The influence of benthic diatoms on the textures of carbonate-coated grains from a fluvial tufa spring in northern California

2020 ◽  
Vol 90 (11) ◽  
pp. 1601-1613
Author(s):  
Hannah P. Boelts ◽  
Yadira Ibarra ◽  
Clive Hayzelden
Keyword(s):  
Pore Space ◽  
Strong Positive Correlation ◽  
Northern California ◽  
Threshold Size ◽  
Fine Grained ◽  
Henry Cowell ◽  
Marine Carbonate ◽  
Pore Area ◽  
Freshwater Spring ◽  
Imagej Software

ABSTRACT Diatoms are common in terrestrial freshwater carbonate environments, but their influence on the resulting carbonate texture and porosity remains unquantified. This study investigates the effect of diatoms on the textural variability and syndepositional porosity of spring-associated carbonate coated grains from a freshwater spring in Henry Cowell State Park, northern California, USA. Carbonate coated grains (n = 60) were collected from the distal-most pool of the spring (∼ 300 m from the spring source) and the porosity of the 1 cm diameter fraction (n = 20) was determined using the ImageJ software by adjusting the threshold size for pores > 1000 μm2. Results reveal a strong positive correlation between the number of pores and the number of diatoms examined in each coated grain (r = 0.77). There is a moderate positive relationship between the length of the largest diatom and the minor-axis diameter of a best-fit ellipse of its corresponding pore (r = 0.60). The total pore area for pores associated with at least one diatom was significantly greater than the total pore area of pores that did not enclose diatom frustules (t = 1.80, p < 0.05). Textural observations show that fine-grained laminated textures contain fewer diatoms than the porous textures, suggesting that diatoms disrupt lamination continuity by introducing pore space. These findings have implications for the influence of diatoms on the syndepositional porosity of carbonate rocks from the Cretaceous to Recent and may help explain textural differences between modern marine carbonate microbialites and their Precambrian counterparts.

scholarly journals A model for coupled electro-hydro-mechanical processes in fine grained soils accounting for gas generation and transport

2010 ◽  
Vol 82 (1) ◽  
pp. 169-193 ◽  
Author(s):  
Claudio Tamagnini ◽  
Cristina Jommi ◽  
Fabio Cattaneo
Keyword(s):  
Pore Space ◽  
Transport Coefficients ◽  
Gas Production ◽  
Degree Of Saturation ◽  
Coupled Processes ◽  
Gas Generation ◽  
Fine Grained ◽  
Clayey Silt ◽  
Waste Containment Systems ◽  
The Impact

A theoretical and numerical model is developed for the quantitative analysis of coupled processes taking place in active waste containment systems, such as electrokinetic barriers or fences, in which alow intensity DC current is circulated across the clay barrier to move polar and non-polar contaminants. A novel feature of the proposed approach is the allowance for the presence of air in the pore space. Under unsaturated conditions, all transport coefficients involved in the electrokinetic process are strongly dependent on the degree of saturation of pore liquid. In order to assess the predictive capability of the proposed theory and to appreciate the impact of gas production at the electrodes, a series of numerical simulations of simple onedimensional electrokinetic tests have been performed. The results of the simulations compare reasonably well with data obtained from laboratory experiments performed on an illitic clayey silt. The numerical results indicate that the impact of gas production at the electrodes can be significant, even in low-intensity and short-duration treatments.

scholarly journals Combining spectral induced polarization with X-ray tomography to investigate the importance of DNAPL geometry in sand samples

Geophysics ◽  
2019 ◽  
Vol 84 (3) ◽  
pp. E173-E188 ◽  
Author(s):  
Sara Johansson ◽  
Matteo Rossi ◽  
Stephen A. Hall ◽  
Charlotte Sparrenbom ◽  
David Hagerberg ◽  
...  
Keyword(s):  
Image Analysis ◽  
Pore Space ◽  
Total Concentration ◽  
Data Interpretation ◽  
Induced Polarization ◽  
X Ray ◽  
Fine Grained ◽  
Surface Areas ◽  
Spectral Induced Polarization ◽  
The Individual

