Mineral Matter Free Basis Research Articles

PETROGRAPHIC EVALUATION OF OKOBO COAL, NORTHERN ANAMBRA BASIN, NIGERIA

Petrographic studies have been carried out on coal samples from Okobo coal deposit in the northern Anambra Basin of Nigeria. The studies were carried out primarily to determine the petrographic characteristics of the coal based on its composition and vitrinite reflectance. Maceral characterization reveals the presence of the three maceral groups; vitrinite, liptinite and inertinite in all the samples. Generally, the proportion of the vitrinites and inertinites are higher than the liptinites in the samples. On mineral matter-free basis, the coal, on average, contains 65.10 % vitrinite, 11.30 % liptinite and 23.60 % inertinite. With mineral matter counted, on average, it consists of 57.10 % vitrinite, 10.20 % liptinite, 21.50 % inertinite and 11.20 % mineral matter. The coal, on average, also contains 67.30 % reactives (vitrinite + liptinite) and 32.70 % inerts (inertinite + mineral matter). It has mean vitrinite reflectance measurement of 0.54 % Romax on average. These petrographic characteristics suggest that the coal does not possess coking qualities suitable for coke making blends for metallurgical processes such as iron and steel manufacture thereby placing it on low quality and non-coking. However, it is good for electricity generation. The coal is appropriate in heating boilers and ovens in industrial heating process. The cement, glass, ceramics, paper and brick industries can use it for this purpose.

Petrographic and geochemical analysis of Barmer Basin Paleogene lignite deposits: Insights into depositional environment and paleo-climate

The current study attempts to characterize the samples from Kapurdi, Giral and Sonari lignite mines of Barmer Basin within Rajasthan Tertiary Lignite deposits using petrographic and geochemical techniques. The data generated has been studied in order to better understand the geochemical properties, hydrocarbon potential, depositional environment and paleo-climatic condition of the paleo-mires of these lignites. The proximate analysis of the samples reveals that the average ash content of the Barmer Basin is 11.93 %, the average moisture content is 14.08 %, average volatile matter yield is 42.03 % and the average fixed carbon is 31.95 %, which suggesting that the physical properties of lignite are dominated by volatile matter on dry basis. The ultimate investigation reveals the chemical properties of the lignite with the average carbon content found to be 58.79 wt%, hydrogen value 3.83 wt%, nitrogen percentage 1.60 wt% and sulphur content 2.75 wt%. This clearly indicates high sulphur concentration in Barmer lignite deposits, based on dry basis. The lignite samples subjected to FTIR studies identified aliphatic CH group, aromatic CO group, hydroxyl OH and Aldehyde HCO group. The Rock-Eval pyrolysis studies have been carried out to know the coalification profile of the deposits and hydrocarbon source rock potential. The varying behaviour between brown coal lithotype are primarily reflected by changes in oxygen index values, whereas hydrogen index values demonstrate a more pronounced correlation with coal type rather than the level of maturation. The results show the average total organic carbon (TOC) 47.29 %, S1 peak 2.18 mg HC/g, S2 peak 88.70 mg HC/g, S3 peak 19.22 % mg CO2/g, Tmax 410.53 °C, hydrogen index 219.2 mg HC/g TOC and oxygen index 46.33 mg CO2/g TOC. According to petrographic investigations, the huminite macerals dominate followed by liptinite and inertinite maceral groups in mineral matter-free basis. In all the three different lignite mines, the huminite group dominates with preserved sub-maceral ulminite indicating less transformation of structured plant matter. Reconstruction of depositional environment and paleo-climatic condition of the paleo-mires has been attempted by using organic petrographic indices. The high gelification index (GI) and low tissue preservation index (TPI) values suggest a prolonged wet environment during the decomposition of organic material, accompanied by a gradual subsidence process. The ground water influence index (GWI) and vegetation index (VI) denote ombrotrophic to mesotrophic hydrological conditions of basin at the time of deposition.

