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Vasileios Mavromatis - One of the best experts on this subject based on the ideXlab platform.
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the role of fe on the formation and diagenesis of interstratified glauconite smectite and illite smectite a case study of upper cretaceous shallow water carbonates
Chemical Geology, 2017Co-Authors: Andre Baldermann, Florian Mittermayr, Martin Dietzel, Laurence N Warr, Vasileios Mavromatis, Klaus WemmerAbstract:Abstract The widespread formation of interstratified glauconite-smectite (Gl-S) and illite-smectite (I-S) in modern and ancient diagenetic settings records the physicochemical conditions prevailing during clay mineral Authigenesis. To date, however, significant gaps in our knowledge persist in respect to the influence of interstitial solution chemistry, temperature and reaction kinetics on the evolution of composition, mineralogy and microstructure of Gl-S and I-S. Herein, we present a study on the reaction mechanisms and the physicochemical conditions that led to the precipitation of early diagenetic Gl-S and late diagenetic I-S on a stable carbonate platform during the Cenomanian at Langenstein in the Northern German Basin. The texture and the K-Ar age (95.0 ± 1.8 Ma) of the green glauconitized grains revealed that green-clay Authigenesis progressed in initially organic-rich, semi-confined micromilieus, i.e., in fecal pellets and in foraminifera, close to the sediment-seawater interface. The composition of Gl-S varied in the range (K + 0.20–0.74 Na + 0–0.10 Ca 2 + 0–0.05 ) 0.28–0.75 (Fe 3 + 0.63–1.20 Fe 2 + 0.08–0.24 Al 3 + 0.19–0.97 Mg 2 + 0.29–0.52 ) 2.01–2.12 [Al 3 + 0.09–0.35 Si 4 + 3.65–3.91 O 10 ](OH 2 ), and depended on the rate of aqueous Fe 2 + and K + ion diffusion, the micromilieu of glauconitization and on the bulk sedimentation rate. The mineralogical, microstructural and chemical changes of the ongoing Gl-S products revealed the following reaction for green-clay Authigenesis at Langenstein: Fe(III)-smectite reacted with monosilicic acid, goethite and aqueous K + , Mg 2 + and Fe 2 + to form glauconite and aqueous Na + , Ca 2 + and H + ions. This process considers complex mineral transformations commonly associated with glauconitization, such as early diagenetic oxidation of organic matter and microbial-catalyzed dissolution of Fe-(oxy)hydroxides, carbonates and detrital silicates. In contrast, the K-Ar age of I-S (68.0 ± 1.6 Ma) and its compositional variability, (K + 0.29–0.45 Na + 0–0.10 Ca 2 + 0–0.06 ) 0.30–0.55 (Fe 3 + 0.16–0.29 Fe 2 + 0–0.10 Al 3 + 1.37–1.68 Mg 2 + 0.18–0.43 ) 2.00–2.12 [Al 3 + 0.17–0.39 Si 4 + 3.61–3.83 O 10 ](OH 2 ), indicate a burial diagenetic origin for this mineral phase, rather than transformation of illitic clays into I-S during weathering under warm and humid climatic conditions. The results from kinetic modelling support a diagenetic origin of I-S (50–60%I layers and 50–40%S layers) and imply its formation by the replacement of pre-existing K-feldspar at high pore-fluid activity K/Na ratios and at low Fe 2 + concentrations. We propose that the substitution of Al 3 + for Fe 3 + , Fe 2 + and Mg 2 + in the octahedral sheet shifts the stability field of the kaolinite–Fe-Al-Mg-smectite–Fe-Al-Mg-illite (or glauconite) triple point to much lower monosilicic acid activities, and stabilizes the I-S (or Gl-S) structure. This reaction supports the idea that the (bio)availability of Fe is the rate-limiting factor for glauconitization, which is not the case for the diagenetic growth of I-S, whereby the pore water Fe 2 + concentration may be limited by the competing formation of Fe-(oxy)hydroxides and/or Fe-sulfides.
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substantial iron sequestration during green clay Authigenesis in modern deep sea sediments
Nature Geoscience, 2015Co-Authors: Andre Baldermann, Laurence N Warr, Ilse Letofskypapst, Vasileios MavromatisAbstract:Pyrite formation has been considered a key iron sink in organic-rich marine sediments. Analyses of sediments from the Ivory Coast–Ghana Marginal Ridge demonstrate that iron can be buried at greater rates during green-clay formation.
