How is nepheline syenite made?

Nepheline syenite and phonolite may be derived by crystal fractionation from more mafic silica-undersaturated mantle-derived melts, or as partial melts of such rocks. Igneous rocks with nepheline in their normative mineralogy commonly are associated with other unusual igneous rocks such as carbonatite.

Where can nepheline syenite be found?

Nepheline Syenite is an anhydrous sodium potassium alumino silicate. Although feldspar-like in its chemistry, mineralogically it is an igneous rock combination of nepheline, microcline, albite and minor minerals like mica, hornblende and magnetite. It is found in Canada, India, Norway and USSR.

Where is nepheline syenite found in India?

Nepheline Syenite, Kishangarh, Ajmer District, Rajasthan is a pluton emplaced along the core of an antiform of metamorphites in Aravalli craton of Rajasthan. Kishangarh syenite, by which the unit is also called has been dated 1590 million years to 1910 million years.

What is the volcanic equivalent of nepheline syenite?

phonolite
Nepheline syenite is a pale-colored, coarse-grained rock composed essentially of alkali feldspar (ca. 70%) and nepheline (ca. 20%) with minor proportions of dark minerals such as sodic pyroxene, sodic hornblende, or biotite; its volcanic equivalent is phonolite.

How is syenite formed?

Formation of syenites Syenites are products of alkaline igneous activity, generally formed in thick continental crustal areas, or in Cordilleran subduction zones. To produce a syenite, it is necessary to melt a granitic or igneous protolith to a fairly low degree of partial melting.

How is syenite made?

What is the difference between granite and syenite?

Chemically, syenites contain a moderate amount of silica, relatively large amounts of alkalies, and alumina. The name was first used by Pliny the Elder. The texture of syenites, like that of granite, is granular, and these rocks differ from granite only by the absence or scarcity of quartz.

What is the chemical composition of syenite?

Syenite is a coarsely crystalline plutonic intermediate rock consisting chiefly of alkali feldspar with less than 5% quartz and/or feldspathoid. Clinopyroxene, hornblende, biotite mica, or olivine may be present in minor proportions.

Is syenite a fluorescent?

In most cases, syenite is not fluorescent. In most cases, sodalite is also not fluorescent.