The effect of petrographically determined parameters on reductant reactivity in the production of high-carbon ferromanganese

In pyrometallurgical processes, metal oxides are reduced from molten slag through carbothermic reduction. It is of interest to evaluate the reactivity of the carbonaceous materials towards substances such as slag. Characterization techniques such as coal petrography can provide insight into the influence of feed coal properties and how they potentially dictate reductant performance. This study aimed to compare the petrographically determined organic composition of coal to reductant reactivity. Two South African medium-rank C bituminous coals and one anthracite sample were investigated together with high-carbon ferromanganese industrial slag. The reductant reactivity tests were conducted at 1500°C in a muffle furnace to assess the potential of carbonaceous reductant in reacting with the main slag components. SEM-EDS was applied to understand the extent of MnO (and to a lesser extent, SiO2) reduction from the slag. Coal 2, consisting of a greater proportion of vitrinite (59.5 vol% on a mineral matter-free basis and 54.7 vol% including mineral matter) was the most reactive reductant. The anthracite sample, with the highest inert maceral proportions (71.8 vol% including mineral matter and 76.8 vol% on a mineral matter-free basis), was the least reactive reductant.

Монголын нүүрсний ордуудын органик петрологийн судалгааны үр дүнгээс

This review includes the results of coal petrography. Maceral compositions are calculated on mineral matter free basis. Studied Mongolian coals are vitrinertite, duroclarite, clarodurite, and clarite. Vitirinte contents range from 38.8% to 96.6%, inertinte contents vary from 2.0% to 63.0%. Liptinite content is less than 13.7%.

Paradigms of biomarker and PAH distributions in lower Gondwana bituminous coal lithotypes

The present study aims to illustrate the paradigms of saturated and aromatic biomarker distributions in the lithotypes of Lower Gondwana bituminous coals (R̄r = 0.50–0.68%), perhaps for the first time. The coal samples were collected from the Early Permian Barakar Formation of the Rajmahal Basin, India. These coals mostly comprise three lithotypes, i.e., vitrain, durain, and fusain. The durain shows a considerable abundance than the other two bands and represents the bulk coal characteristics. The total organic carbon (TOC), S1, and S2 parameters from the Rock-Eval pyrolysis depict insignificant variations among the lithotypes, unlike the hydrogen index (HI), which peaks in the durain samples. The micropetrography furnishes a significant amount of liptinite macerals (30.6–51.3 vol% on the mineral matter free basis) present in the samples, dominated by the sporinite and cutinite. These hydrogen-rich macerals, being one of the crucial micropetrographic constituents, would have enhanced the HI values of the durain lithotype. The waxy nature of durain is also substantiated by the long chain-length n-alkane (LCLAs) distributions, while the plausible scarcity of wax in the lignocellulosic plant materials would have led to lower abundances of the LCLAs in vitrain (detected only from the 2D-Gas chromatography coupled with time-of-flight mass spectrometry (GC × GC-TOFMS)). Further, although the saturated diterpenoids are abundant in the durain and vitrain, their extremely low abundances (identified only through the GC × GC-TOFMS) along with the degraded LCLA signature in fusain may hint toward its source from the biomass combustion. Besides, the distributions and interrelations of the 4-, 5-, and 6-ringed polycyclic aromatic hydrocarbons (PAHs; m/z 202, 206, 228, 252, 276, and 278), like fluoranthene, pyrene, chrysene, benzo[g,h,i]perylene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, benzo[e]pyrene, and the isomers of the dimethylphenanthrene, dibenzanthracene, and benzochrysene further support the pyrogenic origin of the fusain lithotype. Meanwhile, these PAHS would have derived from diagenetic/catagenetic origin to mixed sources (diagenetic/catagenetic maturation of organic matter and combustion origin) in vitrain. The durain shows a mixed to pyrogenic origin of these PAHs and represents the PAH distributions of the bulk coal samples. Besides, the thermal maturity assessment of these lithotypes may suggest that the molecular parameters respond more sensitively to the thermal maturation compared to the bulk organic geochemical proxies.

