Although clay mineral reduction is thought to occur primarily as a result of the activity of indigenous microorganisms in soil, most research has focused on chemical mechanisms of Fe reduction within clay minerals. Here we show that bacteria isolated from soils and sediments catalyze the rapid reduction of structural Fe(III) in the smectite clay minerals. The extent of Fe(III) reduction is larg...

The crystalline swelling of smectites in electrolyte solutions can be controlled by varying the salt concentration of the solutions (Norrish and Quirk 1954, Norrish 1954a, Slade et al 1991). Such osmotic control offers a convenient means of studying the energetics of crystalline swelling. Several X-ray diffraction (XRD) techniques have been developed for measuring the basal spacing of smectites...

In this study, a new genetic interpretation of the Mg-bentonite deposits from Tajo Basin is given through high-resolution transmission electron microscopy study. These bentonites, belonging to Green Clays and Pink lithostratigraphic units, are afforded by sum processes occurring during weathering parent rocks evolution materials transformation phyllosilicates in sedimentary environment. The pri...

The tufts at Yucca Mountain in south-central Nevada are being studied by the Yucca Mountain Project (YMP) to determine their suitability for a high-level radioactive waste repository. For predictive purposes, it Is important to understand the alteration history of Yucca Mountain and to know how the minerals in Yucca Mountain tufts respond to changing conditions such as elevated temperatures. Th...

[1] Jarosite occurs within altered tephra from the saline‐alkaline paleolake deposits of Pliocene‐Pleistocene Olduvai Gorge, Tanzania. Zeolites (mainly phillipsite), authigenic K‐feldspar, and Mg/Fe‐smectites dominate the mineral assemblage, indicating saline‐ alkaline diagenetic conditions (pH > 9). As jarosite is ordinarily an indicator of acidic conditions on Earth and Mars, its association ...

[1] OMEGA/Mars Express has discovered large outcrops rich in phyllosilicates in the region of Mawrth Vallis, Mars (around 20 W, 25 N). The region is located in Noachian highly cratered terrains, close to the limit of the Martian dichotomy, where the outflow channel Mawrth Vallis cuts the highlands. We have examined this region using OMEGA spectra of the surface from 0.9 mm to 2.6 mm, with spati...