The petrographic composition of world coals. Statistical results obtained from a literature survey with reference to coal type (maceral composition)

This paper presents a statistical study concerning the petrographic composition of World coals in terms of Vitrinite (V), Liptinite (L), and Inertinite (I) composition. A comparison between VLI-compositions of coals from different ages, facies, continents and countries/territories was done. North Atlantic Palaeozoic coals show an average petrografic composition of VLI = 70-12-18, while Gondwana Palaeozoic coals show VLI = 52-8-40. Mesozoic coals from 'North Atlantic' territories also show a higher V-content (74) than 'Gondwana' coals of the same age (65), and a lower I-content (18) than 'Gondwana' (21). 'North Atlantic' and 'Gondwana' Tertiary coals have similar VLI-compositions (81-10-9 and 82-8-10, respectively). Data from Quaternary coals are only available for 'North Atlantic' and these show a VLI-composition of 88-6-6, Considering the ECE-UN classification (1990) of coals into Vitric, Liptic, Fusic, Trimaceric-I and Trimaceric-L, a study was carried out to determine the percentages of all coals falling into each of these categories. The amount of Vitric coals increases constantly from Palaeozoic (54.5%) to Quaternary (98.6%), with values of 68.4% and 90.2% for Mesozoic and Tertiary coals, respectively. On the opposite, the amounts of Fusic and Trimaceric-I coals decrease in the same way. Liptic and Trimaceric-L coals do not show a regular variation. Based upon the results, an attempt is made to establish an alternative boundary limit for Fusic coals (I > 55%), to the one proposed by ECE-UN (I > 50%). A new proposal for a change of terminology is presented. (C) 1999 Elsevier Science B.V. All rights reserved.