Diagenesis (/ˌdaɪ.əˈdʒɛnəsɪs/) is the process that describes physical and chemical changes in sediments first caused by water-rock interactions, microbial activity, and compaction after their deposition. Increased pressure and temperature only start to play a role as sediments become buried much deeper in the Earth's crust.[1] In the early stages, the transformation of poorly consolidated sediments into sedimentary rock (lithification) is simply accompanied by a reduction in porosity and water expulsion (clay sediments), while their main mineralogical assemblages remain unaltered. As the rock is carried deeper by further deposition above, its organic content is progressively transformed into kerogens and bitumens. The process of diagenesis excludes surface alteration (weathering) and deep metamorphism. There is no sharp boundary between diagenesis and metamorphism, but the latter occurs at higher temperatures and pressures. Hydrothermal solutions, meteoric groundwater, rock porosity, permeability, dissolution/precipitation reactions, and time are all influential factors.
After deposition, sediments are compacted as they are buried beneath successive layers of sediment and cemented by minerals that precipitate from solution. Grains of sediment, rock fragments and fossils can be replaced by other minerals (e.g., calcite, siderite, pyrite, marcasite...) during diagenesis. Porosity usually decreases during diagenesis, except in rare cases such as dissolution of minerals and dolomitization.
The study of diagenesis in rocks is used to understand the geologic history they have undergone and the nature and type of fluids that have circulated through them. From a commercial standpoint, such studies aid in assessing the likelihood of finding various economically viable mineral and hydrocarbon deposits.
The process of diagenesis is also important in the decomposition of bone tissue.[2]
The term diagenesis, literally meaning "across generation",[3] is extensively used in geology. However, this term has filtered into the field of anthropology, archaeology and paleontology to describe the changes and alterations that take place on skeletal (biological) material. Specifically, diagenesis "is the cumulative physical, chemical, and biological environment; these processes will modify an organic object's original chemical and/or structural properties and will govern its ultimate fate, in terms of preservation or destruction".[4][5] In order to assess the potential impact of diagenesis on archaeological or fossilbones, many factors need to be assessed, beginning with elemental and mineralogical composition of bone and enveloping soil, as well as the local burial environment (geology, climatology, groundwater).[5]
The composite nature of bone, comprising one-third organic (mainly proteincollagen) and two thirds mineral (calcium phosphate mostly in the form of hydroxyapatite) renders its diagenesis more complex.[6] Alteration occurs at all scales from molecular loss and substitution, through crystallite reorganization, porosity, and microstructural changes, and in many cases, to the disintegration of the complete unit.[7] Three general pathways of the diagenesis of bone have been identified:
The dissolution of collagen depends on time, temperature, and environmental pH.[8] At high temperatures, the rate of collagen loss will be accelerated, and extreme pH can cause collagen swelling and accelerated hydrolysis.[8] Due to the increase in porosity of bones through collagen loss, the bone becomes susceptible to hydrolytic infiltration where the hydroxyapatite, with its affinity for amino acids, permits charged species of endogenous and exogenous origin to take up residence.[2]
The hydrolytic activity plays a key role in the mineral phase transformations that expose the collagen to accelerated chemical- and bio-degradation.[8] Chemical changes affect crystallinity.[2][9] Mechanisms of chemical change, such as the uptake of F− or CO3− may cause recrystallization where hydroxyapatite is dissolved and re-precipitated allowing for the incorporation or substitution of exogenous material.[2][9]
Once an individual has been interred, microbial attack, the most common mechanism of bone deterioration, occurs rapidly.[8] During this phase, most bone collagen is lost and porosity is increased.[2] The dissolution of the mineral phase caused by low pH permits access to the collagen by extracellular microbial enzymes thus microbial attack.[8]
Role in hydrocarbon generation
When animal or plant matter is buried during sedimentation, the constituent organic molecules (lipids, proteins, carbohydrates and lignin-humic compounds) break down due to the increase in temperature and pressure. This transformation occurs in the first few hundred meters of burial and results in the creation of two primary products: kerogens and bitumens.
It is generally accepted that hydrocarbons are formed by the thermal alteration of these kerogens (the biogenic theory). In this way, given certain conditions (which are largely temperature-dependent) kerogens will break down to form hydrocarbons through a chemical process known as cracking, or catagenesis.
A kinetic model based on experimental data can capture most of the essential transformation in diagenesis,[10] and a mathematical model in a compacting porous medium to model the dissolution-precipitation mechanism.[11] These models have been intensively studied and applied in real geological applications.