Petrology of the Parvadeh coals, Tabas Basin, Iran

The Tabas Basin is in the Tabas Block in the central part of Iran, and it contains Iran’s largest coal deposits, mostly in the Parvadeh Coalfield. The basin is structurally characterised by regional scale thrust faults and orthogonal strike-slip faults that segregate the coalfields into different areas namely Parvadeh (P) I to IV. The coals under study are in the upper Triassic Nayband Formation. Samples were collected from underground coal mines in PI, PII, PIII, and core from PIV, and prepared for petrographic analysis. The resulting vitrinite reflectance varies between 1.13% and 1.54%, which places the coals into medium volatile bituminous rank. In all samples, the vitrinite content is significantly higher than the inertinite followed by minor amounts of liptinite, mostly secondary exsudatinite. The samples also contain abundant pseudovitrinite, which can be above 40% (volume, mineral matter free basis). The maceral composition and moderate to high mineral matter with common framboidal pyrite and siderite corroborate previous interpretations of the Parvadeh coals forming in topogenous to transitional peatlands in paralic to fluvial palaeoenvironments. However, this study makes additional interpretations of the coalification history of the Parvadeh coals and the occurrence of pseudovitrinite. The coals commonly contain meta-cutinite and associated meta-exsudatinite, and fluorescing exsudatinite that permeates carbargillite lenses, lumina of inertinite macerals, and the slits of the pseudovitrinite. This suggests at least two stages of hydrocarbon generation occurred in the Parvadeh coals: the first phase during entry into the oil window and later devolatilisation to meta- exsudatinite in the early gas window; the second phase post-dates this and could be generated internally from the vitrinite else migrated from surrounding organic-rich rocks in the interburdens of the Nayband Formation. The fact that the pseudovitrinite slits are filled with exsudatinite but not meta-exsudatinite indicates that pseudovitrinite formed just before during partial devolatilisation or contemporaneous with the second generation of exsudatinite. Epigenetic mineralisation includes massive pyrite and dolomite in the fractures, indicative of potential hydrothermal circulation that may also be related to the second phase of hydrocarbon generation as exsudatinite is found trapped in the intracrystalline spaces of the carbonates.

Geochemical characteristics, origin and forms of sulphur distribution in the Talcher coalfield, India

Geochemical studies conducted on samples from the Talcher coal field can help elucidate the occurrence, origin and different forms of Sulphur in the area. In this coalfield, sulphur is present as organic sulphur, pyritic sulphur, and sulphate sulphur. The total sulphur concentration ranges from 0.5% to 1.13%, which falls under category of low-sulphur coals. Organic sulphur accounts for 70%, and pyritic sulphur accounts for 25% of the total sulphur in the Talcher coal. The presence of a minor proportion of sulphate sulphur (approximately ≤ 5%) indicates that Talcher coals are formed under non-marine environmental conditions. Results from proximate analysis expose the gross composition of coal. The air dried results indicate that, the moisture content varies from 2.6 to 4.8%, ash content ranges from 29.7 to 45.6%, volatile matter ranges from 24.54 to 29.65%, and fixed carbon content varies from 25.96 to 37.25%. It is observed that when the ash percentage of coal samples is less than 40%, the gross calorific value of the Talcher coalfield ranges from 4000 to 5000 kcal/kg, and when the ash percentage of the coal samples is greater than 40%, the gross calorific value is less than 3000 kcal/kg. The elemental compositions of the Talcher coalfield were also determined based on the dry mineral matter free basis. Carbon, hydrogen, nitrogen, sulphur, and oxygen content were determined. Macerals and mineral matter were studied using a coal Petrological microscope. It was observed that macerals account for 69% of the total mass of coal while pyrite represent 1.8% and other minerals 29.28%. Results obtained using the field emission scanning electron microscope technique show that the major sulphide minerals present in the Talcher coals are pyrite (FeS2) and marcasite (FeS2), with pyrite being the more common. Sphalerite (ZnS) was found in some samples. The study has revealed the geochemical characteristics, origin and forms of sulphur distribution in the Talcher coalfield.

