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Santanu Banerjee - One of the best experts on this subject based on the ideXlab platform.
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Glauconite authigenesis during the onset of the paleocene eocene thermal maximum a case study from the khuiala formation in jaisalmer basin india
Palaeogeography Palaeoclimatology Palaeoecology, 2021Co-Authors: Tathagata Roy Choudhury, Pratul Kumar Saraswati, Santanu Banerjee, Sonal Khanolkar, Sher Singh MeenaAbstract:Abstract Biological and ecological changes across the Paleogene hyperthermal events were accompanied by dramatic shifts in sedimentation systems in both marine and continental environments. This study investigates the formation of authigenic Glauconite within a biostratigraphically constrained section encompassing the Paleocene-Eocene Thermal Maximum (PETM). Paleogene transgressive shelf deposits in the Jaisalmer Basin in western India are represented by the Khuiala Formation, consisting of grey shale, limestone, and glauconitic shale. Foraminiferal assemblage not only constrains the age of the glauconitic shale to planktic zone E1 but also indicates the deposition of sediments in an oxygen-depleted mid-shelf environment. A detailed geochemical and mineralogical characterization of the authigenic Glauconite within the mid-shelf deposits reveals the highest Glauconite content within the maximum flooding zone, immediately below the negative carbon isotope excursion representing the PETM, followed by its steady decrease. The geochemical signature of the Glauconite is unusual for its high Al2O3 and MgO and medium Fe2O3 and SiO2 contents. The K2O content suggests the ‘evolved’ nature of the Glauconite, which is confirmed by the X-ray diffractional parameters and the presence of the ‘rosette’ texture in FEG-SEM images. The Glauconite evolved by Al-for-Fe substitution in the octahedral site and subsequent fixation of K+ into the interlayer sites. The high alumina content of the Glauconite corresponds to the high Al3+ in the tetrahedral layer, inherited from an aluminous substrate. Mossbauer spectroscopy suggests the dominance of Fe3+ compared to Fe2+ in the octahedral site of Glauconite pellets. The unusual variety of Glauconite formed by the transformation of continent-derived kaolinite and iron oxide in oxygen-depleted porewater conditions. Glauconite authigenesis in the Khuiala Formation is strongly influenced by the warm climatic condition, oxygen-depletion in the mid-shelf environment, and sharp marine transgression promoting sediment starvation associated with the PETM.
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unusual seawater composition of the late cretaceous tethys imprinted in Glauconite of narmada basin central india
Geological Magazine, 2020Co-Authors: Udita Bansal, Kanchan Pande, Santanu Banerjee, Dhiren K RuidasAbstract:A detailed investigation of a Glauconite bed within the Late Cretaceous Bryozoan Limestone Formation of the Bagh Group in central India, as well as the study of existing records, reveals the existence of a ‘glauconitic sea’ along the margins of the Palaeo-Tethys Ocean during the Late Cretaceous Epoch. The authigenic green mineral formed abundantly on shallow seafloors unlike in its modern, deep-sea counterpart. We present an integrated petrographical, geochemical and mineralogical investigation of the Glauconite within Late Cretaceous transgressive deposits to highlight its unique geochemistry with moderate Fe2O3 and high Al2O3, SiO2, MgO as well as K2O contents. X-ray diffractional parameters identify the ‘evolved to high evolved’ nature of the Glauconite while Mossbauer spectroscopic study reveals the dominance of Fe3+ compared to Fe2+ in the atomic structure. The rare earth elements (REE) pattern of Glauconite reveals moderate light-REE/heavy-REE (LREE/HREE) fractionation and weak negative Eu anomaly. The Ce anomaly of the Glauconite indicates a sub-oxic diagenetic condition. We propose that Late Cretaceous Glauconites formed within a shallow marine depositional setting across the Tethyan belt because of enhanced supply of K, Si, Al, Fe, Mg cations through continental weathering under the extant greenhouse climate.
