Plant-controlled supratidal anhydrite from Al-Khiran, Kuwait
We report here that in the supratidal zone of the Al-Khiran sabkha, diagenetic anhydrite occurs exclusively in association with the living halophyte Halocnemum strobilaceum (Pallas) M .B. This anhydrite has a hair cream-like consistency and the bulk of it has formed as pseudomorphs after gypsum crystals. On the death of the plant at the end of its life cycle, the anhydrite is hydrated back to gypsum. This two-way transformation results in a series of characteristic textures, whose preservation could be due to the comparative ‘youth’ of the sabkha, which is in the very earliest stages of evaporite diagenesis.
Hydro-behaviour of Middle Eastern desert soils
Abstract Surface settlement in desert areas occurs in response to fluctuating groundwater levels. Model experiments have indicated a minor settlement as a result of rise and fall of water level and this is attributed to the readjustment of soil particles to a better packing condition as a result of suction forces. Deposition of salts within the pore spaces has been found to result in swelling of 0.5–1% in medium-dense model samples, whereas dense samples showed a swelling of 4–8%. The method of drying affected the results; oven drying gave greater swelling than drying by a hot air current. The type of precipitated salt was found to control the degree of swelling; calcium sulphate results in greater swelling than that caused by calcium carbonate, and the latter exceeds that induced by sodium chloride. The results of tests indicate that changing groundwater levels can cause surface settlement and/or heave related to the associated processes of salt precipitation and/or dissolution.
Thermal stability of some metal sulphates
Abstract The thermal decomposition of eleven (II) sulphates has been studied by a combination of thermogravimetric and differential thermal analysis. The relative decomposition temperatures are: MnSO 4 755, FeSO 4 537, CoSO 4 708, NiSO 4 675, CuSO 4 598, ZnSO 4 646, CdSO 4 816, PbSO 4 803, MgSO 4 895, CaSO 4 1149, and SrSO 4 1374°C. Factors possibly influencing thermal stability of such salts are discussed, with special consideration of the effects of the metal's electronegativity and polarizing power on the condition of the anion.