Diapir

A diapir (/ˈdaɪ.əpɪər/;[1] French, from Greek diapeirein, to pierce through) is a type of geologic intrusion in which a more mobile and ductily deformable material is forced into brittle overlying rocks. Depending on the tectonic environment, diapirs can range from idealized mushroom-shaped Rayleigh–Taylor-instability-type structures in regions with low tectonic stress such as in the Gulf of Mexico to narrow dikes of material that move along tectonically induced fractures in surrounding rock. The term was introduced by the Romanian geologist Ludovic Mrazek, who was the first to understand the principle of salt tectonics and plasticity. The term "diapir" may be applied to igneous structures, but it is more commonly applied to non-igneous, relatively cold materials, such as salt domes and mud diapirs.

1990s Mathmos Astro
A lava lamp illustrates Rayleigh–Taylor instability-type diapirism in which the tectonic stresses are low.

In addition to Earth-based observations, diapirism is thought to occur on Neptune's moon Triton, Jupiter's moon Europa, Saturn's moon Enceladus, and Uranus's moon Miranda.[2]

Diapirs commonly intrude vertically upward along fractures or zones of structural weakness through denser overlying rocks because of density contrast between a less dense, lower rock mass and overlying denser rocks. The density contrast manifests as a force of buoyancy. The process is known as diapirism. The resulting structures are also referred to as piercement structures.

In the process, segments of the existing strata can be disconnected and pushed upwards. While moving higher, they retain much of their original properties such as pressure, which can be significantly different from that of the shallower strata they get pushed into. Such overpressured Floaters pose a significant risk when trying to drill through them. There is an analogy to a Galilean thermometer.[3]

Rock types such as evaporitic salt deposits, and gas charged muds are potential sources of diapirs. Diapirs also form in the earth's mantle when a sufficient mass of hot, less dense magma assembles. Diapirism in the mantle is thought to be associated with the development of large igneous provinces and some mantle plumes.

Explosive, hot volatile rich magma or volcanic eruptions are referred to generally as diatremes. Diatremes are not usually associated with diapirs, as they are small-volume magmas which ascend by volatile plumes, not by density contrast with the surrounding mantle.

Subduction-en
diapirs in a subducting plate boundary

Economic importance of diapirs

Salt dome hg
Geological cross section through the Northwestern Basin of Germany (Ostfriesland-Nordheide). Salt domes have penetrated younger layers and moved near to the surface. They sometimes form pockets where petroleum and natural gas can collect. Excavated salt domes are also used for underground storage.

Diapirs or piercement structures are structures resulting from the penetration of overlaying material. By pushing upward and piercing overlying rock layers, diapirs can form anticlines, salt domes and other structures capable of trapping petroleum and natural gas. Igneous intrusions themselves are typically too hot to allow the preservation of preexisting hydrocarbons.[4]

See also

  • Geyser – Hot spring characterized by intermittent discharge of water ejected turbulently and accompanied by steam
  • Granite – A common type of intrusive, felsic, igneous rock with granular structure
  • Granite dome – Rounded hills of bare granite formed by exfoliation
  • Hydrothermal vent – A fissure in a planet's surface from which geothermally heated water issues
  • Methods of pluton emplacement – The ways magma is accommodated in a host rock where the final result is a pluton
  • Mud volcano – Landform created by the eruption of mud or slurries, water and gases
  • Salt tectonics

References

  1. ^ American Heritage Dictionary of the English Language (Fourth Edition. Houghton Mifflin, 2000). "Archived copy". Archived from the original on 2006-12-08. Retrieved 2006-12-20.CS1 maint: archived copy as title (link).
  2. ^ Cassini Imaging Central Laboratory for Operations, Enceladus Rev 80 Flyby: Aug 11 '08. Retrieved 2008-08-15.
  3. ^ Don L. Anderson (2007). "The eclogite engine: Chemical geodynamics as a Galileo thermometer". In Gillian R. Foulger, Donna M. Jurdy (ed.). Plates, plumes, and planetary processes; Volume 430 of Special Papers. American Geological Society. ISBN 0-8137-2430-9.
  4. ^ Schlumberger Oilfield Glossary, on-line at [1]. Retrieved 2008-08-15.
Amos Frumkin

Amos Frumkin is an Israeli geologist.

Frumkin (עמוס פרומקין ) (1953 ) is a professor of geology at the Hebrew University of Jerusalem.Frumkin was born in Tel Aviv, Israel, in 1953. He wrote his Ph.D. thesis on "The karst system of the Mount Sdom salt diapir." His expertise is the geology of caves. In 2003, Frumkin led a team that radiocarbon-dated Siloam Tunnel. He is the author of the generally accepted explanation of how a tunnel dug by two teams working from opposite ends was engineered by the ancient Israelites before the development of trigonometry.

