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Syenite from Corsica QAPF diagram that shows the quartz (Q), alkali feldspar (A), and plagioclase (P) composition of syenite Leucocratic variety of nepheline syenite from Sweden Syenite is a coarse-grained intrusive igneous rock with a general composition similar to that of granite , but deficient in quartz , which, if present at all, occurs in ...
The Concord Gabbro-Syenite Complex within the Concord pluton is dated to 407 ± 36 Ma, [4] making it the oldest formation within the twenty plutons. It is thought unlikely that the plutons located within the Concord Suite formation spanned this much time, implying that complexes such as the Concord Gabbro-Syenite Complex most likely formed ...
A worldwide average of the major elements in nepheline syenite tabulated by Barker (1983) is listed below, expressed as weight percent oxides. Nepheline syenite is characterized by high ratio of (Na 2 O+K 2 O)/SiO 2 and (Na 2 O+K 2 O)/Al 2 O 3, which are represented respectively by the existence of nepheline and alkaline mafic minerals ...
The Red Hill syenite is a medium- to coarse-grained syenite. The six units of the Red Hill Syenite all contain primarily alkali feldspar, with many rocks displaying perthitic igneous texture. The perthites range from microperthite (lamellae barely visible or not visible to the naked eye) to very coarse exsolution textures.
It is a coarse-grained, foliated variety of nepheline syenite, [1] sometimes called nepheline syenite gneiss or gneissic nepeheline syenite. [2] Litchfieldite is composed of two varieties of feldspar (mostly albite but also some microcline ), with nepheline , sodalite , cancrinite and calcite .
A notable exception where feldspathoids and quartz-bearing rocks are found together is the Red Hill Syenite. [1] Foid, a contraction of the term feldspathoid, is applied to any igneous rock containing up to 60% modal feldspathoid minerals.
Pink eudialyte in syenite from Poços de Caldas, Brazil.The white mineral is alkali feldspar, the black is aegirine, and the little brown bits are biotite.. Eudialyte, whose name derives from the Greek phrase Εὖ διάλυτος, eu dialytos, meaning "well decomposable", is a somewhat rare, nine-member-ring cyclosilicate mineral, which forms in alkaline igneous rocks, such as nepheline ...
Kakortokite, a variety of agpaitic nepheline syenite, from the Ilimaussaq intrusive complex, Greenland. An agpaitic rock is a peralkaline igneous rock, typically nepheline syenite or phonolite. Characteristic minerals in these rocks include complex silicates containing zirconium, titanium, sodium, calcium, the rare-earth elements, and fluorine.