Investigating the relationship between pluton growth and volcanism at an active intrusions in the central Andes

岩浆是如何形成并与周围岩石相互作用的，是地球科学研究的中心问题。岩浆侵入地壳在大陆地壳动力学和演化中起着重要作用。在许多情况下，岩浆向上汇集，并在地球表面的火山上喷发，特别是在构造板块碰撞的地区。安第斯山脉是这样一个碰撞带的一部分，在那里，由于侵入的深层岩浆的化学演化以及周围岩石的部分熔化，形成了大型岩浆体（岩基）。安第斯山脉火山活动的一种常见形式是数百到数千立方公里的岩浆以火成岩（含有火山灰和浮石的火山岩）的形式灾难性地喷发，这通常会导致岩浆房顶部在喷发时坍塌，留下或多或少直径达数公里的环状表面洼地。该项目的动机是由星载卫星获得的结果表明，玻利维亚乌图伦库火山安第斯山脉中部的地面变形和明显的隆起，岩浆可能在那里积聚了27万年。人们怀疑这种膨胀是由一个巨大的岩浆体在深处的生长引起的。如果这种解释是正确的，那么这些异常就提供了一个很好的机会来回答一些问题，比如大型岩浆体是如何在地壳中聚集形成岩体的，它们是如何演化的，它们与一般的火山活动有什么关系，它们是如何在地球表面表现出来的，可能是在喷发之前。我们的目标是通过协调、综合的方法，跨越地球科学的各个学科，找到这些问题的答案。这个雄心勃勃的项目的核心是大地测量学、地球物理学、地质学、岩石学和数学模型的融合，以实时记录岩体的生长。拟议工作的意义包括评估岩体在大陆动力学中的作用和大型火山爆发的可能性。我们要求为英美合作项目的英国部分提供资金，该项目还涉及来自西班牙、智利和玻利维亚的合作伙伴。我们建议对乌图伦库隆起进行综合考察，以检验岩体生长的假设，记录生长的动力学，并探索岩体作用、火山作用和构造作用之间的联系。研究的核心将是为期4年的地球物理实验，研究地面变形、质量变化和地震活动，并对火山下的地下结构进行成像。地球物理实验将辅以地质和岩石学调查以及数学建模，将地球物理实验置于火成岩过程和长期岩浆演化的背景下。这项研究的一个关键成果将是新一代的数学模型，这些模型将告诉我们岩浆房的规模是如何增长的，以及我们可能期望在地球表面记录哪些大地测量或地球物理信号。我们将通过分离（热）水和气体的浅层运移和深部岩浆的补充和淤积对地球物理信号的贡献，量化导致地面膨胀的源的性质。我们也有兴趣找出这些储层的位置，有多少，以及它们与过去导致火山喷发的岩浆房的深度有什么关系。对于后者，熔岩形态研究和岩石学将使我们深入了解这些岩浆房的条件。我们的目标是建立嵌入大陆地壳的岩浆系统的先进模型，包括地壳的可变力学特性，更深地壳的塑性变形以及气体饱和岩浆的结晶和浅层热液系统对地面变形的影响等复杂性。

How magma is emplaced and interacts with its surrounding rock is of central interest in the Earth Sciences. The intrusion of magma into the Earth's crust plays a major role in the dynamics and the evolution of continental crust. In many cases magmas are funnelled upwards and erupt at volcanoes that dot the Earth's surface, particularly in areas where tectonic plates collide. The Andes are part of such a collision zone where large magma bodies (batholiths) form, due to chemical evolution of intruding deeper magma as well as partial melting of surrounding rocks. A common style of volcanic activity in the Andes is the catastrophic eruption of many hundreds to thousands of cubic kilometres of magma in the form of ignimbrites (volcanic rock containing ash and pumice) which often results in the collapse of the magma chamber roof upon eruption, leaving behind more or less ring-shaped surface depressions with diameters of many kilometres. The project is motivated by results obtained from space-borne satellites indicating ground deformation and significant uplift at in the central Andes at Uturuncu volcano, Bolivia, where magma may be accumulating for 270 thousand years. It is suspected that this inflation is caused by the growth of a large magma body at depth. If this interpretation is correct then these anomalies provide an outstanding opportunity to answer questions such as how large magma bodies are assembled in the crust to form plutons, how they evolve, how they relate to volcanism in general and how they manifest at the Earth's surface, potentially before eruption. We aim to find answers to these questions via a coordinated, integrated approach across various disciplines of the Earth Sciences. Central to this ambitious project lies the amalgamation of geodesy, geophysics, geology, petrology and mathematical modelling to document pluton growth in real time. The implications of the proposed work include assessing the role of plutons in continental dynamics and the potential for large volcanic eruptions. We requests funds for the UK component of a collaborative UK-US project, which also involves partners from Spain, Chile and Bolivia. We propose an integrated investigation of the Uturuncu uplift to test the hypothesis that pluton growth is occurring, to document the dynamics of growth, and to explore the links between plutonism, volcanism and tectonics. The core of the study will be a geophysical experiment over a 4-year period to study the ground deformation, mass changes and seismicity, and to image the sub-surface structure beneath the volcano. The geophysical experiment will be complemented by geological and petrological investigations as well as mathematical modelling to set the geophysical experiment in the context with igneous processes and the long-term magmatic evolution. A key outcome of the research will be a new generation of mathematical models to inform on how large magma chambers grow and which geodetic or geophysical signals we might expect to record at the Earth's surface. We will quantify the nature of the sources responsible for ground inflation by separating the contributions of shallow migration of (hot) water and gases, and deep magma replenishment and ponding, to geophysical signals. We are also interested to find out where these reservoirs are located, how many there are and how they relate to the depth of magma chambers that have led to eruptions in the volcano's past. For the latter, lava morphology studies and petrology will give insights onto the conditions in these magma chambers. We aim at developing advanced models of magma systems embedded in continental crust incorporating complexities such as variable mechanical properties of the crust, plastic deformation of deeper crust as well as the influence of crystallization of gas-saturated magma and shallow hydrothermal systems on ground deformation.