Editing Kimberlite

{{short description|Igneous rock which sometimes contains diamonds}}
{{Infobox rock
|name = Kimberlite
|type = Igneous
|image = Kimberlite (Hamilton Branch Kimberlite, Elliott County Peridotite, Late Cretaceous, ~75 Ma; between Ison Creek & Hamilton Branch, Elliott County, Kentucky, USA).jpg
|caption = Kimberlite from the United States
|composition =  Forsteritic olivine and carbonate minerals, with trace amounts of magnesian ilmenite, chromium pyrope, almandine-pyrope, chromium diopside, phlogopite, enstatite and titanium-poor chromite. Sometimes contains [[diamond]]s.
}}
[[Image:Kimberlite crosssection QEMSCAN.png|thumb|False-color [[scanning electron microscope]] image of kimberlite from South Africa. [[Olivine]] crystals (green) are in a fine-grained [[Matrix (geology)|matrix]] made up of clay minerals and carbonates (presented in blue, purple and [[Buff (color)|buff]] colors).]]

'''Kimberlite''' is an [[igneous rock]] and a rare variant of [[peridotite]]. It is most commonly known as the main host matrix for [[diamond]]s. It is named after the town of [[Kimberley, Northern Cape|Kimberley]] in [[South Africa]], where the discovery of an 83.5-[[Carat (mass)|carat]] (16.70 g) diamond called the [[Star of South Africa (diamond)|Star of South Africa]] in 1869 spawned a [[diamond rush]] and led to the excavation of the [[open-pit]] mine called the [[Big Hole]]. Previously, the term kimberlite has been applied to olivine lamproites as Kimberlite II, however this has been in error.

Kimberlite occurs in the Earth's [[Crust (geology)|crust]] in vertical structures known as [[Volcanic pipe|kimberlite pipes]], as well as igneous [[Dike (geology)|dykes]] and can also occur as horizontal [[Sill (geology)|sills]]. Kimberlite pipes are the most important source of mined diamonds today. The consensus on kimberlites is that they are formed deep within [[Earth's mantle]]. Formation occurs at depths between 150 and 450 kilometres (93 and 280&nbsp;mi), potentially from anomalously enriched exotic mantle compositions, and they are erupted rapidly and violently, often with considerable [[carbon dioxide]] and other [[Volatile (astrogeology)|volatile]] components. It is this depth of melting and generation that makes kimberlites prone to hosting diamond [[xenocryst]]s.

Despite its relative rarity, kimberlite has attracted attention because it serves as a carrier of diamonds and [[garnet]] peridotite mantle [[xenolith]]s to the Earth's surface. Its probable derivation from depths greater than any other [[igneous rock]] type, and the extreme [[magma]] composition that it reflects in terms of low [[silica]] content and high levels of [[incompatible element|incompatible]] [[trace-element]] enrichment, make an understanding of kimberlite [[petrogenesis]] important. In this regard, the study of kimberlite has the potential to provide information about the composition of the deep mantle and melting processes occurring at or near the interface between the [[craton]]ic continental [[lithosphere]] and the underlying convecting [[asthenosphere|asthenospheric]] mantle.

