Igneous Rock Compositions Felsic composition is higher in silica (SiO2) and low in iron (Fe) and magnesium (Mg). Mafic composition is higher in iron and magnesium and lower in silica. Intermediate compositions contain silica, iron, and magnesium in amounts that are intermediate to felsic and mafic compositions.
What are the differences between felsic mafic and intermediate composition igneous rocks?
In a widely accepted silica-content classification scheme, rocks with more than 65 percent silica are called felsic; those with between 55 and 65 percent silica are intermediate; those with between 45 and 55 percent silica are mafic; and those with less than 45 percent are ultramafic.
What is the difference between felsic and mafic igneous rocks?
Chemically, mafic rocks are enriched in iron, magnesium and calcium and typically dark in color. In contrast, the felsic rocks are typically light in color and enriched in aluminium and silicon along with potassium and sodium. The mafic rocks also typically have a higher density than felsic rocks.
What are the differences between the two types of igneous rocks in terms of composition?
The two main categories of igneous rocks are extrusive and intrusive. Extrusive rocks are formed on the surface of the Earth from lava, which is magma that has emerged from underground. Intrusive rocks are formed from magma that cools and solidifies within the crust of the planet.
What are three differences between mafic igneous rocks and felsic igneous rocks?
Mafic is rich in heavy minerals like magnesium and ferric, or iron. But Felsic is rich in silica and aluminium. Felsic is also rich in low-density minerals like oxygen, sodium and potassium. Thus, these rocks have low density unlike mafic rock, which have high density are heavy.
What is an intermediate igneous rock?
Igneous rocks are classified according to their mineral content: Intermediate rocks are roughly even mixtures of felsic minerals (mainly plagioclase) and mafic minerals (mainly hornblende, pyroxene, and/or biotite). There is little or no quartz.
What is the difference between felsic and mafic based on their characteristics?
Mafic minerals are usually dark in color and have relatively high specific gravities ( greater than 3.0 ). Felsic minerals are usually light in color and have specific gravities less than 3.0. Common felsic minerals include quartz, muscovite mica, and the orthoclase feldspars.
What is the similarities of felsic and intermediate?
Felsic rocks are commonly oversaturated and contain free quartz (SiO 2), intermediate rocks contain little or no quartz or feldspathoids (undersaturated minerals), and mafic rocks may contain abundant feldspathoids. 2-B1-2), are similar to active continental margin granitoids.
How are intermediate rocks formed?
Intermediate rocks are produced primarily in convergent plate boundaries in which an oceanic plate is subducting beneath either another oceanic plate (such as in Japan) or a continental plate (such as along the Andes Mountains of South America).
Why do igneous rocks have different textures?
Explanation: The faster the magma cools that smaller the crystals that are formed. Some magma from which the igneous rocks is form come from different combinations of remelted igneous rocks, metamorphic rocks and sedimentary layers. The different sources of the melted material affects the textures of the igneous rocks.
What is felsic igneous rock?
In geology, felsic is an adjective describing igneous rocks that are relatively rich in elements that form feldspar and quartz. Felsic magma or lava is higher in viscosity than mafic magma/lava. Felsic rocks are usually light in color and have specific gravities less than 3.
What is the difference between fine grained and coarse grained igneous rock?
Coarse grain varieties (with mineral grains large enough to see without a magnifying glass) are called phaneritic. Granite and gabbro are examples of phaneritic igneous rocks. Fine grained rocks, where the individual grains are too small to see, are called aphanitic. Basalt is an example.
Are felsic rocks less dense than mafic?
Mafic rocks are denser and heavier than Felsic rocks. Mafic rocks are darker in color than Felsic rocks. Lava made up of Felsic rocks is slow moving and has a higher viscosity than Mafic lava.
Is mafic or felsic more viscous?
Composition: he more felsic the lava (the more silica in the lava), the higher the viscosity because silica forms chains in the cooling lava even before it crystallizes. The more mafic the lava (the less silica in it), the lower the viscosity.
What are the major minerals in felsic igneous rocks and in mafic igneous rocks?
The major mineralogical components of igneous rocks can be divided into two groups: felsic (from feldspar and silica) and mafic (from magnesium and ferrous iron).