Clastic rocks are composed of fragments, or clasts, of pre-existing rock. Antelope Canyon is the most-visited and most-photographed Slot canyon in the American Southwest. Sandstone is a Sedimentary rock composed mainly of Sand -size Mineral or rock grains. In Geology, rock is a naturally occurring aggregate of Minerals and/or Mineraloids The Earth's outer solid layer the ‘ Lithosphere The term is most commonly, but not uniquely, applied to sedimentary rocks. Sedimentary rock is one of the three main rock types (the others being igneous and Metamorphic rock)
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Clastic metamorphic and igneous rocks
Clastic metamorphic rocks include breccias formed in faults, as well as some protomylonite and pseudotachylite. Metamorphic rock is the result of the transformation of an existing rock type the protolith, in a process called Metamorphism, which means "change Breccia (ˈbrɛtʃiə ˈbrɛʃiə breach is a rock composed of angular fragments of several Minerals or rocks in a matrix, that is a cementing material In Geology a fault, or fault line, is a planar rock fracture which shows evidence of relative movement Mylonite is a fine-grained compact rock produced by dynamic crystallization of the constituent minerals resulting in a Pseudotachylite is a fault rock that has the appearance of the Basaltic Glass, Tachylyte. Occasionally, metamorphic rocks can be brecciated via hydrothermal fluids, forming a hydrofracture breccia. Hydrothermal circulation in its most general sense is the circulation of hot water 'hydros' in the Greek meaning water and 'thermos' meaning heat Hydraulic fracturing is a method used to create fractures that extend from a Borehole into Rock formations which are typically maintained by a proppant
Clastic igneous rocks include pyroclastic volcanic rocks such as tuff, agglomerate and intrusive breccias, as well as some marginal eutaxitic and taxitic intrusive morphologies. Igneous rocks (etymology from Latin ignis, fire are rocks formed by solidification of cooled Magma (molten rock Pyroclastic rocks or pyroclastics (derived from the Greek πῦρ, meaning fire and κλαστός, meaning broken are Clastic rocks Volcanic rock is an Igneous rock of volcanic origin Texture Volcanic rocks are usually fine-grained or Aphanitic to glassy in Tuff (from the Italian "tufo" is a type of rock consisting of consolidated volcanic ash ejected from vents during a volcanic eruption Agglomerates (from the Latin 'agglomerare' meaning 'to form into a ball' are coarse accumulations of large blocks of volcanic material that contain at least Breccia (ˈbrɛtʃiə ˈbrɛʃiə breach is a rock composed of angular fragments of several Minerals or rocks in a matrix, that is a cementing material In Igneous Petrology, a term applicable to the layered or banded texture in some extrusive rock bodies Igneous clastic rocks are broken by flow, injection or explosive disruption of solid or semi-solid igneous rocks or lavas. Lava is molten rock expelled by a Volcano during an eruption When first expelled from a volcanic vent it is a Liquid at Temperatures
Clastic sediments
Clastic sedimentary rocks are rocks composed predominantly of broken pieces or clasts of older weathered and eroded rocks. Sedimentary rock is one of the three main rock types (the others being igneous and Metamorphic rock) Weathering is the decomposition of earth rocks, Soils and their Minerals through direct contact with the planet's Atmosphere. Erosion is the carrying away or displacement of solids ( Sediment, Soil, rock and other particles usually by the agents of currents such as wind Clastic sediments or sedimentary rocks are classified based on grain size, clast and cementing material (matrix) composition, and texture. The matrix or groundmass of rock is the fine-grained mass of material in which larger grains or Crystals are embedded The classification factors are often useful in determining a sample's environment of deposition.
Grain size determines the basic name of a clastic sedimentary rock. Grain size varies from clay in shales; through silt in siltstones; sand in sandstones; and gravel, cobble, to boulder sized fragments in conglomerates and breccias. Clay is a naturally occurring material composed primarily of fine-grained Minerals which show plasticity through a variable range of Water content, and Shale (also called mudstone) is a fine-grained Sedimentary rock whose original constituents were Clay minerals or Muds It is characterized by Silt is Soil or rock derived Granular material of a Grain size between sand and clay Siltstone is a Sedimentary rock which has a composition intermediate in grain size between the coarser Sandstones and the finer Mudstones and Sand is a naturally occurring Granular material composed of finely divided rock and Mineral particles Sandstone is a Sedimentary rock composed mainly of Sand -size Mineral or rock grains. Gravel is rock that is of a specific Particle size range In Geology, gravel is any loose rock that is larger than two millimeters (2mm In Geology, a boulder is a rock with grain size of usually no less than 256 mm (10 Inches diameter A conglomerate (kɒnˈglɒmərət is a rock consisting of individual stones that have become cemented together Breccia (ˈbrɛtʃiə ˈbrɛʃiə breach is a rock composed of angular fragments of several Minerals or rocks in a matrix, that is a cementing material The Krumbein phi (φ) scale numerically orders these terms in a logarithmic size scale. Particle size, also called grain size, refers to the Diameter of individual grains of Sediment, or the lithified particles in Clastic
Composition includes the chemical and mineralogic make-up of the single or varied fragments and the cementing material (matrix) holding the clasts together as a rock. A chemical substance is a Material with a definite chemical composition. A mineral is a naturally occurring substance formed through geological processes that has a characteristic chemical composition a highly ordered atomic structure and specific The matrix or groundmass of rock is the fine-grained mass of material in which larger grains or Crystals are embedded
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 from solid rock upstream. Erosion is the carrying away or displacement of solids ( Sediment, Soil, rock and other particles usually by the agents of currents such as wind
Sedimentary breccias
Sedimentary breccias are a type of clastic sedimentary rock which are composed of angular to subangular, randomly oriented clasts of other sedimentary rocks. Breccia (ˈbrɛtʃiə ˈbrɛʃiə breach is a rock composed of angular fragments of several Minerals or rocks in a matrix, that is a cementing material They are formed by either submarine debris flows, avalanches, mud flow or mass flow in an aqueous medium. Debris flows are often referred to as mudslides Mudflows jökulhlaups, or debris Avalanches. This article refers to the natural event For other uses see Avalanche (disambiguation An avalanche is an abrupt and rapid flow of snow often Technically, turbidites are a form of debris flow deposit and are a fine-grained peripheral deposit to a sedimentary breccia flow. Turbidite Geological formations have their origins in Turbidity current deposits, which are deposits from a form of underwater Avalanche that
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 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 Thick sequences of sedimentary (colluvial) breccias are generally formed next to fault scarps in grabens. A graben is a depressed block of land bordered by parallel faults Graben is German for ditch.