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origin and sequence stratigraphic implications of high alumina Glauconite within the lower quartzite vindhyan supergroup
Marine and Petroleum Geology, 2020Co-Authors: Sabyasachi Mandal, Santanu Banerjee, S Sarkar, Indrani Mondal, Tathagata Roy ChoudhuryAbstract:Abstract An integrated field, petrographical and geochemical investigation reveals a shallow marine dys-oxic depositional setting for the Glauconite at the top of the Mesoproterozoic Lower Quartzite Member of the Vindhyan Supergroup. A thorough facies and paleogeographic analysis indicates a storm-influenced, shallow subtidal depositional condition for the glauconitic sandstone, occupying the mid-level of a transgressive systems tract (TST) deposit, which is capped by the maximum flooding zone (MFZ). The X-ray diffractional parameters confirm the evolved character of the Glauconite. The mineral chemical analysis indicates the Glauconite is enriched in K2O, MgO and Al2O3 and depleted in Fe2O3(total), compared to the Phanerozoic variety. It formed by the pseudomorphic replacement of the K-feldspar, by the addition of Fe2O3 at consistently high content of K2O, unlike most Phanerozoic examples. The elevated level of H3SiO4, Cl, K, Na, Mg and Fe, possibly derived by the continental weathering and/or contemporary volcanism, facilitated the glauconitization process. The high content of Mg in the Glauconite corresponds to the Mg-rich, Mesoproterozoic seawater. A dys-oxic depositional condition, associated with a major marine flooding surface, favoured the formation of Glauconite. While the onset of anoxic regime caused the disappearance of Glauconite and the deposition of pyritiferous and carbonaceous shale in the overlying condensed zone deposits.
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is the rarity of Glauconite in precambrian bhima basin in india related to its chloritization
Precambrian Research, 2020Co-Authors: Udita Bansal, Santanu Banerjee, R NagendraAbstract:Abstract An integrated textural, mineralogical and chemical investigation reveals the origin of authigenic Glauconite within the Mesoproterozoic Rabanpalli Formation in the Bhima Basin and its subsequent alteration to chlorite. Glauconite forms within the transgressive shallow shelf deposits in the Rabanpalli Formation. It primarily occurs in two modes, as thoroughly replaced form of detrital grains, and as altered zones along cleavages and fractures of quartz, K-feldspar and mica. All varieties of Glauconites exhibit high contents of K2O. The Fe2O3 (T) content is highest in Glauconite formed within mica, while it is least in Glauconite formed by the replacement of feldspars. Pseudomorphic replacement of substrates by Glauconite best explains the origin of Glauconite in the Rabanpalli Formation. Diagenetic chlorite, mostly occurring as thick rims on grains and along the grain margin fractures replaces Glauconite. Chloritization predominantly takes place in the Glauconite variety forming within the mica. The mineral chemistry of chlorite is characterized by high MgO and Fe2O3 (T). Chloritization involves the simultaneous removal of Fe, Mg and Si from the Glauconite structure to form brucite type sheets. The high contents of Fe2O3 (T) and MgO, reducing porewater and the high thermal maturation of sediments facilitate the formation of chlorite within the Rabanpalli Formation. This study, therefore, indicates that the rarity of Glauconite in the Precambrian is related to its alteration to chlorite.
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application of visible and infrared spectroscopy for the evaluation of evolved Glauconite
International Journal of Applied Earth Observation and Geoinformation, 2018Co-Authors: Shovan Lal Chattoraj, Santanu Banerjee, Freek D Van Der Meer, P Champati K RayAbstract:Abstract The Oligocene Maniyara Fort Formation in western India exhibits two distinct Glauconite types with different maturation states, which are characterized by their spectral response in the visible to infrared spectrum of electromagnetic radiation. Spectral signatures of Maniyara Fort Glauconites display absorption features at approximately 0.77, 1.08, 1.9, 2.3 μm in the visible-short-wave infrared (SWIR) and 2.8 and 10 μm in the mid-infrared (MIR) region which vary with K2O content of Glauconite. The spectra of Glauconite varies significantly as a function of its cationic contents and substitution in different sites. The maturity is found to increase in tandem with the metal–metal charge transfer (CT) and the Fe2+ dd absorption band respectively at 1.08 and 0.77 μm. H2O and OH− signatures at the NIR region reflect differences in the sensitivity of Glauconites with different molecular H2O content. In the MIR region, a gradual shift of the Si O stretch at 10 μm towards lower wavelengths indicates the dominance of smectite layers in Glauconites. This study demonstrates a strong correlation between the proportion of expandable layers in the Glauconite structure with variations in characteristic band position, depth and symmetry in reflectance and emissivity.
Sher Singh Meena - One of the best experts on this subject based on the ideXlab platform.
