Distribution
Nepheline syenites and phonolites occur in Canada, Norway, Greenland, Sweden, the Ural Mountains, the Pyrenees, Italy, Brazil, China, the Transvaal region, and Magnet Cove igneous complex of Arkansas, as well as on oceanic islands.
Phonolite lavas formed in the East African rift in particularly large quantity, and the volume there may exceed the volume of all other phonolite occurrences combined, as discussed by Barker (1983).
Nepheline-normative rocks occur in close association with the Bushveld Igneous Complex, possibly formed from partial melting of the wall rocks to that large ultramafic layered intrusion.
Nepheline syenites are rare; there is only one occurrence in Great Britain and one in France and Portugal. They are known also in Bohemia and in several places in Norway, Sweden and Finland. In the Americas these rocks have been found in Texas, Arkansas, New Jersey (Beemerville Complex) and Massachusetts, also in Ontario, British Columbia and Brazil. South Africa, Madagascar, India, Tasmania, Timor and Turkestan are other localities for the rocks of this series.
Rocks of this class also occur in Brazil (Serra de Tingua) containing sodalite and often much augite, in the western Sahara and Cape Verde Islands; also at Zwarte Koppies in the Transvaal, Madagascar, São Paulo in Brazil, Paisano Pass in West Texas and Montreal, Canada. The rock of Salem, Massachusetts, United States, is a mica-foyaite rich in albite and aegirine: it accompanies granite and essexite. Litchfieldite is another well-marked type of nepheline-syenite, in which albite is the dominant feldspar. It is named after Litchfield, Maine, United States, where it occurs in scattered blocks. Biotite, cancrinite and sodalite are characteristic of this rock. A similar nepheline-syenite is known from Hastings County, Ontario, and contains hardly any orthoclase, but only albite feldspar. Nepheline is very abundant and there is also cancrinite, sodalite, scapolite, calcite, biotite and hornblende. The lujaurites are distinguished from the rocks above described by their dark color, which is due to the abundance of minerals such as augite, aegirine, arfvedsonite and other kinds of amphibole. Typical examples are known near Lujaur on the White Sea, where they occur with umptekites and other very peculiar rocks. Other localities for this group are at Julianehaab in Greenland with sodalite-syenite; at their margins they contain pseudomorphs after leucite. The lujaurites frequently have a parallel-banding or gneissose structure. Sodalite-syenites in which sodalite very largely or completely takes the place of nepheline occur in Greenland, where they contain also microcline-perthite, aegirine, arfvedsonite and eudialyte.
Cancrinite syenite, with a large percentage of cancrinite, has been described from Dalekarlia, Sweden and from Finland. We may also mention urtite from Lujaur Urt on the White Sea, which consists very largely of nepheline, with aegirine and apatite, but no feldspar. Jacupirangite (from Jacupiranga in Brazil) is a blackish rock composed of titaniferous augite, magnetite, ilmenite, perofskite and nepheline, with secondary biotite.
Read more about this topic: Nepheline Syenite
Famous quotes containing the word distribution:
“In this distribution of functions, the scholar is the delegated intellect. In the right state, he is, Man Thinking. In the degenerate state, when the victim of society, he tends to become a mere thinker, or, still worse, the parrot of other men’s thinking.”
—Ralph Waldo Emerson (1803–1882)
“My topic for Army reunions ... this summer: How to prepare for war in time of peace. Not by fortifications, by navies, or by standing armies. But by policies which will add to the happiness and the comfort of all our people and which will tend to the distribution of intelligence [and] wealth equally among all. Our strength is a contented and intelligent community.”
—Rutherford Birchard Hayes (1822–1893)
“The question for the country now is how to secure a more equal distribution of property among the people. There can be no republican institutions with vast masses of property permanently in a few hands, and large masses of voters without property.... Let no man get by inheritance, or by will, more than will produce at four per cent interest an income ... of fifteen thousand dollars] per year, or an estate of five hundred thousand dollars.”
—Rutherford Birchard Hayes (1822–1893)