Diagenesis has been divided, based on hydrocarbon and coal genesis into: eodiagenesis (early), mesodiagenesis (middle) and telodiagenesis (late). During the early or eodiagenesis stage shales lose pore water, little to no hydrocarbons are formed and coal varies between lignite and sub-bituminous. During mesodiagenesis, dehydration of clay minerals occurs, the main development of oil genesis occurs and high to low volatile bituminous coals are formed. During telodiagenesis, organic matter undergoes cracking and dry gas is produced; semi-anthracite coals develop.[12]
Early diagenesis in newly formed aquatic sediments is mediated by microorganisms using different electron acceptors as part of their metabolism. Organic matter is mineralized, liberating gaseous carbon dioxide (CO2) in the porewater, which, depending on the conditions, can diffuse into the water column. The various processes of mineralization in this phase are nitrification and denitrification, manganese oxide reduction, iron hydroxide reduction, sulfate reduction, and fermentation.[13]
Role in bone decomposition
Diagenesis alters the proportions of organic collagen and inorganic components (hydroxyapatite, calcium, magnesium) of bone exposed to environmental conditions, especially moisture. This is accomplished by the exchange of natural bone constituents, deposition in voids or defects, adsorption onto the bone surface and leaching from the bone.[2][14]
See also
Chalcedony – Microcrystalline varieties of silica, may contain moganite as well
Chert – Hard, fine-grained sedimentary rock composed of cryptocrystalline silica
Flint – Cryptocrystalline form of the mineral quartz
Concretion – Compact mass formed by precipitation of mineral cement between particles
Fossil – Preserved remains or traces of organisms from a past geological age
^Wilson, Lyn; Pollard, A. Mark (2002). "Here Today, Gone Tomorrow? Integrated Experimentation and Geochemical Modeling in Studies of Archaeological Diagenetic Change". Accounts of Chemical Research. 35 (8): 644–651. doi:10.1021/ar000203s. PMID 12186569. S2CID 20545137.
^ abZapata J, Pérez-Sirvent C, Martínez-Sánchez MJ, Tovar P (October 2006). "Diagenesis, not biogenesis: Two late Roman skeletal examples". The Science of the Total Environment. 369 (1–3): 357–68. Bibcode:2006ScTEn.369..357Z. doi:10.1016/j.scitotenv.2006.05.021. PMID 16828844.
^Nicholson RA (1996). "Bone Degradation, Burial Medium and Species Representation: Debunking the Myths, and Experiment-based Approach". Journal of Archaeological Science. 23 (4): 513–533. doi:10.1006/jasc.1996.0049.
^Nielsen-Marsh CM (2000). "Patterns of Diagenesis in Bone I: The Effects of Site Environments". Journal of Archaeological Science. 27 (12): 1139–1150. doi:10.1006/jasc.1999.0537.
^ abcdefCollins MJ, Nielsen, Marsh CM, Hiller J, Smith CI, Roberts JP, et al. (2002). "The Survival of Organic Matter in Bone: A Review". Archaeometry. 44 (3): 383–394. doi:10.1111/1475-4754.t01-1-00071.
^Fowler AC, Yang XS (2003). "Dissolution/precipitation mechanisms for diagenesis in sedimentary basins". J. Geophys. Res. 108 (B10): 2269. Bibcode:2003JGRB..108.2509F. CiteSeerX10.1.1.190.4424. doi:10.1029/2002jb002269.
^Foscolos AE, Powell TG, Gunther PR (1976). "The use of clay minerals and inorganic and organic geochemical indicators for evaluating the degree of diagenesis and oil generating potential of shales". Geochimica et Cosmochimica Acta. 40 (8): 953–966. Bibcode:1976GeCoA..40..953F. doi:10.1016/0016-7037(76)90144-7.
^Lovley DR (June 1991). "Dissimilatory Fe(III) and Mn(IV) reduction". Microbiological Reviews. 55 (2): 259–87. doi:10.1128/MMBR.55.2.259-287.1991. PMC372814. PMID 1886521.
^Vass, A. A. (2001). "Beyond the grave: understanding human decomposition" (PDF). Microbiology Today. 28.
