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Journal ArticleDOI

Genetic Interpretation of the Polymorphism of the Kaolinite Group in Sedimentary Rocks

01 Oct 1970-Sedimentology (Blackwell Publishing Ltd)-Vol. 15, pp 69-82
TL;DR: In this article, the dynamics of the structural change of triclinic kaolinite and its polymorphous modifications at different stages of sedimentary rock formation are presented. But, the authors do not consider the effects of metagenesis filling of fissures with dickite.
Abstract: SUMMARY The paper presents the dynamics of the structural change of kaolinite and its polymorphous (polytype) modifications at different stages of sedimentary rock formation. Sedimentogenesis is characterized by a gradual disordering of structure of triclinic kaolinite, the degree of disorder produced being proportional to the intensity and duration of the influence of the hydrodynamic medium. Epigenesis (deep) is connected with gradual transformation of kaolinite into dickite through the stage of mixed-layer growths inheriting the structure of twin rotations of disordered kaolinite from the sedimentogenesis stage. In metagenesis filling of fissures with dickite or nacrite takes place. The former is peculiar to the general thermodynamic medium of deep epigenesis/metagen-esis, whereas nacrite is an indicator of intense stress and seems to be due to transformation of dickite.
Citations
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Journal ArticleDOI
TL;DR: The diagenetic evolution of kaolin and illitic minerals in sandstones is described in this article, where the structural characterization of these minerals, the possible reaction pathways leading to their crystallization, and the origin of the fluids involved are discussed specifically.
Abstract: The diagenetic evolution of kaolin and illitic minerals in sandstones is described here. The structural characterization of these minerals, the possible reaction pathways leading to their crystallization, and the origin of the fluids involved are discussed specifically. While early precipitation of kaolinite is in general related to flushing by meteoric waters, subsequent diagenetic kaolinite-to-dickite transformation probably results from invasion by acidic fluids of organic origin. Dickite is the stable polytype in most sandstone formations and the kaolinite-to-dickite conversion is kinetically controlled. The conventional model of kaolin illitization, assuming a thermodynamic control in a closed system, is discussed and compared to an alternative model in which illitization of kaolin is not coupled to dissolution of K-feldspar (Berger et al. , 1997). In the latter model, illite crystallization at the expense of kaolin implies that an energy barrier is overcome either by an increased K+/H+ activity ratio in solution or by a considerable temperature increase.

292 citations

Journal ArticleDOI
Stephen N. Ehrenberg1, P. Aagaard, M. J. Wilson, Anthony R. Fraser, D. Duthie 
TL;DR: In this article, the authors show that the transformation of kaolinite to dickite occurs by dissolution and reprecipitation, rather then in the solid state. But the results are consistent with the transformation depth determined in two other areas studied.
Abstract: Replacement of kaolinite by dickite has been observed to occur with increasing depth of burial in sandstones from three different basins on the Norwegian continental shelf. In the Garn Formation (Middle Jurassic) of Haltenbanken, samples from 1.4-2-7 km below the sea floor (110°C) contain kaolinite, whereas deeper than 3.2 km (130°C) mainly dickite is present. In the Statfjord Formation (Late Triassic-Early Jurassic) from Gullfaks and Gullfaks Sor Fields, transformation of kaolinite to dickite occurs at ~3.1 km below the sea floor (120°C) From the Sto and Nordmela Formations (Lower to Middle Jurassic) to the Troms Area, kaolin polytypes have been identified in only two shallow and two deep samples, but the results are consistent with the transformation depth determined in two other areas studied. These occurrences are significant because they allow the temperature of the kaolinite/dickite transformation to be established with greater confidence than had been possible previously. Also the observation of this transformation in all three areas so far examined indicates that it may be a general and predictable feature of kaolinbearing sandstones worldwide and therefore a potentially reliable paleogeothermometer. In most cases, the kaolinite occurs as relatively large vermicular crystals, whereas dickite forms more euhedral, blockier crystals. This morphological difference, together with the nature of the structural difference in octahedral occupancy between the kaolinite and dickite, suggests that the transformation occurs by dissolution and reprecipitation, rather then in the solid state.

237 citations

Book ChapterDOI
TL;DR: In this paper, the authors discuss mineralogy and petrology of burial diagenesis and incipent metamorphism in clastic rocks and propose an integrated picture of the phase changes in different types of sedimentary rocks upon burial.
Abstract: Publisher Summary This chapter discusses mineralogy and petrology of burial diagenesis and incipent metamorphism in clastic rocks The phase-modification processes referred to as “late-diagenetic” or “epigenetic” (or catagenetic) are metamorphic in nature Hence, the distinction between burial diagenesis and lowest-grade regional metamorphism is largely artificial and arbitrary The modification of various kinds of sedimentary rocks upon burial has largely been studied by investigators from different sub-disciplines within the earth sciences: (1) changes in mineralogy of clay-rich sedimentary rocks by sedimentary petrographers and clay mineralogists; (2) authigenic mineral assemblages in tuffs and volcanic sediments by metamorphic petrologists; and (3) changes in the constitution of coaly and other organic matter by coal petrologists, and organic geochemists The growing awareness of the overlap in space of the physical conditions and of the chemical influences controlling these phenomena warrants renewed efforts to correlate the changes in various types of sedimentary rocks in order to arrive, ultimately, at an integrated picture of the phase changes in different types of sedimentary rocks upon burial and incipient metamorphism This chapter intends to contribute to such an integrated picture

