是地球的地质记录，但可获得的、保存完好的充满碎屑和熔融产物的大型撞击坑是罕见的，该项目将帮助破译地球上非常大的撞击坑中的撞击坑填充材料的碎裂和就位过程，重点是马尼夸根（加拿大）和希克苏鲁布（墨西哥）。两者都影响了大陆地壳，一个在陆地上，另一个在海上，两者都被钻探过。调查将记录，分析和解释陨石坑填充物，以揭示其形成的物理过程。学生将利用最先进的地质和物理火山学技术，了解热岩浆是如何破碎，就位，然后沉积和凝集在一起，形成厚的岩体，随后冷却，并以各种方式失透和结晶。一个目标是开发一个新的相计划，大型撞击坑填充，以帮助重建的事件，他们的形成。

When asteroids or comets collide with Earth they cause catastrophic shock, vaporisation, melting, fragmentation and ejection, significantly modifying the crust and devastating environments and biota. Such 'hypervelocity collisions' are a fundamental process of planetary evolution and arguably the greatest natural hazard. Significant advances in shock metamorphism, petrology and modelling have been made, but several geological aspects of what happens remain poorly understood. We need to better understand the processes of molten ejecta emplacement in order to account for the wider effects. A principle source of information lies in Earth's geological record, but accessible, well-preserved large impact craters filled with clastic and melted products are rare.This project will help decipher the fragmentation and emplacement processes of crater-fill material in very large impact craters on Earth, focussing on Manicouagan (Canada) and Chicxulub (Mexico). Both impacted continental crust, one on land the other at sea, and both have been drilled. The investigation will document, analyse and interpret the crater fills to shed new light on the physical processes of their formation. The student will draw upon state-of-the-art geological and physical volcanological techniques and understanding about how hot magma is fragmented, emplaced, and then deposited and agglutinated back together to form thick rock bodies that subsequently cool, and variously devitrify and crystallise. An objective is to develop a new facies scheme for large impact crater fills in order to help reconstruct the events by which they form.