kimberlite


Also found in: Dictionary, Thesaurus, Medical, Financial, Wikipedia.

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
..... Click the link for more information.
.

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

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.
References in periodicals archive ?
Wood says it was a long process to evaluate the first kimberlite pipe which didn't appear very economic in the beginning.
Diamond hunters normally range over the calm continental interiors where kimberlites are found, but Nixon suggests the plate margins deserve a closer look.
The discovery of diamond-bearing kimberlites and other significant indicator minerals in Northern Ontario has sparked increases in diamond exploration.
In the northeast, these kimberlites form in small clusters following an imaginary line from Attawapiskat on the James Bay Coast down through Kirkland Lake, Cobalt and extends down to southern Ontario, through to New York.
Kimberlites (the indicator mineral for diamond) have always existed in this part of northeastern Ontario, but early exploration ventures in the early 1980s turned up barren kimberlites.
In the southern portion of Temagami, extensive airborne magnetic surveys were performed, as well as sampling for kimberlite indicator minerals (KIM).
The Brauna project comprises three exploration concessions which now encompass four known kimberlite pipes, or blows, namely Brauna 3, 4, 7 and 16.
The current drilling campaign by Vaaldiam and Majescor on the Brauna 3 pipe now indicates that the kimberlite has a surface area of approximately 1.
The kimberlite was originally believed to be 400 metres long and 250 metres wide, but new interpretation of the data indicated the anomaly is about 700 metres long and 300 metres wide.
Anglo Swiss is the majority holder of over 170,000 acres of claims of merit in under explored areas with unexplained kimberlite indicator mineral trains and/or kimberlite targets near known kimberlites and diamond mining operations.
Sudbury Contact reactivated diamond exploration on its properties in the New Liskeard area and is currently conducting a hulk-sampling program on its 92-2 kimberlite pipe.
TSX VENTURE:DGM) ("Diagem" or the "Company") reports that the preliminary results of 40 bulk samples of the in situ eluvial gravels overlying the Collier-04 kimberlite pipe have been received.