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Glauconite authigenesis during the onset of the paleocene eocene thermal maximum a case study from the khuiala formation in jaisalmer basin india
Palaeogeography Palaeoclimatology Palaeoecology, 2021Co-Authors: Tathagata Roy Choudhury, Pratul Kumar Saraswati, Santanu Banerjee, Sonal Khanolkar, Sher Singh MeenaAbstract:Abstract Biological and ecological changes across the Paleogene hyperthermal events were accompanied by dramatic shifts in sedimentation systems in both marine and continental environments. This study investigates the formation of authigenic Glauconite within a biostratigraphically constrained section encompassing the Paleocene-Eocene Thermal Maximum (PETM). Paleogene transgressive shelf deposits in the Jaisalmer Basin in western India are represented by the Khuiala Formation, consisting of grey shale, limestone, and glauconitic shale. Foraminiferal assemblage not only constrains the age of the glauconitic shale to planktic zone E1 but also indicates the deposition of sediments in an oxygen-depleted mid-shelf environment. A detailed geochemical and mineralogical characterization of the authigenic Glauconite within the mid-shelf deposits reveals the highest Glauconite content within the maximum flooding zone, immediately below the negative carbon isotope excursion representing the PETM, followed by its steady decrease. The geochemical signature of the Glauconite is unusual for its high Al2O3 and MgO and medium Fe2O3 and SiO2 contents. The K2O content suggests the ‘evolved’ nature of the Glauconite, which is confirmed by the X-ray diffractional parameters and the presence of the ‘rosette’ texture in FEG-SEM images. The Glauconite evolved by Al-for-Fe substitution in the octahedral site and subsequent fixation of K+ into the interlayer sites. The high alumina content of the Glauconite corresponds to the high Al3+ in the tetrahedral layer, inherited from an aluminous substrate. Mossbauer spectroscopy suggests the dominance of Fe3+ compared to Fe2+ in the octahedral site of Glauconite pellets. The unusual variety of Glauconite formed by the transformation of continent-derived kaolinite and iron oxide in oxygen-depleted porewater conditions. Glauconite authigenesis in the Khuiala Formation is strongly influenced by the warm climatic condition, oxygen-depletion in the mid-shelf environment, and sharp marine transgression promoting sediment starvation associated with the PETM.
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the distinctive compositional evolution of Glauconite in the cretaceous ukra hill member kutch basin india and its implications
Marine and Petroleum Geology, 2017Co-Authors: Udita Bansal, Kanchan Pande, Santanu Banerjee, Ashwin Arora, Sher Singh MeenaAbstract:Abstract An integrated study involving sedimentology, mineral chemistry and spectroscopy highlights a distinctive compositional evolution of Cretaceous Glauconite within the Ukra Hill Member. Glauconite occurs at the top part of transgressive systems tract deposits built on a marine shelf. The concentration of Glauconite steadily increases towards the maximum flooding surface, maximizing around 50%, and sharply falls at the onset of progradation. Unlike most Phanerozoic examples, Ukra Glauconite forms by the variable degree of replacement of quartz, feldspar and mica grains. XRD, FEG-SEM and spectroscopy of Glauconite pellets indicate an ‘evolved’ stage of maturation. Mossbauer spectroscopy reflects a minor substitution of Al3+-Fe3+ (total) in tetrahedral sites and significant substitution of the same in octahedral sites. A consistently high value of K2O as well as Fe2O3 contradicts the two popular theories, ‘layer lattice’ and ‘verdissement’, and support replacement origin of Glauconite in a high aSi+ and high aK+ pore water environment. Incipiently formed Glauconite records a marginal increase in K2O content accompanied by release of Al2O3 and SiO2 to form evolved Glauconite pellets; those forming within quartz grains involve an addition of Fe2O3 (total) content during maturation. The minimal increase in K2O content of incipiently formed Glauconite, best exhibited by those formed within quartz grains is possibly related to stratigraphic condensation. Compositional evolution like this is exhibited by Precambrian Glauconites involving abiotic substrates, but is unusual for the Phanerozoic. Original K2O and Fe2O3 (total) content of Glauconites is reduced around peripheries and fractures during diagenesis, adding to compositional variability.
