Nepheline Syenite

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nepheline syenite

[′nef·ə‚lēn ′sī·ə‚nīt]
(petrology)
A phaneritic plutonic rock with granular texture, composed largely of alkali feldspar, nepheline, and dark-colored materials.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Nepheline Syenite

 

a magmatic alkali rock composed of nepheline, alkali feldspars (sanidine, orthoclase, or microcline), biotite, and alkali amphiboles and pyroxenes. It also contains zirconium-bearing silicates (zircon, eudialyte) and titanium-bearing silicates (sphene, lamprophyllite), as well as minerals containing F, P2O5, CO2 (cancrinite, calcite, apatite, fluorite) and rare earths (rinkolite, loparite). Nepheline syenite contains 50–56 percent SiO2, 19–24 percent Al2O3, a small quantity of Ca and Mg, and 15–17 percent K and Na.

There are numerous varieties of nepheline syenites, including (1) chibinites, greenish gray coarse-grained pyroxene nepheline syenites, with pegmatic texture; (2) rischorites, yellowish gray or greenish gray rocks with poikilitic texture; (3) lujauvrites, greenish black rocks with marked trachytic texture; (4) miascites, micaceous lamellar nepheline syenites found in the Urals; (5) mariupolites, distinctive albite-rich nepheline syenites; and (6) saibarites, melanocratic nepheline syenites found in Siberia and elsewhere. In addition to the USSR, nepheline-syenite deposits are also found in the vicinity of Oslo, Norway, and in southern Greenland, in Canada, in southern Africa, and on Madagascar. Nepheline syenites occur in association with apatites (Kola Peninsula), graphite (Saian Mountains), cryolite (Greenland), and a number of rare elements.

REFERENCES

Kupletskii, B. M. Formatsiia nefelinovykh sienitov SSSR. Moscow-Leningrad, 1937.
Kupletskii, B. M. “K voprosu o kolichestvenno-mineralo-gicheskom sostave fel’dshpatoidnykh porod.” Dokl. AN SSSR: Novaia seriia, 1946, vol. 52, no. 3.
The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
References in periodicals archive ?
The lithology types include gneisses of the 'Paraiba do Sul Complex'; migmatites and granites from the 'Rio Negro Complex', 'Suite Serra dos Orgaos' and 'Suite Rio de Janeiro'; intrusive bodies of the 'Rio Bonito Alkaline Complex' (syenite and nephelinesyenite); and Quaternary sediments (continental and transitional to marine/coastal), represented by marsh sediments, marine sediments, coastal sediments and alluvial sediments (Silva and Cunha 2001).
Focus would be made to take advantage of NephelineSyenite, phosphates, gemstones and metallic minerals including gold and base metals and other variety of industrial minerals and reduce damages of marble and other stones during excavation process.