Depositional Environment of Clay Minerals from Northeast Gulf of Alaska: ABSTRACT

AbstractX-ray analyses of selected samples from the argillaceous subdivisions of the English Wealden indicate that illite, kaolinite, and mixed-layer structures are present in variable amounts. The clay mineral assemblage is thought to reflect parent material, weathering conditions in the source area, and possibly some degrading of the illite structure by the action of active waters in the depositional environment. The specific clay minerals are tentatively correlated with the palaeogeographical framework proposed by Allen (1954). It is suggested that the kaolinite was derived mainly from the Palaeozoic uplands, and the bulk of the illite and mixed-layer structures from the marginal Jurassic lowland.

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Uranium mineralization of the Witwatersrand and Dominion Reef systems

Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences ◽

10.1098/rsta.1977.0130 ◽

1977 ◽

Vol 286 (1336) ◽

pp. 527-548 ◽

Cited By ~ 45

Keyword(s):

Clay Minerals ◽

Depositional Environment ◽

Fission Track ◽

Carbonaceous Material ◽

High Energy ◽

Uranium Mineralization ◽

Stable Phase ◽

Uranyl Ions ◽

Indus River ◽

Reducing Atmosphere

Uranium-bearing minerals in the Witwatersrand and Dominion Reef sediments have been studied by ore microscopic, electron microprobe, fission track and neutron activation analytical methods to determine the controls of uranium mineralization. In the Dominion Reef, which represents a high-energy banket type of depositional environment, allogenic thorian uraninite occurs in hydraulic equivalence with allogenic pyrite, quartz and possibly also gold in the sediments which have uraniumthorium ratios between 3.1 and 5.6 indicating substantial amounts of thorium-rich resistate minerals. The Witwatersrand sediments have uranium-thorium ratios ranging between 7.1 and 19.6 indicating lesser amounts of resistates which is consistent with the lower energy depositional environment. The proximal or nearshore deposits are of banket type but are distinguished from the Dominion Reef by the abundance of concretionary pyrite formed within the Basin and the presence of carbonaceous matter. The distal deposits formed at greater distance from the shoreline contain decaying organic material which has precipitated both uranium and gold from solution. Subsequent metamorphism has resulted in the formation of carbonaceous material bearing finely disseminated low-thorium pitchblende and a fine dissemination of gold associated with sulphides and arsenides. Further evidence of the existence of uranium in solution is to be found in the banket deposits. In this case fine disseminations of uranium (> 500 parts/10 6 ) occur in clay minerals within concretionary pyrite nodules and in lenticles formed of clay minerals in Witwatersrand banket deposits. They represent reduction-deposition of the soluble uranyl ion below the sediment-water interface where conditions are reducing. Allogenic thorian uraninite from the present-day Indus river has a texture, composition and association with gold and pyrite similar to allogenic uraninite in the Witwatersrand and Dominion Reef System. Thorian uraninite is a stable phase over large distances in this river. Hence it would appear quite unnecessary to postulate a reducing atmosphere for the transportation of detrital uraninite. Moreover the retention of sulphate and uranyl ions in solution in the model proposed here suggests that the atmosphere was oxidizing at the time of deposition. This conclusion indicates the likely occurrence in younger sediments of mineralization of this type provided the necessary geological criteria are met.

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Relationship of Clay Minerals to Depositional Environment in the Non-Marine Eocene Pontils Group, Se Ebro Basin (Spain)

Journal of Sedimentary Research ◽

10.1306/d426780c-2b26-11d7-8648000102c1865d ◽

1991 ◽

Vol Vol. 61 ◽

Cited By ~ 1

Author(s):

M. Ingles, P. Anadon

Keyword(s):

Clay Minerals ◽

Depositional Environment ◽

Ebro Basin ◽

Relationship Of

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Clay Minerals and Detrital Material in Paleocene–Eocene Biogenic Siliceous Rocks (Sw Western Siberia): Implications for Volcanic and Depositional Environment Record

Geosciences ◽

10.3390/geosciences10050162 ◽

2020 ◽

Vol 10 (5) ◽

pp. 162

Author(s):

Pavel Smirnov ◽

Oksana Deryagina ◽

Nadezhda Afanasieva ◽

Maxim Rudmin ◽

Hans-Jürgen Gursky

Keyword(s):