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compositional variability of Glauconites within the upper cretaceous karai shale formation cauvery basin india implications for evaluation of stratigraphic condensation
Sedimentary Geology, 2016Co-Authors: Santanu Banerjee, Udita Bansal, Kanchan Pande, Sher Singh MeenaAbstract:Abstract A detailed mineral chemical investigation of Glauconite within the condensed section deposits of the Cretaceous Karai Shale Formation, Cauvery Basin, India reflects a wide spectrum in chemical composition related to origin and evolution in different substrates, stratigraphic condensation, and post-depositional alteration. Fe- and Mg-rich Glauconite, comprising up to 60% of the sedimentary rocks, occurs as replaced forms of fecal pellets, as infillings within pores and chambers of bioclasts including those of foraminifera, ostracoda, bryozoa, and algae, and as altered forms of mica exhibiting vermiforms. Authigenic precipitation of K- and Fe-poor Glauconite, followed by addition of Fe and K into the lattice and concomitant release of Al and Si explains the origin of Glauconite pellets and infillings; the origin of Glauconite vermiforms in partly degraded mica involves only the second stage of Fe and K addition. Glauconite pellets and vermiforms exhibit sharply defined alteration zones along peripheries to form rims, and in proximity to cracks or cleavages with reduced K2O and Fe2O3 (total) and enhanced Al2O3 and SiO2, related to late-stage meteoric water actions. Cores of Glauconite pellets and unaltered zones of vermiforms reflect ‘evolved’ characteristics with > 6% K2O, typical of a condensed section, while other Glauconite varieties occurring at the same stratigraphic level exhibit ‘slightly evolved’ nature, not consonant with stratigraphic condensation. Increasing abundance of Glauconite pellets from the bottom to the top of the transgressive systems tract, accompanied by slight increase in K2O within their cores, reflects the effect of stratigraphic condensation on the evolution of Glauconite. High Fe2O3 (total) content of Glauconite in the Karai Shale Formation may be related to upwelling, although the Fe may be contributed partly by the biotite substrate. Mossbauer spectroscopy of Glauconites reveals significant total Fe substitution in both tetrahedral and octahedral sites. Detailed mineral chemical analysis enables us to distinguish stratigraphically significant Glauconite within the Karai Shale Formation from the rest of the Glauconite notwithstanding its wide compositional range.
Udita Bansal - One of the best experts on this subject based on the ideXlab platform.
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unusual seawater composition of the late cretaceous tethys imprinted in Glauconite of narmada basin central india
Geological Magazine, 2020Co-Authors: Udita Bansal, Kanchan Pande, Santanu Banerjee, Dhiren K RuidasAbstract:A detailed investigation of a Glauconite bed within the Late Cretaceous Bryozoan Limestone Formation of the Bagh Group in central India, as well as the study of existing records, reveals the existence of a ‘glauconitic sea’ along the margins of the Palaeo-Tethys Ocean during the Late Cretaceous Epoch. The authigenic green mineral formed abundantly on shallow seafloors unlike in its modern, deep-sea counterpart. We present an integrated petrographical, geochemical and mineralogical investigation of the Glauconite within Late Cretaceous transgressive deposits to highlight its unique geochemistry with moderate Fe2O3 and high Al2O3, SiO2, MgO as well as K2O contents. X-ray diffractional parameters identify the ‘evolved to high evolved’ nature of the Glauconite while Mossbauer spectroscopic study reveals the dominance of Fe3+ compared to Fe2+ in the atomic structure. The rare earth elements (REE) pattern of Glauconite reveals moderate light-REE/heavy-REE (LREE/HREE) fractionation and weak negative Eu anomaly. The Ce anomaly of the Glauconite indicates a sub-oxic diagenetic condition. We propose that Late Cretaceous Glauconites formed within a shallow marine depositional setting across the Tethyan belt because of enhanced supply of K, Si, Al, Fe, Mg cations through continental weathering under the extant greenhouse climate.
