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Shale

October 20, 2023

For other uses, see Shale (disambiguation).

Shale is a fine-grained, clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals (hydrous aluminium phyllosilicates, e.g. kaolin, Al2Si2O5(OH)4) and tiny fragments (silt-sized particles) of other minerals, especially quartz and calcite.[1] Shale is characterized by its tendency to split into thin layers (laminae) less than one centimeter in thickness. This property is called fissility.[1] Shale is the most common sedimentary rock.[2]

Shale
Sedimentary rock
Shale
Composition
Clay minerals and quartz

The term shale is sometimes applied more broadly, as essentially a synonym for mudrock, rather than in the narrower sense of clay-rich fissile mudrock.[3]

Texture Edit

Shale typically exhibits varying degrees of fissility. Because of the parallel orientation of clay mineral flakes in shale, it breaks into thin layers, often splintery and usually parallel to the otherwise indistinguishable bedding planes.[4] Non-fissile rocks of similar composition and particle size (less than 0.0625 mm) are described as mudstones (1/3 to 2/3 silt particles) or claystones (less than 1/3 silt). Rocks with similar particle sizes but with less clay (greater than 2/3 silt) and therefore grittier are siltstones.[4][5]

 
Sample of drill cuttings of shale while drilling an oil well in Louisiana, United States. Sand grain = 2 mm in diameter

Composition and color Edit

 
Color chart for shale based on oxidation state and organic carbon content

Shales are typically gray in color and are composed of clay minerals and quartz grains. The addition of variable amounts of minor constituents alters the color of the rock. Red, brown and green colors are indicative of ferric oxide (hematite – reds), iron hydroxide (goethite – browns and limonite – yellow), or micaceous minerals (chlorite, biotite and illite – greens).[4] The color shifts from reddish to greenish as iron in the oxidized (ferric) state is converted to iron in the reduced (ferrous) state.[6] Black shale results from the presence of greater than one percent carbonaceous material and indicates a reducing environment.[4] Pale blue to blue-green shales typically are rich in carbonate minerals.[7]

Clays are the major constituent of shales and other mudrocks. The clay minerals represented are largely kaolinite, montmorillonite and illite. Clay minerals of Late Tertiary mudstones are expandable smectites, whereas in older rocks (especially in mid-to early Paleozoic shales) illites predominate. The transformation of smectite to illite produces silica, sodium, calcium, magnesium, iron and water. These released elements form authigenic quartz, chert, calcite, dolomite, ankerite, hematite and albite, all trace to minor (except quartz) minerals found in shales and other mudrocks.[4] A typical shale is composed of about 58% clay minerals, 28% quartz, 6% feldspar, 5% carbonate minerals, and 2% iron oxides.[8] Most of the quartz is detrital (part of the original sediments that formed the shale) rather than authigenic (crystallized within the shale after deposition).[9]

Shales and other mudrocks contain roughly 95 percent of the organic matter in all sedimentary rocks. However, this amounts to less than one percent by mass in an average shale. Black shales, which form in anoxic conditions, contain reduced free carbon along with ferrous iron (Fe2+) and sulfur (S2−). Amorphous iron sulfide, along with carbon, produce the black coloration.[4] Because amorphous iron sulfide gradually converts to pyrite, which is not an important pigment, young shales may be quite dark from their iron sulfide content, in spite of a modest carbon content (less than 1%), while a black color in an ancient shale indicates a high carbon content.[7]

Most shales are marine in origin,[10] and the groundwater in shale formations is often highly saline. There is evidence that shale acts as a semipermeable medium, allowing water to pass through while retaining dissolved salts.[11][12]

Formation Edit

The fine particles that compose shale can remain suspended in water long after the larger particles of sand have been deposited. As a result, shales are typically deposited in very slow moving water and are often found in lakes and lagoonal deposits, in river deltas, on floodplains and offshore below the wave base.[13] Thick deposits of shale are found near ancient continental margins[13] and foreland basins.[14] Some of the most widespread shale formations were deposited by epicontinental seas. Black shales[8] are common in Cretaceous strata on the margins of the Atlantic Ocean, where they were deposited in fault-bounded silled basins associated with the opening of the Atlantic during the breakup of Pangaea. These basins were anoxic, in part because of restricted circulation in the narrow Atlantic, and in part because the very warm Cretaceous seas lacked the circulation of cold bottom water that oxygenates the deep oceans today.[15]

