Melting in the Deep Earth

地球的融化对其化学和物理状态有巨大的影响。例如，地壳、地幔和大气的化学成分在很大程度上是由大洋中脊、热点或岛弧的融化和结晶控制的。因此，在过去的几十年里，人们做出了巨大的努力来了解这些浅层融化过程。然而，更深的融化可能对地球的进化产生了同样的影响。例如，人们普遍认为，在地球历史的早期，存在一个可能延伸到地球中心的深部岩浆海。这是地球增生过程中多次撞击的结果。从岩浆海洋中，铁熔体与硅酸盐熔体分离形成地核，挥发物脱气形成早期大气，原始地壳可能已经形成。人们也接受地球被火星大小的天体撞击而形成月球的说法；这也会导致地球深处大量的融化。此外，现在有证据表明地球深处正在融化。因此，在地球的整个历史中，地球最深处的冰层可能一直存在。然而，关于深熔的物理和化学性质的许多基本数据并不存在。例如，我们不知道地幔矿物和岩石在地球深处的压力和温度下的融化曲线。我们不知道哪些矿物质首先从这些熔体中结晶（液态相）。我们不知道深部地幔岩石或已俯冲的岩石的部分熔体的成分。我们不知道岩石及其熔体的相对密度，因此我们甚至不知道矿物是漂浮还是下沉在这些深层熔体中。由于缺乏数据，人们对深度融化对地球演化的影响产生了许多猜测。例如，有人提出，地幔的地球物理和地球化学异常是由深部早期融化引起的。但这些模型依赖于熔体和结晶固体的化学和物理性质，这些性质根本不为人所知。这个项目将使用新颖的实验结合从头算模型来获得这些数据。这些数据将提供化学和物理基础，所有未来地球早期结晶和随后演化的模型都将以此为基础。

Melting in the Earth has a huge effect on its chemical and physical state. For instance, the chemistry of the crust, the mantle and the atmosphere are largely controlled by melting and crystalisation at mid-ocean ridges, hotspots or island arcs. There has, therefore, been an enormous effort in the last decades to understand these shallow melting processes. Yet much deeper melts may have been equally influential in the evolution of the Earth. For instance, it is generally accepted that a deep magma ocean perhaps extending to the Earth's centre, existed early its history. This was the result of multiple impacts as the Earth accreted. From this magma ocean, iron melts separated from silicate melts to form the core, volatiles degassed to form an early atmosphere, and a proto-crust may have formed. It is also accepted that the Earth was hit by a Mars-sized body to create the moon; this too would have caused enormous amounts of melting in the deep Earth. Moreover, there is some evidence for melting in the deep Earth now. It is possible, therefore, that melts in the deepest Earth have existed throughout Earth's history. However, many basic data on the physical and chemical properties of deep melting do not exist. For instance, we don't know the melting curves for mantle minerals and rocks at the pressure and temperatures of the deep Earth. We don't know which minerals crystalise from these melts first (the liquidus phases). We don't know the composition of partial melts of deep mantle rocks or rocks which have been subducted. We don't know the relative densities of the rocks and their melts, and so we do not even know whether minerals float of sink in these deep melts. This lack of data has led to much speculation on the effect of deep melts on the Earth's evolution. For instance, it has been suggested that geophysical and geochemical anomalies in the Earth's mantle have deep early melts as their origin. But these models depend of the chemical and physical properties of the melts and crystalline solids, properties that are simply not known. This project will use novel experiments in conjunction with ab initio modelling obtain these data. The data will provide the chemical and physical foundation on which all future models of the Earths early crystallization and subsequent evolution will be based.