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Examination of lower Jurassic mudrocks using backscattered electron microscopy

Conference · · Am. Assoc. Pet. Geol., Bull.; (United States)
OSTI ID:5590277
;
The small size of many of the particles in mudrocks makes it almost impossible to image and identify them individually and in situ, using conventional light microscopy. Since the average mudrock contains about 60% clay minerals, an understanding of these minerals is central to the question of burial diagenesis and hydrocarbon generation. Much of the existing evidence concerning burial diagenesis relies on x-ray diffraction data (XRD), particularly with respect to the clay-sized (< 2 ..mu..m) fraction of mudrocks. Backscattered electron techniques (BSE) in scanning electron microscopy (SEM) together with energy-dispersive x-ray microanalysis (EDX), XRD, and electron microprobe analysis, indicate that Lower Jurassic mudrocks from the North Sea basin contain many clay mineral stacks up to 150 ..mu..m long. By studying polished mudrock sections with BSE and EDX, the sizes, shape, orientation, textural relations and internal compositional variation of the clay minerals can be observed in situ. Preliminary evidence suggests that the clay stacks are authigenic and may have formed at shallow burial depths during early diagenesis. In addition, sand- and silt-sized clay pellets (glauconite) composed chiefly of iron-bearing dioctahedral mica were observed in the sediment. The irregular shapes and textural intergrowths of many pellets suggest that active outward growth occurred, probably by a combination of displacement and replacement in the surrounding matrix material.
Research Organization:
Arizona State Univ., Tempe
OSTI ID:
5590277
Report Number(s):
CONF-8408161-
Conference Information:
Journal Name: Am. Assoc. Pet. Geol., Bull.; (United States) Journal Volume: 68:7
Country of Publication:
United States
Language:
English

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Related Subjects

02 PETROLEUM
020200* -- Petroleum-- Reserves
Geology
&amp; Exploration
CLAYS
DIAGENESIS
ELECTRON MICROSCOPY
ENERGY SOURCES
FLUIDS
FOSSIL FUELS
FUEL GAS
FUELS
GAS FUELS
GASES
GEOLOGIC AGES
JURASSIC PERIOD
LITHOLOGY
MATURATION
MESOZOIC ERA
MICROSCOPY
NATURAL GAS
PETROLEUM
ROCKS
SEDIMENTARY ROCKS
SOURCE ROCKS