Journal articles on the topic 'Authigenic clay'
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1
Pozo, Manuel, and José Calvo. "An Overview of Authigenic Magnesian Clays." Minerals 8, no. 11 (November 9, 2018): 520. http://dx.doi.org/10.3390/min8110520.
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Clay authigenesis mostly concerns: (a) the formation of clays by direct precipitation from solution, called “neoformation” and (b) development of clays by transformation of precursor minerals. Precipitation from solution implies that a new mineral structure crystallizes, so that a prior mineral structure is not inherited. Transformation of precursor detrital minerals, a process also termed “neoformation by addition”, can be conducted whether throughout precipitation on pre-existing natural surfaces or transformation and reaction on pre-existing surfaces. Both processes have been recognized as effective mechanisms in the formation of Mg-clays, which mostly include 2:1 clay minerals, such as talc-kerolite and Mg-smectites, as well as fibrous clays (sepiolite, palygorskite). Authigenic Mg-clay minerals occur in both modern and ancient marine and non-marine depositional environments, although formation of these clays in hydrothermal continental and seafloor settings must be also outlined. Most favourable conditions for the formation of Mg-clays on earth surface are found in evaporitic depositional environments, especially where parent rocks are enriched in ferromagnesian minerals. In these settings, Mg-clays are important constituent of weathering profiles and soils and can form thick deposits of significant economic interest. Based on this review of authigenic clay deposits, we propose three geochemical pathways, mainly related to continental environments, for the origin of authigenic Mg-clays: formation of Al-bearing Mg-clays (pathway 1), formation of Al-free Mg clays (pathway 2) and formation of sepiolite from other Mg-clay minerals (pathway 3).
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Setti, M., L. Marinoni, and A. López-Galindo. "Mineralogical and geochemical characteristics (major, minor, trace elements and REE) of detrital and authigenic clay minerals in a Cenozoic sequence from Ross Sea, Antarctica." Clay Minerals 39, no. 4 (December 2004): 405–21. http://dx.doi.org/10.1180/000985503540143.
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AbstractThe mineralogy and geochemistry of the clay fraction of Victoria Land Basin (Ross Sea, Antarctica) sediments was investigated, to determine the origin of clay minerals and the features of authigenic smectite. The investigated core (CRP-3) is ~800 m long, mostly of Oligocene age. The clay fraction of the upper sequence consists of mica, chlorite and detrital smectite, while that of the central and lower part is largely made up of authigenic smectite. Authigenic smectites are ditrioctahedral, with a composition close to saponite, while detrital smectites such as Al-Fe beidellites are dioctahedral. Authigenic smectites have no illite mixed layers, show a higher degree of crystallization, higher MgO, Fe2O3, V, Cr, Co, Ni and Sc contents and lower SiO2, Al2O3, K2O, TiO2, Ba, Rb and Zr contents with respect to detrital clay minerals, and a clear depletion of LREE with respect to HREE. Authigenic smectite formed from the alteration of volcanic materials and clay minerals.
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Baiyegunhi, Temitope Love, Kuiwu Liu, Oswald Gwavava, and Christopher Baiyegunhi. "Impact of Diagenesis on the Reservoir Properties of the Cretaceous Sandstones in the Southern Bredasdorp Basin, Offshore South Africa." Minerals 10, no. 9 (August 27, 2020): 757. http://dx.doi.org/10.3390/min10090757.
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The Cretaceous sandstone in the Bredasdorp Basin is an essential potential hydrocarbon reservoir. In spite of its importance as a reservoir, the impact of diagenesis on the reservoir quality of the sandstones is almost unknown. This study is undertaken to investigate the impact of digenesis on reservoir quality as it pertains to oil and gas production in the basin. The diagenetic characterization of the reservoir is based on XRF, XRD SEM + EDX, and petrographic studies of 106 thin sections of sandstones from exploration wells E-AH1, E-AJ1, E-BA1, E-BB1 and E-D3 in the basin. The main diagenetic processes that have affected the reservoir quality of the sandstones are cementation by authigenic clay, carbonate and silica, growth of authigenic glauconite, dissolution of minerals and load compaction. Based on the framework grain–cement relationships, precipitation of the early calcite cement was either accompanied or followed up by the development of partial pore-lining and pore-filling clay cements, particularly illite. This clay acts as pore choking cement, which reduces porosity and permeability of the reservoir rocks. The scattered plots of porosity and permeability versus cement + clays show good inverse correlations, suggesting that the reservoir quality is mainly controlled by cementation and authigenic clays.
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Bentz, Jennifer L., and Ronald C. Peterson. "Authigenic Phyllosilicates in Sand Layers from the Mudflats of Saline Lakes in the Northern Great Prairies, Saskatchewan." Canadian Mineralogist 60, no. 1 (December 6, 2021): 101–20. http://dx.doi.org/10.3749/canmin.1900065.
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ABSTRACT The mudflats of saline lakes are amenable to authigenic clay formation due to the high ionic strength of the solutions driven by evaporative concentration and due to the fluctuating wet/dry cycles. However, the mudflats of saline lakes have received relatively little study given the challenges in sampling unstable sediments coupled with post-depositional alterations that make direct relationships to the climate difficult. In an effort to gain a better understanding of the authigenic phyllosilicates present, the mudflats of 17 sulfate-rich saline lake basins across southern Saskatchewan were sampled. The <2 μm fraction was separated from the sediments and analyzed utilizing X-ray diffraction (XRD), scanning electron microscopy, bulk chemical analysis via digestion and inductively coupled optical emission spectroscopy, and visible and near-infrared reflectance spectroscopy. The mudflat sediments were characterized as highly variable and were classified based on particle size into sediment classes A (clay-rich), B (unsorted till), and C (sand). Despite the high variability in sorting and thickness of the sedimentary layers, the phyllosilicates were distinctive within each class independent of the basin. Phyllosilicates in sediment class A were characterized by well-crystalline dioctahedral (Al) clays similar to the surrounding soils with smectite > illite > kaolinite > chlorite. Phyllosilicates from sediment class B displayed highly variable characteristics ranging between classes A and C. Clays from sediment class C were dominated by illite with decreasing proportions of smectite, kaolinite, and chlorite. The illite in the sand lenses was poorly formed, with broad reflections in the XRD patterns indicative of small crystallite size or high disorder, which is consistent with an authigenic nature. The clays in class C were rich in iron (Fe) and magnesium (Mg) and displayed lath-like morphologies common with authigenic illite forming in sandy porous sediments. The sand lenses of mudflats represent viable targets for finding authigenic clay minerals in detrital-rich sediments to use in understanding past climates on Earth and Mars.
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Sallstedt, Therese, Magnus Ivarsson, Henrik Drake, and Henrik Skogby. "Instant Attraction: Clay Authigenesis in Fossil Fungal Biofilms." Geosciences 9, no. 9 (August 24, 2019): 369. http://dx.doi.org/10.3390/geosciences9090369.
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Clay authigenesis associated with the activity of microorganisms is an important process for biofilm preservation and may provide clues to the formation of biominerals on the ancient Earth. Fossilization of fungal biofilms attached to vesicles or cracks in igneous rock, is characterized by fungal-induced clay mineralization and can be tracked in deep rock and deep time, from late Paleoproterozoic (2.4 Ga), to the present. Here we briefly review the current data on clay mineralization by fossil fungal biofilms from oceanic and continental subsurface igneous rock. The aim of this study was to compare the nature of subsurface fungal clays from different igneous settings to evaluate the importance of host rock and ambient redox conditions for clay speciation related to fossil microorganisms. Our study suggests that the most common type of authigenic clay associated with pristine fossil fungal biofilms in both oxic (basaltic) and anoxic (granitic) settings are montmorillonite-like smectites and confirms a significant role of fungal biofilms in the cycling of elements between host rock, ocean and secondary precipitates. The presence of life in the deep subsurface may thus prove more significant than host rock geochemistry in directing the precipitation of authigenic clays in the igneous crust, the extent of which remains to be fully understood.
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Barker, W. W. "Bacterial Trace Fossils in Eocene Kaolin." Proceedings, annual meeting, Electron Microscopy Society of America 43 (August 1985): 238–39. http://dx.doi.org/10.1017/s0424820100118114.
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Spheroidal electron-dense masses averaging two microns in diameter comprise up to 20% of a thin Eocene grey kaolin in the upper part of the Huber Fm. near Wrens, Georgia. TEM and SEM reveal that the microspheroids consist of tangentially oriented kaolinite platelets enclosing much finer, delicate intergrowths of secondary authigenic minerals.Many types of bacteria and algae produce mucopolysaccharidal exudates which can attach clay platelets. Clay-clad microorganisms are especially common in marine and estuarine environments, where high ionic strength compresses the electric double layer of kaolinite sufficiently for van der Waals forces to aid its attachment to exudates. Maclean and Smart found clay-clad prokaryotic cells in recent estuarine sediments. Avnimelech, et al. demonstrated mutual flocculation of algae and clay upon addition of electrolyte. Because the size and structure of the clay-clad microspheroids in the Eocene kaolin closely resembles the clay-clad bacteria in recent marine muds, they are interpreted as trace fossils of bacteria.
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Cuevas, Jaime, Ana Ruiz, Raúl Fernández, Daniel González-Santamaría, María Angulo, Almudena Ortega, Elena Torres, and María Turrero. "Authigenic Clay Minerals from Interface Reactions of Concrete-Clay Engineered Barriers: A New Perspective on Mg-Clays Formation in Alkaline Environments." Minerals 8, no. 9 (August 21, 2018): 362. http://dx.doi.org/10.3390/min8090362.
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Artificial and singular geochemical environments are created around the engineered barrier systems (EBS) designed to isolate high level nuclear wastes in deep geological repositories. A concrete-bentonite interface takes place within the EBS and it builds a significant chemical gradient (pH), approximately from pH 8 (bentonite) to pH 12 (low alkali concrete), in a few millimetre thickness. This disequilibrium triggers dissolution and precipitation reactions and form a thin altered region. In this area, poorly ordered authigenic clay minerals, mainly hydrated magnesium silicates, are formed adjacent to hydrated calcium silicates and calcite precipitates adhered to the interface with concrete. This paper presents the development of this authigenic mineral layer comparing 6–18 months to 13 years interfaces. Scanning Electron Microscopy with Energy Dispersive X-ray spectroscopy (SEM-EDX) morphological and chemical characterization with the aid of ternary plots, X-ray diffraction (XRD) and infrared (IR) data show the young to old interface evolution from single brucite layers to stevensite-saponite silicates composition. Geochemical calculations indicate that this layer acts as a pH~11 buffer useful to minimize bentonite alteration and to favour the retention of amphoteric metal ions.