Most clay must be deposited as aggregates and floccules, since the settling rate of individual clay particles is extremely slow.[16] Flocculation is very rapid once the clay encounters highly saline sea water.[17] Whereas individual clay particles are less than 4 microns in size, the clumps of clay particles produced by flocculation vary in size from a few tens of microns to over 700 microns in diameter. The floccules start out water-rich, but much of the water is expelled from the floccules as the clay minerals bind more tightly together over time (a process called syneresis).[18] Clay pelletization by organisms that filter feed is important where flocculation is inhibited. Filter feeders produce an estimated 12 metric tons of clay pellets per square kilometer per year along the U.S. Gulf Coast.[19]

As sediments continue to accumulate, the older, more deeply buried sediments begin to undergo diagenesis. This mostly consists of compaction and lithification of the clay and silt particles.[20][21] Early stages of diagenesis, described as eogenesis, take place at shallow depths (a few tens of meters) and are characterized by bioturbation and mineralogical changes in the sediments, with only slight compaction.[22] Pyrite may be formed in anoxic mud at this stage of diagenesis.[8][23]

Deeper burial is accompanied by mesogenesis, during which most of the compaction and lithification takes place. As the sediments come under increasing pressure from overlying sediments, sediment grains move into more compact arrangements, ductile grains (such as clay mineral grains) are deformed, and pore space is reduced.[24] In addition to this physical compaction, chemical compaction may take place via pressure solution. Points of contact between grains are under the greatest strain, and the strained mineral is more soluble than the rest of the grain. As a result, the contact points are dissolved away, allowing the grains to come into closer contact.[21]

It is during compaction that shale develops its fissility, likely through mechanical compaction of the original open framework of clay particles. The particles become strongly oriented into parallel layers that give the shale its distinctive fabric.[25] Fissility likely develops early in the compaction process, at relatively shallow depth, since fissility does not seem to vary with depth in thick formations.[26] Kaolinite flakes have less tendency to align in parallel layers than other clays, so kaolinite-rich clay is more likely to form nonfissile mudstone than shale. On the other hand, black shales often have very pronounced fissility (paper shales) due to binding of hydrocarbon molecules to the faces of the clay particles, which weakens the binding between particles.[27]

Lithification follows closely on compaction, as increased temperatures at depth hasten deposition of cement that binds the grains together. Pressure solution contributes to cementing, as the mineral dissolved from strained contact points is redeposited in the unstrained pore spaces. The clay minerals may be altered as well. For example, smectite is altered to illite at temperatures of about 55 to 200 °C (130 to 390 °F), releasing water in the process.[8] Other alteration reactions include the alteration of smectite to chlorite and of kaolinite to illite at temperatures between 120 and 150 °C (250 and 300 °F).[8] Because of these reactions, illite composes 80% of Precambrian shales, versus about 25% of young shales.[28]

Unroofing of buried shale is accompanied by telogenesis, the third and final stage of diagenesis.[22] As erosion reduces the depth of burial, renewed exposure to meteoric water produces additional changes to the shale, such as dissolution of some of the cement to produce secondary porosity. Pyrite may be oxidized to produce gypsum.[21]

Black shales are dark, as a result of being especially rich in unoxidized carbon. Common in some Paleozoic and Mesozoic strata, black shales were deposited in anoxic, reducing environments, such as in stagnant water columns.[8] Some black shales contain abundant heavy metals such as molybdenum, uranium, vanadium, and zinc.[8][29][30][31] The enriched values are of controversial origin, having been alternatively attributed to input from hydrothermal fluids during or after sedimentation or to slow accumulation from sea water over long periods of sedimentation.[30][32][33]

Fossils, animal tracks or burrows and even raindrop impressions are sometimes preserved on shale bedding surfaces. Shales may also contain concretions consisting of pyrite, apatite, or various carbonate minerals.[34]

