In comparison with mafic rocks, felsic rocks are much lighter and as a result “float” higher in the lithosphere then mafic rocks. Felsic refers to silicate minerals, magma, and rocks which are enriched in the lighter elements such as silicon, oxygen, aluminium, sodium, and potassium.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. Felsic rocks, in general, form the bulk of the continental plates, while mafic basalt forms the seafloor. sticky, hence … The mafic magmas are somewhat more viscous than the ultramafic magmas, but they are still fairly fluid. On the opposite side of the rock spectrum are the iron and magnesium rich mafic and ultramafic minerals and rocks. The most common felsic rock is granite. Instead rhyolite tuff and ash falls are more common. Obsidian is an easily recognizable igneous rock. as coarse-grained plutonic rocks are porphyraceous. But unlike rhyolite, granite is rough textured and has obvious crystals. In the simplified classification, the intermediate (intermediate toned) aphanitic, crystalline igneous rock is andesite. Like rhyolite, granite is a felsic rock, and is composed almost entirely of feldspar and quartz. Rhyolite, extrusive igneous rock that is the volcanic equivalent of granite. Mafic. In geology, felsic is an adjective describing igneous rocks that are relatively rich in elements that form feldspar and quartz. Learn vocabulary, terms, and more with flashcards, games, and other study tools. The first pair is two rocks that formed from a felsic magma. 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%. Phenocrysts that make up porphyry should be felsic (quartz, feldspar). Most rhyolites are porphyritic, indicating that crystallization began prior to extrusion. Is Basalt felsic? They would have corresponding polished variants, as well as stairs, slabs, and walls, providing some new building materials. Additionally, they contain somewhat more gas than do the ultramafic magmas, but not nearly so much as the felsic magmas. [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. 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 Felsic rocks are light in color and are composed of feldspars and silicates. 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. Start studying Intrusive or Extrusive/Mafic or Felsic. Intermediate Magma. The basalt cooled rapidly, and the gabbro cooled slowly. Ultramafic. Felsic rocks are rich in silica, potassium, sodium, and aluminum and contain only small amounts of iron, magnesium, and calcium. Felsic rocks are made of light-colored, low-density minerals such as quartz and feldspar. Andesitic Intermediate between basalt and rhyolite. In column 2, indicate whether the rock is mafic, felsic, or intermediate. Felsic or Sialic Magma. This is why continental rocks are felsic and oceanic rocks are mafic. PART 1: Fill in the following table from the 6 common rocks we talked about in class: Intermediate. Granite and rhyolite are considered felsic, while basalt and gabbro are mafic (click here for more information on mafic and felsic). Felsic magma or lava is higher in viscosity than mafic magma/lava. Felsic, intermediate and mafic igneous rocks differ in their mineral composition. Light-colored Rhyolite Formation and Location of Mafic Rocks. Before cooling, felsic magmas have a very high viscosity. These are the terms you needed to know for the pre-lab quiz. Obsidian is a natural glass - it lacks crystals, and therefore lacks minerals. RHYOLITE. Felsic. 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. Terms to know prior to completing this lab: intrusive, extrusive, plutonic, volcanic, texture, composition, mafic, felsic, intermediate, aphanitic, phaneritic, vesicular, porphyritic, pegmatitic, glassy. Gabbro is the name given to intrusive mafic rocks, whereas basalt is the name given to extrusive mafic rocks. There is one important exception to the dark = mafic rule, and that is aphanitic, vesicle-free, black or very dark-gray glass that is called obsidian. Quizlet flashcards, activities and games help you improve your grades. Crystallization may sometimes have begun while the magma was deeply buried; in such cases, the rock may consist principally of well-developed, large, single crystals ( phenocrysts ) at the time of extrusion. In geology, felsic is an adjective describing igneous rocks that are relatively rich in elements that form feldspar and quartz. Typical felsic rocks are dacite and rhyolite. Types of Lava. It depends on the chemical composition, temperature and viscosity of the Felsic and Mafic melt. Basalt. 5.Either in describing rocks or lava, mafic means that the lava or rock has less silica while felsic implies that the lava or rock has the most silica. Intermediate rocks are composed of the minerals amphibole and feldspar and contain a combination of light and dark minerals. 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? ; Mafic rocks are dominated by plagioclase and pyroxene (even if you can't see them with the naked eye) and smaller amounts of olivine. Felsic magmas are the most viscous because of their high silica content. 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. Mafic and Felsic: Igneous rocks and the magma they come from can be classified as mafic and felsic based on their mineral content. Since the surface of the earth is covered by oceanic and continental crustal materials, granite and basalt are very common. Obsidian has a very high SiO 2 percent. Mafic and felsic can only be used to describe igneous 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. Fine Grain. Rhyolite is rarely found as lava. 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. These types of rocks are generally light colors as well. It is a glassy-textured, extrusive igneous rock. Types of Lava. The color of … "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. 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. Hence, rhyolite and basalt as fine-grained volcanic rocks are porphyritic and granite, syenite, etc. 1. determine texture: coarse-grained (visible crystals) = plutonic, fine-grained (microscopic crystals), or porphyritic (visible crystals in fine groundmass) = volcanic. * 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. The second pair is two rocks that formed from mafic magma. Mafic rocks are made of dark-colored, higher-density minerals such as olivine and pyroxene. The high silica content and lower temperatures of rhyolite magma result in high viscosities and violent eruptive styles. Andesite. Igneous rocks are classified according to their mineral content: Ultramafic rocks are dominated by olivine and/or pyroxene. The rhyolite cooled rapidly, and the granite cooled slowly. In certain cases where the granite forms very slowly, crystals can be up to several feet long. Igneous Rocks. Rhyolite is an extrusive felsic (silicic) volcanic rock. All igneous rocks are formed by crystals that form as the molten material cools. It is also rich in feldspar and silica.. Because of its high silica content, felsic magma is viscous, i.e. 6.Mafic rocks are darker in color than felsic rocks. 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. Igneous rocks are those that crystallize from magma, or liquid rock. Mafic Magma. Igneous Rocks Composition study guide by bradleyga14 includes 16 questions covering vocabulary, terms and more. Rhyolite. 4.Mafic lava creates basalt while felsic lava produces andesitic and rhyolite rocks. The mineral compositions of igneous rocks are usually described as being felsic, intermediate, mafic, or ultramafic (as examples, see Figure 4.7 and Figure 4.8). lighter and darker shades. So far so good, but what about the rhyolite and gabbro? RHYOLITE - aphanitic (small crystals) of felsic minerals with the same composition of granite. Rhyolite Felsic lava 800°-1000°C Lower temp and higher silica = more viscous. Mafic rocks are darker and are composed of magnesium and iron. 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