M. Esther Sanz-montero - One of the best experts on this subject based on the ideXlab platform.
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Microbially induced palygorskite-sepiolite Authigenesis in modern hypersaline lakes (Central Spain)
Applied Clay Science, 2018Co-Authors: Pablo Del Buey, Óscar Cabestrero, Xabier Arroyo, M. Esther Sanz-monteroAbstract:Abstract This study gives insight into the mechanisms of formation of palygorskite-sepiolite minerals that have remained elusive for many years. The occurrence of palygorskite-sepiolite and minor smectite in association with a variety of authigenic sulphates and Ca-Mg carbonate mineral deposits was identified in silicon-poor, saline to hypersaline ephemeral lakes in Central Spain. By a combination of sedimentological, mineralogical and petrological techniques (XRD, SEM, FEGSEM and TEM) it is shown that very small, poorly ordered palygorskite-sepiolite crystals resulted from the aggregation of nanocrystals within the matrix of the microbial mats (EPS) as it dehydrates. The Mg-rich clays nucleated on Mg-enriched EPS that also contain variable amounts of Si, Mg, Al and Fe, mostly derived from the degradation of siliciclastic minerals. The crystals have a broad compositional and textural range, from poorly ordered palygorskite laths to pure sepiolite bundles, suggesting that they grow through successive stages. Changes in the chemical composition of the fibers occur even at microscale, which is explained by the variability of the biogeochemical conditions prevailing in the microenvironments where the crystals grow. The overall results provide evidence for a biomediated-crystallization of palygorskite-sepiolite in microbial sediments.
Julita Biernacka - One of the best experts on this subject based on the ideXlab platform.
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Insight into diagenetic processes from authigenic tourmaline: An example from Carboniferous and Permian siliciclastic rocks of western Poland
Sedimentary Geology, 2019Co-Authors: Julita BiernackaAbstract:Abstract Authigenic tourmaline is a rare and minor component of siliciclastic rocks, however, once it occurs, it can be used to interpret a number of subsurface parameters and processes, such as fluid composition, redox state, salinity, pH, and fluid migration paths. Notwithstanding, the conditions of tourmaline Authigenesis still need to be recognize with greater clarity. Carboniferous and Permian siliciclastic rocks in the subsurface of western Poland in the vicinity of the Dolsk Fault show unusually high boron contents, at places surpassing 1000 μg/g, which are associated with the presence of authigenic tourmaline. The mineral forms fine, elongated crystals, of nano- to micrometer width, grouped in radiating or semi-parallel aggregates, which are dispersed in the clay matrix of shales and graywackes, coat grain surfaces and line secondary pores in porous sandstones, replace some grains in volcaniclastic breccia, and overgrow detrital tourmalines in quartzarenites. Regardless of host rock compositions, the tourmaline is Si-deficient, moderately Al-rich, and shows significant X-site vacancies and highly variable Mg/(Mg + Fetot) ratios. In rare zoned tourmaline, the Mg/(Mg + Fetot) ratios distinctly decrease and vacancies slightly increase towards the growth direction. The results suggest that the tourmaline nucleated rapidly under a strong driving force at high boron concentration and high temperature. The fluids which enabled the process were acidic, reducing, B- and Mg-bearing, and of low Na and Ca contents. The tourmaline grew primarily at the expense of kaolinite, possibly of other clay minerals and K-feldspar, in the temperature range ~150–200 °C. Its crystallization was a short episode in the diagenetic history of the host rocks. Tourmaline Authigenesis across the Carboniferous/Permian unconformity, in the proximity of a prominent fault zone, is evidence for fluid and heat migration along faults, and for temporarily open geochemical system during late diagenesis. The source of boron has been unproven, yet the circulation of bitterns originated from Upper Permian evaporites was highly probable.
Michael H. Engel - One of the best experts on this subject based on the ideXlab platform.
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Remagnetization and fluid flow in the Old Red Sandstone along the Great Glen Fault, Scotland
Journal of Geochemical Exploration, 2006Co-Authors: R. Douglas Elmore, Michael H. Engel, Shannon A. Dulin, John ParnellAbstract:Abstract The Devonian Old Red Sandstone in the vicinity of the Great Glen Fault (GGF) in Scotland contains two different components residing in hematite: a postfolding Carboniferous CRM1 in the Loch Ness area and a Cretaceous or perhaps Triassic CRM2 near Hilton. The CRM1 could be related to major fluid flow events in the Late Paleozoic which caused hematite Authigenesis and remagnetization along other faults in Scotland. The CRM2 near Hilton was also related to a fluid event in the Cretaceous or Triassic which caused hematite Authigenesis. The presence of different CRMs residing in hematite along different segments of the GGF is similar to what has been reported for other major faults in Scotland.
