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Why are metamorphic rocksformed by contact metamorphism usually not as dense as those formed by regional metamorphism?
Because contact metamorphism usually occurs because of an increase in temperature. In contrary, regional metamorphism is usually the result of compression. Compression makes a rock more dense.
Why are metamorphic rocks formed by contact metamorphism usually not dense or resistant?
Metamorphic rocks formed by contact metamorphism are usually not dense or resistant because they are formed at relatively low pressures and temperatures compared to regional metamorphism. The short duration of the heating process in contact metamorphism does not allow for the recrystallization and reorganization of mineral structures that contribute to denser and more resistant rocks. Additionally, the presence of fluids and gases in contact metamorphism can facilitate alteration and weakening of the original rock material.
Why are metamorphic rocks formed by contact metamorphism usually not as dense as those formed by reg?
Because in contact the rock actually comes in contact with magma, this joins with the rock, so when it cools and become igneous rock, it's denser. In regular, or regional, the rock is formed from intense heat and pressure, but does not actually come in contact with magma.
What causes contact metamorphism?
Contact metamorphism is caused by the heat and chemical activity of nearby magma or lava intruding into the surrounding rock. This results in the alteration of the rock through recrystallization without melting, leading to the formation of new minerals and textures. The temperature and pressure conditions of contact metamorphism are usually lower than those of regional metamorphism.
which rock is only formed by regional metamorphasim?
The heat generated by the magma chamber has changed these sedimentary rocks into the metamorphic rocks marble, quartzite, and hornfels. Regional Metamorphism occurs over a much larger area. This metamorphism produces rocks such as gneiss and schist.
Why are metamorphic rocksformed by contact metamorphism usually not as dense as those formed by regional metamorphism?
Because contact metamorphism usually occurs because of an increase in temperature. In contrary, regional metamorphism is usually the result of compression. Compression makes a rock more dense.
Why are metamorphic rocks formed by contact metamorphism usually not dense or resistant?
Metamorphic rocks formed by contact metamorphism are usually not dense or resistant because they are formed at relatively low pressures and temperatures compared to regional metamorphism. The short duration of the heating process in contact metamorphism does not allow for the recrystallization and reorganization of mineral structures that contribute to denser and more resistant rocks. Additionally, the presence of fluids and gases in contact metamorphism can facilitate alteration and weakening of the original rock material.
Why are metamorphic rocks formed by contact metamorphism usually not as dense as those formed by reg?
Because in contact the rock actually comes in contact with magma, this joins with the rock, so when it cools and become igneous rock, it's denser. In regular, or regional, the rock is formed from intense heat and pressure, but does not actually come in contact with magma.
What are two ways that can poduce metamorphic rocks?
Two ways in which metamorphic rocks are 1) contact metamorphism (thermal) where magma comes in direct contact with surrounding igneous rock and changes it due to high temperatures and usually low pressure. 2) Regional metamorphism (dynamothermal) ,high pressures and low temperature eg mountain ranges. or 3) Cataclastic metamorphism, heat as a result of friction due to two plate meeting or passing each other.
Where does contact (prograde) occur?
Contact metamorphism occurs typically around intrusive igneous rocks as a result of the temperature increase caused by the intrusion of magma into cooler country rock. The area surrounding the intrusion where the contact metamorphism effects are present is called the metamorphic aureole. Contact metamorphic rocks are usually known ashornfels. Rocks formed by contact metamorphism may not present signs of strong deformation and are often fine-grained.
What causes contact metamorphism?
Contact metamorphism is caused by the heat and chemical activity of nearby magma or lava intruding into the surrounding rock. This results in the alteration of the rock through recrystallization without melting, leading to the formation of new minerals and textures. The temperature and pressure conditions of contact metamorphism are usually lower than those of regional metamorphism.
What is the most common type of metamorphism?
The most common type of metamorphism is regional metamorphism, which occurs over large areas typically associated with tectonic plate boundaries. This type of metamorphism involves high pressure and temperature conditions, leading to the formation of minerals like mica, quartz, and feldspar in rocks.
What is an example of a metamorphic rock?
One of the most popular metamorphic rocks is marble. Originally limestone, marble is generally created through regional metamorphism, which is when pressure and heat from where magma is pushing up through the Earth's crust effect rocks which are close by, but not actually touching the magma. Contact metamorphism changes the rocks that do actually touch the magma, this is how shale is usually metamorphosed into gneiss.
which rock is only formed by regional metamorphasim?