Shales that are subject to heat and pressure of metamorphism alter into a hard, fissile, metamorphic rock known as slate. With continued increase in metamorphic grade the sequence is phyllite, then schist and finally gneiss.[35]

As hydrocarbon source rock Edit

Shale is the most common source rock for hydrocarbons (natural gas and petroleum).[8] The lack of coarse sediments in most shale beds reflects the absence of strong currents in the waters of the depositional basin. These might have oxygenated the waters and destroyed organic matter before it could accumulate. The absence of carbonate rock in shale beds reflects the absence of organisms that might have secreted carbonate skeletons, also likely due to an anoxic environment. As a result, about 95% of organic matter in sedimentary rocks is found in shales and other mudrocks. Individual shale beds typically have an organic matter content of about 1%, but the richest source rocks may contain as much as 40% organic matter.[36]

The organic matter in shale is converted over time from the original proteins, polysaccharides, lipids, and other organic molecules to kerogen, which at the higher temperatures found at greater depths of burial is further converted to graphite and petroleum.[37]

Historical mining terminology Edit

Before the mid-19th century, the terms slate, shale and schist were not sharply distinguished.[38] In the context of underground coal mining, shale was frequently referred to as slate well into the 20th century.[39] Black shale associated with coal seams is called black metal.[40]

See also Edit

 
Wikimedia Commons has media related to Shale.
  • Bakken Formation – Geological rock formation known for crude oil and gas production
  • Barnett Shale – Geological formation in Texas, United States
  • Bearpaw Formation – Geologic formation in North America
  • Burgess Shale – Fossil-bearing rock formation in the Canadian Rockies
  • Marcellus Formation – Middle Devonian age unit of sedimentary rock
  • Mazon Creek fossil beds – Conservation lagerstätte in Illinois on the National Register of Historic Places
  • Oil shale – Organic-rich fine-grained sedimentary rock containing kerogen
  • Shale gas – Natural gas trapped in shale formations
  • Wheeler Shale – Geologic formation in Utah notable for trilobite fossils
  • Wianamatta Shale – Geologic formation in Australia

