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Murli H. Manghnani - One of the best experts on this subject based on the ideXlab platform.
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Influence of Diagenesis on the electrical resistivity and the formation factor of deep-sea carbonate sediments
Geo-Marine Letters, 1992Co-Authors: Murli H. ManghnaniAbstract:Laboratory measurements of electrical resistivity on two DSDP pelagic carbonate sequences permitted the study of the effect of Diagenesis on the electrical and other physical properties such as velocity and porosity. Electrical resistivity and formation factor increase with sediment depth. Changes in porosity with progressive Diagenesis (that is, ooze-chalk-limestone) are observed, and changes in pore geometry are inferred. These changes are interpreted in terms of systematic variations in electrical and physical properties. Influence of silica on carbonate Diagenesis may result in significant change in pore geometry. This effect inhibits electrical conduction leading to complicated but generally high resistivity values for siliceous and cherty limestones. Compressional velocity correlates well with resistivity for both sequences.
Peter K Swart - One of the best experts on this subject based on the ideXlab platform.
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Quantifying early marine Diagenesis in shallow-water carbonate sediments
Geochimica et Cosmochimica Acta, 2018Co-Authors: Christian J. Bjerrum, Peter K Swart, Clara L. Blättler, John A. HigginsAbstract:Abstract Shallow-water carbonate sediments constitute one of the most abundant and widely used archives of Earth’s surface evolution. One of the main limitations of this archive is the susceptibility of the chemistry of carbonate sediments to post-depositional Diagenesis. Here, we develop a numerical model of marine carbonate Diagenesis that tracks the elemental and isotopic composition of calcium, magnesium, carbon, oxygen, and strontium, during dissolution of primary carbonates and re-precipitation of secondary carbonate minerals. The model is ground-truthed using measurements of geochemical proxies from sites on and adjacent to the Bahamas platform (Higgins et al., 2018) and authigenic carbonates in the organic-rich deep marine Monterey Formation (Blattler et al., 2015). Observations from these disparate sedimentological and diagenetic settings show broad covariation between bulk sediment calcium and magnesium isotopes that can be explained by varying the extent to which sediments undergo Diagenesis in seawater-buffered or sediment-buffered conditions. Model results indicate that the covariation between calcium and magnesium isotopes can provide a semi-quantitative estimate of the extent and style (fluid-buffered vs. sediment-buffered) of early marine Diagenesis. When applied to geochemical signatures in ancient carbonate rocks, the model can be used to quantify the impact of early marine Diagenesis on other geochemical proxies of interest (e.g. carbon and oxygen isotopes). The increasing recognition of early marine Diagenesis as an important phenomenon in shallow-water carbonate sediments makes this approach essential for developing accurate records of the chemical and climatic history of Earth from the chemical and isotopic composition of carbonate sediments.
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The geochemistry of carbonate Diagenesis: The past, present and future
Sedimentology, 2015Co-Authors: Peter K SwartAbstract:Stable carbon and oxygen isotopes (δ18O and δ13C values) and trace elements have been applied to the study of Diagenesis of carbonate rocks for over 50 years. As valuable as these insights have been, many problems regarding the interpretation of geochemical signals within mature rocks remain. For example, while the δ18O values of carbonate rocks are dependent both upon the temperature and the δ18O value of the fluid, and additional information including trace element composition aids in interpreting such signals, direct evidence of either the temperature or the composition of the fluids is required. Such information can be obtained by analysing the δ18O value of any fluid inclusions or by measuring the temperature using a method such as the ‘clumped’ isotope technique. Such data speak directly to a large number of problems in interpreting the oxygen isotope record including the well-known tendency for δ18O values of carbonate rocks to decrease with increasing age. Unlike the δ18O, δ13C values of carbonates are considered to be less influenced by Diagenesis and more a reflection of primary changes in the global carbon cycle through time. However, many studies have not sufficiently emphasized the effects of Diagenesis and other post-depositional influences on the eventual carbon isotopic composition of the rock with the classic paradigm that the present is the key to the past being frequently ignored. Finally, many additional proxies are poised to contribute to the interpretation of carbonate Diagenesis. Although the study of carbonate Diagenesis is at an exciting point with an explosion of new proxies and methods, care should be taken to understand both old and new proxies before applying them to the ancient record.
