Identification of alginite and bituminite in rocks other than coal. 2006, 2009, and 2011 round robin exercises of the ICCP Identification of Dispersed Organic Matter Working Group

• Published in: International journal of coal geology Vol. 178; pp. 26 - 38
• Main Authors: Kus, J., Araujo, C.V., Borrego, A.G., Flores, D., Hackley, P.C., Hámor-Vidó, M., Kalaitzidis, S., Kommeren, C.J., Kwiecińska, B., Mastalerz, M., Mendonça Filho, J.G., Menezes, T.R., Misz-Kennan, M., Nowak, G.J., Petersen, H.I., Rallakis, D., Suárez-Ruiz, I., Sýkorová, I., Životić, D.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.06.2017
• Subjects: Alginite; Bituminite; ICCP; Lamalginite; Maceral; Round robin exercises; Telalginite; Telalginite; Alginite; ICCP; Round robin exercises; Lamalginite; Bituminite; Maceral
• ISSN: 0166-5162; 1872-7840
• DOI: 10.1016/j.coal.2017.04.013

The paper presents results of round robin exercises on photomicrograph-based identification of dispersed organic matter in source rocks that represent a range of marine and lacustrine deposits from worldwide localities and cover a range of thermal maturities. The round robin exercises were conducted by the Identification of Dispersed Organic Matter Working Group (IDOM WG) of the International Committee for Coal and Organic Petrology (ICCP). The round robin exercises aimed to (1) assess the applicability of the established ICCP definitions of bituminite, (2) identify deficiencies and improve the existing nomenclatures, and (3) provide a basis for the revision of the bituminite and alginite definitions in the ICCP Handbook (Taylor et al., 1998). Three round robin exercises performed in 2006, 2009 and 2011 involved 18 participants from research laboratories at universities and within government and industry. Participants were asked to identify macerals on the basis of existing definitions in 129 photomicrographs taken in incident white light and fluorescent mode and also in fluorescence light mode at prolonged (15min) blue light irradiation. The results indicate that the definition of telalginite permits its positive and satisfactory agreement among the participants. In contrast, the descriptive characteristics of lamalginite referring to film-like appearance (filamentous) and lack of inner or outer structure are insufficient and inadequate to enable an unequivocal discrimination between it and telalginite. Furthermore, based on the amorphous nature of bituminite and lack of adherence to its established description and character (Taylor et al., 1998), the highest discrepancies were observed in its identification. Differentiation of bituminite from a fluorescent groundmass and in some cases from lamalginite proved to be particularly challenging. The findings of these round robin exercises are useful for improving the identification of sedimentary organic matter in source rocks and may be an important foundation for the modification of the ICCP definitions of alginite and bituminite. •Photomicrograph-based identification of alginite and bituminite is based on ICCP liptinite definitions.•The definition of telalginite enables a satisfactory agreement with the observation of discrete algal bodies among the participants.•Filamentous appearance and lack of inner structure or outer ornamentation of lamalginite is inadequate for its identification.•Transitions from lamalginite to bituminite and from bituminite to mineral-bituminous groundmass posed major identification problems.•The term “unstructured” in terms of lacking a definite shape or lacking internal structure requires further clarification.