Timing and mechanisms of the exhumation of deeply buried crust: The genesis of major mountain belts

就在50年前，许多地球科学家认为地球表面在不断运动的想法是荒谬的。现在很难找到一个不相信板块运动理论的地质学家。地壳构成了板块的顶部，并与板块一起移动。地壳有两种类型：洋盆之下的地壳(洋壳)和构成大陆的地壳(大陆壳)。随着板块在地球表面的下伏地幔运动中被携带，新的海洋在大陆分裂的地方诞生，旧的海洋在大陆碰撞的地方消亡。在整个历史中，浮力大陆通常留在地球表面，而洋底则被带到(俯冲)地球内部深处。但阿曼沙漠中阿尔卑斯山和喜马拉雅山的高山山脉以及挪威西部峡湾的岩石记录了另一个故事--一系列非同寻常的事件表明，大陆岩石和海洋岩石的命运截然不同。在这些地区，在大陆岩板内结晶的稀有和奇异矿物的发现表明，这些岩石是在非常高的压力下形成的--这是大陆物质俯冲的明确证据。而被压在大陆岩石上的古代海底切片的保存表明，并不是所有的海洋地壳物质都被摧毁了。大陆地壳俯冲和洋壳保存的非凡组合只有在山带开始上升时才会发生：这段时间不仅对对造山过程感兴趣的地质学家很重要，而且对研究全球气候随时间变化的科学家也很重要。随着山脉的上升，它们形成了一道屏障，阻挡了大量潮湿的空气，并在它们后面形成了一个雨影。因此，山脉地带上升的速度以及它们影响当地和全球气候的速度，对模拟当今的气候变化速度具有重要意义。这项研究旨在精确详细地分析深度俯冲的大陆地壳的板块重新浮回地表需要多长时间，以及这些板块何时被推到与今天发现的岩石相关的岩石旁边。对某些矿物的微观碎片进行测年的新技术可以为这些事件提供时间尺度。矿物的化学成分还提供了关于这些岩石结晶时的温度和压力以及它们在地壳中上升时的温度-压力历史的线索。这些信息将帮助我们更详细地了解山脉带形成和开始上升的速度。然后，我们可以将这些结果与其他科学家关于山带侵蚀速度的工作进行比较，以了解地形上升和当地或全球气候变化之间的滞后时间。

As little as 50 years ago, the idea that the surface of the earth was in constant motion was considered ludicrous by many earth scientists. Now it would be difficult to find a geologist who does not believe in the theory of moving plates. The Earth's crust forms the top part of the plates and moves with them. There are two types of crust: the crust beneath the ocean basins (oceanic crust) and the crust that makes up the continents (continental crust). As the plates are carried by the motion of the underlying mantle over the face of the earth, new oceans are born where continents split apart and old oceans die where continents collide. Throughout this history, the buoyant continents have usually remained at the earth's surface, whereas the ocean floor has been carried down (subducted) deep into the Earth's interior. But rocks in the high mountain chains of the Alps and Himalayas, in the deserts of Oman, and the fjords of Western Norway record another story - an extraordinary sequence of events that suggest an altogether different fate for both continental and oceanic rocks. In these regions, the discovery of rare and exotic minerals that have crystallised within slabs of continental rocks indicate that these rocks formed at very high pressures - clear evidence for the subduction of continental material. And the preservation of slices of ancient ocean floor which were forced up onto continental rocks indicates that not all oceanic crustal material is destroyed. The extraordinary combination of continental crust subduction and oceanic crust preservation only occurs when mountain belts start to rise: a period of time which is important not only to geologists interested in mountain building processes, but also to scientists who study how global climate has changed over time. As mountains rise, they form a barrier for masses of moisture-laden air, and create a rain shadow behind them. The rate at which mountain belts rise, and the rate at which they affected local and global climate, therefore has important implications for modelling the present-day rate of climate change. This research aims to analyse, in precise detail, how long it took for slabs of deeply subducted continental crust to rise back up to the surface, and when these slabs were pushed up next to the rocks they are found associated with today. New techniques of dating microscopic fragments of certain minerals can provide timescales for these events. The chemical composition of the minerals also yields clues about the temperatures and pressures under which these rocks crystallised, and their temperature-pressure history as they rose back through the crust. This information will help us understand in greater detail how quickly mountain belts form and start to rise. We can then compare these results with other scientists' work on how quickly mountain belts erode in order to understand the lag-time between topographic rise and local or global climate change.