Petrographic work

In addition, relatively little petrographic work, such as that done by Cohen, Spackman and Dolsen (3) on Florida peats, has been attempted on Mississippi River Delta Plain sediments. This paper describes results of a reconnaissance study undertaken to examine, both chemically and petrographically, the occurrence of sulfur in Mississippi Delta Plain sediments. 

A second set of vibracores, as well as associated open water samples were collected for more detailed work. Lithologic units were determined employing the criteria used for the first set and channel samples taken for chemical work. In addition, 1 x 2 cm rectangles for petrographic work were cut from the center of each lithostratigraphic unit less than about 25 cm in length. Two samples were taken in thicker units, one at the top and one at the bottom of the unit. Cores were stored in sealed tubes in a walk-in cooler operated at 5° C. 

Petrographic Work. Petrographic studies required preparation of thin sections. Briefly, rectangular blocks of material were treated with ethanol to remove water and then infiltered with hard grade LR White resin, a low viscosity resin developed for biological work. Following this, the block was mounted on a petrographic slide and a polished thin section produced (see Bailey and Blackson (26) and Blackson and Bailey (27)). A total of 57 sections were produced in this way, at least 1 from each thinner lithofacies unit and 2 from thicker lithofacies units. 

Petrographic work is difficult to correlate with bulk chemical analyses due to the sporadic distribution of pyrite. However, petrographic observations offer clues revealing processes involved in iron sulfide formation. 

The Mn- Cr system can be studied by TIMS, ICPMS, and SIMS techniques. For TIMS and ICPMS work, bulk samples or mineral separates are dissolved and the solutions are passed through ion-exchange columns to produce clean solutions of manganese and chromium. For minerals with high Mn/Cr ratios SIMS can obtain isotopic data while retaining the petrographic context of the measurements. The chromium isotopic compositions may have to be corrected for small additions of chromium from spallation reactions induced by cosmic rays. This is particularly important in iron-rich meteorites. 

In addition to contributing towards the basic petrographic knowledge of the coal seams, this detailed work, employing various techniques, was undertaken on these two seams to explore the possibilities for greater industrial exploitation. The primary use of this coal presently is for steam generation, mainly in railway locomotives. 

Peter H. Given Whereas Tschamler and Fuks, and Peover studied more or less pure vitrinites, Mazumdar apparently worked with whole coals. Moreover, Indian coals, being from Gondwanaland strata, are most probably of very different petrographic composition compared with European and North American coals (rich in exinites and inert macerals See p. 284). Quite apart from the question whether sulfur dehydrogenation really is free of side reactions, there may well be a spread of data at any level or rank because of petrographic differences. 

Martin B. Neuworth In some prior work, which will be published, we analyzed the six coals for petrographic composition and found they contained from 73 to 87% vitrain. In the case of coal No. 1, we compared the petrographic composition of the residue with the original lignite. On the basis of these analyses we would conclude that the vitrinite, resinite, and exinite fractions will undergo depolymerization with the rupture of certain aliphatic linkages. The semifusinite, micrinite, and fusinite appear to be inert. 

Work is being conducted presently at BCR to relate petrographic characteristics to coal combustion performance. Preliminary results of the study, although incomplete, show a reasonable correlation between certain petrographic properties and coal combustion behavior. 

At present, a petrographic combustion correlation is being worked out which should provide ultimately a general classification of coals for use in several combustion processes. The results of this study will be reported at a later date. 

Dr. Walker We have not related our studies of kinetics of volatile matter release from anthracites to their petrographic consituents. This type of work is planned for the future. 

This work was performed under the auspices of the Office of Basic Energy Sciences, Division of Chemical Sciences, U.S. DOE under contract W-31-109-ENG-38. The authors thank K.L. Stock for the maceral separations, G.R. Dyrkacz for the petrographic analysis and helpful discussion, and VI. Spackman, Penn. State University for choosing and providing the coal samples. 

Alginites were obtained from selected Permo-Carboniferous torbanites (i.e. algal-rich coals) which, upon petrographic analysis, were found to be rich in the required component. No concentration steps were required for samples used in this work as small blocks were selected in which the initial alginite concentrations were adequate (see Table I). 

Transient heating events were important in the formation of the Solar System and provided the energy to produce chondrules and refractory inclusions. These objects are not predicted in astrophysical models for the formation of planetary systems. They comprise 50-80% of the mass of many primitive meteorites. However, the mechanism that produced the transient heating events is still unknown. Future work must focus on putting the details of the petrographic and chemical analysis of these rocks into an astrophysical and cosmochemical framework of Solar System formation. 

We are grateful to R. N. Caron for laboratory work to S. T. Free, M. W. Zacharias, and J. M. Lopez for modeling calculations and to Inland Steel Research Laboratories for petrographic analyses. We are also grateful for financial support provided by the National Science Foundation, Research Applied to National Needs (RANN), under Contract AER 75-13673 by the United States Department of Energy, University Affairs Section of the Division of Materials and Exploratory Research, under Contract No. EX-76-A-01-2295, T.O. No. 26 by the Mobil Research Foundation, Inc. and by the National Science Foundation, through an Energy Traineeship to E.M.S. 

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