Understanding Dolomitisation: Mechanisms, Settings, and Transformed Rocks

Dolomitisation is a process of mineral transformation that occurs when magnesium-rich fluids replace calcium ions in sedimentary rocks, causing the rock to transform into dolomite. This process can occur through a variety of mechanisms, including:

1. Diagenesis: Dolomitisation can occur during the early stages of rock formation, as a result of changes in the chemistry of the sedimentary material.
2. Hydrothermal activity: Magnesium-rich fluids can migrate through rocks and replace calcium ions, leading to dolomitisation.
3. Metasomatism: This is a process of chemical alteration that occurs when magnesium-rich fluids pass through rocks, replacing calcium ions and causing the rock to transform into dolomite.
4. Weathering: Dolomitisation can also occur as a result of weathering processes, such as dissolution of calcite and recrystallisation as dolomite.

Dolomitised rocks are those that have undergone this process of mineral transformation, resulting in the presence of dolomite as a major mineral component. These rocks can include limestones, sandstones, and other sedimentary rocks, and can be found in a variety of geological settings, including:

1. Carbonate platforms: These are shallow, marine environments where dolomite is deposited in large quantities.
2. Basins: Dolomitised rocks can also be found in basins, where they may have formed as a result of hydrothermal activity or metasomatism.
3. Faults: Dolomitisation can occur along faults, where magnesium-rich fluids can migrate through the rock and replace calcium ions.
4. Burial diagenesis: This is the process of dolomitisation that occurs during burial of sedimentary rocks, as a result of changes in the chemistry of the pore fluid.