Mineral dissolution rates

Table 8.26 pH dependence of mineral dissolution rates (after Lasaga, 1984 with integrations). 

Mineral Dissolution rate k Activation energy eJ Frequency factor A ... 

Experimental investigations will continue to play a critical role in understanding heterogeneous reaction kinetics, such as mineral dissolution rates in silicate melts and in aqueous solutions, the melting rates at the interfaces of two... 

Walter L.M. and Burton E.A. (1986) The effect of orthophosphate on carbonate mineral dissolution rates in seawater. Chem. Geol. 56, 313-323. 

An important factor in controlling mineral dissolution rates are the steps which involve the hydrolysis of cations at the mineral surface and their subsequent removal into the solvent (20, and references therein). 

Ayres M., Harris N., and Vance D. (1997) Possible constraints on anatectic melt residence times from accessory mineral dissolution rates an example from the Himalayan leuco-granites. Min. Mag. 61, 29-36. 

Casey W. H. and Sposito G. (1992) On the temperature dependence of mineral dissolution rates. Geochim. Cosmochim. Acta 56, 3825-3830. 

Swoboda-Colberg N. G. and Drever J. I. (1993) Mineral dissolution rates in plot-scale field and laboratory experiments. Chem. Geol. 105(1-3), 51—69. 

Seimbille F., Zuddas P., and Michard G. (1998) Granite-hydrothermal interaction a simultaneous estimation of the mineral dissolution rate based on the isotopic doping technique. Earth Planet. Set Lett. 157, 183-191. 

Leak-off or loss of acid through the walls of worm holes often results in worm holes being too short to provide significant productivity increase. Therefore, effective stimulation often requires retardation of the mineral dissolution rate. The use of microemulsions is one method to accomplish this retardation. The hydrochloric acid is injected as an water-in-oil microemulsion. The diffusion rate of the dispersed aqueous acid to the rock surface is slower than molecular diffusion of acid from a totally aqueous system. Thus the rate of limestone dissolution is retarded with the microemulsion system. 

The rate of chemical weathering has been evaluated using historic, mass-balance, and theoretical-empirical mineral dissolution rate approaches, often with different results. What are these approaches and why may their results differ ... 

SwoBODA-CoLBERG, N, G., and J. I. Drhvhr. 1992. Mineral dissolution rates A comparison of laboratory and Held studies. Proc. 7th inti, syinp. water-mck interaction, ed J. Kharaka and A. Maest, pp. 115-18. Rotterdam A. A. Balkema. 

This principle relating mineral dissolution rates also extends to secondary minerals such as oxides. The Cr " ion, if substituted for Fe in FeOOH, inhibits dissolution of the oxide, presumably because is a ion with high CFSE, while Fe " " is a ion with zero CFSE. 

Similar principles regarding the effect of weathering product removal apply to primary mineral dissolution rates as well. In this case, however, the weathering reaction is unlikely to be reversible under the temperature and pressure conditions pre-vaiUng in soil environments, as will be demonstrated in the next section. 

Small differences in mineral/water ratios in the reservoir can result in large differences in carbonate mineral dissolution rates. 

Figure 1. Linear rates (in millimeters per year) of chemical kinetic and macroscopic transport processes in surficial aquatic and sedimentary environments. Individual processes are coupled to the driving forces, identified as three main groups of chemical (C), hydrological (H), and physical (P) driving forces. Data sources mineral dissolution rates, Tables 4 and 5, and Berthelin (1988) mineral dehydration, compilation in Bodek and Lerman (1988) metal corrosion, Coburn (1968), Costa (1982), and Haynie and Upham(1970) uplift, Lajoie(1986), Stallard (1988) physical erosion, Table 3 chemical weathering, soil formation and chemical denudation, Table 6.

MINERAL DISSOLUTION AND CHEMICAL WEATHERING 6.1. Mineral Dissolution Rates... 

It was pointed out in the preceding section that a lack of agreement between the mineral dissolution rates, as reported from laboratory experiments, and the chemical weathering rates, as derived from the composition and volumes of surficiai runoff, suggest a number of bracketing values that can be placed on the parameters in the models for chemical weathering and transport. 

A net rate of weathering may also be defined in terms of mineral dissolution rates (K), when dissolution occurs within a porous layer of some thickness, and the dissolution products are transported by water flowlin the pore space and further out to the surficial runoff (Fig. 6). In this formulation, the net weathering rate W is... 

Figure 6. Dissolution and transport in the weathering zone (W is net weathering rate) C is concentration in discharge, Q is volume discharge, A is land surface area, h is thickness of reactive zone, is its porosity, and t is water residence time within the reactive zone space, where S is the reactive surface area of minerals. For a weathering rate consisting of contributions from individual minerals, R, is mineral dissolution rate, Sgi is mineral surface area per gram, and pt is mineral density. Depth of the reactive zone and volume of water in pore space (f> may be functions of the water discharge volume /ib/), v(r/).

The magnitudes of chemical kinetic and macroscopic transport processes, evaluated as their linear rates [linear rate=(mass flux)/(concentration or density) = F/p], indicate that great differences exist between the mineral dissolution rates, as reported from laboratory measurements, and the rates derived from river-water composition and volume flow. These differences point to an important role of the physical structure of the weathering zone and water residence time within it that control mineral dissolution fluxes and transport of the reaction products. An additional factor responsible for the faster rates of chemical weathering could be bacterial, activity which may be expected to vary from lower levels in the cold regions to the higher levels in the tropics, in parallel with the rates of net primary productivity. 

Cation and anion adsorption by hydrous metal oxides influence several processes of environmental concern including contaminant transport, nutrient availability, and mineral dissolution rates (i,2). Various factors influence the amount of a particular ion adsorbed including solution pH, type of oxide and its surface area and crystallinity, time, ionic strength, properties and concentration of the adsorbing species, and competing species. These factors have received various degrees of scrutiny in previous studies. Temperature is another potentially important variable but has not to date received as much... 

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