scholarly journals Structural Control on Clay Mineral Authigenesis in Faulted Arkosic Sandstone of the Rio do Peixe Basin, Brazil

Minerals ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 408 ◽  
Author(s):  
Ingrid Maciel ◽  
Angela Dettori ◽  
Fabrizio Balsamo ◽  
Francisco Bezerra ◽  
Marcela Vieira ◽  
...  
Keyword(s):  
Clay Minerals ◽  
Clay Mineral ◽  
Structural Control ◽  
Fault Zones ◽  
High Porosity ◽  
Deformation Bands ◽  
X Ray Diffraction ◽  
Complex Settings ◽  
Feldspar Dissolution ◽  
Low Porosity

Clay minerals in structurally complex settings influence fault zone behavior and characteristics such as permeability and frictional properties. This work aims to understand the role of fault zones on clay authigenesis in arkosic, high-porosity sandstones of the Cretaceous Rio do Peixe basin, northeast Brazil. We integrated field, petrographic and scanning electron microscopy (SEM) observations with X-ray diffraction data (bulk and clay-size fractions). Fault zones in the field are characterized by low-porosity deformation bands, typical secondary structures developed in high-porosity sandstones. Laboratory results indicate that in the host rock far from faults, smectite, illite and subordinately kaolinite, are present within the pores of the Rio do Peixe sandstones. Such clay minerals formed after sediment deposition, most likely during shallow diagenetic processes (feldspar dissolution) associated with meteoric water circulation. Surprisingly, within fault zones the same clay minerals are absent or are present in amounts which are significantly lower than those in the undeformed sandstone. This occurs because fault activity obliterates porosity and reduces permeability by cataclasis, thus: (1) destroying the space in which clay minerals can form; and (2) providing a generally impermeable tight fabric in which external meteoric fluid flow is inhibited. We conclude that the development of fault zones in high-porosity arkosic sandstones, contrary to other low-porosity lithologies, inhibits clay mineral authigenesis.

scholarly journals Porosity model and pore evolution of transitional shales: an example from the Southern North China Basin

2020 ◽  
Vol 17 (6) ◽  
pp. 1512-1526
Author(s):  
Xiao-Guang Yang ◽  
Shao-Bin Guo
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Clay Minerals ◽  
Clay Mineral ◽  
Specific Surface Area ◽  
Mineral Content ◽  
High Specific Surface Area ◽  
High Porosity ◽  
Mechanical Compaction ◽  
Pore Evolution

AbstractThe evolution of shale reservoirs is mainly related to two functions: mechanical compaction controlled by ground stress and chemical compaction controlled by thermal effect. Thermal simulation experiments were conducted to simulate the chemical compaction of marine-continental transitional shale, and X-ray diffraction (XRD), CO2 adsorption, N2 adsorption and high-pressure mercury injection (MIP) were then used to characterize shale diagenesis and porosity. Moreover, simulations of mechanical compaction adhering to mathematical models were performed, and a shale compaction model was proposed considering clay content and kaolinite proportions. The advantage of this model is that the change in shale compressibility, which is caused by the transformation of clay minerals during thermal evolution, may be considered. The combination of the thermal simulation and compaction model may depict the interactions between chemical and mechanical compaction. Such interactions may then express the pore evolution of shale in actual conditions of formation. Accordingly, the obtained results demonstrated that shales having low kaolinite possess higher porosity at the same burial depth and clay mineral content, proving that other clay minerals such as illite–smectite mixed layers (I/S) and illite are conducive to the development of pores. Shales possessing a high clay mineral content have a higher porosity in shallow layers (< 3500 m) and a lower porosity in deep layers (> 3500 m). Both the amount and location of the increase in porosity differ at different geothermal gradients. High geothermal gradients favor the preservation of high porosity in shale at an appropriate Ro. The pore evolution of the marine-continental transitional shale is divided into five stages. Stage 2 possesses an Ro of 1.0%–1.6% and has high porosity along with a high specific surface area. Stage 3 has an Ro of 1.6%–2.0% and contains a higher porosity with a low specific surface area. Finally, Stage 4 has an Ro of 2.0%–2.9% with a low porosity and high specific surface area.