The heat generated by the magma chamber has changed these sedimentary rocks into the metamorphic rocks marble, quartzite, and hornfels. Regional Metamorphism occurs over a much larger area. This metamorphism produces rocks such as gneiss and schist.
What is the metamorphic grade of gneiss?
Gneiss is typically associated with high-grade metamorphism, which means that it has undergone intense heat and pressure to form distinct banding of minerals. This places gneiss in the high-pressure and high-temperature conditions of the regional metamorphic grade.
How does an igneous rock change to metamorphic?
Meta-igneous. Metamorphism of igneous rocks can form a wide range of metamorphic rocks, depending on the mineralogy of the igneous protolith and the P-T conditions of the metamorphism.
What rocks are Metamorphic rock?
== == Rocks that have undergone a change in mineral structure or composition, without melting, through heat and/or pressure are metamorphic rocks. Examples are slate, anthracite, and gneiss.How does contact (prograde) occur? the changes in mineral assemblage and mineral composition that occur during burial and heating are referred to as prograde metamorphism.Where does contact (prograde) occur? Contact metamorphism occurs typically around intrusive igneous rocks as a result of the temperature increase caused by the intrusion of magma into cooler country rock. The area surrounding the intrusion where the contact metamorphism effects are present is called the metamorphic aureole. Contact metamorphic rocks are usually known ashornfels. Rocks formed by contact metamorphism may not present signs of strong deformation and are often fine-grained.Why does contact (prograde) occur? Contact metamorphism occurs typically around intrusive igneous rocks as a result of the temperature increase caused by the intrusion of magma into cooler country rock. The area surrounding the intrusion where the contact metamorphism effects are present is called the metamorphic aureole.[5] Contact metamorphic rocks are usually known ashornfels. Rocks formed by contact metamorphism may not present signs of strong deformation and are often fine-grained.Contact metamorphism is greater adjacent to the intrusion and dissipates with distance from the contact. The size of the aureole depends on the heat of the intrusion, its size, and the temperature difference with the wall rocks. Dikes generally have small aureoles with minimal metamorphism whereas large ultramafic intrusions can have significantly thick and well-developed contact metamorphism.The metamorphic grade of an aureole is measured by the peak metamorphic mineral which forms in the aureole. This is usually related to the metamorphic temperatures ofpelitic or alumonisilicate rocks and the minerals they form.The metamorphic grades of aureoles are andalusite hornfels, sillimanite hornfels, pyroxene hornfels.Magmatic fluids coming from the intrusive rock may also take part in the metamorphic reactions. Extensive addition of magmatic fluids can significantly modify the chemistry of the affected rocks. In this case the metamorphism grades into metasomatism. If the intruded rock is rich in carbonate the result is a skarn. Fluorine-rich magmatic waters which leave a cooling granite may often form greisens within and adjacent to the contact of the granite. Metasomatic altered aureoles can localize the deposition of metallic oreminerals and thus are of economic interest.Prograde and retrograde metamorphism[edit]Metamorphism is further divided into prograde and retrograde metamorphism. Prograde metamorphism involves the change of mineral assemblages (paragenesis) with increasing temperature and (usually) pressure conditions. These are solid state dehydration reactions, and involve the loss of volatiles such as water or carbon dioxide. Prograde metamorphism results in rock characteristic of the maximum pressure and temperature experienced. Metamorphic rocks usually do not undergo further change when they are brought back to the surface.Retrograde metamorphism involves the reconstitution of a rock via revolatisation under decreasing temperatures (and usually pressures), allowing the mineral assemblages formed in prograde metamorphism to revert to those more stable at less extreme conditions. This is a relatively uncommon process, because volatiles must be present.Garnets with Mn-rich cores and Mn-poorer rims record growth zoning that represents the change from the lower-T conditions at which the garnet core grew to the higher-T conditions at which the garnet rim grew (i.e., prograde metamorphism involving increasing temperature and pressure). Mn is preferentially partitioned into garnet relative to most other common minerals, so Mn is sequestered in early-formed garnet, depleting the local environment of the growing garnet in Mn.(b) Minerals that show major element growth zoning probably did not experience very high metamorphic temperatures. At high temperature (> 700 C) and sufficient duration, zoning may be homogenized as intracrystalline diffusion becomes more effective at eliminating compositional variation. An unzoned mineral that is typically zoned at low-medium metamorphic grades has either experienced high temperature conditions or was never zoned (owing to a simple reaction history at limited P-T or to growth entirely at high-T).
