the bonneville salt flats in utah are examples of plutonic igneous rocks.

Granite consists mostly of quartz and alkali-feldspar, with relatively minor plagioclase feldspar and mafic minerals (biotite, muscovite and/or amphibole ).

The minerals found in the three main types of plutonic rocks are:

The different types of mafic intrusive rocks are classified on their relative amounts of olivine, pyroxene, and plagioclase. Mafic and intermediate intrusive rocks also have a significant proportion of minerals that contain iron and magnesium such as olivine, pyroxene, amphibole, and biotite. Intrusive rocks are classified on the proportion of major minerals in them, particularly the relative amounts of quartz, alkali-feldspar, and plagioclase. ► Intrusive (Plutonic) Rock Classification Silicic - high in silica (and low in magnesium and iron) Mafic - high in magnesium and iron (and low in silica) The two major divisions of igneous rocks based on composition are:

In turn, high silica rocks have less iron and magnesium, and more sodium and potassium. Low silica rocks have higher concentrations of iron and magnesium. Composition of igneous rocks is expressed as weight percent silica, which ranges from about 45 to 78 (wt % SiO2). In descending order, they are:Īlmost all igneous rocks are silicates meaning that silicon and oxygen are the two most common elements in them. Igneous rocks are mostly made of the most common elements found in the Earth’s crust. Texture and structure refer to the relationships between crystals, groundmass, vesicles, and other components of a rock. Igneous rocks are classified both by their chemical composition, mineral composition, texture, and structure.

The bonneville salt flats in utah are examples of plutonic igneous rocks.