· At outcrops in the field metamorphic rocks often reveal extensive details about chemical reactions forming new minerals and of processes that change the rocks. An outcrop in the Tremola valley (Swiss Central Alps) may serve as an illustration for the visibility of metamorphism (Fig. 1.2 ).
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:Igneous RocksMetamorphic RockMetamorphic rock fall into two categories, foliated and unfoliated. Most foliated metamorphic rocks originate from regional metamorphism. Some unfoliated metamorphic rocks, such as hornfels, originate only by
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Metamorphic rocks form when heat and pressure transform an existing rock into a new rock. Contact metamorphism occurs when hot magma transforms the rock that it contacts. Regional metamorphism
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Each patch of color represents a range of temperature and pressure conditions where particular types of metamorphic rocks will form. Metamorphic facies are named for rocks that form under specific conditions (e.g., eclogite facies, amphibolite facies etc.), but those names don’t mean that the facies is limited to that one rock type.
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Metamorphic rocks form when heat and pressure transform an existing rock into a new rock. Contact metamorphism occurs when hot magma transforms rock that it contacts. Regional metamorphism
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:Igneous RocksMetamorphic RockEarth ScienceRocks and Stones9.1 Heat pressure and fluids are the agents of metamorphism. Metamorphic rocks form when heat, pressure, or chemically reactive fluids cause changes in preexisting rocks (Figure 9.1). The preexisting
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rock-forming mineral, any mineral that forms igneous, sedimentary, or metamorphic rocks and that typically, or solely, forms as an intimate part of rock-making processes. In contrast are those minerals that have a limited mode of occurrence or are formed by more unusual processes, such as the ores of metals, vein minerals, and cavity fillings.
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Metamorphic rocks are formed by the alteration of pre-existing rocks from exposure to heat and pressure while remaining in a solid form. Metamorphism occurs by breaking bonds between atoms in a mineral
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Rocks that form from regional metamorphism are likely to be foliated because of the strong directional pressure of converging plates. The Himalaya range is an example of where regional metamorphism is happening because two
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A metamorphic rock used to be some other type of rock, but it was changed inside the Earth to become a new type of rock. The word metamorphism comes from ancient Greek words for “change” (meta) and “form” (morph). The type of rock that a metamorphic rock used to be, prior to metamorphism, is called the protolith.
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· Metamorphic rocks are an important topic in geology.These are the rocks that form by the effects of heat, pressure, and shear upon igneous and sedimentary rocks. Some form during
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Figure 6.2.1 6.2. 1: Difference between pressure and stress and how they deform rocks. Pressure (or confining pressure) has equal stress (forces) in all directions and increases with depth under the Earth’s surface. Under directed stress, some stress directions (forces) are stronger than others, and this can deform rocks.
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Metamorphism occurs when solid rock changes in composition and/or texture without the mineral crystals melting, which is how igneous rock is generated. Metamorphic source rocks, the rocks that experience the
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Based on the rock formations, there are three basic classes which include igneous, sedimentary, and metamorphic. 1. Igneous Rocks. Igneous rocks form from the cooling of magma – molten materials in the earth’s crust. From the terminology itself, igneous means from fire or heat.
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· The word metamorphism is taken from the Greek for “change of form”; metamorphic rocks are derived from igneous or sedimentary rocks that have altered their form (recrystallized) as a result of changes in their physical environment.Metamorphism comprises changes both in mineralogy and in the fabric of the original rock..
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· The Three Types of Rocks. Rocks are classified based on how they were formed. The three major types are igneous, sedimentary, and metamorphic rocks. This classification is essential to geologists as it provides critical information about the history of specific regions on Earth. These rocks change forms via the rock cycle.
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· Sedimentary rocks are one of three main types of rocks, along with igneous and metamorphic. They are formed on or near the Earth’s surface from the compression of ocean sediments or other processes. Sedimentary rocks are formed on or near the Earth’s surface, in contrast to metamorphic and igneous rocks, which are
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9.5.4: Metamorphic Rocks. Metamorphic rocks are formed by the alteration of pre-existing rocks from exposure to heat and pressure while remaining in a solid form. Metamorphism occurs by breaking bonds between atoms in a mineral so that the atoms rearrange themselves into new, more stable, mineral forms. Rocks are transformed and
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· How metamorphic rocks form You can take any rock and make it metamorphic. All you need to do is subject it to enough pressure and temperature that it starts to fundamentally change. Image credits:
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Figure 10. Augen Gneiss. Gneiss is a high-grade, foliated metamorphic rock that consists of alternating bands of light- and dark-colored minerals (often quartz and biotite mica). The surface shown above consists of Precambrian-aged gneiss. The surrounding outcrop is gneiss with some shear zones and minor faults.
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Metamorphic rocks form because of changes in temperature and depth of burial within the Earth in a solid state without actual melting. Texture The first thing that identifies metamorphic rocks is their texture. They can be divided into: non-foliated (or massive) rocks. (or massive) rocks.
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These form by generally low temperature hydration of ultramafic rock (containing minerals composed chiefly of magnesium and iron), commonly at subduction zones. There are several different types of metamorphism, including dynamic, contact, regional, and retrogressive metamorphism, that form and shape rocks.
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Igneous rocks form when molten rock (magma or lava) cools and solidifies. Sedimentary rocks originate when particles settle out of water or air, or by precipitation of minerals from water. They accumulate in layers. Metamorphic rocks result when existing rocks are changed by heat, pressure, or reactive fluids, such as hot, mineral-laden water.
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This is usually related to the metamorphic temperatures of pelitic or aluminosilicate rocks and the minerals they form. The metamorphic grades of aureoles at shallow depth are albite-epidote hornfels, hornblende hornfels, pyroxene hornfels, and sillimanite hornfels, in increasing order of temperature of formation.
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Metamorphic rocks that form under low-pressure conditions or under the effects confining pressure—which is equal in all directions—do not become foliated. In most cases, this is because they are not buried deeply enough, and the heat for the metamorphism comes from a body of magma that has moved into the upper part of the crust.
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“”Metamorphic rocks arise from the transformation of existing rock types, in a process called metamorphism, which means “change in form””. The original rock (protolith) is subjected to heat (temperatures greater than 150 to 200 °C) and pressure (1500 bars), causing profound physical and/or chemical change.
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Metamorphic rocks (changed rocks) are made when existing rocks are subjected to high temperatures and high pressures for long periods of time. Metamorphism (meta = change, morph = form) happens when molten rock intrudes other rocks and bakes the contact zone where the molten rock touches the preexisting rock.
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The pressure that affects metamorphic rocks can be grouped into confining pressure and directed stress. Stress is a scientific term indicating a force. Strain is the result of this stress, including metamorphic changes within minerals. Figure 5.6.2 5.6. 2: An illustration of different types of pressure on rocks.
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· A metamorphic rock is a rock derived from a preexisting sedimentary or igneous rock, in which the minerals have changed due to changing P–T conditions. Recrystallization and neoformation of minerals are the prevailing processes which occur mainly as solid-state transformations. Download chapter PDF.
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Many schists are medium-grade rocks. 8.10 Garnet granulite, a high-grade metamorphic rock. High-grade metamorphic rocks, which form at temperatures greater than about 600 °C, are usually quite coarse-grained and contain minerals easily identified in hand specimen. Most form at high pressures.
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