The two textures of metamorphic rocks are foliated and non-foliated. Foliated means that the rock has the appearance of bands that go around it, while See full answer below. Become a member and. Metamorphic Rock Textures. Metamorphic textures and mineralogy develop progressively over several hundreds of feet/meters of drilling. Without careful examination by the Geologist, and the recognition of the subtle changes in mineralogy and texture, much time and money can be wasted by drilling past the economic basement. Since the change from.
Metamorphic rocks are one of the three types of rocks in the rock cycle. The name refers to the process of metamorphism, which means to undergo notable alteration yextures the original form. The outcome of metamorphism will cause significant enough physical and chemical changes to the original rock type, or protolithfor it to be considered a completely different type of rock.
Any rocos of protolith can undergo metamorphism by the two processes described below, resulting in various types of metamorphic rocks. The protolith must be exposed to temperatures high enough to to alter the mineral structure within the rock, but not high enough to turn the rock into magma, when it would become an igneous rock. However, different protoliths will require different temperature and pressure conditions for alteration.
This can occur through two different processes, known as regional and contact metamorphism. Regional Metamorphism occurs when rocks across a broad area are subjected to metamorphism, commonly through tectonic processes such how to obtain a marriage license in wisconsin continental collision or compression.
This may occur at a convergent plate boundarywhere two continental plates or one metamorpnic plate and one oceanic plate are moving toward each other. During the collision or compression event, entire regions are pushed to greater depths in the lithosphere and metanorphic the asthenosphere, exposing the protolith to greater temperatures and pressures.
In a convergent plate boundary, this may occur by the lower density plate subducting beneath the greater density plate, dragging parts of the higher density plate along with it.
Less dramatically, regional metamorphism may occur as a result of vertical pressure pushing a rock body downwards to greater depths of the lithosphere, simply because of deposition of younger rocks on the surface and the immense weight they carry. Rocks that have undergone regional metamorphism may be exposed at the surface millions of years later by the compounded processes of surface erosion and isostatic rebound.
The following charts display the approximate changes in temperature and pressure conditions with depth beneath the surface, known as the geothermal gradient and the geopressure gradient. Contact Metamorphism is a change made to the protolith by contact with an igneous intrusionwhich has temperatures high enough to teh metamorphism to parts of the protolith nearest to the intrusion.
The extent of contact metamorphism will depend upon the size and nature of the igneous intrusion, which could be as small as a dike or sill. The size of a formation resulting from contact metamorphism will be quite texturss ranging from one centimeter to meters in comparison to those formed by a regional metamorphic event. Rocks that surround an area that has been impacted by a meteor impact or other such extraterrestrial event may also exhibit some characteristics of contact metamorphism.
Some of the most common types wwhat metamorphic rocks are:. Any kind of protolith can undergo the two types of metamorphism to any degree, resulting in the huge amount of variation possible amongst the metamorphic rocks that may be formed.
The degree to which a protolith has been exposed to increased temperature and pressure conditions is referred to as metamorphic grade. The metamorphic facies uses the metamorphic minerals present in the rock to confine the pressure and temperature conditions the rock was exposed to, thus exposing the metamorphic grade of the rock. The following image shows the metamorphic facies and corresponding temperature-pressure conditions.
Here, we can see that members of the zeolite and blueschist facies are amongst the lowest metamorphic grades, while members of the greenschist and amphibolite facies are of medium grade, and members of how to add icons to desktop windows 8 granulite and ecologite facies are the highest metamorphic grade a protolith can undergo before eventually melting.
We can also observe that rocks that have been metamorphosed by contact metamorphism will generally be of a lower metamorphic grade than those that were metamorphosed by regional metamorphism.
Metamorphic rocks often have textkresor realignment of like minerals layered amongst one another in a recognizable pattern. Foliation results from rockx applied to a rock that is not uniform, and is primarily applied from one or two opposing directions. The foliated metamorphic textures are slaty, phyllitic, schistose and gneissic. Rocks with a granoblastic texture, such as marble and quartzite, do not display any foliation.
It is worth noting that foliation is usually a characteristic of formation by regional metamorphism, due to the immense amount thhe compression necessary to cause mineral realignment. When a protolith is exposed to extreme pressure conditions, there is a tendency for the elongate minerals within the rock to align in an orientation that reflects the primary direction of applied pressure. This realignment of minerals creates foliated metamorphic rocks. Foliated textures are usually easy observe and identify, once you know what you are looking for.
There are four metamorphic textures used to describe the varieties of foliated metamorphic rocks. In txetures of what is an enterprise java bean metamorphic grade to highest, they are:. Some metamorphic rocks, called non-foliated metamorphic rocks, may not display any sort of orientation or differentiation of minerals. Protoliths that do not contain any flat or elongated megamorphic such as mica will never produce a foliated texture, no matter how much pressure is applied.
Instead, we see non-foliated metamorphic rocks whose atomic and crystal structure differs significantly from the protolith. Non-foliated metamorphic rocks can also what are the two textures of metamorphic rocks formed by contact metamorphism, where significant heat is added to the protolith but not pressure.
