Metamorphic processes [ edit]
- Recrystallization [ edit] Basalt hand sample showing fine texture Amphibolite formed by metamorphism of basalt showing coarse texture ...
- Phase change [ edit] Kyanite Andalusite ...
- Plastic deformation [ edit] In plastic deformation pressure is applied to the protolith, which causes it to shear or bend, but not break. ...
Which process changes metamorphic rock into sedimentary rock?
How Do Metamorphic Rocks Change Into Sedimentary Rocks?? Explanation: Weathering is the process of breakdown of rocks through the action of wind, air, water and by the action of organisms. The metamorphic rocks get gradually converted into sedimentary rocks through this process. The big rocks change into small rock particles called sediments.
What is the process by which metamorphic rock is formed?
“”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.
What is the process of metamorphism?
Metamorphism is the process by which rocks are changed in composition, texture, or structure by extreme heat and pressure. The change occurs primarily due to heat, pressure, and the introduction of chemically active fluids.
What are the processes that metamorphose a rock?
Metamorphism: A Process of Change 1 Metamorphic rock forms from a pre-existing rock or protolith. During metamorphism, new minerals grow at the expense of old minerals, and/or the shape, size, and arrangement of grains in the rock may change. Changes occur in the solid state because melting doesn t occur.
What is metamorphic rock?
What are the factors that cause metamorphic changes?
How does contact metamorphism differ from dynamic metamorphism?
What are the three main types of metamorphism?
How can minerals be identified?
What is the rock cycle?
What is the importance of gem deposits?
See 4 more
About this website
Metamorphism of Rocks Process & Impact - Study.com
Metamorphic Processes: How Metamorphic Rocks Form. To learn what is metamorphism, recall that in metasomatism rocks change into another form rocks under high temperature and pressure.
Geology 3015 Lecture Notes - Lakehead University
Geology 3015 Lecture Notes - Lakehead University
What is the process of metamorphism?
6.2: Metamorphic Processes. 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 metamorphism, are called the parent rock or protolith, from proto – meaning first, and lithos- meaning rock.
How does metamorphism occur?
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 metamorphism, are called the parent rock or protolith, from proto – meaning first, and lithos- meaning rock. Most metamorphic processes take place deep underground, inside the earth’s crust. During metamorphism, protolith chemistry is mildly changed by increased temperature (heat), a type of pressure called confining pressure, and/or chemically reactive fluids. Rock texture is changed by heat, confining pressure, and a type of pressure called directed stress.
What are the three metamorphic agents?
These reactive fluids are made of mostly water (H 2 O) and carbon dioxide (CO 2 ), and smaller amounts of potassium (K), sodium (Na), iron (Fe), magnesium (Mg), calcium (Ca), and aluminum (Al). These fluids react with minerals in the protolith, changing its chemical equilibrium and mineral composition, in a process similar to the reactions driven by heat and pressure. In addition to using elements found in the protolith, the chemical reaction may incorporate substances contributed by the fluids to create new minerals. In general, this style of metamorphism, in which fluids play an important role, is called hydrothermal metamorphism or hydrothermal alteration. Water actively participates in chemical reactions and allows extra mobility of the components in hydrothermal alteration.
How does pressure affect metamorphic rocks?
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.
What is the term for the process of hydrothermal alteration?
In general, this style of metamorphism, in which fluids play an important role, is called hydrothermal metamorphism or hydrothermal alteration. Water actively participates in chemical reactions and allows extra mobility of the components in hydrothermal alteration.
What temperature does metamorphism occur?
Heat-driven metamorphism begins at temperatures as cold as 200˚C and can continue to occur at temperatures as high as 700°C-1,100°C [ 3; 4; 5 ].
How do fluids react with minerals?
These fluids react with minerals in the protolith, changing its chemical equilibrium and mineral composition, in a process similar to the reactions driven by heat and pressure. In addition to using elements found in the protolith, the chemical reaction may incorporate substances contributed by the fluids to create new minerals.
How is metamorphic rock formed?
