Mobility of volatile (H2O & CO2)-bearing melts in the upper mantle: from carbonatite magmatism to the dynamics of kimberlitic eruptions

挥发物（H2O和CO2）在行星内部的内部动力学和热演化中起着关键作用，并定义了其表面的可居住性条件。因此，了解深层和表层储层之间挥发物的交换和通量仍然是地球科学界的主要目标。然而，这些过程的定量建模在很大程度上是有限的，缺乏基本的限制的流动性和迁移率的挥发性轴承熔体，这是主要的输送机的挥发物的分布。该项目通过将含挥发物熔体中的高压密度测量与热力学建模相结合，以定量了解地球内部的深层挥发性循环和相关地球物理过程，解决了这一关键的知识空白。在第一个资助期内，我们专注于富碳酸盐熔体，并限制了水合作用对碳酸盐熔体密度/流动性的影响，熔体中溶解挥发物的可压缩性以及从俯冲岩性中提取碳酸盐熔体的时间尺度。此外，我们校准了MgO-CaO-Na 2 O-K2 O-Li 2 O-H2O-CO2系统中碳酸盐熔体的第一个连续密度模型，其条件跨越地幔过渡带以外的岩浆过程，即高达30 GPa和2300 K。在成功的第一个供资期后，扩展项目将侧重于中等二氧化硅不饱和富碳熔体，与已被广泛研究的含挥发分的富二氧化硅熔体相比，在相关地幔条件下几乎没有密度数据。在上地幔条件下的碳酸盐岩和金伯利岩熔体的密度数据将使用同步加速器X射线吸收/射线照相和沉浮法在大容量的压力机相结合。新的密度数据将使碳酸盐熔体密度模型能够扩展为一个全球密度模型，适用于上地幔稳定的含挥发物熔体范围，即从碳酸盐（富CO2）到碳酸盐玄武岩（富SiO2熔体）。 新模型将允许预测含挥发分熔体的流动性，并模拟熔体通过地幔的迁移/上升/就位，包括含钻石金伯利岩喷发的动力学及其在固体地幔中的地球物理特征。 最终，该项目的结果将导致对地球深处挥发性流动性和再循环的新理解。

Volatiles (H2O and CO2) play a critical role in the internal dynamics and thermal evolution of planetary interiors, and define the habitability conditions at their surface. Understanding the exchanges and fluxes of volatiles between deep and surficial reservoirs thus remain a primary goal of the Earth Sciences community. Yet, the quantitative modelling of these processes is largely limited by the lack of fundamental constraints on the mobility and migration rates of volatile-bearing melts, that are the main conveyors for the distribution of volatiles. This project addresses this critical gap of knowledge by combining high pressure density measurements in volatile-bearing melts and thermodynamic modelling to gain quantitative insights into the deep volatile cycles and related geophysical processes inside the planet. During the first funding period, we focused on carbonate-rich melts and constrained the effect of hydration on the density/mobility of carbonate melts, the compressibility of dissolved volatiles in the melt and the timescale of carbonate melt extraction from subducted lithologies. Moreover, we calibrated the first continuous density model for carbonate melts in the system MgO-CaO-Na2O-K2O-Li2O-H2O-CO2 at conditions that span magmatic processes beyond the mantle transition zone, i.e. up to 30 GPa and 2300 K. After a successful first funding period, the extension project will focus on intermediate silica under-saturated carbon-rich melts for which density data is virtually not available at relevant mantle conditions in contrast to volatile-bearing silica-rich melts that have been extensively investigated. Density data in carbonatite and kimberlite melts at upper mantle conditions will be obtained using a combination of synchrotron X-ray absorption/radiography and sink-float methods in large volume presses. The new density data will enable the extension of the carbonate melt density model into a global density model for the range of volatile-bearing melts stabilized in the upper mantle, i.e. from carbonates (CO2-rich) to carbonated basalts (SiO2-rich melts). The new model will allow predictions of the mobility of volatile-bearing melts and modelling the migration/ascent/emplacement of melts through the mantle, including the dynamics of diamond-bearing kimberlite eruptions, and their geophysical signature in the solid mantle. Ultimately, the results of this project will lead to a new understanding of volatile mobility and recycling in the deep Earth.