______________ alters the mineralogical composition of rocks at depth in areas of circulating hydrothermal fluid.

Metamorphism alters the mineralogical composition of rocks at depth in areas of circulating hydrothermal fluid.

Here are the steps explaining how this process occurs:

1. Heat and Pressure: The process begins when rocks are subjected to high heat and pressure, which is common at great depths below the Earth's surface. This can also occur where tectonic forces cause a collision of the Earth's crust.

2. Circulating Hydrothermal Fluid: In these high-pressure and high-temperature conditions, there is often circulating hydrothermal fluid. This fluid can be water that has seeped down from the surface or released from the rock due to the high temperature.

3. Chemical Reactions: The heat, pressure, and hydrothermal fluids can cause chemical reactions that change the mineralogical composition of the rock. This can result in the formation of new minerals that are stable under these new conditions.

4. Metamorphic Rock Formation: The original rock, or parent rock, transforms into a new type of rock called a metamorphic rock. This rock has a different mineralogical composition and often a more compact and harder structure.

5. Uplift and Erosion: Over time, these metamorphic rocks can be uplifted to the Earth's surface through geological processes such as mountain building. Erosion can then wear away the overlying rock, revealing the metamorphic rock below.

In summary, the process of metamorphism alters the mineralogical composition of rocks at depth in areas of circulating hydrothermal fluid.