Influence of coal composition and maturity on methane storage capacity of coals of Raniganj Coalfield, India

Methane generation primarily depends on the quantity, type and structure of kerogens and is controlled by temperature to which the precursor material is subjected over the geologic time whereas the gas-in-place depends on the storage capacity and burial history. The Raniganj Coalfield of India hosts significant reserves of good quality coals of Permian age belonging to two formations, Barakar and Raniganj. The adsorption characteristics of the nine regional (R-I to R-IX) and three local seams from Raniganj Formation of south-western part of the coalfield is thoroughly investigated in the light of reflectance, petrography and chemical composition for their CBM potential. Ash (A), moisture (M), volatile matter (VM) and fixed carbon (FC) of these coals range within 12.8–37.3%, 1.1–4.0%, 31.7–51.1% (daf) and 48.9–68.3% (daf), respectively. Carbon (C) varies within the range 77.0–86.8% (dmmf) and reflectance (Rr) within 0.62–0.87%. The coals are high volatile gas prone orthohydrous bituminous type. Both C and Rr increase, and M and VM decrease with depth. Vitrinite ranges mostly within 64.5–85.5%, inertinite 4.8–24.1% and liptinite below 15%, on mineral matter free basis. Most of the samples fall in Type-III kerogen and few are transitional to Type-II and Type-III.Gas content of the samples lies between 3.08 and 14.96 cc/g, on daf basis and generally increases with depth. Langmuir volume (VL) for the coals varies between 17.4 and 29.8 cc/g (daf) and exhibits a moderately positive linear relationship with increase in depth (R2 = 0.58). Reflectance shows a strong linear positive relationship (R2 = 0.70) with Langmuir volume indicating the development of additional micropores with rank enhancement, thereby providing more surface area for adsorption. Gas content results are encouraging though the seams are considerably undersaturated. A very good correlation is observed for the combined effect of ash, moisture and carbon on volume adsorbed for the studied coals and can be used to predict adsorption capacity from compositional data.

Influence of inherent mineral matrix on the product yield and characterization from Huadian oil shale pyrolysis

Huadian oil shale was subjected to step-wise acid treatment to remove inherent carbonate and silicate minerals. The original oil shale and its demineralization products (carbonate- and carbonate-silicate-free oil shale samples) were pyrolyzed in a fixed-bed pyrolyzer to determine the mineral matrix effect on product yield and characteristics of shale oil and gases. The shale oil yields of original, carbonate-free, and carbonate-silicate-free oil shale samples were 50.4 wt.%, 44.3 wt.%, and 50.3 wt.% (values on dry and mineral matter-free basis), respectively, which indicated that carbonates promote, while silicates suppress, shale oil production. Coking of aromatic compounds appeared to be the dominant mechanism accounting for the variation of the shale oil yield. Elimination of the carbonate minerals decreased the nitrogen- and oxygen-containing compounds of shale oil, while removal of silicates increased the oxygenated compounds. Both carbonate and silicate minerals decreased the atomic H/C ratio of shale oil. Silicates promoted the cracking and aromatization of aliphatic hydrocarbons, which increased the short-chain aliphatic hydrocarbons and aromatic hydrocarbons of shale oil, as well as C1–C4 hydrocarbons and H2 yields. On the contrary, carbonates suppressed the cracking of long chain aliphatic hydrocarbons.

Organic Geochemistry and Petrology of Mudrocks from the Upper Carboniferous Batamayineishan Formation, Wulungu Area, Junggar Basin, China: Implications for Petroleum Exploration

The hydrocarbon generation potential of the Carboniferous Batamayineishan mudrocks has been overlooked for a long time. In this study, organic petrology and geochemistry were used to determine the sedimentary environments, organic matter (OM) type, and organic maturity of the Carboniferous Batamayineishan source rocks, collected from outcrops, Wulungu area, Junggar Basin, China. The maceral composition of the studied samples is dominated by vitrinite and inertinite, ranging from 40 vol % to 100 vol % and from 0 vol % to 60 vol % on a mineral matter free basis, respectively. Liptinite macerals, mainly as lamalginites, are only present in trace amounts in several sediments. Vitrinite reflectance values are 0.67% to 2.78%. TOC values are high in these samples, whereas the S1, S2, and HI are very low. Pr/Ph ratios, the plot of Pr/n-C17 versus Ph/n-C18, DBT/P versus Pr/Ph, and ternary of fluorene, dibenzothiophene, and dibenzofuran indicate that anoxic saline environments prevailed during deposition of the Bat...

