kimberlite


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kimberlite:

see diamonddiamond,
mineral, one of two crystalline forms of the element carbon (see allotropy), the hardest natural substance known, used as a gem and in industry. Properties
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The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Kimberlite

 

(named after the city of Kimberley in the Republic of South Africa), an ultrabasic, brecciated igneous rock of effusive habit that fills volcanic pipes. The rock consists essentially of olivine, pyroxenes, garnet of the pyrope-almandine series, picroilmenite, and phlogopite and more rarely zircon, apatite, and other minerals that are surrounded by a fine-grained groundmass. The groundmass has usually been altered by post-volcanic processes to serpentine-carbonate with perovskite and chlorite.

Kimberlite also contains inclusions of other rocks (xenoliths) of two types: (1) plutonic ultrabasic and basic rocks (pyropeolivine ultrabasites, eulysites, and eclogites, which contain corundum, rutile, and graphite), and (2) crustal rock such as granites, crystaline schists, and sandstones. The quantity of the second rock type may be so great that it is difficult to establish the igneous nature of the kimberlite.

Kimberlite is the basic source of diamonds. The diamonds usually occur in the kimberlite itself and may also occur in the inclusions of the plutonic rock and even in the minerals of these rocks. It is thought that the kimberlite-bearing pipes formed as a result of explosions and that the pipes became filled with material that was carried up from great depths where the diamonds and pyrope formed under great pressure. The size of these pipes varies from several square meters to thousands of square meters (for example, the area of the Mwadui pipe in Tanzania is 1,068 × 1,525 m). With increasing depth the cross sections of the pipes decrease, and they become narrow dikes. In addition to volcanic pipes, kimberlites fill some cavities in the earth’s crust, forming veins, dikes, and sheet-like deposits (sills).

Kimberlite occurs, as a rule, on ancient platforms and very rarely in geosynclinal areas. More than 1,500 kimberlite bodies are known to exist, but only 8–10 percent of them are diamond-bearing. Kimberlites with a diamond content of at least 0.3–0.5 carats per cu m are considered of commercial importance. Some of the kimberlite pipes are very large producers. Thus, more than 65 million carats have been taken from the Premier Mine in the Republic of South Africa. Kimberlites are most widely distributed in the USSR (Yakut ASSR) and abroad in Africa, India, and North America.

REFERENCES

Trofimov, V. S. Osnovnye zakonomernosti razmeshcheniia i obrazovaniia almaznykh mestorozhdenii na drevnikh platformakh i ν geosinklinal’nykh oblastiakh. Moscow, 1967.
Trofimov, V. S. “O termine ’kimberlit’.” Izv. AN SSSR: Ser. geologicheskaia, 1970, no. 11.
Trofimov, V. S. “Prirodnye almazy.” Priroda, 1972, no. 3.

V. S. TROFIMOV

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.

kimberlite

[′kim·bər‚līt]
(petrology)
A form of mica periodite that is formed mainly of phenocrysts, olivine, phlogopite, and subordinate melilite with minor amounts of pyroxene, apatite, perovskite, and opaque oxides.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
Forward-looking statements in this press release include that the Timantti Project offers high potential for numerous further diamond-bearing kimberlite discoveries; Arctic's drilling and surveying plans and the expected outcome of those plans; that Arctic can swiftly discover more kimberlite on the property; that the Wolf kimberlites themselves may have the potential to be economic
The kimberlite deposit is also confirmation of how continents drift.
Beaumier, M., Togola, N., Moorhead, J., and Faure, S., 2004, Diamonds, kimberlite pipes and deep-seated lineaments in Quebec: Ministere des Ressources naturelles, Quebec, Poster--[www.mrnf.
Petra's 2003 work programme, approved last year by Endiama, envisages two drill rigs: one operating on the kimberlite discovered by Petra and the other traversing the concession to explore the other known kimberlites and anomalies.
At a later stage, separate circuits can be added to crush hard kimberlite ore and recover water.
The site was resampled in August 1996 and data just released showed a slightly higher concentration of the garnets, which indicate the possible presence of diamond-bearing kimberlite.
They are adjacent to eleven mining leases acquired from GGL in 2013 that included the diamondiferous Doyle Lake kimberlite.