What is the parent rock of schist?
Schist is a metamorphic rock usually formed originally from shale. It is a step above gneiss in the metamorphic process, meaning schist has been subjected to less intense heat and pressure. ... or probable parent material. Orthogneiss is formed by the metamorphism of igneous rocks; paragneiss results from the metamorphism of sedimentary rocks ...
What are facts about schist?
Facts about Schists. Schists are a group of metamorphic rocks which are medium to coarse-grained and of a fissile nature, meaning that at least one of the minerals in the rock crystallizes in platy form. Because of this, schists will split easily along these parallel layers. In fact, the word schist comes from a Greek word meaning “to split”.
What is the chemical composition of schist?
Types of Schist and Their Composition. As explained above, mica minerals such as chlorite, muscovite, and biotite are the characteristic minerals of schist. These were formed through metamorphism of the clay minerals present in the protolith. Other common minerals in schist include quartz and feldspars that are inherited from the protolith. Micas, feldspars, and quartz usually account for most of the minerals present in a schist.
What are the characteristics of schist?
Schist is a strongly foliated medium-grade metamorphic rock. It is characterized by an abundance of platy or elongated minerals (micas, chlorite, talc, graphite, amphiboles) in a preferred orientation.Varieties of this rock type share similarities in appearance (schistosity) but may be highly variable in composition.
What is the parent rock of schist?
ShaleMica SchistTypeMetamorphic RockMetamorphic TypeRegionalMetamorphic GradeLow to middle grade (Low to middle P – T)Parent RockShale or MudstoneMetamorphic EnvironmentLow to middle grade regional metamorphism along a convergent plate boundary4 more rows
Is shale a protolith of schist?
The sedimentary rock shale is usually the protolith for schist; during metamorphism, the very tiny clay minerals in shale recrystallize into micas that are large enough to see unaided.
What is the ultimate protolith material for schist?
Mica schist, the most common schistose rock and the second most common metamorphic rock, is composed mostly of mica (usually biotite or muscovite) and smaller amounts of quartz. The original parent rock (or protolith) of mica schist is shale.
What is the parent rock of talc schist?
Chlorite schist is typically formed by metamorphism of ultramafic igneous rocks, as is talc schist. Talc schist also forms from metamorphosis of talc-bearing carbonate rocks formed by hydrothermal alteration.
What is schist made of?
Most schists are composed largely of platy minerals such as muscovite, chlorite, talc, sericite, biotite, and graphite; feldspar and quartz are much less abundant in schist than in gneiss.
Is schist the parent rock of gneiss?
The parent rock of gneiss can be either granite or schist. Granite is an igneous rock that has cooled from magma. This rock generally has large crystals because it takes a while for it to cool within the Earth. If given more pressure and heat, this rock can turn into gneiss.
Which of the following is a potential protolith of schist?
The protolith of schists can be igneous (e.g. basalt, volcanic tuff) or sedimentary (clay, mud).
Where is schist formed?
It usually forms on a continental side of a convergent plate boundary where sedimentary rocks, such as shales and mudstones, have been subjected to compressive forces, heat, and chemical activity.
What type of rock is schist?
Schist is a type of metamorphic rock in which lamellar minerals, such as muscovite, biotite, and chlorite, or prismatic minerals, such as hornblende and tremolite, are oriented parallel to a secondary platy or laminated structure termed the schistosity.
What is the precursor of schist?
Thus, the precursors of schist are shale, slate, and phyllite. Less commonly, however, schist may form by metamorphism of fine-grained igneous rocks, such as tuff or basalt. Large and aligned flaky minerals, easily seen with the naked eye, define schists.
When was schist formed?
These rocks were originally part of a deep ocean trench, and they were subsequently overlain by sediments now known as the Brahma schist, which was laid down 1.75 billion years ago.
What is the parent rock of metamorphic?
Metamorphic rocks form from heat and pressure changing the original or parent rock into a completely new rock. The parent rock can be either sedimentary, igneous, or even another metamorphic rock.
Is shale a schist?
Schist (SHIST) is a metamorphic rock that can be formed from basalt ( igneous rock), shale ( sedimentary rock) or slate ( metamorphic rock). This type of rock is formed through tremendous heat and pressure.
Is schist made from shale?
Schist is a medium-grade metamorphic rock formed from mudstone or shale.
Which of the following is a potential protolith of schist?
The protolith of schists can be igneous (e.g. basalt, volcanic tuff) or sedimentary (clay, mud).
What type of rock is shale?
Shale is a soft, brittle, fine-grained, and easily eroded sedimentary rock formed from mineral-rich silt, or mud, that was deposited in an aquatic environment, buried by other sediment, and compacted and cemented into hard rock. When exposed at the surface by erosion, shale weathers into thin layers called plates.
What is a schistosity texture?
It formed by metamorphosis of mudstone and shale or some form of igneous rock. It usually has better crystallisation of mica minerals. They are biotite, chlorite and muscovite so this called schistosity texture.
How are slate and schist similar?
Conclusion. Schist and slate are very similar in that they are made from the same rock types except it is subjected to more heat and pressure. It is often referred to as schistosity because of its large mica flakes. Large crystals cause schist rocks to reflect lots of light which gives it a very shiny appearance.