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Deocampo, Daniel M., and Joanne C. Tactikos. "Geochemical gradients and artifact mass densities on the lowermost Bed II eastern lake margin (~ 1.8 Ma), Olduvai Gorge, Tanzania." Quaternary Research 74, no. 3 (November 2010): 411–23. http://dx.doi.org/10.1016/j.yqres.2010.09.004.
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AbstractBulk geochemistry of ~ 1.8 Ma lacustrine claystone at Olduvai Gorge, Tanzania, is controlled principally by the geochemistry of ultrafine (< 0.1 μm), authigenic clay minerals. Authigenic clays have an average structural formula of (Si3.83Al0.17)(Al0.43Fe0.49Mg0.84)(Na0.99K0.22Ca0.16)O10(OH)2; octahedral composition varies, with Mg/(Al + Fe) ranging from 0.7 to 2.3. These clay minerals have a complex history of interaction with saline, alkaline water, followed by secondary diagenetic reactions that leached Mg in freshwater paleoenvironments. Lateral variations in whole-rock and clay geochemistry show westward enrichment in Mg, from Mgoct = 0.6–1.6. This is consistent with persistence of saline, alkaline Paleolake Olduvai to the west, and the presence of groundwater wetlands and other freshwater paleoenvironments to the east. Stone artifact mass density also varies systematically across the basal Bed II deposits, ranging from 100.0 to 104.3 g of artifacts per cubic meter of excavated sediment. Significant correlation is found between clay geochemistry and the density of artifacts excavated from associated archeological trenches (r2 = 0.59, p < 0.01). This relationship supports models of hominin land use in which artifact use and discard is concentrated near freshwater paleoenvironments such as wetlands associated with surface and groundwater discharge. Independent paleoenvironmental proxies such as clay geochemistry allow quantitative hypothesis testing to improve our understanding of early hominin behavior and paleoecology.
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Polkowski, George R. "Degradation of Reservoir Quality by Clay Content, Unayzah Formation, Central Saudi Arabia." GeoArabia 2, no. 1 (January 1, 1997): 49–64. http://dx.doi.org/10.2113/geoarabia020149.
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ABSTRACT Reservoirs in Central Saudi Arabia are important new sources of light sulfur-free crude oil. Development work on these wells has shown the adverse effect of authigenic clay minerals on their productivity or injectivity. The clay minerals may be affected during drilling of the well, during completion, during production, and/or injection. Kaolinite, chlorite, illite, and ordered and random mixed layer illite/smectite are commonly occurring authigenic clay minerals within the Permian Unayzah reservoir rock. As little as 2 weight percent clay causes permeability to be drastically reduced. Formation damage due to clay minerals results from: (1) swelling of smectite caused by injection water or drilling fluids of low salinity; (2) clay mineral migration and subsequent pore blockage; (3) precipitation of gelatinous pore-blocking iron hydroxides caused by the dissolution of chlorite by acid; (4) high water saturations; and (5) disaggregation of poorly consolidated parts of the reservoir into its component sand grains if the weak clay cements are disturbed. The implementation of clay control measures has resulted in increased production while minimizing formation damage.
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Tsirambides, A. E. "Detrital and authigenic minerals in sediments from the western part of the Indian Ocean." Mineralogical Magazine 50, no. 355 (March 1986): 69–74. http://dx.doi.org/10.1180/minmag.1986.050.355.10.
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AbstractMineralogical and oxygen isotope analyses have been performed on nine western Indian Ocean core samples in order to distinguish the detrital from authigenic minerals in the sediments. Following the removal of carbonates, organic constituents and Fe and Mn oxides, the residue was separated into five size fractions, the principal minerals present being feldspar, quartz, clinoptilolite, and clay minerals.Oxygen isotope compositions for two samples reflect an authigenic origin for clinoptilolite by the submarine alteration of volcanic material. Oxygen isotope compositions of two separates (free from feldspar and clays) suggest a detrital origin for the quartz in this area. The same mode of origin is apparent for the other components too, except possibly for some smectite which may have formed authigenically.
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Khidir, Ahmed, and Octavian Catuneanu. "Predictive diagenetic clay-mineral distribution in siliciclastic rocks as a tool for identifying sequence boundaries in non-marine successions: the Coalspur Formation, west-central Alberta." Geologos 15, no. 3-4 (December 1, 2009): 169–80. http://dx.doi.org/10.2478/v10118-009-0001-2.
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Predictive diagenetic clay-mineral distribution in siliciclastic rocks as a tool for identifying sequence boundaries in non-marine successions: the Coalspur Formation, west-central AlbertaThe study of upper Cretaceous-lower Tertiary fluvial deposits of the Coalspur Formation in the Foothills region of west-central Alberta reveals that the distribution of early authigenic kaolinite has a well-defined relation to the sequence stratigraphic framework. In this context, it has been observed that the kaolin mineral content increases in sandstones lying below subaerial unconformities, which mark the most significant stratigraphic hiatuses and hence the sequence boundaries in fully fluvial successions. The increased abundance of authigenic kaolinite immediately below sequence boundaries may have been caused by the infiltration of meteoric water during times of subaerial erosion, resulting in the dissolution of unstable minerals (e.g., micas and feldspar) and the formation of kaolinite and secondary porosity. It is therefore suggested that the change in clay mineral assemblages in the stratigraphic section depends in part on the position of the analyzed sandstone samples relative to the sequence boundaries. In a larger context, the method of using authigenic clays to delineate depositional sequences in non-marine successions needs to be evaluated on a case-by-case basis, as the diagnostic early diagenetic minerals underlying the sequence boundary may change as a function of palaeoclimate and also as a function of late diagenetic processes.
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Giorgetti, G., F. S. Aghib, K. J. T. Livi, A. C. Gaillot, and T. J. Wilson. "Newly formed phyllosilicates in rock matrices and fractures from CRP-3 core (Antarctica): an electron microscopy study." Clay Minerals 42, no. 1 (March 2007): 21–43. http://dx.doi.org/10.1180/claymin.2007.042.1.03.
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AbstractA scanning and transmission electron microscopy study has been performed on Oligocene glacio-marine sediments, Devonian sandstones, and Jurassic dolerites recovered during CRP-3 drilling in the Ross Sea (Antarctica). Newly formed clay minerals occur in the rock matrices and as fillings in veins and faults which crosscut the whole sequence. Authigenic clays in sediments consist of beidellite-montmorillonite, berthierine/chlorite intergrowths and illite. Al,K-rich smectites and kaolinite occur in the Devonian sandstones. Saponite, berthierine/chlorite intergrowths, and Fe-hydroxides develop in the altered dolerites. Hence, the composition of the secondary phases depends also on the geochemistry of the rock they grow in. Within each sample, the same authigenic minerals form in the matrix and in the vein/fault. Clays precipitated from fluids, with variable fO2 values, which circulated in the system during the contemporaneous diagenetic and faulting events.
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Iacoviello, F., G. Giorgetti, F. Nieto, and I. T. Memmi. "Evolution with depth from detrital to authigenic smectites in sediments from AND-2A drill core (McMurdo Sound, Antarctica)." Clay Minerals 47, no. 4 (December 2012): 481–98. http://dx.doi.org/10.1180/claymin.2012.047.4.07.
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AbstractWe have examined the nature and origin of smectites in glaciomarine sediments of the AND-2A drill core (McMurdo Sound, Antarctica) by means of X-ray diffraction (XRD) analyses on the clay fraction, field emission scanning electron microscopy (FESEM), scanning electron microscopy (SEM) observations and SEM-EDS microanalyses on smectite particles. Relying on the smectite variation throughout the drill core it was possible to split the sequence into three units. Smectites throughout the core are either detrital or authigenic. Detrital smectites are close to montmorillonite-beidellite in composition while newly-formed smectites frequently have higher Fe-Mg contents and intermediate compositions between the saponite and nontronite field, with lower amounts in the montmorillonite-beidellite field. In the upper sedimentary sections (Unit I, and Unit II, 36-440 mbsf, 0.7-16.5 Ma) smectites are interpreted to be predominantly detrital, whereas in the lower portion of the core (Unit III, 440-1123.20 mbsf, 16.5-20.2 Ma) authigenic smectites are the most common feature. The predominance of mica, the abundance of chlorite, and the nature of smectites in the upper units indicate physical weathering under cold and dry climate, and a dominant provenance for the clay minerals from the Transantarctic Mountains. Smectites in the lower unit are considered mostly authigenic and they are most likely to be the result of early diagenetic processes, being formed from the alteration of volcanic material (glass, pyroxenes and feldspars) and/or through precipitation from fluids of a possible hydrothermal origin. Our survey attests to the importance of discriminating between a detrital and authigenic nature of smectites as the occurrence of authigenic clay minerals in ancient sedimentary successions might lead to incorrect palaeoclimatic interpretations, since they can be affected by diagenetic processes, thus obliterating the climatic signal.
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Sangüesa, F. J., J. Arostegui, and I. Suarez-Ruiz. "Distribution and origin of clay minerals in the Lower Cretaceous of the Alava Block (Basque-Cantabrian Basin, Spain)." Clay Minerals 35, no. 2 (April 2000): 393–410. http://dx.doi.org/10.1180/000985500546864.
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AbstractLower Cretaceous clay minerals suites of the Alava Block, analysed by XRD, are dominated either by illite or kaolinite. These assemblages are mainly inherited in origin, although textural evidence (SEM) indicates some diagenetic clay. Precipitation of blocky kaolinite took place in sandstones from the southern domain of the Block, characterized by low sedimentation and subsidence rates and by low vitrinite reflectance values (%Rr <0.8). In the northern domain, where sedimentation and subsidence rates were high (%Rr >3.3), illitization of kaolinite and smectitic clays and precipitation of authigenic chlorite occurred. Some chemical aspects of these reactions are discussed.
