Final answer:
Metamorphic rocks undergo phase changes due to changes in temperature, pressure, or chemically reactive fluids. Geologists use mineral assemblages, textures, and geodynamic models to determine the sequence of phase changes and the associated tectonic conditions and depths.
Step-by-step explanation:
Metamorphism is the process by which a pre-existing rock, called a protolith, is altered by changes in temperature, pressure, or chemically reactive fluids. To determine the sequence of aluminosilicate phase changes in rock x and the tectonic conditions and depths at which they occurred, geologists construct geodynamic models and use mineral assemblages and textures as indicators.
Mineral assemblages in metamorphic rocks change with increasing temperature and pressure. For example, as temperature and pressure increase, clay minerals in the protolith can transform into mica minerals, and eventually into garnet or pyroxene minerals. These phase changes occur at specific temperature and pressure conditions, which are typically represented on a pressure-temperature (PT) diagram.
To determine the tectonic conditions and depths at which these phase changes occurred in rock x, geologists analyze the mineral assemblages and textures present in the rock. By comparing these observations to known PT diagrams and geodynamic models, they can estimate the temperature, pressure, and depth at which each phase change occurred.