This results in a baking of the protolith rather than compression, which allows the crystals within the rock to reorganize freely. The resulting metamorphic rock may not have any observable mineral pattern. One texture used to describe non-foliated metamorphic rocks is granoblastic.
Rocks that have a granoblastic texture will have relatively large, granular or anhedral crystals that are observable to the naked eye and are usually equal in size. Common metamorphic rocks that have granoblastic textures are marble and quartzite. The presence of metamorphic minerals, such as garnet, andalusite, staurolite, sillimanite and kyanite, indicate that the rock has undergone metamorphic processes.
Exposure to high temperature and pressure conditions cause the reorganizing of crystals within rocks, a process called recrystallization. This will cause an increase in size of individual crystals, which can be observed in the changes of physical properties of, for example, limestone to marble, or a quartzose sandstone to quartzite.
The sparry texture and visible crystals present in marble or quartzite visibly differs from the sugary texture of limestone or sandstone, where crystals are not visible or only visible under magnification. Which of these metamorphic facies represents the lowest metamorphic grade? Which of the following is NOT a foliated metamorphic texture? Enter your email to receive result:. Metamorphic Rocks by S. Squad November 15, Metamorphic Rocks Definition Metamorphic rocks are one of the three types of rocks in the rock cycle.
How Are Metamorphic Rocks Formed? Regional Metamorphism Regional Metamorphism occurs when rocks across a broad area are subjected to metamorphism, commonly through tectonic processes such as continental collision or compression. Geothermal gradient.
Geopressure gradient. Metamorphic Facies. Which of the following is NOT a metamorphic rock? Through which process might regional metamorphism occur? Convergent plate boundary. Meteor impact. Isostatic rebound. Notify of.
There are two main types of metamorphic rocks. These are Foliated metamorphic rocks and Non-foliated metamorphic rocks. 1. Oct 10, · Metamorphic rock, estimated to be as old as 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 . There are two major subdivisions of metamorphic rocks. Foliated – These have a planar foliation caused by the preferred orientation (alignment) of minerals and formed under differential stress. They have a significant amount of sheet silicate (platy minerals and are classified by composition, grain size, and foliation .
The two characteristics used to classify metamorphic rocks are foliation and lineation. These rocks are identified by the presence of certain mineral types and specific textures. Metamorphic rocks are those formed by other types of rocks that have been exposed to heat, pressure and time, which change them into a different type of rock. Metamorphic rocks can be formed from sedimentary, igneous and even other metamorphic rocks.
The composition of the rocks as well as the temperature and amount of pressure placed on them all play a role in the type of metamorphic rock formed. For this reason, metamorphic rocks can take on all types of colors and textures. However, foliation and lineation are two characteristics commonly seen in metamorphic rocks and are used to help identify and classify the rocks.
By studying metamorphic rocks, scientists can gain insight into the conditions inside the Earth during the metamorphic process. Foliation Foliation is an arrangement of flaky layers along the rock that break off easily.
Also known as salty cleavage, this characteristic is often seen in low-grade metamorphic rocks. Foliation occurs when uneven pressure acts on the parent rock and is accompanied by a change in temperature. It is the result of pressure only acting in one direction.
However, it is important to note that not all metamorphic rocks exhibit foliation nor does all foliation present in the same manner. Some examples of foliated metamorphic rocks are slate, mica, schist and gneiss. Foliated rocks are named after the type of foliation they exhibit. Since non-foliated rocks lack this feature, they are named for their mineral compositions instead.
Examples of non-foliated metamorphic rocks are marble, quartzite and hornfels. Lineation Lineation is another characteristic commonly seen in metamorphic rocks. Intersection lineation is the most common type of lineation seen in metamorphic rocks. This is formed by the intersection of any two foliations, such as bedding and cleavage or cleavage to a second cleavage. Lineation can run parallel or perpendicular to foliations. This feature forms mostly due to a drastic change in pressure and is less dependent on temperature changes.
Types of Metamorphism Metamorphism can occur in several ways. However, scientists have identified three main processes that lead to metamorphism: thermal, dynamic and metasomatic. Thermal metamorphism involves the structural and chemical alteration of rocks through the exposure of intense heat. A subcategory of this type is regional metamorphism which covers rock over a large area. A second subcategory is contact metamorphism, which refers to the small-scale heating of a localized portion of rock.
Dynamic metamorphism, sometimes referred to as burial metamorphism, does not alter the chemical composition of the rock. Instead, the extreme pressure imposed upon the rock causes it to change the physical structure. As rocks get buried, the weight of the material on top increases the pressure exerted on the rock, leading to a physical change.
Metasomatic metamorphism occurs when some of the elements in the rock minerals are replaced with others. This occurs when liquids and gases permeate the bedrock during the metamorphosis process.
The resulting rock has undergone both physical and chemical changes. What Are the Characteristics of Metamorphic Rocks? More From Reference. What Is Aristocracy?