Sediment-peridotite interaction in a temperature gradient: transport of trace elements and growth of diamonds

俯冲带具有非常复杂的成分和热结构。板幔并置相对较冷的沉积物与较热的地幔橄榄岩。下行板块和上覆地幔楔之间的物质传递过程是我们理解地球深部元素循环和弧岩浆生成的基础。在以前的一个项目中，研究了在7.5-10 GPa下温度梯度对沉积物-橄榄岩相互作用的影响。在这些复杂的实验中观察到岩石学和主要元素组成的一些变化作为温度梯度和时间的函数。该项目是前一个项目的延伸，我们的目标是通过分析矿物和沉积物橄榄岩相互作用过程中产生的不同矿物层的微量元素组成，更详细地研究传质。几个新的实验将进行单独的沉积物混合物（K-GLOSS）在一个可比的温度梯度，为我们提供更好的边界条件，我们的元素输运建模。该组合物代表俯冲沉积物，含有H2O，碳酸盐和石墨，并掺杂有微量元素，将通过LA-ICP-MS测量。将进行几个额外的实验，以进一步研究金刚石在复杂的化学和热梯度中的成核和生长。最近的经验表明，需要比以前的实验稍高的温度来促进整个样品中金刚石的自发成核

Subduction zones have a very complex compositional and thermal structure. The slab-mantle juxtaposes relatively cold sediment with hotter mantle peridotite. Mass transfer processes between the downgoing slab and the overlying mantle wedge are fundamental to our understanding of deep-Earth element cycling and the generation of arc magmas. In a previous project, the effect of a thermal gradient on sediment-peridotite interaction at 7.5-10 GPa was investigated. A number of changes in petrology and major element composition were observed in these complex experiments as a function of temperature gradient and time. This project is an extension of the preceding project where we aim to investigate mass transfer in more detail by analyzing trace element compositions of the minerals and different mineralogical layers produced during sediment-peridotite interaction. Several new experiments will be carried out with the sediment mixture (K-GLOSS) alone in a comparable temperature gradient to provide us with better boundary conditions for our element transport modeling. This composition represents a subducting sediment and contains H2O, carbonate and graphite and is doped with trace elements that will be measured by LA-ICP-MS. Several additional experiments will be performed to further study the nucleation and growth of diamond in complex chemical and thermal gradients. Recent experience has indicated that somewhat higher temperatures than previous experiments are needed to promote spontaneous nucleation of diamond throughout the sample