Common mafic rocks include basalt, dolerite, and gabbro. For similar determinations, glasses can also be prepared in the laboratory from crystalline rocks. Chemical analyses of the most abundant components... Mafic and ultramafic rocks (those composed primarily of ferromagnesian—dark-coloured—minerals) 2.7 billion years old within the granite-greenstone terrane are the chief host of the epigenetic gold deposits of Western Australia. Mafic. Igneous rocks and minerals form from magma, molten rock that originates beneath Earth’s surface. 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. Mafic rock is commonly contrasted with felsic rock, in which light-coloured minerals predominate. Magma often collects in large magma chambers at depth in Earth, but magma is also mobile and can flow through fissures and sometimes reach the surface. Felsic. Updates? In geology, mafic is a term which describes an igneous rock or a silicate mineral rich in iron and magnesium. Premium Membership is now 50% off! Mafic rock, in geology, igneous rock that is dominated by the silicates pyroxene, amphibole, olivine, and mica. These minerals are high in magnesium and ferric oxides, and their presence gives mafic rock its characteristic dark colour. https://www.britannica.com/science/mafic-rock. The latter may be further divided into two groups: mafic,…, …or quartz, giving the term felsic; other felsic minerals are corundum, zircon, muscovite, lepidolite, and calcite. Most minerals fall within these two broad groups.…. Silica saturation is a classification of minerals and rocks as oversaturated, saturated, or undersaturated with respect to silica. Rocks containing lots of magnesium and ferrum. Let us know if you have suggestions to improve this article (requires login). Within this scheme, rocks are described as felsic, intermediate, mafic, and ultramafic (in order of decreasing silica content). Updates? Rocks containing lots of feldspar and silica. Of the oxides, silica (SiO 2) is usually the most abundant. Black Friday Sale! Mafic rocks derive from basalt protoliths and some volcanogenic sediments…, …the following groups: silicic or felsic (or acid, an old and discredited but unfortunately entrenched term), rocks having more than 66 percent silica; intermediate, rocks with 55 to 66 percent silica; and subsilicic, rocks containing less than 55 percent silica. Mafic rock, in geology, igneous rock that is dominated by the silicates pyroxene, amphibole, olivine, and mica. By signing up for this email, you are agreeing to news, offers, and information from Encyclopaedia Britannica. Premium Membership is now 50% off! Mid-ocean ridges and subduction zones contain most magmas at or near Earth’s surface. The fine-grained or glassy nature of many volcanic rocks makes a chemical classification such as the felsic-mafic taxonomy very useful in distinguishing the different types. Mafic: Felsic: Definition: It is relating to, denoting, or containing a group of dark-colored, mainly ferromagnetic minerals such as pyroxene and olivine. This broad grouping on the basis of mineralogy related to silica content is used in many modern classification schemes. basement rock The thick foundation of ancient, and oldest metamorphic and igneous rock that forms the crust of continents, often in the form of granite. Mafic is a chemical classification for igneous rocks containing 46-85% mafic (minerals rich in iron and magnesium) minerals. Our editors will review what you’ve submitted and determine whether to revise the article. Felsic rocks can be produced by metamorphism of both igneous and sedimentary protoliths (e.g., granite and arkose, respectively) and are rich in silicon, sodium (Na), potassium, calcium, aluminum, and lesser amounts of iron and magnesium. Corrections? Be on the lookout for your Britannica newsletter to get trusted stories delivered right to your inbox.
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