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is the rarity of Glauconite in precambrian bhima basin in india related to its chloritization
Precambrian Research, 2020Co-Authors: Udita Bansal, Santanu Banerjee, R NagendraAbstract:Abstract An integrated textural, mineralogical and chemical investigation reveals the origin of authigenic Glauconite within the Mesoproterozoic Rabanpalli Formation in the Bhima Basin and its subsequent alteration to chlorite. Glauconite forms within the transgressive shallow shelf deposits in the Rabanpalli Formation. It primarily occurs in two modes, as thoroughly replaced form of detrital grains, and as altered zones along cleavages and fractures of quartz, K-feldspar and mica. All varieties of Glauconites exhibit high contents of K2O. The Fe2O3 (T) content is highest in Glauconite formed within mica, while it is least in Glauconite formed by the replacement of feldspars. Pseudomorphic replacement of substrates by Glauconite best explains the origin of Glauconite in the Rabanpalli Formation. Diagenetic chlorite, mostly occurring as thick rims on grains and along the grain margin fractures replaces Glauconite. Chloritization predominantly takes place in the Glauconite variety forming within the mica. The mineral chemistry of chlorite is characterized by high MgO and Fe2O3 (T). Chloritization involves the simultaneous removal of Fe, Mg and Si from the Glauconite structure to form brucite type sheets. The high contents of Fe2O3 (T) and MgO, reducing porewater and the high thermal maturation of sediments facilitate the formation of chlorite within the Rabanpalli Formation. This study, therefore, indicates that the rarity of Glauconite in the Precambrian is related to its alteration to chlorite.
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the distinctive compositional evolution of Glauconite in the cretaceous ukra hill member kutch basin india and its implications
Marine and Petroleum Geology, 2017Co-Authors: Udita Bansal, Kanchan Pande, Santanu Banerjee, Ashwin Arora, Sher Singh MeenaAbstract:Abstract An integrated study involving sedimentology, mineral chemistry and spectroscopy highlights a distinctive compositional evolution of Cretaceous Glauconite within the Ukra Hill Member. Glauconite occurs at the top part of transgressive systems tract deposits built on a marine shelf. The concentration of Glauconite steadily increases towards the maximum flooding surface, maximizing around 50%, and sharply falls at the onset of progradation. Unlike most Phanerozoic examples, Ukra Glauconite forms by the variable degree of replacement of quartz, feldspar and mica grains. XRD, FEG-SEM and spectroscopy of Glauconite pellets indicate an ‘evolved’ stage of maturation. Mossbauer spectroscopy reflects a minor substitution of Al3+-Fe3+ (total) in tetrahedral sites and significant substitution of the same in octahedral sites. A consistently high value of K2O as well as Fe2O3 contradicts the two popular theories, ‘layer lattice’ and ‘verdissement’, and support replacement origin of Glauconite in a high aSi+ and high aK+ pore water environment. Incipiently formed Glauconite records a marginal increase in K2O content accompanied by release of Al2O3 and SiO2 to form evolved Glauconite pellets; those forming within quartz grains involve an addition of Fe2O3 (total) content during maturation. The minimal increase in K2O content of incipiently formed Glauconite, best exhibited by those formed within quartz grains is possibly related to stratigraphic condensation. Compositional evolution like this is exhibited by Precambrian Glauconites involving abiotic substrates, but is unusual for the Phanerozoic. Original K2O and Fe2O3 (total) content of Glauconites is reduced around peripheries and fractures during diagenesis, adding to compositional variability.
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origin depositional setting and stratigraphic implications of palaeogene Glauconite of kutch
Recent Studies on the Geology of Kachchh, 2016Co-Authors: Shovan Lal Chattoraj, Santanu Banerjee, Pratul Kumar Saraswati, Udita BansalAbstract:A combined sedimentological, stratigraphical, mineralogical and geochemical investigation on Palaeogene Glauconites of Kutch address some of the crucial issues related to origin of Glauconite and its depositional and stratigraphic significance. Glauconite occurs within fossiliferous green shale units of Naredi, Harudi and Maniyara Fort Formation. It occurs primarily in two modes, either as an altered form of fecal pellets or as infillings within the bioclasts. The origin of Glauconite may be best explained by direct precipitation of Fe-rich glauconitic smectite within the pores of bioclasts and fecal pellets followed by its maturation to glauconitic mica by the addition of K. Fecal pellet is a more favourable substrate than bioclasts for glauconitization because of easy percolation of pore water within and availability of relevant ions in pellets. Strong biostratigraphic control allows us to clearly establish that relatively high rate of sedimentation (>27 m/Ma) discourage Glauconite formation in the Fulra limestone while low rate of sedimentation rate (<5m /Ma) allowed its formation. Occurrence of Glauconite exclusively within the transgressive systems tracts and its absence within the highstand systems tracts corroborates the requirement of low rate of sedimentation. Formation of mature Glauconite in shallow marine open as well as in protected lagoon suggests that Glauconite may be a poor indicator of depositional environment, despite the fact that it forms in modern deep marine conditions. However, positive Ce-anomaly in all Glauconites suggests that dys-oxic depositional setting encourages Glauconite formation. Absence of Glauconite within the unfossiliferous and emerged red shales, immediately overlying and underlying the glauconitic green shales suggest that oxic condition discourages Glauconite formation.
