“Natural diamonds crystallize from carbon at depths of about 150 to 200 kilometers in Earth's mantle under temperatures of about 900 to 1,300 degrees Celsius and pressures of 45 to 60 kilobars, then reach Earth's surface through deep volcanic eruptions after remaining underground for hundreds of millions of years.”

According to classical models, in the lithospheric mantle, diamond formation occurs at depths of 120–210 km and temperatures of 900–1500 °C as a result of metasomatic processes.

Inclusion based geothermobarometry indicates that peridotitic suite diamonds typically (1 sigma range about the average) originate from a 140–190km depth at temperatures between 1040–1250°C.

According to classical models, in the lithospheric mantle, diamond formation occurs at depths of 120–210 km and temperatures of 900–1500 ◦C as a result of metasomatic processes.

These enigmatic magmas, originating from depths exceeding 150 km in Earth's mantle 1 , occur in stable cratons and in pulses broadly synchronous with supercontinent cyclicity 4 . … Hence, although cratonic roots are anomalously thick, cool and stable over billions of years 7, 9, 30 , only small changes in pressure and temperature are required to generate the small-volume, low-degree partial melts thought to be characteristic of kimberlites 2, [42] [43] [44] .

The early work on inclusions in diamonds led to two fundamental discoveries: (i) diamonds form long before emplacement of their kimberlite or lamproite hosts and hence are mantle xenocrysts; (ii) minerals included in diamonds can be related to rock types characteristic of the mantle roots underlying ancient cratons. … As a consequence of lower temperatures the graphite-diamond transition is raised to shallower depth (130 to 150km, Fig. 1) within subcratonic lithosphere, creating a diamond stable window where cratonic roots extend into the diamond stability field.

The principal sources of natural diamonds are peridotitic (about 2/3 of diamonds) and eclogitic (1/3) domains located at 140–200 km depth in the subcratonic lithospheric mantle.

Natural diamonds typically form 150–200 km below the surface of the earth. … Diamonds that form within these continental roots are known as lithospheric diamonds and are carried up to the surface of the earth by rare volcanic eruptions known as kimberlites. … If so, fibrous diamonds could form right before the kimberlite eruption to the earth’s surface, which would make them much younger than many gem-quality diamonds that may have resided in the mantle for millions to billions of years.

Kimberlite magmas are volatile-rich, silica-poor ultrabasic magmas originating as small-degree mantle melts at depths of 150 km or greater.

The oxidation state of the mantle at depths where diamonds form (i.e. >~150 km) generally lies below the minimum oxygen fugacity (ƒO2) for carbonate stability 15 as defined by equilibria such as enstatite + magnesite = forsterite + C (diamond) + O2 (EMOD) 16.

Natural Diamond Formation. Natural diamonds typically form 150–200 km below the surface of the earth. … Diamonds that form within these continental roots are known as lithospheric diamonds and are carried up to the surface of the earth by rare volcanic eruptions known as kimberlites.

Kimberlite melts are primary carriers of mantle-derived carbon and hydrogen, playing an important role in Earth’s deep carbon cycle and diamond transport. … Ascending from the upper mantle, kimberlite melts incorporate xenoliths and xenocrysts and exsolve volatiles.

the frequency distribution of pressures for lithospheric diamond is essentially unimodal, with a mode at ~6 GPa, corresponding to depths around ~190 km

There is compelling evidence that kimberlite magmas are extracted from their source region and erupted without significant residence times in the crust (e.g., Mitchell, 2008). … Diamonds are rapidly transported to the surface by kimberlite (or lamproite or ultrabasic lamprophyre) magmas that are channelled by deep, stable magma pathways.

The peak metamorphic conditions of the Kokchetav UHPM rocks are estimated by thermobarometry of the rock forming minerals to be P = ~4.5 GPa and T = 950–1000 °C(e.g., Ogasawara 2005). Studies of nanoinclusions in these diamonds suggest that the Kokchetav diamonds formed at a pressure range of 6–9 GPa, and a temperature range of 980–1200 °C (e.g., Dobrzhinetskaya et al. 2006a).

The majority of diamonds mined as gemstones were formed in the base of ancient thick regions of continents, at a depth of about 150–200 km.

From there, diamonds are carried to Earth's surface by eruptions of kimberlite magma.

The nodule is believed to have come from a section of depleted (partially melted) Iherzolite at a depth of 130 to 180 kilometers.

The pressure (P) and temperature (T) of diamond formation are an essential part of this knowledge and their assessment is pivotal to develop predictive scenarios of diamond distribution in the Earth interior.

Lithospheric diamonds are different from sublithospheric diamonds in critical ways: higher average N content, ages extending into the Paleoarchean, inclusion assemblages indicating formation at lower pressure, and lack of ubiquitous deformation features.

This is much deeper than most other gem diamonds, which form in the lower part of continental tectonic plates at depths of 150-200 km (approximately 93-124 miles).

Kimberlite rocks and deposits are the eruption products of volatile-rich, silica-poor ultrabasic magmas that originate as small-degree mantle melts at depths in excess of 200 km.

Kimberlites -- carrot-shaped volcanic pipes that erupt from mantle depths greater than 150 km -- have long fascinated geologists as windows into the deep Earth. … Diamonds make it to the surface in kimberlites because their rapid ascent prevents them from reverting to graphite, which is more stable at shallow pressures and temperatures.

Application of these methods has yielded the whole range of depths from 110–150 km, corresponding to the graphite–diamond boundary in the lithosphere, to over 660 km, within the lower mantle 1-5.

Diamond formation requires exposure of carbon-bearing materials to high pressure, ranging approximately between 45 and 60 kilobars, but at a comparatively low temperature range between approximately 1652–2372 °F (900–1300 °C). … These depths are estimated to be in between 140–190 kilometers (90–120 miles) though occasionally diamonds have crystallized at depths of 300-400 km (180-250 miles) as well. … Diamond-bearing rock is brought close to the surface through deep-origin volcanic eruptions.

Diamonds were formed over 3 billion years ago deep within the Earth’s crust under conditions of intense heat and pressure that cause carbon atoms to crystallise forming diamonds. … Diamonds are found at a depth of approx. 150-200km below the surface of the Earth. Here, temperatures average 900 to 1,300 degrees Celsius and at a pressure of 45 to 60 kilobars (which is around 50,000 times that of atmospheric pressure at the Earth’s surface). … This expansion causes the magma to erupt, forcing it to the Earth’s surface and taking along with it diamond bearing rocks.

The formation of diamonds predominantly occurs at depths ranging from 90 to 120 miles (150 to 200 kilometers) beneath the Earth's surface. … Pressure: Between 50,000 to 70,000 atmospheres (5 to 7 gigapascals or GPa), which is approximately 45,000 to 60,000 times the atmospheric pressure at sea level. - Temperature: Ranging from 900°C to 1,300°C (1,652°F to 2,372°F). … Diamonds form deep in the mantle and reach the Earth’s surface through rare, powerful volcanic eruptions.

kimberlite eruption, small but powerful volcanic eruption caused by the rapid ascent of kimberlites—a type of intrusive igneous rock originating in the asthenosphere—through the lithosphere and onto the surface of the Earth.