All Topics  
Clastic rocks

 
Clastic Rocks

 
   Email Print
   Bookmark   Link
 

 

Clastic rocks
 
 
  Topics Clastic rocks Topic Home

Clastic rocks are composed of fragments, or clasts, of pre-existing rock
Rock (geology)

In geology, rock is a naturally occurring solid aggregate of minerals and/or mineraloids.The Earth's outer solid layer, the lithosphere, is made of rock....
. The term is most commonly, but not uniquely, applied to sedimentary rocks.
tic metamorphic rocks include breccia
Breccia

Breccia is a rock composed of angular fragments of several minerals or rocks in a Matrix , that is a Cementation material, that may be similar or different in composition to the fragments....
s formed in faults, as well as some protomylonite
Mylonite

Mylonite is a fine-grained, compact Rock produced by dynamic crystallization of the constituent minerals resulting in a reduction of the grain size of the rock....
 and pseudotachylite
Pseudotachylite

Pseudotachylite is a Geologic fault#Fault rock that has the appearance of the basaltic glass, tachylyte. It is generally found either along fault surfaces, often as the matrix to a breccia, or as Vein injected into the walls of the fault....
.






Discussion
Ask a question about 'Clastic rocks'
Start a new discussion about 'Clastic rocks'
Answer questions from other users
Full Discussion Forum



Encyclopedia


Lower Antelope 3 Md
Clastic rocks are composed of fragments, or clasts, of pre-existing rock
Rock (geology)

In geology, rock is a naturally occurring solid aggregate of minerals and/or mineraloids.The Earth's outer solid layer, the lithosphere, is made of rock....
. The term is most commonly, but not uniquely, applied to sedimentary rocks.

Clastic metamorphic and igneous rocks

Clastic metamorphic rocks include breccia
Breccia

Breccia is a rock composed of angular fragments of several minerals or rocks in a Matrix , that is a Cementation material, that may be similar or different in composition to the fragments....
s formed in faults, as well as some protomylonite
Mylonite

Mylonite is a fine-grained, compact Rock produced by dynamic crystallization of the constituent minerals resulting in a reduction of the grain size of the rock....
 and pseudotachylite
Pseudotachylite

Pseudotachylite is a Geologic fault#Fault rock that has the appearance of the basaltic glass, tachylyte. It is generally found either along fault surfaces, often as the matrix to a breccia, or as Vein injected into the walls of the fault....
. Occasionally, metamorphic rocks can be brecciated via hydrothermal fluids, forming a hydrofracture breccia. Clastic igneous rocks include pyroclastic volcanic rock
Volcanic rock

Volcanic rock is an igneous rock of Volcano origin.Texture Volcanic rocks are usually fine-grained or aphanitic to glassy in texture....
s such as tuff
Tuff

Tuff is a type of Rock consisting of consolidated volcanic ash ejected from vents during a volcanic eruption. Tuff is also sometimes called tufa, particularly when used as construction material....
, agglomerate
Agglomerate

Agglomerates are coarse accumulations of large blocks of volcano material that contain at least 75% volcanic bomb. Volcanic bombs differ from volcanic blocks in that their shape records fluidal surfaces: they may, for example, have ropy, cauliform, scoriaceous, or folded, chilled margins and spindle, spatter, ribbon, ragged, or amoeboid s...
 and intrusive breccia
Breccia

Breccia is a rock composed of angular fragments of several minerals or rocks in a Matrix , that is a Cementation material, that may be similar or different in composition to the fragments....
s, as well as some marginal eutaxitic
Eutaxitic

In igneous petrology, a term applicable to the layered or banded texture in some extrusive rock bodies. The layering is often caused by the compaction and flattening of glass shards and pumice fragments....
 and taxitic intrusive morphologies. Igneous clastic rocks are broken by flow, injection or explosive disruption of solid or semi-solid igneous rocks or lava
Lava

Lava is molten Rock expelled by a volcano during an eruption. When first expelled from a volcanic vent, it is a liquid at temperatures from 700 ?C to 1,200 ?C ....
s.