Chemical and mineralogical composition of Kathara Coal, East Bokaro Coalfield, India

Utilisation of any coal primarily depends on its organic constituents. However, the inorganic constituents i.e., mineral matter present in the coal can decide its end uses. Therefore, the study of mineral matter in coal is an inevitable and such type of studies in India is very scanty. In this paper, we present the characters of a relatively low-ash non-coking coal from Kathara mines, East Bokaro coalfield, India with emphasis on its inorganic constituents and mineral matter. The coal is characterised by 22.56wt% ash (dry basis), 28.78wt% volatile matter (dry basis), and 48.66wt% fixed carbon (dry basis). Modal analysis by optical microscopy revealed 53.6vol% vitrinite, 38.3vol% inertinite, 8.1vol% liptinite on the mineral matter free basis (mmf), and 25.1vol% mineral matter. The minerals present in this coal are dominantly clay, quartz and siderite with a minor quantity of hematite, magnetite, goethite and pyrite. Electron micro-probe studies revealed trace presence of sphalerite, baddeleyite, and some altered magnesium silicate. The total sulphur content of this coal is found to be 1.16wt% on dry ash free basis (daf). Since the majority of the minerals, although fine in size, occur as independent phases with distinct and weak grain boundaries with the macerals, the coal shall be susceptible for beneficiation and the cleaner product can find applications in metallurgical industries for partial substitution in coke making because the mean vitrinite reflectance of this coal is 0.70%.

Dunkard Group coal beds: Palynology, coal petrography and geochemistry

Coal beds that occur in the Dunkard Group are typically thin (avg. 0.3m), and are high in ash yield (avg. 27.8%) and total sulfur content (avg. 5.1%). Petrographically, Dunkard coals are high in vitrinite (avg. 83.1%, mmf), with correspondingly low to moderate amounts of liptinite (avg. 2.1%, mmf) and inertinite (avg. 13.8%, mmf). Palynologically, Dunkard coal beds are all dominated by tree fern spore taxa (avg. 96.3%), especially Punctatisporites minutus (avg. 82.8%). Calamite spores are the second most abundant plant group (avg. 2.4%), with others (lycopods, small ferns, Cordaites and other gymnosperms) having very minor representation. Overall, the coal palynofloras are strongly dominated by lowland plants (ferns and Calamites), with only rare occurrences of bisaccate–striate conifer pollen.Coal beds of the underlying Monongahela Group (Pittsburgh, Redstone, Sewickley and Waynesburg) are thicker (avg. 1.6m), and are lower in ash (avg. 13.4%) and sulfur (avg. 3.3%) than their Dunkard counterparts. Petrographically, Monongahela Group coals are very similar to Dunkard Group coals, when compared on a mineral matter free basis; coal beds that occur in both groups are strongly dominated by vitrinite macerals. Monongahela Group coals are also palynologically very similar to Dunkard Group coals, with tree fern spore taxa dominating. A coal bed of early Permian age from west-central Texas is also similar, petrographically and palynologically, to Dunkard and Monongahela coals, being vitrinite and tree fern spore dominant.The almost complete lack of coniferous pollen in Dunkard coals led earlier workers to conclude that the Dunkard was entirely Late Pennsylvanian, and not Permian, in age. However, it is now known that Late Pennsylvania lowland floras persisted into the Dunkard, especially during wet intervals. As earlier interpretations were based primarily on spore and pollen floras from coal beds, the lack of conifer pollen in Dunkard coals is probably the result of a sampling bias. Because of this ecological bias, coal palynology is a poor proxy for age dating Dunkard Group coals.Collectively, Dunkard swamps were all planar and topogenous, their formation being controlled by topography and moisture availability. A progressive decrease in wet intervals, both in terms of frequency and duration, during the Dunkard was the major control on peat accumulation and preservation. Collectively, moisture limitation appears to be the principle factor that controlled the formation of Dunkard Group coals.