May 02, 2023
diagenesis, process, that, describes, physical, chemical, changes, sediments, first, caused, water, rock, interactions, microbial, activity, compaction, after, their, deposition, increased, pressure, temperature, only, start, play, role, sediments, become, bur. Diagenesis ˌ d aɪ e ˈ dʒ ɛ n e s ɪ s is the process that describes physical and chemical changes in sediments first caused by water rock interactions microbial activity and compaction after their deposition Increased pressure and temperature only start to play a role as sediments become buried much deeper in the Earth s crust 1 In the early stages the transformation of poorly consolidated sediments into sedimentary rock lithification is simply accompanied by a reduction in porosity and water expulsion clay sediments while their main mineralogical assemblages remain unaltered As the rock is carried deeper by further deposition above its organic content is progressively transformed into kerogens and bitumens The process of diagenesis excludes surface alteration weathering and deep metamorphism There is no sharp boundary between diagenesis and metamorphism but the latter occurs at higher temperatures and pressures Hydrothermal solutions meteoric groundwater rock porosity permeability dissolution precipitation reactions and time are all influential factors A form of diagenesis is permineralization in which buried organisms are replaced by minerals These trilobites Lloydolithus were replaced by pyrite during a specific type of permineralization called pyritization Permineralization in vertebra from Valgipes bucklandi After deposition sediments are compacted as they are buried beneath successive layers of sediment and cemented by minerals that precipitate from solution Grains of sediment rock fragments and fossils can be replaced by other minerals e g calcite siderite pyrite marcasite during diagenesis Porosity usually decreases during diagenesis except in rare cases such as dissolution of minerals and dolomitization The study of diagenesis in rocks is used to understand the geologic history they have undergone and the nature and type of fluids that have circulated through them From a commercial standpoint such studies aid in assessing the likelihood of finding various economically viable mineral and hydrocarbon deposits The process of diagenesis is also important in the decomposition of bone tissue 2 Contents 1 Role in anthropology and paleontology 2 Role in hydrocarbon generation 3 Role in bone decomposition 4 See also 5 ReferencesRole in anthropology and paleontology Edit Originally calcitic crinoid stem in cross section diagenetically replaced by marcasite in a siderite concretion Lower Carboniferous The term diagenesis literally meaning across generation 3 is extensively used in geology However this term has filtered into the field of anthropology archaeology and paleontology to describe the changes and alterations that take place on skeletal biological material Specifically diagenesis is the cumulative physical chemical and biological environment these processes will modify an organic object s original chemical and or structural properties and will govern its ultimate fate in terms of preservation or destruction 4 5 In order to assess the potential impact of diagenesis on archaeological or fossil bones many factors need to be assessed beginning with elemental and mineralogical composition of bone and enveloping soil as well as the local burial environment geology climatology groundwater 5 The composite nature of bone comprising one third organic mainly protein collagen and two thirds mineral calcium phosphate mostly in the form of hydroxyapatite renders its diagenesis more complex 6 Alteration occurs at all scales from molecular loss and substitution through crystallite reorganization porosity and microstructural changes and in many cases to the disintegration of the complete unit 7 Three general pathways of the diagenesis of bone have been identified Chemical deterioration of the organic phase Chemical deterioration of the mineral phase Micro biological attack of the composite 8 They are as follows The dissolution of collagen depends on time temperature and environmental pH 8 At high temperatures the rate of collagen loss will be accelerated and extreme pH can cause collagen swelling and accelerated hydrolysis 8 Due to the increase in porosity of bones through collagen loss the bone becomes susceptible to hydrolytic infiltration where the hydroxyapatite with its affinity for amino acids permits charged species of endogenous and exogenous origin to take up residence 2 The hydrolytic activity plays a key role in the mineral phase transformations that expose the collagen to accelerated chemical and bio degradation 8 Chemical changes affect crystallinity 2 9 Mechanisms of chemical change such as the uptake of F or CO3 may cause recrystallization where hydroxyapatite is dissolved and re precipitated allowing for the incorporation or substitution of exogenous material 2 9 Once an individual has been interred microbial attack the most common mechanism of bone deterioration occurs rapidly 8 During this phase most bone collagen is lost and porosity is increased 2 The dissolution of the mineral phase caused by low pH permits access to the collagen by extracellular microbial enzymes thus microbial attack 8 Role in hydrocarbon generation