HR: 1340h
AN: MR13C-1407    [Abstracts]
TI: Stress Activation and Propagation of Electronic Charge Carriers in Igneous Rocks
AU: * Ling, J
EM: jling@Princeton.edu
AF: Princeton University, Department of Physics, Princeton, NJ 08544, United States
AU: * Ling, J
EM: jling@Princeton.edu
AF: NASA Academy for Space Exploration, NASA Ames Research Center, Moffett Field, CA 94035-1000, United States
AU: Freund, F T
EM: ffreund@mail.arc.nasa.gov
AF: NASA Ames Research Center, Code SGE, MOffett Field, CA 94035-1000, United States
AU: Freund, F T
EM: ffreund@mail.arc.nasa.gov
AF: San Jose State University, Department of Physics, San Jose, CA 95192-0106, United States
AU: Freund, F T
EM: ffreund@mail.arc.nasa.gov
AF: Carl Sagan Center SETI Institute, 515 N Whisman Rd., Mountain View, CA 94043, United States
AB: Igneous and high-grade metamorphic rocks in the Earth's crust generate electric currents when subjected to deviatoric stresses. The reason is that these rocks contain dormant electronic charge carriers in the form of peroxy links. Peroxy links are sites in the crystal structures of the constituent minerals where oxygen anions have converted from their common 2- valence state to the 1- valence state, O3X-OO-XO3 with X=Si4+, Al3+ etc. As rocks are stressed and dislocations sweep through the mineral grains, the peroxy links break up, activating electrons and pholes ("phole" is an abbreviation for "positive hole", a defect electron on the oxygen sublattice, chemically O– in a matrix of O2–). The pholes are mobile electronic charge carriers that can spread out of the stressed rock into the surrounding unstressed rock. They travel via energy levels at the upper edge of the valence bands, cross grain boundaries and achieve a phase velocity on the order of 200±50 m/sec, consistent with phonon-assisted electron hopping. Due to mutual repulsion inside the rock volume the pholes spread to the surface, where they build up a positive surface charge. The surface charge can be measured with a non-contact capacitive sensor. If a Cu contact is applied to the surface of the rock, electrons are injected from ground into the rock in response to the evolving positive charge on the rock surface. We modeled surface potentials and burst-like electron injections following low and medium velocity impact experiments, 100 m/sec and 1.5 km/sec respectively.
DE: 3630 Experimental mineralogy and petrology
DE: 3900 MINERAL PHYSICS
DE: 3904 Defects
DE: 3914 Electrical properties
DE: 5139 Transport properties
SC: Mineral and Rock Physics [MR]
MN: 2007 Fall Meeting