Devolatilization minerals

Land (1987) has reviewed and discussed theories for the formation of saline brines in sedimentary basins. We will summarize his major relevant conclusions here. He points out that theories for deriving most brines from connate seawater, by processes such as shale membrane filtration, or connate evaporitic brines are usually inadequate to explain their composition, volume and distribution, and that most brines must be related, at least in part, to the interaction of subsurface waters with evaporite beds (primarily halite). The commonly observed increase in dissolved solids with depth is probably largely the result of simple "thermo-haline" circulation and density stratification. Also many basins have basal sequences of evaporites in them. Cation concentrations are largely controlled by mineral solubilities, with carbonate and feldspar minerals dominating so that Ca2+ must exceed Mg2+, and Na+ must exceed K+ (Figures 8.8 and 8.9). Land (1987) hypothesizes that in deep basins devolatilization reactions associated with basement metamorphism may also provide an important source of dissolved components. 

A large volume of work has been reported on rapid devolatilization of coal (heating rates approximating process conditions (21,22). Recently, the effects of coal minerals on the rapid pyrolysis of a bituminous coal were reported by Franklin, et al ( 23). They found that only the calcium minerals affected the pyrolysis products. Addition of CaCO3 reduced the tar, hydrocarbon gas and liquid yields by 20-30%. The calcium minerals also altered the oxygen release mechanism from the coal. Franklin, et al. attribute these effects to CaCOj reduction to CaO, which acts as a solid base catalyst for a keto-enol isomerization reaction that produces the observed CO and H2O. 

Della Ventura, G., Bellatreccia, F., Cesare, B., Harley, S. Piccinini, M. (2009). FTIR microspectroscopy and SIMS study of water-poor cordieiite from El Hoyazo, Spain application to mineral and melt devolatilization. Lithos, Vol 113, pp. 498-506 Dimanov, A., Dresen, G., Xiao, X., Wirth, R. (1999). Grain boimdary diffusion creep of synthetic anorthite aggregates the effect of water. Journal of Geophysical Research, Vol. 104, pp. 10483-10497... 

Although the runaway greenhouse is considered the pre-eminent model, it has been subject to useful criticism and suggestions of engineering alternatives. It seems quite possible (perhaps likely) that if Mars s original inventory of CO2 remains on the planet, then it will have ended up for the most part chemically bound in carbonate minerals, rather than physically bound as the more labile CO2 ice or regolith adsorbate. If this is the case, then re-release of this paleoatmosphere will require extremely energetie processes such as devolatilization of carbonate strata... 

Fig. 29. TWin-screw extrusion compounding line for the preparation of mineral-filled thermoplastics showing pre-mixing, compounding and pelletizing stages [155] (a) Filler/poly-mer/additive feedstock, (b) high-speed pre-mixer, (e) dosing screw, (d) twin-screw compounder, (e) vacuum devolatilization, (f) water-cooled die-face cutter, (g) start-up diverter, (h) de-watering chute, (i) pellet dryer, (k) bagging...

---