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compositional variability of Glauconites within the upper cretaceous karai shale formation cauvery basin india implications for evaluation of stratigraphic condensation
Sedimentary Geology, 2016Co-Authors: Santanu Banerjee, Udita Bansal, Kanchan Pande, Sher Singh MeenaAbstract:Abstract A detailed mineral chemical investigation of Glauconite within the condensed section deposits of the Cretaceous Karai Shale Formation, Cauvery Basin, India reflects a wide spectrum in chemical composition related to origin and evolution in different substrates, stratigraphic condensation, and post-depositional alteration. Fe- and Mg-rich Glauconite, comprising up to 60% of the sedimentary rocks, occurs as replaced forms of fecal pellets, as infillings within pores and chambers of bioclasts including those of foraminifera, ostracoda, bryozoa, and algae, and as altered forms of mica exhibiting vermiforms. Authigenic precipitation of K- and Fe-poor Glauconite, followed by addition of Fe and K into the lattice and concomitant release of Al and Si explains the origin of Glauconite pellets and infillings; the origin of Glauconite vermiforms in partly degraded mica involves only the second stage of Fe and K addition. Glauconite pellets and vermiforms exhibit sharply defined alteration zones along peripheries to form rims, and in proximity to cracks or cleavages with reduced K2O and Fe2O3 (total) and enhanced Al2O3 and SiO2, related to late-stage meteoric water actions. Cores of Glauconite pellets and unaltered zones of vermiforms reflect ‘evolved’ characteristics with > 6% K2O, typical of a condensed section, while other Glauconite varieties occurring at the same stratigraphic level exhibit ‘slightly evolved’ nature, not consonant with stratigraphic condensation. Increasing abundance of Glauconite pellets from the bottom to the top of the transgressive systems tract, accompanied by slight increase in K2O within their cores, reflects the effect of stratigraphic condensation on the evolution of Glauconite. High Fe2O3 (total) content of Glauconite in the Karai Shale Formation may be related to upwelling, although the Fe may be contributed partly by the biotite substrate. Mossbauer spectroscopy of Glauconites reveals significant total Fe substitution in both tetrahedral and octahedral sites. Detailed mineral chemical analysis enables us to distinguish stratigraphically significant Glauconite within the Karai Shale Formation from the rest of the Glauconite notwithstanding its wide compositional range.
Kanchan Pande - One of the best experts on this subject based on the ideXlab platform.
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unusual seawater composition of the late cretaceous tethys imprinted in Glauconite of narmada basin central india
Geological Magazine, 2020Co-Authors: Udita Bansal, Kanchan Pande, Santanu Banerjee, Dhiren K RuidasAbstract:A detailed investigation of a Glauconite bed within the Late Cretaceous Bryozoan Limestone Formation of the Bagh Group in central India, as well as the study of existing records, reveals the existence of a ‘glauconitic sea’ along the margins of the Palaeo-Tethys Ocean during the Late Cretaceous Epoch. The authigenic green mineral formed abundantly on shallow seafloors unlike in its modern, deep-sea counterpart. We present an integrated petrographical, geochemical and mineralogical investigation of the Glauconite within Late Cretaceous transgressive deposits to highlight its unique geochemistry with moderate Fe2O3 and high Al2O3, SiO2, MgO as well as K2O contents. X-ray diffractional parameters identify the ‘evolved to high evolved’ nature of the Glauconite while Mossbauer spectroscopic study reveals the dominance of Fe3+ compared to Fe2+ in the atomic structure. The rare earth elements (REE) pattern of Glauconite reveals moderate light-REE/heavy-REE (LREE/HREE) fractionation and weak negative Eu anomaly. The Ce anomaly of the Glauconite indicates a sub-oxic diagenetic condition. We propose that Late Cretaceous Glauconites formed within a shallow marine depositional setting across the Tethyan belt because of enhanced supply of K, Si, Al, Fe, Mg cations through continental weathering under the extant greenhouse climate.