Clastic sediments

Clastic sedimentary rocks are rocks composed predominantly of broken pieces or clasts of older weathered
Weathering

Weathering is the decomposition of earth Rock , soils and their minerals through direct contact with the planet's atmosphere. Weathering occurs in situ, or "with no movement", and thus should not be confused with erosion, which involves the movement of rocks and minerals by agents such as water, ice, wind, and gravity....
 and eroded
Erosion

For morphological image processing operations, see Erosion 'For use of in dermatopathology, see Erosion Erosion is the removal of solids in the natural environment....
 rocks. Clastic sediments or sedimentary rocks are classified based on grain size, clast and cementing material (matrix
Matrix (geology)

The matrix or groundmass of rock is the fine-grained mass of material in which larger grains or crystals are embedded.The matrix of an igneous rock consists of fine-grained, often microscopic, crystals in which larger crystals are embedded....
) composition, and texture. The classification factors are often useful in determining a sample's environment of deposition
Sedimentary depositional environment

In geology, sedimentary depositional environment describes the combination of physical, chemical and biological processes associated with the deposition of a particular type of sediment and, therefore, the rock types that will be formed after lithification, if the sediment is preserved in the rock record....
. Grain size determines the basic name of a clastic sedimentary rock. Grain size varies from clay
Clay

Clay is a naturally occurring material composed primarily of fine-grained minerals, which show plasticity through a variable range of water content, and which can be hardened when dried and/or fired....
 in shale
Shale

Shale is a fine-grained sedimentary rock whose original constituents were clay minerals or muds. It is characterized by thin laminae breaking with an irregular curving fracture, often splintery and usually parallel to the often-indistinguishable bedding plane....
s; through silt
Silt

Silt is soil or Rock derived granular material of a Particle size between sand and clay. Silt may occur as a soil or as suspended sediment in a surface water body....
 in siltstone
Siltstone

Siltstone is a sedimentary rock which has a composition intermediate in Particle size between the coarser sandstones and the finer mudstones and shales....
s; sand
Sand

Sand is a naturally occurring granular material composed of finely divided rock and mineral particles.As the term is used by geologists, sand particles range in diameter from 0.0625 to 2 millimeters....
 in sandstone
Sandstone

Sandstone is a sedimentary rock composed mainly of sand-size mineral or rock Particle size . Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust ....
s; and gravel
Gravel

Gravel is rock that is of a specific particle size range. Specifically, it is is any loose rock that is larger than two millimeters in its largest dimension and no more than 64 millimeters ....
, cobble
Cobble

Cobble may refer to:* A particular size of rock, larger than gravel* Cobblestone, partially-rounded rocks used for road paving* Hammerstone, a prehistoric stone tool...
, to boulder
Boulder

In geology, a boulder is a rock with Particle size of usually no less than 256 mm diameter. While a boulder may be small enough to move or roll manually, others are extremely massive....
 sized fragments in conglomerates
Conglomerate (geology)

A conglomerate is a Rock consisting of individual stones that have become cemented together. Conglomerates are sedimentary rocks consisting of rounded fragments and are thus differentiated from breccias, which consist of angular clasts....
 and breccia
Breccia

Breccia is a rock composed of angular fragments of several minerals or rocks in a Matrix , that is a Cementation material, that may be similar or different in composition to the fragments....
s. The Krumbein phi (f) scale
Particle size (grain size)

Particle size, also called grain size, refers to the diameter of individual grains of sediment, or the lithification particles in clastic rocks....
 numerically orders these terms in a logarithmic size scale. Composition includes the chemical and mineral
Mineral

A mineral is a naturally occurring solid formed through Geology processes that has a characteristic chemical composition, a highly ordered atomic structure, and specific physical properties....
ogic make-up of the single or varied fragments and the cementing material (matrix
Matrix (geology)

The matrix or groundmass of rock is the fine-grained mass of material in which larger grains or crystals are embedded.The matrix of an igneous rock consists of fine-grained, often microscopic, crystals in which larger crystals are embedded....
) holding the clasts together as a rock. An example clastic environment would be a river system, in which the full range of grains being transported by the moving water consist of pieces eroded
Erosion

For morphological image processing operations, see Erosion 'For use of in dermatopathology, see Erosion Erosion is the removal of solids in the natural environment....
 from solid rock upstream.