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Palaeomagnetic dating of fluid‐flow events in dolomitized rocks along the Highland Boundary Fault, central Scotland
Geofluids, 2002Co-Authors: R. D. Elmore, J. Parnell, Michael H. Engel, S Woods, M Abraham, Martin Baron, M. DavidsonAbstract:Palaeomagnetic and geochemical studies of Cambrian–Ordovician serpentinite in the Highland Border Complex (HBC), a tectonic terrane along the Highland Boundary Fault (HBF) in Scotland, indicate that the HBF was a conduit for fluids in the Carboniferous–Permian. The fluids caused dolomitization, silicification, and haematite Authigenesis. Both red dolomitized serpentinite and relatively unaltered serpentinite were sampled at multiple localities. The unaltered serpentinite contains a poorly defined magnetization with westerly declinations that resides in magnetite and has a pole which plots well off the apparent polar wander path. Most specimens of the red dolomitized serpentinite contain a magnetization with southerly declinations and negative inclinations that resides in haematite. A regional fold test suggests that this magnetization post-dates tilting and the pole positions for the different locations fall on the Carboniferous to Permian part of the apparent polar wander path. In some specimens of red dolomitized serpentinite, alternating field (AF) demagnetization prior to thermal treatment removes a component with a similar direction. Dolomitized basement rocks along the fault contain a similar although apparently slightly older magnetization. Fluid inclusion and geochemical studies indicate that the fluids were hydrothermal in origin (110–240°C) and had a range of sources. The Carboniferous–Permian magnetization in haematite is interpreted as a chemical remanent magnetization that formed when warm fluids moved along the fault zone and caused haematite Authigenesis. The component removed by AF treatment is interpreted as a thermal resetting of primary magnetite by the fluids. The variability of the palaeomagnetic, fluid inclusion, and stable isotope results suggests that there were probably multiple flow events that caused the alteration. The origin of the fluids could be related to the intrusion of late Carboniferous dikes in central Scotland and/or to reactivation of the HBF in the Carboniferous–Permian.
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Paleomagnetic dating of the smectite‐to‐illite conversion: Testing the hypothesis in Jurassic sedimentary rocks, Skye, Scotland
Journal of Geophysical Research, 2002Co-Authors: S Woods, R. D. Elmore, Michael H. EngelAbstract:[1] A hypothesized connection between clay diagenesis and magnetite Authigenesis is supported by the results of paleomagnetic, rock magnetic, geochemical, and petrographic studies on Jurassic sedimentary rock of Skye, Scotland. The results have implications for understanding remagnetization mechanisms and for the development of a paleomagnetic method to date clay diagenesis. Previous diagenetic studies indicate that rock in north Skye contains abundant detrital smectite, whereas the clays in the same age rock in south Skye have altered to illite because of Tertiary igneous activity. Geochemical (87Sr/86Sr, δ13C, δ18O) studies confirm that sedimentary rocks in south Skye are altered. The magnetization in the rocks in north Skye is weak and unstable. In contrast, the rocks in south Skye contain a multicomponent magnetization. At intermediate temperatures (225°–450°C) a magnetization with southerly declinations and negative inclinations or its antipodal equivalent is present. At higher temperatures (450°–580°C) a magnetization with northerly declinations and positive inclinations or its antipodal equivalent is removed. Both magnetizations have directions similar to Tertiary igneous rocks on Skye. Rock magnetic studies indicate the presence of pyrrhotite and magnetite. The intermediate-temperature component resides in pyrrhotite and/or magnetite and is interpreted as a thermoviscous remanent magnetization or a thermochemical remanent magnetization related to the heat and/or hydrothermal activity associated with the igneous activity. The high-temperature component resides in magnetite and is a chemical remanent magnetization (CRM). The presence-absence test and the timing of acquisition for this CRM suggest that magnetite Authigenesis is related to the smectite-to-illite conversion and that clay diagenesis is a viable remagnetization mechanism.
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Paleomagnetic dating of fluid-flow events in dolomitized Caledonian basement rocks, central Scotland
Journal of Geochemical Exploration, 2000Co-Authors: R. D. Elmore, J. Parnell, Michael H. Engel, S Woods, M Abraham, M. DavidsonAbstract:Abstract Paleomagnetic results suggest that there was a fluid-flow event which caused dolomitization and hematite Authigenesis in serpentinite within the Highland Border Group along the Highland Boundary Fault in central Scotland in the late Carboniferous/early Permian. Geochemical data indicate that the fluid was hydrothermal in origin, and in addition to causing hematite Authigenesis, the fluid also thermally remagnetized pre-existing magnetite in the serpentinite.