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the distinctive compositional evolution of Glauconite in the cretaceous ukra hill member kutch basin india and its implications
Marine and Petroleum Geology, 2017Co-Authors: Udita Bansal, Kanchan Pande, Santanu Banerjee, Ashwin Arora, Sher Singh MeenaAbstract:Abstract An integrated study involving sedimentology, mineral chemistry and spectroscopy highlights a distinctive compositional evolution of Cretaceous Glauconite within the Ukra Hill Member. Glauconite occurs at the top part of transgressive systems tract deposits built on a marine shelf. The concentration of Glauconite steadily increases towards the maximum flooding surface, maximizing around 50%, and sharply falls at the onset of progradation. Unlike most Phanerozoic examples, Ukra Glauconite forms by the variable degree of replacement of quartz, feldspar and mica grains. XRD, FEG-SEM and spectroscopy of Glauconite pellets indicate an ‘evolved’ stage of maturation. Mossbauer spectroscopy reflects a minor substitution of Al3+-Fe3+ (total) in tetrahedral sites and significant substitution of the same in octahedral sites. A consistently high value of K2O as well as Fe2O3 contradicts the two popular theories, ‘layer lattice’ and ‘verdissement’, and support replacement origin of Glauconite in a high aSi+ and high aK+ pore water environment. Incipiently formed Glauconite records a marginal increase in K2O content accompanied by release of Al2O3 and SiO2 to form evolved Glauconite pellets; those forming within quartz grains involve an addition of Fe2O3 (total) content during maturation. The minimal increase in K2O content of incipiently formed Glauconite, best exhibited by those formed within quartz grains is possibly related to stratigraphic condensation. Compositional evolution like this is exhibited by Precambrian Glauconites involving abiotic substrates, but is unusual for the Phanerozoic. Original K2O and Fe2O3 (total) content of Glauconites is reduced around peripheries and fractures during diagenesis, adding to compositional variability.
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compositional variability of Glauconites within the upper cretaceous karai shale formation cauvery basin india implications for evaluation of stratigraphic condensation
Sedimentary Geology, 2016Co-Authors: Santanu Banerjee, Udita Bansal, Kanchan Pande, Sher Singh MeenaAbstract:Abstract A detailed mineral chemical investigation of Glauconite within the condensed section deposits of the Cretaceous Karai Shale Formation, Cauvery Basin, India reflects a wide spectrum in chemical composition related to origin and evolution in different substrates, stratigraphic condensation, and post-depositional alteration. Fe- and Mg-rich Glauconite, comprising up to 60% of the sedimentary rocks, occurs as replaced forms of fecal pellets, as infillings within pores and chambers of bioclasts including those of foraminifera, ostracoda, bryozoa, and algae, and as altered forms of mica exhibiting vermiforms. Authigenic precipitation of K- and Fe-poor Glauconite, followed by addition of Fe and K into the lattice and concomitant release of Al and Si explains the origin of Glauconite pellets and infillings; the origin of Glauconite vermiforms in partly degraded mica involves only the second stage of Fe and K addition. Glauconite pellets and vermiforms exhibit sharply defined alteration zones along peripheries to form rims, and in proximity to cracks or cleavages with reduced K2O and Fe2O3 (total) and enhanced Al2O3 and SiO2, related to late-stage meteoric water actions. Cores of Glauconite pellets and unaltered zones of vermiforms reflect ‘evolved’ characteristics with > 6% K2O, typical of a condensed section, while other Glauconite varieties occurring at the same stratigraphic level exhibit ‘slightly evolved’ nature, not consonant with stratigraphic condensation. Increasing abundance of Glauconite pellets from the bottom to the top of the transgressive systems tract, accompanied by slight increase in K2O within their cores, reflects the effect of stratigraphic condensation on the evolution of Glauconite. High Fe2O3 (total) content of Glauconite in the Karai Shale Formation may be related to upwelling, although the Fe may be contributed partly by the biotite substrate. Mossbauer spectroscopy of Glauconites reveals significant total Fe substitution in both tetrahedral and octahedral sites. Detailed mineral chemical analysis enables us to distinguish stratigraphically significant Glauconite within the Karai Shale Formation from the rest of the Glauconite notwithstanding its wide compositional range.
Hansmartin Schulz - One of the best experts on this subject based on the ideXlab platform.