Asse II mine

The Asse II mine (Schacht Asse II) is a former salt mine used as a deep geological repository for radioactive waste in the Asse Mountains of Wolfenbüttel, Lower Saxony, Germany.

Batholith

A batholith (from Greek bathos, depth + lithos, rock) is a large mass of intrusive igneous rock (also called plutonic rock), larger than 100 square kilometres (40 sq mi) in area, that forms from cooled magma deep in the Earth's crust. Batholiths are almost always made mostly of felsic or intermediate rock types, such as granite, quartz monzonite, or diorite (see also granite dome).

Becquerel (Martian crater)

Becquerel is a 167 km-diameter crater at 22.1°N, 352.0°E on Mars, in Arabia Terra in Oxia Palus quadrangle. It is named after Antoine H. Becquerel.Photographs by the Mars Global Surveyor revealed layered sedimentary rocks in the crater. The layers appear to be only a few meters thick and show little variations in thickness. Recent studies with HiRISE have determined the exact thickness of the layers. The 66 layers measured showed one group of layers to average 3.6 metres (12 ft) and another group to average 36 metres (118 ft) in thickness. Patterns like this are usually produced on Earth through the effects of water; volcanic deposits would not produce ash or laval flows of such regular thickness and in any event, there are no nearby volcanic vents.There are cyclic variations in the thickness of the exposed sedimentary layers, possibly indicating cyclic variations in environmental conditions while the sediment was being laid down. Most of the layers are parallel to each other, suggesting they formed by vertical settling, but a few are cross-bedded, indicating that at the time that the layers were deposited the sediment was transported along the ground surface by wind or water. The sedimentary material appears to be easily eroded and active wind erosion may be continuing to the current day.Parts of the mound in Becquerel Crater show radial faults, These may be the result of a salt diapir. On Earth these are associated with methane seepage. Perhaps the methane detected on Mars from time to time is coming from these faults.Some parts of Becquerel show light-toned layers. Light-toned rocks on Mars have been associated with hydrated minerals like sulfates. The Mars Rover Opportunity examined such layers close-up with several instruments. Scientists are excited about finding hydrated minerals such as sulfates and clays on Mars because they are usually formed in the presence of water. Places that contain clays and/or other hydrated minerals would be good places to look for evidence of life.Many craters once contained lakes. Because some crater floors show deltas, we know that water had to be present for some time. Dozens of deltas have been spotted on Mars. Deltas form when sediment is washed in from a stream entering a quiet body of water. It takes a bit of time to form a delta, so the presence of a delta is exciting; it means water was there for a time, maybe for many years. Primitive organisms may have developed in such lakes; hence, some craters may be prime targets for the search for evidence of life on the Red Planet.

Cold seep

A cold seep (sometimes called a cold vent) is an area of the ocean floor where hydrogen sulfide, methane and other hydrocarbon-rich fluid seepage occurs, often in the form of a brine pool. Cold does not mean that the temperature of the seepage is lower than that of the surrounding sea water. On the contrary, its temperature is often slightly higher. The "cold" is relative to the very warm (at least 60 °C or 140 °F) conditions of a hydrothermal vent. Cold seeps constitute a biome supporting several endemic species.

Cold seeps develop unique topography over time, where reactions between methane and seawater create carbonate rock formations and reefs. These reactions may also be dependent on bacterial activity. Ikaite, a hydrous calcium carbonate, can be associated with oxidizing methane at cold seeps.

Connolly Basin crater

Connolly Basin is a 9 km-diameter impact crater located in the Gibson Desert of central Western Australia. It lies adjacent to the Talawana Track 45 km west of the junction (Windy Corner) with the Gary Highway, but is difficult to access due to the remoteness of the area. It was originally thought to be a diapir (salt dome); an impact origin was first proposed in 1985.,

Dome (geology)

A dome is a feature in structural geology consisting of symmetrical anticlines that intersect each other at their respective apices. Intact, domes are distinct, rounded, spherical-to-ellipsoidal-shaped protrusions on the Earth's surface. However, a transect parallel to Earth's surface of a dome features concentric rings of strata. Consequently, if the top of a dome has been eroded flat, the resulting structure in plan view appears as a bullseye, with the youngest rock layers at the outside, and each ring growing progressively older moving inwards. These strata would have been horizontal at the time of deposition, then later deformed by the uplift associated with dome formation.

