Diagenesis problems

Price, T.D., Blitz, X, Burton, J. and Ezzo, J.A. 1992 Diagenesis in prehistoric bone Problems and solutions. Journal of Archaeological Science 19 513-529. 

Price, T.D. 1989 Multi-element studies of diagenesis in prehistoric bone. In Price, T.D., ed.. The Chemistry of Prehistoric Human Bone. Cambridge, Cambridge University Press 126-154. Price, T.D., Biltz, J., Burton, J.H. and Ezzo, J. 1992 Diagenesis in prehistoric bone problems and iohMiom. Journal of Archaeological Science 19 513-529. 

I shall apply the new method of solution to a problem of early diagenesis in carbonate sediments. I calculate the properties of the pore fluid in the sediment as a function of depth and time. The different reservoirs are... 

Ewers WE (1983) Chemical factors in the deposition and diagenesis of banded iron-formation. In Iron Formations Facts and Problems. Trendall AF, Morris RC (eds) Elsevier, Amsterdam, p 491-512 Fantle MS, DePaolo DJ (2002) The isotopic composition of continental iron and implications for the global Fe cycle. EOS Trans Am Geophys Union 83 V22B-1234... 

The biofilm concept, applied to sediment-water interactions, breaks with classical strategies to model early diagenesis (i.e., the vertical redox zonation). Although far from completely developed, this concept may overcome modeling problems, such as an adequate description of recycling of substances. 

An inherent problem with chemical characterization of bones is that diagenesis may confound the results of the analysis. One possible way to avoid diagenesis and contamination is through the use of a microprobe to sample specific areas of the bone. LA-ICP-MS may prove to be ideally suited for this... 

The rate at which metastable phases dissolve or are replaced is an important problem in carbonate diagenesis. Carbonate mineral assemblages persist metastably in environments where they should have altered to stable assemblages. The question is "what are the time scales of these alterations" They are certainly variable ranging from a few thousand to a few hundreds of millions of years. Even calcites in very old limestones show chemical and structural heterogeneities, indicating that the stabilization of these phases is not complete. Unfortunately, it is difficult, but not impossible, to apply directly the lessons learned about carbonate mineral dissolution and precipitation in the laboratory to natural environments. 

The timing of the dolomitization of carbonate rock bodies and emplacement of dolomite cements has been one of the more controversial aspects of the "dolomite problem." Most of the basic factors controlling dolomite formation, where were discussed in Chapters 6 and 7, also apply to dolomite formation during the later stages of diagenesis. However, the extended periods of time, the solution compositions likely to be encountered, and the elevated temperature and pressure that occur during deep burial provide highly favorable conditions for dolomite formation. 

In the diffusion model presented here, the value of the diffusion constant D remains constant, which is not the case for natural bone systems. The problems arising from bone diagenesis will be discussed in Section 3.2.7 and by Reiche in this compendium. 

As a result, a physicochemical model for the formation of the BIF is proposed which is consistent with modern ideas on the evolution of sedimentation and volcanism and of the atmosphere, hydrosphere, and biosphere in the Precambrian. This model, which proposes a mainly volcanic source for the iron and silica and a biochemical and chemical mechanism of deposition, is the most likely but not the only possible one. Other versions, or different interpretations, are not ruled out, but it is perfectly obvious that in any genetic postulates, the specific physicochemical data must be taken into account. It is also quite understandable that in a work which is a first attempt at physicochemical analysis of the entire geological cycle— source of the material transport deposition diagenesis metamorphism—not all the problems have been worked out in sufficient detail and not all the evidence is conclusive far from it. Further investigations in this direction are needed, including not only determination of the role of the individual parameters in ore formation, but also direct experimental modeling of the process. 

Because aragonite is more susceptible to dissolution than calcite, especially under the influence of meteoric waters, and because most fossil corals are recovered from uplifted terrestrial deposits, diagenesis is an especially important limiting factor in recovering older coral records. This problem can be circumvented by drilling into submerged fossil deposits, but because of logistical difficulties, so far this has been accomplished in only a few key spots such as Barbados and Tahiti (Eairbanks, 1989 Bard et al., 1996). 

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