References Edit

  1. ^ a b Blatt, Harvey and Robert J. Tracy (1996) Petrology: Igneous, Sedimentary and Metamorphic, 2nd ed., Freeman, pp. 281–292 ISBN 0-7167-2438-3
  2. ^ . prenhall.com. Archived from the original on 24 December 2014. Retrieved 2007-07-31.
  3. ^ Boggs, Sam (2006). Principles of sedimentology and stratigraphy (4th ed.). Upper Saddle River, N.J.: Pearson Prentice Hall. p. 139. ISBN 0131547283.
  4. ^ a b c d e f Blatt, Harvey and Robert J. Tracy (1996) Petrology: Igneous, Sedimentary and Metamorphic, 2nd ed., Freeman, pp. 281–292 ISBN 0-7167-2438-3
  5. ^ . prenhall.com. Archived from the original on 24 December 2014. Retrieved 2007-07-31.
  6. ^ Potter, Paul Edwin; Maynard, J. Barry; Pryor, Wayne A. (1980). Sedimentology of shale : study guide and reference source. New York: Springer-Verlag. pp. 54–56. ISBN 0387904301.
  7. ^ a b Potter, Maynard & Pryor 1980, p. 56.
  8. ^ a b c d e f g h Ferriday, Tim; Montenari, Michael (2016). "Chemostratigraphy and Chemofacies of Source Rock Analogues: A High-Resolution Analysis of Black Shale Successions from the Lower Silurian Formigoso Formation (Cantabrian Mountains, NW Spain)". Stratigraphy & Timescales. 1: 123–255. doi:10.1016/bs.sats.2016.10.004 – via Elsevier Science Direct.
  9. ^ Potter, Maynard & Pryor 1980, pp. 47–49.
  10. ^ Potter, Maynard & Pryor 1980, p. 72.
  11. ^ Potter, Maynard & Pryor 1980, p. 59.
  12. ^ Berry, F.A. (1960). "Geologic field evidence suggesting membrane properties of shales". AAPG Bulletin. 44 (6): 953–954. Retrieved 13 April 2021.
  13. ^ a b Blatt & Tracy 1996, p. 219.
  14. ^ Fillmore, Robert (2010). Geological evolution of the Colorado Plateau of eastern Utah and western Colorado, including the San Juan River, Natural Bridges, Canyonlands, Arches, and the Book Cliffs. Salt Lake City: University of Utah Press. p. 222-223, 236-241. ISBN 9781607810049.
  15. ^ Blatt & Tracy 1996, pp. 287–292.
  16. ^ Potter, Maynard & Pryor 1980, p. 8.
  17. ^ McCave, I.N. (1975). "Vertical flux of particles in the ocean". Deep Sea Research and Oceanographic Abstracts. 22 (7): 491–502. Bibcode:1975DSRA...22..491M. doi:10.1016/0011-7471(75)90022-4.
  18. ^ Potter, Maynard & Pryor 1980, p. 9.
  19. ^ Potter, Maynard & Pryor 1980, p. 10.
  20. ^ Blatt & Tracy 1996, pp. 265–280.
  21. ^ a b c Boggs 2006, pp. 147–154.
  22. ^ a b Choquette, P.W.; Pray, L.C. (1970). "Geologic Nomenclature and Classification of Porosity in Sedimentary Carbonates". AAPG Bulletin. 54. doi:10.1306/5D25C98B-16C1-11D7-8645000102C1865D.
  23. ^ Boggs 2006, p. 148.
  24. ^ Richardson, Ethan J.; Montenari, Michael (2020). "Assessing shale gas reservoir potential using multi-scaled SEM pore network characterizations and quantifications: The Ciñera-Matallana pull-apart basin, NW Spain". Stratigraphy & Timescales. 5: 677–755. doi:10.1016/bs.sats.2020.07.001. ISBN 9780128209912. S2CID 229217907 – via Elsevier Science Direct.
  25. ^ Lash, G. G.; Blood, D. R. (1 January 2004). "Origin of Shale Fabric by Mechanical Compaction of Flocculated Clay: Evidence from the Upper Devonian Rhinestreet Shale, Western New York, U.S.A.". Journal of Sedimentary Research. 74 (1): 110–116. Bibcode:2004JSedR..74..110L. doi:10.1306/060103740110.
  26. ^ Sintubin, Manuel (1994). "Clay fabrics in relation to the burial history of shales". Sedimentology. 41 (6): 1161–1169. Bibcode:1994Sedim..41.1161S. doi:10.1111/j.1365-3091.1994.tb01447.x.
  27. ^ Blatt, Harvey; Middleton, Gerard; Murray, Raymond (1980). Origin of sedimentary rocks (2d ed.). Englewood Cliffs, N.J.: Prentice-Hall. pp. 398–400. ISBN 0136427103.
  28. ^ Boggs 2006, pp. 142, 145–154.
  29. ^ R. Zangerl and E. S. Richardson (1963) The paleoecologic history of two Pennsylvanian shales, Fieldiana Memoirs v. 4, Field Museum of Natural History, Chicago
  30. ^ a b J.D. Vine and E.B. Tourtelot (1970). "Geochemistry of black shale deposits – A summary report". Economic Geology. 65 (3): 253–273. doi:10.2113/gsecongeo.65.3.253.
  31. ^ R.M. Coveney (1979). "Zinc concentrations in mid-continent Pennsylvanian black shales of Missouri and Kansas". Economic Geology. 74: 131–140. doi:10.2113/gsecongeo.74.1.131.
  32. ^ R.M. Coveney (2003) "Metalliferous Paleozoic black shales and associated strata" in D.R. Lenz (ed.) Geochemistry of Sediments and Sedimentary Rocks, Geotext 4, Geological Association of Canada pp. 135–144
  33. ^ H.D. Holland (1979). "Metals in black shales – A reassessment". Economic Geology. 70 (7): 1676–1680. doi:10.2113/gsecongeo.74.7.1676.
  34. ^ Potter, Maynard & Pryor 1980, pp. 22–23.
  35. ^ Potter, Maynard & Pryor 1980, p. 14.
  36. ^ Blatt, Middleton & Murray 1980, pp. 396–397.
  37. ^ Blatt, Middleton & Murray 1980, pp. 397.
  38. ^ R. W. Raymond (1881) "Slate" in A Glossary of Mining and Metallurigical Terms, American Institute of Mining Engineers. p. 78.
  39. ^ Albert H. Fay (1920) "Slate" in A Glossary of the Mining and Mineral Industry, United States Bureau of Mines. p. 622.
  40. ^ Herbert, Bucksch (1996). Dictionary geotechnical engineering: English German. Springer. p. 61. ISBN 978-3540581642.