Although many studies have been performed to investigate the spectral induced polarization (SIP) response of nonaqueous phase liquid (NAPL)-contaminated soil samples, there are still many uncertainties in the interpretation of the data. A key issue is that altered pore space geometries due to the presence of a NAPL phase will change the measured IP spectra. However, without any information on the NAPL distribution in the pore space, assumptions are necessary for the SIP data interpretation. Therefore, experimental data of SIP signals directly associated with different NAPL distributions are needed. We used high-resolution X-ray tomography and 3D image processing to quantitatively assess NAPL distributions in samples of fine-grained sand containing different concentrations of tetrachloroethylene and link this to SIP measurements on the same samples. The total concentration of the sample constituents as well as the volumes of the individual NAPL blobs were calculated and used for the interpretation of the associated SIP responses. The X-ray tomography and image analysis showed that the real sample properties (porosity and NAPL distributions) differed from the targeted ones. Both contaminated samples contained less NAPL than expected from the manual sample preparation. The SIP results showed higher real conductivity and lower imaginary conductivity in the contaminated samples compared to a clean sample. This is interpreted as an effect of increased surface conductivity along interconnected NAPL blobs and decreased surface areas in the samples due to NAPL blobs larger than and enclosing grains. We conclude that the combination of SIP, X-ray tomography, and image analysis is a very promising approach to achieve a better understanding of the measured SIP responses of NAPL-contaminated samples.

scholarly journals Botryoidal and Spherulitic Aragonite in Carbonates Associated with Microbial Mats: Precipitation or Diagenetic Replacement Product?

2021 ◽  
Vol 9 ◽  
Author(s):  
Yuzhu Ge ◽  
Giovanna Della Porta ◽  
Chelsea L. Pederson ◽  
Stephen W. Lokier ◽  
René Hoffmann ◽  
...  
Keyword(s):  
Extracellular Polymeric Substances ◽  
Microbial Mats ◽  
Salt Lake ◽  
Pore Space ◽  
Depositional Environments ◽  
Formation Mechanisms ◽  
Microbial Biofilms ◽  
Marine Carbonate ◽  
Fluid Properties ◽  
Underlying Mechanisms

Similar carbonate fabrics may result from different pathways of precipitation and diagenetic replacement. Distinguishing the underlying mechanisms leading to a given carbonate fabric is relevant, both in terms of an environmental and diagenetic interpretation. Prominent among carbonate fabrics are aragonite botryoids and spherulites, typically interpreted as direct seawater precipitates and used as proxies for fluid properties and depositional environments. This study investigated μm to mm-scale Holocene botryoidal and spherulitic aragonite from marine and non-marine carbonate settings associated with microbial mats, and reports two distinct formation mechanisms: 1) early diagenetic replacement, and 2) primary precipitation via nanocrystal aggregation. In the intertidal microbial mats of Khawr Qantur (Abu Dhabi), botryoidal and spherulitic aragonite are replacement products of heavily micritized bioclasts. To form the botryoidal and spherulitic aragonite, skeletal rods and needles, resulting from disintegration of micritized bioclasts, recrystallize into nanocrystals during early marine diagenesis. These nanocrystals then grow into fibrous crystals, forming botryoidal and spherulitic aragonite. In the lacustrine microbial bioherms of the hypersaline Great Salt Lake (United States) and in the hydrothermal travertines of Bagni San Filippo (Italy), botryoidal and spherulitic aragonite evolve from nanocrystals via precipitation. The nanocrystals are closely associated with extracellular polymeric substances in microbial biofilms and aggregate to form fibrous crystals of botryoidal and spherulitic aragonite. The studied fabrics form a portion of the bulk sediment and show differences in terms of their formation processes and petrological features compared to the often larger (few mm to over 1 m) botryoidal and spherulitic aragonite described from open-marine reefal cavities. Features shown here may represent modern analogues for ancient examples of carbonate depositional environments associated with microbialites. The implication of this research is that botryoidal and spherulitic aragonite associated with microbial mats are relevant in paleoenvironmental interpretations, but must be combined with a detailed evaluation of their formation process. Care must be taken as the term “botryoidal and spherulitic aragonite” may in fact include, from the viewpoint of their nucleation and formation mechanism, similar fabrics originated from different pathways. At present, it seems unclear to which degree the μm to mm-scale botryoids and spherulites described here are comparable to their cm-to dm-size counterparts precipitated as cements in the open pore space of reefal environments. However, it is clear that the investigation of ancient botryoidal and spherulitic aragonite must consider the possibility of an early diagenetic replacement origin of these precipitates.

