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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 ...
Nepheline syenite is a holocrystalline plutonic rock that consists largely of nepheline and alkali feldspar. [1] The rocks are mostly pale colored, grey or pink, and in general appearance they are not unlike granites , but dark green varieties are also known.
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.
Nepheline syenite – Holocrystalline plutonic rock – A silica-undersaturated plutonic rock of nepheline and alkali feldspar; Nephelinite – Igneous rock made up almost entirely of nepheline and clinopyroxene – A silica-undersaturated plutonic rock with >90% nepheline; Norite – Mafic intrusive igneous rock – A hypersthene-bearing gabbro
Litchfieldite (nepheline syenite gneiss) from Canaã Massif, Brazil. Litchfieldite is a rare igneous rock.It is a coarse-grained, foliated variety of nepheline syenite, [1] sometimes called nepheline syenite gneiss or gneissic nepeheline syenite. [2]
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.
The Coldwell Complex is a large circular gabbro and syenite intrusion within the Earth's crust. Located on the North Shore of Lake Superior in Ontario , Canada , it is the largest alkaline intrusion in North America with a diameter of 25 km (16 mi).
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 ...