![]() Hexavalent chromium is a water-soluble pollutant, the mobility of which can be controlled by reduction of Cr(VI) to less soluble, environmentally benign Cr(III). Joe-Wong, Claresta Brown, Gordon E Maher, Kate Kinetics and Products of Chromium(VI) Reduction by Iron(II/III)- Bearing Clay Minerals. We thus propose that, within calcite gouge, ultra-low clay content (≤3 wt.%) localized along micrometer-thick layers can facilitate seismic slip propagation during earthquakes in continental domains, possibly enhancing surface displacement. Using friction experiments, we demonstrate that, at seismic slip rates (1 ms -1 ), similar calcite gouges with pre-existing phyllosilicate- bearing ( clay content ≤3 wt.%) micro-layers weaken faster than calcite gouges or mixed calcite-phyllosilicate gouges. We document the occurrence of micrometer-thick phyllosilicate- bearing layers along a carbonate-hosted seismogenic extensional fault in the central Apennines, Italy. Conversely, the reason why, in continental domains, co-seismic slip along faults can propagate up to the Earth's surface is still poorly understood. This evidence is crucial for hazard assessment along oceanic subduction zones, where pelagic clays participate in seismic slip propagation. In particular, rotary shear experiments conducted at seismic slip rates (1 ms -1 ) show that phyllosilicates can facilitate co-seismic slip along faults during earthquakes. Seismic slip propagation is facilitated by along-fault low dynamic frictional resistance, which is controlled by a number of physico-chemical lubrication mechanisms. Many earthquakes propagate up to the Earth's surface producing surface ruptures. Smeraglia, Luca Billi, Andrea Carminati, Eugenio Cavallo, Andrea Di Toro, Giulio Spagnuolo, Elena Zorzi, Federico Ultra-thin clay layers facilitate seismic slip in carbonate faults. The presence of carbonate as well as accompanying clays suggests that waters were neutral to alkaline at the time of its formation and that acidic weathering, proposed to be characteristic of Hesperian Mars, did not destroy these carbonates and thus did not dominate all aqueous environments. The carbonate is closely associated with both phyllosilicate- bearing and olivine-rich rock units and probably formed during the Noachian or early Hesperian era from the alteration of olivine by either hydrothermal fluids or near-surface water. Carbonate-bearing rocks had not previously been detected on Mars' surface, but Mars Reconnaissance Orbiter mapping reveals a regional rock layer with near-infrared spectral characteristics that are consistent with the presence of magnesium carbonate in the Nili Fossae region. Geochemical models for Mars predict carbonate formation during aqueous alteration. Orbital identification of carbonate-bearing rocks on MarsĮhlmann, B.L.
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