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Huggett, J. M., B. Laenen, and N. Vandenberghe. "Green clays from the Lower Oligocene of Aardebrug, Belgium: a re-evaluation." Clay Minerals 31, no. 4 (December 1996): 557–62. http://dx.doi.org/10.1180/claymin.1996.031.4.13.
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Porrenga (1968) described the green clays from the Lower Oligocene of Aardebrug, east of Leuven (Louvain) in Belgium as glauconitic illite, a mineral intermediate in chemistry between glauconite and illite, and presumed this clay to be neoformed, though the mode of origin is not discussed. Notably, most of the section from which Porrenga obtained his sample of 'glauconitic illite' is nonmarine. Non-marine glauconites are rare in the literature and there is no standard terminology. Parry and Reeves (1966) reported green pellets of 10 Å clay from recent sediments at Lake Mound, Texas, but with no detrital green clay as source and an authigenic origin is assumed. Green clays described as Fe-rich mica occur in lacustrine environments in the Oligocene of Cantal (Jung, 1954), and the Massif Central (Gabis, 1963) in France. These deposits are derived from altered crystalline basement.
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Jeans, C. V. "Clay mineralogy of the Permo-Triassic strata of the British Isles: onshore and offshore." Clay Minerals 41, no. 1 (March 2006): 309–54. http://dx.doi.org/10.1180/0009855064110199.
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AbstractThe regional distribution, mineralogy, petrology and chemistry of the detrital and authigenic clay minerals associated with the Permo-Triassic strata (excluding the Rotliegend: see Ziegler, 2006; this volume), of the onshore and offshore regions of the British Isles are reviewed within their stratigraphical framework. The origin of these clay minerals is discussed in relation to current hypotheses on the developments of the Mg-rich clay mineral assemblages associated with the evaporitic red-bed Germanic facies of Europe and North Africa.Composite clay mineral successions are described for seven regions of the British Isles — the Western Approaches Trough; SW England; South Midlands; Central Midlands; the Cheshire Basin; NE Yorkshire; and the Central North Sea. The detrital clay mineral assemblages of the Early Permian strata are variable, consisting of mica, smectite, smectite-mica, kaolin and chlorite, whereas those of the Late Permian and the Trias are dominated by mica, usually in association with minor Fe-rich chlorite. The detrital mica consists of a mixture of penecontemporaneous ferric mica, probably of pedogenic origin, and recycled Pre-Permian mica. In the youngest Triassic strata (Rhaetian), the detrital clay assemblages may contain appreciable amounts of poorly defined collapsible minerals (irregular mixed-layer smectite-mica-vermiculite) and kaolin, giving them a Jurassic aspect. There are two types of authigenic clay mineral assemblages. Kaolin may occur as a late-stage diagenetic mineral where the original Permo-Triassic porewaters of the sediment have been replaced by meteoritic waters. A suite of early-stage diagenetic clay minerals, many of them Mg-rich, are linked to the evaporitic red-bed facies — these include sepiolite, palygorskite, smectite, irregular mixed- layer smectite-mica and smectite-chlorite, corrensite, chlorite and glauconite (sensu lato). The sandstones and mudstones of the onshore regions of the British Isles display little or no difference in their detrital and authigenic clay mineral assemblages. In contrast, the sandstones of the offshore regions (North Sea) show major differences with the presence of extensive chloritic cements containing Mg-rich and Al-rich chlorite, irregular mixed-layer serpentine-chlorite, and mica.
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Huggett, J. M., and H. F. Shaw. "Field emission scanning electron microscopy — a high-resolution technique for the study of clay minerals in sediments." Clay Minerals 32, no. 2 (June 1997): 197–203. http://dx.doi.org/10.1180/claymin.1997.032.2.03.
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AbstractThe use of field emission electron microscopy for the study of clay mineral petrography in mudrocks and sandstones is discussed. The methodology including sample preparation is outlined and three examples of the application of the technique are described: the formation of authigenic illite in mudrocks, the multiple generation of authigenic illites in sandstones and the effects of KCl drilling muds on shale fabrics. In the study of authigenic illite formation in Palaeocene mudrocks from the North Sea, the FESEM analyses have demonstrated the formation of illites with increasing burial depth that conventional SEM and XRD analyses had failed to show. The FESEM analyses of the authigenic illites in Carboniferous sandstones from the southern North Sea revealed at least three different habits representing different generation episodes rather than one illite formation event.This has important repercussions with regard to the interpretation of stable isotope and dating data for the illites. Significant petrographic changes in shales after treatment with KCl drilling muds have been observed from FESEM analyses, suggesting reactivity between the shales and the KCl muds.
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Jeans, C. V., D. S. Wray, R. J. Merriman, and M. J. Fisher. "Volcanogenic clays in Jurassic and Cretaceous strata of England and the North Sea Basin." Clay Minerals 35, no. 1 (March 2000): 25–55. http://dx.doi.org/10.1180/000985500546710.
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AbstractThe nature and origin of authigenic clay minerals and silicate cements in the Jurassic and Cretaceous sediments of England and the North Sea are discussed in relation to penecontemporaneous volcanism in and around the North Sea Basin. Evidence, including new REE data, suggests that the authigenic clay minerals represent the argillization of volcanic ash under varying diagenetic conditions, and that volcanic ash is a likely source for at least the early silicate cements in many sandstones. The nature and origin of smectite-rich, glauconite-rich, berthierine-rich and kaolin-rich volcanogenic clay mineral deposits are discussed. Two patterns of volcanogenic clay minerals facies are described. Pattern A is related to ash argillization in the non-marine and marine environments. Pattern B is developed by the argillization of ash concentrated in the sand and silt facies belts in the seas bordering ash-covered islands and massifs. It is associated with regression/ transgression cycles which may be related to thermal doming and associated volcanism, including the submarine release of hydrothermal fluids rich in Fe. The apparent paucity of volcanogenic clay deposits in the Jurasssic and Early Cretaceous sediments of the North Sea is discussed.
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Jones, L. E., and B. W. Sellwood. "Palaeogeographic Significance of Clay Mineral Distributions in the Inferior Oolite Group (Mid Jurassic) of Southern England." Clay Minerals 24, no. 1 (March 1989): 91–105. http://dx.doi.org/10.1180/claymin.1989.024.1.08.
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AbstractFive areally distinct mineral assemblages are recognized in the Inferior Oolite of S. England. In each area, vertical (stratigraphic) variations are insignificant. The five assemblages comprise varying proportions of illite, illite-smectite, kaolinite, chlorite and kaolinite-smectite, the mixed-layer clays being largely poorly crystalline and randomly interstratified. A predominantly detrital rather than authigenic origin is suggested for most of the clays. Shallow-water platform carbonates contain kaolinite with illite and illite-smectite. Kaolinite decreases in abundance away from former mid-Jurassic land areas, the deeper shelf and more basinal facies being dominated by illite and/or illite-smectite. Possible volcanic contributions to clay suites are suggested but cannot yet be fully evaluated. The palaeogeographic usefulness of clay mineral suites is confirmed, even in carbonate-dominated systems.
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Bozkaya, Ö., H. Yalçin, and P. A. Schroeder. "Two-step mode of clay formation in the extensional basins: Cambrian–Ordovician clastic rocks of the Antalya unit, SW Turkey." Clay Minerals 52, no. 3 (September 2017): 365–89. http://dx.doi.org/10.1180/claymin.2017.052.3.07.
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AbstractOrdovician clastic rocks of the Antalya unit in SW Turkey bear mineralogical/geochemical evidence of Triassic extensional rift timing and spatial relations. The crystal chemistry of the phyllosilicate assemblages (illite, chlorite, kaolinite, mixed-layer illite-smectite, chlorite-vermiculite and chlorite-smectite) is consistent with the rock experiencing a multi-generational burial history. The appearance of kaolinite and illite-smectite-bearing rocks in the Antalya unit is characteristic of diagenetic-anchimetamorphic conditions and is of higher grade than their anchi-epizonal equivalents in other regions of the Tauride belt. Illites and chlorites are of both detrital and authigenic origin, whereas I-S and kaolinites are authigenic. Detrital micas have been altered to chlorite and K-white mica stacks in which relicts suggest the chlorites were derived from detrital biotites. The broad X-ray diffraction illite peaks show that they are composed both of illite and illite-smectite. Na,K-mica and paragonite occur within the chlorite-mica stacks as replacements of muscovite, probably driven by Na-rich solutions. The authigenic clays were formed within the microporous matrix and the interplanar spaces of {001} planes of chlorite-mica stacks, with textures independent of the bedding and foliation planes of the rocks. The authigenic chlorites exhibit higher Si and Fe and lower Mg contents than their detrital counterparts. Authigenic chlorite thermometry indicates rift-related temperatures of 50–150°C, whereas pre-rift detrital chlorites formed at temperatures of >200°C. Authigenic illite and illite-smectite are phengitic in composition and contain more Si, Mg, Fe and Ca and less Al and K than detrital K-white micas. The textural, mineralogical and chemical characteristics support the hypothesis that the mineral assemblages were a result of a two-step mode of formation with diagenetic overprints of previously anchizonal rocks in extensional basin conditions.
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Yaremchuk, Yaroslava, Sofiya Hryniv, Tadeusz Peryt, Serhiy Vovnyuk, and Fanwei Meng. "Controls on Associations of Clay Minerals in Phanerozoic Evaporite Formations: An Overview." Minerals 10, no. 11 (November 1, 2020): 974. http://dx.doi.org/10.3390/min10110974.
