Mineral transformation

For many cases one needs to have values of thermodynamic variables for conditions very different from 298 K and 1.0 bar. These cases include reactions occurring above the tropo-pause, where pressures are several orders of magnitude less than 1.0 bar and temperatures are less than 200 K. The important reactions occurring in the high-temperature and high-pressure aqueous conditions of the mid-ocean rift zone, and the high-temperature and high-pressure conditions where important mineral transformations occur far below the Earth s surface are examples. 

Claridge, G. G. C. and Campbell, I. B. (1984). Mineral transformations during weathering of dolerite under cold arid conditions. N.Z. Geol. Geophys. 25, 537-545. 

A heterogeneous natural system such as the subsurface contains a variety of solid surfaces and dissolved constituents that can catalyze transformation reactions of contaminants. In addition to catalytically induced oxidation of synthetic organic pollutants, which are enhanced mainly by the presence of clay minerals, transformation of metals and metalloids occurs with the presence of catalysts such as Mn-oxides and Fe-containing minerals. These species can alter transformation pathways and rates through phase partitioning and acid-base and metal catalysis. 

Blesa, M. (1994) Morphological properties of a-FeOOH, y-FeOOH and Fej04 obtained by oxidation of aqueous Fe(II) solutions. J. Colloid Interface Sd. 165 244-252 Dong, H. Fredrickson, J.K. Kennedy, D.W. Za-chara, J.M. Kukkadapu, R.K. Onstott,T.C. (2000) Mineral transformations associated with the microbial reduction of magnetite. Chem. Geol. 169 299-318 Donnay J.D.H. Marker, D. (1935) A new law... 

As an example of these ideas, an activity-ratio diagram for control of Al(III) solubility by secondary minerals in an acidic soil solution will be constructed. The Jackson-Sherman weathering scenario14 indicates that when soil profiles are leached free of silica with fresh water, 2 1 layer-type clay minerals are replaced by 1 1 layer-type clay minerals, and ultimately these are replaced by metal oxyhydroxides. This sequence of clay mineral transformations can be represented by the successive dissolution reactions of smectite, kaolinite, and gibbsite ... 

Fig. 10.8. Simple biogeochemical model for metal mineral transformations in the mycorhizosphere (the roles of the plant and other microorganisms contributing to the overall process are not shown). (1) Proton-promoted (proton pump, cation-anion antiport, organic anion efflux, dissociation of organic acids) and ligand-promoted (e.g. organic adds) dissolution of metal minerals. (2) Release of anionic (e.g. phosphate) nutrients and metal cations. (3) Nutrient uptake. (4) Intra- and extracellular sequestration of toxic metals biosorption, transport, compartmentation, predpitation etc. (5) Immobilization of metals as oxalates. (6) Binding of soluble metal species to soil constituents, e.g. clay minerals, metal oxides, humic substances.

Fomina, M., Hillier, S., Charnock, J. M. et al. (2005c). Role of oxalic acid overexcretion in toxic metal mineral transformations by Beauveria caledonica. Applied and... 

Sayer, J. A., Cotter-Howells, J. D., Watson, C., Hillier, S. Gadd, G. M. (1999). Lead mineral transformation by fungi. Current Biology, 9, 691. ... 

Precambrian cherty iron sediments. Data on diagenetic processes that went on in ancient rocks which have not retained their original form can be obtained only indirectly, on the basis of a number of assumptions. In any version of the chemogenic hypothesis, the original cherty iron sediment must have been amorphous-dispersed, and the processes of diagenesis were an important step in the formation of the crystalline rock. However, it is quite unclear whether essential mineral transformations occurred, or whether diagenesis was limited to recrystallization of the original sedimentary miner-... 

Rude P. D. and AUer R. C. (1991) Fluorine mobility during early diagenesis of carbonate sediment an indicator of mineral transformations. Geochim. Cosmoehim. Acta 55, 2491-2509. 

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