Fuel, Vol.107, 74-83, 2013
Organic geochemistry of the asphaltite occurrences in the Gumushacikoy (Amasya) Area, Northern Turkey
The asphaltites are exposed in three different locations (Gokcukur Plato, Kagnici, and Saraycik villages) in NW Gumushacikoy (Amasya), Northern Turkey. In this study, organic geochemical characteristics of the asphaltite occurrences were investigated and correlated with each other. The Saraycik asphaltite occurrences are found in the Eosen unit that consists of mainly sandstone, silt-stone, claystone, and limestone. The asphaltites are located in the joint systems of this unit and porosity of sandstone and siltstone. Kagnici asphaltite occurrences are found in agglomerates and tuffs of the Eocene age. The asphaltite occurrences in agglomerates and tuffs fill primary porosity and have an irregular and patchy distribution. Gokcukur asphaltites are found in the ophiolitic melange of the Upper Cretaceous age. The asphaltite occurrences are located in the joint systems of this formation. TOC values of Saraycik, Kagnici and Gokcukur asphaltite samples are 1.16%, 9.35% and 21.22% and respective HI values are 757, 92 and 306 mg HC/g TOC. The delta C-13 values of saturated and aromatic fractions from the asphaltites are similar, but the aromatic fraction of Gokcukur asphaltite sample is enrichment in delta C-13 compared with the others. n-Alkane, isoprenoid, and aromatic fractions were almost completely depleted in the gas chromatograms of Saraycik and Kagnici asphaltite samples. n-Alkanes and isoprenoids are recorded in a low amount in gas chromatograms of Gokcukur asphaltites. The asphaltite samples from Kagnici, Saraycik, and Gokcukur locations show similar diasterane and sterane distributions in the m/z 217 mass chromatograms. These asphaltite samples have lower diasterane and higher sterane abundances. In all the asphaltite samples, C-27, C-28, and C-29 sterane distributions are similar. Regarding the sterane abundances, there is a general ranking of C-29 > C-28 > C-27. Iso-, normal-, and dia-sterane abundances of Kagnici and Gokcukur asphaltites are ranked as normal- > iso- > dia-sterane. Iso- sterane contents of the Saraycik asphaltites are significantly greater, and normal sterane abundance is lower than the others. Gokcukur and Kagnici asphaltite samples have similar tricyclic terpane, hopane, and homohopane distributions in m/z 191 mass chromatograms. In m/z 191 mass chromatogram of Saraycik asphaltite sample, tricyclic terpanes were recorded in high abundances, whereas hopanes and homohopanes were recorded in lower abundances. Kagnici and Gokcukrur asphaltites have lower tricyclic terpane and higher hopane distributions. beta beta/(beta beta + alpha alpha) sterane, 22S/(22S + 22R) homohopane, and the low moretane/hopane ratios show that all the asphaltites are mature. (c) 2013 Elsevier Ltd. All rights reserved.