The Coalbed Methane (CBM) Potential and CO2 Storage Capacity of the Santa Terezinha Coalfield, Paraná Basin, Brazil – 3D Modelling, and Coal and Carbonaceous Shale Characteristics and Related Desorption and Adsorption Capacities in Samples from Exploration Borehole CBM001-ST-RS

This study investigates the CBM generation and CO2 storage capacity of the coal-bearing Permian age Rio Bonito Formation in the Santa Terezinha Coalfield, Paraná Basin, Brazil. In order to assess the volumetrics of the coal seams a fourth-order sequence stratigraphic framework of the coal-bearing succession was established based on parasequence boundaries. A 3D geometric model based on data from 36 well logs was developed, and enabled subdivision of the study area into regions with very different CBM potential, due to variable cumulative coal thickness, depths and presence/absence of diabase. Strata of the coal-bearing Rio Bonito Formation were penetrated in well CBM001-ST-RS at a depth of 575.70 to 638.35 m, from which twelve coal seams and carbonaceous shales, ranging in thickness from 0.15 to 1.77 m, were retrieved for analysis. Gas desorption values range from 0.3 to 2.2 cm3/g. Gas composition is dominated by methane (> 94 Vol%). Gas isotopic analyses suggest a mixed biogenic and thermogenic origin. Vitrinite reflectance indicate a rank of high volatile A bituminous coal, with semi-anthracite occurring in contact with igneous rocks. The majority of the samples has vitrinite group contents > 50 Vol%, mineral matter-free basis. Ash yields range from 42.1 to 92.8 wt.%, whereas sulphur contents range from 0.1 to 7.7 wt.%. Volatile matter and calorific values (dry ash-free) range from 37.6 to 79.4 wt.%, and 2352 to 8107 kcal/kg, respectively. Mineral composition of the samples is dominated by quartz and kaolinite, whereas major element analyses show that SiO2 is most abundant. The 3D model allowed volumetric calculation for the coal seams and formed the basis for calculations of gas content and CO2 storage capacity. According to the 3D model the four coal-bearing parasequences of the study area contain a coal volume on the order of 3212 × 10 6 m3 suggesting a resource base of 5.5 × 109 m3 of methane associated with the coal seams and carbonaceous shales of the study area. The methane and carbon dioxide sorption capacities show a high positive correlation with TOC content. The coal seams appear to be undersaturated, since sorption capacity is significantly higher than the desorbed gas volume. The CO2 sorption capacity at mean reservoir pressure was up to 7 times higher than the methane sorption capacity. Based upon sorption capacities and reservoir conditions, a storage potential of 13.8 Gt CO2 in coal seams and carbonaceous shales of the study area is estimated.

Organic petrology of Carbondale Formation coal beds and marine roof shales in Western Kentucky, Eastern Interior (Illinois) Basin, USA

Abstract Ten samples of Carbondale Formation (late Middle Pennsylvanian, Westphalian D) roof shale strata from the Western Kentucky Coal Field (Eastern Interior Basin, USA) were analyzed petrographically to gain a better understanding of the organic composition of the shales. The samples were collected in conjunction with a coal bed methane exploration program, so a direct comparison of the organic composition of the shales, and the coal beds that directly underlie them, could be made. Petrographically, total vitrinite contents in the shales average 20.8% (mineral matter free basis, mmf), which is significantly lower than the average vitrinite content of Carbondale Formation coal beds (avg. 81.8%, mmf; n = 32). In contrast, total liptinite contents average 49.7% (mmf) in the shales, which is significantly higher than the average liptinite content of Carbondale coals (avg. 7.0%, mmf). Amorphinite and bituminite were found to be the most abundant liptinite macerals in the shales, but were not recorded from the coal samples. Likewise, total inertinite contents were much higher in the shales (avg. 29.6%, mmf), than in the coals (avg. 11.0%, mmf). A type of macrinite identified as “granular macrinite” was the dominant inertinite maceral in the shales, but was absent in the coal samples. Although the average desorbed gas contents of Carbondale Formation coals and shales are low and currently uneconomical (avg. 0.9 ml/g [28.8 scf/ton] for the shales, 2.4 ml/g [76.9 scf/ton] for the coals, as received basis), they nonetheless represent a potential future gas resource.