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. Drilling is the process of using a Drill bit in a Drill to produce cylindrical holes in solid materials such as wood or metal Sedimentary breccias are an integral host rock for many SEDEX ore deposits. Sedimentary exhalative deposits (abbreviated as SEDEX from SED imentary EX halative are Ore deposits which are interpreted to have been formed by release
Igneous clastic rocks
Igneous clastic rocks can be divided into two classes
- Broken, fragmental rocks produced by intrusive processes, usually associated with plutons or porphyry stocks
- Broken, fragmental rocks associated with volcanic eruptions, both of lava 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. In Geology, an intrusion is a body of Igneous rock that has Crystallized from molten Magma below the surface of the Earth. In Geology, an intrusion is a body of Igneous rock that has Crystallized from molten Magma below the surface of the Earth. Lava is molten rock expelled by a Volcano during an eruption When first expelled from a volcanic vent it is a Liquid at Temperatures Pyroclastic rocks or pyroclastics (derived from the Greek πῦρ, meaning fire and κλαστός, meaning broken are Clastic rocks Hydrothermal circulation in its most general sense is the circulation of hot water 'hydros' in the Greek meaning water and 'thermos' meaning heat This is particularly prominent in epithermal ore deposits and is associated with alteration zones around many intrusive rocks, especially granites. The neutron temperature, also called the neutron energy, indicates a free neutron's Kinetic energy, usually given in Electron volts The term An ore is a volume of rock containing components or Minerals in a mode of occurrence that renders it valuable for mining Metasomatism is the chemical alteration of a rock by Hydrothermal and other fluids Granite (ˈɡrænɪt is a common and widely occurring type of intrusive, Felsic, igneous rock. Many skarn and greisen deposits are associated with hydrothermal breccias. Skarn is a Metamorphic rock that is usually variably colored green or red occasionally grey black brown or white Greisen is a highly altered granitic rock or Pegmatite. Greisen is formed by autogenic alteration of a granite and is a class of endoskarn.
Impact breccias
A fairly rare form of clastic rock is formed during meteorite impact. A meteorite is a natural object originating in Outer space that survives an impact with the Earth 's surface This is composed primarily of ejecta; clasts of country rock, melted rock fragments, tektites (glass ejected from the impact crater) and exotic fragments, including fragments derived from the impactor itself. Tektites (from Greek tektos, molten are natural Glass objects up to a few centimeters in size which most scientists argue were formed by the impact of
Identifying a clastic rock as an impact breccia requires recognising shatter cones, tektites, spherulites, and the morphology of an impact crater, as well as potentially recognising particular chemical and trace element signatures, especially osmiridium. Shatter cones are rare geological features that are only known to form in the bedrock beneath Meteorite impact craters or underground nuclear explosions Spherulites, in Petrology, are small rounded bodies that commonly occur in Vitreous Igneous rocks They are often visible in specimens of Obsidian 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 Osmiridium, also called iridosmium, is a natural Alloy of Osmium and Iridium, with traces of other Platinum group metals found naturally
See also
- Textures of clastic rocks
- Breccia
- Igneous rocks including
- welded tuff and other pyroclastic rocks
- Lava, tuff and ignimbrite
- Cumulate rocks and other textural features of ultramafic to mafic layered intrusions
- Mylonite and pseudotachylite
- Shear (geology) or boudinage
- Diatremes or other forms of intrusive breccia. Rock microstructure includes the texture of a rock and the small scale rock structures Breccia (ˈbrɛtʃiə ˈbrɛʃiə breach is a rock composed of angular fragments of several Minerals or rocks in a matrix, that is a cementing material Tuff (from the Italian "tufo" is a type of rock consisting of consolidated volcanic ash ejected from vents during a volcanic eruption Pyroclastic rocks or pyroclastics (derived from the Greek πῦρ, meaning fire and κλαστός, meaning broken are Clastic rocks Lava is molten rock expelled by a Volcano during an eruption When first expelled from a volcanic vent it is a Liquid at Temperatures Tuff (from the Italian "tufo" is a type of rock consisting of consolidated volcanic ash ejected from vents during a volcanic eruption Ignimbrite is a Volcanic Pyroclastic rock often of Dacitic or Rhyolitic composition Cumulate rocks are Igneous rocks formed by the accumulation of Crystals from a Magma either by settling or floating Ultramafic to mafic layered intrusions are found in typically ancient Cratons and are rare but worldwide in distribution Mylonite is a fine-grained compact rock produced by dynamic crystallization of the constituent minerals resulting in a Pseudotachylite is a fault rock that has the appearance of the Basaltic Glass, Tachylyte. Study of geological shear is related to the study of Structural geology, Rock microstructure or rock texture and fault mechanics. boudinagejpg|thumb|Boudinaged Jasperoid in sheared basalt Fortnum Gold Mine Australia A diatreme is a breccia filled Volcanic pipe that was formed by a gaseous explosion
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