== Morphology and volcanology ==

[[File:Kimberlite Pipes in Africa.png|thumb|Distribution of kimberlites in Africa. Cratons: CA-Central African (Kasai), SA-South African (Kalahari), WA-West African; Kimberlites (shown as red dots): B-Banankoro, Cu-Cuango Valley, Do-Dokolwayo, F-Finsch, G-Gope, J-Kwaneng, Ja-Jagersfontein, k-Koidu, Kb-Kimberley, Ko-Koffiefontein, L-Letlhakane, Le-Letseng, Lu-Lunda, M-Mitzic, Mb-Mbuji-Mayi, Mw-Mwadui, O-Orapa, P-[[Premier Mine|Premier]], R-River Ranch, V-Venetia.]]
Many kimberlite structures are emplaced as carrot-shaped, vertical intrusions termed "[[Volcanic pipe|pipes]]". This classic carrot shape is formed due to a complex intrusive process of kimberlitic magma, which inherits a large proportion of CO<sub>2</sub> (lower amounts of H<sub>2</sub>O) in the system, which produces a deep explosive boiling stage that causes a significant amount of vertical flaring.<ref>{{cite journal|last1=Bergman|first1=Steven C.|title=Lamproites and other potassium-rich igneous rocks: a review of their occurrence, mineralogy and geochemistry|journal=Geological Society, London, Special Publications|date=1987|volume=30|issue=1|pages=103–190|doi=10.1144/GSL.SP.1987.030.01.08|bibcode=1987GSLSP..30..103B|s2cid=129449668}}</ref> Kimberlite classification is based on the recognition of differing rock [[facies]]. These differing facies are associated with a particular style of magmatic activity, namely crater, diatreme and [[hypabyssal]] rocks.<ref>Clement, C. R., 1982: A comparative geological study of some major kimberlite pipes in the Northern Cape and Orange free state. PhD Thesis, University of Cape Town.</ref><ref>Clement, C. R., and Skinner, E. M. W. 1985: A textural-genetic classification of kimberlites. Transactions of the Geological Society of South Africa. pp.&nbsp;403–409.</ref>

The [[geomorphology|morphology]] of kimberlite pipes and their classical carrot shape is the result of explosive [[Volcanic pipe|diatreme]] [[volcanism]] from very deep [[Earth's mantle|mantle]]-derived sources. These volcanic explosions produce vertical columns of rock that rise from deep magma reservoirs. The eruptions forming these [[volcanic pipe|pipes]] fracture the surrounding rock as it explodes, bringing up unaltered [[xenolith]]s of peridotite to surface. These [[xenolith]]s provide valuable information to geologists about mantle conditions and composition.<ref>{{Cite journal |last=Sparks |first=R.S.J. |date=2013-05-30 |title=Kimberlite Volcanism |url=https://www.annualreviews.org/doi/10.1146/annurev-earth-042711-105252 |journal=Annual Review of Earth and Planetary Sciences |language=en |volume=41 |issue=1 |pages=497–528 |doi=10.1146/annurev-earth-042711-105252 |bibcode=2013AREPS..41..497S |issn=0084-6597|url-access=subscription }}</ref><ref>{{Cite web |title=kimberlite eruption {{!}} volcanism {{!}} Britannica |url=https://www.britannica.com/science/kimberlite-eruption |access-date=2022-07-14 |website=www.britannica.com |language=en}}</ref> The morphology of kimberlite pipes is varied, but includes a sheeted dyke complex of tabular, vertically dipping feeder dykes in the root of the pipe, which extends down to the mantle. Within {{convert|1.5|-|2|km|ft|abbr=on}} of the surface, the highly pressured magma explodes upwards and expands to form a conical to cylindrical [[diatreme]], which erupts to the surface. The surface expression is rarely preserved but is usually similar to a [[maar|maar volcano]]. Kimberlite dikes and sills can be thin (1&ndash;4 meters), while pipes range in diameter from about 75 meters to 1.5 kilometers.<ref>{{cite book|last1=Kjarsgaard|first1=B. A.|chapter=Kimberlite pipe models: significance for exploration|editor-last1=Milkereit|editor-first1=B.|title=Proceedings of Exploration 07: Fifth Decennial International Conference on Mineral Exploratio|date=2007|publisher=[[Decennial Mineral Exploration Conferences]], 2007|pages=667&ndash;677|chapter-url=http://www.dmec.ca/ex07-dvd/E07/pdfs/46.pdf|access-date=1 March 2018|archive-date=3 August 2021|archive-url=https://web.archive.org/web/20210803232440/http://www.dmec.ca/ex07-dvd/E07/pdfs/46.pdf|url-status=dead}}</ref>

== Petrology ==

Both the location and origin of kimberlitic magmas are subjects of contention. Their extreme enrichment and geochemistry have led to a large amount of speculation about their origin, with models placing their source within the sub-continental lithospheric mantle (SCLM) or even as deep as the transition zone. The mechanism of enrichment has also been the topic of interest with models including partial melting, assimilation of subducted sediment or derivation from a primary magma source.

