Porphyrins diagenesis

In order to demonstrate the relative importance of age and depth of burial on porphyrin diagenesis, the yields of the porphyrins and chlorins were plotted against depth of burial (Figure la) and geologic age (Figure lb) (4,6-16). In Figure la it is noted that as the depth of burial increases (from ocean floor to 1200 m subbottom) there is a systematic increase in... 

These data expose some pertinent new facts concerning porphyrin diagenesis as well as shedding hght on the origin of petroporphyrins which have long been believed to be the products of chlorophyll diagenesis (24,25). Temperature is the promoter of both transalkylation and dealkylation reactions which can occur in deeply buried sediments. However, because of the extreme temperatures (300°-1000°C) to which the sediments in this case were exposed, dealkylation was favored over transalkylation. Under milder conditions (50°-150°C) the transalkylation... 

The distribution of vanadyl vs. nickel porphyrins is noteworthy (Table IV). An overview of the data from Site 368 shows that normal porphyrin diagenesis has progressed to the nickel DPEP porphyrin stage at + 15.87 m (IS). At greater depth, the normal process is interrupted by high thermal stress with concomitant formation of vanadyl porph)u is and decomposition of the native nickel porphyrins. Further below the sill (—8.39 m) only slightly altered nickel porph)rins, again predominantly... 

Porphyrins of the DPEP type, with carbon number ranges of C26—C3g, predominate during diagenesis in... 

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