STATISTICAL REPRESENTATION OF POROUS MEDIUM TECHNOLOGICAL COEFFICIENTS FORMULAS

2021 ◽  
Author(s):  
В.Г. ЖУКОВ ◽  
В.М. ЧЕСНОКОВ ◽  
Н.Д. ЛУКИН
Keyword(s):  
Porous Medium ◽  
Pore Space ◽  
Random Variable ◽  
Homogeneous System ◽  
Characteristic Size ◽  
Fine Grained ◽  
Porosity And Permeability ◽  
The Difference ◽  
Experimental Values ◽  
Relationship Of

В различных отраслях промышленности используют материалы, представляющие собой пористые среды, от которых во многом зависит эффективность процесса производства и, следовательно, качество и стоимость продукта. Наиболее распространенными в пищевых производствах являются процессы фильтрационного разделения, сушки и фильтрационной пропитки. Их решение обычно строится на основе технологических коэффициентов пористости и проницаемости, величины которых определяют относительно простыми экспериментальными методиками для реальной полиразмерной пористой среды. В этом случае невозможно аналитически учесть различие скоростей фильтрации в порах разного размера, изменение влажности пористого материала в процессах сушки или вытеснение заполняющей поры подвижной среды. Поэтому для решения этой проблемы необходим учет статистического характера распределения пор по их размерам. В настоящей работе разработано аналитическое представление формул коэффициентов прерывистости, просветности, пористости и проницаемости, основанное на статистических функциях распределения пор по размерам. В качестве объекта исследования рассматривали пористую среду из мелкозернистого или консолидированного материала, поровое пространство которого состояло из полиразмерного ансамбля сквозных поровых каналов в виде статистически упорядоченной изотропной однородной системы сообщающихся пор случайных, весьма малых размеров. Методика получения формул была основана на статистической формуле логнормального распределения пор характерного размера случайной величины и теореме о взаимосвязи технологических коэффициентов для описания свойств пористой среды. Расчеты проводили с использованием программы Mathcad. Правильность расчетных формул подтверждена совпадением предельных точек расчетных графиков с точками гистограмм, построенных на основе экспериментальных значений коэффициентов. In various industries, materials are used that are porous media, on which the efficiency of the production process and, consequently, the quality and cost of the product largely depend. The most common processes in food production are filtration separation, drying and filtration impregnation. Their solution is usually based on the technological coefficients of porosity and permeability, the values of which are determined by relatively simple experimental methods for a real poly-dimensional porous medium. In this case, it is impossible to analytically take into account the difference in filtration rates in pores of different sizes, the change in the moisture content of the porous material during drying, or the displacement of the mobile medium filling the pores. Therefore to solve this problem, it is necessary to take into account the statistical nature of the distribution of pores by their size. In this paper an analytical representation of the formulas for the coefficients of discontinuity, transparency, porosity, and permeability is developed based on the statistical functions of the pore size distribution. The object of the study was a porous medium made of fine-grained or consolidated material, the pore space of which consisted of a poly-dimensional ensemble of through pore channels in the form of a statistically ordered isotropic homogeneous system of communicating pores of random, very small sizes. The method of obtaining formulas was based on the statistical formula of the lognormal distribution of pores of the characteristic size of a random variable and the theorem on the relationship of technological coefficients for describing the properties of a porous medium. The calculations were performed using the Mathcad program. The correctness of the calculated formulas is confirmed by the coincidence of the limit points of the calculated graphs with the points of the histograms constructed on the basis of the experimental values of the coefficients.

