Ultramafic. Most rhyolites are porphyritic, indicating that crystallization began prior to extrusion. All igneous rocks are formed by crystals that form as the molten material cools. The basalt cooled rapidly, and the gabbro cooled slowly. It is also rich in feldspar and silica.. Because of its high silica content, felsic magma is viscous, i.e. Intermediate Magma. 6.Mafic rocks are darker in color than felsic rocks. Felsic Magma (Rhyolitic). Start studying Intrusive or Extrusive/Mafic or Felsic. * Felsic Classification of Igneous Rocks Intermediate Mafic Obsidian Basaltic glass Extrusive Ultramafic Texture Glassy (non-crystalline) Fine-grained Rhyolite Andesite Basalt Granite Diorite Gabbro Perl. Mafic rocks are darker and are composed of magnesium and iron. Texture: aphanitic The term acid rock, although sometimes used as a synonym, in current usage refers to a high silica content (greater than 63% SiO 2 by weight) volcanic rock such as rhyolite. Felsic rocks are made of light-colored, low-density minerals such as quartz and feldspar. Types of Lava. Mafic Magma. Rhyolite Felsic lava 800°-1000°C Lower temp and higher silica = more viscous. Types of Basalt Mafic Magma Flood Pahoehoe Aa Pillow. In their study, mafic group B inclusions and, to a lesser extent, group A are stated to be compatible with mafic components of andesite–dacite–rhyolite (ADR) arc-type suites (Whalen et al., 2002, p. 1560) with the stated implications about their petrogenesis under conditions of low pressure, dry melting, and fluxing by hydrous fluids derived from subducted lithosphere. ; Mafic rocks are dominated by plagioclase and pyroxene (even if you can't see them with the naked eye) and smaller amounts of olivine. 2. determine color/composition: mostly light minerals = felsic; half light, half black (or gray in fine grained rocks) = intermediate; mostly black minerals = mafic; mostly olivine = ultramafic The high silica content and lower temperatures of rhyolite magma result in high viscosities and violent eruptive styles. Mafic rocks are made of dark-colored, higher-density minerals such as olivine and pyroxene. RHYOLITE. So far so good, but what about the rhyolite and gabbro? Like rhyolite, granite is a felsic rock, and is composed almost entirely of feldspar and quartz. Igneous Rocks. Felsic rocks are rich in silica, potassium, sodium, and aluminum and contain only small amounts of iron, magnesium, and calcium. In geology, felsic is an adjective describing igneous rocks that are relatively rich in elements that form feldspar and quartz. It is a glassy-textured, extrusive igneous rock. Since the surface of the earth is covered by oceanic and continental crustal materials, granite and basalt are very common. Granite and rhyolite are considered felsic, while basalt and gabbro are mafic (click here for more information on mafic and felsic). ANDESITIC ROCKS or Intermediate Rocks ANDESITE is a medium gray, fine-grained rock of volcanic origin, named after the Andes Mountains, but is abundant in all volcanic regions associated with subduction zones (where crust is sinking and partially remelting - example: volcanos associated with … Felsic, intermediate and mafic igneous rocks differ in their mineral composition. Rhyolite is an extrusive felsic (silicic) volcanic rock. Rhyolite is an extrusive igneous rock, formed from magma rich in silica that is extruded from a vent to cool quickly on the surface rather than slowly in the subsurface. In the simplified classification, the intermediate (intermediate toned) aphanitic, crystalline igneous rock is andesite. True or False: Rhyolite and Granite can both have the same mineral composition despite having two different appearances. Light-colored Rhyolite Formation and Location of Mafic Rocks. Mafic. Terms to know prior to completing this lab: intrusive, extrusive, plutonic, volcanic, texture, composition, mafic, felsic, intermediate, aphanitic, phaneritic, vesicular, porphyritic, pegmatitic, glassy. [1] It is contrasted with mafic rocks, which are relatively richer in magnesium and iron.Felsic refers to silicate minerals, magma, and rocks which are enriched in the lighter elements such as silicon, oxygen, aluminium, sodium, and potassium. Before