ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1977.tb01110.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SUMMARYAutomated reflectance microscopy (ARM) systems employ a microscope photometer in conjunction with a computer which controls a motor‐driven stage drive and records and categorizes the photomultiplier output. In a system being developed at The Pennsylvania State University, the object stage moves continuously under the microscope objective at a constant speed and in a predetermined raster. With a scan speed of 1600 μm/s and the computer recording the photo‐multiplier output every 1.25 ms, each recording represents a scan of 2 μm. An aperture below the photomultiplier is set to give an effective area of measurement of 2 μm square, so that a continuous series of readings is obtained on adjacent fields of this size. The difference in reflectance between coal and pyrite particles in polished coal pellets enables pyrite chord‐size distributions to be measured; consecutive recordings on pyrite grains are summed to give a measure of chord length. Size distributions determined by ARM compare well with values measured by visual microscopy. In the course of analysis of a single coal pellet, approximately 400,000 individual readings are recorded, the entire operation of scanning and printout of data taking approximately 18 min. Coal reflectograms obtained by ARM may be used for rank measurements and to indicate petrographic comp

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1977.tb01111.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SUMMARYPetrographic analysis is used to characterize coals in terms of the maceral group composition and the reflectance of the vitrinite. Interchangeability of results and applicability of prediction methods have been hampered up to now through differences between the methods used by different petrographers. Some aspects of a proposed standard method being developed in this country are described.

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1977.tb01112.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SUMMARYTheoretical and empirical formulae are given which relate the principal reflectivities of uniaxial and biaxial substances to the mean values of random, maximum and minimum reflectivities measured on particulate samples. Instead of using values of R̄aand R̄a− R̄cdetermined along the principal directions, a method is described for determining respectively: (a) coal rank through the mean random vitrinite reflectivity, and (b) the bireflectance using the difference between the mean random maximum and minimum reflectivities measured on particulate samples, irrespective of uniaxial or biaxial chara

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1977.tb01113.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SUMMARYErrors in the refractive and absorptive indices derived from reflectance measurements on relatively low‐absorbing organic substances in two media are discussed, with particular reference to coal macerals and cokes. Variation of errors in refractive and absorptive indices at different levels of reflectance, and the effect of different combinations of sign and magnitude of reflectance error on the two parameters, are presented in both tabulated form and as diagrams. The errors in the refractive and absorptive indices vary in relation to reflectance level, the reflectance difference between standard and unknown, the difference between the refractive indices of the unknown and the immersion oil and the wavelength of reflectance measurement within the visible spectrum. Despite the variation, it is possible to obtain useful values for the parameters within the low‐absorbing range. If the absorption is negligible, it may not be possible to obtain realistic values for absorptive index, but even where this is the case, satisfactory values for refractive index can still be obtained. Suggestions are made on how to minimize reflectance errors and to increase the accuracy of dispersion curves for derived refractive and absorptive indices within the visible spect

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1977.tb01114.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SUMMARYSamples may be obtained from outcrops, cuttings, cores, modern sediments and old collections. Coals, brown or grey siltstones and fine‐grained sandstones generally yield the most satisfactory organic matter for maturation analysis, while red beds and evaporites are often barren. Shales with a high organic content are not especially desirable for optical studies of maturation because the organic matter is likely to be very fine‐grained and high in pyrite. The whole rock or a concentrate of organic particles may be prepared for microscopical study, the former being preferred for analysis of solid bitumens and fluorescence study, the latter for measurement of vitrinite reflectance, microspore translucency and refractive index. Crushing, ultrasonic disintegration, handpicking, heavy liquid separation, flotation, settling, sieving and demineralization with HC1 and HF are used to concentrate organic particles. Preparations include polished rock slabs, concentrate briquettes and strew mounts.The constituents with the lowest maturation in a rock must be selected if maturation indigenous to the rock is to be measured. Organic matter that has been previously altered at its site of origin, reworked and altered during diagenesis, or redeposited from older rocks, must be excluded from consideration. The organic constituents are recognized most easily by reflected light microscopy. A combination of fluorescence and reflectance techniques is useful for low rank samp