Historically, kimberlites have been classified into two distinct varieties, termed "basaltic" and "micaceous" based primarily on petrographic observations.<ref>Wagner, P. A., 1914: The diamond fields of South Africa; Transvaal Leader, Johannesburg.</ref> This was later revised by C. B. Smith, who renamed these divisions "group I" and "group II" based on the isotopic affinities of these rocks using the [[neodymium|Nd]], [[strontium|Sr]], and Pb systems.<ref>Smith, C. B., 1983: Lead, strontium, and neodymium isotopic evidence for sources of African Cretaceous kimberlite, Nature, 304, pp. 51–54.</ref>  Roger Mitchell later proposed that these group I and II kimberlites display such distinct differences, that they may not be as closely related as once thought. He showed that group II kimberlites show closer affinities to [[lamproite]]s than they do to group I kimberlites. Hence, he reclassified group II kimberlites as orangeites to prevent confusion.<ref>{{cite book|last1=Mitchell|first1=Roger Howard|title=Kimberlites, Orangeites, and Related Rocks|date=1995|publisher=Springer US|location=Boston, MA|isbn=978-1461519935}}</ref>

=== Group I kimberlites ===

Group-I kimberlites are of CO<sub>2</sub>-rich [[ultramafic]] potassic igneous rocks dominated by primary [[Forsterite|forsteritic olivine]] and carbonate minerals, with a trace-mineral assemblage of magnesian [[ilmenite]], chromium [[pyrope]], [[almandine]]-pyrope, chromium [[diopside]] (in some cases subcalcic), [[phlogopite]], [[enstatite]] and of Ti-poor [[chromite]]. Group I kimberlites exhibit a distinctive inequigranular texture caused by macrocrystic ({{convert|0.5|-|10|mm|in|disp=or|abbr=on}}) to megacrystic ({{convert|10|-|200|mm|in|disp=or|abbr=on}}) phenocrysts of olivine, pyrope, chromian diopside, magnesian ilmenite, and phlogopite, in a fine- to medium-grained groundmass.<ref>{{Cite journal |last1=Sarkar |first1=Soumendu |last2=Giuliani |first2=Andrea |last3=Dalton |first3=Hayden |last4=Phillips |first4=David |last5=Ghosh |first5=Sujoy |last6=Misev |first6=Sarah |last7=Maas |first7=Roland |date=2023-06-20 |title=Derivation of Lamproites and Kimberlites from a Common Evolving Source in the Convective Mantle: the Case for Southern African 'Transitional Kimberlites' |url=http://dx.doi.org/10.1093/petrology/egad043 |journal=Journal of Petrology |volume=64 |issue=7 |doi=10.1093/petrology/egad043 |issn=0022-3530|hdl=20.500.11850/623387 |hdl-access=free }}</ref>

The groundmass mineralogy, which more closely resembles a true composition of the igneous rock, is dominated by carbonate and significant amounts of forsteritic olivine, with lesser amounts of pyrope garnet, Cr-[[diopside]], magnesian ilmenite, and [[spinel]].

=== Olivine lamproites ===

Olivine lamproites were previously called group II kimberlite or orangeite in response to the mistaken belief that they only occurred in South Africa. Their occurrence and petrology, however, are identical globally and should not be erroneously referred to as kimberlite.<ref>{{cite journal |last1=Francis |first1=Don |last2=Patterson|first2=Michael|title=Kimberlites and aillikites as probes of the continental lithospheric mantle|journal=Lithos|date=April 2009|volume=109|issue=1–2|pages=72–80 |doi= 10.1016/j.lithos.2008.05.007|bibcode=2009Litho.109...72F }}</ref> Olivine lamproites are [[ultrapotassic igneous rocks|ultrapotassic]], [[peralkaline rock]]s rich in volatiles (dominantly H<sub>2</sub>O). The distinctive characteristic of olivine lamproites is [[phlogopite]] macrocrysts and microphenocrysts, together with groundmass micas that vary in composition from phlogopite to "tetraferriphlogopite" (anomalously Al-poor phlogopite requiring Fe to enter the tetrahedral site). Resorbed olivine macrocrysts and euhedral primary crystals of groundmass olivine are common but not essential constituents.