Quantitative X-ray diffraction analysis using clay mineral standards extracted from the samples to be analysed

Clay Minerals ◽  
1967 ◽  
Vol 7 (1) ◽  
pp. 79-90 ◽  
Author(s):  
Ronald J. Gibbs
Keyword(s):  
Diffraction Analysis ◽  
Clay Minerals ◽  
Clay Mineral ◽  
Internal Standard ◽  
Ethanol Solution ◽  
X Ray Diffraction ◽  
X Ray ◽  
Density Separation ◽  
Calibration Curves ◽  
Differential Settling

AbstractIn the quantitative X-ray diffraction analysis of a series of samples, the problems arising from the variable compositions and degrees of crystallinity of clay minerals were overcome to a great extent by the use of standards extracted from the samples. Procedures are given for separation of the montmorillonite standard by differential settling of Na-montmorillonite solvated in an ethanol solution and for isolation of the kaolinite, mica, and chlorite standards by density separation of their Na-forms in thallous formate.Calibration curves were prepared from the X-ray diffractograms obtained for series of known mixtures of Ca-forms of the standards and the internal standard boehmite using both powder and smear-oriented mounting techniques.

Thermogravimetry/evolved water analysis (TG/EWA) combined with XRD for improved quantitative whole-rock analysis of clay minerals in sandstones

Clay Minerals ◽  
1995 ◽  
Vol 30 (1) ◽  
pp. 27-38 ◽  
Author(s):  
D. M. Thornley ◽  
T. J. Primmer
Keyword(s):  
Clay Minerals ◽  
Clay Mineral ◽  
Water Analysis ◽  
Infrared Detector ◽  
Size Fraction ◽  
Xrd Analysis ◽  
X Ray Diffraction ◽  
Northern North Sea ◽  
Rock Analysis

AbstractCurrent methods of quantitative whole-rock clay mineral analysis of sandstones often provide little more than an estimate of clay mineral abundances, especially where the total clay mineral content is <10 wt% of the sandstone. More accurate determinations of clay mineral abundance in the whole rock can be made by combining thermogravimetry/evolved water analysis (TG/EWA) and X-ray diffraction (XRD) data. The TGA/EWA system incorporates a purpose built thermobalance linked to a water specific infrared detector which is used to measure quantitatively the clay mineral dehydroxylation water evolved from the whole rock when heated from 250°C to 900°C. This gives a measure of the total hydroxyl content of the clay minerals in the whole rock which, when combined with XRD analysis of a separated clay size-fraction, enables individual clay mineral abundances in the whole-rock sample to be determined. Results on artificial sand/clay mineral mixtures prepared with known amounts of different clay minerals (chlorite, illite and kaolinite) show that the accuracy of the combined method is most influenced by the accuracy of the XRD data. Errors associated with TG/EWA were found to be negligible by comparison. A case study is included in which the technique has been used to determine accurately the illite abundance in the Magnus Sandstone Reservoir, Northern North Sea.

Corrigendum - Transformations of clay minerals in black earth and red loams of basaltic origin.

1954 ◽  
Vol 5 (1) ◽  
pp. 98
Author(s):  
JA Ferguson
Keyword(s):  
Thermal Analysis ◽  
Differential Thermal Analysis ◽  
Clay Minerals ◽  
Clay Mineral ◽  
Soil Types ◽  
X Ray Diffraction ◽  
X Ray ◽  
Partial Decomposition ◽  
Red Soils ◽  
Eastern Australia

The development in the Toowoomba area, Queensland, of red, black, and transitional soil types from basalt is typical of similar processes in many parts of eastern Australia. Systematic samples from this area have been investigated mineralogically by differential thermal analysis, X-ray diffraction, and other methods. Montmorillonite appears to be the clay mineral first formed under present weathering conditions. The further transition to red soils in certain situations is due to partial decomposition of montmorillonite to minerals of the kaolin group by loss of alkalis and iron, the latter being stabilized in the upper horizons as hydrated oxides. Further decomposition of kaolin minerals produces gibbsite. Changes in the nature and amount of clay minerals are thought to correspond with stages in the evolution of basalt soil types.

Transformations of clay minerals in black earth and red loams of basaltic origin.

