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Felsic magmas and lavas have lower temperatures of melting and solidification than mafic magmas and lavas. Felsic rocks are usually light in color and have specific gravities less than 3. The most common felsic rock is granite. Common felsic minerals include quartz, muscovite, orthoclase, and the sodium-rich plagioclase feldspars (albite-rich).
Rhyodacite – Volcanic rock rich in silica and low in alkali metal oxides – A felsic volcanic rock which is intermediate between a rhyolite and a dacite; Rhyolite – Igneous, volcanic rock, of felsic (silica-rich) composition Comendite – Hard, peralkaline igneous rock, a type of light blue grey rhyolite
Since mafic rocks (contain low silica content, such as basalt) are lack of zircon, only the age of felsic rocks can be dated among the volcanic rocks in greenstone belts. [14] As felsic volcanic rocks are episodically deposited in between mafic layers, the age range of a particular mafic layer can be constrained by the upper and lower felsic ...
Felsic intrusions (3 P) R. ... Pages in category "Felsic rocks" The following 10 pages are in this category, out of 10 total. This list may not reflect recent changes. A.
Rocks with low color indices are felsic, and those with higher color indices are mafic, [6] although the exact thresholds used vary. This terminology conflicts with the definition [7] [8] of felsic and mafic rocks based on silica content. [6] For example, a rock composed entirely of pyroxene would contain about 50% silica. [6]
This rock is typically of extrusive origin, formed by compaction of fine volcanic ash, and may be found in association with obsidian and rhyolite. In some cases, it is sufficiently fine-grained for use in making stone tools. Its fine texture and felsic components allow for good knapped pieces, much like working chert, producing conchoidal fracture.
Photomicrograph of a porphyritic-aphanitic felsic rock, from the Middle Eocene in the Blue Ridge Mountains of Virginia. Plagioclase phenocrysts (white) and hornblende phenocryst (dark; intergrown with plagioclase) are set in a fine matrix of plagioclase laths that show flow structure.
QAPF diagram with rhyolite field highlighted TAS diagram with rhyolite field highlighted. Rhyolite is an extrusive igneous rock, formed from magma rich in silica that is extruded from a volcanic vent to cool quickly on the surface rather than slowly in the subsurface.