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Four different sulfur-containing coals (from low to high) (A, B, C and D) obtained from three different geographical locations of the North Eastern Region (NER) of India were studied for the control of ash fusion temperature (AFT) by oxides, generated via in-situ process, during coal combustion. The Meghalaya (B and C) and Nagaland (D) coals were found to contain high ash content in comparison to that of Assam coal (A). Meghalaya coals (B and C) were found to be better as they produce ash in greater quantity of acidic components (Al2O3 and SiO2) and lower amount of basic components (Fe, Ca, Mg, Na and K oxides). This results in lower value of slagging and fouling indices of the Meghalaya coals, and hence increases their AFT. X-ray diffraction studies (XRD) and atomic absorption spectroscopy (AAS) were also performed for qualitative mineralogy and elemental analyses. Statistical tools. such as correlation coefficient and principal component analysis (PCA), confirmed that the low-to-medium AFTs of the coal samples are due to the presence of various fluxing agents (such as K, Fe, Mg and Ca). Ternary phase diagram indicates the fact that the Meghalaya coals (B and C) have higher amount of Aℓ2O3 with lower Fe2O3 contents, resulting in increased fusion temperature. [ABSTRACT FROM AUTHOR]

Considering the importance of REE resources, that are used in several high-technology areas, the present study aims to assess the potentiality of REE in the sedimentary sequence of Shella and Kopili formations (350m and 60m respectively) in East Jaintia Hills district, Meghalaya. A well-developed sedimentary sequence of Shella and Kopili formations of Jaintia Group, middle to upper Eocene age, are exposed in Jaintia Hills. The semi-quantitative (SEM-EDX) analysis of black shale and carbonaceous shale indicate the presence of monazite and xenotime phases. The REE+Y concentration ranges from 77.1 to 1168.7 ppm (avg. 295 ppm). The LREEs (La-Eu) ranges from 55 to 782 ppm (avg. 211.3 ppm), whereas HREEs (Gd-Lu+Y) ranges from 18.8 to 385.9 ppm (avg. 83.7 ppm). Nd ranges from 15.8 to 229.3 ppm (avg. 66.1 ppm). The REE+Y concentration in black shale yields 1168.7 ppm. Further, REE in two coal samples yields 111.6 and 63.2 ppm. REE shows a strong positive correlation with Zr, Y, U and Th, weak positive correlation with V and weak negative correlation with Sc. The REE concentrations in coal samples are relatively higher than previously reported REE concentrations and are comparable with worldwide average values of REE. The REE concentrations in black shale and coal are significant for further exploration. [ABSTRACT FROM AUTHOR]

The Eocene coal deposits of west Daranggiri coalfield of Meghalaya is hosted in the Tura Formation. The coals are perhydrous in composition, rich in organic matters and poor in mineral content. The organic matters are dominantly represented by Type III kerogens contributed by terrestrial plants. Petrographic analysis confirms dominance of vitrinite with subordinate amounts of liptinite and inertinite. Maturity parameters like vitrinite reflectance, Rock-Eval Tmax, volatile matter content etc. indicate low thermal maturity of the coal within lignite to subbituminous rank. The coals are immature to act as petroleum source rock despite having high-quality organic matters. However, perhydrous nature of the organic matters and significant amount of liptinite macerals suggest that despite low thermal maturity, the coals might have some capacity to generate liquid hydrocarbon. High liptinite and perhydrous vitrinite contents of the coal may result in suppression of vitrinite reflectance, thus, underestimation of maturity. Presence of exsudatinite in the coal also points to generation of some liquid hydrocarbon. The coal deposits possess excellent potential for hydrogenation industry. The coals are characterized by very high rate of conversion from coal to oil and high oil yield. Indices of facies critical maceral association indicate the origin of the coal in wet swamps under mildly oxic to the anoxic environment with moist hydrodynamic condition. The high sulphur content of the coal, association of marine palynological assemblage and presence of limestone beds at the top of the Tura Formation point to nearshore environment of deposition. [ABSTRACT FROM AUTHOR]