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35. GEOCHEMISTRY OF PERIPLATFORM CARBONATE SEDIMENTS, LEG 115, SITE 716 (MALDIVES ARCHIPELAGO, INDIAN OCEAN)1
1990Co-Authors: Mitchell J. Malone, Paul A. Baker, Stephen J Burns, Peter K SwartAbstract:Site 716 is a continuous sequence (upper Miocene to Holocene) of periplatform oozes and chalks from the Maldives Ridge, Indian Ocean. Mineralogical and geochemical studies of these carbonate sediments indicate that submarine burial Diagenesis has played an important role in the induration of sediments at this site. Metastable carbonates, high-magnesium calcite (HMC) and aragonite, convert to low-magnesium calcite (LMC) rapidly, within 1.1 and 6.0 Ma, respectively. Strontium concentrations in carbonate decrease with depth as the result of the burial Diagenesis of calcium carbonate, primarily aragonite, with excess strontium being expelled into pore waters. The formation of celestite at depth indicates that sufficient Diagenesis of carbonate sediments has occurred to saturate or supersaturate pore waters with respect to this authigenic mineral. Sodium also decreases monotonically with depth as a result of the burial Diagenesis of calcium carbonate. Magnesium and carbon and oxygen isotopic curves are remarkably similar. Carbon isotopic compositions record inputs of 13C-enriched components from shallow carbonate banks. Magnesium concentrations vary widely, recording enhanced episodes of cementation by LMC with slightly elevated magnesium contents. Positive shifts in oxygen isotopic composition also record episodes of cementation during burial Diagenesis. Intervals with increased accumulation rates of metastable components have undergone more rapid Diagenesis than intervals with predominately pelagic deposition.
S. D. Burley - One of the best experts on this subject based on the ideXlab platform.
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sandstone Diagenesis the evolution of sand to stone
2009Co-Authors: Richard H. Worden, S. D. BurleyAbstract:ates where geochemical reactions approach completion, gibbsite, kaolin group minerals and smectites form from aluminosilicate precursors. In cooler, temperate climates a greater variety of clay minerals occurs in weathering profiles reflecting metastable, intermediate breakdown products of aluminosilicates. Diagenesis is differentiated from metamorphism by a variety of mineral and thermal-history indices (Fig. 1; Frey, 1987; Slater et al., 1994), but broadly a temperature transition of 180–250°C is thought to separate the two regimes. The classic transition from Diagenesis to metamorphism was described eloquently in the Salton Sea geothermal field, south-east California, where sandstones of broadly similar composition are present over a temperature interval of 100°C to 350°C (McDowell & Elders, 1980). Here, clearly diagenetic, non-equilibrium mineral assemblages INTRODUCTION TO Diagenesis
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Sandstone Diagenesis: Recent and Ancient - Sandstone Diagenesis: The Evolution of Sand to Stone
Sandstone Diagenesis, 1Co-Authors: Richard H. Worden, S. D. BurleyAbstract:ates where geochemical reactions approach completion, gibbsite, kaolin group minerals and smectites form from aluminosilicate precursors. In cooler, temperate climates a greater variety of clay minerals occurs in weathering profiles reflecting metastable, intermediate breakdown products of aluminosilicates. Diagenesis is differentiated from metamorphism by a variety of mineral and thermal-history indices (Fig. 1; Frey, 1987; Slater et al., 1994), but broadly a temperature transition of 180–250°C is thought to separate the two regimes. The classic transition from Diagenesis to metamorphism was described eloquently in the Salton Sea geothermal field, south-east California, where sandstones of broadly similar composition are present over a temperature interval of 100°C to 350°C (McDowell & Elders, 1980). Here, clearly diagenetic, non-equilibrium mineral assemblages INTRODUCTION TO Diagenesis
Richard H. Worden - One of the best experts on this subject based on the ideXlab platform.