Metamorphic rock, estimated to be as old as 3.8 billion years, located near Isua at Qorqut Sound, Greenland. rock formed by the cooling of magma or lava. molten rock, or magma, that erupts from volcanoes or fissures in the Earth's surface. molten, or partially melted, rock beneath the Earth's surface.
What are the conditions required to form a metamorphic rock?
The conditions required to form a metamorphic rock are very specific. The existing rock must be exposed to high heat, high pressure, or to a hot, mineral-rich fluid. Usually, all three of these circumstances are met.
How did igneous and sedimentary rocks form?
Igneous rocks formed when liquid magma or lava —magma that has emerged onto the surface of the Earth —cooled and hardened.
Why do metamorphic rocks break down?
This happens due to geologic uplift and the erosion of the rock and soil above them. At the surface, metamorphic rocks will be exposed to weathering processes and may break down into sediment. These sediments could then be compressed to form sedimentary rocks, which would start the entire cycle anew.
What is the relationship between the three rock types?
Noun. movement and interaction of the Earth's plates. rock cycle. Noun. processes that explain the relationship between the three rock types: igneous, sedimentary, and metamorphic. Any rock type can become any other. sedimentary rock. Noun. rock formed from fragments of other rocks or the remains of plants or animals.
Why does limestone turn into marble?
Limestone, a sedimentary rock, will change into the metamorphic rock marble if the right conditions are met. Although metamorphic rocks typically form deep in the planet’s crust, they are often exposed on the surface of the Earth. This happens due to geologic uplift and the erosion of the rock and soil above them.
What is the name of the rock that forms when granite is subjected to intense heat and pressure?
When granite is subjected to intense heat and pressure, it changes into a metamorphic rock called gneiss. Slate is another common metamorphic rock that forms from shale. Limestone, a sedimentary rock, will change into the metamorphic rock marble if the right conditions are met.
How does metamorphism occur?
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 metamorphism, are called the parent rock or protolith, from proto – meaning first, and lithos- meaning rock. Most metamorphic processes take place deep underground, inside the earth’s crust. During metamorphism, protolith chemistry is mildly changed by increased temperature (heat), a type of pressure called confining pressure, and/or chemically reactive fluids. Rock texture is changed by heat, confining pressure, and a type of pressure called directed stress.
What temperature does metamorphic rock start at?
Heat-driven metamorphism begins at temperatures as cold as 200˚C and can continue to occur at temperatures as high as 700°C-1,100°C [ 3; 4; 5 ]. Higher temperatures would create magma, and thus, would no longer be a metamorphic process. Temperature increases with increasing depth in the Earth along a geothermal gradient (see Chapter 4) and metamorphic rock records these depth-related temperature changes.
What are the minerals that are produced by fluids-activated metamorphism?
For example, the mining districts in the Cottonwood Canyons and Mineral Basin of northern Utah produce valuable ores such as argentite (silver sulfide), galena (lead sulfide), and chalcopyrite (copper-iron sulfide), as well as the native element gold [ 2 ] . These mineral deposits were created from the interaction between a granitic intrusion called the Little Cottonwood Stock and country-rock consisting of mostly limestone and dolostone. Hot, circulating fluids expelled by the crystallizing granite reacted with and dissolved the surrounding limestone and dolostone, precipitating out new minerals created by the chemical reaction. Hydrothermal alteration of mafic mantle rock, such as olivine and basalt, creates the metamorphic rock serpentinite, a member of the serpentine subgroup of minerals. This metamorphic process happens at mid-ocean spreading centers where newly formed oceanic crust interacts with seawater.
What are the three metamorphic agents?
These reactive fluids are made of mostly water (H 2 O) and carbon dioxide (CO 2 ), and smaller amounts of potassium (K), sodium (Na), iron (Fe), magnesium (Mg), calcium (Ca), and aluminum (Al). These fluids react with minerals in the protolith, changing its chemical equilibrium and mineral composition, in a process similar to the reactions driven by heat and pressure. In addition to using elements found in the protolith, the chemical reaction may incorporate substances contributed by the fluids to create new minerals. In general, this style of metamorphism, in which fluids play an important role, is called hydrothermal metamorphism or hydrothermal alteration. Water actively participates in chemical reactions and allows extra mobility of the components in hydrothermal alteration.