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Information on the associations of clay minerals in Upper Proterozoic and Phanerozoic marine evaporite formations suggests that cyclic changes in the (SO4-rich and Ca-rich) chemical type of seawater during the Phanerozoic could affect the composition of associations of authigenic clay minerals in marine evaporite deposits. The vast majority of evaporite clay minerals are authigenic. The most common are illite, chlorite, smectite and disordered mixed-layer illite-smectite and chlorite-smectite; all the clay minerals are included regardless of their quantity. Corrensite, sepiolite, palygorskite and talc are very unevenly distributed in the Phanerozoic. Other clay minerals (perhaps with the exception of kaolinite) are very rare. Evaporites precipitated during periods of SO4-rich seawater type are characterized by both a greater number and a greater variety of clay minerals—smectite and mixed-layer minerals, as well as Mg-corrensite, palygorskite, sepiolite, and talc, are more common in associations. The composition of clay mineral association in marine evaporites clearly depends on the chemical type of seawater and upon the brine concentration in the evaporite basin. Along with increasing salinity, aggradational transformations of clay minerals lead to the ordering of their structure and, ideally, to a decrease in the number of minerals. In fact, evaporite deposits of higher stages of brine concentration often still contain unstable clay minerals. This is due to the intense simultaneous volcanic activity that brought a significant amount of pyroclastic material into the evaporite basin; intermediate products of its transformation (in the form of swelling minerals) often remained in the deposits of the potassium salt precipitation stage.
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Huggett, J. M., and R. W. O'B Knox. "Clay mineralogy of the Tertiary onshore and offshore strata of the British Isles." Clay Minerals 41, no. 1 (March 2006): 5–46. http://dx.doi.org/10.1180/0009855064110195.
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AbstractTertiary sediments are of restricted occurrence in the onshore British Isles but occur extensively offshore, attaining thicknesses of ~4 km in the Faroe—Shetland Basin and ~3 km in the North Sea Basin. Clay mineral stratigraphic studies of the North Sea Paleocene to Lower Miocene successions show a dominance of smectite (and smectite-rich illite-smectite) with minor illite, kaolin and chlorite. Abundant smectite in the Paleocene and Eocene reflects alteration of volcanic ash derived from pyroclastic activity associated with the opening of the North Atlantic between Greenland and Europe. However, the persistence of high smectite into the Oligocene and Middle Miocene indicates that smectite-rich soils on adjacent land areas may also have been an important source of detrital clays. An upwards change to illite-dominated assemblages in the Middle Miocene reflects higher rates of erosion and detrital clay supply, with a subsequent increase in chlorite reflecting climatic cooling. The persistence of smectite-rich assemblages to depths of >3000 m in the offshore indicates little burial-related diagenesis within the mudstone succession, possibly as a consequence of over-pressuring. Despite the importance of Paleocene and Eocene sandstones as hydrocarbon reservoirs in the North Sea and Faroe-Shetland basins, there are few published details of the authigenic clays. The principal clay cements in these sandstones are kaolin and chlorite, with only minor illite reported.The offshore successions provide a valuable background to the interpretation of the more intensively studied, but stratigraphically less complete, onshore Tertiary successions. The most extensive onshore successions occur in the London and Hampshire basins where sediments of Paleocene to earliest Oligocene age are preserved. Here clay assemblages are dominated by illite and smectite with subordinate kaolin and chlorite. The relatively large smectite content of these successions is also attributed primarily to the alteration of volcanic ash. Associated non-smectitic clays are largely detrital in origin and sourced from areas to the west, with reworking of laterites and “china clay” deposits developed over Cornish granites. Authigenic clays include glauconite (sensu lato), early diagenetic kaolin that has replaced muscovite (principally in the London Clay Formation of the London Basin) and smectite that has replaced ash. Pedogenesis has extensively modified the assemblages in the Reading Formation and Solent Group. Tertiary sediments are largely missing from onshore northern and western Britain, but clays and sands of Eocene and Oligocene age are locally preserved in small fault-bounded basins. Here, clay assemblages are dominated by kaolin with minor illite.
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Medina, Daniel Alonso, and David Budd. "Critical Diagenetic Features Controlling Intergranular Flow Paths and Matrix Permeability in the Codell Sandstone, Northeastern Colorado." Mountain Geologist 57, no. 2 (April 1, 2020): 95–120. http://dx.doi.org/10.31582/rmag.mg.57.2.95.
Full textAbstract:
The Codell Sandstone is a hydrocarbon-bearing, tight sand (permeability <0.1 mD) that is an active target for unconventional hydrocarbon production in the Denver-Julesburg Basin. In northeastern Colorado, the intergranular microporous drainage network within this clay-rich sandstone is poorly understood, with a strong diagenetic control suggested by the lack of correlation between permeability and depositional facies. Core samples from the Wattenberg Field and Redtail areas in Weld County were used to identify which diagenetic processes were most important in developing a connected pore network. Thirteen diagenetic features were defined using thin-section petrography and electron microprobe mineralogical phase mapping, and skeletonized flow paths were delineated by epifluorescence imaging. Quartz overgrowths, mechanical compaction, and clay cements (illite, chlorite, and kaolinite) are better developed in the laminated facies than the burrowed facies. Authigenic calcite and pyrite, and dissolution of framework grains are equally developed in both types of facies. Cumulative 2D flow-path lengths positively co-vary with permeability, indicating that the skeletonized paths capture the features that control permeability. The longest flow paths in high permeability (≥0.09 mD) samples follow micropores created along the periphery of framework grains where the discontinuous quartz overgrowths abut clays. Micropores within intergranular clay masses (detrital, pore-filling cements, and authigenic replacements) associate with shorter flow paths that dominate in low permeability (≤ 0.01 mD) samples and feed the longer paths in high permeability samples. While compaction and all types of cements had a negative impact on the original pore network, the development of long contacts between quartz overgrowths and mechanically juxtaposed grains eventually became beneficial to the drainage system. The increased surface area along those contacts increased the continuity of the flow paths developed along grain surfaces. All observations indicate that the minute quartz overgrowths, and the high authigenic rugosity they created along grain boundaries, were a key diagenetic event in creating the most efficient drainage networks that now facilitate the movement of hydrocarbons at the core-plug scale.
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Dias, Isis Armstrong, Leonardo Fadel Cury, Bruno Guimarães Titon, Gustavo Barbosa Athayde, Guilherme Fedalto, Larissa da Rocha Santos, Ana Paula Soares, Camila de Vasconcelos Müller Athayde, and Anelize Manuela Bahniuk Rumbeslperger. "The Occurrence of Authigenic Clay Minerals in Alkaline-Saline Lakes, Pantanal Wetland (Nhecolândia Region, Brazil)." Minerals 10, no. 8 (August 17, 2020): 718. http://dx.doi.org/10.3390/min10080718.
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Mg clay minerals are usually associated with carbonates in alkaline-saline environments, precipitated from solution and/or transformation from other minerals. The aim of this research is to identify the mineralogy and geochemistry of clay minerals in different alkaline lakes in the Nhecolândia region, the southernmost region of the Pantanal wetland (Brazil). Sediment samples were analyzed by X-ray diffraction, X-ray fluorescence, scanning electron microscopy and transmission electron microscopy. Water samples were analyzed, determining their main cations and anions, in order to understand their relationship with the clays. The analyses allowed classifying the water bodies as saline, oligosaline and freshwater lakes. The sediments are composed mainly of quartz and a fine-clay fraction, dominated by illite, kaolinite and smectite. The XRD results showed illite and smectite mixed-layered in the saline lakes at Barranco Alto farm, whereas at Nhumirim farm, trioctahedral smectite was only observed in one lake. The smectite minerals were normally identified coupled with calcite at the top of the sequences, associated with exopolymeric substances (EPS) in the lakes, suggesting that these minerals are precipitating due to the physical-chemical and biological conditions of the water bodies.
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Gillott, J. E. "Some clay-related problems in engineering geology in North America." Clay Minerals 21, no. 3 (September 1986): 261–78. http://dx.doi.org/10.1180/claymin.1986.021.3.02.
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AbstractClay minerals are almost ubiquitous in soil and rock and are among the most reactive silicates. They affect the engineering behaviour of soil and rock both as materials of construction and as foundation materials. In the petroleum industry, clay affects the permeability of reservoir formations, it is a common cap-rock, and it is also a constituent of the fluids used in drilling operations. Engineering behaviour almost always involves clay-water interaction and in turn this depends on the nature of water and solutions and on the composition and microstructure of the clay. The importance of clay to specific problems from each of these areas is discussed. In foundation engineering its role in soil-moisture interaction is illustrated by reference to problems resulting from the geological history of some North American soils and from engineering activities. In building materials, reference is made to its effect on concrete durability in aggregate-related problems. The importance of clay in petroleum engineering refers to authigenic clays in reservoir rocks, to clay behaviour in the Alberta oil sands and to the use of clay minerals as a geothermal thermometer.
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Veniale, F., A. Delgado, L. Marinoni, and M. Setti. "Dickite genesis in the ‘varicoloured’ clay-shale formation of the Italian Apennines: an isotopic approach." Clay Minerals 37, no. 2 (June 2002): 255–66. http://dx.doi.org/10.1180/0009855023720032.
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AbstractDickite occurs over wide areas along the Italian Apennines strip throughout Italy, mainly in the allochtonous ‘varicoloured’ clay-shale formation. Morphological, fabric and crystallochemical features suggest an authigenic origin, from pore solutions. The nature of the solutions and the process of dickite formation, including hydrothermalism, diagenesis or supergene evolution have all been discussed. Stable isotope analysis (O, H) was performed to investigate these points. The δD values of dickite range between −63.7 and −79.1% (SMOW) and δ18O between +21% and +16.1‰ (SMOW), and are similar to those reported for kaolinites formed in equilibrium with meteoric waters. The data fall along the ‘Line of Meteoric Kaolinites’, supporting an origin involving meteoric waters and low temperatures. The isotopic compositions of the waters are within the range of Apennines meteoric water, and the temperatures derived are close to surface conditions. Contributions of diagenetic, hydrothermal or metamorphic waters must be discounted. The authigenic dickite from ‘varicoloured’ clays of the Italian Apennines formed by precipitation from flushing meteoric waters whose ingress was favoured by repeated surface erosion.
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Huggett, J. M. "Aluminosilicate diagenesis in a Tertiary sandstone-mudrock sequence from the central North Sea, UK." Clay Minerals 31, no. 4 (December 1996): 523–36. http://dx.doi.org/10.1180/claymin.1996.031.4.10.
