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Igneous rocks are classified mainly by their chemical/mineral composition as felsic, intermediate, mafic, and ultramafic. These are your white and pink colored igneous rocks. Magma that rises to the surface is called lava. The term was used more broadly in older geologic literature. There are many different compositions of magma and lava. These datase… Hot gasses are often trapped in the quenched lava, forming bubbles (vesicles). The word 'felsic' was made up from parts of those words. The felsic minerals include quartz, tridymite, cristobalite, feldspars (plagioclase and alkali feldspar), … Igneous rocks are classified into two groups depending upon where the molten rock solidifies: NPS—Volcanic Landforms: Extrusive Igneous, NPS—Volcanic Landforms: Intrusive Igneous. Granite is a great example of Felsic rocks and muscovite, quartz, and some feldspar are the best examples of Felsic minerals. Describes an igneous rock of any composition that contains conspicuous phenocrysts (larger crystals) in a fine-grained groundmass. Felsic: Derived from the words feldspar and silica to describe an igneous rock having abundant light-colored minerals such as quartz, feldspars, or muscovite. • … The main minerals in igneous rocks are hard, primary ones: feldspar, quartz, amphiboles, and pyroxenes (together called "dark minerals" by geologists), as well as olivine, along with the softer mineral mica. Igneous rock - Igneous rock - Mineralogical components: 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). Intrusive, or plutonic, igneous rock forms when magma remains inside the Earth's crust where it cools and solidifies in chambers within pre-existing rock. Magma originates deep within the Earth, near active plate boundaries or hot spots. Rocks with greater than 90% felsic minerals can also be called leucocratic, meaning 'light-coloured'.Template:Citation needed Felsite is a petrologic field term used to refer to very fine-grained or aphanitic, light-colored volcanicrocks which might be later recl… Mafic is used for silicate minerals, magmas, and rocks which are relatively high in the heavier elements. Visitors to the park, from hikers to rock climbers, experience a landscape dominated by granite. Types of extrusive igneous rocks include: pumice, obsidian, andesite, rhyolite, and basalt. Felsic igneous rocks are rich in silica (in the 65-75% range, meaning the rock would be 65-75% weight percent SiO 2) and poor in iron and magnesium. Fortunately, most igneous rocks are one of three basic compositions: Felsic igneous rocks contain relatively high amounts of silicon, sodium, aluminum, potassium (Si, Na, Al, and K) and relatively low amounts of iron, magnesium, and calcium (Fe, Mg, Ca). Geology Wiki is a FANDOM Lifestyle Community. Igneous rocks (from the Greek word for "fire") form when hot, molten rock (magma) crystallizes and solidifies. Granite and rhyolite are felsic igneous rocks. Occurrence of igneous rocks can be either intrusive (plutonic) or extrusive (volcanic). Mafic vs Felsic • Mafic and Felsic are categories into which igneous rocks are classified. Igneous rocks with 0-15% dark-colored minerals (or 0-15% MCI) are the felsic rocks (Figure 8.3A), igneous rocks with 46-85% MCI are the mafic rocks (Figure 8.3C), and igneous rocks with over 85% MCI are considered ultramafic (Figure 8.3D). A pluton is an igneous intrusive rock body that has cooled in the crust. Magma originates deep within the Earth, near active plate boundaries or hot spots. Key Terms . It may seem strange to thin… National parks with excellent examples of intrusive igneous rocks include: Many national parks were founded for their geology, and Yosemite is known throughout the world for its exceptional high cliffs and rounded domes. 1). Felsic and mafic rocks, division of igneous rocks on the basis of their silica content. Basalt is another igneous rock with the aphanitic texture. Felsic igneous rocks tend to be lighter than mafic igneous rocks. It refers to those rocks rich in silicate minerals, magma, and rocks which are enriched in the lighter elements such as silicon, oxygen, aluminium, sodium, and potassium. Often the species of mafic minerals is included in the name, for instance, hornblende-bearing granite, pyroxene tonalite or augite megacrystic monzonite, because the term "granite" already assumes content with feldspar and quartz. Therefore, rocks are divided into ultramafic, mafic, intermediate, and felsic. Felsic definition, (of rocks) consisting chiefly of feldspars, feldspathoids, quartz, and