Characteristic primary phases in the groundmass include zoned pyroxenes (cores of diopside rimmed by Ti-aegirine), spinel-group minerals (magnesian [[chromite]] to titaniferous [[magnetite]]), Sr- and [[Rare-earth element|REE]]-rich [[perovskite]], Sr-rich [[apatite]], REE-rich phosphates ([[monazite]], daqingshanite), potassian barian [[hollandite]] group minerals, Nb-bearing [[rutile]] and Mn-bearing [[ilmenite]].

=== Kimberlitic indicator minerals ===

Kimberlites are peculiar igneous rocks because they contain a variety of mineral species with chemical compositions that indicate they formed under high pressure and temperature within the mantle. These minerals, such as chromium diopside (a [[pyroxene]]), chromium spinels, magnesian ilmenite, and pyrope garnets rich in chromium, are generally absent from most other igneous rocks, making them particularly useful as indicators for kimberlites.

== Geochemistry ==

{{More citations needed section|date=October 2007}}
Kimberlites exhibit unique geochemical characteristics that distinguish them from other igneous rocks, reflecting their origin deep within the Earth's mantle. These features provide insights into the mantle's composition and the processes involved in the formation and eruption of kimberlite magmas.

=== Composition ===
Kimberlites are classified as ultramafic rocks due to their high [[magnesium oxide]] (MgO) content, which typically exceeds 12%, and often surpasses 15%. This high MgO concentration indicates a mantle-derived origin, rich in [[olivine]] and other magnesium-dominant minerals. Additionally, kimberlites are ultrapotassic, with a molar ratio of [[potassium oxide]] (K<sub>2</sub>O) to [[Aluminium oxide|aluminum oxide]] (Al<sub>2</sub>O<sub>3</sub>) greater than 3, suggesting significant alterations or enrichment processes in their mantle source regions.

=== Elemental abundance ===
Characteristic of kimberlites is their abundance in near-primitive elements such as [[nickel]] (Ni), chromium (Cr), and cobalt (Co), with concentrations often exceeding 400 [[Parts per million|ppm]] for Ni, 1000 ppm for Cr, and 150 ppm for Co. These high levels reflect the primitive nature of their mantle source, having undergone minimal differentiation.

=== Rare Earth and lithophile elements ===
Kimberlites show enrichment in [[Rare-earth element|rare earth elements]] (REEs),<ref>{{Cite journal |last=Nixon |first=P.H. |date=March 1995 |title=The morphology and nature of primary diamondiferous occurrences |url=https://doi.org/10.1016/0375-6742(94)00034-9 |journal=Journal of Geochemical Exploration |volume=53 |issue=1–3 |pages=41–71 |doi=10.1016/0375-6742(94)00034-9 |bibcode=1995JCExp..53...41N |issn=0375-6742|url-access=subscription }}</ref> which are pivotal for understanding their genesis and evolution. This enrichment in REEs, along with a moderate to high large-[[ion]] [[lithophile element]] (LILE)<ref>{{Cite journal |last=CAMERON |first=E. M. |date=September 1994 |title=Depletion of gold and LILE in the lower crust: Lewisian Complex, Scotland |url=http://dx.doi.org/10.1144/gsjgs.151.5.0747 |journal=Journal of the Geological Society |volume=151 |issue=5 |pages=747–754 |doi=10.1144/gsjgs.151.5.0747 |bibcode=1994JGSoc.151..747C |issn=0016-7649|url-access=subscription }}</ref> enrichment (more than 1,000 ppm) including [[potassium]], barium, and strontium, points to a significant contribution from [[metasomatism|metasomatized]] mantle sources, where the rock composition has been altered by fluids.