1954 ◽  
Vol 5 (1) ◽  
pp. 98
Author(s):  
JA Ferguson
Keyword(s):  
Thermal Analysis ◽  
Differential Thermal Analysis ◽  
Clay Minerals ◽  
Clay Mineral ◽  
Soil Types ◽  
X Ray Diffraction ◽  
X Ray ◽  
Partial Decomposition ◽  
Red Soils ◽  
Eastern Australia

The development in the Toowoomba area, Queensland, of red, black, and transitional soil types from basalt is typical of similar processes in many parts of eastern Australia. Systematic samples from this area have been investigated mineralogically by differential thermal analysis, X-ray diffraction, and other methods. Montmorillonite appears to be the clay mineral first formed under present weathering conditions. The further transition to red soils in certain situations is due to partial decomposition of montmorillonite to minerals of the kaolin group by loss of alkalis and iron, the latter being stabilized in the upper horizons as hydrated oxides. Further decomposition of kaolin minerals produces gibbsite. Changes in the nature and amount of clay minerals are thought to correspond with stages in the evolution of basalt soil types.

Qualitative and quantitative mineralogical composition of the Rupelian Boom Clay in Belgium

Clay Minerals ◽  
2015 ◽  
Vol 50 (2) ◽  
pp. 249-272 ◽  
Author(s):  
E. Zeelmaekers ◽  
M. Honty ◽  
A. Derkowski ◽  
J. Środoń ◽  
M. De Craen ◽  
...  
Keyword(s):  
Clay Minerals ◽  
Clay Mineral ◽  
Quantitative Composition ◽  
Bulk Rock ◽  
X Ray Diffraction ◽  
Rock Composition ◽  
X Ray ◽  
Boom Clay ◽  
Bulk Rock Composition ◽  
Clay Formation

AbstractThe Boom Clay Formation of early Oligocene age, which occurs underground in northern Belgium, has been studied intensively for decades as a potential host rock for the disposal of nuclear waste. The goal of the present study is to determine a reference composition for the Boom Clay using both literature methods and methods developed during this work. The study was carried out on 20 samples, representative of the lithological variability of the formation. The bulk-rock composition was obtained by X-ray diffraction using a combined full-pattern summation and singlepeak quantification method. Siliciclastics vary from 27 to 72 wt.%, clay minerals with 25–71 wt.% micas, 0–4 wt.% carbonates, 2–4 wt.% accessory minerals (mainly pyrite and anatase) and 0.5–3.5 wt.% organic matter. This bulk-rock composition was validated independently by majorelement chemical analysis. The detailed composition of the clay-sized fraction was determined by modelling of the oriented X-ray diffraction patterns, using a larger sigma star (σ*) value for discrete smectite than for the other clay minerals. The <2 μm clay mineralogy of the Boom Clay is qualitatively homogeneous; it contains 14–25 wt.% illite, 19–39 wt.% smectite, 19–42 wt.% randomly interstratified illite-smectite with about 65% illite layers, 5–12 wt.% kaolinite, 4–17 wt.% randomly interstratified kaolinite-smectite and 2–7 wt.% chloritic minerals (chlorite, “defective” chlorite and interstratified chlorite-smectite). All modelled clay mineral proportions were verified independently using major-element chemistry and cation exchange capacity measurements. Bulkrock and clay mineral analysis results were combined to obtain the overall detailed quantitative composition of the Boom Clay Formation.

SOME PODZOL SOILS OF ALBERTA

1960 ◽  
Vol 40 (1) ◽  
pp. 1-14 ◽  
Author(s):  
S. Pawluk
Keyword(s):  
Clay Minerals ◽  
Clay Mineral ◽  
Diffraction Data ◽  
Strong Evidence ◽  
Clay Content ◽  
X Ray Diffraction ◽  
X Ray ◽  
Mineral Components ◽  
Mixed Layering ◽  
Podzol Soils

Recent exploratory surveys in the northern sections of Alberta revealed many soils morphologically similar to podzols. A laboratory study was carried out to obtain a better understanding of the genesis and morphology of these soils.Chemical analyses showed the percentage base saturation and pH to be higher than for typical podzols.Physical analyses showed slight increases in clay content in the B horizons and decreases in the A horizons when compared to the parent material.From mineralogical studies of the profiles, the following weathering sequences were established: feldspars>quartz; chlorite>biotite>muscovite; [Formula: see text]. X-ray diffraction data showed illite, montmorillonite-illite mixed layering, montmorillonite, and kaolinite as being the principal clay minerals present in the A and C horizons. The clay mineral components of the B horizons were primarily chlorite-like with lesser amounts of kaolinite. Analyses indicated that the chlorite-like mineral lacked properties attributed to well crystallized chlorites and provided strong evidence in favour of authigenic origin.Data obtained in this study showed the genesis of these soils to be somewhat different from that reported for podzols elsewhere although the process of formation evidently was primarily chemical.

