Carbon Isotope Exchange Between Carbonates and Graphite

岩石在地球表面和内部之间的循环影响着从地壳和地幔的演化到大气组成的一切。为了量化在岩石俯冲和折返过程中发生的过程，地球科学家使用了一系列工具，其中最重要的是稳定同位素的分布。碳的稳定同位素分馏随温度变化显著。方解石和石墨之间的碳同位素分布特别重要，因为它有可能提供关于变质过程的温度信息。二次离子质谱仪的最新发展使人们对变质过程中的石墨沉淀有了新的认识，并有望促进我们对变质过程的温度和速度的理解。然而，这些解释依赖于在重要的温度和压力范围内外推的石墨生长数据，以及未经实验验证的经验校准的分馏关系。这项工作将为这些因素提供直接的实验测量，并将有助于理解地球内部的循环过程。

DeinesEAR-0229551The cycling of rocks between the Earth's surface and interior affects everything from the evolution of the crust and mantle to the composition of the atmosphere. To quantify the processes occurring during subduction and exhumation of rocks, geoscientists utilize a broad range of tools, one of the most important of which is the distribution of stable isotopes. The fractionation of stable isotopes of carbon changes significantly with temperature. The carbon isotope distribution between calcite and graphite is particularly important because it has the potential to provide temperature information about metamorphic processes. Recent developments in secondary ion mass spectrometry have lead to new insights into graphite precipitation during metamorphism and hold promise to advance our understanding of the temperatures and rates of metamorphic processes. However, these interpretations rely on graphite growth data that has been extrapolated over significant temperature and pressure ranges, as well as empirically calibrated fractionation relationships that have not been experimentally verified. This work will provide direct experimental measurements of these factors, and will help understand the cycling process within the Earth.