cooling, felsic magmas have a very high viscosity. Felsic rocks are usually light in color and have specific gravities less than 3. This is why continental rocks are felsic and oceanic rocks are mafic. In certain cases where the granite forms very slowly, crystals can be up to several feet long. In comparison with mafic rocks, felsic rocks are much lighter and as a result “float” higher in the lithosphere then mafic rocks. Felsic minerals tend to be white, pink and clear (transparent) in color, and hence these rocks will be a lighter overall color, while mafic minerals tend to be dark black, dark red, or dark green colors, and these mafic rocks will be a darker color, often black. Felsic rocks are light in color and are composed of feldspars and silicates. Andesitic Intermediate between basalt and rhyolite. These types of rocks are generally light colors as well. Is Basalt felsic? Mineralogic contents – felsic versus mafic. Additionally, they contain somewhat more gas than do the ultramafic magmas, but not nearly so much as the felsic magmas. The rhyolite cooled rapidly, and the granite cooled slowly. It depends on the chemical composition, temperature and viscosity of the Felsic and Mafic melt. They would have corresponding polished variants, as well as stairs, slabs, and walls, providing some new building materials. Types of Lava. If this were a list based on types of magma based on silica content, then felsic magma would sit at the top with 65% and 70%. Mafic and felsic can only be used to describe igneous rocks. Typical felsic rocks are dacite and rhyolite. In geology, felsic is an adjective describing igneous rocks that are relatively rich in elements that form feldspar and quartz. RHYOLITE - aphanitic (small crystals) of felsic minerals with the same composition of granite. But unlike rhyolite, granite is rough textured and has obvious crystals. It is contrasted with mafic rocks, which are relatively richer in magnesium and iron.Felsic refers to silicate minerals, magma, and rocks which are enriched in the lighter elements such as silicon, oxygen, aluminium, sodium, and potassium. Instead rhyolite tuff and ash falls are more common. Andesite. Gabbro is the name given to intrusive mafic rocks, whereas basalt is the name given to extrusive mafic rocks. Well, as you can see, mankind is very good when a need arises to make simple concepts difficult to understand. Rhyolite is rarely found as lava. PART 1: Fill in the following table from the 6 common rocks we talked about in class: These are the terms you needed to know for the pre-lab quiz. felsic rock, highest content of silicon, with predominance of quartz, alkali feldspar and/or feldspathoids: the felsic minerals; these rocks (e.G., granite, rhyolite) are usually light coloured, and feature low density. On the opposite side of the rock spectrum are the iron and magnesium rich mafic and ultramafic minerals and rocks. "Mafic" is a term that describes igneous rocks or silicate material characterized by a rich content of iron and magnesium while felsic rocks are igneous rocks that are rich in light elements such as oxygen, aluminum, silicon, potassium, and sodium. The color of … Rhyolite, andesite, and basalt form a series that varies in composition, from felsic to mafic because of an increasing fraction of iron+magnesium rich minerals that darkens the tone. Why not complete the set of stone variants with rhyolite, which is extrusive felsic, gabbro, which is intrusive mafic, and basalt, which is extrusive mafic? Hence, rhyolite and basalt as fine-grained volcanic rocks are porphyritic and granite, syenite, etc. Basalt. In column 2, indicate whether the rock is mafic, felsic, or intermediate. Learn vocabulary, terms, and more with flashcards, games, and other study tools. Obsidian is an easily recognizable igneous rock. as coarse-grained plutonic rocks are porphyraceous. Mafic and Felsic: Igneous rocks and the magma they come from can be classified as mafic and felsic based on their mineral content. Quizlet flashcards, activities and games help you improve your grades. Rhyolite, extrusive igneous rock that is the volcanic equivalent of granite. 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