EditWhen animal or plant matter is buried during sedimentation the constituent organic molecules lipids proteins carbohydrates and lignin humic compounds break down due to the increase in temperature and pressure This transformation occurs in the first few hundred meters of burial and results in the creation of two primary products kerogens and bitumens It is generally accepted that hydrocarbons are formed by the thermal alteration of these kerogens the biogenic theory In this way given certain conditions which are largely temperature dependent kerogens will break down to form hydrocarbons through a chemical process known as cracking or catagenesis A kinetic model based on experimental data can capture most of the essential transformation in diagenesis 10 and a mathematical model in a compacting porous medium to model the dissolution precipitation mechanism 11 These models have been intensively studied and applied in real geological applications Diagenesis has been divided based on hydrocarbon and coal genesis into eodiagenesis early mesodiagenesis middle and telodiagenesis late During the early or eodiagenesis stage shales lose pore water little to no hydrocarbons are formed and coal varies between lignite and sub bituminous During mesodiagenesis dehydration of clay minerals occurs the main development of oil genesis occurs and high to low volatile bituminous coals are formed During telodiagenesis organic matter undergoes cracking and dry gas is produced semi anthracite coals develop 12 Early diagenesis in newly formed aquatic sediments is mediated by microorganisms using different electron acceptors as part of their metabolism Organic matter is mineralized liberating gaseous carbon dioxide CO2 in the porewater which depending on the conditions can diffuse into the water column The various processes of mineralization in this phase are nitrification and denitrification manganese oxide reduction iron hydroxide reduction sulfate reduction and fermentation 13 Role in bone decomposition EditDiagenesis alters the proportions of organic collagen and inorganic components hydroxyapatite calcium magnesium of bone exposed to environmental conditions especially moisture This is accomplished by the exchange of natural bone constituents deposition in voids or defects adsorption onto the bone surface and leaching from the bone 2 14 See also EditChalcedony Microcrystalline varieties of silica may contain moganite as well Chert Hard fine grained sedimentary rock composed of cryptocrystalline silica Flint Cryptocrystalline form of the mineral quartz Concretion Compact mass formed by precipitation of mineral cement between particles Fossil Preserved remains or traces of organisms from a past geological ageReferences Edit Marshak Stephen 2009 Essentials of Geology 3rd ed W W Norton amp Company ISBN 978 0393196566 a b c d e f Hedges R E 2002 Bone Diagenesis An Overview of Processes Archaeometry 44 3 319 28 doi 10 1111 1475 4754 00064 Oxford English Dictionary Wilson Lyn Pollard A Mark 2002 Here Today Gone Tomorrow Integrated Experimentation and Geochemical Modeling in Studies of Archaeological Diagenetic Change Accounts of Chemical Research 35 8 644 651 doi 10 1021 ar000203s PMID 12186569 S2CID 20545137 a b Zapata J Perez Sirvent C Martinez Sanchez MJ Tovar P October 2006 Diagenesis not biogenesis Two late Roman skeletal examples The Science of the Total Environment 369 1 3 357 68 Bibcode 2006ScTEn 369 357Z doi 10 1016 j scitotenv 2006 05 021 PMID 16828844 Nicholson RA 1996 Bone Degradation Burial Medium and Species Representation Debunking the Myths and Experiment based Approach Journal of Archaeological Science 23 4 513 533 doi 10 1006 jasc 1996 0049 Nielsen Marsh CM 2000 Patterns of Diagenesis in Bone I The Effects of Site Environments Journal of Archaeological Science 27 12 1139 1150 doi 10 1006 jasc 1999 0537 a b c d e f Collins MJ Nielsen Marsh CM Hiller J Smith CI Roberts JP et al 2002 The Survival of Organic Matter in Bone A Review Archaeometry 44 3 383 394 doi 10 1111 1475 4754 t01 1 00071 a b de Sousa DV Eltink E Oliveira RA Felix JF Guimaraes LM December 2020 Diagenetic processes in Quaternary fossil bones from tropical limestone caves Scientific Reports 10 1 21425 Bibcode 2020NatSR 1021425D doi 10 1038 s41598 020 78482 0 PMC 7722736 PMID 33293631 Abercrombie HJ Hutcheon IE Bloch JD Caritat PD 1994 Silica activity and the smectite illite reaction Geology 22 6 539 542 Bibcode 1994Geo 22 539A doi 10 1130 0091 7613 1994 022 lt 0539 saatsi gt 2 3 co 2 Fowler AC Yang XS 2003 Dissolution precipitation mechanisms for diagenesis in sedimentary basins J Geophys Res 108 B10 2269 Bibcode 2003JGRB 108 2509F CiteSeerX 10 1 1 190 4424 doi 10 1029 2002jb002269 Foscolos AE Powell TG Gunther PR 1976 The use of clay minerals and inorganic and organic geochemical indicators for evaluating the degree of diagenesis and oil generating potential of shales Geochimica et Cosmochimica Acta 40 8 953 966 Bibcode 1976GeCoA 40 953F doi 10 1016 0016 7037 76 90144 7 Lovley DR June 1991 Dissimilatory Fe III and Mn IV reduction Microbiological Reviews 55 2 259 87 doi 10 1128 MMBR 55 2 259 287 1991 PMC 372814 PMID 1886521 Vass A A 2001 Beyond the grave understanding human decomposition PDF Microbiology Today 28 Retrieved from https en wikipedia org w index php title Diagenesis amp oldid 1127588824, wikipedia, wiki, book, books, library,
