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Sill (geology)

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	Topics Sill (geology) Topic Home In geologyGeology Summary Geology anetary geology]] refers to the application of geologic principles to other bodies of the solar system.... , a sill is a tabular plutonPluton A pluton in geology is an intrusive igneous rock body which crystallized from a magma below the surface of the Earth.... that has intruded between older layersStratum In geology and related fields, a stratum is a layer of rock or soil with internally consistent characteristics that distingu... of sedimentary rockSedimentary rock Sedimentary rock is one of the three main rock groups and is formed in three main ways—by the deposition of the weath... , beds of volcanic lavaLava Lava is molten rock expelled by a volcano during an eruption.... or tuffTuff Tuff is a type of rock consisting of consolidated volcanic ash ejected from vents during a volcanic eruption. ... , or even along the direction of foliationFoliation (geology) Foliation is any penetrative planar fabric present in rocks.... in metamorphic rockMetamorphic rock Metamorphic rock is the result of the transformation of a pre-existing rock type, the protolith, in a process called met... . The term sill is synonymous with concordant intrusive sheet. This means that the sill does not cut across preexisting rocks, in contrast to dikesDike (geology) Overview A dike or dyke in geology refers to a tabular intrusive igneous body.... , which do cut across older rocks. Sills are always parallel to beds (layers) of the surrounding country rock. Usually they are in a horizontal orientation, although tectonic processes can cause rotation of sills into near vertical orientations. They can be confused with solidified lava flows; however there are several differences between them. Intruded sills will show partial melting of and incorporation of the surrounding country rockFacts About Country rock (geology) Country rock is a geological term meaning the rock native to an area.... . On both the "upper" and "lower" contact surfaces of the country rock into which the sill has intruded, evidence of heating will be observed (contact metamorphism)Metamorphism Metamorphism can be defined as the solid state recrystallisation of pre-existing rocks due to changes in heat and/or pressur... . Lava flows will show this evidence only on the lower side of the flow. In addition, lava flows will typically show evidence of vesiclesVesicular texture Vesicular texture is a volcanic rock texture characterised by, or containing, many vesicles.... (bubbles) where gases escaped into the atmosphereAtmosphere Atmosphere is the general name for a layer of gases that may surround a material body of sufficient mass.... . Because sills generally form at depth (up to many kilometers), the pressure of overlying rock prevents this from happening much, if at all. Lava flows will also typically show evidence of weatheringWeathering Weathering is the process of disintegration of rocks, soils and their minerals through direct, or indirect contact with the ... on their upper surface, whereas sills, if still covered by country rock, typically do not. Certain ultramafic to mafic layered intrusionsUltramafic to mafic layered intrusions Ultramafic to mafic layered intrusions are found in typically ancient cratons and are rare but worldwide in distribution.... are a variety of sill that often contain important oreOre An ore is a volume of rock containing components or minerals in a mode of occurrence which renders it valuable for mining.... deposits. PrecambrianPrecambrian The Precambrian is an informal name for the eons of the geologic timescale that came before the current Phanerozoic eon... examples include the BushveldBushveld igneous complex The Bushveld Igneous Complex contains some of the richest ore deposits on Earth.... , Insizwa, and the Great DykeGreat Dyke Overview The Great Dyke is a linear feature that trends nearly north-south through the center of Zimbabwe passing just to the west of... complexes of southern AfricaAfrica Africa is one of the greatest sized continents of the Earth.... , the Duluth intrusive complexDuluth Complex Overview The Duluth Complex, the related Beaver Bay Complex , and the associated North Shore Volcanic Group are rock form... of the Superior District, and the Stillwater igneous complexStillwater igneous complex The Stillwater igneous complex is a large ultramafic to mafic layered intrusion located in southern Montana in Stillwater, S... of the United StatesUnited States The United States of America, also known as the United States, the U.S., the U.S.A., and America, is... . PhanerozoicPhanerozoic The Phanerozoic Eon is the period of geologic time during which abundant animal life has existed.... examples are usually smaller and include the RùmRum Rum is a distilled beverage made from sugarcane by-products such as molasses and sugarcane juice by a process of fermentatio... peridotitePeridotite Peridotite is a dense, coarse-grained rock, consisting mostly of the minerals olivine and pyroxene.... complex of ScotlandScotland Scotland is a nation in northwest Europe and one of the constituent countries of the United Kingdom.... and the Skaergaard igneous complexSkaergaard intrusion The Skaergaard intrusion is a layered gabbro complex in East Greenland, located at .... of east GreenlandGreenland Greenland is a self-governed Danish territory.... . These intrusionIntrusion In geology, an intrusion is a body of igneous rock that has crystallized from a molten magma below the surface of the Earth.... s often contain concentrations of goldGold Gold is a highly sought-after precious metal that for many centuries has been used as money, a store of value and in jewelry... , platinumPlatinum Platinum is a chemical element in the periodic table that has the symbol Pt and atomic number 78.... , chromiumChromium Chromium is a chemical element in the periodic table that has the symbol Cr and atomic number 24. ... , and other rare elements. See also BatholithBatholith A batholith is a large emplacement of igneous intrusive rock that forms from cooled magma deep in the Earth's crust.... DikeDike (geology) A dike or dyke in geology refers to a tabular intrusive igneous body.... LaccolithLaccolith A laccolith is an igneous intrusion that has been injected between two layers of sedimentary rock....