Kimberlite magma is a rare and fascinating type of magma that originates deep within the Earth's mantle. Here's a breakdown of its key characteristics:
Origin and Formation:
* Deep Mantle Origin: Kimberlite magma originates from the Earth's mantle, typically at depths of 150-450 kilometers (93-280 miles). This is much deeper than most other magmas, which form in the upper mantle or crust.
* Ultramafic Composition: It is ultramafic, meaning it's very rich in magnesium and iron, and relatively poor in silica.
* Explosive Ascent: Kimberlite magma ascends rapidly, often explosively, through the crust. This is due to its high gas content (mainly CO2 and H2O) and its relatively low density compared to surrounding rocks.
Characteristics:
* High Pressure and Temperature: Kimberlite magma is formed under extremely high pressure and temperature conditions, which allows it to incorporate and carry deep mantle minerals, including diamonds.
* High Viscosity: Although it ascends rapidly, kimberlite magma is relatively viscous, meaning it flows slowly. This viscosity is due to its ultramafic composition and high gas content.
* Unique Mineralogy: Kimberlite magma is characterized by the presence of specific minerals like olivine, pyrope garnet, phlogopite mica, and, of course, diamonds. These minerals are indicative of its deep mantle origin.
Geological Significance:
* Diamond Source: Kimberlite magma is the primary source of diamonds found on Earth. The extreme pressure and temperatures during its ascent allow diamonds to crystallize and get transported to the surface.
* Window into the Mantle: Studying kimberlites provides valuable insights into the composition and processes occurring in the deep Earth's mantle.
* Economic Importance: Kimberlite pipes are often mined for diamonds, making them economically significant.
Formation and Occurrence:
* Mantle Plumes: Kimberlite magma is believed to be associated with mantle plumes, which are upwellings of hot, dense material from the Earth's deep mantle.
* Kimberlite Pipes: When kimberlite magma erupts at the surface, it creates characteristic pipe-shaped volcanic structures known as kimberlite pipes. These pipes are often filled with kimberlite breccia, a mixture of fragmented rocks and minerals.
* Global Distribution: Kimberlite pipes are found globally, with major deposits in South Africa, Canada, Australia, and Russia.
In Summary:
Kimberlite magma is a remarkable and valuable geological phenomenon. Its deep origin, explosive ascent, and unique mineralogy make it a fascinating subject of study and a critical source of diamonds for humankind.