What are schistose ironstones?
There are also schistose ironstones (hematite-schists) Origin of the schist include calc-schists, the foliated serpentines, which are once ultramafic masses rich in olivine. The white mica-schists, porphyroids and banded halleflintas, which have been derived from acid tuffs, quartz-porphyries and rhyolites.
Why are schist rocks shiny?
Large crystals cause schist rocks to reflect lots of light which gives it a very shiny appearance. The large crystals in schist indicate the amount of pressure and temperature that was used to make the rock. Specific this rocks are named for the dominant mineral that is a part of its make-up.
What is the difference between gneiss and schist?
The difference is that gneiss is generally more coarsely crystalline and has color banding and schist smells bad.
What type of rock is mica schist?
The most of the mica-schists are altered clays and shales so It is into the normal sedimentary rocks through various types of phyllite and mica-slates.They are among the most common metamorphic rocks.
What are schist rocks made of?
There are various features that distinguish schist rocks made from sedimentary rocks or those made from igneous.
What will happen to schistosity when feldspar increases?
Metamorphic reactions between minerals upon increased burial will lead to the loss of schistosity because feldspar increases in abundance as micas become unstable. This process will lead to the formation of high-grade metamorphic rock gneiss (and gneissose fabric which can be described as a poorly developed schistosity). Sometimes schist is imagined to contain at least 50% of elongated minerals 1, but in many cases the distinction between these rocks is just based on the qualitative assessment of a geologist describing the rocks in the field.
What type of rock has a twinned porphyroblast?
Staurolite schist with a twinned staurolite porphyroblast. 6. Blueschist (glaucophane schist with garnet and omphacite). Some schists contain no platy minerals like sheet silicates or graphite, but in this case these rocks have to display a linear fabric (elongated minerals in sub-parallel orientation).
How does schist form?
Schist can form only if the compressed rock contains lots of elongated or platy grains. Growth of mica crystals during the course of metamorphism makes the schistosity more evident. Mica schist is a very common variety. It is nicely glittering in sunshine because mica flakes act as small mirrors.
What type of rock is schist?
Schist is one of the most widespread rock types in the continental crust. Varieties of schistose metamorphic rocks: 1. Mica schist with porphyroblasts of garnet, staurolite and kyanite. 2. Graphite schist. 3. Chlorite schist (greenschist). 4. Quartzofeldspathic (gneissic) schist.
What causes schistosity in the crust?
Schistosity is a result of pressure in the crust which forces the grains to align perpendicular to the force applied. This force may be compressive (in mountain ranges) or simply caused by the weight of the overlying rocks. Schist can form only if the compressed rock contains lots of elongated or platy grains.
What is the most common rock type in the continental crust?
Individual mineral grains are discernible by the naked eye. This property sets it apart from slate. Schist is one of the most widespread rock types in the continental crust.
Which metamorphic grade rocks are fine grained?
Increasing metamorphic grade and corresponding rocks slate , phyllite and gneissose schist from the left to the right. Slate is a fine-grained rock with well-developed slaty cleavage. Phyllite is coarser and has a silky sheen on the cleavage surfaces. Individual crystals in schist are clearly discernible. The rock may display compositional banding and it often contains porphyroblasts (garnets in this rock).
Geology
- Schist is a strongly foliated medium-grade metamorphic rock. It is characterized by an abundance of platy or elongated minerals (micas, chlorite, talc, graphite, amphiboles) in a preferred orientation. Varieties of this rock type share similarities in appearance (schistosity) but may be highly variable in composition. Individual mineral grains are discernible by the naked eye. This pr…
Composition
- Some schists contain no platy minerals like sheet silicates or graphite, but in this case these rocks have to display a linear fabric (elongated minerals in sub-parallel orientation). Amphibole-bearing rocks with a lineated fabric belong to this group.
Formation
- Schistosity is a type of foliation, characterised by the preferred orientation of elongated or platy mineral grains (which are abundant in schistose rocks). Schistosity is a result of pressure in the crust which forces the grains to align perpendicular to the force applied. This force may be compressive (in mountain ranges) or simply caused by the ...
Naming
- The name of a particular schistose rock depends on the dominant minerals present muscovite-garnet-staurolite schist, for example. Several less known names have been given to a specific varieties: staurotile (contains staurolite porphyroblasts), prasinite (metamorphosed mafic rock with epidote, chlorite and hornblende in equal proportions), sismondinite (chloritoid is the domin…
Types
- Aluminous varieties often contain large crystals in a finer matrix. These crystals formed as the metamorphism progressed and they can convert to each-other as conditions change. Such large and often euhedral crystals are known as porphyroblasts. Common minerals that form porphyroblasts are garnet, staurolite, kyanite and andalusite. Porphyroblasts somewhat resembl…
Appearance
- Foliation surfaces are commonly wavy which reflects the presence and growth of porphyroblasts. Microscopically, schists commonly show a crenulation fabric which indicates the presence of older foliation that may represent an earlier episode of deformation4.
Sources
- 3. Schist. English Dictionary. Oxford University Press. 4. Van der Pluijm, B. A. (2007). Schist. In: McGraw Hill Encyclopedia of Science & Technology, 10th Edition. McGraw-Hill. Volume 16. 103.