Hydrothermal water carries minerals as it travels through the crust. These minerals are often deposited as pressure decreases as the fluid approaches the surface. These minerals and their formations may be evidence of past hydrothermal activity.
Examples of hydrothermal deposition include:
Quartz veining – quartz is often found filling small fractures as the result of fluid flow.
Calcium Carbonate – calcium carbonate is a common cement withing sedimentary matrices, resulting from fluid flow.
Structures such as sinter terraces and tufa mounds indicate extinct spectacular hot spring and fumarole features.
Borate Evaporite crusts.
Sulfur and Sulfides – sulfides are common crustal minerals often extracted and resdeposited by hydrothermal fluids.