=== Volatile content ===
A defining feature of kimberlites is their high volatile content, particularly of water (H<sub>2</sub>O) and carbon dioxide (CO<sub>2</sub>). The presence of these volatiles influences the explosivity of kimberlite eruptions and facilitates the transport of diamonds from deep within the mantle to the Earth's surface. The high levels of H<sub>2</sub>O and CO<sub>2</sub> are indicative of a deep mantle origin, where these compounds are more abundant.<ref>{{Cite journal |last1=Stachel |first1=T. |last2=Harris |first2=J.W. |date=September 2008 |title=The origin of cratonic diamonds — Constraints from mineral inclusions |url=https://doi.org/10.1016/j.oregeorev.2007.05.002 |journal=Ore Geology Reviews |volume=34 |issue=1–2 |pages=5–32 |doi=10.1016/j.oregeorev.2007.05.002 |bibcode=2008OGRv...34....5S |issn=0169-1368|url-access=subscription }}</ref>

== Exploration techniques ==
Kimberlite exploration techniques encompass a multifaceted approach that integrates geological, geochemical, and geophysical methodologies to locate and evaluate potential diamond-bearing deposits.<ref name=":0">{{Cite journal |last1=Kjarsgaard |first1=Bruce A. |last2=Januszczak |first2=Nicole |last3=Stiefenhofer |first3=Johann |date=2019-12-01 |title=Diamond Exploration and Resource Evaluation of Kimberlites |url=https://doi.org/10.2138/gselements.15.6.411 |journal=Elements |volume=15 |issue=6 |pages=411–416 |doi=10.2138/gselements.15.6.411 |bibcode=2019Eleme..15..411K |issn=1811-5217|url-access=subscription }}</ref>

=== Indicator minerals sampling ===
Exploration techniques for kimberlites primarily hinge on the identification and analysis of indicator minerals associated with the presence of kimberlite pipes and their potential diamond content. Sediment sampling is a fundamental approach, where kimberlite indicator minerals (KIMs) are dispersed across landscapes due to geological processes like uplift, erosion, and glaciations. Loaming and alluvial sampling are utilized in different terrains to recover KIMs from soils and stream deposits, respectively. Understanding paleodrainage patterns and geological cover layers aids in tracing KIMs back to their source kimberlite pipes. In glaciated regions, techniques such as [[esker]] sampling, [[till]] sampling, and alluvial sampling are employed to recover KIMs buried beneath thick glacial deposits. Once collected, heavy minerals are separated and sorted by hand to identify these indicators. Chemical analysis confirms their identity and categorizes them. Techniques like [[Geothermobarometry|thermobarometry]] help understand the conditions under which these minerals formed and where they came from in the Earth's mantle. By analyzing these indicators and geological curves, scientists can estimate the likelihood of finding diamonds in a kimberlite pipe. These methods help prioritize where to drill in the search for valuable diamond deposits.<ref>H.O. Cookenboo, H.S. Grütter; Mantle-derived indicator mineral compositions as applied to diamond exploration. ''Geochemistry: Exploration, Environment, Analysis'' 2010;; 10 (1): 81–95.</ref><ref>McClenaghan, B., Peuraniemi, V. and Lehtonen, M. 2011. Indicator mineral methods in mineral exploration. Workshop in the 25th International Applied Geochemistry Symposium 2011, 22–26 August 2011 Rovaniemi, Finland. Vuorimiesyhdistys, B92-4, 72 pages.</ref>

=== Geophysical methods ===
Geophysical methods are particularly useful in areas where direct detection of kimberlites is challenging due to significant [[overburden]] or weathering. These methods leverage physical property contrasts between kimberlite bodies and their surrounding host rocks, enabling the detection of subtle anomalies indicative of potential kimberlite deposits. Airborne and ground surveys, including magnetics, electromagnetics, and gravity surveys, are commonly employed to acquire geophysical data over large areas efficiently. Magnetic surveys detect variations in the Earth's magnetic field caused by magnetic minerals within kimberlites, which typically exhibit distinct magnetic signatures compared to surrounding rocks. Electromagnetic surveys measure variations in electrical conductivity, with conductive kimberlite bodies producing anomalous responses. Gravity surveys detect variations in gravitational attraction caused by differences in density between kimberlite and surrounding rocks. By analyzing and interpreting these geophysical anomalies, geologists can delineate potential kimberlite targets for further investigation, such as drilling. However, the interpretation of geophysical data requires careful consideration of geological context and potential masking effects from surrounding geology, highlighting the importance of integrating geophysical results with other exploration techniques for accurate targeting and successful diamond discoveries.<ref name=":0" /><ref>{{Cite book |last1=Soloveichik |first1=Yury G. |last2=Persova |first2=Marina G. |last3=Sivenkova |first3=Anastasia P. |last4=Kiselev |first4=Dmitry S. |last5=Simon |first5=Evgenia I. |last6=Leonovich |first6=Daryana A. |chapter=Comparative Analysis of Airborne Electrical Prospecting Technologies Using Helicopter Platforms and UAVs when Searching for Kimberlite Pipes |date=2023-11-10 |title=2023 IEEE XVI International Scientific and Technical Conference Actual Problems of Electronic Instrument Engineering (APEIE) |chapter-url=https://ieeexplore.ieee.org/document/10347567 |publisher=IEEE |pages=1–4 |doi=10.1109/APEIE59731.2023.10347567 |isbn=979-8-3503-3088-5}}</ref>