167 citations

Journal ArticleDOI
TL;DR: In this paper, the authors examined the different steps of the depth-related kaolinite-dickite reaction and found that Dickite progressively replaced Kaolinite within a range of burial depths estimated between about 2500 m and 5000 m.
Abstract: The SEM, XRD, FTIR and DTA analyses of different size-fractions of clay material from sandstone reservoirs which have experienced a large range of burial conditions have been used to examine the different steps of the depth-related kaolinite-dickite reaction. Dickite progressively replaced kaolinite within a range of burial depths estimated between about 2500 m and 5000 m. The kaolinite-to-dickite reaction proceeds by gradual structural changes concomitant to crystal coarsening and change from booklet to blocky morphology. The crystallization of dickite proceeds by two distinct paths: (1) Accretion of new material from either dissolution of smaller unstable kaolinite crystals and/or detrital minerals (chiefly feldspars), on early-formed coarser metastable kaolinite crystals which exert extended morphological control on the growing crystals. (2) Neoformation of ordered dickite which will continue to grow by a dissolution-crystallization process. The kaolinite-to- dickite reaction is kinetically controlled and anomalies in the kaolinite/dickite ratio observed in certain sandstone reservoirs may be used to assess the timing of invasion by hydrocarbons.

165 citations

Journal ArticleDOI
TL;DR: In this article, the authors used near-atomic resolution TEM imaging to determine the stacking defect structures in kaolin minerals, especially kaolinite, and showed that few stacking defects exist in this polytype.
Abstract: Near-atomic resolution TEM imaging has been successfully applied to determine the stacking defect structures in kaolin minerals, especially kaolinite. The specimen studied is from the middle stage of the depth-related kaolinite-to-dickite transformation in a sandstone reservoir. Several high-quality images were recorded on films in which the tetrahedral and octahedral positions in the kaolinite unit layers are clearly resolved, despite the obstacle of electron radiation damage. Electron diffraction and high-resolution imaging of dickite showed that few stacking defects exist in this polytype. On the other hand, kaolinite crystals contain a high density of stacking defects. These defects or stacking disorders are formed by a mixture of two kinds of lateral interlayer shifts, t 1 (approximately − a /3) and t 2 (− a /3 + b /3), between adjacent layers. Disorder due to the coexistence of B and C layers (dickite-like stacking sequence) was never observed. These results provide not only an unambiguous settlement for the long -standing controversy of the defect structures in kaolinite, but also a new clue to understanding the kaolinite-to-dickite transformation mechanism.

56 citations


Cites background from "Genetic Interpretation of the Polym..."

  • ...The kaolinite-to-dickite transformation in particular is widely observed during burial diagenesis and its transformation mechanism is an unanswered subject (e.g., Shutov et al. 1970; Ehrenberg et al. 1993; Ruiz Cruz et al. 1993; Beaufort et al. 1998)....

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References
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Journal ArticleDOI
TL;DR: In this article, a model consistent with the infra-red absorption spectra is proposed to position the hydrogen atoms in dickite, and the stacking sequences of kaolin-layer minerals have been considered with reference to the structural features observed in Dickite.
Abstract: The erystal structure of the clay mineral dickite (AI~Si2H409) has been refined to a greater accuracy than that reported in an earlier analysis. Improved lattice parameters are: a 5.1504-0-001, b 8-940 40.001, c 14-424 40-002/~., fl 96 ~ 44' 41'. The diekite structure shows several significant distortions from the geometry of the idealized kaolin layer, including deformation and rotation of the silica tetrahedra. The most striking features of the oetahedral layer are the extremely short shared edges of 2.37 /~. Although the analysis was not sufficiently aecura\"~e to position the hydrogen atoms With certainty, a model consistent with the infra-red absorption spectra is proposed. The stacking sequences of kaolin-layer minerals have been considered with reference to the structural features observed in dickite. There are thirty-six ways of superposing two kaolin layers commensurate with the OH-O bonds found in kaolinite, dickite, and nacrite. The twelve sequences showing the least amount of cation-cation superposition between consecutive kaolin layers can be used to construct two one-layer cells, kaolinite and its mirror image, and twelve two-layer cells, including dickite and nacrite. The distortions of the kaolin layer introduce secondary variations in the interlayer bonding that suggest that diekite and nacrite are the most stable of the kaolin layer structures, since they possess the shortest oxygen-hydroxyl contacts.

118 citations

Journal ArticleDOI
TL;DR: In this paper, the structure of dickite has been evaluated from rotation and Weissenberg data, and the unit cell is monoclinic, Cc, a ~5.15, b = 8.95, c = 14.42/~, fl --96 ° 48', and Z ---4.
Abstract: The structure of dickite has been evaluated from rotation and Weissenberg data. The unit cell is monoclinic, Cc, a ~5.15, b = 8.95, c = 14.42/~, fl --96 ° 48', and Z ---4. One-dimensional Fourier synthesis confirms the polar arrangement of the two kaolin layers in the unit cell. Their disposition within the cell has been established by systematic consideration of possible stacking sequences. The refined structure, obtained by two-dimensional Fourier syntheses, shows considerable distortion within the silica and alumina sheets of the structure.

50 citations