Diamonds are formed deep within the Earth’s mantle, where they are subjected to high pressure and temperature conditions that are necessary for their creation. However, the rocks that carry diamonds to the Earth’s surface are relatively rare and are found in specific geological environments. In this article, we will discuss the types of rocks that can carry diamonds and the geological settings where they can be found.
Kimberlite and Lamproite Rocks
The two main types of rocks that can carry diamonds are kimberlite and lamproite rocks. These rocks are volcanic in origin and are formed from magma that originates deep within the Earth’s mantle. Kimberlite and lamproite rocks are unique in that they contain xenoliths or fragments of rock that have been carried up from the Earth’s mantle to the surface. Diamonds are found in these rocks as inclusions or small crystals within the xenoliths.
Kimberlite is the more common of the two types of rocks that can carry diamonds. It is a volcanic rock that is rich in magnesium, iron, and potassium. Kimberlite rocks are typically found in ancient cratons, which are stable geological regions that have not experienced tectonic activity for billions of years. Cratons are found in many parts of the world, including Canada, Southern Africa, Russia, and Australia. In fact, the majority of the world’s diamonds are produced from kimberlite mines located in these regions.
Lamproite is a less common type of rock that can carry diamonds. It is also a volcanic rock that is rich in magnesium, iron, and potassium, but it has a lower silica content than kimberlite. Lamproite rocks are found in younger geological settings than kimberlite rocks and are typically associated with volcanic activity that has occurred in the last 30 million years. Lamproite deposits are found in several countries, including Australia, Russia, India, and the United States.
Other Rocks that can Carry Diamonds
While kimberlite and lamproite rocks are the most common types of rocks that can carry diamonds, there are other rocks that can contain diamonds as well. These include:
- Eclogite: Eclogite is a high-pressure, high-temperature metamorphic rock that is formed from basaltic rocks that have been subjected to extreme heat and pressure. Eclogite can contain diamonds as inclusions within garnet crystals. Eclogite is typically found in subduction zones, where one tectonic plate is forced beneath another.
- Peridotite: Peridotite is a rock that is rich in the minerals olivine and pyroxene. It is one of the main components of the Earth’s mantle and can contain diamonds as inclusions. Peridotite can be found in many geological settings, including cratons, subduction zones, and mid-ocean ridges.
- Kimberlitic Indicator Minerals: Kimberlite and lamproite rocks are associated with a range of minerals that can indicate the presence of diamonds. These minerals are typically formed under high-pressure and high-temperature conditions, similar to those required for diamond formation. Some of the most common indicator minerals include garnet, ilmenite, and chrome diopside.
Geological Settings for Diamond Formation
In addition to understanding the types of rocks that can carry diamonds, it is important to understand the geological settings where diamonds are formed. Diamonds are typically formed in regions where the Earth’s mantle is subjected to high pressure and temperature conditions. The most common settings for diamond formation include:
- Subduction Zones: Subduction zones occur where one tectonic plate is forced beneath another. The heat and pressure generated in these regions can create the conditions necessary for diamond formation.
- Cratons: Cratons are large regions of the Earth’s crust that have not experienced tectonic