Full textAbstract:
AbstractMudrocks and sandstones from the Palaeocene of the central North Sea have been studied to assess the petrology, diagenesis and extent of any chemical interaction between the two lithologies. Authigenic and detrital minerals have been distinguished using a variety of electron microscope techniques. Small but significant quantities of authigenic minerals, which would not be detected by conventional petrographic tools, have been detected through the use of high-resolution electron beam techniques. Sandstone mineralogy has been quantified by point counting, and mudrock mineralogy semi-quantified by XRD. The detrital and authigenic mineralogy in the sandstone is almost identical to that found in the mudrock. The principal difference is in the relative proportions. Qualitative mass balance suggests that cross-formational flow has not been significant in either clay or quartz diagenesis.
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Papavassiliou, C. T. "GEOCHEMICAL- MINERALOGICAL AND METALLOGENETICAL ASPECTS CONCERNING THE ORIGIN OF SEDIMENTS FROM LEG. 22 D.S.D.P DRILLED SITES 212 AND 213 IN EASTERN INDIAN OCEAN." Bulletin of the Geological Society of Greece 40, no. 2 (January 1, 2007): 918. http://dx.doi.org/10.12681/bgsg.16747.
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Basic mineralogical and geochemical data, are presented for sediment core samples from Deep Sea Drilling Project(D.S.D.P) boreholes .Sites 212 and 213 respectively, from the eastern Indian Ocean. In both Sites the Fe-Mn oxides are abundant controlling a numerous suite of trace elements. In Site 212 the Fe-Mn oxides are more abundant in the upper part of the borehole having mainly a diagenetic or hydrogenous origin, whilst in Site 213 these oxides are more abundant in the lower part having mainly a hydrothermal origin. In both Sites clay minerals are consisting mostly of the expandable mixed layered smectite/illite. The geochemical data shows that in both Sites the majority of the sediments have the characteristics of typical deep sea clay being both of detrital and authigenic origin. In Site 212 these clays with considerable amount of palygorskite and the zeolite clinoptilolite, both of authigenic origin, opaline silica, biogenous CaCOj ,the Fe-Mn oxides and some other detrital minerals together control the bulk chemical composition of the sediments. In Site 213 the clays with large amounts of Fe-Mn oxides and considerable amounts of the zeolite Phillipsite and Palygorskite in small amounts and some other detrital minerals, control the chemical composition of the sediments. The increase in the Ti/Al and Mg/Al ratios with depth in both Sites implies a volcanoclastic input in the bottom sediments probably from the underlying basaltic basement
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Çiflikli, M., E. Çiftçi, and H. Bayhan. "Alteration of glassy volcanic rocks to Naand Ca-smectites in the Neogene basin of Manisa, western Anatolia, Turkey." Clay Minerals 48, no. 3 (June 2013): 513–27. http://dx.doi.org/10.1180/claymin.2013.048.3.08.
Full textAbstract:
AbstractAlkali- and Ca-rich smectites occur in association with Neogene lacustrine sedimentary rocks and high-K calc-alkaline volcanic rocks with compositions ranging from andesite to rhyolite in western Anatolia (Turkey). Major clay occurrences are associated predominantly with the Foça and Akçaköy ignimbrites and with the ignimbrites within the Rahmanlar pyroclastics. Experimental studies indicate that the main clay minerals present are Na- and Ca-smectite and subordinate illite, associated with silica polymorphs, trace clinoptilolite and chlorite. The authigenic minerals formed by weathering and metasomatic reactions between hot volcanic material and lake water. Smectite was produced as a result of argillic alteration of the volcanic glass and feldspars of the ignimbrites, Rahmanlar pyroclastics and reworked volcaniclastic sediments through chemical weathering and dissolution-precipitation processes and formed as authigenic phases both in terrestrial and nearby shallow lacustrine environments under prevalent humid or semi-humid climate during the Neogene.
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Jeans, C. V., M. J. Fisher, and R. J. Merriman. "Origin of the clay mineral assemblages in the Germanic facies of the English Trias: application of the spore colour index method." Clay Minerals 40, no. 1 (March 2005): 115–29. http://dx.doi.org/10.1180/0009855054010160.
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AbstractThe origin of the regional and stratigraphical variation in the Triassic authigenic clay assemblages of England is discussed in relation to new estimates of the palaeotemperatures experienced by their host sediments and a preliminary study by transmission electron microscopy of their microtextural features. Spore colour index measurements, based on the spore type Deltoidospora s.l. occurring in the sediments (Penarth Group) at the very top of the Triassic sequence, give estimated palaeotemperatures ranging from 60–74°C (south Devon) to 89–97°C (northeast Yorkshire). Calculated palaeotemperatures, based on a gradient of 25°C/km, for the main zone of authigenic clay minerals range from 63–77°C to 89–97°C for the top to 71–85°C to 94–104°C for the base. Irregular mixed-layer smectite-chlorite, corrensite and Mg-rich chlorite are associated with calculated palaeotemperatures of 66–86°C, 66–104°C and 75–104°C respectively. The suggestion that elsewhere in the UK corrensite and Mg-rich chlorite were formed at temperatures in excess of 100°C finds no support. Geothermal gradients would have to have been of the order of at least 100–300°C/km to obtain these temperatures within the Triassic sediments; such values are associated typically with high-level magmatic intrusions or geothermal systems of which there is no geological evidence. The balance of evidence suggests that the Triassic authigenic clay assemblages formed by neoformation during the early stages of sediment diagenesis under the influence of variation in the alkalinity of the depositional environments.
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Chen, Bo, Feng Wang, Jian Shi, Fenjun Chen, and Haixin Shi. "Origin and Sources of Minerals and Their Impact on the Hydrocarbon Reservoir Quality of the PaleogeneLulehe Formation in the Eboliang Area, Northern Qaidam Basin, China." Minerals 9, no. 7 (July 15, 2019): 436. http://dx.doi.org/10.3390/min9070436.
Full textAbstract:
The Lulehe sandstone in the Eboliang area is a major target for hydrocarbon exploration in the northern Qaidam Basin. Based on an integrated analysis including thin section analysis, scanning electron microscopy, X-ray diffraction, cathodoluminescence investigation, backscattered electron images, carbon and oxygen stable isotope analysis and fluid inclusion analysis, the diagenetic processes mainly include compaction, cementation by carbonate and quartz, formation of authigenic clay minerals (i.e., chlorite, kaolinite, illite-smectite and illite) and dissolution of unstable materials. Compaction is the main factor for the deterioration of reservoir quality; in addition, calcitecement and clay minerals are present, including kaolinite, pore-filling chlorite, illite-smectite and illite, which also account for reservoir quality reduction. Integration of petrographic studies and isotope geochemistry reveals the carbonate cements might have originated from mixed sources of bioclast- and organic-derived CO2 during burial. The quartz cement probably formed by feldspar dissolution, illitization of smectite and kaolinite, as well as pressure solution of quartz grains. Smectite, commonly derived from alteration of volcanic rock fragments, may have been the primary clay mineral precursor of chlorite. In addition, authigenic kaolinite is closely associated with feldspar dissolution, suggesting that alteration of detrital feldspar grains was the most probable source for authigenic kaolinite. With the increase in temperature and consumption of organic acids, the ratio of K+/H+ increases and the stability field of kaolinite is greatly reduced, thereby transforming kaolinite into mixed layer illite/smectite and illite. Within the study area, porosity increases with chlorite content up to approximately 3% volume and then decreases slightly, indicating that chlorite coatings are beneficial at an optimum volume of 3%. A benefit of the dissolution of unstable minerals and feldspar grains is the occurrence of secondary porosity, which may enhance porosity to some extent. However, the solutes cannot be transported over a large scale in the deep burial environment, and simultaneous precipitation of byproducts of feldspar dissolution such as authigenic kaolinite and quartz cement will occur in situ or in adjacent pores, resulting in heterogeneity of the reservoirs.
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Huggett, Jennifer. "Petrology and diagenesis of Palaeogene clays from Ølst and Ålbækhoved, Denmark." Bulletin of the Geological Society of Denmark 40 (December 30, 1993): 256–71. http://dx.doi.org/10.37570/bgsd-1993-40-11.
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The petrology and diagenesis of Paleocene and Eocene clays from 01st and Albrekhoved in northern Jutland, Denmark has been investigated using backscattered electron microscopy and XRD techniques. The Holmehus, 01st, Rpsnres and Lillebrelt Forma- tions were sampled at both localities, whilst at 01st, the Spvind Marl was also sampled. These sediments are extremely fine grained, smectite-rich, vari-coloured claystones with ash horizons in several formations. Smectite and carbonate minerals are the principal authigenic phases. Smectite is inferred to have formed as a result of alteration of volcanic glass, though it is unclear how much of the smectite is detrital. Three manganese bearing carbonate cements have been identified in all Formations sampled at both localities except the Holmehus Formation. These cements are manganoan calcite, calcian rhodochrosite and manganoan siderite. All occur as equant to subequant rhombs, up to 15 µm across, but typically 2-5 µm. Calcian rhodochrosite is present as overgrowths on rounded clay-size particles of high Mg (20%) calcite, which are either detrital grains or corroded authigenic cement. It also occurs as overgrowths on equant rhombs of earlier formed manganoan calcite. The manganoan siderite occurs as relatively large crystals (20 µm) scattered through the clay matrix and as concretions. Calcite cement is present in the Lillebrelt and 01st Formations. Quantitatively it is not as important as the more unusual Mn-bearing calcium carbonates.
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Tsipoura-Vlachou, M. "DIAGENESIS OF THE MARLY-GYPSUM FORMATIONS, IGOUMENITSA AREA, N.W. GREECE." Bulletin of the Geological Society of Greece 40, no. 2 (January 1, 2007): 1009. http://dx.doi.org/10.12681/bgsg.16783.