Andre Baldermann - One of the best experts on this subject based on the ideXlab platform.
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the role of fe on the formation and diagenesis of interstratified glauconite smectite and illite smectite a case study of upper cretaceous shallow water carbonates
Chemical Geology, 2017Co-Authors: Andre Baldermann, Florian Mittermayr, Martin Dietzel, Laurence N Warr, Vasileios Mavromatis, Klaus WemmerAbstract:Abstract The widespread formation of interstratified glauconite-smectite (Gl-S) and illite-smectite (I-S) in modern and ancient diagenetic settings records the physicochemical conditions prevailing during clay mineral Authigenesis. To date, however, significant gaps in our knowledge persist in respect to the influence of interstitial solution chemistry, temperature and reaction kinetics on the evolution of composition, mineralogy and microstructure of Gl-S and I-S. Herein, we present a study on the reaction mechanisms and the physicochemical conditions that led to the precipitation of early diagenetic Gl-S and late diagenetic I-S on a stable carbonate platform during the Cenomanian at Langenstein in the Northern German Basin. The texture and the K-Ar age (95.0 ± 1.8 Ma) of the green glauconitized grains revealed that green-clay Authigenesis progressed in initially organic-rich, semi-confined micromilieus, i.e., in fecal pellets and in foraminifera, close to the sediment-seawater interface. The composition of Gl-S varied in the range (K + 0.20–0.74 Na + 0–0.10 Ca 2 + 0–0.05 ) 0.28–0.75 (Fe 3 + 0.63–1.20 Fe 2 + 0.08–0.24 Al 3 + 0.19–0.97 Mg 2 + 0.29–0.52 ) 2.01–2.12 [Al 3 + 0.09–0.35 Si 4 + 3.65–3.91 O 10 ](OH 2 ), and depended on the rate of aqueous Fe 2 + and K + ion diffusion, the micromilieu of glauconitization and on the bulk sedimentation rate. The mineralogical, microstructural and chemical changes of the ongoing Gl-S products revealed the following reaction for green-clay Authigenesis at Langenstein: Fe(III)-smectite reacted with monosilicic acid, goethite and aqueous K + , Mg 2 + and Fe 2 + to form glauconite and aqueous Na + , Ca 2 + and H + ions. This process considers complex mineral transformations commonly associated with glauconitization, such as early diagenetic oxidation of organic matter and microbial-catalyzed dissolution of Fe-(oxy)hydroxides, carbonates and detrital silicates. In contrast, the K-Ar age of I-S (68.0 ± 1.6 Ma) and its compositional variability, (K + 0.29–0.45 Na + 0–0.10 Ca 2 + 0–0.06 ) 0.30–0.55 (Fe 3 + 0.16–0.29 Fe 2 + 0–0.10 Al 3 + 1.37–1.68 Mg 2 + 0.18–0.43 ) 2.00–2.12 [Al 3 + 0.17–0.39 Si 4 + 3.61–3.83 O 10 ](OH 2 ), indicate a burial diagenetic origin for this mineral phase, rather than transformation of illitic clays into I-S during weathering under warm and humid climatic conditions. The results from kinetic modelling support a diagenetic origin of I-S (50–60%I layers and 50–40%S layers) and imply its formation by the replacement of pre-existing K-feldspar at high pore-fluid activity K/Na ratios and at low Fe 2 + concentrations. We propose that the substitution of Al 3 + for Fe 3 + , Fe 2 + and Mg 2 + in the octahedral sheet shifts the stability field of the kaolinite–Fe-Al-Mg-smectite–Fe-Al-Mg-illite (or glauconite) triple point to much lower monosilicic acid activities, and stabilizes the I-S (or Gl-S) structure. This reaction supports the idea that the (bio)availability of Fe is the rate-limiting factor for glauconitization, which is not the case for the diagenetic growth of I-S, whereby the pore water Fe 2 + concentration may be limited by the competing formation of Fe-(oxy)hydroxides and/or Fe-sulfides.
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substantial iron sequestration during green clay Authigenesis in modern deep sea sediments
Nature Geoscience, 2015Co-Authors: Andre Baldermann, Laurence N Warr, Ilse Letofskypapst, Vasileios MavromatisAbstract:Pyrite formation has been considered a key iron sink in organic-rich marine sediments. Analyses of sediments from the Ivory Coast–Ghana Marginal Ridge demonstrate that iron can be buried at greater rates during green-clay formation.