How does hydrothermal alterations occur?
This happens when seawater circulates down through fractures in the fresh, still-hot basalt, reacting with and removing mineral ions from it. The dissolved minerals are usually ions that do not fit snugly in the silicate crystal structure, such as copper. The mineral-laden water emerges from the seafloor via hydrothermal vents called black smokers, named after the dark-colored precipitates produced when the hot vent water meets cold seawater. (see Chapter 4, Igneous Rock and Volcanic Processes) Ancient black smokers were an important source of copper ore for the inhabitants of Cyprus (Cypriots) as early as 4,000 BCE, and later by the Romans [ 8 ].
How many bars of pressure is a metamorphic rock?
For metamorphic rocks, pressures range from a relatively low-pressure of 3,000 bars [ 5] around 50,000 bars [ 5 ], which occurs around 15-35 kilometers below the surface.
What is the pressure exerted on rocks?
Pressure exerted on rocks under the surface is due to the simple fact that rocks lie on top of one another. When pressure is exerted from rocks above, it is balanced from below and sides and is called confining or lithostatic pressure. Confining pressure has equal pressure on all sides (see figure) and is responsible for causing chemical reactions to occur, just like heat. These chemical reactions will cause new minerals to form.
What is the process of forming metamorphic rocks?
The most common process in the formation of metamorphic rocks is recrystallization. In this process, small crystals of one mineral in contact with one another slowly come together to form fewer larger crystals. For example, the sedimentary rock, limestone. Limestone is composed of microscopic crystals of calcite that once formed the shells of marine creatures. When metamorphosed, those tiny crystals are slowly forced together under high pressure and begin to form larger, more visible crystals of calcite found in the metamorphic rock marble.
Where does metamorphism occur?
Contact metamorphism occurs relatively locally, in areas adjacent to igneous intrusions or in areas that are in contact with hot water known as hydrothermal fluids .
How long does metamorphism last?
Typically this kind of metamorphism is caused by moderate pressure and extreme heat that may last for a period of days to thousands of years. In cases of contact metamorphism, the most extreme metamorphism occurs at the contact point between the parent rock and the intrusive magma or hydrothermal fluid. The degree of metamorphism then decreases rapidly as distance from the heat source increases. Depending on the source, zones of contact metamorphism may range from a few millimeters to tens of meters.
What is the process of metasomatism?
The process of metasomatism results in the loss or addition of chemicals. This can best be seen in the production of anthracite coal, which is almost pure carbon. The parent rock bituminous coal is produced from the aggregation of dead plant material, and anthracite is produced by the loss of the more volatile materials such as nitrogen, oxygen, and methane.
How slow does metamorphism take place?
Most metamorphic reactions take place at very slow rates. For example, the growth of new minerals within a rock during metamorphism has been estimated to be about 1 millimetre per million years. For this reason, it is very difficult to study metamorphic processes in a lab.
Why is pressure important in metamorphic processes?
1 ). Second, it has implications for the texture of metamorphic rocks. Rocks that are subjected to very high confining pressures are typically denser than others because the mineral grains are squeezed together (Figure 7.1. 2 a), and also because they may contain minerals that have greater density because the atoms are more closely packed.
What is the parent rock of a rock?
The parent rock is the rock that exists before metamorphism starts. Sedimentary or igneous rocks can be considered the parent rocks for metamorphic rocks. Although an existing metamorphic rock can be further metamorphosed or re-metamorphosed, metamorphic rock doesn’t normally qualify as a “parent rock”. For example, if a mudstone is metamorphosed to slate and then buried deeper where it is metamorphosed to schist, the parent rock of the schist is mudstone, not slate. The critical feature of the parent rock is its mineral composition because it is the stability of minerals that counts when metamorphism takes place. In other words, when a rock is subjected to increased temperatures, certain minerals may become unstable and start to recrystallize into new minerals.
What minerals are polymorphs?
