Generation of electromotive force in igneous rocks subjected to non-uniform loading

(整期优先)网络出版时间:2011-06-16
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Whenoneendofanair-dryigneousrockblockwasuniaxiallyloadedinlaboratory,thereappearedanelectromotiveforcethatmadeelectriccurrentsflowfromthestressedvolumetotheunstressedvolume.Quartz-freerockssuchasgabbroalsogeneratedthisforce,strongerthanquartz-bearingrockssuchasgranite.Thisindicatesthatthepiezoelectriceffectofquartzandtheelectrokineticeffectofporewaterdonotmakealargecontributiontowardgeneratingtheelectromotiveforce.Wefocusonperoxybondthatisoneoftheabundantlatticedefectsinigneousrock-formingminerals.Whenmechanicalloadingdeformsthelatticestructurearoundthisdefectandbreaksitsbond,itsenergylevelschangeandactlikeanaccepter.AsanelectronistrappedatthisdefectfromaneighborO2-site,apositiveholeisactivatedthere.Theyattempttodiffusetowardtheunstressedvolumethroughthevalencebandandaresimultaneouslyaffectedbytheattractiveelectricforcewiththeelectronstrappedinperoxybonds.Thisleadstoapolarizationinthestressedvolumeandthegenerationofelectromotiveforcebetweenthestressedandunstressedvolumes.SimilarelectromotiveforcemaybegeneratedintheEarth’scrustwhereinhomogeneousstress/strainischanging.