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1977.tb01115.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SUMMARYFluorescence microscopy of polished surfaces allows more satisfactory study and identification of the hydrogen‐rich constituents (liptinites) that are the precursors of petroleum and which, in soft brown coals, fine‐grained clastic and carbonate sediments can hardly be detected using normal reflected light. Diagnostic properties of liptinites and lipoid substances are their colour, intensity and variation of fluorescence (both colour and intensity) during irradiation which may allow distinction of organic and inorganic constituents in coals and bituminous shales. Fluorescence properties also change with increasing degree of diagenesis (‘rank’) of organic matter, although organic constituents cease to fluoresce beyond the medium‐volatile, bituminous‐rank stage. In this paper fluorescence microscopy as a means of studying the rank of coaly and lipoid substances in sedimentary rocks is discussed after a brief description of the method. The influence of facies on fluorescence properties is considered and the relative merits of fluorescence and reflectance measurements in different parts of the rank range are discussed. The importance of fluorescence microscopy in petroleum exploration is also emphasized. Finally, consideration is given to the future of fluorescence microscopy in relation to the ‘bituminization range’ of coalification which has important implications to both petroleum generation and to the coking and hydroge

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1977.tb01116.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SUMMARYA silicified Palaeocene peat layer discovered in a lignite bed in western North Dakota, U.S.A., has proved to be excellent material for studying the transformation from peat to lignite. Detailed anatomical structures are well preserved in the peat and similar to the level of preservation of Carboniferous coal balls. A compaction of 4: 1 results when the peat is converted to lignite. Loss in volume is primarily caused by the loss of cellular cavities and intergranular spaces and consequent loss or redistribution of moisture. Huminite formed from secondary xylem and phloem sclereids differs in appearance under the microscope from huminite derived from periderms and young cortical tissues. Resinites are formed from fillings of resin canals, secretory cells and sclereids of secondary phloem and may also originate from resinous materials occurring in the palisade and spongy mesophyll of leaves. Cutinite can form from either cuticles or from compressed cortical tissues of young roots. Charred leaves and charred secondary xylem and phloem comprise an important portion of the fusinitic and semifusinitic fractions of the coal. Pyrite grains tend to occupy the cell cavities of early wood and ray cells. Differences between collinite and telinite developed during the peat stage, while progressive coalification tends to accentuate the lack of structure in the collinite.

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1977.tb01117.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SUMMARYThe optical properties of vitrinite and exinite from a low‐rank coal (volatile matter = 37.3% dry ash free) oxidized with air on a fluidized bed at 300°C over periods up to 24 h have been studied. Reflectivities in air and oil of the unoxidized maceral areas within the particles and of the oxidized rims were measured at five wavelengths between 436 and 644 nm and the absorptive and refractive indices calculated using Beer's equation. The reflectivity spectra and the variation of the optical properties of the oxidized macerals with time of oxidation are discussed. It is concluded that the spectrum of oxidized exinite is a good parameter to indicate oxidation and that in low‐temperature oxidation experiments, when no oxidation rims appear, the inner part of the particles may not be oxid

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1977.tb01118.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY

摘要:

SUMMARYThis investigation indicated that different types of microhardness impressions were obtained on different ranks of coal by the Vickers microhardness test and that oxidation transformed the plastic state of fresh vitrinite into an elastic state. The transformation occurred rapidly in high volatile coals, but more severe oxidation was required to cause this change in low volatile coals. Reflectance also increased with oxidation. As oxygen penetrated a coal particle, it produced changes in the microhardness impressions and in the reflectance which were rather abrupt at some point between the outer surface and the centre. The microhardness impressions combined with the reflectance data were capable of defining the boundary where rapid transition from the plastic to elastic state occurred. Movement of this boundary made it possible to follow the oxygen penetration into coal particles.

ISSN:0022-2720    

DOI:10.1111/j.1365-2818.1977.tb01119.x

出版商:Blackwell Publishing Ltd    

年代:1977

数据来源: WILEY