HR: 1340h
AN: V43B-1584    [Abstracts]
TI: Evidences of spontaneous ion mobility in calcite crystal at standard pressure and temperature.
AU: Zuddas, P
EM: pierpaolo.zuddas@univ-lyon1.fr
AF: PEPS Universite Claude Bernard Lyon1, 43, boulevard du 11 novembre 1918, Villeurbanne, F69622 France
AU: Zuddas, P
EM: pierpaolo.zuddas@univ-lyon1.fr
AF: Centre de recherche IPGP SCHLUMBERGER TOTAL sur le stockage geologique du CO2, 4, place Jussieu, Paris, F75005 France
AU: * Lopez, O
EM: lopez@ipgp.jussieu.fr
AF: Geomateriaux et environnement Institut de Physique du Globe de Paris, 4, place Jussieu, Paris, F75005 France
AU: * Lopez, O
EM: lopez@ipgp.jussieu.fr
AF: Centre de recherche IPGP SCHLUMBERGER TOTAL sur le stockage geologique du CO2, 4, place Jussieu, Paris, F75005 France
AB: Diffusion of element from the bulk to the surface of crystal has been recognized at elevated temperature and pressure but it has been always assumed negligible at standard temperature and pressure. In this work, we present evidences of fast ion transfer (1 - 2 min) originating from inner fluid inclusions, accumulate in crystallites on the surface of calcite. The evolution of (10 1̅4) freshly cleaved surface of a calcite crystal containing fluid inclusions, was observed by an Atomic Force Microscope (AFM) under a mechanical constraint corresponding to the applied force of 10 nN. Continuous in situ images obtained at the nanometre-scale resolution showed fast nucleation and growth of hillocks along the cleavage plan. Germinations occur randomly on the atomically flat surface with an average hillock height of 9 ± 2 Å. After 15 minutes of AFM scanning, the growing of hillock is blocked. By reducing the scan frequency from 12 to 6 Hz, corresponding to the doubling of duration of the mechanical constraint, we observed that the velocity of the hillocks growth increases from 23 to 66 nm³.s^-1. Under this mechanical constraint, we estimated the ion diffusion rate to 10^-10 m.s^-1 independently of the contact time. This phenomenon is interpreted to correspond to the mobility of the ions contained in fluid inclusions from the lattice to the surface. Although the extremely weak pressure of the AFM tip on the calcite, ion diffusion occurs extremely quickly and may contribute to change strongly the surface properties. The observed dynamic surface of calcite has important implications in conceptual models for the behaviour water carbonate mineral interface.
DE: 1022 Composition of the hydrosphere
DE: 1043 Fluid and melt inclusion geochemistry
DE: 1051 Sedimentary geochemistry
DE: 3617 Alteration and weathering processes (1039)
DE: 3947 Surfaces and interfaces
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005