=== 3-D modeling ===
<!-- Deleted image removed: [[File:BK16-Fig3.jpg|thumb|Kimberlite pipe 3D model]] -->
Three-dimensional (3D) modeling offers a comprehensive framework for understanding the internal structure and distribution of key geological features within potential diamond-bearing deposits. This process begins with the collection and integration of various datasets, including drill-hole data, ground geophysical surveys, and geological mapping information. These datasets are then integrated into a cohesive digital platform, often utilizing specialized software packages tailored for geological modeling. Through advanced visualization techniques, geologists can create detailed 3D representations of the subsurface geology, highlighting the distribution and geometry of kimberlite bodies alongside other significant geological features such as faults, fractures, and lithological boundaries. Within the model, efforts are made to accurately depict the internal phases of kimberlite pipes, incorporating different [[facies]], country rock xenoliths, and mantle xenoliths identified through careful interpretation of drill-core data and geophysical surveys. Once validated, the 3D model serves as a valuable decision-making tool, offering insights into potential diamond-bearing potential, identifying high-priority drilling targets, and guiding exploration strategies to maximize the chances of successful diamond discoveries.<ref>{{Cite journal |last1=Lépine |first1=Isabelle |last2=Farrow |first2=Darrell |date=2018-12-01 |title=3D geological modelling of the Renard 2 kimberlite pipe, Québec, Canada: from exploration to extraction |url=https://doi.org/10.1007/s00710-018-0567-x |journal=Mineralogy and Petrology |language=en |volume=112 |issue=2 |pages=411–419 |doi=10.1007/s00710-018-0567-x |bibcode=2018MinPe.112..411L |issn=1438-1168|url-access=subscription }}</ref><ref>{{Cite conference |last1=Hetman |first1=C. M. |last2=Diering |first2=M. D. |last3=Barnett |first3=W. |chapter=Generation of 3D kimberlite pipe models for resource classification and mine planning: Data sources, procedures, and guidelines |date=2017-09-18 |title=International Kimberlite Conference Extended Abstracts: 2017 |chapter-url=https://ikcabstracts.com/index.php/ikc/article/view/4005 |language=en |volume=11 |doi=10.29173/ikc4005|isbn=978-1-55195-425-7 }}</ref>

== Historical significance ==
Kimberlites are a valuable source of information about the composition of the Earth's mantle and the dynamic processes that occur within it. The study of kimberlites has contributed to our understanding of the Earth’s deep geochemical cycles and the mechanism of [[mantle plume]]s, which are upwellings of abnormally hot rock within the Earth's mantle.<ref>{{Cite journal |last1=Torsvik |first1=Trond H. |last2=Burke |first2=Kevin |last3=Steinberger |first3=Bernhard |last4=Webb |first4=Susan J. |last5=Ashwal |first5=Lewis D. |date=July 2010 |title=Diamonds sampled by plumes from the core–mantle boundary |url=https://www.nature.com/articles/nature09216 |journal=Nature |language=en |volume=466 |issue=7304 |pages=352–355 |doi=10.1038/nature09216 |pmid=20631796 |bibcode=2010Natur.466..352T |issn=1476-4687|hdl=10852/62003 |hdl-access=free }}</ref>

Moreover, kimberlites are unique in their ability to transport material from the Earth's mantle to its surface. This process, known as xenolith transport, provides geologists with samples of the Earth's mantle, which are otherwise inaccessible. Analyzing these samples has led to significant advances in our knowledge of the Earth's deep interior, including its physical conditions, composition, and the evolutionary history of the planet.

