Changes

[[file:oiloil-and-oilsource-rock-correlations_fig8-38.png|left|300px|thumb|{{figure number|3}}Sterane and triterpane fragmentograms for representatives of the two families. From Grantham;<ref name=ch08r15 /> reprinted with permission from Elsevier.]]

[[file:oiloil-and-oilsource-rock-correlations_fig8-38.png|left|300px|thumb|{{figure number|3}}Sterane and triterpane fragmentograms for representatives of the two families. From Grantham;<ref name=ch08r15 /> reprinted with permission from Elsevier.]]

Two families of oils sourced from Precambrian rocks in Oman have been identified by Grantham.<ref name=ch08r15>Grantham, P., J., 1986, The occurrence of unusual C27 and C29 sterane predominances in two types of Oman crude oil: Organic Geochemistry, vol. 9, p. 1–10., 10., 1016/0146-6380(86)90077-X</ref> [[:file:oiloil-and-oilsource-rock-correlations_fig8-38.png|Figure 3]] shows the sterane and triterpane fragmentograms for representatives of the two families. Triterpane distributions look very different (bottom figures) but in fact differ mostly in the tricyclic/pentacyclic ratio. This ratio is believed to be affected by maturity as well as by source, so this difference alone does not prove the families are different. The steranes, however, are very different. One family is dominated by the C₂₉ regular steranes (top left, peaks E, F, G, H) while the other contains almost exclusively C₂₇ regular steranes (top right, peaks A, B, C).

Two families of oils sourced from Precambrian rocks in Oman have been identified by Grantham.<ref name=ch08r15>Grantham, P. J., 1986, The occurrence of unusual C27 and C29 sterane predominances in two types of Oman crude oil: Organic Geochemistry, vol. 9, p. 1–10., 10., 1016/0146-6380(86)90077-X</ref> [[:file:oiloil-and-oilsource-rock-correlations_fig8-38.png|Figure 3]] shows the sterane and triterpane fragmentograms for representatives of the two families. Triterpane distributions look very different (bottom figures) but in fact differ mostly in the tricyclic/pentacyclic ratio. This ratio is believed to be affected by maturity as well as by source, so this difference alone does not prove the families are different. The steranes, however, are very different. One family is dominated by the C₂₉ regular steranes (top left, peaks E, F, G, H) while the other contains almost exclusively C₂₇ regular steranes (top right, peaks A, B, C).

Gas chromatograms (not shown) reveal the presence of a series of X-compounds in both families, diagnostic of Precambrian sources.

Gas chromatograms (not shown) reveal the presence of a series of X-compounds in both families, diagnostic of Precambrian sources.