Table 1. Alkanes in fresh surface asphalts.
a, Concentrations of low-molecular-weight alkanes [in µmol L-1 bulk asphalt] and resulting C1/(C2-C5) ratios in gas samples prepared from an asphalt/gas hydrate piece from one of the Chapopote invertebrate collection sites (GeoB19325-9). b, The relative composition of light hydrocarbons [in mol% Σ(C1-C6)] and resulting C1/(C2-C6) ratios in gas (Chapopote) and oil (Mictlan) bubbles above invertebrate collection sites (see Fig. 1).
| a) | |||||||||
|---|---|---|---|---|---|---|---|---|---|
| Sample location on asphalt / hydrate piece | C2 | C3 | i-C4 | n-C4 | n-C5 | C1/(C2-C5) | C1/C2 | C1/C3 | |
| outside of microbial mat | 1,026.5 | 8.8 | n.d. | 9.7 | 4.4 | 20.5 | 20.9 | 2440.1 | |
| inside microbial mat | 396.9 | 67.9 | 23.2 | 73.9 | 28.6 | 8.9 | 13.2 | 77.2 | |
| below microbial mat | 839.4 | 376.7 | 57.1 | 411.6 | 128.7 | 4.7 | 10.2 | 22.8 | |
| b) | |||||||||
| Collection site | Station no. GeoB | C1 | C2 | C3 | i-C4 | n-C4 | Σ C5-isomers | Σ C6-isomers | C1/(C2-C6) |
| Chapopote | 19325-13 | 97.6 | 1.5 | 0.4 | 0.1 | 0.2 | 0.1 | 0.1 | 41.4 |
| Mictlan | 19336-5 | 64.1 | 16.0 | 14.5 | 0.1 | 3.0 | 1.2 | 0.4 | 1.8 |