Graphite/graphitic rocks as cause of the electric conductivity anomaly and their relationship to the tectonics - A review

From the very beginning of the magnetotelluric (MT) studies two notions have been coupled to each other: the graphite as one of the causes of strong conductivity anomalies and tectonics. The graphitic formations of very low resistivity (< 10-1 ωm) are accumulated in the shear zones, thrust sheets, detachment horizon etc. and by this way they indicate the tectonics/paleotectonics which may not be indicated by other geophysical method so definitely. The author firstly surveys the manifestation of this phenomenon in case histories of the literature, then illustrates it by own very detailed study carried out on the Transdanubian crustaJ conductivity anomaly (TCA). The material of the conductor and their possible relation to the seismicity of the area will also be demonstrated by the TCA anomaly. In the closing chapters the origin of the graphite and its accumulation in the shear zones is discussed including the role of the (geothermal) water. © 2005 Akadémiai Kiadó, Budapest.