Comparison of the R70 self-heating rate of New Zealand and Australian coals to Suggate rank parameter

Samples from New Zealand and Australia have been tested in an adiabatic oven to assess the effect of rank on the R 70 self-heating rate of coal. A non-linear relationship can be defined for coals from both countries using the revised Suggate rank ( S r) parameter. Subbituminous coals have the highest R 70 self-heating rate values, which are 20 times that of high volatile A bituminous coals on a dry mineral matter free basis (∼ 1 cf. 20 °C h − 1). However, the moderating effects of moisture and mineral matter can reduce this difference to only 2–3 times for coal in-situ.

Antimony and arsenic anomalies in the coal seams from the Gokler coalfield, Gediz, Turkey

The Gokler coalfield in the western part of Turkey mainly contains high sulphur (4.5% to 11.5% on a dry basis) bituminous (0.5% to 0.95% Rr) coals of Middle Miocene age. The Gokler coals from Buyuk, Kucuk and unnamed seams are in general characterised on a mineral matter-free basis by higher amounts of macerals of the vitrinite group (av. 95.5%) than liptinite (av. 2.5%) and inertinite (av. 2%) contents. Geochemical characterisation of 45 coal samples on a whole-coal dry basis was achieved using an energy dispersive, polarised X-ray fluorescence (EDP-XRF) spectrometer. The Gokler coals proved to be anomalously enriched in Sb (8.3–2347 ppm; av. 134 ppm) and As (170–3854 ppm; av. 833 ppm) in the samples in comparison with range values for most world coals. Sb and As are respectively associated with epigenetic stibnite and iron sulfides, both of which formed in microfractures and micropores in the Gokler coals. Stibnite occurs mainly as prismatic crystals and less radial crystals. Scanning electron microscopy (SEM) shows that some stibnites are chemically pure, while others contain minor Fe. Epigenetic Fe sulfides (pyrite and marcasite) typically include (in addition to Fe and S) minor amounts of As and trace amounts of Zn. As and Zn are below the SEM detection levels in syngenetic framboidal pyrites. Epigenetic calcites in the samples consist mainly of Mg and Fe and trace amounts of Sr. All epigenetic minerals, such as stibnite, iron sulfides, calcite and quartz, indicated that the Gokler coals were mainly effected by post-Miocene hydrothermal mineralisations.

Liptinite macerals in Singrauli coals, India: their characterization and assessment

The record of liptinite macerals in Indian Permian coals has been uniformly quite low under normal reflected light. In fact, high inherent clastic minerals intimately associated with liptinite macerals in these coals tends to mask them, at times, completely, obstructing identification and for this reason they are considered to be poor in liptinite content. Petrographic investigations carried out on Early Permian Turra coal seam and Late Permian Jhingurdah coal seam of Singrauli Coalfield, under blue light excitation, recorded appreciably high amounts of liptinite macerals (13-57% on mineral matter-free basis) as against maximum up to 19 per cent (m.m.f basis) under normal reflected light. The liptinite macerals in these coals are formed chiefly by sporinite (7-40%) and liptodetrinite (1-16%). Cutinite, suberinite, resinite, alginate, exsudatinite and fluorinate are the other macerals of liptinite group together occurring in only subordinate amounts.
 The coals of the Turra seam associated with Barakar Formation have relatively higher liptinite content than that of the Jhingurdah seam of Raniganj Formation. Such high concentration of sporinite has not been reported so far from the Indian Permian coals. The increase in liptinite/sporinite content coincides with increase in mineral matter content in many instances, i.e., dull bands normally have high liptinite content. The sporinite concentration in dull coal bands of the Permian coal seams mark the presence of semi-cannel or cannel coal bands.