The role of kimberlites in diamond exploration cannot be overstated. Diamonds are formed under the high-pressure, high-temperature conditions of the Earth's mantle. Kimberlites act as carriers for these diamonds, transporting them to the Earth's surface. The discovery of diamond-bearing kimberlites in the 1870s in Kimberley sparked a [[diamond rush]], transforming the area into one of the world’s largest diamond-producing regions. Since then, the association between kimberlites and diamonds has been crucial in the search for new diamond deposits around the globe.<ref>{{Cite journal |last=Janse |first=A. J. A. (Bram) |date=2007-06-01 |title=Global Rough Diamond Production Since 1870 |url=http://dx.doi.org/10.5741/gems.43.2.98 |journal=Gems & Gemology |volume=43 |issue=2 |pages=98–119 |doi=10.5741/gems.43.2.98 |issn=0016-626X|url-access=subscription }}</ref><ref>{{Cite journal |last1=Dasgupta |first1=Rajdeep |last2=Hirschmann |first2=Marc M. |date=2010-09-15 |title=The deep carbon cycle and melting in Earth's interior |url=https://www.sciencedirect.com/science/article/pii/S0012821X10004140 |journal=Earth and Planetary Science Letters |volume=298 |issue=1 |pages=1–13 |doi=10.1016/j.epsl.2010.06.039 |bibcode=2010E&PSL.298....1D |issn=0012-821X|url-access=subscription }}</ref>

Kimberlites also serve as a window into the Earth's past, offering clues about the formation of continents and the dynamic processes that shape our planet. Their distribution and age can provide insights into ancient continental movements and the assembly and breakup of [[supercontinent]]s.<ref>{{Cite journal |last1=Torsvik |first1=Trond H. |last2=Cocks |first2=L. Robin M. |date=January 2013 |title=Chapter 2 New global palaeogeographical reconstructions for the Early Palaeozoic and their generation |url=http://dx.doi.org/10.1144/m38.2 |journal=Geological Society, London, Memoirs |volume=38 |issue=1 |pages=5–24 |doi=10.1144/m38.2 |issn=0435-4052|url-access=subscription }}</ref>

== Economic importance ==

Kimberlites are the most important source of primary [[diamonds]]. Many kimberlite pipes also produce rich [[alluvial]] or [[eluvial]] diamond [[placer deposit]]s. {{As of|2014}} about 6,400 kimberlite pipes are known on Earth including about 900 that have been found to contain diamonds, with mining of diamonds occurring at about 30 pipes.<ref name=Mining.com>{{cite web|title=Diamond investing FAQ|url=http://www.mining.com/diamond-investing-faq-40055/|website=MINING.com|access-date=30 August 2017|date=18 February 2014}}</ref>

The discovery of diamond-rich kimberlite pipes in northern Canada during the early 1990s serves as a prime example of how challenging these deposits can be to locate, as their surface features are often subtle. In this case, the pipes were hidden beneath ice-covered shallow ponds, which filled depressions formed by the softer kimberlite rock eroding slightly faster than the surrounding harder rock.<ref>{{Cite web |date=2024-05-08 |title=Secrets Beyond the Sparkle |url=https://www.americanscientist.org/article/secrets-beyond-the-sparkle |access-date=2024-09-05 |website=American Scientist |language=en}}</ref>
 
The deposits occurring at [[Kimberley, Northern Cape|Kimberley]], [[South Africa]], were the first recognized and the source of the name. The Kimberley [[diamond]]s were originally found in [[weathering|weathered]] kimberlite, which was colored yellow by [[limonite]], and so was called "yellow ground". Deeper workings encountered less altered rock, [[serpentinite|serpentinized]] kimberlite, which miners call "blue ground". Yellow ground kimberlite is easy to break apart and was the first source of diamonds to be mined. Blue ground kimberlite needs to be run through [[rock crusher]]s to extract the diamonds.<ref name="Schumann 2006 p. 88">{{cite book | last=Schumann | first=W. | title=Gemstones of the World | publisher=Sterling | year=2006 | isbn=978-1-4027-4016-9 | url=https://books.google.com/books?id=uXCzger619QC&pg=PA88 | access-date=2022-07-15 | page=88}}</ref>
[[File:Mirny in Yakutia.jpg|thumb|Mir mine]]
See also [[Mir Mine]] and [[Udachnaya pipe]], both in the [[Sakha Republic]], [[Siberia]].