scholarly journals Investigation on Physicomechanical Properties and Constitutive Model of Tuff in Mila Mountain Tunnel under Dry and Saturated Conditions

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Zhihao He ◽  
Xiangjun Pei ◽  
Shenghua Cui ◽  
Wentai Sun ◽  
Luguang Luo ◽  
...  
Keyword(s):  
Constitutive Model ◽  
Clay Minerals ◽  
Physicomechanical Properties ◽  
Uniaxial Compression Test ◽  
High Porosity ◽  
X Ray Diffraction ◽  
Water Softening ◽  
Tunnel Excavation ◽  
Damage Constitutive Model ◽  
Mountain Tunnel

Many tunnel engineering accidents are generally caused by water softening tuff of high porosity. Experimental and theoretical analytical methods, including rock ultrasonic testing, X-ray diffraction (XRD), microscopic observation, uniaxial compression test, and scanning electron microscope (SEM), are employed to analyze the physicomechanical properties of tuff in Mila Mountain tunnel under dry and saturated conditions. Then, the mechanism of tuff softening in water is explained. Finally, the statistical damage constitutive model of tuff is established. It was revealed that the tuff compositions were dominated by quartz and clay minerals accounting for more than 90%, and clay minerals, anhydrite, and pyrite were mainly soluble minerals. After being saturated with water, the soluble minerals in the tuff are dissolved, and the porosity and wave velocity are increased; however, the elastic modulus and peak strength are decreased, indicating that water softening was distinct. Water softening after saturation was due to the mineral compositions and microstructure characteristics of tuff in Mila Mountain tunnel; specifically, as the tuff characterized by high porosity was conductive to water absorption, the soluble minerals in the tuff were corroded and swelled by water, dissolving, loosening, and softening the tuff structure; then, its mechanical behavior was degraded. It was demonstrated by the experimental results consistent with theoretical results that the model can be employed to express the constitutive behavior of tuff in Mila Mountain tunnel under dry and saturation conditions. The findings provide insights into macroscale deterioration of tuffs and theoretical knowledge for the tunnel excavation and support of Mila Mountain tunnel.

Low-grade evolution of clay minerals and organic matter in fault zones of the Hikurangi prism (New Zealand)

Clay Minerals ◽  
2018 ◽  
Vol 53 (4) ◽  
pp. 579-602 ◽  
Author(s):  
Tatiana Maison ◽  
Sébastien Potel ◽  
Pierre Malié ◽  
Rafael Ferreiro Mählmann ◽  
Frank Chanier ◽  
...  
Keyword(s):  
Organic Matter ◽  
New Zealand ◽  
Clay Minerals ◽  
Clay Mineral ◽  
Structural Characteristics ◽  
Mineral Chemistry ◽  
Fault Zones ◽  
Low Grade ◽  
Pore Fluid Chemistry ◽  
Mineral Crystallinity

ABSTRACTClay minerals and organic matter occur frequently in fault zones. Their structural characteristics and their textural evolution are driven by several formation processes: (1) reaction by metasomatism from circulating fluids; (2)in situevolution by diagenesis; and (3) neoformation due to deformation catalysis. Clay-mineral chemistry and precipitated solid organic matter may be used as indicators of fluid circulation in fault zones and to determine the maximum temperatures in these zones. In the present study, clay-mineral and organic-matter analyses of two major fault zones – the Adams-Tinui and Whakataki faults, Wairarapa, North Island, New Zealand – were investigated. The two faults analysed correspond to the soles of large imbricated thrust sheets formed during the onset of subduction beneath the North Island of New Zealand. The mineralogy of both fault zones is composed mainly of quartz, feldspars, calcite, chabazite and clay minerals such as illite-muscovite, kaolinite, chlorite and mixed-layer minerals such as chlorite-smectite and illite-smectite. The diagenesis and very-low-grade metamorphism of the sedimentary rock is determined by gradual changes of clay mineral ‘crystallinity’ (illite, chlorite, kaolinite), the use of a chlorite geothermometer and the reflectance of organic matter. It is concluded here that: (1) the established thermal grade is diagenesis; (2) tectonic strains affect the clay mineral ‘crystallinity’ in the fault zone; (3) there is a strong correlation between temperature determined by chlorite geothermometry and organic-matter reflectance; and (4) the duration and depth of burial as well as the pore-fluid chemistry are important factors affecting clay-mineral formation.

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