Petrology and facies studies of the carboniferous coals at Mabou mines and inverness in comparison with those of the Port Hood, St. Rose and Sydney coalfields of Cape Breton Island, Nova Scotia, Canada

The Mabou-Inverness coal-bearing section is exposed along the shores of small land areas that form part of the large Carboniferous Basin beneath the Gulf of St. Lawrence. The Westphalian C and D section measures 930 m and contains 26 seams that are 0.3-3.8 m thick. The coals have a rank of high volatile “B” to high volatile “C” bituminous, with vitrinite reflectance values of 0.6-0.7% R max. Petrographic composition, in terms of microlithotypes and macerals, was determined on column samples of thirteen seams, and is illustrated in percentage diagrams. A normal banded humic coal is indicated in which the bright-banded variety predominates. Average ash, sulphur and volatile matter contents are, resectively, 12.4%, 3.7% and 39% (on mineral matter-free basis). Coal facies has been determined from the microlithotypes and is expressed in terms of forest moor (FM), reed moor (RM) and open moor (OM). In addition, whole-seam facies designations are given also and are compared with those of the Sydney, Port Hood and St. Rose coalfields. They show that at Mabou Mines the RM facies greatly predominates, but at Inverness the FM facies is the dominant feature, as is the case at Sydney, while at Port Hood OM conditions prevailed. Higher paleo-groundwater tables at Mabou Mines and Port Hood are deduced from this and are supported by the presence of Anthracomya-bearing black shales. Marceral-based facies plots suggest that the Mabou coals originated in the piedmont zone of the Hercynean foreland region, possibly in a southern embayment bordered by upland areas. Further north, however, in the Inverness area, the coal swamps may have extended uninterrupted to the Sydney field and may have covered the pre-Carboniferous Cape Breton Highlands before their uplift in Early Permian time.

Coalbed Methane Characteristics of Gates Formation Coals, Northeastern British Columbia: Effect of Maceral Composition

The majority of research reported on methane adsorption characteristics of coal seams has focused on vitrinite-rich coals. However, western Canadian coals are more inertinite-rich than those of the western United States and are shown to differ in gas adsorption characteristics. The influence of maceral composition upon gas adsorption characteristics of medium-volatile coal samples from the middle Cretaceous Gates Formation of northeastern British Columbia was investigated. Lithotype (coal facies) samples were analyzed for surface area, maceral and mineral composition, and methane adsorption; standard coal analyses were also performed (proximate, low-temperature ash, and equilibrium moisture). The vitrinite content of the samples analyzed ranges from 18 to 95% (vol. %, min ral matter free); the ash yield varies from 4.4 to 33.7% (wt. %). Both maceral composition and mineral matter content have an important influence on adsorption characteristics as indicated by carbon dioxide surface areas and methane adsorption isotherms. On a mineral matter-free basis, the amount of methane adsorbed generally increases with vitrinite enrichment. The lowest methane adsorption occurs in the sample with the highest inertinite content. Carbon dioxide surface areas of the lithotypes range from 87 to 176 m2/g on a raw-coal basis, and from 99 to 184 m2/g on a mineral matter-free basis. Surface area generally decreases with increased mineral matter content and increases with increased vitrinite content. The increase in adsorption of both methane and carbon dioxide with increased vitrinite concentration is interpreted a resulting from differences in the pore size distribution of vitrinite and inertinite: vitrinite is predominantly microporous whereas inertinite is meso- to macroporous. The monolayer volumes of carbon dioxide (as calculated from the DubininRadushkevich equation) are higher than those of methane (as determined from the Langmuir equation), but are correlated. The methane adsorption isotherms and surface area data indicate that the maceral compositional variations in coal are at least as significant as coal rank in determining the potential volume of adsorbed methane and thus the coalbed methane potential of a deposit.

Determination of organic oxygen content of coals

Fast neutron activation analysis has been used to determine organic oxygen (O org) content of coals by subtracting the oxygen content of the mineral matter from the total oxygen content of the coals. Mineral matter was isolated by low temperature ashing in an oxygen plasma. Optimum ashing conditions produce minimal changes in chemical composition of mineral matter; these changes were taken into account when calculating the O org content. The O org contents of whole coals are substantially different — in some cases by as much as 47% — from the ASTM oxygen contents and those calculated on a dry, mineral matter free basis from the ultimate analysis data. Excellent agreement between the FNAA O org contents of the whole and demineralized coals lends support to the reliability of this experimental approach.