Clay Minerals ◽

Depositional Environment ◽

Western Siberia ◽

Ultramafic Rocks ◽

Burial Diagenesis ◽

Detrital Material ◽

Siliceous Rocks ◽

Low Degree ◽

Provenance Areas ◽

High Degree

The paper presents the results of a study on clay minerals and detrital material of biosiliceous rocks (Paleocene–Eocene) from three sections in the Transuralian region. The authigenic processes in sediments resulted in the formation of dioctahedral clay minerals (illite, smectite) and insignificant amounts of sulfide phases (pyrite, hydrotroillite). Detrital minerals from the studied diatomites and diatomaceous clays often have a subangular and semi-rounded habit that is evidence of a low degree alteration of the sedimentary material in the provenance areas. The high degree of preservation of the bioclastic debris and the transformation of the limited volcanogenic substratum in clay minerals apparently was possible by initial burial diagenesis. The morphology of kaolinite and illite suggests that these mineral formations were caused by diagenesis with feldspars and smectites as a substrate for their formation. The smectite zone of weathering crust that developed on the adjacent land could have also served as a significant source of smectites entering the sea basin. The association with smectite in aggregates of mixed clayey composition indicates a sequential smectite-to-illite reaction via mixed-layered minerals. Such minerals as amphiboles, pyroxenes, and olivines, semi-stable to transportation and genetically associated with ultramafic rocks, form a significant part of the clastic fraction of the rock, indicating the proximity of provenance areas. This is the evident reason that the provenance areas made of mafic and ultramafic rocks played an essential role.

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Hydrated form of some clay minerals observed using a film sealed environmental cell

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100107502 ◽

1978 ◽

Vol 36 (1) ◽

pp. 72-73

Author(s):

N. Kohyama ◽

K. Fukushima ◽

A. Fukami

Keyword(s):

Clay Minerals ◽

Morphological Changes ◽

Carbon Film ◽

Electron Microscopic Observation ◽

Adsorbed Water ◽

Electron Microscopic ◽

Hydrated Form ◽

Thin Carbon ◽

Environmental Cell ◽

Thin Carbon Film

Since the interlayer or adsorbed water of some clay minerals are quite easily dehydrated in dried air, in vacuum, or at moderate temperatures even in the atmosphere, the hydrated forms have not been observed by a conventional electron microscope(TEM). Recently, specific specimen chambers, “environmental cells(E.C.),” have been developed and confirmed to be effective for electron microscopic observation of wet specimen without dehydration. we observed hydrated forms of some clay minerals and their morphological changes by dehydration using a TEM equipped with an E.C..The E.C., equipped with a single hole copper-microgrid sealed by thin carbon-film, attaches to a TEM(JEM 7A) with an accelerating voltage 100KV and both gas pressure (from 760 Torr to vacuum) and relative humidity can be controlled. The samples collected from various localities in Japan were; tubular halloysite (l0Å) from Gumma Prefecture, sperical halloysite (l0Å) from Tochigi Pref., and intermediate halloysite containing both tubular and spherical types from Fukushima Pref..

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Colloidal systems in soils

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100168050 ◽

1994 ◽

Vol 52 ◽

pp. 64-65

Author(s):

J. Thieme ◽

J. Niemeyer ◽

P. Guttman

Keyword(s):

Clay Minerals ◽

Polymeric Materials ◽

Spatial Arrangement ◽

High Specific Surface Area ◽

Turnover Rates ◽

Colloidal Systems ◽

Chemical Conditions ◽

Aggregation Phenomena ◽

Iron And Manganese ◽

Soil Colloids

In soil science the fraction of colloids in soils is understood as particles with diameters smaller than 2μm. Clay minerals, aquoxides of iron and manganese, humic substances, and other polymeric materials are found in this fraction. The spatial arrangement (microstructure) is controlled by the substantial structure of the colloids, by the chemical composition of the soil solution, and by thesoil biota. This microstructure determines among other things the diffusive mass flow within the soils and as a result the availability of substances for chemical and microbiological reactions. The turnover of nutrients, the adsorption of toxicants and the weathering of soil clay minerals are examples of these surface mediated reactions. Due to their high specific surface area, the soil colloids are the most reactive species in this respect. Under the chemical conditions in soils, these minerals are associated in larger aggregates. The accessibility of reactive sites for these reactions on the surface of the colloids is reduced by this aggregation. To determine the turnover rates of chemicals within these aggregates it is highly desirable to visualize directly these aggregation phenomena.

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