alkali feldspar


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Related to alkali feldspar: Plagioclase feldspar, quartz, hornblende, K feldspar

alkali feldspar

[′al·kə‚lī ′feld‚spar]
(mineralogy)
A feldspar composed of potassium feldspar and sodium feldspar, such as orthoclase, microcline, albite, and anorthoclase; all are considered alkali-rich.
References in periodicals archive ?
The phenocrysts of plagioclase, hornblende, alkali feldspar and quartz are set in a felsophyric groundmass in a variable amount.
Quartz is low to moderate in abundance and feldspar is in significant proportion with plagioclase: alkali feldspar ratio high.
Alkali feldspars are represented by orthoclase and microcline.
It consists mainly of perthitic alkali feldspar and quartz, and mafic minerals are less abundant than in the quartz alkali-feldspar syenite to alkali-feldspar syenite (Fig.
The degree of porosity depends on the composition of the parent feldspar grain, with plagioclase producing a dense clay matrix and alkali feldspar a highly porous clay matrix.
Acid igneous rock fragments: composed of quartz, alkali feldspar, plagioclase feldspar, and occasional muscovite/and or biotite mica, amphibole, and microcline.
The most common rocks within the KZ-25 borehole are leucogranite and alkali feldspar syenite (Table 1).
Tapponnier (1993), High cooling and denudation rates at Kongur Shan, eastern Pamir (Xinjiang, China) revealed by 40Ar/39Ar alkali feldspar thermochronology, Tectonics, 12, 1335-1346.
The dyke a]so contains abundant phenocrysts and cognate xenocrysts of kaersutite, biotite, and magnetite, and xenocrysts of a]bite and alkali feldspar.
Alkali feldspar occurs as interstitial grains or antiperthitic inclusions in plagioclase.