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The Igoumenitsa area, in northwestern Greece, is composed of organic-rich clay evaporitic formations, of the Ionian zone. They have undergone diagenetic processes, which effect the mineralogical transformations. The purpose of this paper is the study of the mineralogical diagenesis and the possible implications to the geotechnical behavior of these organic-rich clay evaporitic sedimentary rocks. The diagenetic minerals reported in this study are: A: The authigenic swelling clay minerals, smectite and mixed layers of smectite. B. The two characteristic minerals phases of the sulfate diagenesis: I. Bassanite (semi hydrated gypsum-Ca04.l/2H20) and 2. Celestite (SrS04) that can be considered as an indicator of bacterial sulphate reduction, fluid flow and recycling ofevaporites. The two authigenic minerals have derived from the evaporites, mostly by the dehydration of gypsum and by the action of pore water that is charged with the ions derived from the dissolution of preexistent sulfates, halite and carbonates. C. The neoformation of the carbonate minerals aragonite and dolomite, due to probably bacterial sulfate reduction. When organic-clay rich sediments, are associated to evaporites, the diagenetic processes become more complex and interacted. The diagenetic alterations of the gypsum/anhydrite rocks are related to the geotechnical behavior of the formation and may lead to possible karstiflcation. That may cause problems in roads and tunnels construction on or through these evaporitic series
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Mossmann, J. R. "K-Ar dating of authigenic illite-smectite clay material: application to complex mixtures of mixed-layer assemblages." Clay Minerals 26, no. 2 (June 1991): 189–98. http://dx.doi.org/10.1180/claymin.1991.026.2.04.
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AbstractGenetically homogeneous clay fractions are not always available for K-Ar isotopic dating of authigenic sedimentary material, particularly when dating illitic mixed-layer clay minerals. Three populations of mixed-layer clay minerals have been recognized in Upper Triassic sandstones from the Paris Basin (France), their occurrences being related to the flow of allochthonous fluids across the stratigraphic sections of the basin during Mesozoic times. A method is described for interpreting the K-Ar mixture ages obtained on carefully selected fractions, resulting in constraints being able to be made on the timing of the movements of these fluids.
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Mayayo, M. J., B. Bauluz, and J. M. Gonzalez Lopez. "Variations in the chemistry of smectites from the Calatayud Basin (NE Spain)." Clay Minerals 35, no. 2 (April 2000): 365–74. http://dx.doi.org/10.1180/000985500546837.
Full textAbstract:
AbstractSmectites of sedimentary series from a playa lake system from Calatayud Basin have been studied by XRD and TEM chemical microanalyses. Clay particle microanalyses show complete continuity between dioctahedral aluminous and trioctahedral magnesian smectites. Aluminous smectites have been classified as montmorillonites and ferribeidellites, both with compositional variability. They represent detrital phases resulting from weathering in the source area. Compositionally-intermediate smectites (beidellite-saponite and montmorillonite-stevensite) seem to correspond to weighted mean compositions of di- and trioctahedral phases stacked together in the same particle. They represent intermediate transitional stages from detrital to authigenic smectites in more distal basin facies. Trioctahedral smectites, although called saponites and stevensites, are actually random mixed-layer kerolite-Mg-smectite with a high percentage of expandable layers. They represent authigenic clays formed from solutions with high pH and Mg content as a result of evaporative concentration. The variability in composition of smectites, both within the same sample and amongst different samples, is a possible consequence of the heterogeneity in the local chemical environment, and so, equilibrium may be only reached locally in a large variety of microsystems.
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Niu, Xing, Detian Yan, Mingyi Hu, Zixuan Liu, Xiaosong Wei, and Mingtao Zuo. "Controls of Distinct Mineral Compositions on Pore Structure in Over-Mature Shales: A Case Study of Lower Cambrian Niutitang Shales in South China." Minerals 11, no. 1 (January 6, 2021): 51. http://dx.doi.org/10.3390/min11010051.
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Investigating the impacts of rock composition on pore structure is of great significance to understand shale gas occurrence and gas accumulation mechanism. Shale samples from over-mature Niutitang formation of Lower Cambrian in south China were measured by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), low pressure N2 and CO2 adsorption to elucidate the controls of distinct mineral composition on pore development. Two distinct lithofacies, namely siliceous shale and argillaceous shale, were ascertained based on their mineral composition. Due to the variability of mineral composition in different lithofacies, pore structure characteristics are not uniform. Pores in siliceous shales are dominated by interparticle pores and organic matter (OM) pores, among which the interparticle pores are mainly developed between authigenic quartz. Furthermore, most of these interparticle pores and cleavage-sheet intraparticle pores within clay minerals are usually filled by amorphous organic matter that is host to OM pores. Due to the lack of rigid minerals, argillaceous shale was cemented densely, resulting in few interparticle pores, while cleavage-sheet intraparticle pores within clay minerals are common. Comparing siliceous shales with argillaceous shales, specific surface areas and pore volumes are higher on the former than on the latter. The content of total organic carbon (TOC) and authigenic quartz have a great influence on micropore structures, but less on mesopore structure for siliceous shales. The rigid framework structure formed by authigenic quartz is believed to be able to prevent primary interparticle pores from mechanical compaction and facilitate the formation of organic matter-associated pores. In terms of argillaceous shales, due to the lack of authigenic quartz, interparticle pores were rarely developed and its pore structure is mainly controlled by illite content.
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Charlaftis, Dimitrios, Stuart J. Jones, Katherine J. Dobson, Jonathan Crouch, and Sanem Acikalin. "Experimental study of chlorite authigenesis and influence on porosity maintenance in sandstones." Journal of Sedimentary Research 91, no. 2 (February 28, 2021): 197–212. http://dx.doi.org/10.2110/jsr.2020.122.
Full textAbstract:
ABSTRACT Chlorite is recognized as a key mineral for preserving reservoir quality in deeply buried sandstones, as chlorite coatings inhibit the nucleation of quartz overgrowths. A limited understanding of the mechanisms and conditions under which these authigenic chlorite coatings form prevents the accurate forward modeling of diagenesis and limits reservoir quality models critical to a wide range of geoscience applications. We present experimental data that show how authigenic chlorite grain coatings preserve porosity in deeply buried sandstone reservoirs, using a series of hydrothermal reactor experiments to simulate quartz cementation and capture the evolving porosity. To simulate reservoir evolution, berthierine-bearing sandstone samples (Lower Jurassic Cook Formation, Oseberg Field, 30/6-17R, Norway) were exposed to a silica-supersaturated Na2CO3 (0.1 M) solution for 72 hours at temperatures of between 100 and 250 °C. Quantification of the temperature-dependent changes in the volume of authigenic chlorite, the thickness and coverage of the clay coatings, and the sample porosity shows increases in chlorite volume (from ∼ 2% to ∼ 14%). This occurs by the transformation, of patchy amorphous berthierine into grain-coating Fe-chlorite cements through a mixture of the solid-state transformation and dissolution–precipitation mechanisms, siderite replacement, and direct precipitation on clay-free surfaces. With increasing temperature, the chlorite coatings increase from ∼ 3.8 μm to ∼ 5.4 μm thick and expand their grain surface coverage from ∼ 28% to ∼ 50%. The face-to-edge and face-to-face foliaceous structure of the clay coatings produced are morphologically similar to those observed in deeply buried sandstones. Only above temperatures of 175 °C is porosity preserved as a consequence of inhibition of quartz overgrowths and the generation of secondary porosity. Our quantitative approach enhances our knowledge regarding the temperature and mineral precursor influence on chlorite-coating authigenesis and therefore provides key insight for chlorite grain coatings for reservoir potential in sedimentary sequences greater than 2.5 km.
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Bristow, Thomas F., and Ralph E. Milliken. "Terrestrial perspective on authigenic clay mineral production in ancient Martian lakes." Clays and Clay Minerals 59, no. 4 (August 1, 2011): 339–58. http://dx.doi.org/10.1346/ccmn.2011.0590401.
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Herranz, Juan, and Manuel Pozo. "Authigenic Mg-Clay Minerals Formation in Lake Margin Deposits (the Cerro de los Batallones, Madrid Basin, Spain)." Minerals 8, no. 10 (September 20, 2018): 418. http://dx.doi.org/10.3390/min8100418.
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The Madrid Basin contains large and well developed deposits of Mg-clays of Miocene age. These were developed in an environment controlled by a lacustrine saline-alkaline environment with an arid or semi-arid climate, leading to large deposits of Mg-clays. This paper summarizes the study about the formation of Mg-clay minerals in the transition from mudflat lithofacies made-up of Mg-smectite to palustrine lithofacies where sepiolite is predominant. The samples collected in the field were characterized by XRD (X-Ray Diffaction) (bulk sample and clay fraction), examined using SEM (Scanning Electron Microscopy) and analyzed by XRF (X-Ray Fluorescence) and FTIR (Fourier Transform Infrared Spectroscopy). The results suggest that during the formation of these materials dissolution-precipitation, direct precipitation and recrystallization mechanisms intervened. The type of water present (runoff, lake and/or groundwater) is a key factor for the development of the different mineral phases. In the case of the study, the analyzed series goes from mudflat conditions with influence of runoff water to a palustrine environment. During this evolution, the influence of groundwater increases with time. This is reflected in the affinity between the samples analyzed and the presence of certain elements that could serve as indicators of changes between different media.
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Li, Fu Lai, Wen Shuai Li, Zhong Feng Duan, and Yan Deng. "Petrologic Characteristics of Dawsonite-Bearing Sandstones in Dongying Sag of Bohai Bay Basin, China." Advanced Materials Research 1010-1012 (August 2014): 1376–79. http://dx.doi.org/10.4028/www.scientific.net/amr.1010-1012.1376.
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A large number of dawsonite-bearing sandstones has been found in Dongying Sag of Bohai Bay basin. The petrological characteristics of these sandstones, such as the framework clastic composition, cements, authigenic minerals and diagenetic paragenesis succession are investigated by polarizing microscope, SEM, and Alizarin Red-S staining etc. The results show that these kinds of dawsonite-bearing sandstone are feldspathic sandstone or debris-feldspar sandstone with mainly fine or fine to medium particle size, poor to mediocre sorting features, poor psephicity and dot-line contact. The cements and authigenic minerals are dominated by overgrowth quartz, dawsonite, calcite, ferrocalcite, ankerite and clay minerals. The amount of dawsonite accounts for 15% by volume. The paragenesis sequence are illite/montmorillonite mixing layer, kaolinite, overgrowth quartz-calcite, ferrocalcite, dawsonite and ankerite.