Red Sea Holocene carbonates: Windward platform margin and lagoon near Al-Wajh, northern Saudi Arabia

2021 ◽  
Vol 91 (8) ◽  
pp. 847-875
Author(s):  
D. Mark Steinhauff ◽  
Abduljaleel Abubshait ◽  
Sam J. Purkis
Keyword(s):  
Red Sea ◽  
Pore Space ◽  
Carbonate Platforms ◽  
Rift Basins ◽  
Thin Sections ◽  
Fine Grained ◽  
Platform Margin ◽  
Lagoon Sediment ◽  
Primary Porosity ◽  
Reservoir Potential

ABSTRACT Analysis of Holocene sedimentary seascape is focused on the Red Sea windward Al-Wajh platform margin, its central lagoon, and nearby isolated platforms based on data that include mapped ecological facies (habitats), water depths, grain sizes, and allochem types and abundances determined from thin sections. On this basis, a depositional model applicable to Red Sea Plio-Pleistocene and other ancient icehouse carbonate platforms is presented. The model highlights favorable reservoirs in analogous ancient systems to include coral crests and columnar framework habitats with primary porosity developed in boundstone lithologies and windward platform margins to contain considerable open pore space, including cavernous openings, of which not all should be anticipated to be occluded with marine cements and sediments. Meteoric diagenesis is expected to be minor as limited freshwater is available due to extreme aridity, but may play a role during glaciation. Most habitats have potential for secondary (enhanced) porosity resulting from dissolution of aragonite skeletons, particularly mollusk shells and calcareous coral (Scleractinia) endoskeletons. Central-lagoon habitats are expected to have the least favorable reservoir potential of environments considered because they are dominated by peloids. Central-lagoon sediment differs from other published localities, having higher peloid abundances, greater peloid distribution, and little or no association with Halimeda and quartz grains. Under the likely scenario that platform-interior sediments are completely bioturbated and comprise peloid-rich, grain-dominated fabrics, with many smaller peloids (most of them likely fecal pellets) at or near 4 μm in size (i.e., mud fraction), it is possible that grain size will control pore size once the considered deposits are lithified. If so, platform-interior sediments will lithify as mudstones, wackestones, or very fine-grained grainstones, an outcome which might otherwise be unexpected given the abundance of coarse peloid grains. The Al-Wajh platform is compared with 15 Holocene analogs and found to be unique with respect to rift-margin type, restricted-marine circulation, in having a lagoon with high peloid content, and lack of karst. In further comparison with ancient reservoir analogs, two greenhouse and four icehouse, it compares favorably to icehouse platforms deposited in rift basins with respect to mineralogy of deposition, meter-scale cycle thicknesses, and general peloid content and distribution. It provides a snapshot as to how an icehouse platform might have nucleated and attached along an active rift margin; it is a broadly applicable carbonate analog for the Red Sea Plio-Pleistocene and similar icehouse, rift basins.

Evolution of mineral assemblages and textures from sediment through hornfels in the Salton Sea Geothermal Field: Direct crystallization of phyllosilicates in a hydrothermal-metamorphic system

Clay Minerals ◽  
2003 ◽  
Vol 38 (1) ◽  
pp. 113-126 ◽  
Author(s):  
G. Giorgetti ◽  
M. P. Mata ◽  
D. R. Peacor
Keyword(s):  
Metamorphic Rock ◽  
Pore Space ◽  
Alkali Feldspar ◽  
Geothermal Field ◽  
Time Dependent ◽  
Salton Sea ◽  
Irregular Domains ◽  
Direct Crystallization ◽  
Fine Grained ◽  
Mineral Assemblages

AbstractMicroanalytical data on Plio-Pleistocene sediments from a Salton Sea Geothermal Field well define the evolution of textures and mineral assemblages from sediment to metamorphic rock in an open hydrothermal system.At shallow depths detrital grains occur within a fine-grained matrix of I-S and illite. As depth and temperature increase, grains lose their detrital characteristics; they subsequently form a continuous intergrown array of irregular domains, with phyllosilicates occupying the progressively decreasing pore space.Illite and chlorite are authigenic phyllosilicates down to 2500 m, where biotite occurs. Authigenic phyllosilicates occur as subhedral crystals (200 –600 Å thick). Alkali feldspar has end-member compositions, implying exchange of alkalis with convected fluids. Changes in texture imply dissolution of detrital phases and neocrystallization of authigenic phyllosilicates directly from pore fluids. Changes with depth are not time-dependent for phyllosilicates: they formed simultaneously at all depths as a result of a single hydrothermal event in an open system.

