Quantifying Carbon in the Mantle Lithosphere: Concentration, sources, and forms of carbon stored in carbonates and fluid inclusions

碳是地球上最重要的元素之一，因为它是所有生命的基础，它为人类文明提供燃料，并调节气候。在地球表面，碳在大气、陆地生物圈、海洋和沉积物之间交换。地球表面碳交换的时间尺度和数量有很好的特征。然而，地球表面的碳只占地球总碳收支的1%。地球上绝大多数的碳（约99%）存在于它的内部（地幔和地核），这使得它的研究更具挑战性。为了更好地了解地球内部碳在地质时期对气候和生命的长期贡献，我们必须提高对地球深层碳的理解。该项目将支持一名博士后学者探索这一主题。在拟议的研究中，这一重大知识缺口将通过确定地球内部岩石（由火山采样）中储存的碳量来解决，即捕虏体。通过对这些捕虏体中的碳酸盐和流体包裹体的分析，利用碳、氧同位素更好地约束地幔岩石圈中碳的丰度、来源和储存形式，确定流体包裹体的包裹体温度和组成，并通过岩石圈地幔条件下流体包裹体化学的理论热力学模型研究包裹体温度下含水碳的形态。这项研究将为地幔中碳的数量和来源提供急需的限制，特别是针对来自美国西南部的样本。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Carbon is one of the most important elements on Earth, as it is the basis of all life, it fuels human civilization, and modulates climate. On Earth’s surface, carbon is exchanged between the atmosphere, terrestrial biosphere, oceans, and sediments. The timescales and amount of carbon exchanged on Earth’s surface are well characterized. However, the carbon on Earth’s surface makes up only ~1% of Earth’s total carbon budget. The vast majority of Earth’s carbon (~99%) is found in its interior (mantle and core), making it much more challenging to investigate. To better understand the long-term contribution of Earth’s interior carbon to climate and life through geologic time, our understanding of Earth’s deep carbon must be improved. This project will support a postdoctoral scholar while she explores this topic.In the proposed study, this significant gap in knowledge will be addressed by determining the amount of carbon stored in rocks from Earth’s interior (sampled by volcanoes), namely xenoliths. Through the analysis of carbonates and fluid inclusions hosted in those xenoliths, the PI will better constrain the abundance, sources, and forms of carbon stored in the mantle lithosphere using carbon and oxygen isotopes, determining the entrapment temperature and composition of fluid inclusions, and investigating aqueous carbon speciation at entrapment temperatures by theoretical thermodynamic modeling of fluid inclusion chemistry at lithospheric mantle conditions. This study will provide much needed constraints on the amount and sources of carbon in the mantle, specifically targeting samples from the southwestern United States.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.