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Laita, Elisa, Blanca Bauluz, Marcos Aurell, Beatriz Bádenas, and Alfonso Yuste. "Weathering events recorded in uppermost Hauterivian–lower Barremian clay-dominated continental successions from the NW Iberian Range: climatic vs. tectonic controls." Journal of Iberian Geology 48, no. 1 (December 1, 2021): 45–63. http://dx.doi.org/10.1007/s41513-021-00181-0.
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AbstractThe facies and clay mineral study of clay/marl-rich levels from the Torrelapaja Formation (latest Hauterivian–early Barremian, NW Iberian Range, NE Spain) allowed to establish the palaeoclimatic and palaeoenvironmental conditions under they were generated. The muddy levels and pisoids contained therein of two logs were sampled and studied by X-ray diffraction and optical and electron microscopy. A similar mineralogical upwards trend is recorded in both logs, with a decrease in calcite coupled with an increase in quartz and orthoclase content and constant proportions in goethite, hematite, diaspore, anatase, rutile, ilmenite, and clay mineral content. The lower muddy levels have higher kaolinite content than the upper levels, where illitic phases are the dominant clay minerals. Smectite and intergrowths of illitic phases and kaolinite are also detected upwards. The kaolinite and smectite textures indicate an authigenic origin, whereas the illitic phases are former phases acting as a substrate for kaolinite crystallization. Pisoids mineralogy and texture show an in-situ origin, but some are fractured, indicating reworking processes. The mineral association found in the muddy levels is characteristic of oxisols formed under warm and humid conditions. The upward decrease in kaolinite content is coeval with an increase in the illitic phases and quartz content, related to siliciclastic input, but is also coeval with the presence of authigenic smectite. This indicates a decrease in chemical weathering, not fully registered due to the siliciclastic contribution, which was possibly associated with a change to colder, drier conditions during the latest Hauterivian–early Barremian in the studied area.
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Martos-Villa, Rubén, M. Pilar Mata, Lynda B. Williams, Fernando Nieto, Xabier Arroyo Rey, and C. Ignacio Sainz-Díaz. "Evidence of Hydrocarbon-Rich Fluid Interaction with Clays: Clay Mineralogy and Boron Isotope Data from Gulf of Cádiz Mud Volcano Sediments." Minerals 10, no. 8 (July 23, 2020): 651. http://dx.doi.org/10.3390/min10080651.
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Clay dehydration at great depth generates fluids and overpressures in organic-rich sediments that can release isotopically light boron from mature organic matter, producing 10B-rich fluids. The B can be incorporated into the tetrahedral sites of authigenic illite during the illitization of smectite. Therefore, the crystal-chemical and geochemical characterization of illite, smectite or interlayered illite–smectite clay minerals can be an indicator of depth (temperature) and reactions with the basin fluids. The aim of this study was to determine the detailed clay mineralogy, B-content and isotopic composition in illite–smectite rich samples of mud volcanoes from the Gulf of Cádiz, in order to evaluate interactions of hydrocarbon-rich fluids with clays. Molecular modeling of the illite structure was performed, using electron density functional theory (DFT) methods to examine the phenomenon of B incorporation into illite at the atomic level. We found that it is energetically preferable for B to reside in the tetrahedral sites replacing Si atoms than in the interlayer of expandable clays. The B abundances in this study are high and consistent with previous results of B data on interstitial fluids, suggesting that hydrocarbon-related fluids approaching temperatures of methane generation (150 °C) are the likely source of B-rich illite in the studied samples.
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Goodchild, M. W., and J. H. McD Whitaker. "A petrographic study of the Rotliegendes Sandstone reservoir (Lower Permian) in the Rough Gas Field." Clay Minerals 21, no. 4 (October 1986): 459–77. http://dx.doi.org/10.1180/claymin.1986.021.4.04.
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AbstractThe diagenetic history of the Rotliegendes Sandstone reservoir in the Rough Gas Field was studied using thin-sections, XRD analyses and SEM. The Rotliegendes comprises a sequence of fine-grained fluvial sheet-flood sandstones and coarse, gravelly, low-sinuosity channel sandstones, with thin aeolian interbeds, overlain by a sequence of aeolian dune and interdune sandstones. Early, environmentally-related diagnesis (eogenesis) shows a marked variability with sedimentary facies. Within aeolian sandstones, poikilotopic anhydrite and fine, rhombic dolomite are preserved. Fluvially-derived sandstones typically contain infiltrated detrital clays and early authigenic mixed-layer clays, together with coarse, framework-displacive dolomite. Feldspars show varying degrees of alteration within all facies. These eogenetic features reflect patterns of groundwater movement during the Rotliegendes and early Zechstein. Mineral dissolution and precipitation were controlled by the chemistry of the groundwaters. Burial diagenetic (mesogenetic) features are superimposed on eogenetic cements. Authigenic clays have been converted to illitic clays. In addition, mesogenetic chlorite has formed and quartz and strongly ferroan dolomite cements are recognized. These minerals may be related to clay diagenesis within the underlying Carboniferous Coal Measures. Early, framework-supporting anyhdrite, and both phases of dolomite, have been partially dissolved, creating secondary porosity. This is attributed to the action of acidic porewaters, generated by the maturation of organic material within the Carboniferous. Post-dissolution kaolinite, gypsum and minor pyrite infill secondary pores. Gas emplacement from the Late Cretaceous onwards effectively halted further diagenetic reactions.
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Ho, Toan Minh, Phuong Kim Lieu, Thuy Thi Doan, and Phuong Thi Ngoc Bui. "Generation of authigenic clay minerals during diagenesis and their influences on porosity and permeability of Oligocene sandstone reservoir rocks, from a well in the west of Cuu Long basin." Science and Technology Development Journal 17, no. 3 (September 30, 2014): 21–26. http://dx.doi.org/10.32508/stdj.v17i3.1456.
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Porosity and permeability play a prerequisite role for hydrocarbon reservoirs and fluid flows, especially in sandstone reservoir rocks. The rocks with high porosity decrease down to lower porosity with increasing burial depth due to compaction, cementation and precipitation of authigenic minerals in pores from over saturated solution of minerals. The detailed study of the authigenic clay mineral formation in pore spaces of sandstone reservoir rocks is therefore crucial to estimate the degree of reservoir rock quality. In this study 20 sandstone cores taken from the interval burial depths of 3,700 m - 4,200 m from Oligocene sandstone sequence of a well in the West of the Cuu Long basin, offshore Vietnam, were analyzed by SEM and thin section. Authigenic clay minerals were formed due to temperature and chemistry changes and owing to dissolution of less stable minerals in these burial depths. Authigenic chlorite mineral appears quite abundantly and illite is less frequently. Chlorite was formed from the elements Al and Si, which were released from dissolved grains and Fe and Mg supplied from breakdown of the ferromagnesian minerals of rock fragments and matrix components into pore waters in the burial stage. Illite is associated with the expense of grain dissolution of feldspar, volcanic fragment. Chlorite mostly appears as a coating or mats comprising of small pseudo-hexagonal crystals arranged perpendicular to detrital grain surfaces. Grainrimming chlorites on quartz grain are responsible for the preservation of the porosity in the sandstones because they limit the formation of quartz overgrowth. Additionally fibrous or flaky illite bridging the pores between the grains creates permeability barriers to fluid flows through the sandstones. Thus illite significantly reduces the permeability but to lesser extent affect porosity. Locally, smectite mixes with illite or chlorite and is not abundant in the studied samples. It therefore has no significant impact on the porosity and permeability as well. The variations of the porosity and the permeability of the studied sandstones depend on the generated degree and the arranged patterns of chlorite and illite in pore spaces.
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Jeans, C. V. "Clay mineralogy of the Jurassic strata of the British Isles." Clay Minerals 41, no. 1 (March 2006): 187–307. http://dx.doi.org/10.1180/0009855064110198.
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AbstractThe nature and origin of the clay mineralogy of the Jurassic strata of the British Isles are described and discussed within their lithological and biostratigraphical framework using published and unpublished sources as well as 1800 new clay mineral analyses. Regional clay mineral variation is described systematically for the following formations or groups:England and Wales(i)Hettangian-Toarcian strata (Lias Group): Redcar Mudstone Fm.; Staithes Sandstone Fm.; Cleveland Ironstone Fm.; Whitby Mudstone Fm.; Scunthorpe Mudstone Fm.; Blue Lias Fm.; Charmouth Mudstone Fm.; Marlstone Rock Fm.; Dyrham Fm.; Beacon Limestone Fm.; Bridport Sand Fm.(ii)Aalenian-Bajocian (Inferior Oolite Group): Dogger Fm.; Saltwick Fm.; Eller Beck Fm.; Cloughton Fm.; Scarborough Fm.; Scalby Fm. (in part); Northampton Sand Fm.; Grantham Fm.; Lincolnshire Limestone Fm.; Rutland Fm. (in part); Inferior Oolite of southern England.(iii)Bathonian (Great Oolite Group): Scalby Fm. (in part); Rutland Fm. (in part); Blisworth Limestone Fm.; Great Oolite Group of southern England; Forest Marble Fm.; Cornbrash Fm. (in part).(iv)Callovian-Oxfordian: Cornbrash Fm. (in part); Kellaways Fm.; Oxford Clay Fm.; Corallian Beds and West Walton Beds; Ampthill Clay Fm.(v)Kimmeridgian-Tithonian: Kimmeridge Clay Fm.; Portland Sandstone Fm.; Portland Limestone Fm.; Lulworth Fm.; Spilsby Sandstone Fm. (in part). Scotland(vi)Hettangian-Toarcian: Broadfoot Beds, Dunrobin Bay Fm. Aalenian-Portlandian: Great Estuarine Group (Dunkulm, Kilmaluag and Studiburgh Fm.s); Staffin Shale Fm.; Brora Coal Fm.; Brora Argillaceous Fm.; Balintore Fm.; Helmsdale Boulder Beds (Kimmeridge Clay Fm.).Dominating the Jurassic successions are the great marine mudstone formations — the Lias Group, Oxford Clay, Ampthill Clay and Kimmeridge Clay. These are typically characterized by a detrital clay mineral assemblage of mica, kaolin and poorly defined mixed-layer smectite-mica-vermiculite minerals with traces of chlorite. Detailed evidence suggests that this assemblage is derived ultimately from weathered Palaeozoic sediments and metasediments either directly or by being recycled from earlier Mesozoic sediments. A potassium-bearing clay is a persistent component and formed at approximately the same time as the deposition of the host sediment, either in coeval soils or during very early diagenesis.At three periods during the deposition of the Jurassic (Bajocian-Bathonian, Oxfordian and late Kimmeridgian-Tithonian), the detrital clay assemblage was completely or partially replaced by authigenic clay mineral assemblages rich in kaolin, berthierine, glauconite or smectite minerals. Associated with these changes are major changes in the lithofacies, with the incoming of non-marine and proximal marine strata. The authigenic clay assemblages rich in kaolin and berthierine are generally restricted to the non-marine and very proximal marine beds, those rich in glauconite or smectite are typical of the marine lithofacies. Clay mineral assemblages containing vermiculite and mixed-layer vermiculite-chlorite sometimes occur in the non-marine and proximal marine facies. The causes of these major changes in lithofacies and clay mineralogy are discussed, and present evidence favours an important volcanogenic influence and not climatic control. It is suggested that the Bajocian-Bathonian, Oxfordian and Late Kimmeridgian-Tithonian were periods of enhanced volcanic activity, with centres probably located in the North Sea and linked to regional tectonic changes which caused major modifications of the palaeogeography of the British Isles. The most important of these changes was the development of the central North Sea Rift Dome during the Bajocian and Bathonian. Volcanic ash was widespread in both the non-marine and marine environments and its argillization under different conditions provided the wide range of authigenic clay mineral assemblages.Metre-scale clay mineral cyclicity is widespread in most of the Jurassic mudstone formations that have been examined in sufficient detail. The cyclicity is defined by systematic variations in the mica/ collapsible minerals (mixed-layer smectite-mica-vermiculite) ratio. This variation is unrelated to changes in lithology and its possible origins are discussed in detail using data from the Kimmeridge Clay provided by Reading University's contribution to the Rapid Global Geological Events (RGGE) Project.
