Diffusive transport of water in porous fresh to altered mid-ocean ridge basalts

Differential alteration of basaltic lava flows and hyaloclastites in Icelandic hydrothermal systems

“…But, if the precipitation kinetics of secondary minerals is fast enough to consider a water/rock ratio of 0.4 (i.e., the threshold water/rock ratio calculated in this section) or less, the alteration is blocked because of mineral volume changes or severely decreased if the diffusion can continue through the secondary minerals. An increase of effective diffusion coefficient of water molecules in fresh basalt from 5.05°10 −11 to 1.19°10 −10 m 2 /s was measured as temperature increases from 5 to 50°C, implying an activation energy of 12.3 kJ/mol (Simonyan et al 2012). By using Equation 6, it can be calculated that in 10,000 years, the diffusion front would propagate 6 m at 50°C, and 15 m at 250°C.…”

“…We have no clear idea about the thickness of the alteration zone around the fractures; neither if there is a sharp boundary or a progressive transition, but such a diffusion length is in contradiction with the fact that lava flows are rather fresh. In addition, it is worth to note that the age of the fresh mid-ocean ridge basalt mentioned above was estimated at 8.64 Ma (Simonyan et al 2012). The authors did not provide any information about the temperature, but it is likely that some hydrothermal circulation occurred in such systems.…”

“…By considering a range of possible specific surface areas from 0.4 to 2.3 m 2 /g for a fresh basalt (Simonyan et al 2012) and a perfectly cylindrical shape for pores and fractures, it can be simply calculated that the water/rock ratio of 0.4 corresponds to a pore or fracture diameter range between 0.2 and 1.3 μm, completely filled by water. This is greater than the average pore diameter of 45 nm measured in a fresh basalt (Simonyan et al 2012). Consequently, the pores in basalt can be potentially clogged, as well as the sub-micrometric aperture fractures.…”

Mineralogy and pore space characteristics of traprocks from Central Siberia, Russia: Prerequisite of weathering trends and soil formation

“…Rock disintegration in the soil environment leads to an increase in the proportion of pores with a radius in the range of 50-1000 nm, as identified in the BC horizon rather than in BR, Pit E-5/8. A correlation between secondary minerals and pore sizes less than 10 nm, whose maximum was also observed in the studied rock fragments, has been reported for rock samples of altered mid-ocean ridge basalts (Simonyan et al, 2012). The development of these pores is apparently connected with the zones of the formation of secondary products of dolerite weathering.…”

Application of Rock Weathering and Colonization by Biota for the Relative Dating of Moraines from the Arid Part of the Russian Altai Mountains

“…The intensity of chemical weathering is limited by the moisture availability [52] and depends on rock microstructural properties [53]. Rock weathering is also correlated with the pore size distribution [54] and rock fractality [55]. The use of weathering rates from rinds on several rock types for relative to absolute age dating of Quaternary deposits has been discussed [56][57][58][59][60].…”