ARTIFICIAL MATURATION OF AN IMMATURE SULFUR AND ORGANIC-MATTER RICH LIMESTONE FROM THE GHAREB FORMATION, JORDAN

An immature (R-o = 0.39%), S-rich (S-org/C = 0.07), organic matter-ric h (19.6 wt.% TOC) limestone from the Ghareb Formation (Upper Cretaceou s) in Jordan was artificially matured by hydrous pyrolysis (200, 220,. .., 300 degrees C; 72 h) to study the effect of progressive diagenesis and early catagenesis on the amounts and distributions of hydrocarbon s, organic sulfur compounds and S-rich geomacromolecules. The use of i nternal standards allowed the determination of absolute amounts. With increasing thermal maturation, large amounts of alkanes and alkylthiop henes with predominantly linear carbon skeletons are generated from th e kerogen. The alkylthiophene isomer distributions do not change signi ficantly with increasing thermal maturation, indicating the applicabil ity of alkylthiophenes as biomarkers at relatively high levels of ther mal maturity. For a given carbon skeleton, the saturated hydrocarbon, alkylthiophenes and alkylbenzo[b]thiophenes are stable forms at relati vely high temperatures, whereas the alkylsulfides are not stable. The large amount of alkylthiophenes produced relative to the alkanes may b e explained by the large number of monosulfide links per carbon skelet on. These results are in good agreement with those obtained previously for an artificial maturation series of an immature S-rich sample from the Gessoso-solfifera Formation. (C) 1998 Elsevier Science Ltd. All r ights reserved.