Coalification plant material

Coal contains detrital minerals that were deposited along with the plant material, and authigenic minerals that were formed during coalification. The abundance of mineral matter in coal varies considerably with its source, and is reported to range between 9.05 and 32.26 wt% (Valkovic 1983). Minerals found in coal include (Table 2) aluminosilicates, mainly clay minerals carbonates, such as, calcite, ankerite, siderite, and dolomite sulphides, mainly pyrite (FeS2) chlorides and silicates, principally quartz. Trace elements in coal are commonly associated with one or more of these minerals (see Table 2). 

Coal is mainly composed of carbon, hydrogen and oxygen and is formed from plants by a coalification process. During this process the oxygen, constituting about 40% of the plant material, is split off as, for example, H20 and C02. The process can be... 

Coal lithotypes are megascopically recognizable components of coal. Several nomenclatures have been used to identify the lithotypes [see Damberger et al. (54) for a review of several common classifications]. Coal lithotypes have fairly distinct maceral compositions, which originate from different combinations of plant materials and evolve along somewhat different paths during coalification. 

Coal is an inhomogeneous rock, because different types of plant material behave differently under coalification conditions, and mineral matter is not uniformly distributed, either by type or by amount. Microscopic examination reveals this inhomogeneity by showing that different areas of the coal structure have a different appearance. The organic components of coal are classified into six macerals vitrinite, exinite, resinite, semifusinite, micri-nite, and fusinite. The first three of these macerals are reactive (relatively easily hydrogenated or oxidized), and the other three are relatively inert. Most coals are banded,... 

As coalification progresses, cross-linking increases and the lignin-derived polymers become more aromatic. Phenolic polycarboxylic acids and hydroxynaphthalene dicarboxylic acids which were identified are not found in the CuO-NaOH oxidation products of lignins and plant materials. 

Peat is formed from degradative remains of plant material, mainly of the peat mosses Sphagnum and Hypnum. Peat types are categorized by botanical composition and degree of coalification. In peat, the coalification process is only beginning, and lignin,... 

On the other hand, coal balls are an aggregation of calcite and/or pyrite minerals and appear to represent the early onset of the petrification of the bed (plant) material in the peat swamp, prior to complete compaction and coalification (Francis, 1961). It appears that no marine ranains have been found within a coal ball and although coal balls provide evidence of a marine intrusion, there is insufficient evidence that the original plant material grew in a totally marine environment (Stutzer, 1940). 

The primary component of coal is carbonaceous material resulting from the accumulation and decay of plant matter in marine or freshwater environments and marshes (Hessley et al. 1986). As plant matter accumulates it becomes humified and may eventually be consolidated into coal through a process called coalification. In the organic matrix, C is the major element by weight, with smaller amounts of H, O, N, and S, and many trace elements. The abundance of these trace elements is highly variable, but based on the reported trends in the affinity of elements for the organic fraction of coal (Table 1), elements such as B, Ge, Be, Ti, and V are expected to exist primarily within the organics in coal. 

Extended discussion of these speculative relationships is unwarranted until more critical information is available. The multilinear aspect of coalifi-cation described previously (3, 6) appears to be well illustrated by the Brandon woods. It seems evident that from a single plant tissue various dissimilar materials may result as products of coalification. Those described represent macerals related to the vitrinite, micrinite, and resinite maceral series. Because of the position of these materials in their respective series—i.e., only slightly metamorphosed and anatomically relatable to the woods of extant plants— their detailed study using appropriate chemical and physical methods should reveal useful information concerning the basic composition of coals of both higher and lower rank and simultaneously add to our knowledge of the coalification process. 

Dr. Spackman Several different, coalified, cell wall products have been described. In some instances the source walls were anatomically similar, and similar coalified products resulted. In other cases, the source walls were anatomically distinct and each type yielded a distinct coalified product. Moreover, the walls of each cell type seemed to respond consistently to coalification. When the walls of a particular cell type were compared with their analogs in coalified wood of a different plant genus, sometimes the products were similar, but instances were observed in which the coaly products were quite dissimilar. The latter was inferred to reflect an initial and heretofore, unrecognized difference in the nature of the source materials involved. 

The nature of the mineral matter in coal is discussed in the initial chapters. The mineral matter present in coal includes the mineral matter present in the living plants which were altered over time to produce the coal material. In addition, mineral matter has been added through the effects of subsidence and the subsequent addition of sedimentary material, and the accumulation of airborne dust or other inorganic material. Volcanic eruptions have contributed substantial mineral matter in limited areas. Furthermore, during the coalification process, water has usually percolated through the coal seams and provided additional mineral matter as well as altered the matter that was present. 

Indicative of the extent to which the accumulation of plant debris has been kept free of contamination by inorganic material (mineral matter), before burial (i.e., during peat accumulation), after burial, and during coalification... 

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