Hello, readers. Here's a brief account on Kimberlite.
Kimberlite is a rare, ultramafic volcanic rock that is known for its association with diamond deposits.
Composition:
It is typically composed of olivine, phlogopite, serpentine, and other minerals, and is often rich in mantle-derived xenoliths.
Properties:
Kimberlite eruptions are extremely explosive and can produce steep-sided, cone-shaped volcanic landforms known as kimberlite pipes. These pipes can reach depths of several hundred meters and can be several hectares in size.
Kimberlite pipes are the primary source of commercial diamond deposits, as diamonds are often found within the rock itself or in the surrounding alluvial deposits. The presence of diamonds in kimberlite pipes is believed to be the result of the rapid ascent and cooling of magma, which traps and preserves the diamonds before they can be destroyed.
Kimberlite is a type of ultramafic volcanic rock that is typically associated with diamond deposits. There are several types of kimberlite, which are classified based on their mineralogy and geochemistry. Here are some of the main types:
Group I kimberlite: This is the most common type of kimberlite and is characterized by a high magnesium content and a low aluminum content. Group I kimberlites are typically rich in olivine, phlogopite, and serpentine, and often contain mantle-derived xenoliths.
Group II kimberlite: This type of kimberlite has a lower magnesium content and a higher aluminum content than Group I kimberlite. Group II kimberlites are typically rich in ilmenite and garnet, and often contain eclogitic xenoliths.
Group III kimberlite: This is the rarest type of kimberlite and is characterized by a low magnesium content and a high potassium content. Group III kimberlites are typically rich in phlogopite and contain xenoliths of both lithospheric and asthenospheric origin.
The classification of kimberlite types is based on the ratio of certain trace elements, such as titanium, niobium, and strontium. This information is used to infer the origin of the kimberlite magma and its relationship to diamond formation.
Kimberlite and its association with Diamonds:
Kimberlites are igneous rocks that are typically associated with the formation of diamonds. Here are some of the key geological characteristics of kimberlites:
Kimberlites are volcanic rocks that are formed deep within the Earth's mantle, typically at depths of 150-450 kilometers.
Kimberlites are classified as ultramafic rocks, which means they have a very low silica content and are rich in magnesium and iron.
Kimberlites have a characteristic porphyritic texture, which means they have large, visible crystals (phenocrysts) set in a finer-grained matrix. The phenocrysts are typically olivine, pyroxene, and sometimes garnet.
Kimberlites often contain xenoliths, which are pieces of rock that are incorporated into the kimberlite as it rises to the surface. These xenoliths can provide important information about the composition and structure of the Earth's mantle.
Kimberlites are typically found in small, pipe-like structures that rise from the mantle to the Earth's surface. These structures are often steep-sided and can be several hundred meters in diameter.
Kimberlites often contain diamonds and other valuable minerals, such as garnet, spinel, and chromite. The diamonds in kimberlites are typically small and of low quality, but some kimberlite deposits can be highly productive.
Origin:
The tectonic setting of kimberlite formation is still debated, but it is generally believed to be related to deep mantle processes and the upwelling of mantle material towards the Earth's surface. Some of the proposed tectonic settings for kimberlite formation include:
Subduction zones: Some studies have suggested that kimberlite magmas may be generated in subduction zones, where the descending slab of oceanic lithosphere interacts with the mantle and triggers melting. However, this idea is controversial and there is limited evidence to support it.
Mantle plumes: It is more widely accepted that kimberlite magmas are generated in association with mantle plumes, which are upwellings of hot material from the Earth's mantle. The intense heat and pressure associated with mantle plumes can cause partial melting of the mantle, generating kimberlite magmas.
Lithospheric extension: Another proposed mechanism for kimberlite formation is lithospheric extension, which can create zones of partial melting in the upper mantle. This process may be triggered by tectonic events such as continental rifting or mantle upwelling.
Here is a brief overview of some of the major kimberlite intrusions across the globe in a chronological order:
The oldest known kimberlite intrusion is the 2.7 billion-year-old Kapvaal Craton in South Africa, which contains the famous diamond mines of Kimberley.
In the early Paleozoic era, around 500 million years ago, several kimberlite intrusions were emplaced in what is now the Canadian Shield. Some of the most famous Canadian kimberlite pipes include the Ekati, Diavik, and Snap Lake mines in the Northwest Territories.
During the Late Cretaceous period, around 100 million years ago, there was a major pulse of kimberlite activity around the world. This included the emplacement of several large kimberlite fields in Siberia, such as the Udachnaya and Mir mines.
In the late Eocene and early Oligocene, around 40-30 million years ago, several kimberlite pipes were emplaced in the Colorado-Wyoming State Line district in the United States. This area is now known as the Colorado-Wyoming kimberlite province.
In the Neogene period, around 25-5 million years ago, several kimberlite intrusions were emplaced in southern Africa, including the Premier mine in South Africa and the Mwadui mine in Tanzania.
In the Quaternary period, there have been several more recent kimberlite eruptions, including the Argyle mine in Australia, which started production in the early 1980s, and the Renard mine in Quebec, Canada, which started production in 2017.
Indian Picture of Kimberlite:
There is only one known kimberlite intrusion in India, which is located in the state of Madhya Pradesh. Here is some information on this intrusion:
The Majhgawan-Kankarwara kimberlite field is located in the Chhatarpur district of Madhya Pradesh, in central India.
The kimberlite pipes were discovered in 1967 and were later found to contain diamonds.
The pipes are believed to have been emplaced during the Late Cretaceous period, around 100 million years ago.
The Majhgawan pipe is the largest of the pipes, with a surface area of around 8 hectares.
The diamonds from the Majhgawan-Kankarwara kimberlite field are of low quality and are mostly used for industrial purposes.
It's worth noting that the Majhgawan-Kankarwara kimberlite field is a relatively small and poorly-known kimberlite intrusion compared to many of the major kimberlite fields around the world.
Some of the major diamond-producing regions in India:
Panna in Madhya Pradesh: Panna is one of the most famous diamond-producing regions in India, known for its high-quality diamonds. The most famous mine in the region is the Majhgawan mine.
Wajrakarur in Andhra Pradesh: Wajrakarur is another important diamond-producing region in India, known for its alluvial diamond deposits.
Bunder in Madhya Pradesh: Bunder is a relatively new diamond mine in India, with estimated reserves of around 34 million carats of diamonds.
Krishna River Valley in Andhra Pradesh: The Krishna River Valley is known for its alluvial diamond deposits, which are mined using traditional techniques.
Mahodari in Maharashtra: The Mahodari mine is a small diamond mine in Maharashtra, known for its high-quality diamonds.
Trivia:
Kimberlite is named after the town of Kimberley in South Africa, where the first kimberlite pipes were discovered in the late 19th century. Today, kimberlite deposits are found in a number of countries around the world, including Russia, Canada, Angola, and Australia.
Hope you liked it. Stay tuned for more.
Geo Khan.
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