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。地壳形成了板块的顶部，并随板块一起移动。有两种类型的地壳：海洋盆地下的地壳（海洋地壳）和组成大陆的地壳（大陆地壳）。当板块被地幔在地球表面的运动所携带时，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死亡。在整个历史中，浮力强的大陆通常停留在地球表面，而海底则被带往（俯冲）到地球内部深处。但阿尔卑斯山脉和喜马拉雅山脉的高山、阿曼沙漠和挪威西部峡湾的岩石却记录着另一个故事——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，在大陆岩石板块中结晶的稀有和外来矿物的发现表明，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。而那些被挤压到大陆岩石上的古海底碎片的保存表明，并不是所有的海洋地壳物质都被破坏了。只有当山带开始上升时，大陆地壳俯冲和海洋地壳保存的非凡结合才会发生：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如何随时间变化的科学家也很重要。随着山脉的上升，它们对大量富含水分的空气形成了屏障，并在其背后形成了雨影。因此，山带上升的速度及其对当地和全球气候的影响速度对模拟当今气候变化速度具有重要意义。这项研究的目的是精确详细地分析，深俯冲的大陆地壳板块上升到地表需要多长时间，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。测定某些矿物微观碎片年代的新技术可以为这些事件提供时间尺度。矿物的化学成分也提供了这些岩石结晶时的温度和压力的线索，以及它们从地壳中回升时的温度-压力历史。这些信息将帮助我们更详细地了解山带形成和上升的速度。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研究结果进行比较，以了解地形上升与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.