SEM and TEM evidence of mixed-layer illite-smectite formed by dissolutioncrystallization processes in continental Paleogene sequences in northwestern Argentina

Campo, Margarita Diana Do; Bauluz, Blanca; Nieto, Fernando; Papa, Cecilia Eugenia del; Hongn, Fernando

doi:10.1180/claymin.2016.051.5.03

Cited by 7 publications

(5 citation statements)

References 44 publications

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“…Both backscattered electron images of the clay fraction of sample 04MRE123 show aggregates of small particles with different morphologies: Figure 6a indicates plate type aggregates formed by extremely small particles, whereas flakes aggregates indicate and validate the X-ray diffraction interpretation of the I/S occurrence. Smaller intergrowths with the same structure were already documented by Do Campo et al [18] in backscattered images from ultra-polished thin sections, where they were assigned to interlayered structures. Figure 6b shows a more detailed morphology and size of the particles (2 µ) from the extracted sample fraction.…”

Section: Scanned Electron Microscopysupporting

confidence: 70%

Detection of Interlayered Illite/Smectite Clay Minerals with XRD, SEM Analyses and Reflectance Spectroscopy

Ruitenbeek

Werff

Meijde

2022

Sensors

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Accurate determination of clay minerals can be challenging due to the natural occurrence of interlayered phases, i.e., layers of different clay species such as illite and smectite. The overlap of peaks of the constituent minerals (e.g., illite and smectite), and the similarity of diffraction patterns when not treated with ethylene glycol, hampers identification, especially when the clay content is low. We investigated the occurrence of interlayered illite/smectite in a rock sample from Rodalquilar, Spain, using X-ray diffraction, scanning electron microscopy and reflectance spectroscopy in the short-wave infrared wavelength range. For the first time, a precise determination of interlayered I/S conducted on the extracted clay fraction treated with ethylene glycol using such different approaches was provided. X-ray diffraction results demonstrated the presence of an I/S peak at around 8.4° in the untreated fraction coupled with a peak splitting at 6.7° and 9.4° 2θ when solvated with ethylene glycol. While spectroscopy indicated the occurrence of interlayered structures as a mixture of the two constituent minerals, the results of X-ray analysis showed that the interlayered clay consisted of two discrete phases (illite and smectite). The two discrete phases were observed in both the whole rock analysis and in the extracted clay fraction. This study shows that X-ray diffraction and validation with a scanning electron microscope is a mandatory, integrating tool for detecting interlayered phases since reflectance spectroscopy alone cannot be used to differentiate between interlayered clay minerals and non-interlayered mixtures. This work highlights the limits and advantages of three sensors (X-ray diffraction, scanning electron microscopy and reflectance spectroscopy) to investigate clay mixtures and interlayering, representing a significant contribution to confidence in the interpretation of interlayered clays, this being essential in mineral exploration and prospecting.

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Section: Scanned Electron Microscopysupporting

confidence: 70%

Detection of Interlayered Illite/Smectite Clay Minerals with XRD, SEM Analyses and Reflectance Spectroscopy

Ruitenbeek

Werff

Meijde

2022

Sensors

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“…The latter mineral could represent either an intermediate phase of the replacement process, or a co-product derived from feldspar alteration. As it appears that the chlorite occurring in low-temperature systems derives from specific clay precursors through solid-state transformation mechanisms [38], whereas both direct precipitation and dissolution-crystallization processes are typical of hydrothermal systems [40], the textures described in the analyzed samples strongly suggest that Kihabe baileychlore is associated with the same hydrothermal processes that were responsible for the mineralization. To our knowledge, a specific geothermometer for baileychlore does not exist.…”

Section: Discussionmentioning

confidence: 93%

Mineralogy and Genesis of the Kihabe Zn-Pb-V Prospect, Aha Hills, Northwest Botswana

