Alkali feldspar granite Alkali feldspar granite Alkali feldspar granite, some varieties of which are called 'red granite', is a felsic igneous rock and a type of granite rich in the mineral potassium feldspar (K-spar). It is a dense rock with a phaneritic texture. The abundance of K-spar gives the rock a predominant pink to reddish hue; peppered with minor amounts of black minerals. As shown in the QAPF diagram, alkali feldspar granite contains between 20% - 60% quartz. Less quartz content would lead to "quartz alkali feldspar syenite". More than 90% of the total feldspar content is in the form of alkali feldspar.
A-type granite magnesium. There are lower levels of calcium and strontium. By using Ga/Al ratio, fractionated felsic I or S-type granites can overlap in apparent composition. Enriched alkalis include sodium, potassium, rubidium and caesium. Other depleted elements include barium, phosphorus, titanium and europium. Subtypes include A, anorogenic, derived from ocean island basalt; and A post-orogenic, derived by crustal melting or crust and mantle mixing. The source could be dry granulite left over from the loss of wet magma during orogenies. A-type granite A-type granites are a class of granite. They are characterised by low water and a lack of tectonic fabric. A