A bentonite bed in the Aceguá (RS, Brazil) and Melo (Uruguay) areas: a highly crystallized montmorillonite

A dual-layer Chicxulub ejecta sequence with shocked carbonates from the Cretaceous–Paleogene (K–Pg) boundary, Demerara Rise, western Atlantic

“…The smectite 00l peaks have a very high intensity and a very low FWHM (full width at half maximum) value of only $0.6°to 0.8°2H for the smectite 001 reflection. In concert, these mineralogical data imply excellent smectite crystallinity, suggesting that a large part of this smectite formed in situ by alteration of glassy ejecta material (e.g., Ortega-Huertas et al, 2002;Calarge et al, 2003). Further constraints on the mineralogy of the spherule deposit are provided by temperature (T)-dependent magnetic susceptibility (j) measurements (j-T curves), allowing detection of even very low amounts of ferromagnetic phases.…”

Stability of lanthanum-saturated montmorillonite under high pressure and high temperature conditions

“…The structural formula of the montmorillonite used in this work was determined by Calarge et al (2003) from a bulk bentonite and is given by: …”

Structural changes of potassium-saturated smectite at high pressures and high temperatures: Application for subduction zones

“…This method involves the direct measurement of the distribution of fractions as a function of time for these particles, decanted in a vertical cell (beaker) with a convenient liquid (distilled water). The chemical formula of the studied smectite was approximately calculated by Calarge et al (2003) using ICP-MS analyses: [Si 3,87 Al 0,13 ] O 10 (Al 1,43 Fe 3+ 0,08 Mg 0,53 Ti 0,01 ) (OH) 2 K + 0,01 Ca 2+ 0,23 . Following the separation of the b2 μm fraction, a KCl (1 mol/L) solution was added to replace calcium by potassium in the structure of the smectite.…”