Sedimentary breccias

Sedimentary breccia
Breccia

Breccia is a rock composed of angular fragments of several minerals or rocks in a Matrix , that is a Cementation material, that may be similar or different in composition to the fragments....
s are a type of clastic sedimentary rock which are composed of angular to subangular, randomly oriented clasts of other sedimentary rocks. They are formed by either submarine debris flow
Debris flow

A Debris flow is a fast moving mass of unconsolidated, saturated debris that looks like flowing concrete. They differentiate from a mudflow by terms of the viscosity of the flow....
s, avalanches, mud flow or mass flow in an aqueous medium. Technically, turbidite
Turbidite

Turbidite geological formations have their origins in turbidity current Deposition , which are deposits from a form of underwater avalanche that are responsible for distributing vast amounts of clastic sediment into the deep ocean....
s are a form of debris flow deposit and are a fine-grained peripheral deposit to a sedimentary breccia flow. The other derivation of sedimentary breccia is as angular, poorly sorted, very immature fragments of rocks in a finer grained groundmass which are produced by mass wasting. These are, in essence, lithified colluvium
Colluvium

Colluvium is the name for loose bodies of sediment that have been deposited or built up at the bottom of a low-grade slope or against a barrier on that slope, transported by gravity....
. Thick sequences of sedimentary (colluvial) breccias are generally formed next to fault scarps in graben
Graben

A graben is a depression block of land bordered by parallel Fault s. Graben is German language for ditch.A graben is the result of a block of land being downthrown producing a valley with a distinct Escarpment on each side....
s. In the field, it may at times be difficult to distinguish between a debris flow sedimentary breccia and a colluvial breccia, especially if one is working entirely from drilling information. Sedimentary breccias are an integral host rock for many SEDEX ore deposits
Sedimentary exhalative deposits

Sedimentary exhalative deposits are ore deposits which are interpreted to have been formed by release of ore-bearing hydrothermal fluids into a water reservoir , resulting in the precipitation of Stratum ore....
.

Igneous clastic rocks

Basalt Breccia
Igneous clastic rocks can be divided into two classes
  • Broken, fragmental rocks produced by intrusive
    Intrusion

    In geology, an intrusion is a body of igneous rock that has crystallized from molten magma below the surface of the Earth. Bodies of magma that solidify underground before they reach the surface of the earth are called plutons, named for Pluto , the Roman mythology of the underworld....
     processes, usually associated with pluton
    Intrusion

    In geology, an intrusion is a body of igneous rock that has crystallized from molten magma below the surface of the Earth. Bodies of magma that solidify underground before they reach the surface of the earth are called plutons, named for Pluto , the Roman mythology of the underworld....
    s or porphyry stocks
  • Broken, fragmental rocks associated with volcanic eruptions, both of lava
    Lava

    Lava is molten Rock expelled by a volcano during an eruption. When first expelled from a volcanic vent, it is a liquid at temperatures from 700 ?C to 1,200 ?C ....
     and pyroclastic type


Hydrothermal clastic rocks

Hydrothermal clastic rocks are generally restricted to those formed by hydrofracture, the process by which hydrothermal circulation cracks and brecciates the wall rocks and fills it in with veins. This is particularly prominent in epithermal ore
Ore

An ore is a type of Rock that contains minerals such as gemstones and metals that can be extracted through mining and refined for use. Samples of ore in the form of exceptionally beautiful crystals, exotic layering visible when sectioned or polished or metallic presentations such as large nuggets or crystalline formations of metals suc...
 deposits and is associated with alteration zones
Metasomatism

Metasomatism is the chemical alteration of a Rock by hydrothermal and other fluids.Metasomatism can occur via the action of hydrothermal fluids from an igneous or Metamorphism source....
 around many intrusive rocks, especially granite
Granite

Granite is a common and widely occurring type of Intrusion , felsic, igneous rock rock . Granite has a medium to coarse texture, occasionally with some individual crystals larger than the groundmass forming a rock known as Porphyry ....
s. Many skarn
Skarn

Skarn is a metamorphic rock that is usually variably colored green or red, occasionally grey, black, brown or white.It usually forms by chemical metasomatism of rocks during metamorphism and in the contact zone of magmatic intrusions like granites with carbonate-rich rock s such as limestone or dolostone....
 and greisen
Greisen

Greisen is a highly altered granite rock or pegmatite. Greisen is formed by autogenic alteration of a granite and is a class of skarn.Greisens appear as highly metasomatism rocks, partly coarse, crystalline granite, partly vugh with miarolitic cavities, disseminated halide minerals such as fluorite, and occasionally metallic oxide and sulfi...
 deposits are associated with hydrothermal breccias.