Flinders Ranges, South Australia

Flinders Ranges is a locality in the Australian state of South Australia located in the mountain range of the same name, about 380 kilometres (240 miles) north of the state capital of Adelaide, about 86 kilometres (53 miles) north-east of the municipal seat of Quorn and about 131 kilometres (81 miles) north-east of the centre of Port Augusta in the state’s Far North region.Its boundaries were created in April 2013, with the name selected in respect to the ‘long established local name’. Its southern boundary was altered in November 2013 with the addition of land from Hawker and the transfer of land to Shaggy Ridge. The sites of the government towns of Edeowie and Mernmerna are also within its boundaries. These were both surveyed in 1863; Edeowie Post Office was open from c. 1870 to 1876 and from 1879 to 1881, while Mernmerna Post Office was open from 1874 to 1881 and again for a period in 1905.Flinders Ranges consists of the part of the mountain range between the ‘town centre’ of Hawker in the south and the 'town centre' of Parachilna in the north, as well as some land to the west of the range. In the north east it contains all of the protected areas of the Ikara-Flinders Ranges National Park and Bunkers Conservation Reserve, whose eastern boundaries align with that of the locality. The Marree railway line and The Outback Highway both pass through the west side of the locality while the Flinders Ranges Way passes through the south-east side. Granite

Granite ( ) is a common type of felsic intrusive igneous rock that is granular and phaneritic in texture. Granites can be predominantly white, pink, or gray in color, depending on their mineralogy. The word "granite" comes from the Latin granum, a grain, in reference to the coarse-grained structure of such a holocrystalline rock. Strictly speaking, granite is an igneous rock with between 20% and 60% quartz by volume, and at least 35% of the total feldspar consisting of alkali feldspar, although commonly the term "granite" is used to refer to a wider range of coarse-grained igneous rocks containing quartz and feldspar.

The term "granitic" means granite-like and is applied to granite and a group of intrusive igneous rocks with similar textures and slight variations in composition and origin. These rocks mainly consist of feldspar, quartz, mica, and amphibole minerals, which form an interlocking, somewhat equigranular matrix of feldspar and quartz with scattered darker biotite mica and amphibole (often hornblende) peppering the lighter color minerals. Occasionally some individual crystals (phenocrysts) are larger than the groundmass, in which case the texture is known as porphyritic. A granitic rock with a porphyritic texture is known as a granite porphyry. Granitoid is a general, descriptive field term for lighter-colored, coarse-grained igneous rocks. Petrographic examination is required for identification of specific types of granitoids. The extrusive igneous rock equivalent of granite is rhyolite.

Granite is nearly always massive (i.e., lacking any internal structures), hard, and tough. These properties have made granite a widespread construction stone throughout human history. The average density of granite is between 2.65 and 2.75 g/cm3 (165 and 172 lb/cu ft), its compressive strength usually lies above 200 MPa, and its viscosity near STP is 3–6·1019 Pa·s.The melting temperature of dry granite at ambient pressure is 1215–1260 °C (2219–2300 °F); it is strongly reduced in the presence of water, down to 650 °C at a few kBar pressure.Granite has poor primary permeability overall, but strong secondary permeability through cracks and fractures if they are present.

Ikara-Flinders Ranges National Park

The Ikara-Flinders Ranges National Park is situated approximately 400 km north of Adelaide in the northern central part of South Australia's largest mountain range, the Flinders Ranges. The park covers an area of 912 km², northeast of the small town of Hawker. The Heysen Trail and Mawson Trails pass through the park.

The park's most characteristic landmark is Wilpena Pound, a large, sickle-shaped, natural amphitheatre covering nearly 80 km², containing the range's highest peak, St Mary Peak (1,170 metres). On 12 February 2016 the park was renamed to include the Adnyamathanha word, Ikara, "meeting place", referring to the traditional name for Wilpena Pound.The park centre at Wilpena Pound is accessible by sealed road from Hawker. Other areas in the park can be reached by un-sealed roads, which are mostly accessible by two-wheel drive vehicles except in bad weather or after heavy rain. There are many lookouts, scenic vistas, small canyons and unusual rock formations located in the park. These include Wilpena Pound, Wilkawillina Gorge, Hucks Lookout, Brachina Gorge, Bunyeroo Gorge and Arkaroo Rock. The park has some stone ruins from early European settlement and Aboriginal rock art sites. A rock formation called the Great Wall of China is located just outside the park. Camping is permitted at many locations in the park.

Ludovic Mrazek

Ludovic Mrazec (July 17, 1867 in Craiova – June 9, 1944 in Bucharest) was a Romanian geologist and member of the Romanian Academy. He introduced the term diapir that denotes a type of intrusion in which a more mobile and ductily deformable material is forced into brittle overlying rocks. The phenomenon of "diapirism" allows rock salt to provide an effective trap for hydrocarbon deposits. In this way, Ludovic Mrazec explained the distribution of hydrocarbon accumulations in the Neogene Carpathian. Diapirism is commonly used as a basic concept in geological survey as well as in Planetary science.

