Silicic is an adjective to describe magma or igneous rock rich in silica. The amount of silica that constitutes a silicic rock is usually defined as at least 63 percent.[1] Granite and rhyolite are the most common silicic rocks.
Silicic is the group of silicate magmas which will eventually crystallise a relatively small proportion of ferromagnesian silicates, such as amphibole, pyroxene, and biotite. The main constituents of a silicic rock will be minerals rich in silica-minerals, like silicic feldspar or even free silica as quartz. These are just part of all the other silicate minerals that make up 90% of the earth's crust.
This broad classification is refined in practice based on more detained compositional studies where ever possible in the science of mineralology.
Example
The "Shammar group" is a silicic and volcaniclastic sequence in northwestern Saudi Arabia.[2]
See also
References
- ^ "USGS Volcano Hazards Program Glossary - Silicic". USGS. 2013-09-19. Retrieved 2016-01-02.
- ^ Kellogg, Karl S. (1984), Reconnaissance geology of the Qufar Quadrangle, sheet 27/41 D, Kingdom of Saudi Arabia (PDF), Denver: United States Geological Survey, pp. 1–33, retrieved 2019-01-06