Hydrous alkali-silicate liquids at the magmatic-hydrothermal transition

这项建议侧重于具有最高H2O溶解度和最低固相线温度的碱-硅酸盐液体。这些液体的性质是有争议的。它们被认为是熔体、浓缩水溶液或胶体凝胶。然而，它们能够结晶常见的形成岩石的硅酸盐，如长石和石英，因此可以被认为是可信的岩浆液体。天然碱性硅酸盐液体可能在长英质侵入岩中岩浆结晶的最后阶段、地壳深熔过程中发挥重要作用，也可能在俯冲带岩浆作用中形成。该项目包括合成系统的全面实验研究，涉及实验和分析方法(水热金刚石砧座、原位拉曼光谱、激光烧蚀电感耦合等离子体质谱)，其中一些方法，如超声波光谱，据我们所知，以前从未应用于富水的碱性硅酸盐液体。通过使用新的工具，我们期望解决关于无定形硅酸盐相性质的争议，特别是研究它们在岩浆-热液转变期间的地质系统中的作用。该项目旨在从碱性硅酸盐液体中了解伟晶岩形成的重大突破，并对大陆地壳和岩石圈地幔中的流体诱导熔融具有更广泛的意义。水含量大的无定形硅酸盐材料(液体、玻璃或胶体)可以为挥发分在硅酸盐熔体中的溶解机理提供新的线索，也是材料科学的研究热点。

This proposal focuses on alkali-silicate liquids with the highest solubility of H2O and the lowest solidus temperatures. The nature of these liquids is contentious. They are considered either as melts, or concentrated aqueous solutions, or colloidal gels. However, they are able to crystallise common rock-forming silicates, such as feldspars and quartz, and thus can be regarded as plausible magmatic liquids. Natural alkali silicate liquids are likely to play an important role at the final stages of magma crystallisation in felsic intrusions, during anatectic melting of the crust and they may also form in subduction zone magmatism. The project includes comprehensive experimental studies in synthetic systems, and involves experimental and analytical methods (hydrothermal diamond anvil cells, in situ Raman spectroscopy, laser ablation ICP-MS), some of which, such as ultrasonic spectroscopy, were never applied, as far as we know, to water-rich alkali-silicate liquids before. By using new tools, we expect to resolve the controversy regarding the nature of the amorphous silicate phases and particularly examine their role in geologic systems at the magmatic-hydrothermal transition. The project aims at a major breakthrough in understanding pegmatite formation from alkali silicate liquids and has broader implications for fluid-induced melting in continental crust and lithospheric mantle. Amorphous silicate materials (liquid, glassy or colloidal) with large contents of water may shed new light on solubility mechanisms of volatiles in silicate melts and are also of great interest to material science.