Foliation is common in aphanitic as well as phaneritic metamorphic rocks. In order of increasing grain size, foliated textures are referred to as SLATY (aphanitic, very fine-grained), PHYLLITIC (aphanitic, fine-grained), SCHISTOSE (phaneritic). The corresponding rock types are called SLATE, PHYLLITE, and SCHIST. Textures of Metamorphic Rocks. Metamorphic textures are either granular or foliated. Here we examine only the foliated types. Foliation - any planar set of minerals, or banding of mineral concentrations, especially the planar structure that results from flattening of the mineral grains, like micas. The texture of a metamorphic rock is both a description of its constituent minerals along with their arrangement and size. Typically this will be initially described.
|Published:||13 June 2016|
|PDF File Size:||43.57 Mb|
|ePub File Size:||38.79 Mb|
When metamorphosed, those tiny crystals are slowly forced together under high pressure metamorphic textures begin to form larger, more visible crystals of calcite found in the metamorphic rock marble.
Pictures of Metamorphic Rocks
In other metamorphic textures, the loss or addition of chemicals results in metasomatism. This can best be seen in the metamorphic textures 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.
As metamorphism proceeds, the sheet structure silicates flat minerals with basal cleavage such as mica biotite and muscovite and chlorite start to grow.
- Metamorphic Textures
- Metamorphic rock - Wikipedia
- Metamorphic Rocks | Pictures of Foliated and Non-Foliated Types
- What are Metamorphic Rocks?
The sheets orient themselves perpendicular to the direction of maximum stress. The new parallel mineral flakes produce a planar metamorphic textures called foliation.
Foliation can be subtle or pronounced metamorphic textures on the degree of metamorphism. The foliated textures develop in the sequence listed below as temperature and pressure increases.
Here we just define the textures.
Below are descriptions and illustrations of how each texture develops. Slaty cleavage - a pervasive, parallel foliation layering of fine-grained platy minerals chlorite in a direction perpendicular to the direction of maximum stress.
This results in a banded, or foliated rock, with metamorphic textures bands showing the colors of metamorphic textures minerals that formed them. Textures are separated into foliated and non-foliated categories. Foliated rock is a product of differential stress that metamorphic textures the rock in one plane, sometimes creating a plane of cleavage.
Textures of Metamorphic Rocks
For example, slate is a foliated metamorphic metamorphic textures, originating from shale. Non-foliated rock does not have planar patterns of strain.
Rocks that were subjected to uniform pressure from all sides, or those that lack minerals with distinctive metamorphic textures habits, will not be foliated. Where a metamorphic textures has been metamorphic textures to differential stress, the type of foliation that develops depends on the metamorphic grade.
For instance, starting with a mudstonethe following sequence develops with increasing temperature: Another important mechanism of metamorphism is that of chemical reactions that occur between minerals without them melting. In the process atoms are exchanged between the minerals, and thus new minerals are formed.
Many complex high-temperature reactions may take place, and each mineral assemblage produced provides us with a clue as to the temperatures and pressures at the time of metamorphism.
Metasomatism is the metamorphic textures change in the bulk chemical composition of a rock that often occurs during the processes of metamorphism. In the initial stages a new foliation begins to develop in the rock as a result of compressional stress at some angle to the original bedding.
As the minerals that form this foliation metamorphic textures, they begin to break up the original beds into small pods. As the pods are compressed and extended, partly by recrystallization, they could metamorphic textures intersect again to form new compositional bands parallel to the new foliation.
In fine grained metamorphic rocks small scale folds, called kink bands, often develop in the rock as the result of application of compressional stress. A new foliation begins to develop along the axial metamorphic textures of the folds.
Quartz and feldspar may dissolve metamorphic textures a result of pressure solution and be reprecipitated at the hinges of the folds where the pressure is lower.
Fluids present during metamorphism metamorphic textures the ability to dissolve minerals and transport ions from one place in the rock to another.