caa a22 4500 46321725X CHVBK 20180405153200.0 cr unu---uuuuu 170326e20070901xx s 000 0 eng 10.1007/s00269-007-0162-x doi (NATIONALLICENCE)springer-10.1007/s00269-007-0162-x In situ impedance spectroscopy on pyrophyllite and CaCO3 at high pressure and temperature: phase transformations and kinetics of atomistic transport [Elektronische Daten] [J. Ter Heege, J. Renner] In situ impedance spectroscopy in laboratory experiments at high pressure and temperature can provide crucial quantitative information on properties of rock materials at depth as well as on physical and chemical processes occurring in the deep Earth. We developed an experimental setup for in situ electrical impedance measurements in a piston-cylinder apparatus and applied it to study the kinetics of charge carriers and phase transformations in pyrophyllite and CaCO3 aggregates. From comparison with previous studies, we found that absolute values of electrical conductivity and pressure-temperature conditions for dehydration reactions in pyrophyllite and phase transformations in CaCO3 can be accurately determined using our setup. Dehydration of pyrophyllite significantly enhances the transport kinetics and the effect is more pronounced under undrained conditions than under drained conditions. When dehydroxylation and decomposition temperatures for pyrophyllite under undrained and drained conditions are combined, they appear independent of pressure rather than increasing with pressure as previously suggested. Electrical conductivity of CaCO3 varies with impurity content and grain size, and is most likely controlled by diffusion of oxygen along wet grain boundaries. When applied to the Earth, the results on pyrophyllite suggest that the increase in electrical conductivity in rocks that undergo dehydration should be taken into account in interpreting magnetotelluric surveys of regions with anomalously high conductivity found above subducting plates. The results on CaCO3 indicate that grain boundary transport controls the electrical conductivity in fine-grained calcite rocks; hence calcite mylonites may be detected using magnetotelluric methods. Order-disorder transformations, such as occurring in calcite, possibly affect the physical properties of rocks (e.g., rheology) by changing the kinetics of atomistic transport processes. Springer-Verlag, 2007 Impedance spectroscopy nationallicence High pressure nationallicence Pyrophyllite nationallicence Calcite-aragonite nationallicence Ter Heege J. Institute for Geology, Mineralogy and Geophysics, Ruhr-University Bochum, 44780, Bochum, Germany aut Renner J. Institute for Geology, Mineralogy and Geophysics, Ruhr-University Bochum, 44780, Bochum, Germany aut Physics and Chemistry of Minerals Springer-Verlag 34/7(2007-09-01), 445-465 0342-1791 34:7<445 2007 34 269 https://doi.org/10.1007/s00269-007-0162-x text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s00269-007-0162-x text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Ter Heege J. Institute for Geology, Mineralogy and Geophysics, Ruhr-University Bochum, 44780, Bochum, Germany aut NATIONALLICENCE 700 1- Renner J. Institute for Geology, Mineralogy and Geophysics, Ruhr-University Bochum, 44780, Bochum, Germany aut NATIONALLICENCE 773 0- Physics and Chemistry of Minerals Springer-Verlag 34/7(2007-09-01), 445-465 0342-1791 34:7<445 2007 34 269 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer