Trachybasalt

It resembles basalt but has a high content of alkali metal oxides.

Minerals in trachybasalt include alkali feldspar, calcic plagioclase, olivine, clinopyroxene and likely very small amounts of leucite or analcime.

[6] Trachybasalt is not defined on the QAPF diagram, which classifies crystalline igneous rock by its relative content of feldspars and quartz.

[3][4][5] However, the U.S. Geological Survey defines trachybasalt as a mafic volcanic rock (composed of over 35% mafic minerals) in which the quartz-feldspar-feldspathoid fraction of the rock is less than 20% quartz and less than 10% feldspathoid, and in which plagioclase is between 65% and 90% of the total feldspar content.

[7] Trachybasalt is common in continental volcanism and is also found on some ocean islands.

Potassic trachybasalt from the July–August 2001 eruption of Mount Etna , Italy
Satellite image of Bayuda volcanic field in Sudan where nepheline -rich trachybasalt lavas have been erupted during the Holocene epoch [ 1 ]
TAS diagram highlighting the trachybasalt field