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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 ...
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 .
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.
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.
Case hardening is a weathering phenomenon of rock surface induration.It is observed commonly in: felsic alkaline rocks, such as nepheline syenite, phonolite and trachyte; pyroclastic rocks, as pyroclastic flow deposit, fine air-fall deposits and vent-filling pyroclastic deposits; sedimentary rocks, as sandstone and mudstone.
[1] [2] The complex is chiefly made up of peralkaline nepheline syenite and is rich in exotic minerals. [1] Rocks of the complex intruded into the Paleoproterozoic-aged Växjo granites of the Transscandinavian Igneous Belt. [1] [2] Alfred Elis Törnebohm was the first to describe the rocks of Norra Kärr in 1906.