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sandstone Diagenesis the evolution of sand to stone
2009Co-Authors: Richard H. Worden, S. D. BurleyAbstract:ates where geochemical reactions approach completion, gibbsite, kaolin group minerals and smectites form from aluminosilicate precursors. In cooler, temperate climates a greater variety of clay minerals occurs in weathering profiles reflecting metastable, intermediate breakdown products of aluminosilicates. Diagenesis is differentiated from metamorphism by a variety of mineral and thermal-history indices (Fig. 1; Frey, 1987; Slater et al., 1994), but broadly a temperature transition of 180–250°C is thought to separate the two regimes. The classic transition from Diagenesis to metamorphism was described eloquently in the Salton Sea geothermal field, south-east California, where sandstones of broadly similar composition are present over a temperature interval of 100°C to 350°C (McDowell & Elders, 1980). Here, clearly diagenetic, non-equilibrium mineral assemblages INTRODUCTION TO Diagenesis
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Palaeoclimate, sequence stratigraphy and Diagenesis
Journal of Geochemical Exploration, 2000Co-Authors: Richard H. Worden, Alastair Ruffell, C. CornfordAbstract:Abstract Past and present climates have been characterised in terms of temperature and aridity/humidity. Global changes of atmospheric temperature occur on a periodicity of hundreds of millions of years (Icehouse and Greenhouse states of the Earth) to 500,000 years (glacial and interglacial episodes). Diagenetic conditions are influenced by temperature through the action of thermally controlled kinetic reactions. Meteoric waters influence Diagenesis through changing the amounts and chemistry of pore-fluid: in arid climates the volume of groundwater flux is diminished in comparison to humid climates. Relative sea-level change impacts shallow and deep burial Diagenesis by changing near-surface chemical conditions and the propagation of heat into the subsurface. Relative sea-level changes can induce sediment surface temperature changes of 20°C when the sediment surface changes from being close to or beneath the thermocline to being sub-aerially exposed. Such sea-level changes typically occur on a timescale of half a million years. In a Greenhouse world, such sea-level changes occur on a similar periodicity to glacial–interglacial cycles. On a longer time scale, Greenhouse to Icehouse conditions occur approximately every 100 ma. Burial Diagenesis and cementation may thus be episodic on timescales associated with palaeoclimatic and sequence stratigraphic events occurring on the surface, a few metres to thousands of metres above the zone where Diagenesis is occurring.
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Sandstone Diagenesis: Recent and Ancient - Sandstone Diagenesis: The Evolution of Sand to Stone
Sandstone Diagenesis, 1Co-Authors: Richard H. Worden, S. D. BurleyAbstract:ates where geochemical reactions approach completion, gibbsite, kaolin group minerals and smectites form from aluminosilicate precursors. In cooler, temperate climates a greater variety of clay minerals occurs in weathering profiles reflecting metastable, intermediate breakdown products of aluminosilicates. Diagenesis is differentiated from metamorphism by a variety of mineral and thermal-history indices (Fig. 1; Frey, 1987; Slater et al., 1994), but broadly a temperature transition of 180–250°C is thought to separate the two regimes. The classic transition from Diagenesis to metamorphism was described eloquently in the Salton Sea geothermal field, south-east California, where sandstones of broadly similar composition are present over a temperature interval of 100°C to 350°C (McDowell & Elders, 1980). Here, clearly diagenetic, non-equilibrium mineral assemblages INTRODUCTION TO Diagenesis
John A. Higgins - One of the best experts on this subject based on the ideXlab platform.
