You can also expect to see quartz, muscovite, potassium feldspar, and maybe a little biotite and Na-rich plagioclase in a felsic or silicic rock such as granite or rhyolite. Figure 8. In Figure 8. Notice that the felsic rocks can have a small amount of dark-colored ferromagnesian minerals, but is predominately composed of light-colored minerals, whereas the mafic rock has a higher percentage of dark-colored ferromagnesian minerals, which results in a darker-colored rock. A rock that is considered intermediate between the mafic and felsic rocks is truly an intermediate in terms of the color and mineral composition; such a rock would have less ferromagnesian minerals than the mafic rocks, yet more ferromagnesian minerals than the felsic rocks.
They are dark in colour whereas felsic rocks are light in colour. Chemically, these rocks are consist of magnesium, iron, and calcium. Mafic magma has a low content of silica because of which before cooling, mafic lava has a low viscosity. The volcanic eruptions consist of mafic lava are less explosively violent as compared to felsic volcanic eruptions. On the basis of the texture of rocks, different names of mafic rocks are given below in the table:. Name of Mafic Rocks. Gabbro pegmatite.
Coarse grained - Phaneritic. Coarse grained - Porphyritic. Porphyritic Gabbro. Fine grained - aphanitic. Fine grained - Porphyritic. Porphyritic basalt. Basalt tuff or breccia. Vesicular basalt. Amygdaloidal basalt. Of or relating to an igneous rock in which the crystals are so coarse that individual minerals can be distinguished with the naked eye.
Phaneritic rocks are intrusive rocks that cooled slowly enough to allow significant crystal growth. Compare aphanitic. Mafic igneous rocks are generally more dense than felsic igneous rocks. Higher metamorphic grade rocks such as eclogite and amphibolite are more dense than low grade metamorphic rocks such as slate and phyllite. Intrusive igneous rocks cool from magma slowly because they are buried beneath the surface, so they have large crystals.
Extrusive igneous rocks cool from lava rapidly because they form at the surface, so they have small crystals. Texture reflects how an igneous rock formed. Mafic is used for silicate minerals, magmas, and rocks which are relatively high in the heavier elements. The term is derived from using the MA from magnesium and the FIC from the Latin word for iron, but mafic magmas also are relatively enriched in calcium and sodium.
Granite and rhyolite are considered felsic , while basalt and gabbro are mafic click here for more information on mafic and felsic. In simple terms, gabbro is just the cooled magma chamber for the basaltic flows that erupt at the surface. For instance, the name of a coarse - grained intrusive igneous rock with a felsic composition is granite whereas the name of the fine - grained extrusive rock with a similar composition is rhyolite.
As ultramafic magmas encounter the felsic rocks of the continental crust, they cause the most felsic minerals in those felsic rocks the ones with the lowest melting point to melt. Thus, felsic material is added to the magma as mafic material is lost to fractional crystalization.
Diorite is a plutonic igneous rock with intermediate composition between mafic and felsic rocks. It is visibly crystalline and usually has a granular texture composed of roughly equally sized crystals although the appearance may vary widely. Intrusive igneous rocks crystallize below Earth's surface, and the slow cooling that occurs there allows large crystals to form.
Examples of intrusive igneous rocks are diorite, gabbro, granite, pegmatite, and peridotite. Extrusive igneous rocks erupt onto the surface, where they cool quickly to form small crystals. Magma is a molten and semi-molten rock mixture found under the surface of the Earth. This mixture is usually made up of four parts: a hot liquid base, called the melt; minerals crystallized by the melt; solid rocks incorporated into the melt from the surrounding confines; and dissolved gases.
What are the characteristics of mafic rocks? Category: science geology.
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