Determining the origin and evolutionary history of volatiles on Earth

确定地球上挥发物的起源和进化历史

• 批准号: NE/X01732X/1
• 负责人: Michael Ward Broadley
• 金额: $ 99.41万
• 依托单位: University of Manchester
• 依托单位国家: 英国
• 项目类别: Fellowship
• 财政年份: 2024
• 资助国家: 英国
• 起止时间: 2024 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FX01732X%2F1
• 关键词: Determining; origin; evolutionary; history; volatiles

With its surface covered in liquid water, the Earth stands out amongst the other planets of the solar system as the only known haven capable of supporting life. But what makes the Earth so unique? And where did its life-supporting oceans and atmosphere originate? These are the fundamental questions that drive my scientific research.When Earth formed 4.5 billion years ago, the solar system was a very different, chaotic, place. The Earth grew from repeated collisions between kilometre-sized asteroids. These impacts would have generated huge amounts of energy that would have ejected the oceans and atmosphere in to space, leaving it dry and barren of the ingredients essential for life. So how the Earth became the volatile-rich planet we know today remains a mystery.To understand how volatile elements arrived on Earth we need to looks for clues in their composition that could point us to their origin. However, the Earth's active geology and biology has wiped out any potential fingerprints that may have existed on the Earth's surface. Fortunately, deep inside the Earth's mantle there are regions that have remained isolated from the surface for billions of years, and still retain the information needed to solve the mysterious origin of Earth's volatiles. I therefore plan to analyse the composition of volatiles trapped in volcanic rocks and ancient diamonds erupted from deep within the Earth. This research will shed new light on, how and when, volatiles arrived on Earth, and evaluate how geological processes redistributed these volatiles throughout Earth's history. More specifically it will enable three central questions concerning the Earth's volatile cycle to be addressed 1) What is the origin of volatiles trapped within the mantle, and did Earth acquire volatiles from multiple different sources? Noble gases are inert volatile elements that show resolvable isotopic and elemental differences between different accretionary sources (solar, chondritic, cometary, etc.) making them key tools for understanding the origin of volatiles on Earth. By analysing noble gas isotopes within basaltic glasses I will attempt to reveal the origin of volatiles in Earth's mantle and provide a better understanding on the where exactly in the solar system did the Earth's volatiles originate.2) When did volatiles first started being recycled to the mantle, and how has the process of subduction modified the mantle volatile budget through time? The Earth's surface environment and climate is modulated by the movement of volatiles such as water, carbon and nitrogen between the atmosphere and the mantle. The main process through which volatiles are introduced to the mantle is through subduction. This process is unique to the Earth and may have been key in preventing the runaway greenhouse conditions that affected our neighbouring planet Venus. However despite the important role volatile subduction plays in controlling the habitability of the Earth it is not currently well understood when this return flux of volatiles to the mantle commenced. In this project I will analyse volatiles in ancient diamonds to search for signs of ancient subduction and determine when and to what extent volatiles started being returned to the mantle. 3) Does subduction heterogeneously recycle different volatiles in to the mantle? From mass balance calculations at volcanic arcs it is known that at least some volatiles survive the subduction process and make it in to the mantle. However, how these volatiles are then distributed throughout the mantle is less well known. By combining the analysis of halogens and nitrogen with the heavy noble gases, which have an easily identifiable subducted signature I will determine to what extent halogens and nitrogen in the mantle have a recycled origin, and provide an insight into the mantle dynamics that control their distribution throughout the mantle.

它的表面被液态水覆盖，地球在太阳系的其他行星中脱颖而出，是唯一已知能够支撑生命的避风港。但是，是什么使地球如此独特？它的生命支持海洋和氛围在哪里？这些是推动我科学研究的基本问题。当地球形成45亿年前时，太阳系是一个非常不同的，混乱的地方。地球从千数小行星之间反复碰撞而生长。这些影响会产生大量的能量，这些能量将使海洋和气氛在太空中弹出，从而使其干燥和贫瘠的生命成分。因此，我们今天知道的地球如何变成一个挥发性富裕的星球仍然是一个谜。要了解挥发性元素如何到达地球上，我们需要在其构图中寻找可以将我们指向其起源的线索。但是，地球的活跃地质和生物学已经消除了地球表面上可能存在的任何潜在指纹。幸运的是，在地球地幔的深处，有数十亿年与地面隔离的地区，仍然保留了解决地球挥发物神秘起源所需的信息。因此，我计划分析被困在火山岩和古老钻石中的挥发物的组成。这项研究将阐明挥发物在地球上的新启示，如何以及何时到达，并评估地质过程如何在地球历史上重新分布这些挥发物。更具体地说，它将使有关地球挥发性周期的三个核心问题能够解决。贵重气体是惰性的挥发性元素，显示出可分离的同位素和元素差异（太阳能来源（太阳能，软骨，彗星等）），使其成为理解地球上挥发物的起源的关键工具。通过分析玄武岩眼镜中的贵重同位同位素，我将试图揭示地球上挥发物的起源，并更好地了解地球挥发物的确切位置。地球的表面环境和气候受到大气和地幔之间的挥发物的运动，例如水，碳和氮的运动。挥发物被引入地幔的主要过程是通过俯冲。这个过程是地球独有的，可能是防止影响我们邻近星球金星的失控温室条件的关键。然而，尽管挥发性俯冲在控制地球的可居住性方面发挥了重要作用，目前尚未充分理解，当挥发性向地幔的浪潮返回时。在这个项目中，我将分析古代钻石中的挥发物，以寻找古代俯冲的迹象，并确定何时以及在多大程度上开始将挥发物恢复到地幔。 3）俯冲是否异质地回收不同的挥发物中的地幔？从火山弧的质量平衡计算中可以知道，至少某些挥发物可以在俯冲过程中生存并将其进入地幔。但是，这些挥发物如何在整个地幔中分布不太鲜为人知。通过将卤素和氮的分析与沉重的贵重气体结合在一起，这些气体具有易于识别的俯冲签名，我将确定地幔中的卤素和氮在多大程度上具有回收的起源，并提供了对地幔动态的洞察力，可以控制其整个地幔的分布。