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Matthews, J. C., B. Velde, and H. Johansen. "Significance of K-Ar ages of authigenic illitic clay minerals in sandstones and shales from the North Sea." Clay Minerals 29, no. 3 (September 1994): 379–90. http://dx.doi.org/10.1180/claymin.1994.029.3.09.
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AbstractPetrographic, X-ray diffraction, and microprobe analyses have been used to assess the significance of illite K-Ar ages from sandstones of two North Sea wells. Three closely spaced samples in one well from the upper Statfjord Formation yield similar ages (69-79 Ma) although the illites formed from different precursor minerals. Pore-filling illite in the upper Brent and the Upper Skagerrak Formations from a second well formed by replacing groundmass clays and other detrital minerals. The average layer charge and K+ content increase slightly with depth (0.69-0.80 K+) due to minor reaction and crystal growth during burial diagenesis. These K-Ar ages increase from 15 to 33 Ma within a 500 m depth interval. The K-Ar age vs. depth relationship for these samples corresponds to the burial rate during the middle Tertiary. In examples of extensive illitization of pore-filling clays in sandstones with little subsequent evolution of the clay minerals, the K-Ar ages indicate the age of diagenetic events.In contrast, illitic minerals in shales from the Skagerrak Formation in the second well yield an age (108 Ma) that is much older than the clays in the sandstones, but is still younger than stratigraphic age. The K-Ar ages from illitic clay in shales reported in the literature can get younger, older, or remain essentially unchanged with increasing depth. These age vs. depth trends reflect the complex interplay of crystal growth and dissolution during diagenesis, as well as probable contamination by non-recrystallized detrital illites. The K-Ar ages of illitic clays, therefore, evolve in a different manner in shales than in sandstones.
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Scotchman, Iain C. "Clay diagenesis in the Kimmeridge Clay Formation, onshore UK, and its relation to organic maturation." Mineralogical Magazine 51, no. 362 (October 1987): 535–51. http://dx.doi.org/10.1180/minmag.1987.051.362.08.
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AbstractConversion of randomly ordered illite-smectite to ordered illite-smectite in the Upper Jurassic Kimmeridge Clay Formation from the North Sea has been recorded in the literature as occurring within the ‘oil window’ and has been suggested as an indicator of oil source rock maturity. Studies of authigenic clay minerals in the fine fraction (>0.5 µm) of the Kimmeridge Clay Formation mudstones from fourteen locations along the UK onshore outcrop between Dorset and North Yorkshire show that they comprise mainly ordered illite-smectites. The onshore Kimmeridge Clay section is organically immature, suggesting that the illite-smectite ordering reaction cannot be extrapolated between basins as an inorganic indicator of ‘oil window’ levels of maturity. These results also have important implications in source rock hydrocarbon expulsion and migration models which involve shale dewatering as a flushing agent. However, dewatering of shales may aid migration as it could cause fracturing of the shale bands separating the organic-rich layers within the source rock, prior to hydrocarbon generation.
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Herranz, Juan Emilio, and Manuel Pozo. "Sepiolite and Other Authigenic Mg-Clay Minerals Formation in Different Palustrine Environments (Madrid Basin, Spain)." Minerals 12, no. 8 (August 3, 2022): 987. http://dx.doi.org/10.3390/min12080987.
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Lithofacies belonging to mud-flat and palustrine deposits (lake margin) in the Miocene of the Madrid Basin (Spain) have been studied. Four lithofacies corresponding to mud flat (1 and 3) and palustrine (2 and 4) deposits have been differentiated. Units 1 and 3 consist mainly of mudstones and carbonates (calcretes and diolocretes). The clay fraction is dominated by trioctahedral smectite (up to 79%) with illite and kaolinite as minor components. The d(060) spacing value shows reflections at 1.52 and 1.50 Å indicating also the presence of dioctahedral phyllosilicates. Unit 2 consists predominantly of lutites (claystones), locally with carbonate and chert nodules. The clay fraction is dominated by sepiolite (up to 96%) with variable contents of smectite and subordinate illite. The d(060) spacing value shows reflections at 1.51 and 1.52 Å indicating trioctahedral clay minerals. Unit 4 consists mostly of carbonates (limestones) with mudstone and lutite inserts. The clay fraction shows different contents of sepiolite, palygorskite and dioctahedral smectite. The analysis of a selection of trace elements (Cr, Co, Th, La, Sc) has allowed us to determine the characteristics of the source area as dioritic, somewhat different from those of the nearby materials from the Batallones sector. Sepiolite shows FWHM values ranging between 0.68 and 1.10 (2θ), indicating “low crystallinity sepiolite”. Differences in the conditions of formation of magnesian smectite and palygorskite have been observed in the mud-flat and palustrine deposits. The formation of sepiolite mainly by neoformation in palustrine deposits with different hydrochemistry is remarkable, leading to differences in fibre size and crystallinity of the fibrous clay mineral. Authigenic transformation processes from previous Al-rich phases would be responsible for the formation of saponite and palygorskite in mud flat and palustrine environments, with different pH conditions.
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Rudmin, Maxim, Aleksey Ruban, Oleg Savichev, Aleksey Mazurov, Aigerim Dauletova, and Olesya Savinova. "Authigenic and Detrital Minerals in Peat Environment of Vasyugan Swamp, Western Siberia." Minerals 8, no. 11 (November 1, 2018): 500. http://dx.doi.org/10.3390/min8110500.
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Studies of mineral-forming processes in modern peat bogs can shed light on metal concentrations and their cycling in similar environments, especially in geological paleoanalogs. In terms of the mineralogical and geochemical evolution of peat bog environments, the Vasyugan Swamp in Western Siberia is a unique scientific object. Twelve peat samples were collected from the Vasyugan Swamp up to the depth of 275 cm at 25 cm intervals. The studied peat deposit section is represented by oligotrophic (0–100 cm), mesotrophic (100–175 cm), and eutrophic (175–275 cm) peat, and this is underlain by basal sediments (from 275 cm). About 30 minerals were detected using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Raman spectroscopy. The observed minerals are divided into detrital, clay, and authigenic phases. The detrital minerals found included quartz, feldspar, ilmenite, rutile, magnetite, zircon, and monazite. When passing from basal to oligotrophic bog sediments, the clay minerals changed from illite-smectite to kaolinite. Authigenic minerals are represented by carbonates (calcite and dolomite), iron (hydro-)oxides, galena, sphalerite, pyrite, chalcopyrite, Zn-Pb-S mineral, barite, baritocelestine, celestine, tetrahedrite, cassiterite, REE phosphate, etc. The regular distribution of mineral inclusions in peat is associated with the (bio)geochemical evolution of the environment. The formation of authigenic Zn, Pb and Sb sulfides is mainly confined to anaerobic conditions that exist in the eutrophic peat and basal sediments. The maximum amount of pyrite is associated with the interval of 225–250 cm, which is the zone of transition from basal sediments to eutrophic peat. The formation of carbonate minerals and the decreasing concentration of clay in the association with local sulfide formation (galena, sphalerite, chalcopyrite, stibnite) begins above this interval. The peak of specific carbonation appears in the 125–150 cm interval of the mesotrophic peat, which is characterized by pH 4.9–4.5 of pore water. Kaolinite is the dominant clay mineral in the oligotrophic peat. Gypsum, galena, chalcopyrite, sphalerite, and relicts of carbonate are noted in association with kaolinite. Changes in oxygen concentrations are reflected in newly formed mineral associations in corresponding intervals of the peat. This can be explained by the activity of microbiological processes such as the anaerobic oxidation of methane (AOM) and bacterial sulfate reduction (BSR), expressed in specific carbonatization (100–225 cm) and sulfidization (175–250 cm), respectively.
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Zhang, Xu (Yvon), Jérôme Gaillardet, Laurie Barrier, and Julien Bouchez. "Li and Si isotopes reveal authigenic clay formation in a palaeo-delta." Earth and Planetary Science Letters 578 (January 2022): 117339. http://dx.doi.org/10.1016/j.epsl.2021.117339.
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