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Quantifying early marine Diagenesis in shallow-water carbonate sediments
Geochimica et Cosmochimica Acta, 2018Co-Authors: Christian J. Bjerrum, Peter K Swart, Clara L. Blättler, John A. HigginsAbstract:Abstract Shallow-water carbonate sediments constitute one of the most abundant and widely used archives of Earth’s surface evolution. One of the main limitations of this archive is the susceptibility of the chemistry of carbonate sediments to post-depositional Diagenesis. Here, we develop a numerical model of marine carbonate Diagenesis that tracks the elemental and isotopic composition of calcium, magnesium, carbon, oxygen, and strontium, during dissolution of primary carbonates and re-precipitation of secondary carbonate minerals. The model is ground-truthed using measurements of geochemical proxies from sites on and adjacent to the Bahamas platform (Higgins et al., 2018) and authigenic carbonates in the organic-rich deep marine Monterey Formation (Blattler et al., 2015). Observations from these disparate sedimentological and diagenetic settings show broad covariation between bulk sediment calcium and magnesium isotopes that can be explained by varying the extent to which sediments undergo Diagenesis in seawater-buffered or sediment-buffered conditions. Model results indicate that the covariation between calcium and magnesium isotopes can provide a semi-quantitative estimate of the extent and style (fluid-buffered vs. sediment-buffered) of early marine Diagenesis. When applied to geochemical signatures in ancient carbonate rocks, the model can be used to quantify the impact of early marine Diagenesis on other geochemical proxies of interest (e.g. carbon and oxygen isotopes). The increasing recognition of early marine Diagenesis as an important phenomenon in shallow-water carbonate sediments makes this approach essential for developing accurate records of the chemical and climatic history of Earth from the chemical and isotopic composition of carbonate sediments.
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The effects of Diagenesis and dolomitization on Ca and Mg isotopes in marine platform carbonates: Implications for the geochemical cycles of Ca and Mg
Geochimica et Cosmochimica Acta, 2014Co-Authors: Matthew S. Fantle, John A. HigginsAbstract:Abstract The Ca, Mg, O, and C isotopic and trace elemental compositions of marine limestones and dolostones from ODP Site 1196A, which range in depth (∼58 to 627 mbsf) and in depositional age (∼5 and 23 Ma), are presented. The objectives of the study are to explore the potential for non-traditional isotope systems to fingerprint Diagenesis, to quantify the extent to which geochemical proxies are altered during Diagenesis, and to investigate the importance of Diagenesis within the global Ca and Mg geochemical cycles. The data suggest that Ca, which has a relatively high solid to fluid mass ratio, can be isotopically altered during Diagenesis. In addition, the alteration of Ca correlates with the alteration of Mg in such a way that both can serve as useful tools for deciphering Diagenesis in ancient rocks. Bulk carbonate δ 44 Ca values vary between 0.60 and 1.31‰ (SRM-915a scale); the average limestone δ 44 Ca is 0.97 ± 0.24‰ (1SD), identical within error to the average dolostone (1.03 ± 0.15 1SD ‰). Magnesium isotopic compositions (δ 26 Mg, DSM-3 scale) range between −2.59‰ and −3.91‰, and limestones (−3.60 ± 0.25‰) and dolostones (−2.68 ± 0.07‰) are isotopically distinct. Carbon isotopic compositions (δ 13 C, PDB scale) vary between 0.86‰ and 2.47‰, with average limestone (1.96 ± 0.31‰) marginally offset relative to average dolostone (1.68 ± 0.57‰). The oxygen isotopic compositions (δ 18 O, PDB scale) of limestones (−1.22 ± 0.94‰) are substantially lower than the dolostones measured (2.72 ± 1.07‰). The isotopic data from 1196A suggest distinct and coherent trends in isotopic and elemental compositions that are interpreted in terms of diagenetic trajectories. Numerical modeling supports the contention that such trends can be interpreted as diagenetic, and suggests that the appropriate distribution coefficient ( K Mg ) associated with limestone Diagenesis is ∼1 to 5 × 10 −3 , distinctly lower than those values (>0.015) reported in laboratory studies. With respect to Mg isotopes, the modeling also suggest that diagenetic fractionation factors of ∼0.9955 (−4.5‰) and 0.9980 (−2‰) are appropriate for limestone Diagenesis and dolomitization, respectively.