External links Edit

  Media related to Shale at Wikimedia Commons

October 20, 2023
shale, other, uses, disambiguation, fine, grained, clastic, sedimentary, rock, formed, from, that, flakes, clay, minerals, hydrous, aluminium, phyllosilicates, kaolin, al2si2o5, tiny, fragments, silt, sized, particles, other, minerals, especially, quartz, calc. For other uses see Shale disambiguation Shale is a fine grained clastic sedimentary rock formed from mud that is a mix of flakes of clay minerals hydrous aluminium phyllosilicates e g kaolin Al2Si2O5 OH 4 and tiny fragments silt sized particles of other minerals especially quartz and calcite 1 Shale is characterized by its tendency to split into thin layers laminae less than one centimeter in thickness This property is called fissility 1 Shale is the most common sedimentary rock 2 ShaleSedimentary rockShaleCompositionClay minerals and quartzThe term shale is sometimes applied more broadly as essentially a synonym for mudrock rather than in the narrower sense of clay rich fissile mudrock 3 Contents 1 Texture 2 Composition and color 3 Formation 4 As hydrocarbon source rock 5 Historical mining terminology 6 See also 7 References 8 External linksTexture EditShale typically exhibits varying degrees of fissility Because of the parallel orientation of clay mineral flakes in shale it breaks into thin layers often splintery and usually parallel to the otherwise indistinguishable bedding planes 4 Non fissile rocks of similar composition and particle size less than 0 0625 mm are described as mudstones 1 3 to 2 3 silt particles or claystones less than 1 3 silt Rocks with similar particle sizes but with less clay greater than 2 3 silt and therefore grittier are siltstones 4 5 nbsp Sample of drill cuttings of shale while drilling an oil well in Louisiana United States Sand grain 2 mm in diameterComposition and color Edit nbsp Color chart for shale based on oxidation state and organic carbon contentShales are typically gray in color and are composed of clay minerals and quartz grains The addition of variable amounts of minor constituents alters the color of the rock Red brown and green colors are indicative of ferric oxide hematite reds iron hydroxide goethite browns and limonite yellow or micaceous minerals chlorite biotite and illite greens 4 The color shifts from reddish to greenish as iron in the oxidized ferric state is converted to iron in the reduced ferrous state 6 Black shale results from the presence of greater than one percent carbonaceous material and indicates a reducing environment 4 Pale blue to blue green shales typically are rich in carbonate minerals 7 Clays are the major constituent of shales and other mudrocks The clay minerals represented are largely kaolinite montmorillonite and illite Clay minerals of Late Tertiary mudstones are expandable smectites whereas in older rocks especially in mid to early Paleozoic shales illites predominate The transformation of smectite to illite produces silica sodium calcium magnesium iron and water These released elements form authigenic quartz chert calcite dolomite ankerite hematite and albite all trace to minor except quartz minerals found in shales and other mudrocks 4 A typical shale is composed of about 58 clay minerals 28 quartz 6 feldspar 5 carbonate minerals and 2 iron oxides 8 Most of the quartz is detrital part of the original sediments that formed the shale rather than authigenic crystallized within the shale after deposition 9 Shales and other mudrocks contain roughly 95 percent of the organic matter in all sedimentary rocks However this amounts to less than one percent by mass in an average shale Black shales which form in anoxic conditions contain reduced free carbon along with ferrous iron Fe2 and sulfur S2 Amorphous iron sulfide along with carbon produce the black coloration 4 Because amorphous iron sulfide gradually converts to pyrite which is not an important pigment young shales may be quite dark from their iron sulfide content in spite of a modest carbon content less than 1 while a black color in an ancient shale indicates a high carbon content 7 Most shales are marine in origin 10 and the groundwater in shale formations is often highly saline There is evidence that shale acts as a semipermeable medium allowing water to