Mount Toondina crater

Mount Toondina crater is an impact structure (or astrobleme), the eroded remnant of a former impact crater, situated in northern South Australia 45 km south of the township of Oodnadatta. Mount Toondina is the high point of a circular topographic feature rising out of an otherwise relatively flat desert area of the Eromanga Basin. An impact origin was first suggested in 1976, challenging the earlier diapir (salt dome) hypothesis, and strongly supported by subsequent studies. A geophysical survey using gravity methods indicates an internal structure typical of complex impact craters, including an uplifted centre, and suggests that the original crater was about 3–4 km in diameter. The crater must be younger than the Early Cretaceous age of the rocks in which it is situated, but otherwise is not well dated. It has clearly undergone significant erosion since the impact event.

Poza de la Sal

Poza de la Sal is a municipality and town located in the province of Burgos, Castile and León, Spain. According to the 2004 census (INE), the municipality has a population of 387 inhabitants.

Salt deformation

Salt deformation is the change of shape of natural salt bodies in response to forces and mechanisms that controls salt flow. Such deformation can generate large salt structures such as underground salt layers, salt diapirs or salt sheets at the surface. Strictly speaking, salt structures are formed by rock salt that is composed of pure halite (NaCl) crystal. However, most halite in nature appears in impure form, therefore rock salt usually refers to all rocks that composed mainly of halite, sometimes also as a mixture with other evaporites such as gypsum and anhydrite. Earth's salt deformation generally involves such mixed materials.

Due to the unique physical and chemical properties of rock salt such as its low density, high thermal conductivity and high solubility in water, it deforms distinctively in underground and surface environments compared with other rocks. Instability of rock salt is also given by its low viscosity, which allows rock salt to flow as a fluid. As the rock salt flows, a variety of salt structures are formed. Therefore, basins containing salt deform more easily than those lacking salt.

Salt dome

A salt dome is a type of structural dome formed when a thick bed of evaporite minerals (mainly salt, or halite) found at depth intrudes vertically into surrounding rock strata, forming a diapir. It is important in petroleum geology because salt structures are impermeable and can lead to the formation of a stratigraphic trap.

Salt glacier

A salt glacier (or namakier) is a rare flow of salt that is created when a rising diapir in a salt dome breaches the surface of the Earth. The name ‘salt glacier’ was given to this phenomenon due to the similarity of movement when compared with ice glaciers. The causes of these formations is primarily due to salt's unique properties and its surrounding geologic environment. A rising body of salt is referred to as a diapir; which rises to the surface and feeds the salt glacier. Salt structures are usually composed of halite, anhydrite, gypsum and clay minerals. Clays may be brought up with the salt, turning it dark. These salt flows are rare on earth. In a more recent discovery, scientists have found that they also occur on Mars, but are composed of sulfates.

The salt glaciers of the Zagros Mountains in Iran are halite whereas the salt glacier of Lüneburg Kalkberg, Germany is composed of gypsum and carbonate minerals.

Ancient flows have been preserved in various rock records by sedimentation. Late Triassic salt glaciers repeatedly flowed onto a basin in Germany and were buried with sediment to create a series of preserved glaciers. Miocene glaciers flowed into sheets in the northern Gulf of Mexico and were similarly preserved by overriding sediment.

Salt surface structures

Salt surface structures are extensions of salt tectonics that form at the Earth's surface when either diapirs or salt sheets pierce through the overlying strata. They can occur in any location where there are salt deposits, namely in cratonic basins, synrift basins, passive margins and collisional margins. These are environments where mass quantities of water collect and then evaporate; leaving behind salt and other evaporites to form sedimentary beds. When there is a difference in pressure, such as additional sediment in a particular area, the salt beds – due to the unique ability of salt to behave as a fluid under pressure – form into new structures. Sometimes, these new bodies form subhorizontal or moderately dipping structures over a younger stratigraphic unit, which are called allochthonous salt bodies or salt surface structures.

Salt tectonics

Salt tectonics, or halokinesis, or halotectonics, is concerned with the geometries and processes associated with the presence of significant thicknesses of evaporites containing rock salt within a stratigraphic sequence of rocks. This is due both to the low density of salt, which does not increase with burial, and its low strength.

Salt structures (excluding undeformed layers of salt) have been found in more than 120 sedimentary basins across the world.

Yinggehai basin

The Yinggehai-Song Hong Basin is located on the northwest of the South China Sea, between Hainan island and the coast of northern Vietnam. It is a large extensional pull-part basin in extensional continental marginal setting, developed along the Red River fault zone, which located at the suture of the Indochina Plate and Yangtze Plate (South China Plate).

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