This proposal aims to map high-pressure hydrous phases stable under Earth's mantle conditions, focusing on dense silicates in the Mg-Al-Si-O-H system, formed after the destabilization of water-bearing minerals in subduction zones. These phases are critical to understand the deep water cycle. Using advanced X-ray microdiffraction techniques at ID11, the study will analyze the structure and textural distribution of synthetic high-pressure phases, identifying new possible transient structures in complex systems that include calcium and iron. By linking atomic-scale processes to large-scale planetary dynamics like deep earthquakes, this research seeks to reveal the role of these phases in geodynamic phenomena and improve our understanding of mantle composition and fluid migration.