other light-colored minerals. As adjectives the difference between ultramafic and felsic is that ultramafic is (geology) describing igneous rocks that contain magnesium and iron and only a very small amount of silica, such as are found in the earth’s mantle while felsic is (mineralogy) enriched in the lighter elements such as silicon, oxygen, … Felsic magmas are much more viscous than the intermediate magmas. If the rock is analyzed and found to be felsic but is metamorphic and has no definite volcanic protolith, it may be sufficient to simply call it a 'felsic schist'. Mafic igneous rocks, on the whole, tend to be dark colored, commonly black or dark gray. Divisions of igneous rocks based on chemical composition. Most mafic magma originates by melting of rocks in the mantle that are extremely rich in iron and magnesium. In order for a rock to be classified as felsic, it generally needs to contain more than 75% felsic minerals; namely quartz, orthoclase and plagioclase. Igneous rocks are classified into two groups depending upon where the molten rock solidifies: Extrusive or Intrusive. Plutonic rocks. Describes the texture of fine-grained igneous rock in which different components are not distinguishable by the unaided eye. The similarity of the term felsic to the German words Fels, meaning "rock", and felsig, meaning "rocky", is purely accidental, as feldspar is a borrowing from German Feldspat, which derives from German Feld, meaning "field". See more. Granite, pegmatite, and rhyolite are common rock structures which fit into the category of felsic igneous rocks which each have their own texture requirements. Geoscience Australia, in collaboration with the Geological Surveys, Mineral Resources Tasmania and Phil Blevin of Petrochem Consultants, started a project in 2003 focussed on the Tasmanides of eastern Australia. Pumice and obsidian also fall into this classification. Slow cooling means the individual mineral grains have a very long time to grow, forming a rock with large, visible crystals. These are both made up words used to indicate the chemical composition of silicate minerals, magmas, and igneous rocks. 1967 Shelby GT500 Barn Find and Appraisal That Buyer Uses To Pay Widow - Price Revealed - Duration: 22:15. Intermediate: 15-40% dark minerals: In between dark and light in color. -Igneous rocks in which silicates, quartz, and feldspars are the dominant minerals have a granitic composition (granitic rocks = felsic rocks). The terms felsic and mafic refer to the elemental composition of silicate minerals and igneous rocks–specifically, the amount of iron and magnesium present. Magma and Igneous Rocks. Common felsic … What do the terms mafic and felsic mean? Feldspar is a name of a group of minerals that varies in composition and bulk color. Describes an igneous rock texture in which mineral grains are large enough to be seen with the unaided eye and are of approximately equal size. Since igneous rocks are characterised by silica content in them, mafic is the one with less silica content (approx. There is more plagioclase feldspar. Mafic: Derived from the words magnesium and ferric (Fe is the chemical symbol for iron) to describe an igneous rock having abundant dark-colored, magnesium- or iron-rich minerals such as biotite, pyroxene, or olivine. These are your grayish igneous rocks. It is considered archaic now, as the terms "acidic" and "basic rock" were based on an incorrect idea, dating from the 19th century, that silicic acid was the chief form of silicon occurring in rocks. As such, igneous rocks are described based on their silicate minerals. Rocks composed mostly of biotite, muscovite, sodium-rich plagioclase feldspars, potassium feldspars, and quartz make up the felsic family of igneous rocks. The composition of felsic igneous rocks is dominated by felsic minerals, primarily feldspar and quartz. This means that ultramafic is the type of rock having the least silica while felsic has the most silicate compound. Intrusive and Extrusive Igneous Rocks. The most common felsic rock is granite. Felsic igneous rocks, as a whole rock, tend to have light colors or shades: white, pink, light brown, light gray. For phaneritic felsic rocks, the QAPF diagram should be used, and a name given according to the granite nomenclature. Igneous rocks are formed by the cooling and crystallization of magma. For example, granite contains around 70% of silica. Common felsic minerals include quartz, muscovite, orthoclase, and the sodium-rich plagioclase feldspars. 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