| Popis: |
An understanding has been established of the geochemistry and distribution of porphyrins, chlorins and polycyclic aromatics in nearly 250 soils, sediments and sedimentary rocks of various ages from early Precambrian to Recent, and of a wide range of depositional environments. Nickel porphyrin, at concentrations up to 9.8 ppm was found preferentially in fine-grained marine clastic rocks. Vanadyl porphyrins, at concentrations up to 39 ppm, are more widely distributed, with a tendency to concentrate in marine strata, despite the fact that their concentration is generally one order of magnitude lower than that of nickel porphyrin. Iron porphyrins were found in 3 per cent of the samples, at concentrations up to 12.5 ppm. Cobalt, copper and zinc porphyrin were not detected. Chlorins occur in 90 per cent of the Recent sediments and soils analyzed, and are believed to be primary in some ancient sediments. They appear to be about equally distributed in ancient marine and non-marine sedimentary rocks. Six types of polycyclic aromatics have been distinguished, based on their spectral characteristics. They occur at concentrations up to 5·6 ppm and show a slight preference to accumulation in non-marine rocks. Normal alkanes and isoprenoids were sought in 42 selected rocks and soils. Odd carbon preference was marked in some rocks, with n-alkanes being found up to 216 ppm and isoprenoids up to 12.9 ppm. It is concluded that traces of much of the biogenic material associated with ancient and modern life processes are preserved in the mass of organic material present in the sedimentary environment. |
