Montmorillonite under high H 2 O pressures; stability of hydrate phases, rehydration hysteresis, and the effect of interlayer cations

Other| February 01, 1997 Montmorillonite under high H2O pressures: Stability of hydrate phases, rehydration hysteresis, and the effect of interlayer cations Tzy-Chung Wu; Tzy-Chung Wu Cornell University, Department of Geological Sciences, Ithaca, NY, United States Search for other works by this author on: GSW Google Scholar William A. Bassett; William A. Bassett Search for other works by this author on: GSW Google Scholar Wuu-Liang Huang; Wuu-Liang Huang Search for other works by this author on: GSW Google Scholar Stephen Guggenheim; Stephen Guggenheim Search for other works by this author on: GSW Google Scholar August F. Koster van Groos August F. Koster van Groos Search for other works by this author on: GSW Google Scholar American Mineralogist (1997) 82 (1-2): 69–78. https://doi.org/10.2138/am-1997-1-209 Article history first online: 02 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Twitter LinkedIn Tools Icon Tools Get Permissions Search Site Citation Tzy-Chung Wu, William A. Bassett, Wuu-Liang Huang, Stephen Guggenheim, August F. Koster van Groos; Montmorillonite under high H2O pressures: Stability of hydrate phases, rehydration hysteresis, and the effect of interlayer cations. American Mineralogist 1997;; 82 (1-2): 69–78. doi: https://doi.org/10.2138/am-1997-1-209 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu nav search search input Search input auto suggest search filter All ContentBy SocietyAmerican Mineralogist Search Advanced Search Abstract Dehydration of Ca- and Mg-exchanged montmorillonite was studied along H2O isochores in the hydrothermal diamond-anvil cell by in situ X-ray diffraction using a synchrotron radiation source. At pressures between the H2O liquid-vapor (L-V) boundary and ~ 10 kbar, the dehydration temperature for the conversion from the 19 Å hydration state to the 15 Å hydration state occurred over the temperature range 260–350 °C for Ca-ex-changed montmorillonite and 200–250 °C for Mg-exchanged montmorillonite, with a slight increase with increasing pressure. For both materials, the rehydration from the 15 Å to 19 Å states occurred at the same temperature as dehydration at pressures along the H2O L-V boundary, thus showing no hysteresis. The rehydration hysteresis increased to nearly 75 °C at 6 kbar for Ca-exchanged montmorillonite and to the same amount at 2.5 kbar for Mg-exchanged montmorillonite. Dehydration experiments on Mg-exchanged montmorillonite along the isochores of 1.024 and 0.75 g/cm3 showed conversion from the 15 Å hydrate to the 12.5 Å hydrate at 590–605 °C. The 12.5 Å hydrate only partially rehydrated after cooling to room temperature along those two isochores. In an experiment started from the 15 Å state, in which the pressure was below the H2O L-V curve, dehydration occurred at 400–500 °C and rehydration at 430–350 °C. When our previous results on Na-exchanged montmorillonite are combined with the current experimental data, systematic trends can be found in the effect of pressure and interlayer-cation species on the dehydration temperature and rehydration hysteresis. This content is PDF only. Please click on the PDF icon to access. First Page Preview Close Modal You do not currently have access to this article.