Impact breccias

A fairly rare form of clastic rock is formed during meteorite
Meteorite

A meteorite is a natural object originating in outer space that survives an impact with the Earth's surface. While in space it is called a meteoroid....
 impact. This is composed primarily of ejecta; clasts of country rock, melted rock fragments, tektite
Tektite

Tektites are natural glass rocks up to a few centimeters in size, which most scientists argue were formed by the impact event of large meteorites on Earth's surface....
s (glass ejected from the impact crater) and exotic fragments, including fragments derived from the impactor itself. Identifying a clastic rock as an impact breccia requires recognising shatter cone
Shatter cone

Shatter cones are rare geological features that are only known to form in the bedrock beneath meteorite impact crater or Underground nuclear testing....
s, tektites, spherulite
Spherulite

Spherulites, in petrology, are small, rounded bodies that commonly occur in vitreous igneous rocks. They are often visible in specimens of obsidian, pitchstone and rhyolite as globules about the size of millet seed or rice grain, with a duller Lustre than the surrounding glassy base of the rock, and when they are examined with a lens they...
s, and the morphology of an impact crater
Impact crater

In the broadest sense, the term impact crater can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with larger body....
, as well as potentially recognizing particular chemical and trace element signatures, especially osmiridium
Osmiridium

Osmiridium, also called iridosmium, is a natural alloy of osmium and iridium, with traces of other platinum group metals, found naturally or man-made....
.

See also

  • Textures
    Rock microstructure

    Rock microstructure includes the Texture of a rock and the small scale rock structures. The words "texture" and "microstructure" are interchangeable, with the latter preferred in modern geological literature....
     of clastic rocks
  • Breccia
    Breccia

    Breccia is a rock composed of angular fragments of several minerals or rocks in a Matrix , that is a Cementation material, that may be similar or different in composition to the fragments....
  • Cataclasite
    Cataclasite

    Cataclasite is a metamorphic rock rock that is formed by mechanical shear stress during Geologic fault . It is either Cohesion or cohesive with poor schistosity....
  • Igneous rocks including
    • welded tuff
      Tuff

      Tuff is a type of Rock consisting of consolidated volcanic ash ejected from vents during a volcanic eruption. Tuff is also sometimes called tufa, particularly when used as construction material....
       and other pyroclastic rocks
    • Lava
      Lava

      Lava is molten Rock expelled by a volcano during an eruption. When first expelled from a volcanic vent, it is a liquid at temperatures from 700 ?C to 1,200 ?C ....
      , tuff
      Tuff

      Tuff is a type of Rock consisting of consolidated volcanic ash ejected from vents during a volcanic eruption. Tuff is also sometimes called tufa, particularly when used as construction material....
       and ignimbrite
      Ignimbrite

      Ignimbrite is a volcano pyroclastic rock, often of dacitic or rhyolitic composition."Ignimbrite" is the deposit of a pumice rich pyroclastic density current, or 'pyroclastic flow', a hot suspension of particles and gases that flows rapidly from a volcano, driven by a greater density than the surrounding atmosphere....
    • Cumulate rocks and other textural features of ultramafic to mafic layered intrusions
      Ultramafic to mafic layered intrusions

      Ultramafic to mafic layered intrusions are found in typically ancient cratons and are rare but worldwide in distribution. The intrusive complexes exhibit evidence of Fractional crystallization and crystal segregation by settling or floating of minerals from a melt....
  • Mylonite
    Mylonite

    Mylonite is a fine-grained, compact Rock produced by dynamic crystallization of the constituent minerals resulting in a reduction of the grain size of the rock....
     and pseudotachylite
    Pseudotachylite

    Pseudotachylite is a Geologic fault#Fault rock that has the appearance of the basaltic glass, tachylyte. It is generally found either along fault surfaces, often as the matrix to a breccia, or as Vein injected into the walls of the fault....
  • Shear (geology) or boudinage
    Boudinage

    Boudinage is a geological term for structures formed by extension, where a rigid tabular body such as a bed of sandstone, is stretched and deformed amidst less competent surroundings....
  • Diatreme
    Diatreme

    A diatreme is a Breccia filled volcanic pipe that was formed by a gaseous explosion. Diatremes often breach the surface and produce a tuff cone or a filled relatively shallow crater known as a maar or other volcanic pipes....
    s or other forms of intrusive breccia.