pass through while retaining dissolved salts 11 12 Formation EditThe fine particles that compose shale can remain suspended in water long after the larger particles of sand have been deposited As a result shales are typically deposited in very slow moving water and are often found in lakes and lagoonal deposits in river deltas on floodplains and offshore below the wave base 13 Thick deposits of shale are found near ancient continental margins 13 and foreland basins 14 Some of the most widespread shale formations were deposited by epicontinental seas Black shales 8 are common in Cretaceous strata on the margins of the Atlantic Ocean where they were deposited in fault bounded silled basins associated with the opening of the Atlantic during the breakup of Pangaea These basins were anoxic in part because of restricted circulation in the narrow Atlantic and in part because the very warm Cretaceous seas lacked the circulation of cold bottom water that oxygenates the deep oceans today 15 Most clay must be deposited as aggregates and floccules since the settling rate of individual clay particles is extremely slow 16 Flocculation is very rapid once the clay encounters highly saline sea water 17 Whereas individual clay particles are less than 4 microns in size the clumps of clay particles produced by flocculation vary in size from a few tens of microns to over 700 microns in diameter The floccules start out water rich but much of the water is expelled from the floccules as the clay minerals bind more tightly together over time a process called syneresis 18 Clay pelletization by organisms that filter feed is important where flocculation is inhibited Filter feeders produce an estimated 12 metric tons of clay pellets per square kilometer per year along the U S Gulf Coast 19 As sediments continue to accumulate the older more deeply buried sediments begin to undergo diagenesis This mostly consists of compaction and lithification of the clay and silt particles 20 21 Early stages of diagenesis described as eogenesis take place at shallow depths a few tens of meters and are characterized by bioturbation and mineralogical changes in the sediments with only slight compaction 22 Pyrite may be formed in anoxic mud at this stage of diagenesis 8 23 Deeper burial is accompanied by mesogenesis during which most of the compaction and lithification takes place As the sediments come under increasing pressure from overlying sediments sediment grains move into more compact arrangements ductile grains such as clay mineral grains are deformed and pore space is reduced 24 In addition to this physical compaction chemical compaction may take place via pressure solution Points of contact between grains are under the greatest strain and the strained mineral is more soluble than the rest of the grain As a result the contact points are dissolved away allowing the grains to come into closer contact 21 It is during compaction that shale develops its fissility likely through mechanical compaction of the original open framework of clay particles The particles become strongly oriented into parallel layers that give the shale its distinctive fabric 25 Fissility likely develops early in the compaction process at relatively shallow depth since fissility does not seem to vary with depth in thick formations 26 Kaolinite flakes have less tendency to align in parallel layers than other clays so kaolinite rich clay is more likely to form nonfissile mudstone than shale On the other hand black shales often have very pronounced fissility paper shales due to binding of hydrocarbon molecules to the faces of the clay particles which weakens the binding between particles 27 Lithification follows closely on compaction as increased temperatures at depth hasten deposition of cement that binds the grains together Pressure solution contributes to cementing as the mineral dissolved from strained contact points is redeposited in the unstrained pore spaces The clay minerals may be altered as well For example smectite is altered to illite at temperatures of about 55 to 200 C 130 to 390 F releasing water in the process 8 Other alteration reactions include the alteration of smectite to chlorite and of kaolinite to illite at temperatures between 120 and 150 C 250 and 300 F 8 Because of