et al. 2020

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The Kihabe Zn-Pb-V > (Cu-Ag-Ge) prospect is located at the boundary between Namibia and Botswana (Aha Hills, Ngamiland District) in a strongly deformed Proterozoic fold belt, corresponding to the NE extension of the Namibian Damara Orogen. The Kihabe prospect contains Zn-Pb resources of 14.4 million tonnes at 2.84% zinc equivalent, Ag resources of 3.3 million ounces, and notable V-Ge amounts, still not evaluated at a resource level. The ores are represented by a mixed sulfide–nonsulfide mineralization. Sulfide minerals consist mainly of sphalerite, galena and pyrite in a metamorphic quartzwacke. Among the nonsulfide assemblage, two styles of mineralization occur in the investigated samples: A first one, characterized by hydrothermal willemite and baileychlore, and a second one consisting of supergene smithsonite, cerussite, hemimorphite, Pb-phosphates, arsenates and vanadates. Willemite is present in two generations, which postdate sulfide emplacement and may also form at their expenses. These characteristics are similar to those observed in the willemite occurrences of the nearby Otavi Mountainland, which formed through hydrothermal processes, during the final stages of the Damara Orogeny. The formation of the Kihabe willemite is likely coeval. Baileychlore is characterized by textures indicating direct precipitation from solutions and dissolution–crystallization mechanisms. Both processes are typical of hydrothermal systems, thus suggesting a hydrothermal genesis for the Kihabe Zn-chlorite as well. Baileychlore could represent an alteration halo possibly associated either with the sulfide or with willemite mineralization. The other nonsulfide minerals, smithsonite, cerussite, various Pb-phosphates and vanadates, are clearly genetically associated with late phases of supergene alteration, which overprinted both the sulfide and the willemite- and baileychlore-bearing mineralizations. Supergene alteration probably occurred in this part of Botswana from the Late Cretaceous to the Miocene.

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“…5b) and exhibit the typical morphology of illite-smectite layered intergrowths (Fig. 5c) at higher magnification 42 . HRTEM images ( Fig.…”

Section: Smectite (Crystallized Hydrous Aluminosilicate Melt)mentioning

confidence: 84%

Mysterious long-living ultrahigh-pressure or secondary impact crisis

Шумилова

Zubov

Исаенко

et al. 2020

Sci Rep

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High-pressure glass has attracted interest in terms of both its fundamental state under extreme conditions and its possible applications as an advanced material. in this context, natural impact glasses are of considerable interest because they are formed under ultrahigh-pressure and high-temperature (UHpHt) conditions in larger volumes than laboratory fabrication can produce. Studying the UHpHt glasses of the unique giant Kara astrobleme (Russia), we found that the specific geological position of the UHpHt melt glass veins points to an origin from a secondary ultrahigh-pressure (UHp) melt according to the characteristics of the host suevites, which suggest later bottom flow. Here, we propose a fundamentally novel model involving an upward-injected UHp melt complex with complicated multilevel and multi-process differentiation based on observations of the UHP silica glass, single-crystal coesite and related UHp smectite that crystallized from an impact-generated hydrous melt. this model proposes a secondary UHP crisis during the modification stage of the Kara crater formation. The results are very important for addressing fundamental problems in fields as diverse as condensed matter states under extreme pressure and temperature (pt) conditions, material and geological reconstructions of impact structures, water conditions in mineral substances under UHp conditions in the deep earth, and the duration and magnitude of the catastrophic effects of large asteroid impacts. The structure and properties of disordered substances have been studied for a long time and used in a wide range of applications. The behaviour of such substances under extreme conditions, including intense compression, is particularly interesting and is actively studied both theoretically and experimentally 1-7. High-pressure glasses have drawn interest both fundamentally as a material formed under extreme conditions and as a novel compound that could be used in new applications 8,9. The behaviour of disordered and weakly ordered systems under compression has been studied in microvolumes via diamond anvil. Typically, the compression process is performed at pressures of up to 100 GPa and sometimes higher. Furthermore, the experiments are typically performed at room temperature 1,4-6,9. Only a few experiments combining both high pressures and high temperatures have been carried out. However, such studies are intriguing because the simultaneous effects of temperature and pressure can produce profound internal changes in a substance. For example, SiO 2 glass has a significantly higher density and strength at a pressure of approximately 8 GPa and a temperature of 1100 °C than under cold compression 10. The most important properties expected from these glasses are the heat capacity, hardness, unusual optical properties and other physical properties, which can be used in high-tech materials and technologies, including high-energy lasers, microelectronics and innovative optics. Glasses with microstructural features at a nanoscale are potential basic matrices ...

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SEM and TEM evidence of mixed-layer illite-smectite formed by dissolutioncrystallization processes in continental Paleogene sequences in northwestern Argentina

Cited by 7 publications

References 44 publications

Detection of Interlayered Illite/Smectite Clay Minerals with XRD, SEM Analyses and Reflectance Spectroscopy

Detection of Interlayered Illite/Smectite Clay Minerals with XRD, SEM Analyses and Reflectance Spectroscopy

Mineralogy and Genesis of the Kihabe Zn-Pb-V Prospect, Aha Hills, Northwest Botswana

Mysterious long-living ultrahigh-pressure or secondary impact crisis

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