topography and climate are two important soil forming factors affecting genesis and clay mineralogy of soils. calcareous and gypsiferous soils are widely spread in arid and semiarid parts of iran and palygorskite is a dominant clay mineral in these soils. the objectives of the study were to: (1) determine soil genesis and classification along the climotoposequence and (2) investigate clay miner...

-A new chemical mass balance technique has been developed for simultaneous mineralogical quantification and chemical characterization of soil clays. The procedure includes separation of the whole clay (<2 ~tm fraction) into six particle size fractions (<0.02, <0.06, <0.2, 0.02-0.06, 0.06-0.2, and 0.22 um fractions), chemical analysis of the whole clay and each of the six fractions, and fitting ...

Mineral surfaces can support several processes that likely play a role in the origin of life including the concentration, selective sorption[1], protection[2], organization[3-5], and polymerization[6] of organic molecules. Clay minerals are predicted to be present in prebiotic environments and provide a large surface area for reactions with organic molecules. Interactions between early biomolec...

Worldwide increases in fluvial fine sediment are a threat to aquatic animal health. Fluvial fine sediment is always a mixture of particles whose mineralogical composition differs depending on the sediment source and catchment area geology. Nonetheless, whether particle impact in aquatic organisms differs between mineral species remains to be investigated. This study applied an in vitro approach...

Iron-bearing phyllosilicates strongly influence the redox state and mobility of uranium because of their limited hydraulic conductivity, high specific surface area, and redox reactivity. Standard extraction procedures cannot be accurately applied for the determination of clay-Fe(II/III) and U(IV/VI) in clay mineral-U suspensions such that advanced spectroscopic techniques are required. Instead,...

The formation of transition-metal surface precipitates may occur during sorption to clay minerals under ambient soil conditions. This process may lead to significant longterm stabilization of the metal within the soil profile. However, the rates and mechanisms controlling surface precipitate formation are poorly understood. We monitored changes in the reversibility of Ni sorbed to a clay minera...

Estimates of temperatures, past and present, in geothermal reservoirs can be made by using now standard mineralogical techniques, including fluid inclusion geothermometry, vitrinite reflectance, calc-silicate and clay occurrence, the extent of clay interlayering, and measuring clay crystallinity. Recent studies of clays in 60 drillcores from 6 wells at Wairakei, for example, show an inverse rel...

The aim of this review is to examine the hypothesis that organic matter decreases the adsorption of radiocaesium on clay minerals. The factors that determine radiocaesium mobility and bioavailability in soil are briefly outlined to show why a relationship between soil organic matter content and enhanced Cs bioavailability is paradoxical. In all the investigations reviewed the ionic compositions...

The clay montmorillonite is known to catalyze the polymerization of RNA from activated ribonucleotides. Here we report that montmorillonite accelerates the spontaneous conversion of fatty acid micelles into vesicles. Clay particles often become encapsulated in these vesicles, thus providing a pathway for the prebiotic encapsulation of catalytically active surfaces within membrane vesicles. In a...