The minerals kyanite, andalusite, and sillimanite are polymorphs with the composition Al 2 SiO 5. They are stable at different pressures and temperatures, and, as we will see later, they are important indicators of the pressures and temperatures that existed during the formation of metamorphic rocks (Figure 7.1. 1 ).
Is metamorphism slow or fast?
While the rate of metamorphism is slow, the tectonic processes that lead to metamorphism are also very slow, so in most cases, the chance for metamorphic reactions to be completed is high. For example, one important metamorphic setting is many kilometers deep within the roots of mountain ranges. A mountain range takes tens of millions of years to form, and tens of millions of years more to be eroded to the extent that we can see the rocks that were metamorphosed deep beneath it.
What are the main factors that control metamorphic processes?
7.1 Controls over Metamorphic Processes. The main factors that control metamorphic processes are: The mineral composition of the parent rock. The temperature at which metamorphism takes place. The amount and type of pressure during metamorphism. The types of fluids (mostly water) that are present during metamorphism.
How slow does metamorphism take place?
Most metamorphic reactions take place at very slow rates. For example, the growth of new minerals within a rock during metamorphism has been estimated to be about 1 mm per million years. For this reason, it is very difficult to study metamorphic processes in a lab.
Why is pressure important in metamorphic processes?
Pressure is important in metamorphic processes for two main reasons. First, it has implications for mineral stability (Figure 7.3). Second, it has implications for the texture of metamorphic rock s. Rocks that are subjected to very high confining pressures are typically denser than others because the mineral grains are squeezed together (Figure 7.4a), and because they may contain mineral polymorphs in which the atoms are more closely packed. Because of plate tectonics, pressures within the crust are typically not applied equally in all directions. In areas of plate convergence, the pressure in one direction (perpendicular to the direction of convergence) is typically greater than in the other directions (Figure 7.4b). In situations where different blocks of the crust are being pushed in different directions, the rocks will be subjected to sheer stress (Figure 7.4c).
What is the key variable in controlling the type of metamorphism that takes place?
The temperature that the rock is subjected to is a key variable in controlling the type of metamorphism that takes place. As we learned in the context of igneous rocks, mineral stability is a function of temperature, pressure, and the presence of fluids (especially water). All minerals are stable over a specific range of temperatures.
How long does it take for a mountain range to metamorphose?
For example, one important metamorphic setting is many kilometres deep within the roots of mountain ranges. A mountain range takes tens of millions of years to form, and tens of millions of years more to be eroded to the extent that we can see the rocks that were metamorphosed deep beneath it. Exercises.
What is metamorphic rock?
Metamorphic rocks are pre-existing rocks whose mineral composition and/or texture has been changed by processes within the Earth. Discover more. You have reached the end of the main content. Go back to start of main content.
What are the factors that cause metamorphic changes?
The important factors that produce metamorphic changes are. pressure deep within the crust. temperature. strain (shape and volume changes as a result of stress during deformation) fluid activity (pressure due to fluids in pore spaces within the original rocks) Toggle Caption.
How does contact metamorphism differ from dynamic metamorphism?
Contact metamorphism occurs as zones a few hundred metres wide around large igneous intrusions while dynamic metamorphism is restricted to fault and thrust zones only a few tens of metres thick. All three types of metamorphism can overlap.
What are the three main types of metamorphism?
The three main types of metamorphism are: Contact (also known as thermal) metamorphism: this is produced by high temperature, low pressure, low strain and variable fluid pressure.
How can minerals be identified?
Minerals can be identified by the shape of their crystals: called crystallography. External crystallography measures the outside properties of crystals such as length of crystal surfaces and the angles between these surfaces.
What is the rock cycle?
The rock cycle is a collection of processes which shape the surface of the Earth. Rocks are constantly recycled by burial, melting, uplift and erosion. During metamorphic processes, few components (e.g. fluorine, boron), other than water, enter or leave rocks. No overall chemical changes occur; instead, the original chemical constituents are just ...
What is the importance of gem deposits?
Since the 1950s, several discoveries have led to a new understanding of how the Earth works. Gem deposits are a very important group of mineral deposits, forming in a variety of geological environments and occurring in rocks of all ages from thousands of millions to recent times.