The blue and yellow ground were both prolific producers of diamonds. After the yellow ground had been exhausted, miners in the late 19th century accidentally cut into the blue ground and found gem-quality diamonds in quantity. The economic situation at the time was such that, with a flood of diamonds being found, the miners undercut each other's prices and eventually decreased the diamonds' value down to cost in a short time.<ref>"South Africa: A New History of the Development of the Diamond Fields" (1902): New York Times Archives, ''New York Times''.</ref>

== Related rock types ==

* {{annotated link|Lamproite}}
* {{annotated link|Lamprophyre}}
* {{annotated link|Nepheline syenite}}
* {{annotated link|Ultrapotassic igneous rocks}}

==References==
{{reflist|30em}}

==Further reading==
{{refbegin}}
* {{cite book |title=Petrology of Lamproites |last=Mitchell |first=R. H. |author2=Bergman, S. C.  |year=1991 |publisher=Plenum Press |location=New York |isbn=978-0-306-43556-0 }}
* Edwards, C. B., Howkins, J. B., 1966. Kimberlites in Tanganyika with special reference to the Mwadui occurrence. Econ. Geol., 61:537-554.
* {{cite web|last1=Kopylova|first1=Maya G.|title=Definition of Kimberlite|url=https://www.eoas.ubc.ca/research/diamonds/kopylova/intro/definition.html|website=Diamond Exploration Laboratory|publisher=University of British Columbia|access-date=30 August 2017}}
* Nixon, P. H., 1995.  The morphology and nature of primary diamondiferous occurrences.  Journal of Geochemical Exoloration, 53: 41–71.
* {{cite book|last1=Pell|first1=Jennifer|chapter=Kimberlite-hosted Diamonds|chapter-url=http://www.unalmed.edu.co/~rrodriguez/MODELOS/columbia/KIMBERLITE-HOSTED%20DIAMONDS.htm|title=Geological Fieldwork 1997. Paper 1998-1|pages=24L–1&ndash;24L–4|publisher=British Columbia Ministry of Employment and Investment|access-date=30 August 2017|url-status=dead|archive-url=https://web.archive.org/web/20160404230700/http://www.unalmed.edu.co/~rrodriguez/MODELOS/columbia/KIMBERLITE-HOSTED%20DIAMONDS.htm|archive-date=4 April 2016}}
* Woolley, A. R., Bergman, S. C., Edgar, A. D., Le Bas, M. J., Mitchell, R. H., Rock, N. M. S., Scott Smith, B. H., 1996. Classification of lamprophyres, lamproites, kimberlites, and the kalsilitic, melilitic, and leucitic rocks. ''The Canadian Mineralogist'', Vol 34, Part 2. pp.&nbsp;175–186.
* {{cite web|url=https://science.ubc.ca/news/geologists-find-lost-fragment-ancient-continent-canada%E2%80%99s-north|author=Kopylova|title=Geologists find lost fragment of ancient continent in Canada's North. See the interesting citation from the main author: "For researchers, kimberlites are subterranean rockets that pick up passengers on their way to the surface," explains University of British Columbia geologist Maya Kopylova. "The passengers are solid chunks of wall rocks that carry a wealth of details on conditions far beneath the surface of our planet over time."|date=19 March 2020|work=science.ubc.ca|access-date=21 March 2020}}
{{refend}}

==External links==
{{Commons category|Kimberlite}}
* [http://earthphysicsteaching.homestead.com/Kimberlite.html Kimberlite image gallery]. Retrieved 2012-02-10.

{{Igneous rocks}}
{{Rock type}}
{{Geology of South Africa|minerals}}

[[Category:Ultrapotassic rocks]]
[[Category:Ultramafic rocks]]
[[Category:Subvolcanic rocks]]
[[Category:Economic geology]]
[[Category:Diamond]]
[[Category:Kimberley, Northern Cape]]