The role of clay minerals in influencing porosity and permeability characteristics in the Bridport Sands of Wytch Farm, Dorset

Clay Minerals ◽  
1982 ◽  
Vol 17 (1) ◽  
pp. 41-54 ◽  
Author(s):  
K. A. Morris ◽  
C. M. Shepperd
Keyword(s):  
Clay Minerals ◽  
Mixed Layer ◽  
Oil Recovery ◽  
Pore Space ◽  
Water Injection ◽  
Lower Jurassic ◽  
Core Material ◽  
Permeability Characteristics ◽  
Fine Grained ◽  
Porosity And Permeability

AbstractThe Bridport Sands is a widespread marine sandstone of Lower Jurassic age found in much of southern England. It is a very fine grained, moderately sorted quartz-arenite and is characterized by the alternation of friable and hard calcareous-cemented layers. The sands form the upper reservoir in the Wytch Farm Field, Dorset, which is currently producing at the rate of around 4000 barrels per day. Investigation of core material to assess the suitability of water injection for gas/oil recovery has shown that significant reductions of liquid permeability compared to air permeability occur. These reductions vary from 30% or less in the best quality reservoir to more than 70% in low-permeability sandstones. Clay minerals in the Bridport Sands comprise mainly kaolinite and mixed-layer clays of both the illite-chlorite and illite-smectite types. Small amounts of vermiculite and chlorite also occur. The kaolinite is found as loosely-attached, discrete particles, whilst the mixed-layer clays form patchy pore linings. The permeability reductions may be explained by: (i) the adsorption of water and expansion of poorly-crystalline mixed-layer illite-smectites causing blockage of pore space (this reduction is largely reversible) and (ii) the physical movement of authigenic kaolinite crystal aggregates blocking pore-throats (this reduction is largely non-reversible). The pore-size distribution, clay particle sizes, the distribution of the clays within the pore space, and the composition of the clays are all important factors in controlling porosity/permeability relationships and permeability reductions in the friable reservoir intervals in the Bridport Sands.

scholarly journals Limestones of the Uk Formation (Upper Riphean, the Southern Urals): Effect of contamination and diagenetic fluids on the distribution of rare-earth elements and yttrium

LITOSFERA ◽  
2021 ◽  
Vol 21 (1) ◽  
pp. 23-31
Author(s):  
A. V. Maslov
Keyword(s):  
Trace Elements ◽  
Carbonate Rocks ◽  
Southern Urals ◽  
Strong Positive Correlation ◽  
The Southern Urals ◽  
Positive Correlation ◽  
Fine Grained ◽  
Upper Riphean ◽  
Diagenetic Fluids ◽  
The Uk

Research subject. A study was conducted into the geochemical features of various lithotypes of carbonate rocks (granular and clastic limestones, limestones with planar, planar-columnar and columnar stromatolites) from the upper subformation of the Uk Formation. This formation crowns the Upper Riphean Karatau Group on the Western slope of the Southern Urals (Bashkir meganticlinorium). Material and methods. The research material was two collections of carbonate rocks (11 and 32 samples), the general geochemical features of which were previously considered in publications in 2019. The main research method was the analysis of the correlation relationships of the main rock-forming components, trace elements and their indicator relationships. Research results. It was established that all lithotypes are characterized by a significant content of both the main rock-forming components and the trace elements that make up the insoluble residue/fine-grained terrigenous admixture. This suggests that the area of accumulation of carbonate sediments was located near the continent, which served as a source of a significant amount of fine-grained/clay suspension. Conclusions. A strong positive correlation was observed between K2O and REE in the carbonate rocks of the Upper Uk Subformation, and a strong negative correlation was observed between REE and CaO. This suggests that the REE content in carbonate rocks is controlled mainly by terrigenous/clay admixture. A positive correlation is also observed between REE and Th, Zr, and Al2O3. All this shows that REE in carbonate rocks are mainly present in clay admixtures. The correlation coefficient between Ce/Ce* and (Dy/Sm)N is 0.20, while this coefficient for Eu/Eu* and (Pr/Sm)N equals 0.12. Thus, a definite conclusion about the effect of diagenetic fluids on the distribution of REE cannot be made. The data obtained show that the distribution of REE and Y in our collection of carbonate rocks of the Upper subformation of the Uk Formation of the Southern Urals is controlled mainly by clay admixtures.