these reactions illite composes 80 of Precambrian shales versus about 25 of young shales 28 Unroofing of buried shale is accompanied by telogenesis the third and final stage of diagenesis 22 As erosion reduces the depth of burial renewed exposure to meteoric water produces additional changes to the shale such as dissolution of some of the cement to produce secondary porosity Pyrite may be oxidized to produce gypsum 21 Black shales are dark as a result of being especially rich in unoxidized carbon Common in some Paleozoic and Mesozoic strata black shales were deposited in anoxic reducing environments such as in stagnant water columns 8 Some black shales contain abundant heavy metals such as molybdenum uranium vanadium and zinc 8 29 30 31 The enriched values are of controversial origin having been alternatively attributed to input from hydrothermal fluids during or after sedimentation or to slow accumulation from sea water over long periods of sedimentation 30 32 33 nbsp Shale in Potokgraben the Karawanks Austria nbsp Splitting shale Messel oil shale with a large knife to reveal fossils nbsp Weathering shale at a road cut in southeastern KentuckyFossils animal tracks or burrows and even raindrop impressions are sometimes preserved on shale bedding surfaces Shales may also contain concretions consisting of pyrite apatite or various carbonate minerals 34 Shales that are subject to heat and pressure of metamorphism alter into a hard fissile metamorphic rock known as slate With continued increase in metamorphic grade the sequence is phyllite then schist and finally gneiss 35 As hydrocarbon source rock EditShale is the most common source rock for hydrocarbons natural gas and petroleum 8 The lack of coarse sediments in most shale beds reflects the absence of strong currents in the waters of the depositional basin These might have oxygenated the waters and destroyed organic matter before it could accumulate The absence of carbonate rock in shale beds reflects the absence of organisms that might have secreted carbonate skeletons also likely due to an anoxic environment As a result about 95 of organic matter in sedimentary rocks is found in shales and other mudrocks Individual shale beds typically have an organic matter content of about 1 but the richest source rocks may contain as much as 40 organic matter 36 The organic matter in shale is converted over time from the original proteins polysaccharides lipids and other organic molecules to kerogen which at the higher temperatures found at greater depths of burial is further converted to graphite and petroleum 37 Historical mining terminology EditBefore the mid 19th century the terms slate shale and schist were not sharply distinguished 38 In the context of underground coal mining shale was frequently referred to as slate well into the 20th century 39 Black shale associated with coal seams is called black metal 40 See also Edit nbsp Wikimedia Commons has media related to Shale Bakken Formation Geological rock formation known for crude oil and gas production Barnett Shale Geological formation in Texas United States Bearpaw Formation Geologic formation in North America Burgess Shale Fossil bearing rock formation in the Canadian Rockies Marcellus Formation Middle Devonian age unit of sedimentary rock Mazon Creek fossil beds Conservation lagerstatte in Illinois on the National Register of Historic Places Oil shale Organic rich fine grained sedimentary rock containing kerogen Shale gas Natural gas trapped in shale formations Wheeler Shale Geologic formation in Utah notable for trilobite fossils Wianamatta Shale Geologic formation in AustraliaPages displaying short descriptions of redirect targetsReferences Edit a b Blatt Harvey and Robert J Tracy 1996 Petrology Igneous Sedimentary and Metamorphic 2nd ed Freeman pp 281 292 ISBN 0 7167 2438 3 Rocks Materials of the Lithosphere Summary prenhall com Archived from the original on 24 December 2014 Retrieved 2007 07 31 Boggs Sam 2006 Principles of sedimentology and stratigraphy 4th ed Upper Saddle River N J Pearson Prentice Hall p 139 ISBN 0131547283 a b c d e f Blatt Harvey and Robert J Tracy 1996 Petrology Igneous Sedimentary and Metamorphic 2nd ed Freeman pp 281 292 ISBN 0 7167 2438 3 Rocks Materials of the Lithosphere Summary prenhall com