Volatile Recycling at the Lesser Antilles Arc: Processes and Consequences

小安的列斯群岛弧的挥发性回收：过程和后果

基本信息

批准号：
NE/K010662/1
负责人：
Jonathan Blundy
金额：
$ 14万
依托单位：
University of Bristol
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2015
资助国家：
英国
起止时间：
2015 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FK010662%2F1
关键词：
Volatile Recycling Lesser Antilles Arc

项目摘要

The Earth is unique in our solar system in having abundant liquid water, plate tectonics and life. These properties are not unconnected; The evolution of life has depended heavily on water, and water is pumped around the planet by the plate tectonic cycle. Plate tectonics in turn, and its capacity to generate the very continents on which we live, also depends on the existence of water.Subduction zones are the most important "valve" in the plate tectonic system. They form where tectonic plates sink back into the mantle. Here water, along with other volatiles such as carbon dioxide and sulphur, are returned to the deep interior. However, the return is not wholesale. As the sinking plate is subjected to heat and pressure, a large fraction of the incoming volatiles is "sweated off" and added to the overlying mantle where it causes melting. These melts feed volcanoes at subduction zones which are characteristically dangerously explosive. When considered with the earthquakes triggered by the plates scraping past each other and the consequent tsunamis and landslides, it is clear that subduction zones are the most hazardous places on Earth. Yet, these regions also have benefits: the cocktail of fluids travelling with magmas at subduction zones is responsible for transporting and emplacing valuable metal deposits into the crust, and the fine ash distributed by the explosive volcanoes produces nutrient-rich, fertile soils.The importance of cycling volatiles through subduction zones is self-evident. However we still don't really know how it works and what the budgets are of volatiles delivered to the subduction zone, versus those recycled into the lithosphere, hydrosphere and atmosphere compared with those sequestered back into the deep mantle.We propose an innovative multidisciplinary experiment to track volatiles at a subduction zone. Questions to be answered include: How do volatiles influence the types and amounts of magmas generated? How do they control where volcanoes, such as Mt Pinatubo and Montserrat are located and how explosive they are? How do volatiles dictate where ore deposits are formed? How do volatiles mediate the seismogenic behaviour of subduction zones - whether there are large "megathrust" earthquakes like Japan and Sumatra or whether slip is less violent?Our focus area is the Lesser Antilles Arc, which is a special case, because it is one of only two Atlantic subduction zones. Plate formation processes at the slowly-spreading mid-Atlantic ridge produce a much more pervasively hydrated plate than those in the extensively studied Pacific. Furthermore, a laterally varying capacity to carry water in the plate and sediments subducting below the Antillean arc are a likely culprit for the arc's highly variable style and intensity of seismic and volcanic activity. By mapping structural differences along the arc we will be able to pinpoint the effects of variable water input. We plan to use novel seismic approaches complemented by geochemical analyses and integrated using numerical models to identify and quantify where volatiles are in the downgoing plate, where they are released at depth, and how they are transported from the subducting plate through the mantle wedge to the arc. We will use a unique suite of rocks from deep in the crust which have been carried up in volcanoes to help us understand how magmas evolve, and what allows them to concentrate ore metals. Mapped water pathways will be compared with seismic and volcanic activity, as well as with those inferred at other subduction zones.This large research project will be "bookended' on the one hand by an enormous amount of resource; data, samples, expertise and results from previous studies that will provide excellent value for money, and on the other hand a special focus on the societal benefits; informing natural hazard planning, and a better appreciation of how and where economic deposits form.

在我们的太阳系中，地球在拥有丰富的液态水，板块构造和生命方面是独一无二的。这些属性不是没有连接的；生命的演变很大程度上取决于水，并且通过板块构造周期在行星周围抽水。板块构造依次及其生成我们居住的大陆的能力也取决于水的存在。提包区是板块构造系统中最重要的“阀门”。它们形成了构造板沉入地幔中的地方。这里的水以及其他挥发物（如二氧化碳和硫）都将返回到深内部。但是，回报不是批发。由于下沉板受到热量和压力的影响，因此传入的挥发物的很大一部分被“汗水掉下来”，并将其添加到上面的地幔中，导致熔化。这些融化在俯冲带中为火山提供了特征危险爆炸性的俯冲带。当用板触发的地震以及随之而来的海啸和滑坡触发的地震触发时，很明显，俯冲带是地球上最危险的地方。然而，这些区域也有好处：俯冲带在俯冲带中旅行的液体鸡尾酒负责将有价值的金属沉积物运输到地壳中，以及由爆炸性火山分布的细灰产生富含营养的肥沃土壤，肥沃的土壤。但是，我们仍然不知道它是如何工作的，以及向俯冲带的挥发带的预算是什么，而与隔离层，水圈和大气相比，与隔离到深层地幔相比，我们提出了一个创新的多学科实验，以跟踪俯冲区的挥发性挥发物。要回答的问题包括：挥发物如何影响产生的岩浆的类型和数量？他们如何控制火山（例如Pinatubo和Montserrat的位置）以及它们的爆炸性如何？挥发物如何决定在哪里形成矿石？挥发物如何介导俯冲带的地震生成行为 - 是否存在像日本和苏门答腊这样的大型“巨型”地震，还是滑倒较少？我们的重点区域是否较小的安泰氏菌ARC，这是一种特殊情况，因为它是仅有的两个大西洋俯冲区域之一。与广泛研究的太平洋地区相比，在缓慢扩展的中大西洋山脊上的板块形成过程可产生更加普遍的水合板。此外，横向变化的能力在板上载水和安提亚弧下方的沉积物俯冲，这可能是ARC高度可变风格以及地震和火山活动强度的罪魁祸首。通过绘制沿弧的结构差异，我们将能够查明可变水输入的影响。我们计划使用通过地球化学分析补充的新型地震方法，并使用数值模型进行整合，以识别和量化挥发物在下板中的位置，深度释放，以及如何从横冲板通过披风楔传递到ARC。我们将使用来自地壳深处的独特岩石套件，这些岩石已在火山中携带，以帮助我们了解岩浆的发展方式，以及什么使它们能够集中矿石金属。映射的水路路径将与地震和火山活动以及在其他俯冲区推断的水路进行比较。该大型研究项目将“一方面预订”，这是一方面的大量资源；数据，样本，专业知识和先前研究的结果，这些研究将带来良好的货币价值，另一方面是对社会收益的特殊焦点；从而使自然界和自然范围的计划都可以很好地构成；以及如何获得自然的计划和自然范围和一项自然范围和一项自然范围的信息。