Provenance and depositional environment of organic-rich calcareous black shale of the Late Ordovician Macasty Formation, western Anticosti Basin, eastern Canada

2019 ◽  
Vol 56 (3) ◽  
pp. 321-334 ◽  
Author(s):  
Keiko Hattori ◽  
André Desrochers ◽  
Janice Pedro
Keyword(s):  
Depositional Environment ◽  
Pore Space ◽  
Bulk Composition ◽  
Explosive Volcanism ◽  
Late Ordovician ◽  
Source Rocks ◽  
Eastern Canada ◽  
Fine Grained ◽  
Taconic Orogeny ◽  
Calcite Cement

The organic-rich Macasty shale in the Gulf of St. Lawrence was deposited in the Late Ordovician during the Taconic orogeny. The orogeny involved explosive volcanism and thrusting of allochthonous rocks in the eastern margin of North America. Neodymium isotope compositions of the shale show that the provenance is predominantly Grenvillian granite–gneissic rocks, which were widely exposed north of the basin, with little contribution from Taconic igneous rocks. The bulk composition and the presence of detrital kaolinite suggest that the Grenvillian source rocks underwent intense weathering before erosion. Fine-grained detritus was deposited in the Anticosti Basin, where abundant organic activity kept the sediment–water interface under anoxic conditions. This proposed interpretation is supported by the enrichment of redox-sensitive elements, such as As, V, and U, and by high δ34S for pyrite. Calcite cement formed in the pore space of sediments during the diagenesis at temperatures below 60 °C. The low-temperature diagenetic conditions are consistent with the preservation of abundant organic matter in the shale.

Attenuation in fine‐grained marine sediments: Extension of the Biot‐Stoll model by the “effective grain model” (EGM)

Geophysics ◽  
1997 ◽  
Vol 62 (5) ◽  
pp. 1465-1479 ◽  
Author(s):  
Klaus C. Leurer
Keyword(s):  
Clay Minerals ◽  
Marine Sediments ◽  
Solid Phase ◽  
Pore Space ◽  
Two Phase ◽  
Flow Process ◽  
Swelling Clay ◽  
Fine Grained ◽  
Grain Model ◽  
Swelling Clay Minerals

It is postulated that the presence of swelling clay minerals in unconsolidated fine‐grained saturated marine sediments leads to deviations from the normally assumed ideal elasticity of the solid phase. In the proposed “effective grain model” (EGM), the elastic grain material is consequently replaced by an effective medium made up of a homogeneous elastic mineral phase that is isotropically interspersed with cylindrical, “penny‐shaped” inclusions of low aspect ratio representing the intracrystalline water layers in the swelling clay minerals. The two‐phase nature of the grain material thus specified results in a wave‐energy consuming squirt‐flow process from the inclusions into the pore space. Introducing the EGM into the Biot‐Stoll model (BSM) via the complex bulk modulus of the dissipative grain material leads to a better fit to literature data on the attenuation of compressional waves than does the original BSM alone. Since swelling clay minerals occur in nearly all clay‐bearing sediments, it is concluded that the attenuation mechanism of the EGM may represent a universal contribution to the overall intrinsic anelasticity of unconsolidated fine‐grained saturated marine sediments in the frequency range from a few kilohertz to about 1 MHz.

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