Archived from the original on 24 December 2014 Retrieved 2007 07 31 Potter Paul Edwin Maynard J Barry Pryor Wayne A 1980 Sedimentology of shale study guide and reference source New York Springer Verlag pp 54 56 ISBN 0387904301 a b Potter Maynard amp Pryor 1980 p 56 a b c d e f g h Ferriday Tim Montenari Michael 2016 Chemostratigraphy and Chemofacies of Source Rock Analogues A High Resolution Analysis of Black Shale Successions from the Lower Silurian Formigoso Formation Cantabrian Mountains NW Spain Stratigraphy amp Timescales 1 123 255 doi 10 1016 bs sats 2016 10 004 via Elsevier Science Direct Potter Maynard amp Pryor 1980 pp 47 49 Potter Maynard amp Pryor 1980 p 72 Potter Maynard amp Pryor 1980 p 59 Berry F A 1960 Geologic field evidence suggesting membrane properties of shales AAPG Bulletin 44 6 953 954 Retrieved 13 April 2021 a b Blatt amp Tracy 1996 p 219 sfn error no target CITEREFBlattTracy1996 help Fillmore Robert 2010 Geological evolution of the Colorado Plateau of eastern Utah and western Colorado including the San Juan River Natural Bridges Canyonlands Arches and the Book Cliffs Salt Lake City University of Utah Press p 222 223 236 241 ISBN 9781607810049 Blatt amp Tracy 1996 pp 287 292 sfn error no target CITEREFBlattTracy1996 help Potter Maynard amp Pryor 1980 p 8 McCave I N 1975 Vertical flux of particles in the ocean Deep Sea Research and Oceanographic Abstracts 22 7 491 502 Bibcode 1975DSRA 22 491M doi 10 1016 0011 7471 75 90022 4 Potter Maynard amp Pryor 1980 p 9 Potter Maynard amp Pryor 1980 p 10 Blatt amp Tracy 1996 pp 265 280 sfn error no target CITEREFBlattTracy1996 help a b c Boggs 2006 pp 147 154 a b Choquette P W Pray L C 1970 Geologic Nomenclature and Classification of Porosity in Sedimentary Carbonates AAPG Bulletin 54 doi 10 1306 5D25C98B 16C1 11D7 8645000102C1865D Boggs 2006 p 148 Richardson Ethan J Montenari Michael 2020 Assessing shale gas reservoir potential using multi scaled SEM pore network characterizations and quantifications The Cinera Matallana pull apart basin NW Spain Stratigraphy amp Timescales 5 677 755 doi 10 1016 bs sats 2020 07 001 ISBN 9780128209912 S2CID 229217907 via Elsevier Science Direct Lash G G Blood D R 1 January 2004 Origin of Shale Fabric by Mechanical Compaction of Flocculated Clay Evidence from the Upper Devonian Rhinestreet Shale Western New York U S A Journal of Sedimentary Research 74 1 110 116 Bibcode 2004JSedR 74 110L doi 10 1306 060103740110 Sintubin Manuel 1994 Clay fabrics in relation to the burial history of shales Sedimentology 41 6 1161 1169 Bibcode 1994Sedim 41 1161S doi 10 1111 j 1365 3091 1994 tb01447 x Blatt Harvey Middleton Gerard Murray Raymond 1980 Origin of sedimentary rocks 2d ed Englewood Cliffs N J Prentice Hall pp 398 400 ISBN 0136427103 Boggs 2006 pp 142 145 154 R Zangerl and E S Richardson 1963 The paleoecologic history of two Pennsylvanian shales Fieldiana Memoirs v 4 Field Museum of Natural History Chicago a b J D Vine and E B Tourtelot 1970 Geochemistry of black shale deposits A summary report Economic Geology 65 3 253 273 doi 10 2113 gsecongeo 65 3 253 R M Coveney 1979 Zinc concentrations in mid continent Pennsylvanian black shales of Missouri and Kansas Economic Geology 74 131 140 doi 10 2113 gsecongeo 74 1 131 R M Coveney 2003 Metalliferous Paleozoic black shales and associated strata in D R Lenz ed Geochemistry of Sediments and Sedimentary Rocks Geotext 4 Geological Association of Canada pp 135 144 H D Holland 1979 Metals in black shales A reassessment Economic Geology 70 7 1676 1680 doi 10 2113 gsecongeo 74 7 1676 Potter Maynard amp Pryor 1980 pp 22 23 Potter Maynard amp Pryor 1980 p 14 Blatt Middleton amp Murray 1980 pp 396 397 Blatt Middleton amp Murray 1980 pp 397 R W Raymond 1881 Slate in A Glossary of Mining and Metallurigical Terms American Institute of Mining Engineers p 78 Albert H Fay 1920 Slate in A Glossary of the Mining and Mineral Industry United States Bureau of Mines p 622 Herbert Bucksch 1996 Dictionary geotechnical engineering English German Springer p 61 ISBN 978 3540581642 External links Edit nbsp Media related to Shale at Wikimedia Commons Retrieved from https en wikipedia org w index php title Shale amp oldid 1178205164, wikipedia, wiki, book, books, library,

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