Ž . International Journal of Coal Geology 41 1999 257–274 Composition and organic maturity of Middle Jurassic coals, North-East Greenland: evidence for liptinite-induced suppression of huminite reflectance H.I. Petersen ) , H. Vosgerau Geological SurÕey of Denmark and Greenland, ThoraÕej 8, Copenhagen DK-2400 NV, Denmark Received 18 August 1998; accepted 18 March 1999 Abstract Middle Jurassic coals from Kuhn Ø, North-East Greenland, may contain up to 85 vol.% Ž . liptinite, principally resinite up to 68.6 vol.% . The coals are thus petrographically comparable to the Middle Jurassic Muslingebjerg Formation coals at Hochstetter Forland approximately 40–50 Ž km to the north, and they are inherently excellent petroleum source rocks. Liptinite-poor F6.0 . vol.% coal samples from both Kuhn Ø and Hochstetter Forland yield mean random huminite reflectance values of 0.49–0.53%R , implying a rank of sub-bituminous A. Above a threshold o value somewhere between 3 and 24 vol.% resinite and 6 and 35 vol.% total liptinite, significant reflectance suppression is induced, and between 24 and 69 vol.% resinite and 35 and 85 vol.% total liptinite, a nearly linear inverse relationship exists between the content of liptiniterresinite and the mean random reflectance values. At the highest liptiniterresinite contents, reflectance suppression may be up to 0.23%R . The reflectance suppression is related to bitumen-adsorption o caused by bitumen-expulsion from resinite, and total reflectance distributions of the huminite fractions suggest that the reflectance of all huminite macerals is lowered with increasing liptiniterresinite content. q 1999 Elsevier Science B.V. All rights reserved. Keywords: liptinite; resinite; reflectance suppression; Middle Jurassic; North-East Greenland ) Corresponding author. Tel.: q45-38-14-23-45; Fax: q45-38-14-20-50; E-mail: hip@geus.dk 0166-5162r99r$ - see front matter q 1999 Elsevier Science B.V. All rights reserved. Ž . PII: S0166-5162 99 00022-1