Cratons are the oldest and most stable parts of the Earth's continental crust. They're like the ancient foundations of continents, formed billions of years ago. They are characterized by:
* Great thickness: Cratons can extend down to over 200km deep.
* Low density: Compared to other parts of the crust, they're lighter and less dense.
* Stability: They've remained relatively undisturbed for a long time, making them resistant to tectonic deformation.
Kimberlite pipes are volcanic conduits that carry magma from the Earth's mantle to the surface. These pipes are characterized by:
* Vertical shape: They are long, narrow, and vertical, resembling pipes.
* Explosive eruptions: They form when magma rises rapidly, leading to explosive eruptions that leave behind these distinctive pipes.
* Presence of diamonds: They bring diamonds from the deep mantle to the surface, making them a prime target for diamond mining.
The Link:
Diamonds are formed deep within the Earth's mantle, under intense pressure and heat. Cratons, with their immense depth and stability, provide the ideal environment for diamond formation. The exceptional depth and stability of cratons allow for diamond growth over millions of years.
Here's how kimberlite pipes play a crucial role:
1. Deep Origin: Kimberlite magma originates deep in the mantle, often from within the craton.
2. Rapid Ascent: The magma erupts explosively, bringing with it fragments of the mantle rock, including diamonds.
3. Surface Exposure: The volcanic eruption leaves behind the kimberlite pipe, filled with diamonds and other mantle minerals.
Diamond Discovery:
The unique composition and formation of kimberlite pipes made them a key to diamond discovery. Geologists learned to recognize these pipes by their distinctive characteristics:
* Unique mineral composition: Kimberlite is a dark, ultramafic rock with a specific mineral composition.
* Presence of mantle-derived minerals: They contain other rare minerals that originate from the mantle, serving as a signpost for diamond-bearing rocks.
Since diamonds are extremely rare and only form under specific conditions, finding a kimberlite pipe is like striking gold! These pipes became a primary target for diamond mining, leading to the discovery and extraction of some of the world's most famous diamonds.
In short, the combination of stable cratons, which provide the ideal environment for diamond formation, and explosive kimberlite pipes, which bring these treasures to the surface, has made these features crucial to diamond exploration and mining.
