Fissility of Mudrocks

Ingram, R.L.

doi:10.1130/0016-7606(1953)64[869:fom]2.0.co;2

Cited by 80 publications

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“…The criss-cross orientation of fire clay mineral crystals is interpreted as arising from the haphazard and random growth of crystal aggregates of clay minerals crystallizing within a quiet, fairly homogeneous body of mud or gel that is essentially physically isotropic. The clay plates in a laminated marine shale, on the other hand, are initiated as a result of the flocculation of clay as it enters saline water, after which flakes grow as it settles through or is washed about in the water containing a high concentration of effective cations (Keller, 1946;Ingrain, 1953).…”

Section: The Semi-plastic and Semi-flint Claysmentioning

confidence: 99%

The Origin of Missouri Fire Clays

Keller

1953

Clays clay miner. (Natl. Conf. Clays Clay Miner.)

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The origin of Missouri fire clays is interpreted from the testimony of the clays in terms of the geologic setting in which they were deposited and developed. Hence, the approach to the interpretation is fundamentally that of sedimentary petrology, rather than economic geology. The clays, as sedimentary rocks, are considered to be the products (mineralogie and geologic) resulting from the responses of their source materials to the energetics of the physical and chemical'environments which were impressed upon them during the time interval of their deposition and diagenesis.The fire clays are inferred to have a sedimentary origin; it is believed that their present-day characteristics were essentially developed in the time intervals of the Cheltenham to pre-Fort Scott (Pennsytvanian) age. The different varieties of fire clay are interpreted as different lithofacies within a continuous Cheltenham deposit. The high-alumina facies (diaspore-burley and boehmite) appears to have been formed by severe leaching on a relatively stable land area, whereas the kaolinitic-illitic facies (semi-plastic to semi-flint clay) seem to characterize products formed near the margin of a slowly sinking depositional region. Both processes of destruction and construction ("katamorphism" and "anamorphism," as used by Van Hise, 1904) appear to have operated in the genesis of the clay minerals.Evidence points toward a negative Eh and an approximately neutral to slightly acid pH during the formation of the clays. The presence of diaspore and boehmite and the absence of gibbsite in the high-alumina clay are interpreted as indications of leaching of clay minerals under waterlogged conditions. Diaspore may inherit part of the crystal structure and energy of the kaolinite from which it was derived. INTRODUCTIONThe facts that one of the major themes of the program at this Conference on Clays and Clay Minerals is the genesis of clay, and that the conference is held at the University of Missouri make a discussion of the origin of Missouri fire clays very timely. The objectives of this paper are : first, to describe the geologic and mineralogic evidence which bears on the origin of Missouri fire clays, and of the associated rocks of essentially the same age (Pennsylvanian) thought they are barren of economically producible, refractory fire clay; second, to draw genetic inferences from the evidence; and, third, to interpret from those inferences the geological, mineralogical, and chemical environments in which the clay was formed. Finally, a geologic model for the formation of the clay will be proposed. For brevity, only a minimum of stratigraphic detail will be presented; the detailed stratigraphy has been thoroughly covered by Mc~ueen (1943).

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Section: The Semi-plastic and Semi-flint Claysmentioning

confidence: 99%

The Origin of Missouri Fire Clays

Keller

1953

Clays clay miner. (Natl. Conf. Clays Clay Miner.)

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“…There is no reason why we should restrict our usage of the word 'shale' to laminated and/or fissile fine-grained sedimentary rocks, because 'lamination' has both a descriptive and a genetic definition with distinct sedimentological implications (cf. McKee & Weir 1953;Campbell 1967), and particularly because fissility is a secondary property largely related to weathering (Ingram 1953). Other authors prefer the term 'mudstone' for fine-grained sedimentary rocks in general (e.g.…”

Section: Origin Of Stratification In Shalesmentioning

confidence: 99%

“…As discussed by Macquaker & Adams (2003), although this may sometimes be the case (cf. Oertel & Curtis 1972), many fissile shales are not laminated and their fissility is a secondary property largely related to weathering (Ingram 1953). Fissility is not a good rock classification criterion, because some mudstones are then merely freshly exposed shales.…”

Section: Origin Of Stratification In Shalesmentioning

confidence: 99%

More gaps than shale: erosion of mud and its effect on preserved geochemical and palaeobiological signals

Trabucho‐Alexandre¹

2014

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“…Many workers (Ingram, 1953;Grim, Bradley, White, 1957;Gipson, 1965;and Odom, 1967) have studied the fabric of shales using petrographic or x-ray diffraction methods.White (1961) and O'Brien (1964) published x-ray diffraction traces of very fissile gray shales which indicated clay platelets are oriented with their C axis perpendicular to the fissility plane. It is concluded by most workers that the degree of fissility of shales is: proportional to the degree of preferred clay flake orientation.…”

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confidence: 99%

“…Many workers (Ingram, 1953;Grim, Bradley, White, 1957;Gipson, 1965;and Odom, 1967) have studied the fabric of shales using petrographic or x-ray diffraction methods.…”

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Clay Fabric of Very Fissile Paleozoic Gray Shales

O’Brien

1968

atgeol

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The purpose of this paper is to report preliminary findings of an electron microscope study of the fabric of Paleozoic gray shales.Very few electron micrographs have been published which show in detail the actual clay flake orientation in very fissile shales, therefore, it is felt that such a study would be useful in determining factors which contribute to shale fabric and fissility.Fissility is that characteristic which causes shale to split into thin layers, usually parallel to the bedding plane. Many workers (Ingram, 1953;Grim, Bradley, White, 1957;Gipson, 1965;and Odom, 1967) have studied the fabric of shales using petrographic or x-ray diffraction methods.White (1961) and O'Brien (1964) published x-ray diffraction traces of very fissile gray shales which indicated clay platelets are oriented with their C axis perpendicular to the fissility plane. It is concluded by most workers that the degree of fissility of shales is: proportional to the degree of preferred clay flake orientation.Therefore, very fissile shales should be composed of clay flakes with the highest degree of preferred orientation.This author conducted a detailed electron microscope study of the surface morphology of a number of gray shales possessing well developed fissility in order to test the validity of this conclusion.Each sample of shale was broken parallel to the fissile plane and the exposed surface cleaned with a fine brush.This surface was replicated first with a coat of platinum -palladium metal and then with carbon. The shadow angle was 90° and the sample was rotated during shadowing. Replicated specimens were placed into hydrofluoric acid, dissolving the clay and allowing the replica to float free. After remaining in the acid bath for two days, the replicas were washed in distilled water and mounted on copper grids. Figure 1 shows the electron micrographs of the number of very fissile gray shales.X-ray data obtained by the author but not included in this paper reveal a high degree of parallelism of the clay flakes in these illitic shales.The electron micrographs corroborate this interpretation. The reader will notice that the clay flakes overlap like pages in a book and that there is a remarkably high degree of preferred orientation.This work supports the conclusion that the major cause of fissility is the parallel orientation of clay particles and is offered as additional evidence to corroborate conclusions previously reached from X-ray data.

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Fissility of Mudrocks

Cited by 80 publications

References 0 publications

The Origin of Missouri Fire Clays

The Origin of Missouri Fire Clays

More gaps than shale: erosion of mud and its effect on preserved geochemical and palaeobiological signals

Clay Fabric of Very Fissile Paleozoic Gray Shales

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