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berthierine formation in reservoir rocks from the siri oilfield danish north sea as result of fluid rock interactions part iii determining mineral stability and co2 sequestering capacity of glauconitic sandstones
Marine and Petroleum Geology, 2015Co-Authors: Wolfgang Van Berk, Hansmartin SchulzAbstract:Abstract Berthierine was proven as one of the most important products of Glauconite alteration in the Siri oilfield (Danish North Sea). However, there is an ongoing debate regarding the main product of Glauconite dissolution: siderite, berthierine, or berthierine as a precursor of siderite and/or magnesium-bearing carbonate. In order to investigate the consequences of Glauconite dissolution in view of thermodynamic admissibility and the resulting CO2-sequestering capacity, a hydrogeochemical model, which is based on thermodynamics of chemical equilibrium, was developed. Calculating various modeling scenarios helps to conclude on the pH-EH conditions of Glauconite dissolution as well as of berthierine formation and dissolution in generic, aqueous systems under elevated temperature-pressure conditions. Our modeling results highlight that carbonate formation cannot be triggered exclusively by CO2 addition into glauconitic sandstones. The injection of pure CO2 into glauconitic sandstones leads to acidic and anoxic oxidizing conditions under which Glauconite remains stable. To intensify Glauconite alteration by CO2 injection, glauconitic sandstones have to be in contact with degradable organic matter, or, alternatively, reducing agents have to be co-injected with CO2. Sufficient electron transfer to ferric iron bound in Glauconite is the ultimate control for intense Glauconite alteration and for subsequent berthierine precipitation. Once formed, berthierine remains stable over a broad pH range and is not transformed to any carbonate under reducing conditions. Thus, CO2 injection into glauconitic sandstones under reducing conditions mainly leads to formation of berthierine instead of iron- and magnesium-carbonates. However, hydrogeochemical conditions in the subsurface can affect CO2 sequestration via Glauconite dissolution and the resulting carbonate formation, including the pH-EH conditions, the chemical composition of Glauconite, and the overall mineralogical composition of glauconitic sandstones.
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berthierine formation in reservoir rocks from the siri oilfield danish north sea as result of fluid rock interactions part i characterization
Marine and Petroleum Geology, 2015Co-Authors: Hansmartin Schulz, Niels H Schovsbo, Richard Wirth, Dieter Rhede, Wolfgang Van BerkAbstract:Abstract Berthierine as the only authigenic Fe-rich clay mineral occurs in an oil-bearing, Glauconite-rich sandstone (Paleocene Heimdal Member of the Lista Formation, Danish North Sea). Based on the results of thin section, transmission and scanning electron microscopy, five different morphological types of berthierine were identified: (1) mainly as grain-coatings partly together with authigenic quartz covering detrital grains, (2) as pore-filling clay in open pores, (3) small crystals in transformed Glauconite grains, (4) small crystals associated with siderite in layers of mica/micaceous Glauconite, and (5) as elongated crystals in siderite concretions. Although different in occurrence, all berthierine types investigated by microprobe analysis are of similar chemical composition, suggesting similar precipitation conditions. Investigations by transmission electron microscopy reveal that fine berthierine crystals display straight parallel layers with a typical lattice fringe spacing of 0.7 nm, and that their occurrence is intimately connected to oil phases in pore space. Partly, berthierine textures resemble mineralized oil–water emulsions. Berthierine is more abundant in the oil leg than in the water leg, but occurs especially abundant at the oil–water contact. The coexistence of berthierine together with quartz overgrowth, but also its appearance in Glauconite indicates that berthierine formed in situ and that it is a product of Glauconite dissolution. Berthierine formation is coupled to the reduction of aqueous Fe 3+ into Fe 2+ derived from Glauconite dissolution, and is related to fluid–rock interactions triggered by oil degradation which occurred in the oil-filled zone and at the oil–water contact. The biomarker parameters pristane/ n -C 17 and phytane/ n -C 18 indicate an increased extent of oil degradation at the oil–water contact. On the one hand, soluble oil degradation products (methane, carbon dioxide, and hydrogen) changed the hydrogeochemical conditions (such as pH, pe, alkalinity, etc.), and controlled dissolution of Glauconite (and feldspar). On the other hand, the changed hydrogeochemical conditions led to berthierine and quartz precipitation in water-wet reservoir intervals.